COMBUSTION-TORCH IGNITION - FLUORESCENCE IMAGING OF OH CONCENTRATION

The temporal and spatial development of the OH concentration during the ignition of a lean methane-air mixture ( phi equals 0. 65) by a combustion torch has been studied. In the experiment the combustion torch was formed by a jet of high temperature combustion product gases that exit a thin-plate circular orifice connecting a small cylindrical prechamber with the main combustion chamber. This starting jet was driven by a spark-ignited flame which propagates through the prechamber. By decreasing the diameter of the prechamber orifice the initial gas velocity of the combustion torch was systematically increased. The fluid physics of the combustion torch has a significant influence on its chemical structure and the development of the subsequent ignition process in the main combustion chamber. This work is pertinent to internal combustion engines.