Combustion and Emissions in a Spark-ignition Engine Fueled with Coal-Bed Gas - Modeling and Experimental Results 2005-01-3804
There is a worldwide interest in the research of various alternative fuels for automotive engines for the purpose of reduction of CO2 and toxically harmful exhaust emissions. Coal-bed gas, the main component of which is methane, has been considered an attractive alternative fuel for combustion engines due to its abundant resources, high hydrogen-carbon ratios and very low soot formation tendency. The composition of available coal-bed gas, however, can vary considerably, and this has made its combustion stability difficult to control in conventional spark ignition engines.
To overcome the problem, a combustion system with a swirl chamber connected to the main combustion chamber through an orifice has been developed for the use of coal-bed gas in spark ignition engines, and the corresponding combustion process has been studied using a developed combustion model involving flame kernel formation and flame front propagation. The combustion model includes two sub-models with the first dealing with the calculation of turbulence intensity history, and the second modeling a jet flow through the orifice of the swirl chamber. Emissions of NOX, HC and CO have been predicted using the combustion model based on an extended Zeldovich mechanism, wall quenching and incomplete oxidation simulations. The effects of various components in coal-bed gas on the engine combustion process and emissions are also investigated. Validation of the combustion model has been performed through comparing simulation data with the experimental result obtained from a relevant single cylinder research engine, and a satisfactory agreement between them has been achieved in terms of combustion parameters and exhaust emissions.