识别运行状态下内燃机曲轴角振动模态参数的新方法

A New Method for Identifying Angular Vibration Modal Parameters of IC Engine Crankshaft in Operating Condition

提出了基于停缸法识别运行状态内燃机曲轴角振动模态参数的一种新方法。基于线性叠加原理,将某缸单独工作引起的测点角振动表示成多个模态角振动的叠加,并推导出当曲轴在该缸的某谐次简谐力矩作用下发生某一种振型的振动时,此时测点角振动近似表现为该模态角振动。对某6240柴油机的仿真研究结果表明:利用停缸法得到的测点角振动位移频响曲线,可识别内燃机曲轴角振动第1、2阶模态参数(固有频率、阻尼比和振型),且各阶模态振型和固有频率与自由振动计算结果相当接近,最大误差仅为2%。

A new method for identifying the angular vibration modal parameters of IC engine crankshaft in operating condition was proposed. According to the linear superposition principle, the angular vibra- tion of measuring point produced when a cylinder was operating separately, was expressed as the superposition of multi-mode angular vibration, and then it was derived that the angular vibration of measuring point could be considered as the mode angular vibration when the crankshaft resulted in a kind of mode angular vibration by the action of a certain order harmonic moment of the cylinder. The simulated results for a 6240 diesel engine show that the displacement frequency response curve of angular vibration in measuring point obtained by misfiring method can be used to identify the modal parameters （natural frequency, damping ratio and vibration mode） of the first and second order, and the modal natural frequency and vibration mode of both orders are close to the results of free vibration calculation considerably, the maximum error is only 2%.