Development of Coaxial Type Thin Film Temperature Sensor with Improved Measurement Accuracy Based on Principle of Thermoelectromotive Force

摘要

In order to verify cooling loss reduction effect of internal combustion engine, method for measuring wall surface temperature and heat flux with high accuracy is required. Various methods have been proposed for measuring the cooling loss from the combustion gas to the combustion chamber wall, newly coaxial type thin-film temperature sensor was developed for wall temperature and heat flux measurement by the authors. This sensor consists of thin-film and body and center wire have three junction positions in the case where three materials are different. Therefore, it is necessary to use the same materials for thin-film and body or thin-film and center wire to make two junction points. In this study, sputtering method that can be formed various kinds of alloy materials and film thickness of 0.1～1μm on the sensor surface was chosen. It was evaluated the influence of differences in thin-film material on wall temperature and heat flux measurement by numerical analysis, as a result, the surface of sensor body (the same material as the combustion chamber) was hot junction by using the same material for the thin-film and center wire, it was suggested that high accuracy measurement is possible. And the sensor was attached to the cylinder head of test engine using hydrogen as fuel and conducted experiments, and it was obtained the similar results as the numerical analysis results. From these result, it was found that possible to measure high accurately surface temperature and heat flux by forming a thin film of the same material as center wire in the case where the sensor body was used the same material as the combustion chamber.