Measurement of Flame Propagation Characteristics in an SI Engine Using Micro-Local Chemiluminescence Technique

A small Cassegrain optics sensor was developed to measure local chemiluminescence spectra and the local chemiluminescence intensities of OH*, CH*, and C2* in a four-stroke spark-ignition (SI) engine in order to investigate the propagation characteristics of the turbulent premixed flame. The small Cassegrain optics sensor was an M5 type that could be installed in place of a pressure transducer. The measurements could be used to estimate the flame propagation speed, burning zone thickness, and local air/fuel (A/F) ratio for each cycle. The specifications of the small Cassegrain optics sensor were the same as those used for previous engine measurements. In this paper, measurements were made of several A/F ratios using gasoline to fuel the model engine. The performances of two Cassegrain optics sensors were compared to demonstrate the advantages of the new small sensor by measuring the local chemiluminescence intensities of a turbulent premixed flame in the model engine. The measurements suggested that the small Cassegrain optics sensor is superior to the conventional Cassegrain sensor and can provide stable data for measurements over several hours, which should be sufficient for practical combustion diagnostics. This sensor proved useful for estimating the flame propagation characteristics. In addition, the sensor should be useful for local A/F ratio measurements in an engine cylinder.