An Investigation of the Impact of Combustion Chamber Geometry on Turbulent Burning Speeds in a Thermodynamic Model

Combustion is the main parameter that affects efficiency and exhaust gas emissions. Recently, different studies have been carried out to increase the combustion rates due to the increasing use of the alternative fuels and lean mixtures in spark ignition engines. In general, in the absence of systems such as an optical access engine or ionization probes, combustion process evaluation is done based on cylinder pressure. In this study, the effect of different combustion chamber geometries on the turbulent burning speeds was investigated experimentally and theoretically. A three-zone, quasi-dimensional thermodynamic model for a spark ignition engine was constructed. Measured cylinder pressure data were used to establish the transition between the zones of the model and determine turbulent burning speeds. Two different turbulent speeds were calculated in the model, these are flame propagation and consumption speeds. It was seen that combustion chamber geometry significantly affected turbulent burning speeds. In MAN-Ricardo shapes and cylindrical shapes, the turbulent burning speeds decreased after it reached a maximum value in the combustion period. In flat geometry, without any bowl, speed continuously decreased different from other two designs. By means of a quasi-dimensional thermodynamic model, mean values of the turbulent burning and the flame propagation speeds can be calculated without having any optical observation.