Showing papers on "Spark-ignition engine published in 2006"

Comparative bio-fuel performance in internal combustion engines

Abstract: An experimental programme examining performance and emissions from spark- and compression-ignition engines, running on a variety of bio-fuels, including simulated bio-gas and commercial seed oil is presented. Both engines were single-cylinder laboratory-type engines of comparable power output having variable speed and load capability, the spark-ignition engine additionally having variable compression ratio. For bio-gas, containing carbon dioxide, emissions of oxides of nitrogen were reduced relative to natural gas, while unburnt hydrocarbons were increased. Brake power and specific fuel consumption changed little and carbon monoxide was predominantly affected by air:fuel ratio. Equivalent effects were demonstrated with nitrogen replacing carbon dioxide in the simulated bio-gas and similar trends were evident as compression ratio was increased. Seed-oil bio-fuel gave similar performance to diesel fuel without major disadvantages, other than an increased specific fuel consumption. Tests with cetane and rape-seed methyl ester bio-diesel are also presented for comparison. Specific fuel consumption was about the same and specific NOx emissions were lower with bio-fuel than results from the spark-ignition engine tests running on biogas.

Detailed Chemistry Promotes Understanding of Octane Numbers and Gasoline Sensitivity

Abstract: Detailed kinetic models of pyrolysis and combustion of hydrocarbon fuels are now reliable tools which can aid the design of internal combustion engines required to meet the increasingly stringent pollutant formation and engine efficiency standards. The aim of this paper is to discuss and verify the potential of these kinetic models in analyzing the knock related combustion behavior of hydrocarbon fuels with particular regard to octane numbers and octane sensitivity. Detailed chemistry not only helps to explain the different reactivities of alkanes and alkenes but also the combustion behavior of hydrocarbon mixtures. A two-zone model of a spark ignition engine, coupled with the detailed chemistry of combustion processes, was developed and utilized for the predictions of octane numbers. This model explains the effect of various components on the knocking behavior of the fuel under different operating conditions and is thus a useful tool both in formulating new fuels and designing new engines.

Experimental study on engine performance and emissions for an engine fueled with natural gas-hydrogen mixtures

Abstract: An experimental study on the performance and emissions of a spark ignition engine operating on the natural gas−hydrogen mixtures was conducted. The results show that the engine lean-burn limit is extended by the addition of hydrogen into natural gas. For a specific excessive air ratio, engine power output and thermal efficiency decrease with the increase of hydrogen fraction in natural gas when the hydrogen fraction is less than a certain value (20%) whereas engine power output and thermal efficiency increase with further increasing hydrogen fraction when hydrogen fraction is larger than a certain value (20%). Addition of hydrogen into natural gas decreases the exhaust hydrocarbon (HC) concentrations. However, addition of hydrogen into natural gas will increase NOx concentration. Thus, an engine operating on lean-burn natural gas−hydrogen combustion is favorable for getting higher thermal efficiency and lower emissions.

Spark Ignition Engine Combustion Modeling Using a Level Set Method with Detailed Chemistry

Abstract: A level set method (G-equation)-based combustion model incorporating detailed chemical kinetics has been developed and implemented in KIVA-3V for SparkIgnition (SI) engine simulations for better predictions of fuel oxidation and pollutant formation. Detailed fuel oxidation mechanisms coupled with a reduced NOX mechanism are used to describe the chemical processes. The flame front in the spark kernel stage is tracked using the Discrete Particle Ignition Kernel (DPIK) model. In the G-equation model, it is assumed that after the flame front has passed, the mixture within the mean flame brush tends to local equilibrium. The subgrid-scale burnt/unburnt volumes of the flame containing cells are tracked for the primary heat release calculation. A progress variable concept is introduced into the turbulent flame speed correlation to account for the laminar to turbulent evolution of the spark kernel flame. To test the model, a homogeneous charge propane SI engine was modeled using a 100-species, 539-reaction propane mechanism, coupled with a reduced 9-reaction NOx mechanism for the chemistry calculations. Good agreement with experimental cylinder pressures and NOx data was obtained as a function of spark timing, engine speed and EGR levels. The model was also applied to a stratified charge two-stroke gasoline engine simulations, and good agreement with measured data was obtained.

Hot spot formation by the propagating flame and the influence of egr on knock occurrence in si engines

Abstract: Numerical modeling of knocking onset and hot spot formation by propagating flame in SI engines

Method of starting spark ignition engine without using starter motor

Abstract: There is provided a method of starting a spark ignition engine having multiple cylinders. The method comprises stopping fuel upon an engine stop request, introducing air and injecting fuel for restart into a first cylinder before the engine completely stops, and igniting the mixture of the air and the fuel in the first cylinder upon an engine start request. In accordance with the method, by introducing air and injecting fuel into the first cylinder before the engine completely stops, the mixture of air and fuel in the first cylinder may be homogeneous at the time of the engine start request. Also, there may also not be turbulence of the mixture then. Under these states of the mixture in the first cylinder, by igniting the mixture upon the engine start request, the mixture may be relatively slowly combusted. The slower combustion may decrease temperature of the combusted gas, while temperature of the cylinder wall is relatively low at that time because the engine stopped for a while. So, the slower combustion may reduce heat loss in the first cylinder because of smaller difference between the temperatures of the combusted gas and the cylinder wall. Consequently, more energy may be derived from the first cylinder to the crankshaft. Then if the first cylinder is on the compression stroke when the engine stops, as the compression stroke cylinder described above, the crankshaft may rotate more in reverse so that the expansion stroke cylinder described above may ascend more and compress more air therein to exert more reaction force from the compression. It also may combust the more air therein to generate more combustion energy from the expansion stroke cylinder. So, the more compressive reaction force and the more combustion energy may together increase the inertia of the crankshaft at the second top dead center.

Hydrogen-Enhanced Gasoline Stratified Combustion in SI-DI Engines

Abstract: Experimental investigations were carried out to assess the use of hydrogen in a Gasoline Direct Injection (GDI) engine. Injection of small amounts of hydrogen (up to 27% on energy basis) in the intake port creates a reactive homogeneous background for the direct injection of gasoline in the cylinder. In this way, it is possible to operate the engine with high EGR rates and, in certain conditions, to delay the ignition timing as compared to standard GDI operation, in order to reduce NOx and HC emissions to very low levels and possibly soot emissions. The results confirmed that high EGR rates can be achieved and NOx and HC emissions reduced, showed significant advantage in terms of combustion efficiency and gave unexpected results relative to the delaying of ignition, which only partly confirmed the expected behavior. A realistic application would make use of hydrogen-containing reformer gas produced on board the vehicle, but safety restrictions did not allow using carbon monoxide in the test facility. Thus pure hydrogen was used for a best-case investigation. The expected difference in the use of the two gases is briefly discussed.Copyright © 2006 by ASME

The Operating Features of a Stoichiometric, Ammonia and Gasoline Dual Fueled Spark Ignition Engine

Abstract: An overall stoichiometric mixture of air, gaseous ammonia and gasoline was metered into a single cylinder, variable compression ratio, supercharged CFR engine at varying ratios of gasoline to ammonia. The engine was operated such that the combustion was knock-free with minimal roughness for all loads ranging from idle up to a maximum load in the supercharge regime. For a given load, speed, and compression ratio there was a range of ratios of gasoline to ammonia for which knock-free, smooth firing was obtained. This range was investigated at its roughness limit and also at its knock limit. If too much ammonia was used, then the engine fired with an excessive roughness. If too much gasoline was used, then knock-free combustion could not be obtained while the maximum brake torque spark advance was maintained. Stoichiometric operation on gasoline alone was also investigated, for comparison. It was found that a significant fraction of the gasoline used in spark ignition engines could be replaced with ammonia. Operation on mostly gasoline was required near idle. However, mostly ammonia could be used at high load. Operation on ammonia alone was possible at some of the supercharged load points. Generally, the use of ammonia or ammonia with gasoline allowed knock-free operation at higher compression ratios and higher loads than could be obtained with the use of gasoline alone. The use of ammonia/gasoline allowed practical operation at a compression ratio of 12:1 whereas the limit for gasoline alone was 9:1. When running on ammonia/gasoline the engine could be operated at brake mean effective pressures that were more than 50% higher than those achieved with the use of gasoline alone. The maximum brake thermal efficiency achieved with the use of ammonia/gasoline was 32.0% at 10:1 compression ratio and BMEP = 1025 kPa. The maximum brake thermal efficiency possible for gasoline was 24.6% at 9:1 and BMEP = 570 kPa.Copyright © 2006 by ASME

A model-based SI engine air fuel ratio controller

Abstract: A novel linear state-space model predictive controller for SI engine air fuel ratio control is presented and demonstrated over a range of engine operation. The linear model-based controller is an analytical controller that does not require online optimization. Time-varying delay compensation is adapted based on the measured engine speed. A Kalman filter is used to estimate the model and unmeasured disturbance states.

Spark ignition engine

Abstract: A spark ignition engine capable of operating even with a leaner air-fuel mixture to achieve stable ignition and combustion performance An ignition plug (7) is fitted to a cylinder head (1) through a sleeve (6), and the ignition electrode (7a) of the ignition plug (7) is disposed in a cylinder (2), facing a single chamber type combustion chamber (5) The sleeve (6) is formed in a blind cylindrical shape, an auxiliary chamber (10) storing the ignition electrodes (7a, 7b) of the ignition plug (7) is formed at the bottom part of the sleeve (6), and a nozzle hole (6a) allowing the auxiliary chamber (10) to communicate with the combustion chamber (5) is formed in the bottom part of the sleeve The bottom part of the sleeve (6) is projected from an explosion surface (1a) to the inside of the combustion chamber (5) and the position (12) of ignition by the ignition electrode (7a) is set near the explosion surface (1a)

Multivariable EGR/spark timing control for IC engines via extremum seeking

Abstract: This paper proposes a closed loop multivariable EGR/Spark timing management system for maximum dilution control while maintaining a desired level of combustion stability. A combustion stability measure derived from in-cylinder ionization signals is used as feedback. An extremum seeking algorithm is employed to modulate spark timing in a slow-time scale in order to maximize the steady-state EGR amount. Simulation results based on data collected from a 3.0L V6 engine are also included to illustrate the proposed control strategy.

Experimental Investigation of the Knock and Combustion Characteristics of CH4, H2, CO, and Some of Their Mixtures

Abstract: Experimental data obtained in a single-cylinder, variable compression ratio, spark ignition (SI), cooperative fuel research (CFR) engine when operating on CH4, H2, CO, simulated reforming p...

Analysis of combustion in a small homogeneous charge compression assisted ignition engine

Abstract: Combustion analysis has been conducted on a small two-stroke glow ignition engine, which has similar combustion characteristics to homogeneous charge compression ignition (HCCI) engines. Difficulties such as unknown ignition timing and the polytropic index have been addressed by combining both heat release and mass fraction burn analyses. Results for all operating conditions have shown good correlations between the two methods. The engine has been fuelled with a mixture of methanol, nitromethane, and lubrication oil. The effect of nitromethane on combustion is difficult to determine, since altering nitromethane content also changes the air-fuel ratio under the current experiment set-up. However, it is still possible to show that nitromethane shortens the combustion periods beyond the uncertainty created by the mixture strength and cycle-by-cycle variations. The results further show that a faster combustion does not necessarily give a higher indicative mean effective pressure (i.m.e.p.) in this engine. This is because the start of combustion can shift away from its optimum value when nitromethane is added. The initial combustion period is found to be between 10 and 30° CA (crank angle); the main combustion period is between 25 and 50° CA. These com- bustion periods are comparable to a traditional spark ignition engine. In a very rich mixture, the 'hot' glow plug has been found to change significantly the combustion characteristics. Further study would be recommended to elucidate the effect of glow plugs. Lastly, in the case of poor combustion, cycle-by-cycle analysis shows that a misfire or partial burn cycles are always followed by high i.m.e.p. and fast burn cycles.

Analysis of Homogeneous Charge Compression Ignition (HCCI) Engines for Cogeneration Applications

Abstract: This paper presents an evaluation of the applicability of Homogeneous Charge Compression Ignition Engines (HCCI) for small-scale cogeneration (less than 1 MWe) in comparison to five previously analyzed prime movers. The five comparator prime movers include stoichiometric spark-ignited (SI) engines, lean burn SI engines, diesel engines, microturbines and fuel cells. The investigated option, HCCI engines, is a relatively new type of engine that has some fundamental differences with respect to other prime movers. Here, the prime movers are compared by calculating electric and heating efficiency, fuel consumption, nitrogen oxide (NOx) emissions and capital and fuel cost. Two cases are analyzed. In Case 1, the cogeneration facility requires combined power and heating. In Case 2, the requirement is for power and chilling. The results show that the HCCI engines closely approach the very high fuel utilization efficiency of diesel engines without the high emissions of NOx and the expensive diesel fuel. HCCI engines offer a new alternative for cogeneration that provides a unique combination of low cost, high efficiency, low emissions and flexibility in operating temperatures that can be optimally tuned for cogeneration systems. HCCI engines are the most efficient technology that meets the oncoming 2007 CARB NOx standards for cogenerationmore » engines. The HCCI engine appears to be a good option for cogeneration systems and merits more detailed analysis and experimental demonstration.« less