Measurement of Diesel Combustion by Optical Fiber Thermometer (1st Report, Combustion Process and Exhaust Emission Level)

A combination of an optical fiber thermometer (OFT) and a beveled-edge-type light pipe sensor was used to measure flame temperature and soot concentration accurately in a DI diesel engine combustion chamber through a simple and easy procedure applying an infrared two-color method. The influence of sensor contamination due to combustion on the OFT output was examined and the appropriate correction method was applied for compensation of the decreased OFT output. The changes in combustion temperature and soot concentration were measured and compared with the exhaust emission levels by varying parameters such as engine speed and torque, fuel injection timing and suction air temperature. As a result, it was shown that this measuring technique is useful and effective in evaluating the combustion process in a diesel engine.