A New Technique to Determine the Burning Velocity in a Gasoline Direct Injection Engine 2014-01-1176

Many approaches have been taken to determine the burning velocity in internal combustion engines. Experimentally, the burning velocity has been determined in optically accessible gasoline engines by tracking the propagation of the flame front from the spark plug to the end of the combustion chamber. These experiments are costly as they require special imaging techniques and major modifications in the engine structure. Another approach to determine the burning velocity is from 3D CFD simulation models. These models require basic information about the mechanisms of combustion which are not available for distillate fuels in addition to many assumptions that have to be made to determine the burning velocity. Such models take long periods of computational time for execution and have to be calibrated and validated through experimentation.

This paper presents a new technique to determine the burning velocity in a production engine without making any modification in its structure, or use of high speed imaging equipment. This technique is based on the combustion produced ionization measured at two defined locations in the combustion chamber. In the engine used in this investigation, the spark plug is used as an ion current sensor which indicates the time the flame kernel is formed around the spark plug gap. In addition, the fuel injector is used as an ion current sensor, after it is electrically insulated from the cylinder head. The time between the start of ionization at the two locations is used to calculate the burning velocity. The use of this technique to determine the cycle to cycle variation in the burning velocity and other combustion parameters is demonstrated with engine operation at a steady speed and load.