Vibration signal of internal combustion engine is excited by the cylinder pressure and other excitations. The response signals caused by different excitations couple together in the time domain and frequency domain, which makes it difficult to extract combustion information from vibration signal. To determine the main excitation sources and the contribution level of the most important excitation that contributes to the vibration in a 2-cylinder diesel engine, the ratios of the maximum value of displacement, velocity and acceleration caused by the non-combustion excitations to those caused by the cylinder pressure are calculated. And a cylinder head-body finite element model of an SD2100TA diesel engine is established to analyze the characteristics of different excitations such as reciprocating inertial force (RIF), piston slap and main bearing load (MBL). According to the analyzed results, the excitations that play a major role on the vibration signal is determined. In addition, the coupling relationship of the excitations is evaluated. The simulation results show that the RIF is the most important excitation in the vibration signal. Finally, the contribution level of the RIF is calculated with the partial coherence function. Results show that the contribution level increases significantly with the increase of the rotation speed and remains basically unchanged with the increase of the torque.

内燃机的振动信号由气缸压力和其他激励来激励。由不同激励引起的响应信号在时域和频域耦合在一起，这使得很难从振动信号中提取燃烧信息。为了确定主要的激励源以及对引起两缸柴油机振动产生影响的最重要激励的贡献水平，应将非燃烧激励引起的排量，速度和加速度最大值与所引起的最大排放量之比由气缸压力计算得出。建立了SD2100TA柴油机的气缸盖体有限元模型，以分析往复惯性力（RIF），活塞拍击和主轴承载荷（MBL）。根据分析结果，确定在振动信号中起主要作用的激励。另外，评估了激励的耦合关系。仿真结果表明，RIF是振动信号中最重要的激励。最后，使用部分相干函数计算RIF的贡献水平。结果表明，贡献水平随着转速的增加而显着增加，而随着扭矩的增加而基本保持不变。仿真结果表明，RIF是振动信号中最重要的激励。最后，使用部分相干函数计算RIF的贡献水平。结果表明，贡献水平随着转速的增加而显着增加，而随着扭矩的增加而基本保持不变。仿真结果表明，RIF是振动信号中最重要的激励。最后，使用部分相干函数计算RIF的贡献水平。结果表明，贡献水平随着转速的增加而显着增加，而随着扭矩的增加而基本保持不变。