Research On The Surface Transient Temperature Test Of The Diesel Engine Piston Based On Thin Film Thermocouple

With the rapid development of science technology and the increasing requirements of people, each country’s internal combustion engine designers and major manufacturers are trying to accelerate the speed of the research and development of high speed and high power diesel engine of new products. In the process of new product design, a large amount of the thermal load analysis and research was carried out on the heated component is very important, especially the piston. Measuring the actual temperature of piston in the working process is the most intuitive means to understand the condition of the piston heating. Because of the piston working in harsh, special environment, the current ordinary temperature sensor has been difficult to meet the requirements. Thin film sensors developed in this paper, not only lay the theoretical foundation for the subsequent piston thermal load analysis, but also provide reliable reference data for the new product development of high speed and high power diesel engine.First of all, according to the temperature field finite element analysis theory and the piston thermal analysis theory as the basis; Established entity model of piston, used the COSMOSWorks software division unit grid, the finite element analysis on the steady temperature field of piston got temperature distribution; Then, combined with the principle of thin film temperature sensor and the sensor design experience, in line with the perfect, the optimization design idea. Ensure the sensor sensitivity, linearity, response speed and stability, designed transient temperature measurement film sensor, has small structure size, more suitable for field measurement; Designed NiCr/NiSi wire fixed bracket, used high-temperature sintering technology to prepare different number of ceramic wire element; Designed ceramic wire components element clamping piece and the fixed plate, used pulsed DC magnetron sputtering and RF bias technology, controlled film deposition time, prepared three groups of NiSi thin film on the end face of each ceramic wire element, the formation of hot junction with NiCr wire, reused the reaction of pulse magnetron sputtering and RF bias method preparation Si3N4 protective film, finally complete sensors; To observe the surface morphology of ceramic wire element, to characterize NiSi film of the sensor; Finally, the research on static and dynamic calibration were carried out on transient temperature measurement thin film sensor.The thickness, surface morphology and composition of NiSi films were respectively characterized by profiler, scanning electron microscope and energy dispersive spectroscopy. Static and dynamic calibrations for the developed thin sensor are carried out by the development system designed by ourselves. It is concluded that the thin sensor’s Seebeck coefficient at 50°C~400°C range is around 41.5μV/K, the nonlinear error is less than 0.38%, and has nothing to do with hot junction size, film thickness, high repetition rate, stable and reliable. When the hot junction film thickness is 307 nm, the shortest response time is 23.5μs.The smaller the film thickness of the hot junction, the smaller the time dynamic constant of thin film temperature sensor, but regardless of the hot junction area.