Abstract
Measurement of gas temperature in an internal combustion engine is very important for studying the combustion process. The measurement is, however, difficult and many methods, so far reported, are almost always tested in laboratories and have difficulties for practical application.
In the present study, a method for the temperature measurement by measuring the radiance of CO2-4.3μm band (CO2-4.3μm band radiance method) is proposed and experimentally investigated for the accuracy and precision. The method has been found to be applicable for measuring the gas temperature in practical engines.
The main findings are as follows.
(1) Spectral emissivity of CO2-4.3μm band, calculated from the statistical model, coincides with that experimentally obtained. It depends on the optical path length, total gas pressure, and CO2 concentration or partial pressure. The combustion gas, therefore, can not always be regarded as a blackbody even under high CO2 concentration.
(2) The radiance-temperature calibration curves for the combustion gas can be obtained by calculation.
(3) The calibration curves also depend on the optical path length, total gas pressure, and CO2 concentration. However, if the measurement is restricted to the gas in internal combustion engines and 2∼3% error is allowed for temperature calibration, the calibration curves can be regarded to depend only on the optical path length.
(4) It has been experimentally clarified that the engine gas temperature can be measured within ±10% accuracy.
(5) The method provides useful temperature information in an internal combustion engine, informative to the analysis of the combustion process.
