Research On The Effect Of Local Structure Of Cylinder Head Cooling Jacket On Fatigue Strength

As one of the most important heated parts of combustion chamber in internal-combustion engine, cylinder head is prone to fatigue failure because of high temperature, high mechanical constraints and the periodic stress. This paper mainly explored the effect of cylinder head local structure on temperature field distribution and high-cycle fatigue strength by means of numerical simulation. Then it proposed one structure optimization scheme. The following works has been completed in this paper:1. Established the single cylinder model based on a six-cylinder model. After meshing and applying flow and heat transfer boundary conditions, the temperature field distribution was obtained. Comparing the calculated results with the temperature measurement experiment, it proved the validity of the calculation model.2. Applied the mechanical load and periodical stress on the single cylinder model, with the temperature field calculated before, high-cycle fatigue failure area was obtained by thermal-mechanical coupling calculation. Then the structure parameters were formulated and the optimal level was determined.3. Based on the calculated model, this paper demonstrated that temperature field distribution didn’t change significantly when the structure parameters varied with a series of levels.4. Applied the temperature field distribution calculated by the first step to different levels of structure parameters separately, this paper showed that thickening the rounded corners of two inlet valves water jacket can significantly increase the high-cycle fatigue safety factor individually. However, for the other outlet valve which suffered from tensile stress, thickening the rounded comers of water jacket can significantly decrease the high-cycle fatigue safety factor, which had an adverse effect on the fatigue strength of cylinder head.5. Multiple factors structure optimization result showed that there can be one structure optimization scheme. By thickening the rounded comers of two inlet valves by 0,8mm, thickening the rounded corner of the other outlet valve which suffered from tensile stress by 0.2mm, the high-cycle fatigue safety factor of the easy failure area could be increased significantly.