A fast response thermocouple for internal combustion engine surface temperature measurements

A fast response thermocouple was developed for measuring surface temperatures of aluminum components in ICE combustion chambers. The key features of the design are the use of the aluminum substrate as one of the thermocouple metals and the use of a thick copper layer as the hot junction at the surface. The copper equalizes the hot junction temperature with the surrounding aluminum to correct for the differences in thermal properties between the two materials. FEA determined the optimum thickness of the copper layer to be between 100 and 125 μm. Under typical SI engine heat flux conditions, the thermocouple should be able to measure average surface temperatures within 0.19 °C and the magnitude of temperature swings within 6% of true values.Following the FEA, the optimized thermocouple was tested in a SI engine. Experimental results displayed the same trends as the FEA at measuring average temperatures and temperature swings, suggesting the thermocouple was performing as predicted.