Research Of Thermal-Mechanical Stress And Fatigue In LNG Engine Cylinder Head And Block

With the serious shortage of oil,Liquefied Natural Gas(LNG), which possesses higher calorific value and larger reserve scale, is becoming the most applied alternative fuel of engine. However, the combustion of LNG is relatively slow, resulting in high temperature of exhaust gas and thermal load of engine. The cylinder head and cylinder block need to be more reliability. Therefore, it is very important to simulate temperature, stress and fatigue of the LNG engine.This study take the LNG engine of DongFeng motor co. LTD as research object, carry out the CFD and FEA simulation, propose a way to couple thermal and mechanical stress, and conduct the structure strength and fatigue analysis of the engine. Based on maximum torque working condition, temperature simulation has been implemented. Main research content includes: one-dimensional work process simulation, three-dimensional combustion simulation, CFD analysis of cooling water jacket, fluid-solid couple analysis of the engine, finally, the stress analysis of thermal and mechanical stress, low cycle fatigue and high cycle fatigue analysis.The temperature comparison of the simulation and experiment shows that the simulation results are very accuracy. The highest temperature of the cylinder head is 330.3?, which appears around the spark plug and close to the area between the exhaust valves. Stress results show that the engine stress concentration is in the nose sections of the cylinder head, the largest stress appears between the two inlet valves, the maximum Mises stress is 328 MPa. Fatigue analysis results show that: at the nose sections of the cylinder head location, low cycle fatigue life and high cycle fatigue safety coefficient are low but still within the safety range of fatigue. In the future, it is suggested to improve the reliability of nose areas.