Study on Thin Film Thermocouple for Measuring Instantaneous Temperature on Surface of Combustion Chamber Wall in Internal Combustion Engine

Abstract

The optimum thin film thermocouple in terms of materials, shape and dimensions has been determined as follows. Equations of different element method capable of determining the temperature distribution in such a thermocouple are introduced in order to obtain the temperature distribution by which the combustion gas temperature and heat transfer coefficient affect the thermocouple under steady state and unsteady state conditions. Further, effects of thermophysical properties and dimensions of materials constituting the thermocouples have been studied. On the other hand, thermocouples made of different materials and in different shapes have been trially produced and embedded respectively into the piston of a 4-stroke gasoline engine. Actual measurements of such thermocouples proved the validty of calculated results, and it has been demonstrated that the above mentioned thermocouples have an adequate durability under high speed/high load conditions.