Study On IC Engine Flame Temperature And Soot With Two-color Method

Optical engines and related optical measurement methods have been important ways to study the combustion process in the automotive engines. Two-color method is an optical method to analyze the distributions of the flame temperature and the soot concentration in Diesel engines. The optical methods can help us understand the mechanism of the combustion and emission formation more thoroughly. In this research, firstly different kinds of optical methods and their theories and some key technical issues are presented, based on thorough literature survey. An optical engine was built on the basis of a single-cylinder Diesel engine. And the data collection system, the high-speed digital camera and the synchronization control system were completed to make up a whole optical engine test bench. Two key problems were solved: to match the combustion images with the crank angles and to prevent the gas leaking through the aperture between the quartz and the piston. Software was written to realize the Two-color method on the digital images with matlab language. The functions include inputting/outputting the images, calculating the temperatures and KL factors, enhancing and smoothing the output images. Another part of this research is experiment. Firstly the Two-color method system was calibrated. The Ta=f(I) curves were gotten by using the black body furnace as the standard radiation source. Then temperatures of a steady acetylene flame, calculated separately by the three RG, RB, GB modes, were compared with the temperatures measured by a B type thermal-couple to study the precision of the system. The results show that the biggest error among the three modes is lower than 3.67%. The test results on the real Diesel engine flame showed that RG mode had the advantage of calculating the low temperature flame and the GB mode had the advantage of calculating the high temperature flame. The combustion characteristics and soot reducing effect of the ethanol-diesel blended fuels were studied as the application the system. The results showed that with the increase of ethanol, the areas of the flames, the mean flame temperatures and the KL factors decreased, which indicated that ethanol can suppress soot formation and is beneficial to the soot oxidation during the late period of the combustion process.