Experimental Study On The Heat Transfer Boundary Conditions Of The Piston Cooling Oil Chamber

The working process of diesel engine, piston parts of the harsh working environment, working conditions is the worst for reciprocating movement in the cylinder. The working reliability of diesel engine and the using durability, work largely restricted to piston. The piston working temperature is high, and the high speed sliding mechanical load is very high, and poor lubrication, which determines that it is subjected to strong wear, and may create a sliding surface galling, burns and other fault. Practical experience has shown, the piston life decides the diesel engine repair interval. In the high power diesel engine, thermal load of piston often limit the diesel engine strengthening potential of heat injury, precise analysis is a part of diesel engine design, strengthening process essential for piston.Need to carry out research on diesel engine piston thermal damage of a company in the course of work, an accurate assessment of the thermal state is the basis for design of thermal injury, how the heat transfer boundary conditions on the piston shaker cooling oil cavity determine precisely, become the restriction of diesel engine piston thermal state to determine the key problems and technical difficulties.The company intends to use the simulation calculation of piston thermal load, due to lack of experimental evaluation means necessary, verify it intends to carry out the piston oscillation oil cavity using piston oscillating cooling oil chamber test bed fluid solid heat coupling boundary conditions.Firstly, through building the piston cooling oil cavity oscillation test bench, effective flow related site measurement of piston temperature value and the piston oscillation of the oil cavity; then the piston oscillation oil cavity injection cooling CFD calculation, for verifying the accuracy of the simulation model through the effective flow piston oscillation of the oil cavity, the oscillation oil cavity heat transfer boundary condition hot air heating; CFD calculation on the top of the piston, through a piston cooling oil injection without temperature measured value to verify accuracy of the simulation model, get the top of the piston heat transfer boundary conditions; finally, through the empirical formula for skirt part of piston, piston ring and other parts of the heat transfer coefficient is set, solving the temperature field of the piston, through the comparison of the simulation results with the experimental results, verifying the accuracy of the piston cooling oil cavity oscillating heat transfer boundary condition, finally solve the thermal state of piston oscillation analysis of oil cavity in the process of heat transfer boundary condition setting problem.In addition, this paper not only through the piston cooling oil cavity oscillation test bench to solve the oil chamber piston oscillation fluid solid heat coupling analysis process of the oscillating oil cavity heat transfer boundary condition setting problem, but also in the experiment is also put forward several points of innovation. One is the design of double link thermocouple temperature measuring mechanism, can measure the piston to the high-speed movement of the temperature, and can ensure long-term and effective work and the thermocouple wire is not broken. The two is to build a piston shaker cooling oil chamber test rig based on a single cylinder diesel engine, simply and effectively solves the problem of dynamic balance of traditional test bench, and replace the piston bore with different oscillation of the oil cavity, in inner space limited single cylinder engine accurately and conveniently mounted injector nozzle.