Scheme Design Of A Thermal Load Simulation Tester For Piston And Optimization Of Cooling System

As internal combustion engine constantly develops into high strength,the reliability of its overall unit and heated parts is facing severe challenges. Especially when it comes to piston working under the conditions of high temperature and pressure and bearing alternating mechanical loads, it suffers from thermal fatigue damages with high probability, to deal with which depends on systematic researches on thermal damage mechanism. Numerical simulation can figuratively mimic the temperature distribution of piston, whose precision relies on boundary conditions and calculation results should be validated by experiment. Therefore a simulation test-bed was designed to predict temperature field of piston, not only offering boundary conditions to numerical simulation, but validating simulation results.Firstly overall schemes of test-bed were designed. Based on the study on the existing thermal fatigue test-beds at home and abroad, with the reality and conditions of this subject taken into account, two overall schemes were designed, which were analyzed comparatively, and consequently the second one was adopted.Then heating, cooling, temperature detecting and safety alerting systems were independently designed, whose main content is fully described as follows. With the analysis comparatively of different methods to heat piston, the method that the flame directly heats piston was adopted after integrated consideration, which took combustor as the heat source. And plate heat exchanger was chosen, with running conditions and advantages and disadvantages analyzed. According to working environment and measure precision, K-thermocouple was adopted to measure temperature. Six kinds of safety alert reminders were designed to secure human life and property.And design calculation of test-bed cooling system was conducted, to obtain selection parameters of main units, like exchanger, pump and pipes.Finally a cooling system model was built by AMEsim and Matlab. Simulation results show that the cooling system is applicable to pistons of different power, but to reach steady state, it takes cooling system longer time, and cooling water and engine oil inlet temperature different time, so the effects of total pipe pressure, efficiency and working area of heat exchanger on the time of cooling system costs to reach steady state was analyzed by numerical simulation, whose results indicate that higher total pipe pressure, higher exchange efficiency and larger working area will lead to less time and smaller difference of time to reach steady state. Based on the conclusions described above, parameters of cooling system were optimized and the third scheme was offered. Simulation results of the third scheme show that optimization index is satisfied when total pipe pressure is 0.19 MPa and working area of engine oil heat exchanger is set as 0.9m2. Though proposed under the condition of maximum piston power, the optimized scheme is applicable to pistons of different power, which is verified through simulation by changing power of piston.