往复式发动机振动特性建模与分析

Modeling and Analysis of Vibration Characteristics of a Reciprocating Engine

在标定工况下的往复式发动机是一个复杂多变的动态系统。其内部惯性力系中的不平衡力、力矩是引起发动机振动和噪声的主要激励源。单缸发动机对一阶往复惯性力、二阶往复惯性力的稳态响应分别为两个振动方向相同、初相位不同、频率之比为1∶2的倍频谐振动;其合振动是复杂的周期振动。而采用平面对称曲轴的直列四缸发动机的作用力矩的基频等于曲轴回转角速度的一半,整机二阶往复惯性力为单缸机的四倍,其稳态响应是简谐振动。对发动机进行动力学分析,了解其振动特性,并采取适当的减振措施,有助于改善整机的工作性能。

A reciprocating engine under calibrated working conditions was a complicated dynamic system with varying inertia. Unbalanced initial inertial forces and moments were main excitation resources of engine vibration and noise. As to a single cylinder engine, the steady- state responses to reciprocating inertia, 1 st and 2nd order, were two frequency doubling harmonic vibrations, which had the same orientation, different initial phases, and the frequency ratio 1 ： 2. Nevertheless, the fundamental frequency of the applied torque to a straight - four one with a symmetric crankshaft coincided with half speed of the crankshaft, and its steady - state response to reciprocating inertia with four times amplitude related to one applied to a single cylinder engine, 2nd order, was harmonic vibration. Carrying out dynamics analysis, exploring vibration characteristics of an engine and taking proper measures against vibration, it helped to improve machine periormance.