Research On Thermal Load And Influence Law Of Heated Parts Of Engine

The thermal load of the heated parts is of great significance to the design and service life of the engine.With the increasing power of the diesel engine,the thermal load is also greatly increased.Heated parts in the combustion chamber withstand high thermal load for a long time,having a great impact on the mechanical properties and anti-deformation ability of the material,thereby causing thermal fatigue or directly affecting the performance of the engine.The main heated elements include piston,cylinder liner and cylinder head,so this paper mainly establishes a thermo-fluid-solid coupling model for these three elements to obtain an accurate temperature field.In this paper,the two-phase flow oscillating heat transfer is used to obtain the cooling boundary conditions of the piston,the iterative mapping of the fluid-solid is used to eliminate the initial boundary condition errors,and the simulation of the temperature field is verified by the hardness plug experiment.It is believed that the increase of the air-fuel ratio in the cylinder or the delay of fuel injection will reduce the overall temperature of the piston.The filling rate of the cooling cavity of the piston will decrease as the engine speed increases or the cooling oil injection rate decreases,and the higher the filling rate is not the better the cooling effect.At the same time,the amount of deformation at different cross-sectional positions of the cylinder liner under the thermal-mechanical coupling is extracted,and the characteristic equation is used to fit it.The second-order deformation is considered to be relatively large.And the effects of various stages of deformation on engine performance such as oil consumption and wear are discussed.It is believed that with the increase of deformation,the amount of blow-by gas and wear-rate increases,and the overall change in oil film thickness is small,while the oil consumption is increased first and then decreased,and the cooling boundary of the original machine is optimized,so that the deformation of the cylinder liner is reduced,thereby reducing the amount of piston blow-by gas and lube oil consumption.In this paper,the stresses of the circumferential nodes at different positions of the cylinder head under the thermo-mechanical coupling are extracted,and the thermal stress is considered to be dominant,and the thermal fatigue analysis is carried out.The calculated low-cycle fatigue has a low safety factor,so the low-cycle fatigue caused by thermal load is often the main cause of cylinder head failure.