Combustion characteristics of a preliminary design of a spark-ignited stratified charge generator 2001-24-0052
The study of the combustion process in a novel internal combustion engine is presented. The novel engine is part of an electric power generator and has been designed to work at low average combustion temperatures to achieve very low NOx emissions. The engine is two-stroke, with one cylinder and two pistons in-line. The combustion occurs in two combustion pre-chambers for each piston. Charge stratification leading to stoichiometric mixture inside the pre-chamber and cold air in the rest of the cylinder is adopted. Progressive burning of the charge is expected to keep the flame inside the pre-chamber with the combustion products ejected very fast and effectively mixed with the cold air in the cylinder. The study has been performed with the help of Computational Fluid Dynamics. For the preliminary engine design, the main characteristics of the combustion process have been analyzed. The preliminary design of the engine showed some problems in keeping the flame confined inside the pre-chambers. Changing the ignition timing with more spark advance partly overcame the problem of the flame location. The simulations reported a low turbulent burning velocity; the combustion duration was found to be longer than what it was expected by designers. The average combustion temperatures were found much higher than the proposed levels for keeping low the NOx. Solutions for the highlighted problems have been proposed and are now under investigation.