柴油机曲轴运转的非线性振动与混沌

通过对柴油机曲柄(曲轴)连杆机构作运动和受力分析，将其受力简化为气体膨胀的瞬间作用力和柴油机运转的惯性力，且均假设为集中荷载。因此曲轴运转的力学模型也可简化为：气体作用力为转子周期性脉冲力；惯性力为转子-轴承系统的力。这两个力学模型都存在非线性振动，且在一定条件下产生混沌现象，这从理论上解释了柴油机曲轴的运转能产生非线性振动和混沌。同时本文还应用功率谱法来研究混沌性态。在实例分析中，我们通过对8NVD2U-48A柴油机主轴承对应的机体上布采样点，对表面振动信号进行采样且对采样进行功率谱分析，其结果说明上述结论在理论上是正确的。这一结论也为柴油机曲轴和主轴承的故障诊断提供了理论基础。

On the Nonlinear Vibration and Chaos of Diesel Engine Crankshaft in Running

In this paper,the force exerting on diesel engine crankshaft is simplified as transient force which is produced by gas expansion and inertial force which is produced by diesel's running,and both of them are assumed to be concentrated load.So that,the mechanics model of running crankshaft can be simplified to include two forces:periodical pulsating force created by gas and inertial force. Both forces contain nonlinear vibration and,in certain conditions,produce chaos phenomenon.This explains theoretically that crankshaft of diesel engine in running produces nonlinear vibration and chaos phenomenon.Meanwhile,power spectrum method is used to research nature and mode of the chaos.Diesel 8NVD2U 48A is taken as an example and analyzed.In the example,sampling points are placed on main bearing seats.Surface vibration signals are acquired and analyzed in power spectrum method.Results show that the conclusion above is theoretically correct.This result could provide theoretical basis for trouble diagnosis of crankshaft and main bearings of diesel engine.