Gas temperature measurement by laser interferometry (Application for measurement of absolute value of temperature in internal combustion engine cylinder)

A fiber optical interferometer system which was previously reported was used. The reported method was useful for measuring only the temperature change. However, in this study, absolute value of temperature could be measured by changing the density of the reference gas according to the density change of the test gas. After confirmation by temperature measurement in a constant-volume vessel, this method was applied to measure the gas temperature in a specially designed spark-ignition engine cylinder. The measured temperature satisfactorily agreed with the value obtained using a resistance wire thermometer. By combining this method with the method reported previously, the absolute value of gas temperature in an engine cylinder can be measured.