论文部分内容阅读
中速柴油机气缸盖两个相邻阀座孔之间的火焰面经常出现裂纹,在大多数情况下,这种现象被认为是由热疲劳造成的,因此必须对热应力值进行较精确的计算,目的是建立气缸盖强度的设计方法。然而由于气缸盖结构复杂,有关应力分析的例子较少。为了掌握作用在气缸盖火焰板热应力的情况,用二维和三维有限元法对一只四气阀、双层底气缸盖进行了应力分析,分析结果如下:(1)通过气缸盖的二维简化模型对竖撑板,中间隔板、火焰板的热应力状态以及阀坑位置与热应力的关系进行了定性分析。(2)排气阀座孔之间跨接部分的热应力最大。这一现象能很好说明气缸盖开裂现象。(3)由于气缸盖周壁的约束,因此只要通过燃烧室表面平均温度 T_m 和修正系数 K 的算术平均值的简单方程就可以估算出气缸盖的热应力。(4)计算得到的热应力值用气缸盖火焰面的残余应力测量值加以验证。
In most cases, this phenomenon is considered to be caused by thermal fatigue, so the thermal stress value must be calculated more accurately , The purpose is to establish the design method of cylinder head strength. However, there are few examples of stress analysis due to the complicated cylinder head structure. In order to grasp the thermal stress acting on the flame plate of the cylinder head, the stress analysis of a four-valve and double-bottom cylinder head was carried out by two-dimensional and three-dimensional finite element method. The analysis results are as follows: (1) Dimensional simplified model is used to qualitatively analyze the thermal stress state of the riser, the middle partition and the flame plate as well as the relationship between the position of the valve pit and the thermal stress. (2) The thermal stress of the bridging part between the exhaust valve seat holes is the largest. This phenomenon can well explain the phenomenon of cylinder head cracking. (3) Due to the constraint of the circumferential wall of the cylinder head, the thermal stress of the cylinder head can be estimated simply by a simple equation of the arithmetic mean of the average surface temperature Tm of the combustion chamber and the correction factor K. (4) The calculated thermal stress value is verified by residual stress measurement on the flame surface of cylinder head.