Research On Transient Temperature Testing Technique For Piston Surface Of High-speed And Large-power Diesel Engine

The piston is one of the key components to bear the heat load in the high-speed and large-power diesel engine.The thermal load rule of diesel engine piston can't be fully grasped by designers,because of the terrible working environment and the fast reciprocating motion characteristics of the diesel engine piston.The common methods to measure temperature of piston surface is limited by the response speed of sensors and the harsh working environment of pistons,so it is difficult to accurately measure and monitor the transient temperature of the surface.In regard to the technical problems for measuring the transient surface temperature of diesel engine piston with high-speed and large-power,the main contents of this research are as follows:Based on the theories of thermal analysis and finite element analysis,the ways of heat transfer,the control equations of thermal analysis,the finite element methods of thermal analysis and the boundary conditions of thermal analysis are studied.The solid model of the piston is established by using the 3D modeling software Creo3.0.The solid model of the piston is meshed by using the finite element simulation software of ANSYS15.0.The thermal boundary condition of the piston steady temperature field is calculated by empirical formula and then the distribution cloud of piston steady temperature field is obtained through numerical simulation.A thin film temperature sensor with the characteristics of fast response,accurately measurement and easy to installation is developed,which can be applied to the transient surface temperature measurement of diesel engine piston with high-speed and large-power.The DC pulsed magnetron sputtering technology is applied to deposit NiSi functional thin film and SiO2 insulating thin film on the surface of ceramic substrate embedded with NiCr-NiSi parallel electrode wires.The static performance of developed sensor is studied by utilizing a self-developed static calibration system.Experimental results show that prepared sensor has good linearity and thermal stability in the range of 50 to 400?.The Seebeck coefficient is 41.2?V/? with a nonlinear error less than 0.05%,which remains stable with the change of NiSi film thickness.The prepared temperature sensor has a microsecond response time and it increases with the increasing of NiSi film thickness and has little effect with the change of energy of laser pulse.The principle of thermocouple cold junction compensation and temperature conversion of MAX31855 is studied.The transient surface temperature acquisition system for the piston based on STM32 is developed by utilizing ZigBee wireless transmission technology,which realizes the function of cold end compensation,data acquisition and wireless transmission of the thin film thermocouple sensor.The sampling speed for transient temperature measurement can reach 30S/s.The real-time monitoring system for transient surface temperature of piston based on C/S architecture is developed through Visual Studio 2010 software development platform by using C#programming language.The user information module,data monitoring module,data processing module and database module are designed.The piston temperature test system is verified by test,which provides reliable technical support for the target to accurately measure and real-time monitor transient surface temperature of diesel engine piston with high-speed and large-power.