Abstract
In this study, simultaneous measurements of hydrocarbon fuel and carbon dioxide (CO_2) concentrations around a spark plug in the homogeneous-charge spark-ignition and the direct-injection spark-ignition engine by a spark plug sensor using infrared absorption technique were carried out. The new simultaneous measuring system including four optical fibers in an M14 spark plug was developed. It was possible that the simultaneous measurement of CO_2 and fuel concentrations in the homogeneous-charge spark-ignition combustion with methane-air or propane-air mixture. Behavior of initial flame kernel around the spark plug can be understood using hydrocarbon fuel and CO_2 concentrations around a spark plug.
