Spark-Induced Breakdown Spectroscopy In A Direct-Injected Natural Gas Spark-Ignition Engine

The purpose of this study is to investigate the fuel concentration around the spark plug obtained using spark-induced breakdown spectroscopy (SIBS) method with the spark plug with an optical fiber in the direct-injected natural gas SI engine. Effect of exposure duration on measurement accuracy of fuel concentration was discussed. Equivalence ratio around the spark plug in the direct-injected natural gas SI engine were measured under different natural gas injection timing. When the exposure duration is shortened, the emission of potassium elements near the emission wavelength of oxygen elements can be suppressed, and the measurement accuracy in the calculation of the emission intensity ratio can be improved. The relationship between the luminescence intensity ratio of hydrogen and oxygen (Hα/O) and the equivalence ratio of homogeneous mixture of natural gas and air was investigated and it was found that there was a positive correlation between the luminescence intensity ratio of hydrogen and oxygen (Hα/O) and the equivalence ratio. As a result of measuring the equivalence ratio around the spark plug of direct-injected natural gas SI engine using the SIBS method, an equivalence ratio of 0.67 was measured for a set value of 0.8 using the luminescence intensity ratio of hydrogen and oxygen.