Thermal Mechanical Coupling Analysis Of Valve Train Clearance Of 265 Diesel Engine

The valve mechanism is an important part of the diesel engine,and the reasonable gaps of the components directly affect the stable performance of the diesel engine.The failures,such as pulling cylinders,pistons hitting the valve,and the valve striking the valve arm,are caused by the unreasonable gaps.These failures make the diesel engine can’t work normally.Therefore,it is very necessary to analyze the reasonable gaps between the components of the diesel valve mechanism.The 265 diesel engine is taken as an example to analyze the diesel engine valve mechanism,using Creo 3.0,Ansys Fluent 19.0 and Ansys Workbench 19.0 software.The gas temperature field in the cylinder is analyzed by using the combustion engine temperature method.The gas flow rate,gas temperature,wall temperature,heat flux density and pressure distribution law are obtained.The temperature field of the cylinder wall is used as the boundary condition to analyze the temperature field of the gas distribution component.And then the temperature field of the component obtained by the analysis is used as the boundary condition.Thermal-mechanical coupling analysis of the valve mechanism is divided into three working conditions,i.e.,intake,exhaust,compression and explosion.The equivalent stress,strain and deformation of the component are obtained.Finally,according to the deformation of the component obtained by the thermal-mechanical analysis,reasonable gaps of the piston and cylinder liner,piston and valve,valve and valve arm should be reserved under cold conditions are gained.The analysis results state that:(1)The maximum gas flow rate in the cylinder is 397m/s and the maximum gas temperature is about 1387℃.The maximum wall temperature is about581℃and the maximum heat flux density is 99.47 W/m~2.The maximum pressure in the cylinder under intake and exhaust conditions is about 0.174MPa,the average pressure on the inner wall of the cylinder is 0.139MPa,and the factory test data verify the reliability of the analysis results;(2)Under intake conditions,the maximum stress is 358.88MPa,it is located on the end surface of the crankshaft.The maximum deformation is 1.9975mm,it is located on the top surface of the piston.Under exhaust conditions,the maximum stress is 358.88MPa,it is located on the end surface of the crankshaft,and the maximum deformation is 1.9975mm,it is located on the top surface of the piston.Under compression and explosion conditions,the maximum stress is 778.06MPa,it is located on the middle of the connecting rod.The maximum deformation is 5.0722mm,it is located at the top of the connecting rod;(3)The reasonable gap to be reserved under the three groups of components in the cold state are obtained:Gap of piston and cylinder liner is larger than 0.9978mm,piston and valve is larger than 2.4908mm,intake valve and intake valve arm is larger than 0.3129mm,exhaust valve and exhaust valve arm is larger than 0.4256mm.The calculated reasonable gap between the piston and the valve,the valve and the valve arm have been used in the actual debugging of the diesel engine in the factory.The practical application of the factory has proved that the analysis results in this paper are reasonable and reliable.This issue proposed a method to calculate the temperature field of the cylinder wall surface by using the combustion simulation method.This method provides a new way to analyze the temperature field of the diesel engine.At the same time,the components gap obtained by this method has been applied in factory practice.Their applications prove the results have certain reference value for the design and application of diesel engines,and provides relevant basis for the optimal design,manufacturing and installation of the valve mechanism.