| The off-road diesel engine has been developing fast in recent years.On the one hand,it has a wider power range,a more complex and diverse structure and thus,a broader range of application compared with on-road diesel engine.On October 1,2015 in our country started the road with the diesel engine ? emission standards.The improvement of emission regulations for diesel engine using higher injection pressure and electric control technology to strengthen the diesel engine.Coupled with poor working conditions,the impact vibration is big,poor cooling effect makes the road such as diesel engine under the condition of working long hours under high heat load,it is easy to cause damage to cylinder head and other parts,affect the engine performance.Therefore,investigation of thermal loads on cylinder head is of great significance to improving overall performance and reliability of the engine in the engineering design of the ICE.The paper takes a non Road four valve turbocharged diesel engine as the research object,using the method of hardness plug test cylinder head temperature field measurement and calibration,temperature,flow rate of cooling water jacket outlet parameters such as the boundary conditions of numerical calculation;The coupling finite element simulation model of cylinder head cylinder assembly is established.The fluid solid coupling calculation and analysis of the cylinder head and the cooling jacket are carried out,and the coupling calculation and analysis are carried out.The results are as follows:(1)The temperature field of the cylinder head of the diesel engine was measured by the hardness plug method in the calibration condition and the maximum torque condition.The test results show that the two conditions temperature distribution is basically consistent,high temperature area is located in the exhaust valve between the nose region,the highest temperature under the same condition of the 3 cylinder up to 1 cylinder 3-5?,the highest temperature is higher than the rated maximum torque of 5?;temperature distribution in large part 200-300?,the highest temperature in the condition of third cylinder exhaust valve calibration between the nose area,the temperature is 337.5?.(2)By establishing a finite element "cylinder-block-cylinder pad-cylinder bolt-cooling water jacket" model,the calculated calibration of the steady temperature field with different condition of the cylinder head(preload conditions,heat load,working under the head of the outbreak)stress and deformation results.Results show that high temperature regions of the cylinder head are mainly in combustion surface of each cylinder:especially,the third cylinder of the bridge zone between exhaust valves endures the highest thermal load,reaching a temperature of 321.81 ?.And maximum stress can reach up to 300.43MPa,while maximum deformation at 0.458mm.(3)Structural optimization of water cooling jacket in the original cylinder head was accomplished.Results show that optimum schemes could dramatically improve flow characteristics of the cooling jackets and reduce thermal loads of the cylinder head.To be specific,the average velocity of the overall cooling jacket in cylinder head increases from 1.38m/s to 1.44m/s.the average velocity of flows near cylinder head plate increases from 1.081m/s to 1.092m/s.average heat transfer coefficient of surfaces of the cooling jacket goes up from 8906W(m2·K)-1 to 9065W·(m2·K)-1.Highest temperature of bridge zone in cylinder head falls from 321.81 0C to 312.69?,by 9.12?.maximum stress decreases from 300.43MPa to 277.72MPa,by 22.71MPa.And max deformation also drops from 0.458mm to 0.447mm,by 0.011mm?... |
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