We have developed a local three point heat flux measurement system with the MEMS (Micro-Electro-Mechanical-System) technology for the internal combustion engines. The heat flux sensor of three tiny thermometers of 315 μm square has measurement frequency of 10 kHz. The sensor was designed to observe turbulent heat transfer in the engine. The three tiny sensors enable to reproduce heat flux vector on the sensor surface flush to the engine inner wall. The developed sensor was composed of an Al alloy substrate, an Al_2O_3 insulation layer, Pt sensing layer and an Al_2O_3 passivation layer for improving the durability of the thin film sensors. The wall heat flux in the engine is derived by taking surface temperature change with the Pt sensor and analyzing the heat conduction inside the sensor with the temperature as the boundary condition. Performance test of the sensor was conducted in a laboratory engine of SIP, Cross-ministerial Strategic Innovation Promotion Program in Japan. The instantaneous heat flux with peak of 2.0 - 2.8 MW/m~2 with a noise level of 8.4 - 8.7 kW/m~2 was measured at 2000 RPM. Since the sensor can clearly measure the instantaneous value, remarkable variation among each cycle was confirmed. Simultaneous three point heat flux measurement also enable to visualize the local heat transfer in the three dimensional heat conduction analysis.
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