This paper describes the investigation of the mechanisms of engine front noise generation and the corresponding countermeasures employed in the development of a diesel engine. According to the analysis of acoustic signals and vibration signals measurement, an investigation of the noise source identification in a diesel engine is presented, and that the noise level of the diesel is comprehended. With the sound intensity method, the major sources of the exterior radiation noise of the engine front are surveyed. The research provides the reliable basis for the engineering practice to reduce vehicle noise level. Furthermore, the measuring data of the acoustic signals are compared by measuring noise from surface vibration, and the results are valid.

A non-linear dynamic model of one type of high-speed rotor system with gas supporting system is set up. The laws between the capacity force and the parameters of bearing, the static equilibrium position and rotating speed are studied on the basis of above model. Then, the failure rotating speed is given in the working state, and the relation between the minimum failure rotating speed and clearance ofbearing is also studied. At last, the stability and failure condition are discussed in different working conditions.

The torsionaI oscillation characteristics on the bending and torsioh coupled vibration of ro. tary shaft system were investigated using the elasto•-dynamic theery and other mathematic meth-ods, such as difference approach, Fourier transfOrm. and wavelet transform. It iS concluded that　mass eccentricity and other exciting modalities affect the bending and torsion coupled vibration of ro. tary shafts. TorsionaI vibration caused by bending vibration features linearity along with the change　of amplitude of bending vibration. Meanwhile, energy spectrum concentrates on high frequency are-a with the wavelet analysis.

The vibratory and acoustic behaviour of the internal combustion engine is a highly complex one, consisting of many components that are subject to loads that vary greatly in magnitude and which operate at wide range of speed. CAE tools development will lead to a significant reduction in the duration of the development period for engine as well as ensure a dramatic increase in product quality. This paper presents today's state-of-the-art CAE capabilities in the simulation of the dynamic and acoustic behaviour of engine and focuses on the relative merits of modification and full-scale structural/acoustic optimisation of engine, together with the creation of new low-noise designs. Modern CAE tools allow the analysis, assessment and acoustic optimisation of the engine.

The multi-body dynamics model of the X6170ZC diesel is established to analyze vibration and acoustic noise. The high quality finite element and simulation models are developed, and nonlin-ear springs are used to imitate the joints of engine components. The acoustic behavior of the struc-ture is evaluated by the velocity of surface vibration. The noise level is reduced by improving the structure of the engine. The result shows that the surface vibration velocity level is decreased about 3.7 dB (A) at-1 600 Hz after the optimization. Based on the contrast between the two structures, it is concluded that through structure design the combined noise can be reduced, and the virtual de-sign mode of diesel engines is feasible.

在分析一类高速气浮轴承工作原理的基础上，建立其轴径轴承的静态承载力模型，并据此分析出轴承司隙中气体流 量、压强与节流孔孔径司的相互关系，以及在低速运转下受离心力作用的轴径中心运动轨迹。最后，通过模拟仿真并考虑实际工况给出了轴承司隙和节流孔孔径两个关键尺寸。此举为高速气浮轴承的国产化奠定了一个良好的基础。

在分析一类高速永磁轴承工作原理的基础上，根据磁库仑定律建立其轴颈轴承承载力模型。并据此分析出轴承承载力与偏心距及剩磁强度司的关系，由此提出一种提高轴承承载能力的途径。同时考虑因转子质心与几何中心的偏移而造成转动时产生的离心力，分析了高速运转下转子的运动稳定性问题。此举为高速永磁转子一轴承系统的维修与制造奠定了一个良好的基础。

随着旋转机械在役运行时间的增加，转子部分多数会有质量偏心现象出现。这使得转子抽系的扭转振动与弯由振动的锅合作用明显增强。在已有辆合振动方程基础上，采用有限差分、Newmark 积分法求得动力响应，以300MW汽枪发电机组为研究对象，将其模化为多支承分布质量模型，采用FFT、STFT和wavelet 多种方法分析它在简谐衰减、非同期并列两种典型工况激励下以及不同偏心函数、弯扭下的弯振特性。分析结果为研究旋转机械复杂转子系统搞合振动中弯振特性的定量、定性分析提供了依据。因24参7

采用了振动实验数据的模态扩展技术研究油底南的辐射噪声。通过油底壳的少量振动没理数据和油底壳有限元模态分析相结合的方法计算了油底壳的振动响应，减小了单独采用有限元法计算结构振动响应时油激励和阴尼等参数引入的误差，提高了油底壳振动响应的计算精度；确认了油底壳振动响应计算的可靠性后，通过边界元方法计算得到了油底壳的辐射噪声。

以某直列6缸柴油机曲轴为研究对象，通过动力学非线性分析的方法对该轴进行了耐久性的研究。首先建立了曲轴等部件的三维有限元模型，采用子结构技术，对有限元模型进行模态压缩，然后运用AVL 的动力分析模块EXCITE 进行动力学非线性仿真，得到一个工作循环曲轴的瞬态应力分布状况，并进行疲劳强度安全系数计算。