Research On Matched Deformation Of The Engine Load-carrying Structural Components

Cylinder head and cylinder block are important load-carrying structuralcomponents in an engine. Cylinder head and cylinder block deformation willinfluence the normal engine operation, such as the oil and gas leakage, loss of powerand so on. Thus it is quite necessary to consider the cylinder head and cylinder blockdeformation during the engine designing.With the development of computertechnology, finite element methods are widely used in cylinder head and cylinderblock deformation analysis.Engine design cycles and cost can be greatly reducedwhen finite element methods are applied.In this paper, finite element methods areused to analyze the cylinder head, cylinder gasket and cylinder block deformation.3D models of cylinder head and cylinder block are established in Pro/E software,and are meshed in Hypermesh software. After setting the loads and boundaryconditions, analysis is conducted in Ansys software.Conclusions can be made asfollows:Firstly, contact styles of bolts among the cylinder head, cylinder gasket andcylinder block are set close to the real engine conditions, including the bandingcontact and friction contactCylinder head, cylinder gasket and cylinder blockdeformations are analyzed when bolts are pretighted. nose bridges near the intake andexhaust duct and cylinder liner deformations are also analyzed.Conclusions can bemade that cylinder head, cylinder gasket and cylinder block deformations areinfluenced a lot by the bolts pretighting.Deformations in the intake and exhaust ductnose bridge are more obvious.Deformations of cylinder gasket is well-distributed andwhich can ensure the well sealing.Cylinder block deforms a lot at the place ofthreaded hole.Cylinder liner distortion is larger at the upper part and smaller in thelower part.The influence of cylinder bolts tightening sequences, bolts length, stiffness ofcylinder head and cylinder liner on the cylinder head, cylinder gasket, cylinder blockand cylinder liner distortions are analyzed which could provide the basis for thecylinder head, cylinder gasket and cylinder block desigining.The best bolt tighteningsequence for cylinder gasket sealing is to tighten the intermediate two bolts, and thenthe cross lateral bolt.The influence of bolts length on the cylinder head and cylindergasket deformation is that the deformation decrease when the bolts length gets smaller.However, engine normal operation will be influenced if the bolts length is toosmall.The increase of the stiffness of the cylinder head and block has much influence on the upper part of the liner deformation, while there is little influence on the lowerpart.Finally, thermal stress and strain on the cylinder head and the cylinder areanalyzed indirectly.Proper temperature boundary conditions are set in the finiteelement model and temperature field is calculated.Then the temperature field isloaded in the bolt preloaded structure model and the thermal stress results areachieved. Thermal deformation is analyzed and is compared with the one when onlybolts are preloaded Cylinder head, cylinder gasket, cylinder block and cylinder linerdistortions are analyzed when maximum explosion pressures are loaded in differentcylinders. Results are compared with the one when only thermal stress is loaded.The cylinder head thermal deformation trend is the central deformation largerthan the both sides, and the exhaust side has larger deformation, small deformation ofthe intake side.Cylinder block and cylinder liner distortions are bigger on the top andsmaller in the bottom. When maximum explosion pressure is loaded on thecombustion chamber under steady-state conditions, the cylinder deformation getssmaller while other cylinders show little change.