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End Use Operations and Maintenance

2006;():1-8. doi:10.1115/ICES2006-1301.

This paper presents results from a study intended to generate engine operating profiles and exhaust temperature characteristics for the fleet of five ferries operated by the Texas Department of Transportation (TxDOT) between Galveston and Port Bolivar, Texas. Data logging of the TxDOT Galveston ferries was an important first step in assessing NOx reduction technologies. Based on the data logging, the following conclusions are drawn; While EMD and DDC engine exhaust temperatures monitored during in-use operations were below 260°C for a majority of the time, more than 70 percent of the EMD engine NOx emissions occurred at exhaust temperatures greater than 260°C during in-use operations. This is based on in-situ emissions data from an EMD engine of a ferry (Greer) in which emissions measurements were performed; the EMD 12-645-E6 propulsion engines operated well below their 1,120 kW rating; Actual in-use engine operating conditions of the EMD 12-645-E6 engines are not well represented by EPA E2 and E3 marine certification test cycles; EPA engine certification data may not be directly applicable for estimating in-use emissions; Emissions testing at two additional test points during EPA certification testing would capture TxDOT ferry actual operating modes.

Topics: Engines
Commentary by Dr. Valentin Fuster
2006;():9-13. doi:10.1115/ICES2006-1309.

The 1,500 kW EMD 16-645E engine is popular in switcher and shunter locomotive applications for railroads in North America. These locomotives are typically lightly loaded with extended periods of idle operation, and usually operate in large urban areas. With the advent of EPA emissions standards, and increasing fuel costs, many in the railroad industry are looking at replacing these locomotives with hybrid locomotives, installing APU systems or automatic start stops systems, repowering with newer engines, or using new technology to reduce emissions and improve fuel consumption. This paper documents results of research into ways to improve idle and low power emissions and fuel consumption from these roots-blown two-cycle EMD 645E engines. Specifically, this research looked at disabling one bank of injectors to simulate skip fire operation, and the stopping the rotation of one of the two roots-type blowers used to supply boost air to the uni-flow, two-cycle, diesel engine. The results of this work demonstrated that the EMD 16-645E engine did not respond positively when the injectors of one cylinder bank were disabled (simulating bank to bank skip fire operation). However, the engine did demonstrate both a reduction of NOx emissions and brake specific fuel consumption, over the US-EPA switcher and line haul emissions cycles, while operating on only one of the two blowers at idle and light loads. Additionally this concept of blower cut-out allows for reduced mass flow and higher exhaust temperatures at light loads, which could be beneficial for future application of exhaust aftertreatment. However, there is an associated increase in particulate matter emissions.

Topics: Engines , Ejectors , Emissions
Commentary by Dr. Valentin Fuster
2006;():15-23. doi:10.1115/ICES2006-1362.

A DCL oxidation catalyst for exhaust-gas cleaning has been field tested on a Wärtsilä 50 series dual-fuel engine during 5000 hours of continuous operation in an end-user power plant application. The engine has been designed for continuous operation on natural gas (NG), light fuel oil (LFO) as well as heavy fuel oil (HFO), thus giving the consumer a wide variety of fuelling options. All three fuels were used at some point during the 5000 hours field trial. These fuels have different properties such as differing levels of sulphur and ash contents that affect the abatement efficiencies of the oxidation catalyst. A detailed study was performed to understand the effect of different fuels, lube oil poisoning and long running hours on the abatement performance of the oxidation catalyst. The oxidation catalyst was equipped with sample cores that were exchanged during scheduled engine maintenance periods. This allowed parallel field and laboratory evaluation of the emissions abatement and the quantity of lube oil deposits on the catalyst at successive intervals of engine running hours. We will show that the combination of the dual fuel engine and the oxidation catalyst is very robust, even for the different fuels, and it gives low emissions.

Commentary by Dr. Valentin Fuster
2006;():25-34. doi:10.1115/ICES2006-1441.

From 2006 to 2008 depending on the power ratings, Deutz has to update its complete engine product portfolio of compact engines to meet the emission legislation U.S. EPA Tier 3 and EU COM 3A for applications of mobile nonroad machinery. This challenge covers air cooled, oil cooled and as well water cooled engines up to 500 kW. To provide the best solution for the customer with respect to engine price, fuel consumption, power rating and torque characteristics. Deutz will introduce a technology concept called DEVERT® — Deutz Variable Emissions Reduction Technology. In the wide range of industrial applications of construction machinery, agriculture, material handling, and others DEVERT® provides an optimised solution for every case. The technology approach of DEVERT® consists of injection systems like the mechanical unit pump system and the Deutz Common Rail (DCR® ), 2 and 4 valve cylinder-heads, different solutions for internal and external exhaust gas recirculation, and also variable valve actuation. The focus of this paper is on the water-cooled, in-line engine families 2012 and 2013 with a displacement of 4 to 7 l. Based on the application of DEVERT® to these engine families the different technologies are explained by their functionality and their impact on emissions and performance. A short outlook of the emission legislation on future technologies is given. Here exhaust after-treatment will have a significant impact on the engine package with new challenges for the variety of applications.

Topics: Engines , Roads , Emissions
Commentary by Dr. Valentin Fuster
2006;():35-42. doi:10.1115/ICES2006-1443.

Diesel generator sets are installed at nuclear power plants to provide emergency power to ensure safe shut down of the reactor in the event of an accident. In the United States, all nuclear power plants belong to one of six different Diesel Generator Owner’s Groups. Some groups have been in existence for over 17 years and the members have all benefited from their participation. In the past three years, the Diesel Generator Owner’s Group concept has spread and two new groups have been formed among a number of independent diesel generator power plant owners and operators in Latin America and the Caribbean area. This paper describes: (1) how electric power plants, large and small, have formed Diesel Generator Owner’s Groups, (2) how better working relationships between the power plants and the engine manufacturer have been established, and (3) how involvement in a strong owner’s group provides significant benefits to the members. The primary goal of the groups is to increase reliability and improve performance of the diesel engines at the respective power plants. Typical objectives of effective Diesel Generator Owner’s Groups include: • Provide a mechanism for rapid resolution of specific problems with the diesel engine, generator and auxiliary systems, • Provide improved communications among the owners and the diesel generator manufacturer, • Develop a group of “technical experts” and expand that knowledge base to other plant personnel, and • Identify methods to improve diesel engine generator and overall power plant performance, reliability, availability and safety. Active participation in Diesel Generator Owner’s Group has resulted in real payback for the owners and manufacturers alike. To illustrate this fact, several unique diesel engine problems are described along with the approach the Diesel Generator Owner’s Groups used to resolve the problems. Finally, overall diesel generator reliability and availability have improved. These groups have worked to develop the best possible technical environment to continue improving diesel generator power plant performance, operation and maintenance.

Commentary by Dr. Valentin Fuster

Advancements in Engine and Emissions Technology

2006;():43-52. doi:10.1115/ICES2006-1318.

This paper presents an investigation into the potential efficiency and performance improvements in an internal combustion engine by changing the mass and stiffness of valve train components, specifically the mass of the valve and the stiffness of the valve spring. Changes in valve mass affect the dynamic response of the valve train, so changes in other components must be made to maintain reliable and efficient engine operation. In order to quantify the potential benefits of lightweight engine valves, a dynamic model of the complete valve train system was developed. This model was experimentally validated on a motored engine in which the valve motion was measured for different combinations of valve mass, spring stiffness and engine speed. This paper describes the development and validation of the dynamic model, and discusses the effects of varying the valve mass and valve spring stiffness. It was found that a 75% reduction in the mass of the valves (as expected through the use of fiber reinforced composites) could reduce the maximum camshaft drive torque and frictional power by about 60–70%.

Commentary by Dr. Valentin Fuster
2006;():53-64. doi:10.1115/ICES2006-1324.

Unfortunately, the most turbocharger models included in a whole engine simulation rely typically on the direct use of the manufacturers’ maps and on the assumption of adiabaticity of the compressor and the turbine. However, experiments on a turbocharger test bench show that, contrary to general opinions, the heat transfers can influence the turbocharger performances. It seems essential to determine and correlate the different heat transfers occurring in a turbocharger. Furthermore one method is proposed to obtain compressor and turbine isentropic efficiencies, actual mechanical powers and outlet temperatures starting from the manufacturers’ performance maps. This method coupled with the heat transfers correlations obtained experimentally give results in relative good agreement with experimental measures in comparison to their easiness of use.

Topics: Heat transfer
Commentary by Dr. Valentin Fuster
2006;():65-73. doi:10.1115/ICES2006-1332.

Emissions regulations for off-highway engines are tightening towards those of on-highway engines. Present designs will not be able to meet these more stringent regulations because of their use of mechanical fuel injection timing control; more advanced timing control will be required. Ion sensing combined with variable fuel injection timing may help these engines meet the emissions requirements without the drastic price increase that usually accompanies a switch to advanced fuel injection technology. Ion sensing can detect the start of combustion and this signal can be used for closed loop control for the injection timing. The integrity of the ion signal is highly dependent on combustion chamber geometry, sensor placement, and even the polarity of the charge across the sensor. Optimizing all of these effects could improve the detection of the start of combustion from an ion sensor to less than one crank angle degree and provide a signal for closed loop control of the injection timing.

Commentary by Dr. Valentin Fuster
2006;():75-86. doi:10.1115/ICES2006-1336.

The reduction of green-house gas emissions, that is the reduction of engine fuel consumption, is becoming a primary requirement for the automotive industry as well as meeting current and future emission legislations. Performing high torque values with small displacement engines, the so-called “downsizing”, permits, in general, to limit some typical engine losses (for instance: pumping and friction losses), increasing the overall engine efficiency. This means to improve vehicle fuel economy and, as a consequence, the CO2 emissions avoiding a performance decrease. In this paper, the behavior of a small displacement turbocharged spark-ignition engine prototype, for medium size passenger cars, has been analyzed. 3-D numerical simulations have been carried out in order to achieve a lot of information on engine performance and control parameters. Thus, at different engine operating points, intake and exhaust manifold pressure, volumetric efficiency, high pressure curves, the flow field of the fresh charge within the cylinder, the air to fuel ratio distribution, the residual gas fraction distribution and so long have been calculated. Since, as usual, the turbocharged version of the engine under study derives from an existing naturally aspirated engine, the purpose of this investigation is to obtain a detailed picture of the variations produced by turbo-charging on engine main parameters. The increase of knock risk due to higher cylinder pressures has been evaluated as well. Thanks to the three dimensional analysis, sound information have been obtained, so that suggestions for modifying some geometric engine parameters, according to the variations imposed by turbo-charging, have been proposed. Computations have been performed by means of the 3-D AVL Fire code. Initial and boundary conditions have been evaluated by means of 1-D, unsteady computations running separately from the 3-D code. The model utilized in this study has been validated by comparing the obtained results to the measured data provided by the research center of the engine manufacturer.

Commentary by Dr. Valentin Fuster
2006;():87-92. doi:10.1115/ICES2006-1341.

This paper presents the static pressure development and the effect of struts on the performance of an annular diffuser. A typical exhaust diffuser of an industrial gas turbine is annular with structural members, called struts, which extend radially from the inner to the outer annulus wall. An annular diffuser model, primarily intended for fundamental research, has been tested on a wind tunnel. Similar conditions that prevail in an industrial gas turbine have been generated in the diffuser. Measurements were made using a five holed Pitot probe. The research had been carried out to make a detailed investigation on the effect of struts and to advance computational and design tools for gas turbine exhaust diffusers.

Commentary by Dr. Valentin Fuster
2006;():93-107. doi:10.1115/ICES2006-1345.

Increasingly stringent emissions regulations aimed at drastically reducing particulate emissions from diesel engines pose one of the greatest challenges to diesel engine development today. Furthermore, engine manufacturers are finding it more and more difficult to comply with these new regulations through in-cylinder optimization alone. As a result, exhaust after-treatment systems, namely diesel particulate traps, present additional means for meeting these strict requirements. A previous study demonstrated the potential for diesel particulate emissions reduction using neat Fischer-Tropsch (F-T) fuel and blends. The absence of sulfur in F-T fuels permits the use of more aggressively catalyzed traps, as sulfur poisoning is not an issue. Furthermore, the reduced particulate emissions of F-T fuels leads to increased time between trap regenerations, which in conjunction with advanced catalyst formulations reducing the temperatures required to initiate regeneration, may provide substantial improvements in trap durability and performance. However, the deposition of particulates from F-T fuels on the trap substrates and loading and regeneration of the trap with F-T particulates and F-T fuel have not been adequately addressed. In this study a 2002, six-cylinder, 5.9 liter, Cummins ISB 300 diesel engine, outfitted with a fully instrumented particulate trap, was subjected to a subset of the Euro III 13-mode test cycle under steady-state operating conditions. In order to investigate the fundamental fuel effects on particulate trap loading characteristics, un-catalyzed Cordierite substrates were loaded with particulates generated from neat F-T diesel and a low sulfur diesel (LSD). Trap temperature, pressure drop, particulate emissions, and gaseous exhaust composition were monitored before and after the trap. The use of F-T fuel significantly extended the trapping period and reduced the regeneration frequency as compared to the LSD. Based on the differences in emissions and fuel composition, explanations for the observed differences in the trap performance were developed.

Commentary by Dr. Valentin Fuster
2006;():109-115. doi:10.1115/ICES2006-1351.

The monolithic catalytic converter still is the main pollution control device for modern vehicles in order to reach the ever-increasing legislative demands for low emission standards. The catalytic converters require a large expansion from the exhaust pipe to the front face of the monolith. Unfortunately, packaging constraints often do not permit the use of long diffusers. Hence, flow separation within the diffuser leads to a non-uniform flow distribution across the monolith. A uniform flow distribution at the inlet monolith face is favorable for the conversion efficiency as well as the durability of the catalytic converter. Therefore the main problem is to optimize the flow distribution at the catalytic converter. It should be noted that due to flow maldistribution in an enlarged inlet of catalytic converter, some part of the monolith would be non effective. In this research a new design for inlet diffuser of catalytic converter has been proposed and fabricated. The new inlet diffuser is composed of some tube to tube cones that distribute the flow uniformly at the entrance face of monolith. Temperature, pressure drop and concentration of pollutants, before and after catalyst, have been measured. The results show that the new design for inlet diffuser tends in less uniform temperature field at the entrance of monolith but the flow distribution becomes more uniform and an increased conversion efficiency of catalyst will be obtained.

Commentary by Dr. Valentin Fuster
2006;():117-122. doi:10.1115/ICES2006-1370.

Laser ignition is viewed as a potential future technology for advanced high-efficiency low-emission natural gas engines. However, in order to make laser ignition systems more practical, thereby enabling them to transition from the laboratory to industrial settings, there is a need to develop fiber optically delivered ignition systems. Recent work at Colorado State University has shown the possibility of using coated hollow fibers for spark delivery and has demonstrated laser ignition and operation of a single engine cylinder using hollow fiber delivery. In order to practically operate a multiple cylinder engine, we envisage a simple and low-cost system based upon a single laser source being delivered (“multiplexed”) through multiple fibers to multiple engine cylinders. In this paper, we report on the design, development, and initial bench-top testing of a multiplexer. Bench-top testing showed that the multiplexer can be positioned with the required accuracy and precision for launching into fiber optics, and can be switched at the relatively high switching rates needed to operate modern natural gas engines. Another test employed the multiplexer to alternately launch laser pulses into a pair of hollow fibers in a way that allows spark creation downstream of the fibers.

Commentary by Dr. Valentin Fuster
2006;():123-127. doi:10.1115/ICES2006-1391.

One of the main drivers in the automotive industry is the reduction in fuel consumptions and emissions. In order to achieve these goals, the weight of the engine block as well as the friction in the cylinder bore has to be optimized. This paper describes the FORD PTWA (Plasma Transferred Wire Arc) thermal spray process that protects the aluminum cylinder bore surface against wear by a thermal spray coating. The PTWA technology was originally developed for the application in gasoline V8 engines and it will be shown in this paper how this process can be modified to apply nano-material to produce high-wear resistant, low-friction coatings for highly loaded engine blocks for future demands. A large German BMBF “Nanomobile” Research Program was started in 2005 with 13 partners (DaimlerChrysler, Opel, Porsche, Ford, Gehring, Federal Mogul, GTV Thermal Spray Systems, DURUM, RWTH University and other institutes) in order to develop next generation nano-material coatings for cylinder bores.

Commentary by Dr. Valentin Fuster
2006;():129-135. doi:10.1115/ICES2006-1400.

The aim of this paper consists of establishing a methodology for oxidation catalyst modeling based on experimental tests and the development of a theoretical model with zero and one dimensional elements. Related to the theoretical work, the main aspects of such modeling are presented. It consists of describing the inner catalyst geometry by a combination of volumes and simple pipes network. The gas properties in volumes are calculated with a filling and emptying approach whereas the unsteady flow in pipes elements is considered to be one-dimensional and solved by using a finite difference scheme. Concerning the experimental tests, a study is carried out on a shock tube bench. The advantage of this experimental test bench is to study the propagation of a shock wave in the catalyst under controlled and convenient conditions, i.e. cold and non steady flow. Later, the model is set up by comparing the upstream and downstream pressure signals with the simulation results. Since the model lacks of relevant information of pressure losses at the inlet and outlet of the channels, which are rather difficult to compute due to the complex phenomena and flow maldistributions if the use of a 3D CFD code is avoided, the calibration of the model to match the experimental data is the decided approach. In this context, the shock wave test bench is used in order to excite the catalyst with non-steady flow conditions rather than to reproduce the conditions that will appear in real engine operation. The comparison shows good agreement between one-dimensional and experimental results. In order to validate this new modeling on a real engine configuration, an experimental validation is carried out in a four-stroke turbocharged Diesel engine. This experimental test bench allows to measure the main engine characteristics and performance as well as the instantaneous pressure upstream and downstream the catalyst. A simulation code has been also set up to model the engine and the comparison in terms of exhaust pressure pulses propagation inside the catalyst shows good agreement between the one-dimensional model and the experimental results.

Commentary by Dr. Valentin Fuster
2006;():137-145. doi:10.1115/ICES2006-1405.

For spark ignition engines, the fuel-air mixture preparation process is known to have a significant influence on engine performance and exhaust emissions. In this paper, an experimental study is made to characterize the spray characteristics of an injector with multi-disc nozzle used in the engine. The distributions of the droplet size and velocity and volume flux were characterized by a PDA system. Also a model of a 4 cylinder multi-point fuel injection engine was prepared using a fluid dynamics code. By this code one-dimensional, unsteady, multiphase flow in the intake port has been modeled to study the mixture formation process in the intake port. Also, one-dimensional air flow and wall fuel film flow and a two-dimensional fuel droplet flow have been modeled, including the effects of in-cylinder mixture back flows into the port. The accuracy of model was verified using experimental results of the engine testing showing good agreement between the model and the real engine. As a result, predictions are obtained that provide a detailed picture of the air-fuel mixture properties along the intake port. A comparison was made on engine performance and exhaust emission in different fuel injection timing for 2600 rpm and different loads. According to the present investigation, optimum injection timing for different engine operating conditions was found.

Commentary by Dr. Valentin Fuster
2006;():147-154. doi:10.1115/ICES2006-1407.

This paper presents a variable valve lifting methodology for turbocharged diesel engines. For this purpose, the diesel engine is modeled based on a modified mean-value engine modeling. An optimal control strategy is used for maximum volumetric efficiency acquirement. Using camless valve train strategy makes better fuel economy and improved air intake characteristics throughout the engine operating map. The system is capable of continuously, independently and virtually controlling all standard parameters of variable valve motion. This permits optimization of valve events for any operating condition without compromise. The optimized intake valve profile is determined, to have the best volumetric efficiency and proper operation for each running condition based on the existing model make use of numerical techniques. The model used in this paper is validated using simulation results of references. The model treats the cylinder and the manifolds as thermodynamic control volumes by using the filling and emptying method, solving energy and mass conservation equations with sub models for intake manifold, variable valve timing, cylinder breathing dynamics and turbocharger including turbine and compressor. This model is a crank angle based dynamic nonlinear model of a four-cylinder turbocharged (TC) diesel engine, which captures the interactions among the VVT actuation, the turbocharger dynamics and the cylinder-to-cylinder breathing characteristics. The model have been implemented in Matlab/Simulink and tested. This work shows the results obtained for air management control in a turbocharged diesel engine, specifically, manifold pressure and air mass flow. These variables are often required to achieve better power performance and lower emissions.

Topics: Diesel engines
Commentary by Dr. Valentin Fuster
2006;():155-162. doi:10.1115/ICES2006-1413.

This paper presents a computational investigation of the effect of exhaust temperature modulations on an automotive catalytic converter. The objective is to develop a better fundamental understanding of the converter’s performance under transient driving conditions. Such an understanding will be beneficial in devising improved emission control methodologies. The study employs a single-channel based, one-dimensional, non-adiabatic model. The transient conditions are imposed by varying the exhaust gas temperature sinusoidally. The results show that temperature modulations cause a significant departure in the catalyst behavior from its steady behavior, and modulations have both favorable and harmful effects on pollutant conversion. The operating conditions and the modulating gas composition and flow rates (space velocity) have substantial influence on catalyst behavior.

Commentary by Dr. Valentin Fuster
2006;():163-170. doi:10.1115/ICES2006-1417.

Short spark plug life, resulting in increased engine downtime and operating costs, is the primary factor limiting the power density and thermal efficiency in lean burn natural gas engines. Fundamentally, as engine power density increases, spark plug life decreases. Common approaches to increasing spark plug life include use of high melting temperature electrode materials and increased electrode surface area. However, future targets for engine efficiency and power density require more effective system solutions. In order to achieve these system solutions, work has been focused on developing an empirically derived electrode erosion model. This model quantifies spark plug life as a function of spark discharge characteristics, spark plug electrode design, and flow fields in the vicinity of the spark plug gap for different engine power densities. Furthermore, quenching effects resulting from large surface electrodes and smaller spark gaps have been included to verify ignitability for given in-cylinder charge density and air/fuel ratio conditions. A good agreement between experimental data and model predictions has been demonstrated. Finally, a solution for extending spark plug life in high efficiency, high power density, natural gas engines has been proposed. This solution combines high spark power with a spark plug design consisting of small electrode gap, large electrode surface, and with enhanced flow fields at the electrode gap.

Topics: Density , Gas engines
Commentary by Dr. Valentin Fuster
2006;():171-178. doi:10.1115/ICES2006-1430.

This paper addresses issues related with the measurement, analysis and real-time control of knocking combustions in high-performance spark-ignition engines. In particular, the relationship between output torque and knock intensity has been investigated. Issues examined include a methodology for identifying target knocking levels, and a critical comparison of different signals for extracting knock-related information. When considering high-performance spark-ignition engines, individual cylinder spark advance management that allows maximum output torque while protecting engine components from knock-related damage, is particularly complex. The first part of the activity is focused on an analysis aimed at the identification of a knocking level that allows reaching maximum performance while protecting engine components: For a given engine operating condition, such knocking level is shown to be constant for all the engine cylinders, and it is directly measurable through knock intensity indexes obtained by post-processing the in-cylinder pressure signal. If such knocking level is to be achieved during on-board operation, it is necessary to real-time reconstruct individual cylinder pressure-based knock indexes values. One of the main objectives of this work is therefore the evaluation of the impact that the adoption of an ion current sensing system would have on the performance of such a spark advance controller. The background of the second part of the work is the knocking-related information that can be extracted by real-time processing engine block vibration signals. The main drawbacks of such approach are related to the definition of the minimum number of sensors to be installed, to the evaluation of their optimal position, and to the signal-to-noise ratio typical of such systems, which becomes critical especially at high engine speeds. Possible solutions are the use of in-cylinder pressure or ion current sensors installed on board the vehicle. This work is mainly focused on ion sensing application, due to the still existing cost and reliability problems associated with the onboard application of in-cylinder pressure measuring systems. The second part of the work therefore deals with the correlation analysis between pressure based and ion current based knock intensity indexes. The experimental tests have been performed on a V12 6.0 liter and on a V12 6.2 liter high performance engines: Large spark advance sweeps were performed for each speed breakpoint, while acquiring 6 in-cylinder pressure and 6 ion current signals. Several indexes were extracted from both type of signals, in order to achieve both maximum correlation levels and physical consistency with knock-related damage. The results are particularly encouraging, since the correlation levels between pressure-based and ion current-based knock indexes are very high, thus allowing the definition of a closed-loop individual cylinder spark advance controller able to achieve the target knocking level.

Topics: Cylinders
Commentary by Dr. Valentin Fuster
2006;():179-186. doi:10.1115/ICES2006-1434.

The continuous increase in power density has led to higher thermal loading of pistons of heavy duty diesel engines. Material constraints restrict the maximum operating temperature of a piston. High piston temperature rise may lead to engine seizure because of piston warping. To avoid this, pistons are usually cooled by oil jet impingement from the underside of the piston in heavy duty diesel engines. Impingement heat transfer has been used extensively because of the high rates of cooling it provides. The associated high heat transfer rate is due to the oil jet that impacts hot impingement surface at high speed. However, if the temperature at the underside of the piston, where the oil jet strikes the piston, is above the boiling point of the oil, it may contribute to the mist generation. This mist significantly contributes to non tail-pipe emission (non-point source) in the form of unburnt hydrocarbons (UBHC’s). This paper presents and discusses the results of a numerical and experimental investigation of the heat transfer between a constant heat flux flat plate and an impinging oil jet. Piston boundary conditions are applied to the flat plate. Using the numerical modeling, heat transfer coefficient (h) at the underside of the piston is calculated. This predicted value of heat transfer coefficient significantly helps in selecting right oil grade, oil jet velocity, nozzle diameter and distance of the nozzle from the underside of the piston. It also helps to predict whether the selected grade of oil will contribute to mist generation. Using numerical simulation (finite element method) temperature profiles are evaluated by varying heat flux. Infrared camera is used to investigate and validate the temperature profile of the flat plate. High speed camera is used to capture the mist generation and oil jet breakup due to impinging jet.

Commentary by Dr. Valentin Fuster
2006;():187-196. doi:10.1115/ICES2006-1444.

The sensitivity of engine performance to gas-dynamic phenomena in the exhaust system has been known for around 100 years but is still relatively poorly understood. The nonlinearity of the wave-propagation behaviour renders simple empirical approaches ineffective, even in a single-cylinder engine. The adoption of analytical tools such as engine-cycle-simulation codes has enabled greater understanding of the tuning mechanisms but for multi-cylinder engines has required the development of accurate models for pipe junctions. The present work examines the propagation of pressure waves through pipe junctions using shock-tube rigs in order to validate a computational model. Following this the effects of exhaust-system gas dynamics on engine performance are discussed using the results from an engine-cycle-simulation program based on the equations of one-dimensional compressible fluid flow.

Commentary by Dr. Valentin Fuster

Applications of Emissions Technologies

2006;():197-207. doi:10.1115/ICES2006-1310.

In natural gas SI engines under lean conditions, NOx emissions reduction can be realized by injecting an additional mass flow rate to inlet gases. It can be easily done in situ using two techniques: EGR (Exhaust Gas Recirculation) or RGR (Reformed Gas Recirculation) which is an improvement of the usual EGR configuration. Exhaust gases are catalyzed before being reintroduced at the engine inlet. Reformed gases contain carbon monoxide and hydrogen in addition to carbon dioxide, steam and nitrogen dioxide that compose usual recirculated gases. In order to compare EGR and RGR concepts, the study is divided in three stages. Firstly, a “two-zone” thermodynamic model has been developed and validated on a large open chamber SI engine (18L CHP plant engine, fuelled by natural gas and equipped with data acquisition). Both in-cylinder pressure and NOx emissions have been compared between numerical results and experimental data. A good agreement is obtained, the error is less than 3%. Secondly, a widespread model of steam reforming on a Ni/MgOAl2 O3 catalyst has been used to compute in particular CO and H2 concentrations. Numerical results lead to a good concordance with experimental data from literature. Finally, SI engine and reformer models have been linked. RGR and EGR configurations have been numerically compared considering the same recirculation mass flow rate. According to the results, RGR is the best way to decrease significantly nitrous oxide emissions, while keeping good engine performance.

Commentary by Dr. Valentin Fuster
2006;():209-216. doi:10.1115/ICES2006-1330.

Exhaust gas recirculation (EGR) combined with particulate trap technology has proven to reduce nitrogen oxides (NOx ) and smoke emissions simultaneously at relatively low cost compared to other reduction strategies. An experimental study was conducted on a single cylinder, direct injection (DI) diesel engine to study the effect of EGR on engine performance and emissions under constant speed of 1500 rpm at various loads. In the present work hot and cool EGR were used to control the formation of NOx in a D.I diesel engine. The findings of both hot and cool EGR are discussed and compared at full load condition corresponding to the maximum allowable EGR proportion of 15%. It is found that cool EGR has a substantial reduction in NOx and smoke emissions compared to hot EGR. Based on the above result it is found that suitable particulate trap which is cost effective and high trapping efficiency is needed before the EGR cooler to reduce the smoke emissions to meet the emission standards. In the present study a substrate made of clay material was used in the particulate trap. They were made into spheres and coated with copper and zinc oxide catalyst material. The results have shown that EGR combined with particulate trap simultaneously reduces the NOx and smoke emissions by 63% and 42% respectively where as it increases brake specific fuel consumption by 10% compared to baseline mode.

Commentary by Dr. Valentin Fuster
2006;():217-224. doi:10.1115/ICES2006-1379.

The efficiency of natural-gas-fuelled reciprocating engines increased from an average value of 35% in the year 1990 to over 46% for large-bore engines in 2005. Increasing the load (bmep) of the engines helped to reduce the negative effect of friction losses on efficiency and to reduce the relative heat losses from the combustion process. Doubling the cylinder bore decreased the heat escaping from the cylinder process by about a factor two. The analyses show that further increases in bmep and bore diameter will hardly help in achieving a better efficiency. Reduction of the friction losses appears the best path to follow for an even higher efficiency. The authors do not expect that the efficiency of an Otto-cycle gas engine will substantially exceed 49%.

Topics: Engines
Commentary by Dr. Valentin Fuster

Fuels and Combustion

2006;():225-234. doi:10.1115/ICES2006-1306.

Biogas derived from organic waste materials is a promising alternative and renewable gaseous fuel for internal combustion (IC) engines and could substitute for conventional fossil fuels. The aims of this study are to review the past researches on biogas fuelled IC engines and from this review, to identify current research needs. A detailed analysis of the previous results of biogas fueling on the emissions and performance of spark ignition (SI) and dual fuel compression ignition (CI) engines is presented. The literature review reveals that the published research on biogas fueled IC engines are not rich in number and the scenario of biogas-diesel dual fuel engines is even worse. According to the analysis, biogas fueling in IC engines causes lower power output compared to natural gas, irrespective of the engine operating conditions. However, the use of biogas allows exhaust nitrogen oxides (NOx) emissions to be reduced substantially. Both experimental and computational analyses have been done in the case of SI engines. However, there are needs to investigate the exhaust emissions for the biogas-diesel dual fuel engines both experimentally and computationally. Also the effect of H2 S on engine emissions and life/durability, which is neglected very often in the literature, needs to be investigated.

Commentary by Dr. Valentin Fuster
2006;():235-245. doi:10.1115/ICES2006-1311.

This paper deals with the modelling and experimental work carried out on a BMW single cylinder spark ignition hydrogen engine. The authors have enhanced a 1D thermo-fluid dynamic simulation code in order to cope with the different chemical and physical aspects due to the fuelling of a spark ignition engine with hydrogen rather than with conventional gasoline. In particular the combustion module, which is based on a quasi-dimensional approach, has been extended by introducing the possibility of predicting the burning rate of the combustion of a homogeneous mixture of hydrogen and air. A fractal approach was followed for the turbulent flame speed evaluation, while an extend database for laminar burning velocities was created applying a kinetic simulation code for one-dimensional laminar flames. The modelling of the whole intake and exhaust systems coupled to the engine has been addressed, considering port-injection fuel system, in which hydrogen has been injected at very low temperature (cryogenic conditions). The fundamental 1D fluid-dynamic equations are solved by means of second order finite difference schemes; the working fluid is considered as a mixture of ideal gases, with specific heats depending on the gas temperature and the mole fractions of species, whose correlations for each specie (including para-hydrogen) have been extended in the region of low temperature. A first validation of the enhanced model is shown in the paper, comparing the computed results with the experimental data of in-cylinder pressures, intake and exhaust instantaneous pressure histories at different locations and NO emissions discharged by the cylinder.

Commentary by Dr. Valentin Fuster
2006;():247-256. doi:10.1115/ICES2006-1317.

Hydrogen is an attractive alternative energy carrier, which could make harmful emissions, global warming and the insecurity concerning oil supply a thing of the past. Hydrogen internal combustion engines can be introduced relatively easily, from a technological as well as from an economic point of view. This paper discusses the development of a model for the combustion of hydrogen in spark ignition engines, which has lead to a simulation program that can assist the optimization of these engines. The importance of a laminar burning velocity correlation taking stretch and instability effects into account is shown. The effects are particularly strong for the highly diffusive hydrogen molecule. In this paper, a laminar burning velocity correlation published previously by two of the authors is combined with a number of turbulent burning velocity models in a quasi-dimensional two-zone combustion model framework. After calibration of the combustion model for a reference condition, simulation results are compared with experimental cylinder pressure data recorded on a single cylinder hydrogen engine. Correspondence between simulation and measurement is shown for varying equivalence ratio, ignition timing and compression ratio. All models performed well for varying ignition timings and compression ratios; the real test proved to be the ability of the models to predict the effects of a varying equivalence ratio, this lead to a clear distinction in the models.

Commentary by Dr. Valentin Fuster
2006;():257-265. doi:10.1115/ICES2006-1331.

Single-cylinder research engines are valuable tools in the development of multi-cylinder reciprocating engines. The financial advantages of single-cylinder testing increases with engine size offering even larger benefits for medium-speed engines than light-duty automotive or heavy-duty truck engines. While testing on a single-cylinder engine provides a number of economic and technical advantages [1], careful planning and setup are required to maximize the usefulness of single-cylinder results as predictive of multi-cylinder performance. This paper describes the methodology used to set up and operate a single-cylinder medium speed diesel engine for combustion performance testing. An overview of the test cell design, infrastructure and instrumentation is provided, along with detailed specifications of the engine. There is good correlation between the single-cylinder and multi-cylinder performance when the gas-exchange-and frictional loss differences are taken into account. The strategy and results for this correlation effort are presented and discussed. The apparent rate of heat release was very consistent between the MCE and the SCE for the same load and injection timing. For other parameters, it was found that the single-cylinder engine contains biases relative to the absolute values observed from a full multi-cylinder engine, but the single-cylinder results are very useful in identifying relative performance trends and in performing in-cylinder optimization.

Commentary by Dr. Valentin Fuster
2006;():267-277. doi:10.1115/ICES2006-1335.

In-cylinder flows such as tumble and swirl have an important role on the engine combustion efficiencies and emission formations. In particular, the tumble flow, which is dominant in-cylinder flow in current high performance gasoline engines, has an important effect on the fuel consumptions and exhaust emissions under part load conditions. Therefore, it is important to know the effect of the tumble ratio on the part load performance and optimize the tumble ratio of a gasoline engine for better fuel economy and exhaust emissions. First step in optimizing a tumble flow is to measure a tumble ratio accurately. In this research the tumble flow was measured, compared and correlated using three different measurement methods: steady flow rig, 2-Dimensional PIV, and 3-Dimensional PTV. Engine dynamometer test was performed to find out the effect of the tumble ratio on the part load performance. Dynamometer test results of high tumble ratio engine showed faster combustion speed, retarded MBT timing, higher exhaust emissions, and a better lean burn combustion stability. Lean limit of the baseline engine was expanded from A/F=18:1 to A/F=21:1 by increasing a tumble ratio using MTV.

Commentary by Dr. Valentin Fuster
2006;():279-288. doi:10.1115/ICES2006-1346.

A new phenomenological model that was published in ref [1] encompasses the spray and the wall interaction by a simple geometrical consideration. The current study extends this earlier work with investigations made on 16 different engines from 6-engine families of widely varying features applied to off-highway as well as on-road duty. A dimensionless factor was introduced to take care of the nozzle hole manufactured by hydro-erosion, (HE) as well as the conical shape of the nozzle hole (K factor) in case of valve closed orifice type of nozzles. The smoke emitted from the wall spray formed after wall impingement is the major contributor to the total smoke at higher loads. As the fuel spray impinges upon the walls of the combustion chamber, its velocity decreases. This low velocity jet contributes to the higher rate of the smoke production. Therefore, the combustion bowl geometry alongwith injection parameters play a significant role in the smoke emissions. The satisfactory comparison of predicted and observed smoke over the wide range of operation demonstrated applicability of the model in simulation study of combustion occurring in DI diesel engines.

Topics: Diesel engines , Smoke
Commentary by Dr. Valentin Fuster
2006;():289-301. doi:10.1115/ICES2006-1359.

In order to comply with stringent pollutant emissions regulations a detailed analysis of the overall engine is required, assessing the mutual influence of its main operating parameters. The present study is focused on the investigation of the intake system under actual working conditions by means of 1D and 3D numerical simulations. Particularly, the effect of EGR distribution on engine performance and pollutants formation has been calculated for a production 6 cylinder HSDI Diesel engine in a EUDC operating point. Firstly a coupled 1D/3D simulation of the entire engine geometry has been carried out to estimate the EGR rate delivered to every cylinder; subsequently the in-cylinder flow field has been evaluated by simulating the intake and compression strokes. Finally the spray and combustion processes have been studied accounting for the real combustion chamber geometry and particularly the pollutants formation has been determined by using a detailed kinetic mechanism combustion model. The 1D/3D analysis highlighted a significant cylinder to cylinder EGR percentage variation affecting remarkably the pollutant emissions formation, as evaluated by the combustion process simulations. A combined use of commercial and in-house modified codes has been adopted.

Commentary by Dr. Valentin Fuster
2006;():303-316. doi:10.1115/ICES2006-1367.

An original technique for the detection of combustion start in SI engines on a cycle-by-cycle basis was proposed and applied to the analysis of pressure time-histories taken on a bi-fuel engine fueled by either gasoline or CNG. Such a technique locates the onset of combustion on the basis of the earliest release of chemical energy. It stems from the fact that, during the compression stroke, changes in the charge sensible energy, and thus in the cylinder pressure, are ruled only by work and heat exchanges with the combustion chamber walls. Hence, an imbalance in these three energies indicates the correspondent release of chemical energy, identifying combustion onset. The results of this technique were compared to those obtained through a direct analysis of in-cylinder pressure time-histories on logarithmic-coordinates p-V diagrams. More specifically, compression stroke appears like a segment on such diagrams and thus combustion onset can be defined by the detachment of in-cylinder pressure curve from linearity. The results of the different approaches for combustion start detection were compared on a wide range of working conditions of the bi-fuel SI engine under both gasoline and CNG fueling. The experimental matrix covered different engine speeds (N = 2000–4600 rpm), loads (bmep = 200–790 kPa), relative air-fuel ratios (RAFR = 0.80–1.60) and spark advances (SA ranging from 8 deg retard to 2 deg advance from MBT timing). 100 consecutive in-cylinder pressure traces were analyzed for each point in the test matrix. Particular attention was also given to the techniques applied for in-cylinder pressure filtering, which proved to be fundamental for accurate cycle-by-cycle investigation. Finally, on the basis of the experimental results obtained through the chemical-energy approach, two correlations for flame-development angle prediction are proposed, one for gasoline and the other for CNG. These correlations are based on cylinder-average thermodynamic properties at SA and can be usefully applied for triggering the flame propagation routines in indicated-cycle simulation codes.

Commentary by Dr. Valentin Fuster
2006;():317-332. doi:10.1115/ICES2006-1369.

In ‘Multijet’ Common Rail (C.R.) diesel injection systems, when two consecutive injection current-pulses are approached to each other, the fusion of the two injections can occur. This causes undesired excessive amount of injected fuel, which leads to worsening of particulate emissions and fuel consumption. In order to avoid such a phenomenon, lower limits to the values of dwell time are introduced in the control unit maps, by means of a conservatively overestimated threshold, limiting the flexible management of multiple injections and C.R. system capability to perform a larger number of injection shots. The reason of the injection fusion is mainly due to the time delay between the electrical signal to the solenoid and the needle lift at both valve opening and closure. In particular, the dwell-time range inside of which injection fusion occurs was shown to decrease by reducing the nozzle closure delay. Experimental tests were carried out on a high-performance Moehwald-Bosch MEP2000/CA4000 test bench for determining the functional dependence of nozzle closure and opening delays on solenoid energizing time and nominal rail pressure. Besides, a mathematical relation between the solenoid energizing time and the injection time interval was determined. A Multijet C.R. injection system mathematical model, that was previously developed, including thermodynamics of liquids, fluid dynamics, subsystem mechanics, and electromagnetism equations, was applied to better understand the cause and effect relationships for nozzle opening and closure delays. In particular, numerical results on the time histories of delivery- and control-chamber pressures, pilot- and needle-valve lifts, mass flow rates through Z and A holes, were obtained and analyzed in order to highlight the dependence of nozzle opening and closure delays on electro-injector internal geometric features and on the needle dynamics. For all the considered operating conditions, the model predictions were compared to the experimental injection flow-rate patterns and to the pressure data taken at the injector inlet, for assessment. The nozzle closure delay was shown to strongly depend on the needle dynamics. Parametric tests were carried out with the numerical code by changing needle and control plunger mass, needle spring preload and stiffness, maximum needle stroke, in order to identify configurations useful for minimizing the nozzle closure delay. On the basis of the indications derived from these numerical tests, a modified version of the commercial electro-injector was realized so as to achieve effectively reduced nozzle closure delays and very close sequential injections without any fusion between them.

Topics: Solenoids
Commentary by Dr. Valentin Fuster
2006;():333-340. doi:10.1115/ICES2006-1375.

The methyl esters of vegetable oils, known as biodiesel are becoming increasingly popular because of their low environmental impact and potential as a green alternative fuel for diesel engines. They do not require significant modification in existing engine hardware. Methyl ester of rice bran oil (ROME) is prepared through the process of transesterification. Previous research has shown that ROME has comparable performance, lower bsfc in comparison to diesel. There was reduction in the emissions of CO, HC, and smoke but NOx emissions increased. In the present research, experimental investigations have been carried out to examine the combustion characteristics of a direct injection transportation diesel engine running with diesel, and 20% blend of ROME with diesel. A four-stroke, four-cylinder, direct-injection transportation diesel engine (MDI 3000) was fully instrumented for the measurement of combustion pressure, rate of pressure rise and other combustion parameters such as instantaneous heat release rate, cumulative heat release rate, mass fraction burned etc. Tests were performed at different loads ranging from no load to 100%, at constant engine speed. No engine hardware modification was carried out for the present study. A careful analysis of combustion and heat release parameters has been carried out, which gives precise information about the in-cylinder combustion of rice bran oil based biodiesel vis-à-vis mineral diesel.

Commentary by Dr. Valentin Fuster
2006;():341-350. doi:10.1115/ICES2006-1376.

The characterization of diesel sprays for the simulation-based optimization of injection strategies and combustion chamber geometries is of particular importance to reach future targets concerning performance, fuel consumption and emissions. The prediction quality of this simulation process depends largely upon the adequate calibration of the spray models used. This paper aims to present the experimental setup of a spray box, the applied optical visualization techniques and the results. Furthermore, it will show the adjustment and the validation of the simulation models based on the experimental analysis.

Commentary by Dr. Valentin Fuster
2006;():351-362. doi:10.1115/ICES2006-1377.

A variety of gaseous fuels and wide range of cooled EGR could be used in turbocharged S.I. gas engines. This makes experimental investigation of knocking behavior both unwieldy and uneconomical. Accordingly, it would be attractive to develop suitable effective predictive model that can be used to improve understanding the role of various design and operating parameters and achieve a more optimized turbo-charged engine operation. A two-zone predictive model developed mainly for naturally aspirated S.I. engine applications of natural gas and validated earlier, was extended to consider applications employing turbochargers, after-coolers and cooled EGR. A suitably detailed kinetic scheme involving 155 reaction steps and 39 species for the oxidation of natural gas is employed to examine the pre-ignition reactions of the unburned natural gas-air mixtures that can lead to knock before being fully consumed by the propagating flame. The model predicts the onset of knock and its intensity once end gas auto-ignition occurs and considers the effects of turbo-charging and cooled EGR on the total energy to be released through auto-ignition and its effect on the intensity of the resulting knock. The consequences of changes in the effectiveness of after- and EGR-coolers when fitted, lean operation and reductions in the compression ratio on engine performance parameters, especially the incidence of knock were examined. The benefits, limitations and possible penalties of the application of fuel lean operation combined with cooled EGR are also examined and discussed.

Commentary by Dr. Valentin Fuster
2006;():363-370. doi:10.1115/ICES2006-1378.

A new kind of electromagnetic valve [1], with great flow and fast speed, used in the medium pressure common rail electronically controlled fuel injection system of diesel engine is introduced for the first time. It is a kind of Two-position, Three-way Valve (TTV) that consists of a valve body, an outer valve rod and two inner valve rods. The electromagnet can generate great electromagnetic force because of its assembled magnetic fields. It actuates the outer valve rod from its closed-position to the open-position rapidly. A spring is used to push it back. Fuel injection begins when the outer rod is in the open position and ends in the closed. The inner and outer valve rods with taper valve port replace the traditional configuration and decrease the difficulties in machining. Finite element method has been used to analyze the electromagnet’s electromagnetic fields. Static characteristics of the electromagnet are calculated. Some factors such as working area, coil turns, core number, armature depth and iron material that influence the magnetic force are discussed in detail. The magnetic material and the electromagnet dimensions are optimized according to calculation results. Meanwhile, the leakage between the valve body and the outer valve rod, the leakage between the outer valve rod and left-inner valve rod and the leakage between the outer valve rod and the right-inner valve rod are also studied by the finite element method. Key part that causes the leak during operation has been found out and improvement is carried out. Influences of the TTV to the injection timing and the injection amount are analyzed in detail based on the Fuel Injection Test Platform (FITP) in the end.

Commentary by Dr. Valentin Fuster
2006;():371-381. doi:10.1115/ICES2006-1382.

The paper analyses, by means of a parallel experimental and computational investigation, the performances of a small HSDI turbocharged Diesel engine. As far as the numerical approach is concerned, an in-house ID research code for the simulation of the whole engine system has been enhanced by the introduction of a multi-zone quasi-dimensional combustion model, tailored for multi-jet direct injection Diesel engines. This model takes into account the most relevant issues of the combustion process: the spray development, the in-cylinder air-fuel mixing process, the ignition and formation of the main pollutant species, such as nitrogen oxides and particulate. The prediction of the spray basic patterns requires the previous knowledge of the fuel injection rate. Since the direct measure of this quantity at each operating condition is not a very practical proceeding, an empirical model has been developed in order to provide reasonably accurate injection laws from a few experimental characteristic curves. The results of the simulation at full load are compared to experiments, showing a good agreement on brake performance and emissions. Furthermore, the combustion model tuned at full load has been applied without any change to the analysis of some operating conditions at partial load. Still, the numerical simulation provided results which qualitatively agree with experiments.

Commentary by Dr. Valentin Fuster
2006;():383-392. doi:10.1115/ICES2006-1384.

Biodiesel blends from two different origins (Canola and Frying oil) were prepared and tested at B5, B20 and B100 concentrations on single cylinder medium-speed research engine at ESDC Inc. The effect of these six fuels (three concentrations, B5, B20 and B100 of each source) on exhaust emissions, fuel consumption (BSFC) and engine horsepower were compared to those of Low Sulphur # 2 Petro-diesel fuel. The engine was tested under three different test settings; Idle, 50% Load and 100% Load. The results showed: reduction in emissions (except NOX) for B5 and B20 of Canola and Frying oil blends while maintaining engine power and fuel efficiency in an acceptable range (within 2%). For B100 blends, reductions were more significant for CO and Smoke opacity but significant increase for NOX and PM emissions. Engine break horsepower was also decreased by %8–%9 with B100 blends. Engine Heat Value Release rate and Fuel Injection Pressure were also recorded for better assessment of fuel efficiency and emission results.

Commentary by Dr. Valentin Fuster
2006;():393-400. doi:10.1115/ICES2006-1387.

Nowadays, increased attention has been focused on internal combustion engine fuels. Regarding environmental effects of internal combustion engines particularly as pollutant sources and depletion of fossil fuel resources, compressed natural gas (CNG) has been introduced as an effective alternative to gasoline and diesel fuel in many applications. A high research octane number allows combustion at higher compression ratios without knocking and good emission characteristics of HC and CO are major benefits of CNG as an engine fuel. In this paper, CNG as an alternative fuel in a spark ignition engine has been considered. Engine performance and exhaust emissions have been experimentally studied for CNG and gasoline in a wide range of the engine operating conditions.

Commentary by Dr. Valentin Fuster
2006;():401-409. doi:10.1115/ICES2006-1392.

The characteristics of HCCI combustion were investigated experimentally in a variable compression ratio CFR engine when operating on lean mixtures of n-heptane and n-pentane in air. The effects of changes in equivalence ratio, compression ratio, the addition of nitrogen, carbon dioxide, and methane into the intake charge on the cyclic variation in the ignition and the development of the combustion processes were investigated. The limiting conditions that produce ignition in one cycle only among many, repeated ignition in every cycle, and knock were identified. It was found that HCCI combustion and the range of its operating conditions are limited by the extent of non-homogeneity of the intake charge, both in mixture quality and temperature. The optimum values for the addition of nitrogen, carbon dioxide, and natural gas to produce higher indicated work and reduce cyclic variation and the intensity of energy release depend on the intake mixture strength and specific operational conditions.

Commentary by Dr. Valentin Fuster
2006;():411-419. doi:10.1115/ICES2006-1397.

Charge dilution, due to the reduced combustion temperatures that it brings about, has long been proven as effective means of reducing Nitrogen Oxides (NOx ) emissions in reciprocating engines. The extent of this dilution is practically bounded on the lean side of stoichiometric conditions by engine misfire or the point at which the combustion process is no longer sufficiently reliable to sustain engine operation within some specified limit. Extending this misfire limit of an engine becomes a worth while goal as it brings about further reductions in NOx emissions. Much work has been dedicated to reaching this end and several techniques have proven viable in natural gas fueled engines. This work explores potential synergies between two proven techniques for NOx reductions in lean-burn natural gas fueled engines, hydrogen enrichment of the natural gas fuel and application of laser spark ignition. Independently both techniques have been shown to provide significant NOx emissions reductions through lean limit extension in spark ignited gaseous fueled reciprocating engines [1–11, 13–15]. Here hydrogen is blended with natural gas at five different levels ranging from 0% to 40% by volume in a single cylinder engine. The mixtures are fired using a conventional spark plug based ignition system and then again with an open beam path laser induced breakdown spark ignition system. NOx emissions measurements were made at different levels including misfire conditions for each level of hydrogen enrichment with both ignition systems. Data are presented and the emissions and engine performance of two configurations are compared to determine realizable benefits that arise from combining the two techniques.

Commentary by Dr. Valentin Fuster
2006;():421-427. doi:10.1115/ICES2006-1398.

Although hydrogen is considered one of the most promising future energy carriers, there are several challenges to achieving a “hydrogen economy,” including finding a practical, efficient, cost-effective end-use device. Using hydrogen as a fuel for internal combustion engines is seen as a bridging technology toward a large-scale hydrogen infrastructure. To facilitate high-efficiency, high-power-density use of hydrogen with near-zero emissions in an internal combustion engine, detailed analysis of the hydrogen combustion process is necessary. This paper presents thermodynamic results regarding engine performance and emissions behavior during investigations performed on a single-cylinder research engine fueled by pressurized gaseous hydrogen. Avoiding combustion anomalies is one of the necessary steps to further improve the hydrogen engine power output at high-load operation while, at the same time, reducing fuel consumption and emissions during part-load operation. The overall target of the investigations is an improved combustion concept especially designed for hydrogen-engine-powered vehicles. Future activities include performing optical imaging of hydrogen combustion by using an endoscope. We will also investigate supercharged external mixture formation, as well as hydrogen direct-injection operation.

Topics: Combustion , Ice
Commentary by Dr. Valentin Fuster
2006;():429-436. doi:10.1115/ICES2006-1399.

Experimental investigations were carried out to assess the use of hydrogen in a Gasoline Direct Injection (GDI) engine. Injection of small amounts of hydrogen (up to 27% on energy basis) in the intake port creates a reactive homogeneous background for the direct injection of gasoline in the cylinder. In this way, it is possible to operate the engine with high EGR rates and, in certain conditions, to delay the ignition timing as compared to standard GDI operation, in order to reduce NOx and HC emissions to very low levels and possibly soot emissions. The results confirmed that high EGR rates can be achieved and NOx and HC emissions reduced, showed significant advantage in terms of combustion efficiency and gave unexpected results relative to the delaying of ignition, which only partly confirmed the expected behavior. A realistic application would make use of hydrogen-containing reformer gas produced on board the vehicle, but safety restrictions did not allow using carbon monoxide in the test facility. Thus pure hydrogen was used for a best-case investigation. The expected difference in the use of the two gases is briefly discussed.

Commentary by Dr. Valentin Fuster
2006;():437-442. doi:10.1115/ICES2006-1402.

This paper summarizes the analytical and experimental investigation of fuel-injection-controllable medium speed diesel engines using kerosene fuels. The investigation focuses on analyzing and testing the effects of using JP-8 kerosene fuel for an engine of this type, on engine fuel injection, in-cylinder combustion, and output performances and exhaust emissions. Main properties of JP-8 fuel compared to those of conventional 2-D diesel in affecting the engine processes are identified and analyzed in connection with the engine processes. The consequent effects are analytically predicted prior to actual engine testing. Results from testing a medium-speed diesel engine using 2-D diesel and JP-8 fuel separately are presented and agree closely in the trends of variation with the analysis and prediction.

Topics: Fuels , Diesel engines
Commentary by Dr. Valentin Fuster
2006;():443-454. doi:10.1115/ICES2006-1414.

This paper deals with a numerical investigation of a single cylinder diesel engine equipped with mechanical fuel direct injection system and focuses on the fuel injection system modelling with the aim of predicting the performance of the entire injection system, the spray characteristics, the interaction among spray-cones, combustion chamber flows and geometry. In the simulations, two different codes have been used. With the former one, AMESim code, the complete injection system has been analysed and the single components have been selected and modelled. The results obtained from the injection system simulation, in terms of injection needle lift, injection flow rate, pressure time evolution, have been used to initialize the latter computation tool, FIRE code, in which 3D flow numerical investigation of the internal injector flow has been performed. Since such a flow is directly linked to the spray modelling, the primary break-up effects have been taken into account. The details of the adopted modelling strategy have been shown and the results of each simulation step have been presented. In order to highlight the relationship among the nozzle flow condition and the spray formation-vaporization characteristics, a comparison between two different calculation setups has been shown. Moreover, a qualitative comparison among predictions and experimental data has been discussed.

Commentary by Dr. Valentin Fuster
2006;():455-463. doi:10.1115/ICES2006-1415.

The present work treats the problems and phenomena related to the soot deposition inside a modern Diesel particulate filter, in order to realize a numerical model able to analyze how particulate matter lays down and grows over the porous walls inside a non-catalyzed diesel particulate filter. The geometry of a commercial device has been imported in a 3D CFD code and the phenomena related to the fluid while it passes through the porous media of the filter have been viewed upon with an unsteady approach for different values of engine power and torque. The obtained velocity fields have been used to calculate the profile of deposited soot after a chosen operation period and the geometry of the filter has been then refreshed for the subsequent quasi-steady simulation. The backpressure due to the growing of the soot layer has been calculated.

Commentary by Dr. Valentin Fuster
2006;():465-477. doi:10.1115/ICES2006-1426.

In Multijet Common Rail (C.R.) systems, the capability to manage multiple injections with full flexibility in the choice of the dwell time (DT) between consecutive solenoid current pulses is one of the most relevant design targets. Pressure oscillations triggered by the nozzle closure after each injection event induce disturbances in the amount of fuel injected during subsequent injections. This causes a remarkable dispersion in the mass of fuel delivered by each injection shot when DT is varied. The present works aims at investigating hydraulic circuit design keys to improve multiple injection performance of C.R. systems, by virtually removing the dependence of the injected fuel amount on DT. A Multi-Jet C.R. of the latest solenoid-type generation was experimentally tested at engine-like operating conditions on a high performance test bench. The considerable influence that the injector supplying pipe can exert on induced pressure oscillation frequency and amplitude was widely investigated and a physical explanation of cause-effect relationships was found by energetics considerations, starting from experimental tests. An optimization study was carried out to identify the best geometrical configurations of the injector supplying pipes so as to minimize pressure oscillations. The analysis was carried out with the aid of a previously developed simple zero-dimensional model, allowing the evaluation of pressure wave frequencies as functions of main system geometric data. Purposely designed orifices were introduced into the rail-pipe connectors or at the injector inlet, so as to damp pressure oscillations. Their effects on injection system performance were experimentally analyzed. Hydraulic circuit solutions that apply both optimized injector inlet-pipe sizes and oscillation damping orifices at the rail outlet were thoroughly investigated. Finally, the influence of the rail volume on pressure wave dynamics was studied to evaluate the possibility of severely reducing the rail capacitance. This would lead to a system, not only with reduced overall dimensions, but also with a prompter dynamic response during engine transients.

Topics: Fuels , Circuit design
Commentary by Dr. Valentin Fuster
2006;():479-485. doi:10.1115/ICES2006-1428.

Internal combustion engine development nowadays is characterized by decrease of exhaust gas emissions and increase of specific power and torque. Combustion noise excitation and fuel consumption have to be decreased in parallel. All these goals can be met today due to the development of advanced combustion systems and the increased flexibility of fuel injection system and ECU. But hereby, combustion system development and vehicle application have become more complex in recent times. A precise and simple description of ‘combustion noise’ is not trivial in this context. The customer subjective impression of e.g. diesel knock intensity, at vehicle interior and exterior, is the relevant value for this. Combustion noise excitation today is described by using the in-cylinder pressure based FEV CSL. Full calibration NVH potential is explored hereby, while meeting the emission and fuel consumption targets. FEV CSL-CAL is the in-house developed tool for NVH related vehicle calibration. All important ECU parameters are optimized simultaneous under the customer-relevant driving conditions hereby. Additionally, sound quality objective parameters for judgment of subjective combustion noise impression — FEV SQO — are used to find the optimal calibration map, for steady state as well as for cold start and during acceleration. By all this, combustion noise is described well and can be optimized toward customer expectation.

Commentary by Dr. Valentin Fuster
2006;():487-498. doi:10.1115/ICES2006-1432.

In SI engines the ignition process strongly affects the combustion process. Its accurate modelling becomes a key issue for a design-oriented CFD simulation of the combustion process. Different approaches to simulate ignition have been proposed. The common base is decoupling the physics related to the very first ignition phase when a plasma is formed from that of the development of the flame kernel. The critical point of ignition models is related to the capability of representing the effect of ignition system characteristics, the criterion used for flame deposit and the initialisation of the combustion model. This paper aims to present and validates extensively an ignition model suited for CFD calculation of premixed combustion. The ignition model implemented in a customized version of the Kiva 3 code is coupled with ECFM Flamelet combustion model. The ignition model simulates the plasma/kernel expansion based on a lump evaluation of main ignition processes (i.e., breakdown, arc-phase and glow phase). A double switch criterion based on physical and numerical consideration is used to switch to the main combustion model. The Herweg and Maly experimental test case has been used to check the model capability. In particular, two different ignition systems having different amount of electrical energy released during spark discharge are considered. Comparisons with experimental results allowed testing the model with respect to its capability to reproduce the effects of mixture equivalence ratio, mean flow, turbulence and spark energy on flame kernel development as never done before in three-dimensional RANS CFD combustion modelling of premixed flames.

Commentary by Dr. Valentin Fuster
2006;():499-506. doi:10.1115/ICES2006-1445.

The long time challenge for diesel engine manufacturers has been to reduce both particulate matter (PM) and NOx emissions simultaneously without sacrificing engine performance. One technique for reducing PM has been to inject air or oxygen-enriched air directly into the combustion chamber. Previous studies using the KIVA-3V computational fluid dynamics (CFD) model have shown benefits and the importance of the gas injection’s characteristics on the technique’s effectiveness in reducing emissions. Using a Caterpillar 3401E single cylinder engine, an experimental investigation has been conducted to demonstrate the effectiveness of an oxygen-enriched air injection system and fuel injection timing retard in reducing the NOx and the PM emissions in terms of both the particulate size and concentration. The gaseous emissions were measured using a Pierburg AMA 2000 gaseous emissions bench which included a chemiluminescent analyzer for NOx volumetric measurements, non-dispersive infrared (NDIR) analyzer for CO and CO2 measurements, and a parametric fuel cell for O2 measurements. PM emissions (i.e., soot particle concentration and size distribution) were measured using a TSI Model 3936 Scanning Mobility Particle Sizer (SMPS). The experimental observations regarding the effects of oxygen-enriched air injection on NOx and PM emissions were in accord with the previously reported results for late-cycle gas injection from a KIVA-3V model. The air injection technique additionally provided a low level of oxygen-enrichment during the compression cycle, with results similar to previous intake air oxygen-enrichment studies. A simultaneous reduction of NOx and particulates was demonstrated when the fuel injection timing characteristics were optimized in conjunction with the oxygen-enriched air injection. The experimental PM emissions were analyzed for number and size distributions and also found to be consistent with previously reported trends.

Commentary by Dr. Valentin Fuster

Engine Design and Analysis

2006;():507-515. doi:10.1115/ICES2006-1303.

Cummins recognized a sales growth opportunity in the gas compression market place in 2001. Natural Gas Engine Engineering then started developing the smallest displacement engines in the product line first. These are engines in the 37 to 225 kilowatt range and were introduced successfully into the market place over the last four years. Two years ago, the next step up in horsepower, the 19 liter, inline six cylinder KTA 19GC engine at 313 kilowatt was released for production. Marketing then determined that the 450 to 670 kilowatt market was underserved and decided to develop the V12 version of the KTA 19GC, the KTA38GC, to fill this need. It was recognized early in the program that the engine needed to be simple and robust because engine uptime is at a premium in the higher horsepower segments of this market. Thus, simple, robust and proven components were chosen for the engine. The project team started with the KTA38 diesel engine. The team then added the KTA19GC power cylinder components. Next, an ignition system, air/ratio control system and an electronic integrated throttle/governor system were added. These were all “off the shelf” components. When adding these components, an emphasis was placed on simplicity, user friendliness, and self diagnostics with or without a laptop computer. The engine development team was located in Columbus, IN and Clovis, NM, the design team was located in Daventry, England (the final manufacturing location) and Columbus, IN and the analysis team in Pune, India. In addition, our lead customer and distributor, both located in Texas, were closely involved in the project and added considerably to its success. The efforts of these five locations were coordinated in Columbus, IN.

Topics: Compression
Commentary by Dr. Valentin Fuster
2006;():517-523. doi:10.1115/ICES2006-1308.

Steel spring couplings for applications such as drive lines, gear drives etc. are installed between two shafts to transmit torque from one shaft to another while influencing the torsional vibrations and accommodating misalignments between the shafts. The main focus is to control the torsional vibrations both by moving the critical resonances out of the operating speed range and damping the remaining vibrations to acceptable levels. The market offers various coupling designs, one of them is the Geislinger Steel Spring Coupling. The stiffness of the coupling leaf springs can be precisely tuned to isolate or move harmful natural resonance frequencies. In addition Geislinger Couplings provide a unique hydrodynamic damping via oil displacement, which effectively absorbs torsional vibrations. The Steel Spring Coupling concept meets not only the demands of any type and size of internal combustion engine, but also the demands of a variety of other machinery systems. Applications for pumps and compressors are typical ones. This paper will present design features, analysis parameters as well as examples of actual applications in order to show how the coupling design is able to meet the torsional requirements.

Topics: Steel , Vibration , Springs
Commentary by Dr. Valentin Fuster
2006;():525-538. doi:10.1115/ICES2006-1319.

A project has been undertaken to design, build and test internal combustion engine poppet valves made from resin transfer molded (RTM) Fiber Reinforced Composites (FRCs). For poppet-valve engines, the valve train mass and stiffness is of particular importance because valve train natural frequency and the onset of valve float and bounce typically limit the engine operating speed. This in turn limits engine power and performance. FRC poppet valves offer the potential for substantial mass reduction as well as increased component stiffness. This enables reduced power consumption by the valve train, and increased overall engine efficiency. Resin transfer molding was chosen because of potential for high-volume production and near-net shape products. Valve design details include; identification of valve operating requirements, fiber orientations, material selection, and evaluation of potential solutions using computerized structural analysis. Mold design includes; mold configuration requirements, fiber placement strategies evaluated, intermediate validation testing done and initial prototype configuration. Results include the final valve design for an exhaust valve, fiber and matrix material selection, fiber placement strategy, and mold configuration. Plans for additional validation testing are presented.

Commentary by Dr. Valentin Fuster
2006;():539-549. doi:10.1115/ICES2006-1326.

The design of intake ports for high-performance internal combustion engines has traditionally relied on steady-state flow benches and prototype core boxes. In this study, Computational Fluid Dynamics (CFD) methods were employed to gain further insight into the characteristics of a high-performance motorcycle engine. In this particular engine configuration, the throttle is located in very close proximity to the intake port, and the effects of throttle position on the intake flow characteristics were examined. This study shows that steady-state CFD analysis can be used in combination with traditional flow optimization techniques to provide further insight for cylinder head development. The intake flow behavior in this engine was found to vary considerably as a function of valve lift and throttle position. It was found that at low valve lifts the intake flow is relatively uniform around the periphery of the intake port, but at high valve lifts the flow into the cylinder is biased towards the top of the intake port. This results in a tendency to promote tumble at high valve lifts, but not at low valve lifts. Small throttle opening angles were found to magnify the flow biasing effect at high valve lifts.

Commentary by Dr. Valentin Fuster
2006;():551-557. doi:10.1115/ICES2006-1333.

In this Study, radiator performance for passenger car has been studied experimentally in wide range of operating conditions. Experimental prediction of Nusselt number and heat transfer coefficient for coolant in radiator tubes are also performed with ε–NTU method. The total effectiveness coefficient of radiator and heat transfer coefficient in air side is calculated via try and error method considering experimental data. The Colburn factor and pressure drop are also estimated for this heat exchanger. Examples of application demonstrate the practical usefulness of this method to provide empirical data which can be used during the design stage.

Commentary by Dr. Valentin Fuster
2006;():559-567. doi:10.1115/ICES2006-1357.

High combustion gas pressure and mass reduction of modern automotive engines have generated new problems in mechanical assemblies. For example, it is now common to observe bearing shell rotation in the conrod of automotive prototype engines at the design stage. The consequence is sometimes the seizure of the bearing due to the presence of the joint face relief in the loaded area. Physically, the bearing shell rotation results from cumulated microslip between the bearing and the conrod. To have a better physical approach of the phenomenon and propose design recommendations, we have performed analyses based on the strength of material theory and numerical modellings. These tools permit us to obtain simple models allowing an easier mechanical understanding as well as an analysis of sensitivity to different parameters. The main results presented in this paper are: • The basic description of the phenomenon, • The modelling of the conrod, its sensitivity to deformation and numerical validation, • The analysis of the microslip between the bearing shell and the conrod, • The sensitivity analysis with respect to conception and physical parameters.

Topics: Bearings
Commentary by Dr. Valentin Fuster
2006;():569-577. doi:10.1115/ICES2006-1366.

The dynamic behavior of a typical four-stroke, medium-speed, marine diesel engine driving a Controllable Pitch Propeller (CPP) is investigated during ship maneuvering including fast propeller pitch changes. A modular model has been developed in Simulink/Matlab for the simulation of the dynamics of ship propulsion. The developed model considers the ship propulsion system as a set of three main modules: the engine, the propeller and the ship hull. The developed ship propulsion dynamics model has been validated with a wide range of experimental data from a 500 kW test engine (MAN B&W 5L16/24), coupled to a four quadrant electric brake (AEG), installed at the test-bed of the Laboratory of Marine Engineering of the National Technical University of Athens (NTUA/LME). The model was then used for the investigation of marine diesel engine behavior during load changing including some extreme maneuvering case scenarios such as Crash Stop, Full Astern and Full Ahead maneuvers. The resulting ship propulsion model is a reduced order model, which can easily be used for detailed studies such as engine-control during fast transient loadings, with accuracy and small computational cost.

Commentary by Dr. Valentin Fuster
2006;():579-591. doi:10.1115/ICES2006-1383.

The paper proposes some design criteria for the MotoGP engines, complying with the FIM 2007 Technical Regulations. Five configurations have been considered: 3-cylinder in-line, 4-cylinder in-line, and three V-engines with 4, 5 and 6 cylinders. All the analyzed solutions have been optimized from a fluid-dynamic point of view, by means of 1D engine cycle simulations. Then, the engines are compared in terms of full load performance, at steady conditions. Finally, the influence of engine performance, along with operations regularity and motorbike weight, is assessed by means of a lap time simulator, developed by the author on the base of real data. The best configurations turned out to be the 4-cylinder engines, while 3-cylinder and 5-cylinder are quite penalizing.

Topics: Engines , Optimization
Commentary by Dr. Valentin Fuster
2006;():593-604. doi:10.1115/ICES2006-1410.

This paper presents the results of an investigation into the comparison between measured and simulated intake system dynamics of the Peugeot XU7-L3 engine. Simulation and Experimental tests are conducted at full throttle operating conditions ranging from 1500 to 6000 rpm under firing operation. Comparisons of basic engine performance parameters, showed a good correlation between measurement and simulation.

Commentary by Dr. Valentin Fuster
2006;():605-614. doi:10.1115/ICES2006-1420.

While the deformation and damage behavior of aluminum cylinder heads under complex thermal mechanical loading has been the subject of numerous studies in the past, cast iron cylinder heads have been in the focus of thermomechanical fatigue (TMF) only to a minor extent. In this paper, a feasible procedure is presented to set-up material models and estimate service life of cast iron cylinder heads under variable thermomechanical loading conditions by the use of CAE tools. In addition, the influence of thermal load and mechanical constraints on TMF life span is shown. A specimen model is used for parameter identification in material model set-up and a cylinder head model is used for correlation with cracking phenomena. Investigation of different thermomechanical load influences is conducted on the cylinder head model. The principal strain and energy based fatigue criteria are used in assessment of TMF lifetime for the cast iron family and material specific evaluation procedures are pointed out. The results highlight the importance of exact definitions of the boundary conditions and underline the sensitivity of TMF lifespan of cast iron cylinder heads with respect to the defined boundary conditions. Considering this sensitivity, an approach conforming to the engine development requirements is proposed. It is shown that both the crack location and fatigue lifetime are predicted with high accuracy.

Commentary by Dr. Valentin Fuster
2006;():615-624. doi:10.1115/ICES2006-1421.

There must be an end gap in the piston ring because of the need of mounting and compensation for diameter after the wear of ring. Richardson’ and many author’ studies have showed the effects of the end gap to blowby and oil consumption, especially in the presence of ring or liner wear. This problem has influenced the effective utilization of the fuel energy for many years. Moreover the ring will rotate in the working cycle of engine. Once the end gaps of two compression rings come to the site of superposition, the shortest passage of gas flow is formed and blowby will be increased. The deflection of crankpin and rotation of piston were calculated according to the analytical model based on the torque transmission theory of crankshaft. The positive and negative deflections of crankpin result in the reciprocating rotation of piston in the IC engine working cycle. The peak values of deflection and rotation are in the vicinity of crank angle position of deflagration. Because the clingy moment of compression rings are less than rotational resistance moment in a few section of crank angle, they are unable to keep synchronism with piston and the rotations opposite to piston occur. The rotation angle of the second compression ring is more than that of the first ring. The superposition of the end gaps of two compression rings comes about when they turn to the same angle position. Based on above study, the structure of one compression ring in piston system should be widely used, which is in favor of reduction of friction and engine weight, pushing forward the lightweight process, being useful to the decrease of fuel consumption and emission. The pressure of combustion gas will not remarkably descend in this structure. The problem of ring suspension and pressure release in the first ring land can be resolved. Two types of rings with complete seal and economizing energy design are showed for the structure of one ring, which will also avoid the increase of end gap after the rings are worn.

Topics: Friction , Pistons
Commentary by Dr. Valentin Fuster
2006;():625-632. doi:10.1115/ICES2006-1429.

Nowadays power trains face an increased customer expectation regarding noise and vibration. This trend requires the use of simulation tools beginning in early phases of the development process to ensure a ‘low noise engine’ at the end of the development process. Therefore FEV is using virtual development methods for NVH optimization of power trains for more than ten years. Fully parameterized simulation models allow the utilization in all phases of the development. Depending on the current design status of the development the detailing of the simulation models can be adapted. Based on comparative simple rigid body models in the beginning decisions regarding engine global data like bore, stroke cylinder distance and positioning of balancer shafts can be made. Later on, when more design parameters are fixed the depth of simulation models is increased until a fully flexible model allows the prediction of the NVH behavior of the complete power train. Such a simulation is performed using a hybrid simulation approach based on Finite-Element and Multi-Body simulation. The FE model of the power train is loaded with excitation forces calculated with MBS in order to calculate surface velocity. Based on these results further simulation allows the simulation of the airborne noise radiation. Here, the simulated airborne noise simulation is combined with the so called virtual interior noise simulation (VINS) developed by FEV. This method allows a target-oriented engine development with focus on an excellent vehicle interior noise behavior. Within the scope of this paper the above described procedure is applied to a development of a gasoline inline four cylinder engine. The simulation methods are verified in each step of the development.

Commentary by Dr. Valentin Fuster
2006;():633-643. doi:10.1115/ICES2006-1431.

The paper is a contribution to the discussion about a suitable future engine architecture, which has to cope with two contrary demands: the high mechanical and thermal loads in the engine and the need for a cost efficient, light weight engine design. Based on combustion related requirements of future emission legislation and expected performance requirements, a possible scenario of engine types and displacements is described. Features of a proposed bottom and top end concept — such as liner and crankcase concept, cylinder head bolt pattern, cylinder head concept, and suitable materials — are discussed, with the target to define a solution especially capable of high cylinder peak pressures and cost efficient at the same time.

Topics: Engines , Trucks
Commentary by Dr. Valentin Fuster
2006;():645-654. doi:10.1115/ICES2006-1435.

In bi-fuel engines, in which thermodynamic and mechanical design concepts are entirely based on gasoline mode, torque and power values are lower in natural gas mode than gasoline one. This problem is directly related to volumetric efficiency reduction in natural gas (NG) mode. Volumetric efficiency in natural gas is lower because of gaseous form of natural gas entering the engine and differences between thermo-chemical properties of natural gas and gasoline; e.g. stoichiometric air-fuel ratio and heat of vaporization. On the other hand, natural gas stoichiometric air-fuel ratio is generally greater than gasoline one and theoretically, more air should be supplied in NG mode. Although the effect of volumetric efficiency reduction is more important than another, both of them state the amount of charged air should be increased in NG mode to prevent power fall in this mode.

Commentary by Dr. Valentin Fuster
2006;():655-663. doi:10.1115/ICES2006-1438.

The cooling system of today’s engines has to fulfill certain requirements which results from fuel consumption reduction, efficiency increase and tightened emission legislation. Additionally the warm-up behavior especially of the passenger cabin and the resulting heater performance requirement leads to controversial targets. Beside these aspects the main function of the cooling system, the limitation of fluid and material temperatures has to be guaranteed. Following the trend that one engine will be integrated in a few different vehicles, with different vehicle-sided cooling system components, the cooling system development gets more and more complex with the result of an increase of the necessary testing effort to develop the system to series status. With focus on this trend, FEV has extended the well proven 1-dimensional thermal management simulation model to a complete closed loop development approach starting from the engine internal coolant flow distribution in the early engine concept phase up to the virtual testing model, which allows to simulate common vehicle test rows on the climate chamber or at hot ambient conditions at rod tests.

Topics: Cooling systems
Commentary by Dr. Valentin Fuster

Lubrication and Friction

2006;():665-676. doi:10.1115/ICES2006-1313.

An unsteady and two-dimensional thermohydrodynamic lubrication model in consideration of the ring movement and the heat flow from ring groove to piston ring was developed. The piston ring temperature in an internal combustion engine was analyzed by using the unsteady and two-dimensional form heat-conduction equation in consideration of axial movement of ring and heat flow from ring groove to ring during a cycle. The oil film temperature, oil film thickness and heat transfer between ring and liner surfaces were analyzed by using the calculated ring temperature taking into consideration cycle variation. The results are as follows. The heat flow rate around ring changes greatly with the ring movement and the ring sliding face temperature changes about 6 °C in a cycle. Then, the cycle mean temperature of ring sliding face becomes lower than the ring sliding face temperature calculated by the ring groove and liner surface temperatures under 2800 rpm and full load conditions. Therefore, the oil film viscosity is higher than that of the conventional viscosity model in which the viscosity was based on a constant ring sliding face temperature in a cycle. The oil film thickness predicted by the present method is thicker than that calculated by our previous method.

Commentary by Dr. Valentin Fuster
2006;():677-682. doi:10.1115/ICES2006-1322.

The state of piston lubrication-has been determined with reference to piston friction force measured by our developed single-cylinder supercharged small bore diesel engine with a boost pressure of up to 150kPa. The result is that the state of lubrication deteriorates markedly immediately before the compression top dead center due to increased boost pressure and immediately after the compression top dead center due to increased engine load. Moreover, the crankshaft offset, piston pin offset and multi-grade oil further deteriorate piston lubrication with a boost pressure.

Commentary by Dr. Valentin Fuster
2006;():683-692. doi:10.1115/ICES2006-1327.

A project to reduce frictional losses from natural gas engines is currently being carried out by a collaborative team from Waukesha Engine Dresser, Massachusetts Institute of Technology (MIT) and Colorado State University (CSU). This project is part of the Advanced Reciprocating Engine System (ARES) program led by the US Department of Energy. Previous papers have discussed the computational tools used to evaluate piston-ring/cylinder friction and described the effects of changing various ring pack parameters on engine friction. These computational tools were used to optimize the ring pack of a Waukesha VGF 18-liter engine, and this paper presents the experimental results obtained on the engine test bed. Measured reductions in friction mean effective pressure (FMEP) were observed with a low tension oil control ring (LTOCR) and a skewed barrel top ring (SBTR). A negative twist second ring (NTSR) was used to counteract the oil consumption increase due to the LTOCR. The LTOCR and SBTR each resulted in a ∼ 0.50% improvement in mechanical efficiency (ηmech ).

Commentary by Dr. Valentin Fuster
2006;():693-699. doi:10.1115/ICES2006-1328.

According to statistics, a large portion of used lubricants remain as potential hazards for the environment. Particularly, about 30 to 50% lubricant used in outboard marine engines is not burned completely and released into the water. As a result, consumers demand environmentally compatible lubricants due to concern about loss of mineral oil-based lubricants to the environment which can result in water contamination and pose a threat to animal and plant life. To prevent bioaccumulation of these materials in aquatic plants and animals, many agencies are considering regulations toward to biodegradable two-stroke outboard marine engines oil. Vegetable oils and ester oils are very suitable to develop “green lubricants”. Ester oils usually show excellent high temperature stability, low temperature fluidity, high viscosity index, very low volatility, good miscibility and biodegradability, but they are expensive and also produce many poisonous materials to environmental during produce process. Vegetable oils are biodegradable, nontoxic and renewable, moreover, their cost is reasonable compared to ester oils. Accordingly, vegetable oils are considered as potential candidates to replace conventional mineral oil-based lubricating oils, but the poor oxidative stability limits their utilization in large scale. Investigation of this work have found that proper percentage rapeseed oil can meet the requirements of biodegradable water-cooling two stroke engine oil, futhermore this two-cycle engine oil has good miscibility without need any miscibility-enhancing solvents. Research results indicate that two-cycle engine oil, which comprised rapeseed oil, ester oil and low viscosity hydrocracked oil as well as functional additives, exhibits good oxidative stability, easy biodegradability and good miscibility.

Commentary by Dr. Valentin Fuster
2006;():701-708. doi:10.1115/ICES2006-1340.

A simulation method was proposed to predict the slippage and transversal vibration of the accessory drive belt. To reproduce these phenomena, the accessory drive belt was represented by a section-by-section model in which the belt was replaced by a finite number of masses and springs using multi-body dynamics simulation. In this model, the belt was able to vibrate in both the direction of advance and the direction perpendicular to it, and a friction contact element was defined between the pulley and the belt. The coefficient of friction was made variable with respect to the slippage speed to enable stick and slippage to be predicted. This method allows for accurate simulation of the amount of belt slippage and the amplitude of transversal vibration, thus enabling the optimum belt layout to be determined at the design stage.

Topics: Simulation , Vibration , Belts
Commentary by Dr. Valentin Fuster
2006;():709-717. doi:10.1115/ICES2006-1349.

This paper presents a rigorous analysis of the elastohydrodynamic (EHD) lubrication of journal bearings in internal combustion (IC) engines. The approach treats a set of radial slider (plain journal) bearings as a system or a subsystem. Thus, they can be simulated simultaneously, and hence the system effect is included. The analysis considers both the elasticity and dynamics of the connected parts such as the cylinder block (or main bearing walls), crankshaft and conrod. Both local vibration and global motion of these elastic parts are modelled by a multi-body system (MBS) approach. Hence, the EHD behaviour of engine bearings is simulated in a realistic manner.

Commentary by Dr. Valentin Fuster
2006;():719-726. doi:10.1115/ICES2006-1356.

The oil aeration in a V-6 spark-ignition passenger car engine under motoring condition was measured by the X-ray absorption method in the speed range of 2000–6000 rpm. Measurements were made at different locations in the sump representing the state of the oil at (1) the pump inlet, (2) the head return and (3) the timing chain return. The aeration of the block return was estimated from these measurements. At a fixed engine speed, the aeration (in % volume of air) of the head return and the chain return were about the same, and they were approximately twice the value found in the block return. This distribution did not change with engine speed. When weighted by the flow rate, however, the block flow contributed to 55% of the aeration at the pump inlet; the total contribution of the head return and the chain return was 45% (36% from head return and 9% from chain return). Further aeration observations were made by comparing the cases with and without the oil sump windage tray in place. When the tray was removed, aeration at the pump inlet was found to increase by less than 30% for all speeds.

Commentary by Dr. Valentin Fuster
2006;():727-733. doi:10.1115/ICES2006-1374.

In order to reduce emissions and improve performance, engine designers have increased fuel injection pressures to improve fuel atomization. This leads to increased mechanical loads on the injection system requiring finer clearances that must be maintained between the plungers and bores in order to maintain diesel fuel injection quality. The reduction in diesel fuel sulfur levels required for meeting the emission legislations result in decreased fuel lubricity. In addition, due to unprecedented rise in the crude oil prices, biofuels are getting increasing attention worldwide. However, this also needs evaluation of the performance of the engine parts, especially the friction and wear in injection systems. In the present study we have investigated three titanium based physical vapour deposition (PVD) coatings (TiN, TiAlN, TiCN) used in two different environments namely mineral diesel and biodiesel, both containing 1% water. Commercially available thin-film ion-bonded coatings of above mentioned inter-metallic compounds, grown on steel balls were subjected to wear under stable load conditions in a custom build rotating disk wear tester. Some of the interesting findings of this experimental investigation may be instrumental in providing input for the development of hard, corrosion-resistant coatings for parts of Injector and fuel pumps of internal combustion engines using different fuels, especially biodiesel fuels.

Commentary by Dr. Valentin Fuster
2006;():735-740. doi:10.1115/ICES2006-1394.

Due to strict lead recycling regulations put upon discarded automobile engines, removing lead from new automotive engines became essential. Removing lead found in batteries from discarded automobiles is fairly straight-forward and inexpensive; however, much labor and cost is associated with removing lead containing engine bearings. Due to the relatively light loading applied to automotive gas engine bearings, lead-free aluminum alloys have been developed. Many experts predict that this lead-free trend will carry over to non-automotive bearings as well. Many of these non-automotive engines are run on diesel fuel and have much higher loading on the bearings. The current generation of lead-free aluminum alloys just cannot carry the loads required by these engines. Therefore, there has been efforts on developing lead-free copper based bearing alloys. This paper reviews one process that was undertaken to develop lead-free copper based alloy to be used in these highly loaded, non-automotive lead-free engine bearing types. This process included a fundamental understanding of the tribological role of lead in copper based bearing alloys, as well as a thorough performance screening of lead-free bearings types based on this lead-free lining and a comprehensive review of the test results. Also included in this paper are some future development plans in the world of lead-free copper based bearings alloys.

Topics: Bearings
Commentary by Dr. Valentin Fuster
2006;():741-748. doi:10.1115/ICES2006-1412.

A piston pin joint in a modern diesel engine operates under extreme loading and lubrication conditions. High load in combination with low relative surface velocities and limited lubrication makes this joint prone to localized wear and sudden failure. The analysis of this joint is also complicated with the pin motion, which defines surface velocities in the pin bore to pin and the pin to connecting rod interfaces. Therefore, the entire joint needs to be analyzed as a system of two bearings. Also, the hydrodynamic pressure in this joint at times may not be sufficient to balance the force applied to the joint and has to be complemented by the asperity contact pressure. The latter causes an additional deformation of the bearing. To address this problem a mixed lubrication model has been developed based on spectral EHD and nonlinear Greenwood and Trip statistical asperity contact formulation. Contact pressure distributions calculated with this model showed a pattern similar to the wear pattern in the bushing after production test. Analysis of the heat generated in the bearing was found to be a good indicator for the severity of the regime. Analysis of the bushing and piston bore with different geometry showed that asperity contact pressure and heat generated in the joint can be significantly reduced by modifications in local shape of the contacting surfaces.

Commentary by Dr. Valentin Fuster
2006;():749-759. doi:10.1115/ICES2006-1436.

The investigations and developments described in this article substantiate the potential for reduction of fuel consumption and the general feasibility of a roller bearing crank train in an internal combustion engine. An improvement of fuel consumption of 5.4% (NEDC) resulting from reduced friction was proven on the basis of a given 1.6L 4-cylinder plain bearing engine converted to roller bearings. By means of subsequent calculations and simulations, the parameters for optimisation of the engine acoustics and durability were identified. Based on these findings, an advanced test engine was set up. Measurements with this generation 2 roller bearing engine demonstrate the expected significant improvement of NVH behaviour. In parallel to the investigations with the generation 2 prototype which had to be a compromise with regard to robustness due to the requirement for a quickly realisable and feasible application, a completely new roller bearing bottom-end concept (generation 3) was developed. This new design meets the main requirements of optimal roller bearings while also taking the boundary conditions for high-volume production into account. The essential attributes of this generation 3 roller bearing crank train concept are the single-piece conrod and main-bearing pedestals which are threaded onto a crankshaft with detachable counterweights. The extra cost of EUR 50.- to 70.- for these roller bearing engine concepts is on a low level compared to the achieved reduction in fuel consumption.

Commentary by Dr. Valentin Fuster
2006;():761-768. doi:10.1115/ICES2006-1442.

Traditional designs, using cartridge filters for full-flow filtration, protect medium speed and high speed diesel engines from wear and keep the concentration of abrasive particles in the oil system down by collecting them out of the circulating oil flow. After several hundred running hours the filtration surface is saturated, the cartridges get exchanged and disposed. State of the art automatic filters protect the engines against wear with the same efficiency as the cartridge filters but the backflushing mechanism keeps the filtration surface clean and the lubrication circuit remains maintenance free. The lifetime of filter elements lasts during time before overhaul (TBO) of the engine itself and is at least 24,000 hrs. The job to discharge the particles out of the system is done by highly efficient centrifugal oil cleaners in by-pass operation which separate not only the particles retained by the automatic filter but also very fine solids like soot. Figure 1 shows an automatic filter in cooperation with two centrifugal oil cleaners build into the silhouette of the engine.

Commentary by Dr. Valentin Fuster

Instrumentation and Controls

2006;():769-779. doi:10.1115/ICES2006-1373.

The acoustic resonances in indicator passages are often modeled using either a Helmholtz or a so called organ pipe acoustical model. However, in practice these models often indicate natural frequencies which are too high. This paper proposes the Bergh and Tijdeman model [1] which is more accurate and which was originally developed for pressure measurements in turbomachinery. This paper presents the theoretical basis for the Berg / Tijdeman model and then uses it to explore signal distortion from a variety of indicator passage geometries. In order to validate the approach, a flush-mounted water-cooled Kistler reference transducer was used to measure accurate in-cylinder combustion data in an automotive Diesel engine. An additional sensor was recess mounted with passages of different geometries. The Bergh Tijdeman model was then applied to investigate the acoustic distortion of the indicator passages. The results show excellent agreement with the experimental data, which are much closer than using the Helmholtz or the organ pipe model. Further the Bergh and Tijdeman model is applied to complex indicator passage geometries with multiple cavities. Again, for comparison, a flush-mounted Kistler reference transducer was used to measure accurate in-cylinder combustion data in a large-bore natural gas engine. Three additional sensors were mounted using different indicator passage geometries. The engine was operated under base line and knocking combustion conditions. The Bergh Tijdeman model was then applied to model the acoustic distortion of the three indicator passages and again showed good agreement with the experimental data. Finally, the paper proposes simple rules for implementing indicator passages in large gas engines.

Commentary by Dr. Valentin Fuster
2006;():781-787. doi:10.1115/ICES2006-1381.

A new strategy based on a fuzzy multi-variable controller is proposed to regulate both the fresh airflow and the intake manifold pressure. The air system controller requires neither an internal model nor certain feed-forward maps. Taking only into account standard engine measurements, it is intrinsically robust and very easy to tune with respect to strategies proposed in literature. The results obtained with this controller are compared to those of current embedded controllers.

Commentary by Dr. Valentin Fuster
2006;():789-803. doi:10.1115/ICES2006-1411.

In internal combustion engines valve events and timings are among the most important parameters which have a major influence on the engine’s operation and volumetric efficiency. By using camless valvetrain strategy, improvement in fuel economy as well as an increase in entering air charge is found throughout the engine map with the largest benefits arising from low speed operating conditions. The system offers a continuously variable and independent control of virtually all parameters of valve motion. This permits optimization of valve events for each operating condition without any compromise. In this paper we describe a phenomenological model for an unthrottled operation of a camless intake process of spark-ignited (SI) engine. Initially the cylinder breathing dynamics is modeled and results are validated with experimental data of a conventional engine with cam-driven valve profile during unthrottled operation. Then we determine the most optimized intake valve profile in order to have the most volumetric efficiency and proper operation for each operating condition based on the existing model and using numerical techniques.

Commentary by Dr. Valentin Fuster
2006;():805-812. doi:10.1115/ICES2006-1425.

Gasoline engines can be affected, under certain operating conditions, by excessive heat flux through the combustion chamber walls, which can result in serious engine damage. Specific power and efficiency are influenced by factors such as compression ratio and spark advance regulation, that modify the combustion development over the crank angle: the trade-off between performance and the risk of irreversible damages is still a key factor in the design of both high-performance (racing) and low-consumption engines. New generation detection systems, especially based on ionization current technology, allow aggressive advance mapping and control, and future equipment, such as low-cost in-cylinder pressure transducers, will allow following that trend. Also HCCI (Homogeneous Charge Compression Ignition) engines need a sophisticated combustion monitoring methodology, since increasing BMEP levels in HCCI mode force the combustion to approach large heat-flux operation. Many methodologies can be found in the literature to recognize potentially dangerous combustions, usually based on the analysis of accelerometer, in-cylinder pressure or ionization current signals. Signals are sampled with high sample rates, than filtered, for a clear recognition of the phenomenon. Filtered signals can then be used to define damage-related indexes, by means of various types of mathematical operations. The indexes are then compared to pre-defined thresholds, for the diagnosis of dangerous combustion events. Thresholds setting is a challenging task, since most indexes are usually not intrinsically related to the damages caused by abnormal combustion events. Furthermore, the indexes values usually strongly depend on the engine operating conditions (speed and load), and thresholds must therefore vary with respect to speed and load. This paper presents a novel approach to the problem, whose objective is to define a damage-related and operating conditions-independent index. The methodology is based on the in-cylinder pressure signal, that is used for the Rate Of Heat Release evaluation. An onset condition is defined, for the dangerous phenomenon identification, and the mean thermal power released during the over-heating part of the combustion is considered as a damage intensity index. The paper shows that this parameter does not depend on the engine operating conditions, and it reaches similar values for different types of engine, under critical conditions. The index, however, must also take into account the malfunction frequency, since permanent damages are not caused by isolated events. The use of a moving average filter on the raw index is aimed at obtaining a stable output, more representative of the permanent damage risk and less influenced by the single combustion. These considerations lead to the definition of a heat flux index, strictly related to the damages caused by abnormal combustions. The diagnostic threshold value is constant over the entire operating range. Once the index is defined, it can be implemented on a control unit for real time diagnosis, or it can be used as a reference for the off-line calibration of other indexes. Examples are shown of other indexes trends and threshold calibrations over the engine operating range.

Topics: Heat flux
Commentary by Dr. Valentin Fuster
2006;():813-822. doi:10.1115/ICES2006-1427.

The recent OBD requirements enforce the misfire’s diagnosis and the isolation of the cylinder where the missing combustion took place. Most of the common-used techniques developed are based on the engine’s angular speed, that is derived by the signal usually measured with an inductive or Hall-effect sensor already used for the engine’s control. The presence of single or multiple misfires (several misfires within the same engine’s cycle) induces torsional vibration in the powertrain, requiring specific filtering of the diagnostic signal to avoid false alarms. This paper presents some preliminary results, related to a 4 cylinder 1.2 liter engine mounted on an eddy-current brake test bench, obtained by a new diagnosis technique based on two speed sensors, placed near the toothed wheels used respectively for the engine and current brake’s control. The signals coming from the two sensors, applied to an equation derived by a torsional model of the engine powertrain, allow to evaluate an index based on the difference between engine and brake’s torque that highlights the misfire presence. It will be shown that this index does not require any particular calibration procedure. Experimental tests, in which single and multiple misfires are induced in several operating conditions, show clearly the algorithm’s robustness in misfire detection, especially in multiple misfire tests, where the misfiring cylinders are exactly detected.

Commentary by Dr. Valentin Fuster

General

2006;():835-845. doi:10.1115/ICEF2005-1221.

A “High Efficiency Hybrid Cycle” (HEHC) thermodynamic cycle is explored. This four-stroke cycle borrows elements from Otto, Diesel, Atkinson, and Rankine cycles. Air is compressed into an isolated combustion chamber, allowing for true isochoric combustion, and extended duration for combustion to proceed until completion. Combustion products expand into a chamber with greater volume than intake. We provide details of a compact HEHC design implementation using rotary pistons and isolated rotating combustion chambers. Two Pistons simultaneously rotate and reciprocate and are held in position by two roller bearings. One Piston performs intake and compression, while the other performs exhaust and expansion. We predict a reduction of energy losses, moving part counts, weight and size over conventional engines.

Topics: Engines , Cycles
Commentary by Dr. Valentin Fuster

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