Prediction Of NVH And Heat Load Performance Of Engine With A Magnesium Cylinder Body

The lightweight has important influence on the power,the economy and the environmental performance of the automobile,which is one of the important directions of the development of the automobile.Magnesium alloy as a "green engineering materials in the 21st century",with a small density,specific strength and specific stiffness,damping and other characteristics,which is gradually increasing used in the automotive,plays an important lightweight role.But the magnesium alloy used in the engine and other high-temperature components is relatively rare.With the development of high-temperature magnesium alloy,magnesium alloy in the application of the engine is bound to be more and more.In the cylinder body,the largest engine parts,magnesium alloy applications will bring a significant weight reduction effect.Therefore,it is of great engineering significance and academic value to study the NVH performance and heat load performance of magnesium alloy cylinder body in advance.Based on the finite element method,boundary element method and fluid-solid coupling method,the NVH performance and heat load performance of magnesium alloy cylinder body are studied,and compared with the traditional cast iron cylinder body.The main contents include the following two aspects.Taking a vehicle as an example,the multibody dynamics model and acoustic model of the whole engine were established.The dynamic response of the cylinder body was calculated by multi-body dynamics.Surface radiated noise was calculated by sound boundary element method,and compared with experiment and simulation results of the cast iron cylinder body.The comparison shows that,under the same conditions,the surface vibration and the radiated noise of the magnesium alloy cylinder body engine will be larger than that of the cast iron cylinder body engine.The radiated sound power level of the whole engine is 108.1dB(A)and the radiated sound power level of cast iron cylinder body engine is 107.3dB(A).Although the NVH performance of magnesium alloy cylinder body is weaker than the cast iron cylinder body,but its weight is reduced by 75%.Based on the fluid-solid coupling method,the heat load of the magnesium alloy cylinder body was researched,including the temperature field,thermal stress and thermal deformation,and compared with the cast iron cylinder body.The comparison shows that,both the temperature distribution and thermal stress distribution are basically the same.The maximum temperature of magnesium alloy cylinder body is 519.03K,which is slightly lower than that of cast iron cylinder body,with a temperature 523.00K;the maximum principal stress of magnesium alloy cylinder body is 177.4MPa,the maximum principal stress of cast iron cylinder body is 202.2MPa,The minimum principal stress of the magnesium alloy cylinder body is 150.5MPa,the minimum principal stress of the cast iron cylinder body is 174.5MPa,which is 24.0MPa larger than that of the magnesium alloy cylinder body.The deformation of the magnesium alloy cylinder body is mainly distributed at the rear end of the cylinder body and the maximum deformation is 0.54mm;the cast iron cylinder body is mainly distributed in the cylinder surface and the maximum deformation is 3.27 mm.From the temperature field and thermal stress and thermal deformation,the mechanical property of magnesium alloy cylinder body is better than cast iron cylinder body.