This work presents an experimental investigation of advanced combustion of extremely lean natural gas / air mixture in a gas fueled automotive engine with a scavenged pre-chamber. The pre-chamber, which was designed and manufactured in-house, is scavenged with natural gas and is installed into a modified cylinder head of a gas fueled engine for a light duty truck.
For initial pre-chamber ignition tests and optimizations, the engine is modified into a single cylinder one. The pre-chamber is equipped with a spark plug, fuel supply and a miniature pressure transducer. This arrangement allows a simultaneous crank angle resolved pressure measurement in the pre-chamber and in the main combustion chamber and provides important validation data for computational fluid dynamics (CFD) simulations.
The results of the tests and initial optimizations show that the pre-chamber engine is able to operate within a significantly wider range of mixture composition than the conventional spark ignition engine.
Full load operation of the pre-chamber engine is feasible with stoichiometric mixture (compatible with a three-way catalyst), without excessive thermal loading of components. At low load operation, the results show low NOx emissions with a high potential to fulfil current and future NOx limits without lean NOx exhaust gas after-treatment. The scavenged pre-chamber helps to increase the combustion rate mainly in the initial phase of combustion. However, significant unburned hydrocarbons emissions due to incomplete combustion need further optimizations. Thermal efficiency of lean operation of the engine with the pre-chamber compared to the conventional spark ignition system operated in stoichiometric conditions shows approximately 13% improvement.
This paper deals with the application of advanced simulation techniques for combustion modeling in the case of an internal combustion engine. The main focus is put on models with a high predictive ability hence 3-D CFD was selected while using LES (turbulence model) and detailed chemistry (both SI and CI ICE) or turbulent flame propagation (SI ICE). Both engine types are considered – spark ignited ICE and a compression ignited engine. Examples are shown and comparison with available experimental data is presented. The main conclusion is that such models are capable of high quality predictions while very little tuning is needed. This is desired as such models could be applied in the early phases of ICE development. On the other hand, such calculations are very demanding in terms of computational power.
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