Effects Of Mechanical Load On The Diesel Engine Cylinder Liner Deformation

With the global energy conservation and emission reduction becoming more stringent, the cylinder explosion pressure has been constantly increased, and this leads the mechanical and thermal loads of the friction pair of piston-cylinder-liner increasingly in a large degree. Cylinder liner is easy to deform influenced by cylinder head bolt preload, piston high-speed periodic reciprocating motion, and cooling unevenness and uneven of the stiffness of the diesel engine block. When the nature of piston rings to follow the liner can not compensate for the cylinder liner out of roundness, there will be an abnormal gap between the piston group and cylinder liner. This causes oil and gas leak, resulting in the combustion deterioration and the lube contamination. So it is important to improve the sealing performance between the cylinder-piston friction pair, to reduce oil consumption, to improve the friction properties, and to reduce the emissions that the cylinder liner deformed conditions is understood, and the cylinder liner and piston group deformation and out of roundness is controlled.The assembly coupling model of cylinder block-liner-head is established, and the deformation of the liner is analyzed under the cylinder head bolt preload, and the deformation of the block and bore is tested to verify the accuracy of the finite element model. Based on the cylinder liner deformation test, the influence of the mechanical loads, including the cylinder head bolt preload, bearing interference fit, main bearing cap bolt preload, cylinder firing pressure, main bearing load and piston sideswipe force, on the cylinder liner deformation and stress are calculated and analyzed. And the effects of structure factors on the expansion and compressive deformation of the cylinder liner, and the impact of the change in stiffness of the body on the cylinder liner deformation are studied by the orthogonal design method.The results are as follows.(1)The cylinder liner deformations affected by the cylinder head bolt preload, the cylinder explosion pressure and the main bearing loads and the cylinder head bolt preload is the main factor that affects the liner stress.(2)Based on the orthogonal experiment, the findings show that, the structure factors affecting the liner deformation are the depth of cylinder head countersunk that impacts most, the angle of the cylinder sleeve shaft shoulder positioning flange with the second place, and the length of head bolt engagement with minimal impact. And the optimal solution of the three structure factors is obtained.(3)The depth of cylinder head countersunk is closer to the cylinder liner shaft shoulder positioning flange, the radial deformation of cylinder liner is larger. With the increase of the cylinder liner the shaft shoulder Positioning boss angle, cylinder liner radial deformation present trend is to reduce the-Increase-Decrease, cylinder liner deformation minimum at an angle of20’.With the increase of the length of the cylinder head bolt engaging, cylinder liner radial deformation showing a gradually decreasing trend, but the very small the cylinder radial deformation amplitude variation. The structural of diesel engine block has changed, a first-order natural frequency of the body is enhanced20Hz, and the amount of the radial deformation and distortion of the liner is reduced in a certain extent after improving the diesel.