ASME Conference Presenter Attendance Policy and Archival Proceedings

2013;():V001T00A001. doi:10.1115/ICEF2013-NS1.

This online compilation of papers from the ASME 2013 Internal Combustion Engine Division Fall Technical Conference (ICEF2013) represents the archival version of the Conference Proceedings. According to ASME’s conference presenter attendance policy, if a paper is not presented at the Conference, the paper will not be published in the official archival Proceedings, which are registered with the Library of Congress and are submitted for abstracting and indexing. The paper also will not be published in The ASME Digital Collection and may not be cited as a published paper.

Commentary by Dr. Valentin Fuster

Large Bore Engines

2013;():V001T01A001. doi:10.1115/ICEF2013-19138.

The natural gas industry has long depended on large bore, two-stroke cycle, spark-ignited, gas-powered, reciprocating engines to move gas from the well to the pipeline and downstream. As regulations governing the pollutant emissions from these engines are tightened the industry is turning to the engine OEMs for a solution.

The challenge of further reducing engine emissions is not a new task to the industry. However, as the requirements placed on the engines are further restricted, the technology required to achieve these goals becomes more advanced, along with the required tools and technology to create it. New predictive tools have been created and have become more powerful and capable as computer software and hardware becomes more advanced, enabling engineers to create more complex designs and to do so quickly and at lower cost, all of which may not have been possible previously. This paper investigates methods used in designing the Ajax 2800 series, which is a large bore, two-stroke cycle, gas-powered, reciprocating engine and the improvements in emissions that resulted from the application of these methods.. Solutions to overcoming the challenges encountered during the process will also be presented.

Commentary by Dr. Valentin Fuster
2013;():V001T01A002. doi:10.1115/ICEF2013-19141.

Large bore, spark ignited, reciprocating, gas engines have been the workhorse of the pipeline industry for many years when it comes to transmission of gas. Recently, the US government has released an update to the NSPS and RICE NESHAP regulating emissions from many of these engines to [1]:

Display Formula1gbhp·hgbhp-hrNOX

Display Formula2gbhp·hCO

Display Formula0.7gbhp·hVOCs (Non-methane, non-ethane hydrocarbons)

This new rule leaves many of these legacy engines out of compliance with the standard. Because of this, engine operators are left with the choice of decommissioning these engines as they come due for compliance based retrofit or working with engine OEMs to implement an emissions reduction strategy.

For many years, the traditional methods and tools used for engine design were more than enough to create a successful engine. But with tightening restrictions and higher expectations for customers and the amount of improvement that can be extracted from design changes shrinking with every redesign, these methods by themselves are no longer sufficient. This paper will examine modern design methods and tools available to an engine designer as well as their integration with more traditional testing methods. A comparison of results for the redesigned COOPER BESSEMER® GMVH-6C3 will also be presented for analysis.

Commentary by Dr. Valentin Fuster
2013;():V001T01A003. doi:10.1115/ICEF2013-19158.

High exhaust emissions reduction efficiencies from a spark ignited (SI) internal combustion engine utilizing a Non Selective Catalyst Reduction (NSCR) catalyst system require complex fuel control strategies. The allowable equivalence ratio (Φ) operating range is very narrow where NSCR systems achieve high exhaust emission reduction efficiencies of multiple species. Current fuel control technologies utilizing lambda sensor feedback for natural gas spark ignited engines are reported to be unable to sustain these demands for extended operation periods and when transients are introduced. Lambda sensor accuracy is the critical issue with current fuel controllers. The goal of this project was to develop a minimization control algorithm utilizing an oxides of nitrogen (NOx) sensor installed downstream of the NSCR catalyst system for feedback air/fuel ratio control. Testing was performed on a 100kW rated natural gas Cummins-Onan generator set that was reconfigured to operate utilizing an electronic gas carburetor (EGC2) with lambda sensor feedback and high reduction efficiency NSCR catalyst system. The control algorithm was programmed utilizing a Labview interface that communicated with the electronic gas carburetor where the fuel trim adjustment was physically made. Improvement under steady state operation was observed. The system was also evaluated during load and fuel composition transients.

Commentary by Dr. Valentin Fuster
2013;():V001T01A004. doi:10.1115/ICEF2013-19229.

The selection of turbocharging systems for 8-cylinder marine diesel engines is difficult due to the existence of scavenge interference between cylinders. The constant pressure and pulse converter turbocharging systems have been used to eliminate the scavenge interference by applying large volume exhaust manifolds or grouped exhaust branches according to the firing order. But, the performance of constant pressure turbocharging system under low speed conditions of propulsion characteristics and transient conditions is poor, because of less available exhaust gas energy. The structure and arrangement of pulse converter turbocharging system is complex, meanwhile, and the performance at high speed and loads is not as good. In this paper, three new turbocharging systems, such as, MIXPC (mixed pulse converter) system, dual-turbocharger system (DTS) and controllable exhaust system (CES) were designed to improve the performance of a marine diesel engine. In the upstream part of MIXPC system, the separated small diameter branch pipes were used to isolate the exhaust gas interference. In the downstream part of MIXPC system, the single main pipe was connected with one entry turbocharger to improve the operation efficiency of the turbocharger. In the DTS, two one-entry turbochargers were used, one of which connected with 4 cylinders by two branch pipes and a mixer. The two cylinders with firing intervals of 270 crank angles were connected with one branch pipe. In the CES, a control valve was used to control the exhaust gas flow. The valve was opened at high speed and load conditions and closed at low speed and load conditions. The steady and transient performance of the three turbocharging systems was analyzed by simulation. The experimental studies were also carried out to compare the performance of the three turbocharging systems. The experimental results showed that the CES had the best fuel efficiency under low speed and load conditions, and the DTS had the best fuel efficiency under high speed and load conditions. Compared with the MIXPC system, the overall brake specific fuel consumption under propeller operating conditions was reduced by 11.3g/kWh with DTS and 5.3g/kWh with CES. But the uniformity of exhaust gas temperatures of cylinder heads was the best for MIXPC system. In general, the DTS was superior considering the structure simplicity and performance of the engine.

Commentary by Dr. Valentin Fuster

Advanced Combustion

2013;():V001T03A001. doi:10.1115/ICEF2013-19028.

Recent developments in emissions regulations, costs of conventional fuels, and new gas extraction drilling technologies have resulted in an increased emphasis in gaseous fueled spark ignited engine development. However the composition of gaseous fuels can vary greatly. Homogenous Charge Spark Ignited (HCSI) engine performance is heavily dependent upon fuel properties, and robust engine design to utilize gaseous fuels must accommodate these fuel property variances. Accurate prediction of fuel energy release characteristics and knock tendency is critical in the process of HCSI engine development.

Combustion characteristics, such as Laminar Flame Speed (LFS) and Autoignition Interval (AI), are used to characterize performance of various gaseous fuels in HCSI engine applications. Combustion duration is related to the LFS. The likelihood of Knock is related to the AI. Overall engine performance is estimated by appropriately incorporating these parameters into cycle simulation software.

Experimental data of LFS is often at low temperature and low pressure and thus does not represent the high temperature and pressure conditions typically prevalent in HCSI engine combustion chambers at the time of ignition. Lack of reliable LFS data at high temperature and pressures represents a major opportunity of development for better engine performance simulations [1].

In this paper, the commercially available chemical kinetics solver Chemkin Pro using an appropriate mechanism was employed to compute LFS and AI at typical HCSI engine in-cylinder conditions.

It is challenging to compute LFS at such extreme conditions mainly because of autoignition as a competing process.

This paper describes development of a robust methodology to compute LFS over a wide range of Temperature (up to 1300 K), Pressure (up to 250 bar), Relative Humidity, and Lambda for Methane. A regression for LFS with Pressure, Temperature, Lambda, and Relative Humidity as independent variables was generated for Methane. Methodology robustness was suggested with similar LFS calculations using other fuels. The form of the regression is similar for all of the fuels investigated.

Commentary by Dr. Valentin Fuster
2013;():V001T03A002. doi:10.1115/ICEF2013-19034.

The effects of hydrogen addition, diluent addition, injection pressure, chamber pressure, chamber temperature and turbulence intensity on methane–air partially premixed turbulent combustion have been studied experimentally using a constant volume combustion chamber (CVCC). The fuel–air mixture was ignited by centrally located electrodes at given spark delay times of 1, 5, 40, 75 and 110 milliseconds. Experiments were performed for a wide range of hydrogen volumetric fractions (0% to 40%), exhaust gas recirculation (EGR) volumetric fractions (0% to 25% as a diluent), injection pressures (30–90 bar), chamber pressures (1–3 bar), chamber temperatures (298–432 K) and overall equivalence ratios of 0.6, 0.8, and 1.0. Flame propagation images via the Sclieren/Shadowgraph technique, combustions characteristics via pressure derived parameters and pollutant concentrations were analyzed for each set of conditions. The results showed that peak pressure and maximum rate of pressure rise increased with the increase in chamber pressure and temperature while changing injection pressure had no considerable effect on pressure and maximum rate of pressure rise. The peak pressure and maximum rate of pressure rise increased while combustion duration decreased with simultaneous increase of hydrogen content. The lean burn limit of methane–air turbulent combustion was improved with hydrogen addition. Addition of EGR increased combustion instability and misfiring while decreasing the emission of nitrogen oxides (NOx).

Topics: Combustion , Methane
Commentary by Dr. Valentin Fuster
2013;():V001T03A003. doi:10.1115/ICEF2013-19037.

The use of close-coupled post injections of fuel is an in-cylinder soot-reduction technique that has much promise for high efficiency, heavy-duty diesel engines. Close-coupled post injections, short injections of fuel that occur soon after the end of the main fuel injection, have been known to reduce engine-out soot at a wide range of engine operating conditions, including variations in injection timing, EGR level, load, boost, and speed. While many studies have investigated the performance of post injections, the details of the mechanism by which soot is reduced remains unclear. In this study, we have measured the efficacy of post injections over a range of load conditions, at constant speed, boost, and rail pressure, in a heavy-duty, optically-accessible research diesel engine. Here, the base load is varied by changing the main-injection duration. Measurements of engine-out soot indicate that not only does the efficacy of a post injection decrease at higher engine loads, but that the range of post-injection durations over which soot reduction is achievable is limited at higher loads. Optical measurements, including natural luminescence of soot and planar laser-induced incandescence of soot, provide information about the spatio-temporal development of in-cylinder soot through the cycle in cases with and without post injections. The optical results indicate that the post injection behaves similarly at different loads, but that its relative efficacy decreases due to the increase in soot resulting from longer main-injection durations.

Topics: Engines , Stress , Diesel , Soot
Commentary by Dr. Valentin Fuster
2013;():V001T03A004. doi:10.1115/ICEF2013-19040.

Thermodynamics is the key discipline for determining and quantifying the elements of advanced engine designs which lead to high efficiency. In spite of its importance, thermodynamics is often not given full consideration in understanding engine operation for high efficiency. By fully utilizing the first and second laws of thermodynamics, detailed understanding of the engine features that provide for high efficiency may be determined. Of all the possible features that contribute to high efficiency, the results of this study show that highly diluted engines with high compression ratios provide the greatest impact for high efficiencies. Other important improvements which increase the efficiency include reduced heat losses, optimal combustion phasing, reduced friction, and reduced combustion duration. Thermodynamic quantification of these concepts is provided. For one comparison, the brake thermal efficiency increased from about 34% for the conventional engine to about 48% for the engine with one set of the above features. One aspect that contributes to these improvements is the importance of the ratio of specific heats (“gamma”). In addition, these design features often result in low emissions due to the low combustion temperatures.

Commentary by Dr. Valentin Fuster
2013;():V001T03A005. doi:10.1115/ICEF2013-19051.

Spark assist (SA) has been demonstrated to extend the operating limits of homogeneous charge compression ignition (HCCI) modes of engine operation. This experimental investigation focuses on the effects of 100% indolene and 70% indolene/30% ethanol blends on the ignition and combustion properties during SA HCCI operation. The spark assist effects are compared to baseline HCCI operation for each blend by varying spark timing at different fuel/air equivalence ratios ranging from ϕ = 0.4–0.5. High speed imaging is used to understand connections between spark initiated flame propagation and heat release rates. Ethanol generally improves engine performance with higher IMEPn and higher stability compared to 100% indolene. SA advances phasing within a range of ∼5 CAD at lower engine speeds (700 RPM) and ∼11 CAD at higher engine speeds (1200 RPM). SA does not affect heat release rates until immediately (within ∼5 CAD) prior to autoignition. Unlike previous SA HCCI studies of indolene fuel in the same engine, flames were not observed for all SA conditions.

Commentary by Dr. Valentin Fuster
2013;():V001T03A006. doi:10.1115/ICEF2013-19060.

Injection rate shaping is a method used to control the instantaneous mass flow rate of the fuel during an injection event. The rate at which the fuel is delivered affects the composition of the combustible mixture and its distribution in the combustion chamber, thereby has an impact on the combustion process in the diesel engine. This paper investigates the effects of five different types of injection rate shapes on diesel engine autoignition, combustion, and engine-out emission trends using a three-dimensional computational simulation approach. For this purpose, an n-heptane fuel model is utilized. Initially, a tophat rate-shape, characterized by the constant mass flow rate of the fuel, is assumed to represent the actual injection profile of an actual engine. Then, in order to develop sufficient confidence in the simulation predictions, this assumption together with the calibrated CFD models are validated by reproducing the cylinder gas pressure, the rate of heat release, and engine-out emissions trends for two sets of engine operating conditions. Later, using all the rate shapes the investigation is conducted for one test point considering two different cases of fuel injection: Case 1 - same SOI and duration of injection (DOI), and Case 2 - same combustion phasing and DOI.

The results obtained from the computational analysis show that the injection rate shape affects the autoignition, combustion, and emissions of a diesel engine. It is observed that the rate shapes, characterized by high injection rates at the beginning of the injection event, enhance the formation of negative temperature coefficient (NTC) regime. Therefore, the mole fractions of different species are determined during the NTC regime in order to examine the processes relevant to the formation of the NTC regimes for these rate shapes. Further, for the same SOI and DOI case, significant differences in the ignition delays between each rate shapes are observed. The maximum deviation of the ignition delay from the reference tophat is found to be 37%. Furthermore, the paper highlights the differences in the cylinder gas pressure, gas temperature, and rate of heat release due to different fuel delivery rates of different rate shapes. Finally, the comparison of the engine-out emissions for different rate shapes for both the cases of injection are presented and discussed in detail.

Commentary by Dr. Valentin Fuster
2013;():V001T03A007. doi:10.1115/ICEF2013-19066.

Eight different multi-hole fuel injectors with nominally the same exterior geometry (8-hole, 60 degree circular symmetric spray pattern) but different levels of development (Generation I and Generation II), length-to-diameter (L/D) ratios (1.4 to 2.4), and manufacturing processes (EDM vs. laser drilled) are compared in a spray-guided, spark-ignition direct injection (SG-SIDI) single-cylinder optical engine. In-cylinder pressure measurements and exhaust emission measurements quantified effects of different injectors on combustion and emissions. Crank-angle-resolved white-light spray imaging and simultaneous flame and soot visualization quantified variations in spray structure, combustion propagation, and soot formation and oxidation.

At a single operating condition (2000rpm, 95kPa inlet pressure, 90°C engine temperature, end of injection timing (EOI) @ 36 BTDC, spark advance (SA) @ 36 BTDC, 8.1mg/injection), all eight injectors have nearly the same IMEP (about 270kPa) and engine-out gaseous emissions. Experiments show that laser drilled injectors with lower L/D ratios (L/D = 1.4–2.0) have a totally collapsed fuel spray structure, a more penetrating liquid spray with severe fuel impingement on the piston, and rapidly-forming soot deposits on the piston. The collapsed, more compact fuel spray vaporized more slowly and the resulting rich zones led to strong soot luminosity. In contrast, the laser drilled injector with the highest L/D ratio (2.4) and the two EDM injectors (Generation I and Generation II with L/D = 2.0) show 8 distinct spray plumes, less fuel impingement, and much less soot emission intensity. Image analysis tools developed in Matlab were used to characterize the flame propagation and soot formation processes.

Commentary by Dr. Valentin Fuster
2013;():V001T03A008. doi:10.1115/ICEF2013-19068.

An algorithm for determining the four tuning parameters in a double-Wiebe description of the combustion process in spark-assisted compression ignition engines is presented where the novelty is that the tuning problem is posed as a weighted linear least-squares problem. The approach is applied and shown to describe well an extensive data set from a light-duty gasoline engine for various engine speeds and loads. Correlations are suggested for the four parameters based on the results, which illustrates how the double-Wiebe approach can also be utilized in predictive simulation. The effectiveness of the methodology is quantified by the accuracy for describing and predicting the heat release rate as well as predicting the cylinder pressure. The root-mean square errors between the measured and predicted cylinder pressures are 1 bar or less, which corresponds to 2% or less of the peak cylinder pressure.

Commentary by Dr. Valentin Fuster
2013;():V001T03A009. doi:10.1115/ICEF2013-19069.

A pseudo-multi-zone phenomenological model has been created with the ultimate goal of supporting efforts to enable broader commercialization of low temperature combustion modes in diesel engines. The benefits of low temperature combustion are the simultaneous reduction in soot and nitric oxide emissions and increased engine efficiency if combustion is properly controlled. Determining what qualifies as low temperature combustion for any given engine can be difficult without expensive emissions analysis equipment. This determination can be made off-line using computer models or through factory calibration procedures. This process could potentially be simplified if a real-time prediction model could be implemented to run for any engine platform — this is the motivation for this study.

The major benefit of this model is the ability for it to predict the combustion trajectory, i.e. local temperature and equivalence ratio in the burning zones. The model successfully captures all the expected trends based on the experimental data and even highlights an opportunity for simply using the average reaction temperature and equivalence ratio as an indicator of emissions levels alone — without solving formation sub-models.

This general type of modeling effort is not new, but a major effort was made to minimize the calculation duration to enable implementation as an input to real-time next-cycle engine controller Instead of simply using the predicted engine out soot and NOx levels, control decisions could be made based on the trajectory. This has the potential to save large amounts of calibration time because with minor tuning (the model has only one automatically determined constant) it is hoped that the control algorithm would be generally applicable.

Commentary by Dr. Valentin Fuster
2013;():V001T03A010. doi:10.1115/ICEF2013-19089.

Experiments under two intake air swirl levels (swirl ratio of 0.55 and 5.68) were conducted to investigate the early flame development of combustion in a single-cylinder spark-ignition direct-injection engine. The engine was equipped with a quartz insert in the piston which provided an optical access to its cylinder through the piston. The crank angle resolved combustion images through the piston window and in-cylinder pressure measurements of 250 cycles were recorded simultaneously for both swirl levels at a specified engine speed and low load condition. The early development, size and spatial characteristics extracted from the flame images were analyzed as a function of crank angle degrees after the ignition. Experimental results revealed that the early flame development was strongly influenced by the highly directed swirl motion of intake-air into the combustion cylinder. The location of the start of flame kernel relative to the spark plug position also changed intermittently at different swirl levels. While the structure of the early flame was found to be similar for both swirl levels, the starting location of the flame showed vast difference in how the flame progressed. In general, the flame kernel was formed 2 crank-angle degrees after spark timing for the high swirl level, which was 4 crank-angle degrees earlier than that of low swirl case. For low swirl flow, the early combustion showed more cycle-to-cycle variation in terms of both flame size and centroid location. It was quantitatively shown that increasing swirl ratio from 0.55 to 5.68 could reduce the cycle-to-cycle variation of early flame structure, resulting in about 3 to 4 crank-angle degrees advance of peak pressure location and 1% improvement for COV of IMEP.

Topics: Engines , Flames , Ignition
Commentary by Dr. Valentin Fuster
2013;():V001T03A011. doi:10.1115/ICEF2013-19095.

Most studies comparing diesel/gasoline dual-fuel operation and single-fuel diesel operation in diesel engines center on time-averaged results. It seems few studies discuss differences in cyclic variability. Motivated by this, the present study evaluates the cyclic variability of combustion in both dual-fuel and single-fuel operations of a diesel engine.

Steady-state tests were done on a medium duty diesel engine with conventional direct injection timings of diesel fuel into the cylinder at one speed and three loads. In addition to single-fuel (diesel) operation, dual-fuel (gasoline and diesel) operation was studied at increasing levels of gasoline fraction. Gasoline fuel is introduced via a fuel injector at a single location prior to the intake manifold (and EGR mixing location). Crank-angle resolved data including in-cylinder pressure and heat release rate obtained for around 150 consecutive cycles are used to assess cyclic variability.

The sources of cyclic variability, namely the factors causing cyclic variability or influencing its magnitude, especially those related to cylinder charge amount and mixture preparation, are analyzed. Fuel spray penetration and cyclic variability of cylinder charging, overall A/F ratio, and fuel injection timing, tend to increase cyclic variability of combustion in dual-fuel operation. On the other hand, fuel type and fuel spray droplet size tend to increase cyclic variability in single-fuel operation.

The cyclic variability in dual-fuel operation in this study is more serious than that in single-fuel operation, in terms of magnitude, indicated by metrics chosen to quantify it. Most measures of cyclic variability increase consistently with increasing gasoline fraction. Variations of gasoline amount and possibly gasoline low temperature heat release cause higher combustion variation in dual-fuel operation primarily by affecting premixed burning.

Statistical methods such as probability density function, autocorrelation coefficient, return map, and symbol sequence statistics methods are used to check determinism. In general, the parameters studied do not show strong determinism, which suggests other parameters must be identified to establish determinism or the system is inherently stochastic. Regardless, dominant sequences and optimal sequence lengths can be identified.

Commentary by Dr. Valentin Fuster
2013;():V001T03A012. doi:10.1115/ICEF2013-19098.

The purpose of this study was to characterize combustion behavior for n-heptane using experimental measurements in a direct-injection constant-volume combustion chamber (CVCC) to validate chemical-kinetic mechanisms. This work is focused on compression-ignition (i.e., diesel) combustion, primarily because mechanisms for larger-chain diesel-relevant species are not well developed and require significant attention.

The CVCC used in this work can be pressurized and heated to create engine-relevant conditions that enable study of autoignition behavior. In addition, the chamber is equipped with a high-pressure, common-rail diesel injector, making the study of autoignition and combustion in this system highly relevant to modern diesel engines. By varying injection pressure and duration, it is possible to control global equivalence ratio as well. Chamber pressure during injection and combustion is measured using a piezoelectric transducer, and can be subsequently used to infer heat-release rates. Experimental measurements for n-heptane mostly displayed expected trends. As initial chamber pressure increased, ignition delay decreased and peak pressure increased. As injection duration increased, ignition delay decreased due to faster ignition of richer mixtures, and peak pressure increased due to higher total heat release. The effect of temperature on ignition delay, however, was more complex and suggested some amount of NTC (negative temperature coefficient) behavior. For all conditions, heat-release rates indicated entirely premixed combustion with no hint of mixing-controlled combustion.

Experimental data were compared with results from CHEMKIN-PRO simulations. The model simulated zero-dimensional combustion using a detailed n-heptane mechanism developed at Lawrence Livermore National Laboratory. These computations were used to infer local equivalence ratio information, based on equivalence ratio required in the model to match experimental ignition delay. For most test cases, the model required an equivalence ratio that was at least ∼2× richer than the global value. In addition, equivalence ratios in the model ranged a full order of magnitude, from ∼0.6 to 6, suggesting that local mixture equivalence ratios varied considerably as experimental conditions were varied. Results suggest that improved models that include details of spray physics are required in order to properly predict local equivalence ratios and resulting autoignition characteristics.

Commentary by Dr. Valentin Fuster
2013;():V001T03A013. doi:10.1115/ICEF2013-19099.

In the quest for high efficiency IC engine operation, spark assisted compression ignition (SACI) can fill the gap between homogeneous charge compression ignition (HCCI) operation at low load and spark ignited (SI) operation at high load. SACI combustion utilizes a combination of flame propagation and auto-ignition to achieve ignition when unburned temperatures are too low for reliable auto-ignition and the mixture is too dilute for flame propagation with sufficient speed. Stoichiometric SACI combustion with cooled external exhaust gas recirculation (EGR) offers improved thermal efficiency compared to stoichiometric SI operation. It also reduces combustion temperatures and therefore NOx emissions, while still allowing for the use of a three-way catalyst (TWC).

This study investigates NOx spikes that can occur during transitions between different SACI operating points as a result of system time lags or mixture deviation from stoichiometry. Load transitions at various stoichiometric SACI operating points are investigated and NOx emissions before and after the TWC are reported. Significant engine-out NOx spikes are observed. A 1200 ppm NOx spike occurs during a load increase from 3 to 6 bar BMEP at 1800 rpm in 2 cycles (0.13 seconds), which is representative of a faster load change in the FTP-75 drive cycle. Observed NOx spikes are attributed to a time lag in external EGR during the transitions. NOx emissions after the TWC are reduced to below 50 ppm, indicating that NOx emissions during these transients can be handled effectively by a TWC.

Commentary by Dr. Valentin Fuster
2013;():V001T03A014. doi:10.1115/ICEF2013-19102.

The focus of this work was to develop a continuous-flow vessel with extensive optical access for characterization of engine-relevant fuel-injection and spray processes. The spray chamber was designed for non-reacting experiments at pressures up to 1380 kPa (200 psi) and temperatures up to 200°C. Continuous flow of inert “sweep gas” enables acquisition of large statistical data samples and thus potentially enables characterization of stochastic spray processes. A custom flange was designed to hold a common-rail diesel injector, with significant flexibility to accommodate other injectors and injector types in the future. This flexibility, combined with the continuous flow through the chamber, may enable studies of gas-turbine direct-injection spray processes in the future. Overall, the user can control and vary: injection duration, injection pressure, sweep-gas temperature, sweep-gas pressure, and sweep-gas flow rate. The user also can control frequency of replicate injections.

There are four flat windows installed orthogonally on the vessel for optical access. Optical data, at present, include global spray properties such as liquid-phase fuel penetration and cone angle. These measurements are made using a high-speed spray-visualization system (up to 100 kHz) consisting of a fast-pulsed LED (light emitting diode) source and a high-speed camera. Experimental control and data acquisition have been set up and synchronized using custom LabVIEW programs. The culmination of this development effort was an initial demonstration experiment to capture high-speed spray-visualization movies of n-heptane injections to determine liquid-phase fuel penetration length (i.e., liquid length) and spray cone angle. In this initial experiment, fuel-injection pressure was ∼120 MPa (1200 bar) and the injection command-pulse duration was 800 μs. At room conditions, liquid length and nominal spray cone angle were ∼170 mm and ∼14.5°, respectively. In contrast, with air flow in the chamber at 100 psi and 100°C, liquid length was considerably shorter at ∼92 mm and spray cone angle was wider at ∼16.5°. Future experiments will include the continuation of these measurements for a wider range of conditions and fuels, extension of high-speed imaging to vapor-phase fuel penetration using schlieren imaging techniques, and detailed characterization of spray properties near the injector nozzle and near the liquid length.

Commentary by Dr. Valentin Fuster
2013;():V001T03A015. doi:10.1115/ICEF2013-19104.

High-speed photography, two-color method, and thermodynamic analysis have been used to improve understanding of the influence of pilot injection timing on diesel combustion in an optical engine equipped with an electronically-controlled, common rail, high-pressure fuel injection system. The tests were performed at four different pilot injection timings (30 degree, 25 degree, 20 degree, and 15 degree CA BTDC) with the same main injection timing (5 degree CA BTDC), and under 100MPa injection pressure. The engine speed was selected at 1200 rev/min, and the whole injection mass was fixed as 27.4 mg/stroke. The experimental results showed that the pilot injection timing had a strong influence on ignition delay and combustion duration: advancing the pilot injection timing turned to prolong the ignition delay and shorten the combustion duration. The combustion images indicated that when pilot injection was advanced, the area of luminous flames decreased. The results of two-color method suggested pilot injection timing significantly impacted both the soot temperature distribution and soot concentration (KL factor) within the combustion chamber. 30 degree CA BTDC was the optimal pilot injection timing for in-cylinder soot reduction.

Topics: Combustion , Engines , Diesel
Commentary by Dr. Valentin Fuster
2013;():V001T03A016. doi:10.1115/ICEF2013-19108.

Diesel-ignited gasoline dual fuel combustion experiments were performed in a single-cylinder research engine (SCRE), outfitted with a common-rail diesel injection system and a stand-alone engine controller. Gasoline was injected in the intake port using a port-fuel injector. The engine was operated at a constant speed of 1500 rev/min, a constant load of 5.2 bar IMEP, and a constant gasoline energy substitution of 80%. Parameters such as diesel injection timing (SOI), diesel injection pressure, and boost pressure were varied to quantify their impact on engine performance and engine-out ISNOx, ISHC, ISCO, and smoke emissions. Advancing SOI from 30 DBTDC to 60 DBTDC reduced ISNOx from 14 g/kWhr to less than 0.1 g/kWhr; further advancement of SOI did not yield significant ISNOx reduction. A fundamental change was observed from heterogeneous combustion at 30 DBTDC to “premixed enough” combustion at 50–80 DBTDC and finally to well-mixed diesel-assisted gasoline HCCI-like combustion at 170 DBTDC. Smoke emissions were less than 0.1 FSN at all SOIs, while ISHC and ISCO were in the range of 8–20 g/kWhr, with the earliest SOIs yielding very high values. Indicated fuel conversion efficiencies were ∼ 40–42.5%. An injection pressure sweep from 200 to 1300 bar at 50 DBTDC SOI and 1.5 bar intake boost showed that very low injection pressures lead to more heterogeneous combustion and higher ISNOx and ISCO emissions, while smoke and ISHC emissions remained unaffected. A boost pressure sweep from 1.1 to 1.8 bar at 50 DBTDC SOI and 500 bar rail pressure showed very rapid combustion for the lowest boost conditions, leading to high pressure rise rates, higher ISNOx emissions, and lower ISCO emissions, while smoke and ISHC emissions remained unaffected by boost pressure variations.

Commentary by Dr. Valentin Fuster
2013;():V001T03A017. doi:10.1115/ICEF2013-19110.

This paper presents an experimental analysis of diesel-ignited propane dual fuel low temperature combustion (LTC) based on performance, emissions, and in-cylinder combustion data from a modern, heavy-duty diesel engine. The engine used for these experiments was a 12.9-liter, six-cylinder, direct injection heavy-duty diesel engine with electronic unit diesel injection pumps, a variable geometry turbocharger, and cooled exhaust gas recirculation (EGR). The experiments were performed with gaseous propane (the primary fuel) fumigated upstream of the turbocharger and diesel (the pilot fuel) injected directly into the cylinders. Results are presented for a range of diesel injection timings (SOIs) from 10° BTDC to 50° BTDC at a brake mean effective pressure (BMEP) of 5 bar and a constant engine speed of 1500 RPM. The effects of SOI, percent energy substitution (PES) of propane (i.e., replacement of diesel fuel energy with propane), intake boost pressure, and cooled EGR on the dual fuel LTC process were investigated. The approach was to determine the effects of SOI while maximizing the PES of propane. Dual fuel LTC was achieved with very early SOIs (e.g., 50° BTDC) coupled with high propane PES (> 84%), which yielded near-zero NOx (< 0.02 g/kW-hr) and very low smoke emissions (< 0.1 FSN). Increasing the propane PES beyond 84% at the SOI of 50° BTDC yielded a high COV of IMEP due to retarded combustion phasing (CA50). Intake boost pressures were increased and EGR rates were decreased to minimize the COV, allowing higher propane PES (∼ 93%); however, lower fuel conversion efficiencies (FCE) and higher HC and CO emissions were observed.

Commentary by Dr. Valentin Fuster
2013;():V001T03A018. doi:10.1115/ICEF2013-19125.

Advanced combustion techniques have shown promise for achieving high thermal efficiency with simultaneous reductions in oxides of nitrogen (NOx) and particulate matter (PM) emissions. Many advanced combustion studies have used some form of noise-related metric to constrain engine operation, whether it be cylinder pressure rise rate, combustion noise, or ringing intensity. As the development of advanced combustion techniques progresses towards production-viable concepts, combustion noise is anticipated to be of the upmost concern for consumer acceptability. This study compares the noise metrics of cylinder pressure rise rate with combustion noise as measured by an AVL combustion noise meter over a wide range of engine operation conditions with reactivity controlled compression ignition on a light-duty multi-cylinder diesel engine modified to allow for direct injection of diesel fuel and port fuel injection of gasoline. Key parameters affecting noise metrics are engine load, speed, and the amount of boost. The trade-offs between high efficiency, low NOX emissions, and combustion noise were also explored. Additionally, the combustion noise algorithm integrated into the Drivven combustion analysis toolkit is compared to cylinder pressure rise rate and combustion noise as measured with a combustion noise meter. It is shown that the combustion noise of the multi-cylinder reactivity controlled compression ignition map can approach 100 dB while keeping the maximum pressure rise under 100 kPa/CAD.

Commentary by Dr. Valentin Fuster
2013;():V001T03A019. doi:10.1115/ICEF2013-19140.

Dual-fuel reactivity controlled compression ignition (RCCI) combustion has shown high thermal efficiency and superior controllability with low NOx and soot emissions. However, as in other low temperature (LTC) combustion strategies, the combustion control using low exhaust gas recirculation (EGR) or high compression ratio at high load conditions has been a challenge. The objective of this work was to examine the efficacy of using dual direct injectors for combustion phasing control of high load RCCI combustion. The present computational work demonstrates that 21bar gross indicated mean effective pressure (IMEP) RCCI is achievable using dual direct injection. The simulations were done using the KIVA3V-Release 2 code with a discrete multi-component fuel evaporation model, coupled with sparse analytical Jacobian solver for describing the chemistry of the two fuels (iso-octane and n-heptane). In order to identify an optimum injection strategy a Nondominated Sorting Genetic Algorithm II (NSGA II), which is a multi-objective genetic algorithm, was used. The goal of the optimization was to find injection timings and mass splits among the multiple injections that simultaneously minimize the six objectives: soot, nitrogen oxide (NOx), carbon monoxide (CO), unburned hydrocarbon (UHC), indicated specific fuel consumption (ISFC), and ringing intensity. The simulations were performed for a 2.44 liter, heavy-duty engine with 15:1 compression ratio. The speed was 1800 rev/min and the intake valve closure (IVC) conditions were maintained at 3.42bar, 90°C, and 46% EGR. The resulting optimum condition has 12.6bar/deg peak pressure rise rate, 158bar maximum pressure, and 48.7% gross indicated thermal efficiency. NOx, CO, and soot emissions are very low.

Topics: Combustion , Fuels , Stress
Commentary by Dr. Valentin Fuster
2013;():V001T03A020. doi:10.1115/ICEF2013-19155.

The spray combustion of diesel fuel under conditions of very low ambient O2 concentrations was examined in this study. The detailed combustion characteristics were evaluated using two different sets of experimental apparatuses. A high-temperature, high-pressure combustion vessel with dual observation windows was employed to visualize the spray flame. The sequential images were obtained by using a high-speed color video camera and were analyzed using the two color method to quantify the temporal variation of the two dimensional distribution of soot temperature and KL factor. Both the ambient O2 concentration and the CO2 mixing ratio were varied as experimental parameters. A second constant volume vessel with a smaller internal volume was also employed as an experimental apparatus to conduct analyses of heat release rates based on temporal variations of pressure.

Based on a series of systematic experiments, we confirmed that O2 concentration is the primary factor affecting both the ignition delay and combustion period, while the level of CO2 mixing has little effect. Decreasing O2 concentrations were associated with delays in the appearance of the luminous flame following the onset of light emission from OH radicals. The heat release rate study showed the possibility of the existence of endothermic reactions during this period. The flame temperature was observed to decrease as the O2 concentration decreased and as the CO2 ratio increased, resulting in reduced NOx emissions. The amount of soot inside the flame initially increased with decreasing O2 concentrations, but then decreased starting at an O2 concentration of approximately 11%, such that minimal amounts of soot were generated at very low O2 levels. Both visual observations and emissions measurements confirmed that the simultaneous reduction of NOx, soot and CO can be successfully achieved under very low O2 concentrations.

Topics: Combustion , Sprays , Diesel
Commentary by Dr. Valentin Fuster
2013;():V001T03A021. doi:10.1115/ICEF2013-19168.

A systems approach is implemented to fully optimize the overall performance of a gasoline SIDI two-valve “small block” engine. The objective is to maximize fuel economy while achieving significant improvements in idle stability, cold-start emissions, and torque and power performance relative a baseline port-fuel-injected (PFI) engine. The scope includes the optimization of the fuel injector, piston, cylinder head, cams, in-cylinder charge motion, and the intake-manifold. The results show that the SIDI engine provides the potential to achieve 6.5% better fuel economy; a result of higher efficiency when implementing a higher geometric compression ratio and significantly better combustion performance. A multiple fuel-injection strategy is examined to provide lower HC emissions at a representative cold-start operating condition. The engine’s idle stability is improved by a factor of three; the individual contributions from a better combustion system design and from multiple fuel injections are identified. The new SIDI engine concept demonstrated significantly better wide-open-throttle (WOT) performance, including up to 10% higher torque and 6% more power when using premium fuel. This document further demonstrates the performance sensitivity to engine design variables while emphasizing the importance of using a systems approach to achieve optimized performance for the direct-injection engine technology.

Commentary by Dr. Valentin Fuster
2013;():V001T03A022. doi:10.1115/ICEF2013-19170.

Advanced technologies combining turbocharging, downsizing, direct injection, and cooled EGR are being intensively investigated in order to significantly improve the fuel economy of spark-ignition (SI) gasoline engines. To avoid the occurrence of knock and to improve the thermal efficiency, a significant fraction of EGR is often used. Due to the significant fraction of EGR, the ignition source needs to be enhanced to ensure high combustion stability. In addition to advanced spark-based solutions, diesel micro-pilot (DMP) technology has been proposed in recent years where the diesel fuel replaces the spark-plug as the ignition source.

This paper studies the combustion characteristics of a diesel micro pilot ignited gasoline engine, employing direct injection of gasoline and diesel as well as turbocharging and cooled EGR. A multi-dimensional CFD code with a chemical kinetic calculation capability was extensively validated across the engine speed and load range in a previous study [1]. This paper explores the influence of a number of parameters on DMP combustion behavior, including: diesel pilot mass fraction, start of injection (SOI), DMP injection strategy, as well as EGR rate, air/fuel ratio, and DI gasoline/air mixture inhomogeneity.

Besides, the comparison of DMP ignited combustion with traditional spark ignited combustion is also made in terms of EGR tolerance, lean burn limit, and DI gasoline air mixture inhomogeneity. Finally, numerical simulations aimed at optimizing both gasoline and diesel injection parameters, as well as EGR rate in order to enhance the engine performance in the DMP combustion mode, are discussed.

Commentary by Dr. Valentin Fuster
2013;():V001T03A023. doi:10.1115/ICEF2013-19174.

This paper reviews the technical approach and reports on the results of ASPEN Plus® modeling of two patented approaches for integrating a gas turbine with reciprocating internal combustion engine for lower emissions and higher efficiency power generation. In one approach, a partial oxidation gas turbine (POGT) is located in the 1st stage, and the H2-rich fuel gas from POGT exhaust is cooled and fed as main fuel to the second stage, ICE. In this case, the ICE operates in lean combustion mode. In the second approach, an ICE operates in partial oxidation mode (POX) in the 1st stage. The exhaust from the POX-ICE (a low BTU fuel gas) is combusted to drive a conventional GT in the 2nd stage of the integrated system. In both versions, use of staged reheat combustion leads to predictions of higher efficiency and lower emissions compared to independently providing the same amount of fuel to separate GT and ICE where both are configured for lean combustion. The POGT and GT analyzed in the integrated systems are based upon building them from commercially available turbocharger components (turbo-compressor and turbo-expander).

Modeling results with assumptions predicting 50–52% LHV fuel to power system efficiency and supporting NOx < 9 ppm for gaseous fuels are presented for these GT-ICE integrated systems.

Commentary by Dr. Valentin Fuster
2013;():V001T03A024. doi:10.1115/ICEF2013-19176.

Spark Assisted Compression Ignition (SACI) is a combustion mode that may offer significant efficiency improvements compared to conventional spark-ignited combustion systems. Unfortunately, SACI is constrained to a relatively narrow range of dilution levels and top dead center temperatures. Both positive valve overlap (PVO) and negative valve overlap (NVO) strategies may be utilized to attain these conditions at low and intermediate engine loads.

The current work compares 1D thermodynamic simulations of PVO valving strategies and a baseline NVO strategy in a downsized boosted automotive engine with variable valve timing capability. As future downsized boosted engines may employ multiple combustion modes, the goal of this work is the definition of valving strategies appropriate for SACI combustion at low to moderate loads and SI combustion at moderate to high loads for an engine with fixed camshaft profiles. PVO durations, valve opening timings and peak lifts are investigated at low to moderate loads and are compared to a baseline NVO configuration in order to assess valving strategies appropriate for multi-mode combustion operation. A valvetrain kinematic model is used to translate the desired valve lift profiles into camshaft profiles, while a kinematic analysis is used to calculate piston to valve clearances and to define the practical limits of the PVO strategies. The NVO and PVO strategies are also compared to throttled SI operation at part load to assess the overall efficiency benefit of operating under the thermodynamic conditions of the SACI combustion regime.

While the results of this study are engine specific, there are several camshaft profiles that are appropriate for the use of PVO rebreathing type valve events. For the range of PVO valve events examined and taking into consideration piston to valve interference, the use of high exhaust and low intake lifts with early exhaust valve opening timing and long PVO durations enables high levels of internal EGR with relatively low pumping losses.

Commentary by Dr. Valentin Fuster
2013;():V001T03A025. doi:10.1115/ICEF2013-19195.

The dual fuel reactivity controlled compression ignition (RCCI) concept has been successfully demonstrated to be a promising, more controllable, high efficiency and cleaner combustion mode. A multi-dimensional computational fluid dynamics (CFD) code coupled with detailed chemistry, KIVA-CHEMKIN, was applied to develop a strategy for phasing control during load transitions. Steady-state operating points at 1500 rev/min were calibrated from 0 to 5 bar brake mean effective pressure (BMEP). The load transitions considered in this study included a load-up and a load-down load change transient between 1 bar and 4 bar BMEP at 1500 rev/min. The experimental results showed that during the load transitions, the diesel injection timing responded in 2 cycles while around 5 cycles were needed for the diesel common-rail pressure to reach the target value. However, the intake manifold pressure lagged behind the pedal change for about 50 cycles due to the slower response of the turbocharger.

The effect of these transients on RCCI engine combustion phasing was studied. The CFD model was first validated against steady-state experimental data at 1 bar and 4 bar BMEP. Then the model was used to develop strategies for phasing control by changing the direct port fuel injection (PFI) amount during load transitions. Specific engine operating cycles during the load transitions (6 cycles for the load-up transition and 7 cycles for the load-down transition) were selected based on the change of intake manifold pressure to represent the transition processes. Each cycle was studied separately to find the correct PFI to diesel fuel ratio for the desired CA50 (the crank angle at which 50 % of total heat release occurs). The simulation results showed that CA50 was delayed by 7 to 15 degrees for the load-up transition and advanced by around 5 degrees during the load-down transition if the pre-calibrated steady-state PFI table was used. By decreasing the PFI ratio by 10 % to 15 % during the load-up transition and increasing the PFI ratio by around 40 % during the load-down transition, the CA50 could be controlled at a reasonable value during transitions. The control strategy can be used for closed-loop control during engine transient operating conditions. Combustion and emission results during load transitions are also discussed.

Commentary by Dr. Valentin Fuster
2013;():V001T03A026. doi:10.1115/ICEF2013-19203.

Homogeneous Charge Compression Ignition (HCCI) is a low temperature combustion strategy that simultaneously improves fuel efficiency and lowers engine-out NOx emissions. Unfortunately, broad usage of HCCI is hampered by combustion instabilities and a limited operation envelope. To help understand these limitations, this paper treats individual cylinders in a production four-cylinder engine as dynamical systems that iterate CA90 (the crank angle where 90% of net heat release is achieved) cycle-to-cycle as the engine operates in an unboosted, negative valve overlap HCCI combustion mode. This approach is shown to provide qualitative understanding of the stability limit bifurcation behavior, while also enabling quantitative cycle-to-cycle predictions of combustion phasing across a wide variety of transient and steady-state conditions, right up to complete misfire.

Commentary by Dr. Valentin Fuster
2013;():V001T03A027. doi:10.1115/ICEF2013-19209.

Dual-fuel reactivity-controlled compression ignition (RCCI) combustion using port injection of a less reactive fuel and early-cycle direct injection of a more reactive fuel has been shown to yield both high thermal efficiency and low NOX and soot emissions over a wide engine operating range. Conventional and alternative fuels such as gasoline, natural gas and E85 as the lower reactivity fuel in RCCI have been studied by many researchers; however, published experimental investigations of hydrous ethanol use in RCCI are scarce. Making greater use of hydrous ethanol in internal combustion engines has the potential to dramatically improve the economics and life cycle carbon dioxide emissions of using bio-ethanol. In this work, an experimental investigation was conducted using 150 proof hydrous ethanol as the low reactivity fuel and commercially-available diesel as the high reactivity fuel in an RCCI combustion mode at various load conditions. A modified single-cylinder diesel engine was used for the experiments. Based on previous studies on RCCI combustion by other researchers, early-cycle split-injection strategy of diesel fuel was used to create an in-cylinder fuel reactivity distribution to maintain high thermal efficiency and low NOX and soot emissions. At each load condition, timing and mass fraction of the first diesel injection was held constant, while timing of the second diesel injection was swept over a range where stable combustion could be maintained. Since hydrous ethanol is highly resistant to auto-ignition and has large heat of vaporization, intake air heating was needed to obtain stable operations of the engine. The study shows that 150 proof hydrous ethanol can be used as the low reactivity fuel in RCCI through 8.6 bar IMEP and with ethanol energy fraction up to 75% while achieving simultaneously low levels of NOX and soot emissions. With increasing engine load, less intake heating is needed and EGR is required to maintain low NOX emissions. Future work will look at stability of hydrous ethanol RCCI at higher engine load.

Commentary by Dr. Valentin Fuster
2013;():V001T03A028. doi:10.1115/ICEF2013-19219.

The characteristics of combustion, emissions, and thermal efficiency of a diesel engine with direct injection neat n-butanol were investigated. Tests were conducted on a single cylinder water-cooled four stroke direct injection diesel engine. The engine ran at a load of 6.5 ∼ 8.0 bar IMEP at 1500 rpm engine speed and the injection pressure was controlled to 900 bar. The intake boost pressure, injection timing and EGR rate were adjusted to investigate the engine performance. The test results showed that significantly longer ignition delays were possible when using butanol compared to diesel fuel. Butanol usage generally led to a rapid heat release in a short period, resulting in excessively high pressure rise rate. The pressure rise rate was reduced by retarding the injection timing. The butanol injection timing was limited by misfire and pressure rise rate. Thus, the ignition timing controllable window by injection timing was much narrower than that of diesel. The neat butanol combustion produced near zero soot and very low NOx emissions even at low EGR rate. The tests demonstrated that neat butanol had the potential to achieve ultra-low emissions. However, challenges related to reducing the pressure rise rate and improving the ignition controllability were identified.

Topics: Diesel engines
Commentary by Dr. Valentin Fuster
2013;():V001T03A029. doi:10.1115/ICEF2013-19226.

Suitable cylinder charge preparation is deemed critical for the attainment of a highly homogeneous, diluted, and lean cylinder charge which is shown to lower the flame temperature. The resultant low temperature combustion (LTC) can simultaneously reduce the NOx and soot emissions from diesel engines. This requires sophisticated coordination of multiple control systems for controlling the intake boost, exhaust gas recirculation (EGR), and fueling events. Additionally, the cylinder charge modulation becomes more complicated in the novel combustion concepts that apply port injection of low reactivity alcohol fuels to replace the diesel fuel partially or entirely. In this work, experiments have been conducted on a single cylinder research engine with diesel and ethanol fuels. The test platform is capable of independently controlling the intake boost, EGR rates, and fuelling events. Effects of these control variables are evaluated with diesel direct injection and a combination of diesel direct injection and ethanol port injection. Data analyses are performed to establish the control requirements for stable operation at different engine load levels with the use of one or two fuels. The sensitivity of the combustion modes is thereby analyzed with regard to the boost, EGR, fuel types and fueling strategies. Zero-dimensional cycle simulations have been conducted in parallel with the experiments to evaluate the operating requirements and operation zones of the LTC combustion modes. Correlations are generated between air-fuel ratio (λ), EGR rate, boost level, in-cylinder oxygen concentration and load level using the experimental data and simulation results. Development of a real-time boost-EGR set-point determination to sustain the LTC mode at the varying engine load levels and fueling strategies is proposed.

Commentary by Dr. Valentin Fuster
2013;():V001T03A030. doi:10.1115/ICEF2013-19238.

As future downsized boosted engines may employ multiple combustion modes, the goal of the current work is the definition of valving strategies appropriate for moderate to high load spark ignition (SI) combustion and for spark assisted compression ignition (SACI) combustion at low to moderate loads for an engine with variable valve timing capability and fixed camshaft profiles. The dilution and unburned gas temperature requirements for SACI combustion can be markedly different from those of SI; therefore it is important to ensure that a given valving strategy is appropriate for operation within both regimes. This paper compares one dimensional (1D) thermodynamic simulations of rated engine operation with positive valve overlap (PVO) and a baseline negative valve overlap (NVO) camshaft design in a boosted automotive engine with variable valve timing capability. Several peak lifts and valve open durations are investigated to guide the down-selection of camshaft profiles for further evaluation under SACI conditions in a companion paper.

While the results of this study are engine specific, rated performance predictions show that the duration of both the intake and exhaust camshafts significantly impacts the ability to achieve high load operation. While it was noted that the flow through the exhaust valve chokes for the majority of the exhaust stroke for peak exhaust lifts less than 8 mm, the engine rating could be achieved with peak intake lifts as low as 4 mm. Therefore, camshafts with peak lifts of 8/4 mm exhaust/intake were down selected to facilitate multimode combustion operation with high levels of PVO. Analysis of high load operation with the down-selected camshafts indicates that peak unburned gas temperatures remain low enough to mitigate end-gas knock, while other variables such as peak cylinder pressure, turbine inlet temperature and turbocharger speed are all predicted to be within acceptable limits.

Commentary by Dr. Valentin Fuster

Emissions Control Systems

2013;():V001T04A001. doi:10.1115/ICEF2013-19022.

In recent years, the purification of sulfur oxides in shipping exhaust is becoming the focus of attention. It is especially important about how to accurately determine and control the various factors affecting desulfurization efficiency. This paper built a mathematical model, mainly focusing on action and mass transfer characteristic of gas-liquid absorption progress of natrium-alkali desulphurization system. It is based on gas-liquid complicated reactions of packed absorption tower, obtaining the influence of concentration distribution of various components in liquid phase, as well as partial pressure, pH value, mass transfer rate, absorption enhancement factor, liquid gas ratio and other key parameters on SO2 absorption rate. As shown in the models, the removal efficiency of 97.8% is equivalent to use a sulfur content of 3.5% fuel oil under the restrictions in emission control area. According to the calculation of 4.0 MW diesel engines, the minimum supply rate of absorption liquid is 75.8 L/h. These data have the reference significance for the development and evaluation of shipping flue gas desulfurization systems.

Topics: Exhaust systems
Commentary by Dr. Valentin Fuster
2013;():V001T04A002. doi:10.1115/ICEF2013-19157.

Spark ignition direct injection (SIDI) gasoline engines, especially in downsized boosted engine platforms, are increasing their market share relative to port fuel injection (PFI) engines in U.S., European and Chinese vehicles due to better fuel economy by enabling higher compression ratios and higher specific power output. However, particulate matter (PM) emissions from engines are becoming a concern due to adverse human health and environment effects, and more stringent emission standards. To conduct a PM number and size comparison between SIDI and PFI systems, a 2.0 L boosted gasoline engine has been equipped and tested with both systems at different loads, air fuel ratios, spark timings, fuel pressures and injection timings for SIDI operation and loads, air fuel ratios and spark timings for PFI operation.

Regardless of load, air fuel ratio, spark timing, fuel pressure, and injection timing, particle size distribution from SIDI and PFI is shown to be bimodal, exhibiting nucleation and accumulation mode particles. SIDI produces particle numbers that are an order of magnitude greater than PFI. Particle number can be reduced by retarding spark timing and operating the engine lean, both for SIDI and PFI operation. Increasing fuel injection pressure and optimizing injection timing with SIDI also reduces PM emissions. This study provides insight into the differences in PM emissions from boosted SIDI and PFI engines and an evaluation of PM reduction potential by varying engine operating parameters in boosted SIDI and PFI gasoline engines.

Commentary by Dr. Valentin Fuster
2013;():V001T04A003. doi:10.1115/ICEF2013-19162.

The implementation of exhaust gas recirculation (EGR) coolers has recently been a widespread methodology for engine in-cylinder NOX reduction. A common problem with the use of EGR coolers is the tendency for a deposit, or fouling layer to form through thermophoresis. These deposit layers consist of soot and volatiles and reduce the effectiveness of heat exchangers at decreasing exhaust gas outlet temperatures, subsequently increasing engine out NOX emission.

This paper presents results from a novel visualization rig that allows for the development of a deposit layer while providing optical and infrared access. A 24-hour, 379 micron thick deposit layer was developed and characterized with an optical microscope, an infrared camera, and a thermogravimetric analyzer. The in-situ thermal conductivity of the deposit layer was calculated to be 0.047 W/mK. Volatiles from the layer were then evaporated off and the layer reanalyzed. Results suggest that volatile bake-out can significantly alter the thermo-physical properties of the deposit layer and hypotheses are presented as to how.

Topics: Soot
Commentary by Dr. Valentin Fuster
2013;():V001T04A004. doi:10.1115/ICEF2013-19199.

Diesel particulate filters (DPF) have seen widespread application in the United States and Europe to meet stringent diesel particulate matter (PM) emissions regulations. Now commonplace on most on-road diesel vehicles, DPFs are being increasingly applied to diesel-powered off-road equipment as additional regulations are phased in. Further, recent awareness of particulate matter emissions from gasoline direct injection engines has motivated additional study into potential applications of gasoline particulate filters (GPF).

Key to the efficient operation of the combined engine and emissions aftertreatment system, is the accurate determination of the filter loading state, to enable precise control of filter regeneration and on-board diagnostics. Currently pressure- and model-based controls are utilized, in parallel, to provide an indirect estimate of filter loading. This work presents results of an investigation applying radio frequencies (RF) to monitor the accumulation of particulate matter in the DPF, providing a direct, in-situ determination of filter loading state. Simulation results, supported by experimental measurements, are provided to demonstrate the utility of the technique to monitor not only the filter loading state but also to provide a measure of the spatial distribution of the accumulated material. The results of this work indicate significant potential to apply RF-based sensing for improved monitoring and control of the particulate filter in a range of applications.

Commentary by Dr. Valentin Fuster

Instrumentation, Controls, and Hybrids

2013;():V001T05A001. doi:10.1115/ICEF2013-19025.

Cylinder pressure based combustion state control is a direction that has drawn much attention in the field of internal combustion engine control, especially in the field of diesel HCCI (Homogeneous Charge Compression Ignition) research. In-cylinder pressure sensors have the potential to diagnose or even replace many traditional sensors, including camshaft and crankshaft sensors. This paper did research on engine synchronization method based on in-cylinder pressure signal. The research was based on a 4-cylinder high pressure common rail diesel engine equipped with 4 PSG (Pressure Sensor Glow Plug) type piezo-resistance cylinder pressure sensors, intended for HCCI research. Through theoretical analysis and experimental proof, methods and models for cylinder identification, engine phase estimation and engine speed estimation are given and further verified by experiments. Results show that cylinder pressure sensor could be used to identify cylinder instead of cam shaft sensor. The models for engine phase and speed estimation have been proved to have precision of 3° crank angle and 4.6rpm, respectively. The precision of engine phase and speed estimation provides a possibility for the engine to run if the crankshaft sensor fails, but more researches have to be carried out with respect to crankshaft sensor replacement.

Commentary by Dr. Valentin Fuster
2013;():V001T05A002. doi:10.1115/ICEF2013-19030.

In this paper, a diesel SOC (Start of Combustion) online detection method is developed in a diesel engine equipped with serial produced in-cylinder pressure signal sensors. Motored pressure trace is estimated in real time and the difference between the measured actual cylinder pressure and the estimated motored pressure is calculated. SOC is defined as the separation point of the two different pressure traces. In order to realize accurate motored pressure estimation, a thermodynamic analysis of the motored process of engines is done and a new concept “equivalent adiabatic exponent” is proposed. The pressure difference 0.2 MPa is taken as the criteria of combustion start. The SOC detection algorithm is executed in a MCU based electronic control unit. Engine tests are done in steady states as well as dynamic states.

Commentary by Dr. Valentin Fuster
2013;():V001T05A003. doi:10.1115/ICEF2013-19038.

The hybridization and electrification of powertrains gain increasing popularity in recent years, especially in the field of construction machine. In this paper, a TITO (Two-input Two-Output) coupling control strategy for parallel hybrid excavator is studied. First, the structure and configuration of the parallel hybrid powertrain are introduced. Then, a TITO coupling control strategy is presented. Engine speed and SOC (State of Charge) of super capacitor are controlled by engine torque and ISG torque together. Whereafter, the model of powertrain and control strategy is built in Matlab/Simulink. Then, networked control system for parallel hybrid excavator is introduced. Finally, the control strategy is optimized and validated by field tests. The results show that the operating region is close to the high efficiency working point and SOC of super capacitor maintains within 50% and 70%. Compared with conventional hydraulic excavator, a 15% reduction in fuel consumption is achieved.

Commentary by Dr. Valentin Fuster
2013;():V001T05A004. doi:10.1115/ICEF2013-19091.

With the increasingly stringent emissions and fuel economy standards, there is a need to develop new advanced in-cylinder sensing techniques to optimize the operation of internal combustion engine. In addition, reducing the number of on-board sensors needed for proper engine monitoring over the life time of the vehicle would reduce the cost and complexity of the electronic system.

This paper presents a new technique to enable one engine component, the fuel injector, to perform multiple sensing tasks in addition to its primary task of delivering the fuel into the cylinder. The injector is instrumented within an electric circuit to produce a signal indicative of some injection and combustion parameters in electronically controlled spark ignition direct injection (SIDI) engines. The output of the multi sensing fuel injector (MSFI) system can be used as a feedback signal to the engine control unit (ECU) for injection timing control and diagnosis of the injection and combustion processes. A comparison between sensing capabilities of the multi-sensing fuel injector and the spark plug-ion sensor under different engine operating conditions is also included in this study. In addition, the combined use of the ion current signals produced by the MSFI and the spark plug for combustion sensing and control is demonstrated.

Commentary by Dr. Valentin Fuster
2013;():V001T05A005. doi:10.1115/ICEF2013-19096.

Control and detection of misfire is an essential part of on-board diagnosis of modern SI engines. This study proposes a novel model-based technique for misfire detection of a multi-cylinder SI engine. The new technique uses a dynamic engine model to determine mean output power, which is then used to calculate a new parameter for misfire detection. The new parameter directly relates to combustion period and is sensitive to the engine speed fluctuations caused by misfire. The new technique only requires measured engine speed data and it is computationally viable for use in a typical ECU.

The new technique is evaluated experimentally on a 4-cylinder 1.6-liter SI engine. Three types of misfires are studied including single, continues, and multiple events. The steady-state and transient experiments were done for a wide range of engine speeds and engine loads, using a vehicle chassis dynamometer and on-road vehicle testing. The validation results show the new technique is capable to detect all the three types of misfire with up to 97 percent accuracy during steady-state conditions. The new technique is augmented with a compensation factor to improve the accuracy of the technique for transient operations. The resulting technique is shown to be capable of detecting misfire during both transient and steady-state engine conditions.

Commentary by Dr. Valentin Fuster
2013;():V001T05A006. doi:10.1115/ICEF2013-19097.

High fidelity models that balance accuracy and computation load are essential for real-time model-based control of Homogeneous Charge Compression Ignition (HCCI) engines. Grey-box modeling offers an effective technique to obtain desirable HCCI control models. In this paper, a physical HCCI engine model is combined with two feed-forward artificial neural networks models to form a serial architecture grey-box model. The resulting model can predict three major HCCI engine control outputs including combustion phasing, Indicated Mean Effective Pressure (IMEP), and exhaust gas temperature (Texh). The grey-box model is trained and validated with the steady-state and transient experimental data for a large range of HCCI operating conditions. The results indicate the grey-box model significantly improves the predictions from the physical model. For 234 HCCI conditions tested, the grey-box model predicts combustion phasing, IMEP, and Texh with an average error less than 1 crank angle degree, 0.2 bar, and 6 °C respectively. The grey-box model is computationally efficient and it can be used for real-time control application of HCCI engines.

Commentary by Dr. Valentin Fuster
2013;():V001T05A007. doi:10.1115/ICEF2013-19107.

Integrated control of HCCI combustion phasing, load, and exhaust aftertreatment system is essential for realizing high efficiency HCCI engines, while maintaining low HC and CO emissions. This paper introduces a new approach for integrated HCCI engine control by defining a novel performance index to characterize different HCCI operating regions. The experimental data from a single cylinder engine at 214 operating conditions is used to determine the performance index for a blended fuel HCCI engine. The new performance index is then used to design an optimum reference trajectory for a multi-input multi-output HCCI controller. The optimum trajectory is designed for control of combustion phasing and IMEP, while meeting catalyst light-off requirements for the exhaust aftertreatment system. The designed controller is tested on a previously validated physical HCCI engine model. The simulation results illustrate the successful application of the new approach for controller design of HCCI engines.

Commentary by Dr. Valentin Fuster
2013;():V001T05A008. doi:10.1115/ICEF2013-19130.

The increasing request for pollutant emissions reduction spawned a great deal of research in the field of combustion control and monitoring. As a matter of fact, newly developed low temperature combustion strategies for Diesel engines allow obtaining a significant reduction both in particulate matter and NOx emissions, combining the use of high EGR rates with a proper injection strategy. Unfortunately, due to their nature, these innovative combustion strategies are very sensitive to in-cylinder thermal conditions. Therefore, in order to obtain a stable combustion, a closed-loop combustion control methodology is needed.

Many works demonstrate that a closed-loop combustion control strategy can be based on real-time analysis of in-cylinder pressure trace, that provides important information about the combustion process, such as start of combustion, center of combustion and torque delivered by each cylinder. Nevertheless, cylinder pressure sensors on-board installation is still uncommon, due to problems related to unsatisfactory measurement long term reliability and cost.

This paper presents a newly developed approach that allows extracting information about combustion effectiveness through the analysis of engine vibrations. In particular, the developed methodology can be used to obtain an accurate estimation of the indicated quantities of interest combining the information provided by engine speed fluctuations measurement and by the signals coming from acceleration transducers mounted on the engine.

This paper also reports the results obtained applying the whole methodology to a light-duty turbocharged Common Rail Diesel engine.

Commentary by Dr. Valentin Fuster
2013;():V001T05A009. doi:10.1115/ICEF2013-19132.

Combustion control is assuming a crucial role in reducing engine tailpipe emissions and maximizing performance. The number of actuations influencing the combustion is increasing, and, as a consequence, the calibration of control parameters is becoming challenging. One of the most effective factors influencing performance and efficiency is the combustion phasing: for gasoline engines control variables such as Spark Advance (SA), Air-to-Fuel Ratio (AFR), Variable Valve Timing (VVT), Exhaust Gas Recirculation (EGR) are mostly used to set the combustion phasing.

The optimal control setting can be chosen according to a target function (cost or merit function), taking into account performance indicators, such as Indicated Mean Effective Pressure (IMEP), Brake Specific Fuel Consumption (BSFC), pollutant emissions, or other indexes inherent to reliability issues, such as exhaust gas temperature, or knock intensity.

Many different approaches can be used to reach the best calibration settings: Design Of Experiment (DOE) is a common option when many parameters influence the results, but other methodologies are in use: some of them are based on the knowledge of the controlled system behavior, by means of models that are identified during the calibration process.

The paper proposes the use of a different concept, based on the extremum seeking approach. The main idea consists in changing the values of each control parameter at the same time, identifying its effect on the monitored target function, allowing to shift automatically the control setting towards the optimum solution throughout the calibration procedure. An original technique for the recognition of control parameters variations effect on the target function is introduced, based on spectral analysis.

The methodology has been applied to data referring to different engines and operating conditions, using IMEP, exhaust temperature and knock intensity for the definition of the target function, and using SA and AFR as control variables. The approach proved to be efficient in reaching the optimum control setting, showing that the optimal setting can be achieved rapidly and consistently.

Commentary by Dr. Valentin Fuster
2013;():V001T05A010. doi:10.1115/ICEF2013-19134.

A control-oriented model and its associated tuning methodology is presented for the air path of a six cylinder 13 L diesel engine equipped with an asymmetric twin-scroll turbine, wastegate (WG), and exhaust gas recirculation (EGR). This model is validated against experimental engine data and shows good agreement. The small scroll of the asymmetric twin scroll turbine is fed by the exhaust of three cylinders via a split manifold that operates at higher pressure than the exhaust manifold feeding the larger turbine scroll. The asymmetric design with the high exhaust back pressure on three of the six cylinders gives the necessary EGR capability, with reduced pumping work, but leads to complex flow characteristics. The mean-value model describes the flows through the engine, the flow through the two turbine scrolls, the EGR flow, and the WG flow as they are defined, and defines the pressure of the manifolds they connect to. Using seven states that capture the dynamics of the pressure and composition in the manifolds and the speed of the turbo shaft, the model can be used for transient control, along with set point optimization for the EGR and WG flows for each speed and load condition. The relatively low order of the model makes it amenable to fast simulations, system analysis, and control design.

Commentary by Dr. Valentin Fuster

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