活塞结构刚度对动力学性能影响的研究

用矩阵来描述活塞的径向刚度,并在试验台架上对不同位置加载,测得规定点处的变形量,从而确定活塞整体刚度的分布情况。利用建立的动力学模型分析活塞刚度变化对二阶运动、敲击动能及摩擦功损失等的影响,为确保活塞温度场、热变形及缸套安装变形等边界条件的准确性,使用硬度塞测温试验、缸孔轮廓仪等得到的实测数据对模拟过程进行标定和验证。计算结果表明:活塞动力学分析要同时考虑缸套和活塞刚度的影响,否则计算得到的活塞摆角偏小,摩擦损失偏大,而敲击动能则随着曲轴转角的不同而与实际情况产生周期性偏差,有些偏差值甚至会达到70%;改变活塞结构会改变活塞的刚度,通常当裙部刚度增大后,活塞在每个换向时刻的最大摆角会减小,同时在每个敲击时刻的敲击能量峰值也会减小。

Effect of Structure Stiffness of Piston to Dynamical Performance

In order to determine the stiffness distribution of a piston, a matrix was used to describe the piston radial stiffness, and a bench test was made to measure the piston deformations at specified points when loading was made at different positions. The effect of stiffness change on the secondary motion, kinetic energy in knocking and friction loss was analyzed by simulation. In order to ensure the accuracy of boundary conditions such as piston temperature field, thermal piston deformation and installed liner deformation, the simulation process was calibrated and validated by the measured data obtained with the hardness plug temperature test and liner profiler. The results show that a dynamic analysis must include the influence of liner stiffness and piston stiffness, otherwise the piston tilting angle from the simulation will be smaller and the friction loss will be larger than their actual values, and the kinetic energy in knocking will generate cyclical deviations at different crank angles, some deviations may even reach 70%; that the piston stiffness will change with the structure, and usually if the stiffness of skirt is increased, the maximum tilting angle at each turning point will become smaller and so will be the peak kinetic energy at each knocking point.