Advanced Technology

2005;():1-9. doi:10.1115/ICEF2005-1219.

Wireless microwave telemetry addresses the difficult issue of obtaining transducer outputs from reciprocating and rotating components through the use of advanced electronic components. This eliminates the requirements of a direct link between the transducer and the acquisition system. Accuracy of the transducer signal is maintained through the use of a double frequency modulation (FM) technique which provides temperature stability and a 20 point calibration of each, complete system. Multiple transmitters can be used for larger applications and multiple antennas can be used to improve the signal strength and reduce the possibility of dropouts. Examples of piston temperature and automotive torque converter measurements are provided, showing the effectiveness of the wireless measuring technique.

Topics: Microwaves , Telemetry
Commentary by Dr. Valentin Fuster
2005;():11-17. doi:10.1115/ICEF2005-1239.

This paper describes experimental research aimed at developing techniques for monitoring the growth of combustion chamber deposits in diesel engines using data obtained from cylinder pressure and exhaust temperature measurements. A naturally aspirated single cylinder research engine was operated alternately between low load “coking” conditions (2.5 bar BMEP) and higher load “decoking” conditions (5.5 bar BMEP) intended to promote the formation and removal, respectively of combustion chamber deposits. The polytropic exponent of compression was observed to increase during coking runs and decrease during decoking runs. The peak heat release rate was observed to decrease during coking runs and increase during decoking runs. The peak cycle value of the first derivative of the exhaust thermocouple signal decreased during coking runs but exhibited no clear trend during decoking runs. Conventional exhaust temperature measurements showed no consistent trend during coking runs but the exhaust temperature decreased during decoking runs.

Commentary by Dr. Valentin Fuster
2005;():19-28. doi:10.1115/ICEF2005-1267.

Engine control algorithms are among the most important factors that affect engine performance and emission. Developing control algorithms would improve engine performance, fuel consumption and emission levels. On the other hand, time and cost reduction of controller development is becoming an ever increasing demand. To meet these demands, more advanced engine models and better controller development processes are essential. Therefore, those models with good accuracy together with high calculation speed and fewest numbers of tests for calibration are most suitable. The mean value engine models are developed to meet these criteria. The governing equations for these models are simple and relatively easy to calibrate. The main purpose of this work was to simplify the equations of such a model, decrease the number of calibration tests and improve model accuracy. Simpler equations are used for the calculation of air mass flow at the throttle body and cylinder ports. To increase the accuracy of the manifold pressure calculations, two different relations are proposed and the results are compared. Also a set of equations is presented for rotational dynamics. Then the accuracy of the developed model is examined through the experimental works carried out on the engine of a locally manufactured vehicle called Samand.

Topics: Engines
Commentary by Dr. Valentin Fuster
2005;():29-35. doi:10.1115/ICEF2005-1302.

This paper describes experimental research aimed at developing an on-board smoke sensor for diesel engines. The sensor element was similar to a conventional spark plug. Electrical heating of the insulator was used to prevent carbon fouling from the diesel soot. The sensing element created sparks within the exhaust pipe and changes in smoke levels were detected through analysis of the voltage levels of the sparks. The system was tested in a heavy duty diesel engine equipped with Exhaust Gas Recirculation (EGR)) and compared with reference measurements of the Filter Smoke Number (FSN). The experiments showed good sensitivity to step changes in smoke levels (accomplished by varying EGR levels) at smoke levels below 0.5 FSN. However, the sensor suffered from temperature induced signal drift and was unstable under some circumstances. The use of a spark plug with a smaller electrode tip diameter improved the signal stability. It is proposed that measurement and control of the electrode temperature will be necessary to control the signal drift.

Commentary by Dr. Valentin Fuster


2005;():37-46. doi:10.1115/ICEF2005-1228.

This paper documents results from an experimental study performed to determine the effects of several ultra-low sulfur diesel (ULSD) fuels (< 15 ppm S) on exhaust emissions from a 1,500 kW EMD 16-645-E, roots-blown, diesel locomotive engine. U.S. EPA-regulated emission levels of hydrocarbons (HC), carbon monoxide (CO), oxides of nitrogen (NOx ), and particulate (PM) were measured using U.S. EPA locomotive test procedures while operating on four ULSD fuels, plus a fifth baseline fuel which was a commercially-available Federal on-highway diesel fuel (< 500 ppm). The four ULSD fuels were (1) a ULSD California motor vehicle diesel fuel (CARB fuel) with an aromatic content of less than 10 percent, (2) a ULSD “equivalent” California motor vehicle diesel fuel with an aromatic content of 24 percent, (3 and 4) two custom blended “2006 ULSD Federal” diesel fuels with relatively low Cetane Numbers and higher aromatic levels. This paper reports the changes observed in the regulated exhaust emission levels between the ULSD CARB diesel fuels and the ULSD Federal diesel fuels.

Commentary by Dr. Valentin Fuster
2005;():47-53. doi:10.1115/ICEF2005-1234.

The gaseous and particulate emissions from two diesel engines were measured while operating under simulated fault conditions in a controlled laboratory environment. The engines were representative of those typically used in light and heavy-duty mobile underground mining equipment. Faults were applied singly and in combination. Emissions data were measured using laboratory and field instruments for comparison. The development of protocols for field-testing of vehicles are discussed.

Commentary by Dr. Valentin Fuster
2005;():55-66. doi:10.1115/ICEF2005-1235.

The Transportation Development Centre of Transport Canada, in collaboration with Environment Canada’s Emissions Research and Measurement Division, conducted a series of emissions tests onboard the Oceanex RoRo vessel MV Cabot operating between Montréal, Quebec, and St. John’s, Newfoundland. The primary objectives were to verify emissions inventories and demonstrate the feasibility of installing affordable emissions reduction technology on marine vessels as well as compliance with future regulatory emissions limits. The tests also provided an opportunity for Canada to share information on emissions program and technology developments with U.S. regulatory authorities. This may lead to developing joint emissions reduction initiatives for existing marine vessels. This paper describes the field-testing of a water injection system (WIS) to reduce oxides of nitrogen (NOx) emissions from ocean-going vessels. Tests were conducted on a semi-dedicated basis during voyage and under steady-state conditions. The emissions measurements were taken in accordance with ISO 8178-4-E3 protocol and using both marine diesel oil and intermediate fuel oil, which enabled the evaluation of the impact of different fuel type and quality on emissions. An initial series of tests was carried out on the MV Cabot in March 2004, followed by a second series of tests on the same vessel in March 2005. These tests demonstrated the effectiveness of a low-cost WIS for reducing NOx emissions in marine diesel engines. They also showed that water injection reduces NOx at the expense of an increase in both particulate matter and carbon monoxide when using intermediate fuel oil. NOx reductions varied between 10 and 35 percent, and were most effective at high water injection ratios above 50 percent engine load. The test results showed no negative impact of the WIS on fuel consumption or engine operation and performance. This paper compares the results obtained from the consecutive series of tests in terms of the effectiveness of NOx reduction, and analyses the results in the context of other full-scale test results obtained from emissions control system vendors and engine suppliers. It also investigates the theoretical process and technology of water injection through charge air fumigation, and both direct water and fuel/water emulsion injection. In addition, the effects of water injection on engine emissions, operation and maintenance, and the optimization of water injection from a knowledge-based perspective are discussed. Further testing and development of the WIS are required to realize optimal emissions reduction potential and to determine the impact of water injection on fuel consumption, and engine operational performance as well as the impact of fuel quality on emissions.

Commentary by Dr. Valentin Fuster
2005;():67-71. doi:10.1115/ICEF2005-1242.

NOx forms during a combustion process and contributes to ozone, smog, acid rain, eutrophic soil, etc. The use of water to prevent NOx formation during the combustion process is well known. Adding water to the combustion process reduces the flame temperature by increasing the specific heat capacity of charge air. Moisturizing a charge air is one of the most effective methods to add water to the combustion process. In this study, the characteristics of charge air moisturizing method were evaluated on cylinder pressure, heat release rate, exhaust gas temperature, specific fuel oil consumption, NOx reduction rate, etc., using the medium speed diesel engine with a single cylinder.

Commentary by Dr. Valentin Fuster
2005;():73-79. doi:10.1115/ICEF2005-1253.

In this study, ZSM-5 zeolites were successfully in situ synthesized on the surface of honeycomb cordierite substrate and certified by XRD and SEM techniques. Strong interaction between zeolite and substrate has been found during in-situ synthesis, and hydrothermal stabilities of the zeolites was improved by entailing. The in-situ synthesized monolithic ZSM-5/cordierite showed superior thermal and hydrothermal stabilities. Cu-ZSM-5/cordierite was prepared by ion-exchange and impregnation methods were studied as catalysts for selective catalytic reduction (SCR) of nitrogen oxides (NOx ) in a lean-burn gasoline engine. Engine test results show that NOx emission was decreased by reductants of HC and CO in the exhaust gas without any other extra reducing agents. It also exhibited high activities. Using Cu-ZSM-5/cordierite, the maximum NOx conversion efficiency to N2 reached to 64% at the exhaust temperature of 400 °C and the gas hourly space velocity (GHTV) of 25 000/h. Meanwhile, the HC conversion efficiency was about 60%, while CO was little converted. Cu-ZSM-5/cordierite also showed good duration and anti-poison properties. Furthermore, the activated temperature of the Cu-ZSM-5/cordierite was decreased and the NOx conversion was increased via addition of iridium as a modifier.

Commentary by Dr. Valentin Fuster
2005;():81-90. doi:10.1115/ICEF2005-1270.

In this paper, detailed computational study is presented which helps to understand and improve the fuel-air mixing in a new direct-mixture-injection two-stroke engine. This new air-assisted injection system-based two-stroke engine is being developed at the Indian Institute of Science, Bangalore over the past few years. It shows the potential to meet emission norms such as EURO-II and EURO-III and also deliver satisfactory performance. This work proposes a comprehensive strategy to study the air-fuel mixing process in this engine and shows that this strategy can be potentially used to improve the engine performance. A three-dimensional compressible flow code with standard k–ε turbulence model with wall functions is developed and used for this modeling. To account for the moving boundary or piston in the engine cylinder domain, a non-stationary and deforming grid is used in this region with stationary cells in the ports and connecting ducts. A flux conservation scheme is used in the domain interface to allow the in-cylinder moving mesh to slide past the fixed port meshes. The initial conditions for flow parameters are taken from the output of a three-dimensional scavenging simulation. The state of the inlet charge is obtained from a separate modeling of the air-assisted injection system of this engine. The simulation results show that a large, near-stoichiometric region is present at most operating conditions in the cylinder head plane. The state of the in-cylinder charge at the onset of ignition is studied leading to a good understanding of the mixing process. In addition, sensitivity of two critical parameters on the mixing and stratification is investigated. The suggested parameters substantially enhance the flammable proportion at the onset of combustion. The predicted P–θ from a combustion simulation supports this recommendation.

Commentary by Dr. Valentin Fuster
2005;():91-98. doi:10.1115/ICEF2005-1275.

Many of the stationary power generation and agricultural pumping applications in India utilize diesel engines. Recently, as per Government regulations, these engines are required to satisfy stringent emissions norms. This forms the motivation for the present study on a stationary, direct-injection, single cylinder, 10 HP diesel engine. The selected engine was not satisfying the norms. The engine has a hemi- spherical piston bowl and an injector with a finite sac volume. The combustion chamber was made re-entrant and the injector was replaced with a sac-less injector. After these modifications, there is a significant change in emission levels. To understand clearly the effect of the combustion chamber geometry on the emission levels, three-dimensional computational fluid dynamics (CFD) simulations have been performed for the complete suction and closed-valve part of the cycle. Comparisons of turbulent kinetic energy and swirl levels of old and new geometries were systematically conducted. In contrary to the expected, that the swirl and turbulence levels are consistently less in the modified geometry than that of original geometry. A third combustion chamber was proposed and tested computationally. It was found that the in the proposed combustion chamber swirl and turbulence levels are much higher than the baseline engine. Thus, the proposed combustion chamber geometry shows significant potential for the engine to meet the prescribed norms.

Commentary by Dr. Valentin Fuster
2005;():99-104. doi:10.1115/ICEF2005-1277.

Testing of catalytic converter with exhaust gas recirculation system for diesel engine to reduce pollute gases is chosen for present work. The emphasis is given on hydrocarbon (HC), carbon monoxide (CO) and oxides of nitrogen. The catalytic converter was developed with variations of catalyst plates. Perforated plates of copper and combination of copper oxide and cerium oxide (CeO2 +CuO2 ) were used as the catalyst. Copper spacer is used in between plates to vary the distance. Secondary air was injected into the converter to aid oxidization of HC and CO. Experimental study was carried out on computerized kirloskar single cylinder four stroke (10 B.H.P, 7.4 KW) diesel engine test rig with an eddy current dynamometer. The converter was tested with various combination of the exhaust gas re-circulation (EGR) system. There are some improvements in the reduction and conversion efficiency of HC & CO. Exhaust gas recirculation has proved to be effective in reducing NOx .

Commentary by Dr. Valentin Fuster
2005;():105-110. doi:10.1115/ICEF2005-1286.

Described are the methodology, database and example projections to the year 2020 of the cumulative emissions from diesel locomotives in Canada for a range of freight and passenger fleet activity profiles. The emissions include both the criteria air contaminants (CAC) harmful to human health and the principal greenhouse gases (GHG) covered by the Kyoto Protocol to the United Nations Framework on Climate Change. The projections show a continuous reduction in emissions intensities to 2020 as the Canadian railways acquire new locomotives meeting U.S. EPA Tier 2 and Tier 3 emissions limits to accommodate both increased traffic and units being retired.

Commentary by Dr. Valentin Fuster
2005;():111-123. doi:10.1115/ICEF2005-1326.

Derived from natural gas, coal, and even biomass Fischer-Tropsch (F-T) diesel fuels have a number of very desirable properties. The potential for emissions reduction with F-T diesel fuels in laboratory engine tests and on-road vehicle tests is well documented. While a number of chemical and physical characteristics of F-T fuels have been attributed to the observed reduction in emissions, the actual effects of both the fuel properties and in-cylinder combustion characteristics in modern diesel engines are still not well understood. In this study a 2002, six-cylinder, 5.9 liter, Cummins ISB 300 diesel engine, outfitted with an in-cylinder pressure transducer. was subjected to a subset of the Euro III 13-mode test cycle under steady-state operating conditions. Emissions and in-cylinder pressure measurements were conducted for neat F-T diesel, low sulfur diesel (LSD), ultra-low sulfur diesel (ULSD), and a blend of FT/LSD. In addition, a detailed chemical analysis of the fuels was carried out. The differences in the measured combustion characteristics and fuel properties were compared to the emissions variations between the fuels studied, and an explanation for the observed emissions behavior of the fuels was developed.

Commentary by Dr. Valentin Fuster
2005;():125-138. doi:10.1115/ICEF2005-1339.

Catalytic converters have been used for a number of years in the United States to control automotive pollution. A catalytic converter needs to reach a certain temperature before the chemical reactions take place (light-off). Recently, the new regulations on emission standards have prompted a reconsideration of the design of automotive catalytic converters in order to reduce the light-off period of the catalyst. The catalytic converter light-off period is very Important since almost 80% of the emissions from vehicles occur within the first three minutes after cold start in the FTP-75 test. In order to meet these new regulations, current studies have suggested that the catalyst should be “close-coupled”; that is fitted close to the engine exhaust manifold. In order to design “close-coupled” converters, the designer may have to resort to truncated inlet and outlet cones, or distorted inlet pipes due to space limitations. Hence, it is very difficult to achieve good mixing of the exhaust gas, and a good flow distribution at the inlet cross section of the monolith. Based on such a current status in the study of the catalytic converter, the present work focuses on the time-dependent flow patterns, both in the exhaust manifold and the catalytic converter using Computational Fluid Dynamics (CFD). A three-dimensional grid model of an engine exhaust manifold and a close-coupled catalytic converter was developed and analyzed. The flow simulations were performed using KIVA-3 for non-reacting flow fields. These simulations were performed with transient boundary conditions applied at the inlet to the exhaust runners to simulate the opening and closing of exhaust valves. The CFD results were used to study flow uniformity under different operating conditions and to identify the best location for the oxygen sensor.

Commentary by Dr. Valentin Fuster

Fuels and Combustion

2005;():139-144. doi:10.1115/ICEF2005-1108.

With increasingly stringent emissions regulations for NOx and the known tradeoff of fuel consumption with NOx, ensuring the use of appropriate correction factors becomes increasingly significant to the OEM and customer. The Environmental Protection Agency (EPA) has specified in 40CFR Part92 that locomotive engines shall use a NOx correction factor, KNOx = f(KH ), where KH is the humidity correction factor. This paper will present an alternative NOx humidity correction factor for GE Rail 4-stroke medium speed diesel engines. GE Rail’s NOx humidity correction factor will be compared with five other correction factors in a numerical exercise to assess the sensitivity to variations in ambient temperature, ambient pressure, relative humidity and A:F ratio. GE Rail’s alternative correction factor provides a 25% reduction in Line Haul Duty Cycle BSNOx variation and a mean BSNOx reduction of 3% as compared with KNOx correction factor from Part92.

Commentary by Dr. Valentin Fuster
2005;():145-152. doi:10.1115/ICEF2005-1109.

The operation of S.I. engines on lean mixtures is attractive in principle since it can provide improved fuel economy, reduced tendency to knock and extremely low NOx emissions. However, the associated flame propagation rates become degraded significantly and drop sharply as the operating mixture is made increasingly lean. Consequently, there exist distinct operational lean mixture limits beyond which satisfactory engine performance cannot be maintained due to the resulting prolonged and unstable combustion processes. The paper presents experimental data obtained in a single cylinder, variable compression ratio, S.I., CFR engine when operated in turn on CH4 , H2 , CO, gasoline, iso-octane and some of their binary mixtures. A quantitative approach for determining the operational limits of S.I. engines is suggested, compared and validated against corresponding experimental results of other traditional approaches. On this basis, the dependence of the values of the lean mixture operational limits on the composition of the fuel mixtures is investigated and discussed. The operational limit for throttled operation with methane as the fuel is also established.

Topics: Fuels , Engines
Commentary by Dr. Valentin Fuster
2005;():153-160. doi:10.1115/ICEF2005-1212.

The multi-pulse fuel injection in a diesel engine is considered an effective way to reduce nitrogen oxides (NOx) emissions by heat-release shaping. In this research a preliminary energy efficiency analysis has been conducted for various split injection rates and schedules using the in-house and the commercial engine simulation software. Theoretical findings have been validated using experimentally obtained cylinder pressure data for various injection timings from a single-cylinder engine. The theoretical analysis on the shape of heat- release has been made to evaluate the energy efficiency of the post injection pulses on the engine exhaust temperature increases. An investigation of the cycle-to-cycle variation has also been performed for the measured cylinder pressure data.

Commentary by Dr. Valentin Fuster
2005;():161-173. doi:10.1115/ICEF2005-1213.

The use of pilot-ignited, direct-injected natural gas fuelling for heavy-duty on-road applications has been shown to substantially reduce NOx and particulate matter emissions. The fuelling process involves the injection of pilot diesel near top-dead-center, followed shortly afterwards by the injection of natural gas at high pressure. The injection pressure of the gas and diesel will substantially affect the penetration of the fuel into the combustion chamber, the break-up and atomization of the diesel spray, and the mixing and nature of the turbulent gas jet. To investigate these influences, a series of experiments were performed on a single-cylinder heavy-duty engine over a range of engine operating conditions (exhaust gas recirculation fraction, engine speed, engine load). Due to the unique nature of the single-cylinder engine, it was possible to hold all other parameters constant while only varying injection pressure. The results indicated that injection pressure had a substantial impact on emissions and performance at high loads, where substantial reductions in PM and CO were observed, with only minor increases in NOx and no significant effect on tHC or fuel consumption. At low loads, no significant impact on either emissions or performance was detected. The effects of injection pressure, while still significant, were found to be reduced at increased engine speeds. Higher injection pressures were found to consistently reduce both the number density and the size of particles in the exhaust stream.

Commentary by Dr. Valentin Fuster
2005;():175-191. doi:10.1115/ICEF2005-1214.

The paper investigates cyclic variability in a fast-burn engine running on both gasoline or CNG by applying a new diagnostic technique based on a quasi-dimensional multizone model. Two different procedures were proposed for the ‘cycle-resolved’ calibration of the heat transfer correlation in the multizone model. The first procedure relates the cycle-resolved unreleased energy of the charge at the end of the flame propagation to the combustion efficiency determined from the average exhaust gas composition. The second procedure evaluates the coefficient in the heat transfer correlation through the application of the overall energy balance to the ensemble-cycle combustion and keeps them unchanged for all cycles. Both methods gave similar results, though the second procedure showed to be more physically consistent and in better agreement with the experimental results reported in the literature. 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), for both CNG and gasoline operations, 100 consecutive in-cylinder pressure cycles were analyzed for each point in the test matrix and the sensitivity to cyclic variability of pressure, burn-rate and flame front position related parameters was analyzed. Main results showed that maximum pressure derivative, delay from SA of detected combustion start, NO exhaust concentration and maximum burning speed were the most sensitive parameters to cyclic variability. Strong correlations were found to hold between PFP and burned-gas temperature peak value, as well as between peak values of HRR and burning speed. On the contrary, some seemingly reasonable correlations were not assessed: for example, delay from SA of detected combustion start is related neither with PFP value nor with combustion duration. Finally, the results from mean cycle and cycle-resolved calculations were compared. Though they were usually in good agreement, in the case of NO emission and combustion interval calculation. cycle-resolved approach results in improved accuracy.

Topics: Fuels , Engines , Cycles
Commentary by Dr. Valentin Fuster
2005;():193-208. doi:10.1115/ICEF2005-1216.

The necessity for further reductions of in-cylinder pollutant formation and the opportunity to minimize engine development and testing time highlight the need of cycle simulation tools that have to accurately predict the effects of fuel, design and operating variables on engine performance. To develop reliable tools for indicated cycle simulation in SI engines, a correct prediction of heat release is required, which, in turn, involves the evaluation of in-cylinder turbulence generation and flame-turbulence interaction. This can be pursued by the application of a combustion fractal model coupled with semiempirical correlations of available geometrical and thermodynamical mass-averaged quantities. However, in the literature there is a lack of comparisons between the flame propagation speed obtained through these correlations and the experimental data determined under operating conditions that are significant for IC engines running on both conventional and alternative fuels. The present paper develops a new correlation that takes account of the effects of turbulence shrinking on the flame front as well as of the turbulent transfer of both species and heat across the flame front. The procedure has been applied to calculate the burning speeds in the cylinder of a naturally-aspirated bi-fuel engine for a wide range of engine speeds (N = 2000–4600 rpm), loads (bmep = 200–790 kPa), relative air-fuel ratios (RAFR = 0.80–1.30) and spark-advances (SA ranging from 8 deg retard to 2 deg advance with respect to MBT), under both gasoline and CNG operations. The computed burning speeds were compared to those obtained with the correlations currently available in the literature and to the experimental flame propagation data. These latter were extracted from measured in-cylinder pressure by means of a diagnostics technique previously developed by the authors. The results indicate that the burning speeds calculated through the authors’ procedure are in better agreement with the experimental outcomes than those derived from the correlations that are currently available in the literature.

Commentary by Dr. Valentin Fuster
2005;():209-214. doi:10.1115/ICEF2005-1217.

Peak cylinder pressure of a compression-ignition engine can be affected by engine inlet air condition such as its temperature and pressure. The variation of peak cylinder pressure due to varying inlet air temperature and pressure is analytically studied in this paper. An analytical model is developed and thus the variations of peak cylinder pressure can be predicted along with inlet air temperature or pressure varying. It is indicated that cylinder compression ratio (CR) and intake air boost ratio (pm0 /pi0 ) play significant roles in affecting the variation of peak cylinder pressure over inlet air temperature and pressure, and the pressure variation is proportional to CRk and pm0 /pi0 . The predicted results are compared to those from engine experiments, and show a close agreement. The prediction also includes the investigation of the variation in peak cylinder pressure due to varying the cylinder TDC volume. Results from the analytical studies are presented and show that the change in pmax versus a change in the volume is also affected by compression ratio. This indicates that for a certain change in the clearance volume, a higher compression-ratio configuration would produce a greater change in pmax than a lower compression-ratio would with the rest of the engine design parameters remaining unchanged.

Commentary by Dr. Valentin Fuster
2005;():215-224. doi:10.1115/ICEF2005-1220.

A CFD multi-dimensional computational approach has been developed through a combination of a modified KIVA3 code together with a detailed chemical kinetics scheme for the oxidation of n-heptane in air while considering the effects of turbulence. The effects of adding different quantities of hydrogen, methane and carbon monoxide to the heptane on the combustion characteristics of the HCCI engine under different conditions were investigated both experimentally and numerically. The effects of changes in the combustion chamber wall surface temperature on the combustion characteristics of the HCCI engine were examined. It was found that the presence with n-heptane of some hydrogen, methane or carbon monoxide could delay to various extents the autoignition, while changes in the values of the combustion chamber wall temperature influence the autoignition timing and its initial location. It is suggested that the supplementing of the liquid fuel with gaseous fuels and/or application of a suitable glow-plug surface of optimum size and location fitted with temperature control may aid in controlling the combustion process of an HCCI engine while obtaining higher power output without producing knock.

Commentary by Dr. Valentin Fuster
2005;():225-231. doi:10.1115/ICEF2005-1222.

In order to carry out an accurate heat release analysis, it is necessary to solve a non linear set of chemical equilibrium equations to calculate concentrations of the species present in cylinder gases during the combustion process. So, the thermodynamics properties of the mixture can be evaluated. The present paper deals with the study of the thermodynamics of combustion using a genetic approach. A genetic algorithm was used to solve the set of non linear equations. The goal of this method is the possibility of solving the equations set in a wide range of pressure, temperature and equivalence ratio combinations, where more traditional methods are often found to fail.

Commentary by Dr. Valentin Fuster
2005;():233-239. doi:10.1115/ICEF2005-1229.

Pinus product (Turpentine) has been proposed as an alternate to petro fuels since the invention of S.I. engine. In general, due to higher volatility, turpentine has been used only in the S.I. engine. But the present work proves that based on the property of turpentine (Table – 1), it is a very good substitute for diesel fuel. The low cetane number of turpentine oil had prevented the use of 100% turpentine oil in diesel engine. The present work explores the performance, emission and combustion characteristics of turpentine diesel blends and its suitability with C.I. engine. The 20% turpentine 80% diesel blend has an equal combustion and performance characteristics with that of diesel fuel. The experimental results show that some of the toxic gases like CO, UBHC and soot are decreased compared to diesel baseline. In particular around 45% to 50% smoke reduction is obtained with higher turpentine blends. Also it proves that 20% addition of turpentine into conventional diesel fuel improve the performance, combustion, and emission to a considerable limit.

Commentary by Dr. Valentin Fuster
2005;():241-245. doi:10.1115/ICEF2005-1231.

Experimental tests have been carried out to evaluate the performance and emissions characteristics of a diesel engine when fuelled by blends of 25% vegetable oil with 75% diesel fuel, 50% vegetable oil with 50% diesel fuel, 75% vegetable oil with 25% diesel fuel, and 100% vegetable oil, compared with the performance, emissions characteristics of 100% diesel fuel. The series of tests were conducted and repeated six times using each of the test fuels. 100% of ordinary diesel fuel was also used for comparison purposes. The engine worked at a fixed speed of 1500 r/min, but at different loads respectively, i.e. 0%, 25%, 50%, 75% and 100% of the engine load. The performance and the emission characteristics of exhaust gases of the engine were compared and analyzed. The experimental results showed that the carbon monoxide (CO) emission from the vegetable oil and vegetable oil/diesel fuel blends were nearly all higher than that from pure diesel fuel at the engine 0% load to 75% load. Only at the 100% engine load point, the CO emission of vegetable oil and vegetable oil/diesel fuel blends was lower than that of diesel fuel. The hydrocarbon (HC) emission of vegetable oil and vegetable/diesel fuel blends were lower than that of diesel fuel, except that 50% of vegetable oil and 50% diesel fuel blend was a little higher than that of diesel fuel. The oxides of nitrogen (NOx) emission of vegetable oil and vegetable oil/diesel fuel blends, at the range of tests, were lower than that of diesel fuel.

Commentary by Dr. Valentin Fuster
2005;():247-252. doi:10.1115/ICEF2005-1232.

At present, there is a hunt for an alternative source of fuel which should also cause less pollution. Vegetable oil is one such source, which is both renewable and biodegradable. But using straight vegetable oil lead to the clogging of the fuel injectors and there is a problem of starting especially when the engine is cold. Hence straight vegetable oils can be chemically treated to enhance its properties, after which the vegetable oil is known as biodiesel. In this work, biodiesel is prepared from Palm oil and then various tests (load test, Heat balance test and Emission test) are carried out on a Kirloskar engine (single cylinder D.I. diesel engine) by varying the percentage of biodiesel. It has been inferred from the test that performance of the engine decreases and also the various emissions (except NOx) decreases. It has also been inferred that the emissions reduction is maximum when biodiesel is blended with 60% diesel. To decrease NOx, hot EGR (15%) is adopted. Again the above tests are performed with EGR and it has been found that NOx decreases but at the same time the performance of the engine decreases further.

Commentary by Dr. Valentin Fuster
2005;():253-264. doi:10.1115/ICEF2005-1240.

Homogenous Charge Compression Ignition (HCCI) combustion is an efficient operating mode for internal combustion engines operating at low specific power and has the further advantage of very low specific NOx emission rate. High Compression Lean Burn (HCLB) spark ignition (SI) provides a more conventional approach to achieving high engine efficiency. Specific NOx emission rates are low though not as low as with HCCI. Compared with HCCI engines, HCLB-SI engines have the advantage of direct combustion control, (through spark timing), and thus are able to start from cold and operate over a wider range of conditions including higher specific power than HCCI. On the other hand HCCI still has the advantage in efficiency and NOx emission rate. These trade-offs makes it desirable to develop an engine which can operate in either mode, hopefully without significantly adding to engine cost or compromising either mode. This paper presents a first exploration of a dual-mode engine which can use either HCCI or HCLB mode by operating on either a base, low-octane liquid fuel or on reformer gas (RG) produced by steam reforming or partial oxidation from the base fuel. Engine experiments with a CFR engine are used to demonstrate engine operation in both HCLB-SI and HCCI operating modes fueled with some combination of n-heptane and reformer gas. The combustion characteristics including combustion stability and cyclic variation are measured and compared for HCCI operation and RG-fueled HCLB-SI engine operation. CNG-fueled SI engine operation is also used as an additional basis for comparison.

Commentary by Dr. Valentin Fuster
2005;():265-274. doi:10.1115/ICEF2005-1241.

Because they have the potential for ultra low NOx emissions and high efficiency, Homogeneous Charge Compression Ignition (HCCI) engines have the potential to develop a significant niche. However, a narrow operating range, (bracketed by severe knock and misfire problems), presents a formidable obstacle to developing usable HCCI combustion systems. HCCI combustion is influenced by a complex array of operating variables including fuel octane quality, intake preheating temperature, compression ratio, equivalence ratio, exhaust gas recirculation and engine component temperature. These variables affect the two critical combustion parameters: ignition timing and combustion duration. If these two parameters can be controlled by appropriate settings of the operating variables, a good HCCI combustion scheme could be achieved. Therefore, the theoretical prediction of these two combustion parameters as a function of the key operating variables is necessary for development of HCCI combustion. This paper describes a stand-alone, single-zone and multi-zone combustion model which have been developed for the specific purpose of investigating HCCI combustion control. In the multi-zone model, temperature and composition in each zone were adjusted in order to study the effect of in-homogeneity which is critical to understanding ignition timing and combustion duration in real HCCI engines. The models simulated HCCI combustion using two fuels: hydrogen, (11 species, 23 reactions- from CHEMKIN library), and natural gas, (53 species, 325 reactions- from GRI mech). The capabilities of the two models to predict ignition timing, combustion duration and peak pressure were verified against experimental and simulation results of Fiveland et al [2, 11]. The models were then used to study the effect of different in-homogeneity levels of equivalence ratio, intake temperature and residual fraction. The single zone model could only predict ignition timing while the multi-zone model shows the capability to mimic realistic HCCI combustion phenomena. The study showed that some degree of in -homogeneity is critical to predicting performance of the homogeneous charge compression ignition engine. Further, stratification of equivalence ratio was relatively ineffective at changing combustion while stratification of mixture temperature was very effective. Stratification of the residual fraction proved to be the most promising method of controlling combustion parameters and the mechanism was primarily thermal.

Commentary by Dr. Valentin Fuster
2005;():275-281. doi:10.1115/ICEF2005-1243.

In a swirl chamber type diesel engine, a strong swirl is produced inside the swirl chamber during the compression stroke. By spraying the fuel into this chamber and thus forming a good mixture, the engine can obtain excellent combustion even at high speeds. Therefore, swirl chamber type diesel engines are favorable for high-speed operations, and because they can produce high power from a small size, they are used often for small, high-speed diesel engine applications. In order to simultaneously realize a reduction in harmful emissions and improvement in fuel consumption of the swirl chamber type diesel engine, reduction of the mixture formation period and complete combustion must be pursued; an optimum combustion chamber to achieve these tasks must first be designed. In this experiment, the effects of the area and the angle of the passage hole, which are the primary design factors of the swirl chamber type diesel engine, on the engine’s turbulent flow will be investigated. Using the commercial numerical analysis program the passage hole area and angle will be varied to analyze the intake and compression stages.

Commentary by Dr. Valentin Fuster
2005;():283-293. doi:10.1115/ICEF2005-1245.

Homogeneous Charge Compression Ignition (HCCI) combustion is currently limited in application due to several key issues such as a narrow operating range, high hydrocarbon and carbon monoxide emissions and lack of control over the onset of combustion. Exhaust gas recycling (EGR) has the potential to 1) provide reasonable control over the HCCI combustion process and 2) extend its operating range. In this paper, the effect of hot internal EGR on ignition timing and heat release rate of HCCI combustion fuelled with n-heptane has been investigated using the CHEMKIN 0-D closed combustion engine simulation package. An attempt has been made to study the effect of individual components of EGR on cylinder-temperature history and the rate of chemical reaction. The results indicate that combustion initiation is directly linked to the thermal energy contained in the hot EGR but the particular chemical species contained in the EGR have different influences towards ignition timing and heat release rate. This theoretical study would be substantiated by experimental work in the near future.

Commentary by Dr. Valentin Fuster
2005;():295-302. doi:10.1115/ICEF2005-1250.

The intake system of a 2-Valve TJ376QE gasoline engine was modified so that its intake swirl and tumble motions were considerably intensified. The stronger air motions are helpful to organize air and fuel mixture strength distribution. The previous port electronic fuel injection system was modified and the technique of TEFI (Twice Electronic Fuel Injection per cycle) is employed. Through regulations of the two injection timings and proportions, an adequate air and fuel mixture stratification–quasi-homogenous mixture was produced and the lean burn can be realized in a product 2-valve S.I. engine. The experimental results show that the scope of bsfc reduction can be >10 % at quite wide load range by ether 1 injection or by 2 injections. Comparing to the conventional single injection, a leaner mixture can be used by TEFI and an even more reduced fuel consumption of 5% was reached by 2 injections. The optimized values of A/F ratio can be higher by 2–3 units of A/F than that of the single injection method. The TEFI can reduce NOx emission by 35–50% than that of single injection at engine load (bmep) range of 0.20–0.75 (MPa).

Commentary by Dr. Valentin Fuster
2005;():303-309. doi:10.1115/ICEF2005-1256.

An experimental investigation was performed on a small direct injection (DI) diesel engine equipped with a common-rail injection system to reduce exhaust emissions through HCCI (homogenous charge compression ignition) combustion. Recently, strict environmental standard requirements call for both lower fuel consumption and reduced emissions that could not be achieved by conventional diesel combustion. In this work experimental investigations to achieve simultaneous reduction of NOx and soot by combustion of more diluted fuel/air mixture before the start of ignition were carried out. To realize this fundamental concept, the experimental conditions including injection timing and EGR rate are varied with the different engine configurations. For reducing the deposition of early injected fuel, spray angle of injector is reduced to 60° and piston head shape also modified to fit with the new injector and to reduce the compression ratio to 15:1 for expanding the ignition delay to form diluted mixture before the ignition. Experimental results show that reduced spray angle with modified piston head allow very low NOx and soot emission level while maintaining the high IMEP of diesel combustion.

Commentary by Dr. Valentin Fuster
2005;():311-316. doi:10.1115/ICEF2005-1258.

A single cylinder DI (direct injection) diesel engine equipped with common-rail injection system was used to investigate the combustion and emission characteristics of biodiesel fuels. Tested fuels were conventional diesel and biodiesels obtained from unpolished rice oil and soybean oil. The volumetric blending ratios of biodiesel with diesel fuel are set at 0, 10, 20 and 40%. Experimental results show that the peak injection rate is reduced as the mixing ratio increased. The effect of the mixing ratio on the injection delay of biodiesel is not significant at the equal injection pressure. The peak combustion pressure was increased with the increase of the mixing ratio at an injection pressure of 100MPa. The ignition delay became shorter with the increase of the mixing ratio due to a higher cetane number of the biodiesel. HC and CO emissions are decreased at a high injection pressure. However, NOx emissions are increased at higher mixing ratios.

Commentary by Dr. Valentin Fuster
2005;():317-323. doi:10.1115/ICEF2005-1266.

Biodiesel blends were prepared by mixing low sulphur #2 diesel and biodiesel of two origins (canola and frying oil) at two different concentrations (5% and 20%). They were tested in a single-cylinder four-stroke medium-speed diesel engine under three engine modes representing idle, about 50% power and full load conditions. Engine performance and emissions data obtained with the blends were compared to that of engine running with the #2 diesel. Results indicated that the 5% blends could maintain engine power and fuel economy. Frying oil based B5 provided more significant reductions on CO, THC and PM emissions and increments on NOx emissions as compared with that of the canola B5 fuel. The 20% blends reduce engine CO, PM and smoke emissions, but increase NOx emissions by up to approximately 8%. Engine cylinder pressure and injection pressure data was also collected to provide additional information for evaluation of fuel economy and emissions benefits of using the blends.

Commentary by Dr. Valentin Fuster
2005;():325-333. doi:10.1115/ICEF2005-1268.

Atomization of the fuel that is injected to the combustion chamber depends on flow field characteristics during the compression process. Mixture formation, mixture preparation rate and delay period are some of the dominant factors in DI diesel engine performance and emission level. This paper presents a new CFD approach simulation of flow field during intake and compression of a four strokes IC engine. In this model a dynamic mesh is used to simulate the moving boundaries of engine parts, such as piston and valves. Computational domain, which is a precise model of one cylinder, is meshed to 300,000–500,000 cells. In our solution three different two-equation turbulence models are used. The capability of each model is highlighted and the results are compared with relevant works. The focus of these turbulence models and three-dimensional simulation of engine flow are to validate the reliability of flow characteristics. The results accurately demonstrate the three-dimensional characteristics of air motion in the swirl chamber and development of vortices.

Commentary by Dr. Valentin Fuster
2005;():335-342. doi:10.1115/ICEF2005-1281.

The objective of this work is to compare the quality of various diesel fuels using a normal engine and carrying out the test under the actual operating conditions of the engine, unlike the conventional test methods that uses standard test conditions. The standard test conditions involve the running of the diesel engine test rig at a speed of around 800 rpm, which is not the condition when the fuel is actually being used, as the operational speed of commercial engines is around 1500–2000 rpm. Also the non-engine based quality rating methods are not economically liable and are inaccurate as they depend too much on the chemical nature of the fuel. So, the objective of this work is to develop a generalized quality rating procedure with less number of parameters, with a simpler and cheaper method compared to other available methods. A single cylinder diesel engine was used to study the ignition quality of various reference fuels of known Cetane numbers. A relatively simple and compact setup was used, by modifying the existing test rig. The inlet manifold was incorporated with an airflow control valve so that the quantity of air let into the cylinder can be varied. The exhaust gas manifold was modified to enable easier observation of the exhaust gas. The single cylinder diesel engine was made to run at two distinct conditions, namely, the normal and white-puff / critical condition, with the reference fuels of known cetane numbers. The quantity of air available for the fuel to combust is the only difference between the two conditions. The air-fuel ratio of each fuel under both the conditions was continuously monitored. A correlation was developed between the critical air-fuel ratios and the corresponding Cetane numbers. From this correlation, a test fuel can be rated easily by finding the air-fuel ratio, by running it in the same engine at an identical load, at an instant when the “white puff” is observed.

Topics: Fuels
Commentary by Dr. Valentin Fuster
2005;():343-353. doi:10.1115/ICEF2005-1282.

Different synthetic fuels have been investigated within a variety of optical experiments at a rapid compression machine using diverse optical set-ups. The experiments have been carried out to determine the fuel requirements for good homogenisation and a controlled ignition and heat release for HCCI combustion. A directly actuated piezo injection system, which allows a flexible multiple injection strategy has been used to inject the fuel at different times during the compression stroke. Mie-scatter and Schlieren optics have been applied to investigate the different behaviour of the synthetic fuels concerning evaporation and mixture formation. The auto ignition behaviour of the different fuels has been investigated using an intensified relay optics and combustion chamber probes utilising the two-colour-method and a photo multiplier analysis systems. A multiple injection strategy and a 13 hole injection nozzle for HCCI operation mode with diesel-like fuels have been designed and optimised using CFD simulation prior to the experimental work. The experimental results using synthetic fuels will then be used to verify advanced 3D CFD models for multi component fuels and their behaviour concerning mixture formation and HCCI two-stage ignition.

Commentary by Dr. Valentin Fuster
2005;():355-362. doi:10.1115/ICEF2005-1291.

In this study, a phenomenological three-equation soot model was developed for modelling soot formation in diesel engine combustion based on considerations of acceptable computational demand and a qualitative description of the main features of the physics of soot formation. The model was developed based on that of Tesner et al. The model was implemented into the commercial STAR-CD CFD package and was demonstrated in the modelling of soot formation in a single-cylinder research version of Caterpillar 3400 series diesel engine with exhaust gas recirculation. Numerical results show that the new soot formulation overcomes most of the drawbacks in the existing soot models and demonstrates a robust and consistent behaviour with experimental observation. Compared to the existing soot models for engine combustion modelling, some distinct features of the new soot model include: no soot is formed at low temperature, minimal model parameter adjustment for application to different fuels, and there is no need to prescribe the soot particle size.

Commentary by Dr. Valentin Fuster
2005;():363-371. doi:10.1115/ICEF2005-1295.

The influence of hydrogen content in hydrogen-natural gas fuel mixtures on the emissions of a lean-burn spark ignition engine has been examined under representative operating conditions, a mid load and a high load. The hydrogen content in the fuel gas mixtures was varied from 0 to 30% with the balance made up of natural gas. The primary effect on emissions was to influence the tradeoff between NOx and hydrocarbon emissions. At the mid-load condition, increasing the hydrogen content from 0 to 15% at constant equivalence ratio reduced the HC emissions by 80% with little change in NOx emissions. Increasing from 15 to 30% hydrogen content reduced the HC emissions a further 50% but increased the NOx emissions by 16%. At the high load condition, the overall result of increasing the hydrogen content was to increase the NOx emissions substantially without significantly reducing the HC emissions. The impact of increasing hydrogen content on engine efficiency is similar to the impact on hydrocarbon emissions. At the mid-load condition, engine efficiency was increased by increasing hydrogen content, but with diminishing returns. An increase from 0 to 5% hydrogen content provides a significant benefit under marginal combustion conditions but further increases in hydrogen content are less effective.

Commentary by Dr. Valentin Fuster
2005;():373-381. doi:10.1115/ICEF2005-1298.

Accurate heat release analysis based on the cylinder pressure trace is important for evaluating combustion process of diesel engines. However, traditional single-zone heat release models (SZM) have significant limitations due mainly to their simplified assumptions of uniform charge and homogeneity while neglecting local temperature distribution inside cylinder during combustion process. In this study, a heat release analysis based on single-zone model has been evaluated by comparison with computational analysis result using Fire-code, which is based on multi-dimensional model (MDM). The limitations of the single-zone assumption have been estimated. To overcome these limitations, an improved model that includes the effects of spatial non-uniformity has been applied. From this improved single-zone heat release model (Improved-SZM), two effective values of specific heats ratios, denoted by γV and γH in this study, have been introduced. These values are formulated as the function of charge temperature changing rate and overall equivalence ratio by matching the results of the single-zone analysis to those of computational analysis using Fire-code about medium speed marine diesel engine. Also, it is applied that each equation of γV and γH has respectively different slopes according to several meaningful regions such as the start of injection, the end of injection, the maximum cylinder temperature, and the exhaust valve open. This calculation method based on improved single-zone model gives a good agreement with Fire-code results over the whole range of operating conditions.

Topics: Heat , Diesel engines , Errors
Commentary by Dr. Valentin Fuster
2005;():383-391. doi:10.1115/ICEF2005-1299.

The effect of water addition on NO formation in counterflow CH4 /air premixed flames was investigated by numerical simulation. Detailed chemistry and complex thermal and transport properties were employed. The results show that the addition of water to a flame suppresses the formation of NO primarily due to the flame temperature drop. Among a lean, a stoichiometric and a rich premixed flame, the effectiveness of water addition is most significant for the stoichiometric flame and least for the rich flame, since the dominant NO formation mechanism varies. The addition of water also reduces the formation of NO in a flame because of chemical effect that increases the concentration of OH, while reduces the concentrations of O and H. Compared to the stoichiometric flame, the chemical effect is intensified in the lean and rich flames.

Topics: Flames , Methane , Water
Commentary by Dr. Valentin Fuster
2005;():393-404. doi:10.1115/ICEF2005-1301.

In this paper, results of experimental and numerical investigations of stratified exhaust gas recirculation in a single-cylinder gasoline engine are presented. The engine was operated in spray guided direct injection mode. The radial exhaust gas stratification was achieved by a spatial and temporal separated induction of exhaust gas and fresh air. The spatial separated induction was realized by specially shaped baffles in the inlet port. The temporally separated induction was performed by impulse charge valves, with one for the fresh air and one for the exhaust gas. From various possible strategies for time-dependent induction of fresh air and exhaust gas, three different strategies to stratify the exhaust gas were examined. The first strategy was characterized by a closed left inlet port. Due to the closed inlet port, the swirl motion of both fluids were in the same direction. So mixing effects between both fluids should be minimized. The intake of fresh air was after the intake of exhaust gas. Strategy two and three were characterized by a central induction of fresh air through both inlet ports. The exhaust gas was induced with a swirl motion. At strategy two, the induction of fresh air was before the induction of exhaust gas and at strategy three the temporal induction was vice versa. The in-cylinder flow was investigated using CFD simulation to quantify the distribution of fresh air and exhaust gas in the combustion chamber. These various concepts to stratify the exhaust gas were verified by experiments to evaluate the potential of these concepts to reduce NOx -emissions.

Commentary by Dr. Valentin Fuster
2005;():405-413. doi:10.1115/ICEF2005-1307.

CFD Modeling of the injection, the mixing, the combustion and the emission formation processes in a high pressure direct injection (HPDI) natural gas engine is presented in this paper. KIVA3V was used together with an injector model. Two sub-models had been developed that the concurrent injection, ignition and combustion of natural gas and diesel could be simulated. The gas injection was simulated with the injector model. In the injector model, the electromagnetism, the hydraulics and the mechanics were computed by solving a set of ordinary differential equations. Based on the engine experimental data, a combustion model was built in which premixed combustion of natural gas was excluded and the natural gas ignition was initiated by the pilot diesel combustion rather than a spontaneous process. The model calibration and validation are discussed. The model parameters were tuned against one set of engine test data. For the model validation, 30 engine test data were applied. The data were from HPDI engine tests at varied engine speeds, loads and injection timings with and without EGR. The model gave good agreement with the engine tests having no EGR. However, the model, in general, under-predicted the burning rate. With EGR, the model prediction errors were large and the NOx were under-predicted, though the trends were still captured.

Commentary by Dr. Valentin Fuster
2005;():415-423. doi:10.1115/ICEF2005-1327.

A study to explore the effect of EGR upon combustion in a light-duty automotive style diesel engine was performed. The engine used in this study was a Mercedes 1.7L 4 cylinder, direct injected turbodiesel with a common rail injection system. The engine was operated at 2500 RPM, 50% load, with constant rail pressure and injection duration. An endoscope imaging system built by AVL, called the VisioScope™, was used to acquire in-cylinder optical images of combustion events. These images were processed to extract soot radiation temperatures and soot volume fraction for each pixel. The results were compared to global engine measurements using piezo-electric pressure transducers, an emissions bench, and a scanning mobility particle sizer (SMPS) to characterize particulates. It was discovered that the optical data correlated well with the global measurements, allowing for in-depth analysis of the mechanisms of emissions formation at three different EGR levels (0%, 10%, 19%). Several conclusions were reached, including the correlation of soot radiation temperature with NOx production and the correlation of soot luminosity with engine-out PM. Each of these factors was determined as a function of EGR level.

Commentary by Dr. Valentin Fuster
2005;():425-431. doi:10.1115/ICEF2005-1338.

In this study computational fluid dynamics (CFD) was used to model fluid flow and diesel combustion in an IC engine that uses a pre-chamber and a main-chamber. The pre-chamber is located in the cylinder head and a bowl in the piston serves as the main chamber. The study considers the effect of diesel combustion in the pre-chamber on turbulence generation and hence fuel-air mixing and combustion in the piston-bowl. Diesel fuel was injected directly into the pre-chamber and the piston bowl at different times. In order to better determine the effect of pre-chamber combustion on the main chamber combustion, various pre-chamber injection timings were considered. The results show that pre-chamber combustion caused the average cylinder pressure to increase by up to 20% in some cases.

Commentary by Dr. Valentin Fuster
2005;():433-440. doi:10.1115/ICEF2005-1350.

A phenomenological model for smoke prediction from a direct injection (DI) diesel engine is newly evolved from an eddy dissipation model of Dent [1]. The turbulence structure of fuel spray is developed by incorporating the wall impingement to explain smoke formed in free and wall portions. The spray wall interaction is unavoidable in case of modern DI diesel engines of bore less than 125 mm. The new model is one dimensional and based on the recent phenomenological description of spray combustion in direct injection diesel engine. Integration of net soot rate and no need to use empirical tuning constants are the important features, which distinguish the model from existing models. Smoke values are successfully predicted using this model for an engine with heavy-duty applications under widely varying operating conditions.

Topics: Diesel engines , Smoke
Commentary by Dr. Valentin Fuster

Engine Design

2005;():441-446. doi:10.1115/ICEF2005-1110.

The Entropy Generation Minimization (EGM) method is based on the analysis by three sciences (thermodynamics, fluid flow and heat transfer) of the different processes that may occur in a system or in an equipment. Herein the EGM method is applied to internal combustion engines to determine the entropy generation caused by different processes. A model incorporating entropy generation calculations is used to assess various engines configurations. Otto cycle was tested and Variable Valve Timing (VVT) and Variable Compression Ratio (VCR) were applied so thermodynamic benefits could be tested and evaluated. With the referred model, the Miller cycle variables are analyzed in order to establish the best working conditions of an engine under a certain load. The intake and exhaust valve timing, combustion start, compression ratio adjustment and heat transfer are the variables for which a best working condition is determined based on the minimization of the entropy generation of the several engine processes.

Topics: Miller cycle
Commentary by Dr. Valentin Fuster
2005;():447-457. doi:10.1115/ICEF2005-1218.

In four-stroke engines direct injection increases power and fuel economy, which is further improved by charge stratification, due to pumping loss reduction and better combustion efficiency at partial loads. Charge stratification can be obtained by different techniques and injector designs. In every case late injection is necessary for stratification, which however is impaired by fuel dilution and spreading in consequence of burnt gas expansion, leading to incomplete combustion at very light loads. A numerical study has been carried out modifying KIVA code to handle new piston shapes. An innovative combustion chamber that is split in two volumes and allows fuel confinement during combustion has been conceived. CFD comparison has been made between a conventional combustion chamber and the proposed new one in term of combustion efficiency. Combustion is enhanced by the new design and unburnt emissions are reduced.

Commentary by Dr. Valentin Fuster
2005;():459-467. doi:10.1115/ICEF2005-1223.

The UK Ministry of Defence (MoD) operates a wide range of small, high performance boats, used in varying environments, and locations throughout the world. These boats primarily operate using outboard motors (OBMs) due to the optimum power to size and weight ratios they provide, and the ease of maintenance compared to inboard motor boats. The use of OBMs has, with the exception of a large and heavy 27hp diesel (compression ignition) OBM, necessitated the use of Petrol (CIVGAS - F67). This dependency evolved from the difficulty encountered developing a reliable compression ignition OBM over the full power range required (20–250hp) at acceptable power to weight/size ratios. Given the lack of a perceived market for such an engine, very little development work was done in this area in the private sector. The requirement to run OBMs on CIVGAS presents a number of problems for the MoD, including logistical, availability (especially for Special Forces), and safety (especially for HM Ships required to store the fuel on the upper decks). The Marine Propulsion Systems Integrated Project Team (MPS IPT) within MoD’s Defence Logistics Organisation (DLO), was therefore mandated to develop solutions aimed at removing MoD’s reliance on CIVGAS. This resulted in a two pronged approach investigating both micro-gas turbines and multi-fuel OBMs. This paper will present the issues encountered and the development work completed to-date developing multi-fuel reciprocating OBM technology. The primary focus has been developing direct injection, spark ignition multi-fuel OBM technology, capable of using petrol, AVTUR (F34), AVCAT (F44), diesel, and marine distillate oil (MDO - F76). The paper will discuss the project plan, the technologies involved, development work, including test and trials, and the way ahead for the future.

Topics: Combustion , Motors , Gasoline
Commentary by Dr. Valentin Fuster
2005;():469-473. doi:10.1115/ICEF2005-1237.

Moore’s law relates how the integration of semiconductors has progressed in time. This research shows that the exponential trend shown in the electronics manufacturing industry can have applications elsewhere. This study shows that the internal combustion engine followed the same trend for over 70 years. Though not the most used engine variable, engine power density shows the same trends for engines as transistor density does for microchips. This now mature technology has ended its period of rapid growth. However the present day engine trends can show how Moore’s law can be extended to include the slower growth of long established technologies. Because exponential growth cannot go on forever, the extension Moore’s law requires that the logistic function be used. The new function also allows one to predict a theoretical value for maximum power density.

Commentary by Dr. Valentin Fuster
2005;():475-483. doi:10.1115/ICEF2005-1273.

Multi-dimensional computational fluid dynamics simulations were carried out on the intake manifold and cylinder of a four-stroke single cylinder two-wheeler engine. The complex geometry of the manifold and the engine cylinder, and the motion of the intake valve were taken into consideration. Both air flow and two-phase calculations were done to predict the trajectory of the liquid fuel and identify regions of impingement which could lead to film formation and high emissions at startup. The results show that the present geometry of the manifold is non-optimum as large recirculation zones are present. The two-phase simulations show that fuel transport is significantly affected due to the recirculation under idling conditions and significant impingement occurs. The numerical results obtained could be utilized to improve the flow in the manifold for lowering emissions.

Commentary by Dr. Valentin Fuster
2005;():485-489. doi:10.1115/ICEF2005-1285.

The objective of this paper is to simulate road loads experienced by an automobile during an urban driving cycle on an engine test bed. This is to be achieved through the use of a combined eddy-current dynamometer and flywheel arrangement, to load the IC engine on the test bed, and an automatic throttle control system, which will vary engine power under changing load conditions to obtain the desired speed-time variation. This paper is intended to provide a system which will permit engine testing under realistically simulated urban driving conditions; it seeks to avoid the use of chassis dynamometers for this purpose. The test is conducted on the IC engine/dynamometer set-up, which consists of the Maruti Omni’s 3-cylinder, 796cc, 37bhp (@5000 rpm) petrol engine with drive train coupled with an eddy current dynamometer. The paper consists of the following stages: 1. A driving cycle is defined, corresponding to urban driving conditions and tractive resistances are calculated and provided in the form of a resisting torque applied by the dynamometer on the IC engine, controlled by a microcontroller. 2. Inertial loads are calculated and applied on the IC engine via both the dynamometer and a flywheel, which is attached to the dynamometer mounted on a separately fabricated assembly. 3. Throttle control is achieved using a stepper motor, which is used to modify the existing manual throttle control setup. The stepper motor is operated using a micro controller. An interfacing circuit has been fabricated to allow this and program written is used to control the stepper motor and provide desired throttle positions through the driving cycle. 4. Torque control in the dynamometer is to be achieved by using the ‘external mode’ available on the control panel of the dynamometer. This allows communication of values from a micro controller via a parallel port, digital-analog converter, and driver circuit, in the form of voltages signals, allowing torque control to be achieved.

Commentary by Dr. Valentin Fuster
2005;():491-496. doi:10.1115/ICEF2005-1312.

This paper studies the effect of design improvements generally prescribed for the piston pin hole on induced stresses with the help of finite element analysis techniques. This decade has seen a very significant increase in the load rating of internal combustion engines. The engines develop a pressure to the tune of 180 bar and more, which needs to be supported by the pin hole, which rests on the piston pin. Predictions of the effect of the increased load on the pin hole and design modifications to support the higher load have become very important activities during the course of piston development. Two design modification options are studied in this paper. The first modification is based on reducing stress concentration by suitably machining a taper profile for a pre-calculated distance at the inner boss zone. The second modification is carried out by having pin hole longitudinal relieves, popularly known as lube slots. Any modification carried out in the pin hole has an influence on the stress distribution at the bowl zone. Therefore, in addition to the pin hole stress, a thorough study on the stress distribution in the bowl zone is also carried out. The numerical results obtained for the modified designs are compared with the base line configuration and the effects of the modifications are discussed in detail. The modifications are found to have a significant effect in reducing the pin hole hoop stress, which is tensile in nature. But at the same time, it has been observed that the tensile hoop stress value in the bowl area increases. Therefore, it is concluded that the suggested pin hole improvements can be carried out if the induced hoop stress values do not exceed the prescribed values for the selected material. Further studies were made to analyze the influence of thermal loading on the stress induced and also to analyze the influence of combined (mechanical and thermal) loading on the induced stress. The thermal hoop stress were compressive in nature and hence its influence on the combined loading is significant. In this paper the results are normalized and shown as tables and figures.

Topics: Engines , Design , Pistons
Commentary by Dr. Valentin Fuster
2005;():497-503. doi:10.1115/ICEF2005-1313.

This study deals with the prediction of the heat flow and temperature of an IC engine piston having different types of cooling methods. This decade has seen a very significant increase in the load rating of the internal combustion engines. There is a marked shift in the current engines from the conventional NA (Naturally Aspirated) engines. The presence of turbo chargers and super chargers has improved the power output by more than two times. The engines develop a pressure upto 180 bar and release very high heat energy. This has resulted in a piston crown temperature to the tune of 350 Deg. Centigrade. The increase in temperature will have a very serious effect on the lubricating oil, as at elevated temperature oil will have greatly reduced viscosity. Therefore, it is essential to bring the temperature down by having a proper cooling arrangement for the piston system. Two design options of cooling the piston are studied in this paper. In the first option piston is cooled by forcing a jet of oil towards the under-crown portion of the piston. The second option is having a cavity popularly known as cooling gallery, through which the jet of oil is allowed to circulate. The predictive study is carried out by using Finite Element Analysis Techniques. The numerical results obtained for the two options are compared with the base line configuration and the effects of the modifications are discussed in detail. In addition transient thermal analysis is done to predict the transient thermal hoop stress developed in the piston bowl. Since transient hoop stress is the main cause for fatigue failure of the piston bowl, a parametric study is carried out to study the effect of cooling methods on thermal hoop stress.

Commentary by Dr. Valentin Fuster
2005;():505-513. doi:10.1115/ICEF2005-1317.

Using a laser, as opposed to a conventional (electrical) spark plug, to create a combustion initiating spark is potentially advantageous for several reasons: flexibility in choosing and optimizing the spark location, in particular to move the spark away from solid heat sinks; production of a more robust spark containing more energy; and obviation of electrode erosion problems. In this paper we present the on-engine test results of the laser ignition system on a large bore natural gas engine. Test results include: mass fraction burn duration, hydrocarbon emissions data, and combustion stability comparisons to the conventional spark plug ignition system. Design and spark location considerations for the laser ignition system were presented in the first paper of this two-paper series.

Commentary by Dr. Valentin Fuster
2005;():515-521. doi:10.1115/ICEF2005-1319.

Cam-to-follower clearance influences several aspects of engine operation: valve-train noise, which affects acoustic comfort: valve-train dynamics, which affects engine reliability and functionality; valve lift profile and phasing, which influences combustion cyclic stability especially at idle. If mechanical followers are used on an engine, then, depending on engine operating conditions and different thermal expansion between cylinder head and valve, the valve clearance changes. For this reason the initial and final cam ramps are designed in order to minimize the effects of these variations. When a new valve-train is designed the determination of the nominal valve clearance requires an in-depth knowledge of the above mentioned variations. An experimental evaluation of valve clearance in real engine operating conditions would be desirable. In this paper an extensive experimental activity at engine test bed is presented. A simple, economical and precise indicated methodology was set-up and developed in order to directly measure the angular position of the camshaft when each valve tappet starts to move: in this way valve clearance can be directly determined. These measurements were done in different engine operating conditions with respect to speed and load, and also in thermal and speed transient conditions, in order to determine valve clearance maps. On the intake side a maximum increase of 0.13 mm was found with respect to nominal value, while on the exhaust side a maximum decrease of 0.30 mm was determined. This last value was judged excessive, so some design changes were made in order to limit it: in particular a bi-metallic exhaust valve was tested. The improvement with this type of valve varied from 25% to 70% depending on engine load conditions.

Commentary by Dr. Valentin Fuster
2005;():523-534. doi:10.1115/ICEF2005-1320.

An experimental investigation has been carried out for almost the first time to examine the heat transfer by forced convection and subcooled boiling from a finned water-cooled engine cylinder head using steady state technique. Cast iron and cast steel specimens with and without fins have been used in the present work. The effects of flow velocity, coolant bulk temperature, fin length, fin number and fin material have been examined. It has been found that the use of finned cylinder head surface greatly improves the forced convection heat transfer coefficient and subcooled boiling heat flux as the fin length and number influenced the heat transfer process. The cast iron specimen exhibited better heat transfer characteristics over the cast steel one. The effects of bulk flow velocity and temperature for flat and finned specimens have been evaluated for forced convection and subcooled boiling. A correlation has been developed to relate the Nusselt number with Reynolds’ number, Prandtl number, viscosity ratio and fin length ratio, for forced convection from the cast iron specimen, which read:

Nu = 0.023 Re0.697 Pr0.33 μr0.14 (1+A)0.623

Commentary by Dr. Valentin Fuster
2005;():535-541. doi:10.1115/ICEF2005-1324.

Half the engine displacement of popular cars and light trucks would be adequate for most driving. The split engine (SE) is introduced here as a concept to improve the fuel economy of light-duty vehicles with large spark-ignition internal combustion engines. It operates with a small-displacement portion of the engine for typical driving and activates the secondary portion of the engine to assist with high-power driving. SE is different from cylinder deactivation; the two portions of the engine have independent crankshafts which connect through a one-way clutch, a mechanical diode with indexing features to achieve the correct relative phase of the engine sections. For illustration, 6- and 8-cylinder SE are proposed and simple versions are modeled analytically. The 6-cylinder SE consists of two inline 3-cylinder engines of equal or near-equal displacement. The 8-cylinder SE consists of two opposed horizontal 4-cylinder engines of the same displacement. SE and cylinder deactivation are also compared. Moments of inertia and the time to connect both engine sections smoothly are estimated. Fuel economy improvements with SE are estimated for the EPA urban and highway cycles.

Commentary by Dr. Valentin Fuster
2005;():543-546. doi:10.1115/ICEF2005-1341.

In the analysis of internal forces for a slider–crank machine, writing the equations of motion is just the beginning. There are many engineering analysis decisions to be made regarding the handling of the crank angular acceleration, modeling of the connecting rod mass moment of inertia, and the approach to the solution of the resulting system of equations. Over the years, each of these have been handled in various ways, not all of then entirely correct. This paper looks at the various options and makes a critical review of the various practices. The intent is to encourage all engineering analysts to review the assumptions and methods of the software that they routinely use.

Topics: Force , Machinery
Commentary by Dr. Valentin Fuster

Lubrication and Friction

2005;():547-560. doi:10.1115/ICEF2005-1300.

Even though many researchers have measured the piston/ring assembly friction force over the last several decades, accurate measurement of the piston/ring assembly friction force is a still challenging problem. The floating liner method is not widely used, in spite of its accuracy, due to the substantial modifications required to the engine. On the other extreme, bench tests of the piston/ring assembly cannot completely simulate the real firing condition although bench tests are rapid, consistent, and cost effective. In this study, friction forces of the piston/ring assembly were measured using the instantaneous IMEP method and compared with modeling results using Ricardo’s RINGPAK software. In this research, a flexible flat cable was used to connect the connecting rod strain gage signal to the analysis system instead of using a grasshopper linkage. Therefore, the piston/ring assembly friction force was measured with the minimum change to the engine hardware.

Commentary by Dr. Valentin Fuster
2005;():561-567. doi:10.1115/ICEF2005-1321.

New engines are presenting a constant increase of mechanical and thermal loads. The engine components should guarantee similar, or superior, performance than the baseline components in spite of the unfavorable wear conditions. For piston rings, the performance is given by the ring capacity of sealing and scraping. This performance can be measured in an engine by the lube oil consumption (LOC) and the gas flow to the crankcase (Blow-by) results. The purpose of this work is to evaluate the top piston ring wear influence on its sealing and scraping performance. Two engines were tested, one Otto and the other Diesel, in a dynamometer in order to quantify the top ring dimensional variation due to wear. Numerical simulations were performed in order to evaluate the individual influences of each dimensional parameter. The results of LOC and Blow-by were compared to literature data and engine test results of each engine. A proposal of combined effects among the dimensional parameters is presented.

Commentary by Dr. Valentin Fuster
2005;():569-575. doi:10.1115/ICEF2005-1340.

A new wear model for piston ring and cylinder bore system has been developed to predict wear process with high accuracy and efficiency. It will save time and cost compared with experimental investigations. Surfaces of ring and bore were divided into small domains and assigned to corresponding elements in two-dimensional matrix. Fast Fourier Transform (FFT) and Conjugate Gradient Method (CGM) were applied to obtain pressure distribution on the computing domain. The pressure and film thickness distribution were provided by a previously developed ring/bore lubrication module. By changing the wear coefficients of the ring and bore with accumulated cycles, wear was calculated point by point in the matrix. Ring and bore surface profiles were modified when wear occurred. The results of ring and bore wear after 1 cycle, 10 cycles and 2 hours at 3600 rpm were calculated. They coincided well with the general tendency of wear in a ring and bore system.

Commentary by Dr. Valentin Fuster

ARES-ARICE Symposium on Gas Fired Reciprocating Engines

2005;():577-584. doi:10.1115/ICEF2005-1283.

Dilute operation of internal combustion engines through lean fueling and/or high levels of exhaust gas recirculation (EGR) is frequently employed to increase fuel efficiency, reduce NOx emissions, and promote enhanced combustion modes such as HCCI. The maximum level of dilution is limited by the development of combustion instabilities that produce unacceptable levels of cycle-to-cycle combustion variability. These combustion instabilities are frequently stimulated by the nonlinear feedback associated with the residual and recirculated exhaust gases exchanged between successive cycles. However, with the application of adaptive control, it is possible to limit the severity of the combustion variability and regain efficiency and emission reduction benefits that would otherwise be lost. In order to better characterize the benefits of adaptive control, we have employed a two-zone phenomenological combustion model to simulate the onset of combustion instabilities under dilute operating conditions and illustrate the impact of these instabilities on emissions and fuel efficiency. The two-zone in-cylinder combustion model is coupled to a WAVE engine-simulation code, allowing rapid simulation of several hundred successive engine cycles with many external engine parametric effects included. By applying adaptive feedback control to the WAVE model, we demonstrate how mitigation of the extreme combustion events can result in improved efficiency and reduced emissions levels. We expect that this approach can be used to estimate the potential benefits of implementing adaptive control strategies on specific engine platforms to achieve further efficiency and emission-reduction gains.

Commentary by Dr. Valentin Fuster
2005;():585-593. doi:10.1115/ICEF2005-1287.

Program goals for the Advanced Reciprocating Engine Systems (ARES) program of the Department of Energy include efficiency and environmental goals. Lean-burn natural gas engines offer higher efficiency than engines that operate with Stoichiometric air-to-fuel mixtures; however, the excess oxygen in the exhaust of lean engines makes NOx reduction with catalytic aftertreatment difficult. Thus, advancing efficiency via lean combustion results in challenges to meet environmental goals. The lean NOx trap catalyst technology is capable of reducing NOx in lean exhaust and, thereby, enables the potential for lean combustion to meet both efficiency and environmental goals. During lean NOx trap catalysis, NOx in oxygen-rich exhaust is trapped on the catalyst by alkali or alkaline earth-based sorbate materials; then, upon exposure to oxygen-depleted exhaust, the NOx is released and reduced to nitrogen in a process called regeneration. The regeneration process renews the catalyst for more NOx trapping; the cyclic process repeats at periods on the order of a minute. Oxygen depletion during regeneration is accomplished by temporarily operating the catalyst at rich air-to-fuel ratios; traditionally, a variety of methods have been utilized to achieve rich conditions for the catalyst. In this presentation, research of a lean NOx trap on a lean natural gas engine will be presented. Natural gas from the engine supply was used to provide the reductant for the lean NOx trap regeneration process. The natural gas is injected into the exhaust system where oxidation and reforming catalysts partially oxidize and/or reform the natural gas into reductants suitable for lean NOx trap regeneration. Studies of the natural gas oxidation and reforming processes and their relation to NOx reduction performance will be presented.

Commentary by Dr. Valentin Fuster
2005;():595-599. doi:10.1115/ICEF2005-1293.

Large natural gas engines are durable and cost-effective generators of power for distributed energy applications. Fuel efficiency is an important aspect of distributed generation since operating costs associated with fuel consumption are the major component of energy cost on a life-cycle basis; furthermore, higher fuel efficiency results in lower CO2 emissions. Leaner operation of natural gas engines can result in improved fuel efficiency; however, engine operation becomes challenging at leaner air-to-fuel ratios due to several factors. One factor in combustion control is ignition. At lean air-fuel mixtures, reliable and repeatable ignition is necessary to maintain consistent power production from the engine, and spark plug quality and durability play an important role in reliability of ignition. Here research of a novel spark plug design for lean natural gas engines is presented. The spark plug is an annular gap spark plug with a permanent magnet that produces a magnetic field that forces the spark to rotate during spark discharge. The rotating arc spark plug (RASP) has the potential to improve ignition system reliability and durability. In the study presented here, the RASP plug was operated in a small natural gas engine, and combustion stability (measured by the coefficient of variation of indicated mean effective pressure (IMEP)) was measured as a function of air-to-fuel ratio to characterize the ignition performance at lean mixtures. Comparisons were made to a standard J-plug spark plug.

Topics: Gas engines
Commentary by Dr. Valentin Fuster
2005;():601-608. doi:10.1115/ICEF2005-1325.

Laser ignition is considered the prime alternative to conventional coil based ignition for improving efficiency and simultaneously reducing NOx emissions in lean-burn natural gas fired stationary reciprocating engines. In this paper, Argonne’s efforts towards the development of a viable laser ignition system are presented. The relative merits of various implementation strategies for laser based ignition are discussed. Finally, the performance improvements required for some of the components for successful field implementation are listed. Also reported are efforts to determine the relative merit of laser ignition over conventional Capacitance Discharge Ignition (CDI) ignition. Emissions and performance data of a large-bore single cylinder research engine are compared while running with laser ignition and the industry standard CDI system. It was primarily noticed that NOx emissions reduce by 50% under full load conditions with up to 65% reductions noticed under part load conditions. Also, the lean ignition limit was significantly extended and laser ignition improved combustion stability under all operating conditions. Other noticeable differences in combustion characteristics are also presented. Efforts wherein ignition was achieved while transmitting the high-power laser pulses through optical fibers showed performance improvements similar those achieved by using free-space laser ignition.

Commentary by Dr. Valentin Fuster
2005;():609-619. doi:10.1115/ICEF2005-1329.

Waukesha Engine, Dresser, Inc., (Waukesha) entered into a program with the California Energy Commission (CEC) to develop and demonstrate a 500 kWe ultra-low emission, Advanced Reciprocating Internal Combustion Engine (ARICE) for power generation. The purpose of the program was to demonstrate a natural gas fueled engine with emissions control technology that could achieve the following ARICE goals: • Reduce specified emissions by 90%; • Increase thermal efficiency by 10%; • Reduce installed costs of Distributed Generation (DG) systems by 10%; • Maintain engine durability. All changes are with respect to current levels defined at the time the program began. To work towards meeting these program goals Waukesha partnered with two primary subcontractors, Southwest Research Institute (SwRI) and MIRATECH Corporation. The program was originally defined in two phases. In Phase I Waukesha would develop and demonstrate a cooled EGR system. In Phase II further enhancements would be applied to the cooled EGR system with the intent of achieving still further gains in efficiency and reductions in emissions. A cooled Exhaust Gas Recirculation (EGR) system was installed on a base Waukesha H24GSI engine. The diluent properties of the EGR added to the stoichiometric fuel-air charge reduce peak cylinder combustion temperature. The lower combustion temperatures result in lower NOx values without the need for excess air which would yield oxygen in the exhaust gas. The lack of oxygen in the exhaust gas allows the use of an efficient, cost-effective, three-way catalyst (TWC) to reduce all three primary emittants — NOx, CO, and unburned hydrocarbons. This paper describes the Phase I design and development of an ultra-low emission, natural gas engine operating at stoichiometric conditions with cooled EGR and a TWC. Hardware modifications to incorporate the cooled EGR system on the base engine are covered. The TWC and control system developed are briefly described. The EGR engine with control system and three-way catalyst successfully completed a 500 hour durability test at SwRI. Stable control of the engine across the load range and acceptable load response by the unit have been demonstrated. Very low emissions of the three primary pollutants were measured downstream of the catalyst both before and after the 500 hours of durability testing. The phase I emissions goals were easily met. Emission levels near the Phase II goals were achieved. The Phase I engine efficiency was increased 12% and BMEP was increased 33% compared to the baseline engine. Examination of the engine and systems after the 500 hour run did not show signs of unusual wear or deposits. The potential for a cooled EGR system to produce significantly reduced NOx in a reciprocating natural gas engine was demonstrated. Remaining challenges include the demonstration of consistent, long term emissions performance and the long term durability of engine systems and components operating with EGR.

Commentary by Dr. Valentin Fuster
2005;():621-632. doi:10.1115/ICEF2005-1333.

Frictional losses in the piston ring-pack of an engine account for approximately 20% of the total frictional losses within an engine. Although many non-conventional cylinder liner finishes are now being developed to reduce friction and oil consumption, the effects of the surface finish on ring-pack performance is not well understood. The current study focuses on modeling the effects of three-dimensional cylinder liner surface anisotropy on piston ring-pack performance. A rough surface flow simulation program was developed to generate flow factors and shear stress factors for three-dimensional cylinder liner surface textures. Rough surface contact between the ring and liner was modeled using a previously published methodology for asperity contact pressure estimation between actual rough surfaces. The surface specific flow factors, shear stress factors, and asperity contact model were used in conjunction with MIT’s previously developed ring-pack simulation program to predict the effects of different surface textures on ring-pack behavior. Specific attention was given to the effect of honing groove cross-hatch angle on piston ring-pack friction in a stationary natural gas engine application, and adverse effects on engine oil consumption and durability were also briefly considered. The modeling results suggest that ring-pack friction reduction is possible if the liner honing cross hatch angle is decreased by reducing the feed-to-speed ratio of the honing tool. Reducing the cross-hatch angle increased oil flow blockage and increased the lubricant’s effective viscosity during mixed lubrication. This allowed more load to be supported by hydrodynamic pressure, reducing ring-pack friction. However, there appeared to be a potential for increased oil consumption and scuffing tendency corresponding to a decrease in honing cross-hatch angle.

Commentary by Dr. Valentin Fuster
2005;():633-641. doi:10.1115/ICEF2005-1336.

A practical impediment to implementation of laser ignition systems has been the open-path beam delivery used in past research. In this contribution, we present the development and implementation of a fiber-optically delivery laser spark ignition system. To our knowledge, the work represents the first demonstration of fiber coupled laser ignition (using a remote laser source) of a natural gas engine. A Nd:YAG laser is used as the energy source and a coated hollow fiber is used for beam energy delivery. The system was implemented on a single-cylinder of a Waukesha VGF 18 turbo charged natural gas engine and yielded consistent and reliable ignition. In addition to presenting the design and testing of the fiber delivered laser ignition system, we present initial design concepts for a multiplexer to ignite multiple cylinders using a single laser source, and integrated optical diagnostic approaches to monitor the spark ignition and combustion performance.

Commentary by Dr. Valentin Fuster
2005;():643-651. doi:10.1115/ICEF2005-1342.

This paper describes the technical approach for converting a Caterpillar 3406 natural gas spark ignited engine into HCCI mode. The paper describes all stages of the process, starting with a preliminary analysis that determined that the engine can be operated by preheating the intake air with a heat exchanger that recovers energy from the exhaust gases. This heat exchanger plays a dual role, since it is also used for starting the engine. For start-up, the heat exchanger is preheated with a natural gas burner. The engine is therefore started in HCCI mode, avoiding the need to handle the potentially difficult transition from SI or diesel mode to HCCI. The fueling system was modified by replacing the natural gas carburetor with a liquid petroleum gas (LPG) carburetor. This modification sets an upper limit for the equivalence ratio at φ∼0.4, which is ideal for HCCI operation and guarantees that the engine will not fail due to knock. Equivalence ratio can be reduced below 0.4 for low load operation with an electronic control valve. Intake boosting has been a challenge, as commercially available turbochargers are not a good match for the engine, due to the low HCCI exhaust temperature. Commercial introduction of HCCI engines for stationary power will therefore require the development of turbochargers designed specifically for this mode of operation. Considering that no appropriate off-the-shelf turbocharger for HCCI engines exists at this time, we are investigating mechanical supercharging options, which will deliver the required boost pressure (3 bar absolute intake) at the expense of some reduction in the output power and efficiency. An appropriate turbocharger can later be installed for improved performance when it becomes available or when a custom turbocharger is developed. The engine is now running in HCCI mode and producing power in an essentially naturally aspirated mode. Current work focuses on developing an automatic controller for obtaining consistent combustion in the 6 cylinders. The engine will then be tested for 1000 hours to demonstrate durability. This paper presents intermediate progress towards development of an HCCI engine for stationary power generation and next steps towards achieving the project goals.

Commentary by Dr. Valentin Fuster
2005;():653-662. doi:10.1115/ICEF2005-1343.

The piston and rings generate a significant fraction of the total friction in a reciprocating engine, with comparable contributions from the rings and from the piston. In order to develop strategies to reduce overall engine friction, a piston model was used to examine the effects of lubricant, piston design, and material surface characteristics on piston friction. The analysis was performed on a large-bore reciprocating natural-gas engine. First, opportunities in friction reduction via lubricant supply and lubricant formulation were evaluated. This was done by studying how oil film thickness, viscosity, and its temperature dependence affect piston hydrodynamic and boundary-contact friction. Piston design parameters investigated include piston skirt profiles that are more realistic and varied than those previously studied. The piston material was also analyzed in terms of surface waviness. The results show how individual design parameters can be combined to generate the aggregate benefit in engine friction reduction.

Commentary by Dr. Valentin Fuster
2005;():663-671. doi:10.1115/ICEF2005-1346.

A numerical model has been developed to investigate the effects of surface modifications on the lubrication condition and frictional loss at the interface between a piston ring and cylinder liner. The effects of boundary and mixed lubrication conditions were included through the use of a fully deterministic mixed lubrication model, which provides detailed information of the rough contact zone throughout the stroke. The effects of non-Gaussian surface characteristics (e.g. skewness) on the cycle-average frictional performance are discussed. Surface modifications in the form of circular profile dimples were added to the cylinder liner and their effects were investigated. The modified cylinder liner was shown to reduce the cycle-average coefficient of friction by 55–65%, while total energy loss per cycle was reduced by 20–40%.

Commentary by Dr. Valentin Fuster
2005;():673-681. doi:10.1115/ICEF2005-1352.

Due to market demands aimed at increasing the efficiency and the power density of gas engines, existing ignition systems are rapidly approaching their limits. To avoid this, gas engine manufacturers are seeking new technologies. From the viewpoint of gas engine R&D engineers, ignition of the fuel/air mixture by means of a laser has great potential. Especially the thermodynamic requirements of a high compression ratio and a high power density are fulfilled well by laser ignition. Results of measurements on the test bench confirm the high expectations — with a BMEP of 1.8 MPa it was possible to verify NOx values of a non-optimized system of 30 ppm (70 mg/Nm3 @ 5 % O2 ) with very high combustion stability. Despite this, considerable developmental steps are still necessary to adapt the laser ignition concept fully to desired objectives (especially costs).

Commentary by Dr. Valentin Fuster
2005;():683-691. doi:10.1115/ICEF2005-1354.

In the utilization of gas mixtures with high amounts of H2 there is a great number of applications of such special gases, for example several gases that result from pyrolysis or the gasification of biomass or thermally utilizable waste substances. What is special about gases containing H2 is the shifting of the lean-burn limit towards greater amounts of excess air than is the case with natural gas. This effect causes the mean combustion chamber temperatures to sink and the NOx emissions are reduced to a very low level. Depending on the amount of hydrogen and other gas components it is possible to attain NOx values of under 5 ppm. Also very interesting is the property of these H2 -rich gas mixtures to have a neutral influence on the degree of efficiency (even with extremely high amounts of excess air). The background of this property lies in the considerably higher laminar flame speed of hydrogen. Especially in the lower and medium load range this effect can be utilized directly; in this regard it was possible to measure an efficiency of up to 2% points better with operation using pure hydrogen compared with NG. Higher BMEPs are also only possible to a limited extent with extreme lean-burn operation because the knocking limit is reached. Furthermore, the dimensioning of the turbocharger is becoming more and more difficult because the exhaust gas temperature upstream from the turbine sinks and as a result also the thermal energy is available only to a limited degree. When dealing with high amounts of H2 , from the standpoint of operational reliability it is necessary to modify the mixture formation before the TC position to the pressure side position upstream from the intake valve, because otherwise load fluctuations could lead to undesired rich mixtures in the inlet side. As a result, backfiring could occur that could also cause engine damage and that could be hazardous for personnel. From the viewpoint of GE Jenbacher H2 technology can be applied relatively quickly to reduce NOx emissions. Especially when considering the “life cycle costs”, this potential solution is superior to concepts functioning on the basis of stoichiometric combustion. The next step that can be mentioned is the concept of fuel-reforming integrated in the engine — here a part of the exhaust gas energy is used to reform a relatively small amount of natural gas to a CH4 /H2 /CO mixture. With this concept, alongside the dramatic reduction of NOx emissions to the level of fuel cells, the degree of efficiency can be improved by about 2 to 3% points by means of “energy shifting”.

Commentary by Dr. Valentin Fuster

Controls and Instrumentation

2005;():693-702. doi:10.1115/ICEF2005-1294.

This paper describes a means of monitoring cyclic variability in reciprocating engines that is an alternative to cylinder pressure measurements. The monitoring system uses robust exhaust temperature sensors that are capable of detecting cycle-to-cycle variations in the gas temperatures near each exhaust port. These variations are related to cyclic variations in combustion, and tend to increase as cyclic variability worsens. Further processing yields a combustion variability signal that is intended to reflect relative changes in the Coefficient of Variation of Indicated Mean Effective Pressure (COV of IMEP). Proof of concept experiments have been carried out using a naturally aspirated, propane fueled automotive engine equipped with laboratory grade in-cylinder pressure transducers. The results show a good correlation between the exhaust cyclic variability signal and the COV of IMEP from cylinder pressure measurements.

Commentary by Dr. Valentin Fuster

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