发动机局部振动和噪声控制

【作者】 白书战；

【导师】 李树生； 李国祥；

【作者基本信息】 山东大学 ， 动力机械及工程， 2005， 硕士

【摘要】 随着人们对工作和生活环境的要求日益提高,国家法规日益严格,控制发动机的振动和噪声具有重要意义。 针对某车用发动机出现的曲轴前端断裂的问题,对曲轴前端进行了强度和挠度计算以及振动测试,确定发生事故的原因是由于皮带对连接在曲轴前端的皮带轮传动的冲击过大,使曲轴前端振动剧烈,从而导致危险截面出现裂纹,直至疲劳断裂。本文将发动机的曲轴前端简化为梁模型来进行理论分析,确定了它的振动模型,计算出了曲轴前端的固有频率。对曲轴前端进行了振动试验分析,通过振幅确定皮带冲击系数的大小,并提出了减小冲击系数的改进措施。 针对某车用发动机出现的高压油管断裂的问题,对发动机高压油管处的局部振动进行试验测试,通过分析其振动特点,确定了事故原因,并提出了改进措施。 对某柴油机进行了声功率的测量,确定了其噪声的声功率噪声水平。应用声强法对该柴油机进行了表面辐射噪声源识别,确定了发动机的主要噪声源,针对这些主要噪声源,提出了一些降噪的具体措施。 对于发动机的曲轴前端振动问题,经过强度计算可知,加上冲击载荷后安全系数较低,提出了通过加粗曲轴的危险截面来提高强度;计算出了曲轴前端的固有频率,从理论上排除了共振发生的可能性;并用测试振幅来确定皮带的实际冲击系数;通过加粗曲轴危险截面和增加过渡轮作为缓冲,有效地解决了这一问题。经过试验分析得出高压油管的两端振动不协调是导致油管发生断裂事故的根本原因,通过改变支架刚度改变共振转速,来解决已出厂发动机油管的振动问题;并通过改变油泵和传动齿轮间的连接方式来彻底解决高压油管的振动问题。通过某发动机的表面辐射噪声源识别,找出了发动机的主要噪声源,并进行了排序,按照对整机噪声贡献的大小分别为缸盖、排气管、齿轮箱、喷油泵等。更多还原

【Abstract】 With the improvement of working and living conditions, and the implementation of stricter regulations, the reduction of engine vibration and noise has an important significance. In this thesis, the calculations of intensity and flexivity as well as tests are carried out on the crankshaft front-end of a certain engine. The cause of the crankshaft front-end abruption is as follows: The excessive impact of pulley drive causes too much vibration on the front-end, and thus cracks appear on dangerous cross section which finally result in abruption of the crankshaft front-end. To determine the free frequency of the crankshaft front-end, a beam model is used as the simplified model of front-end. The impact factor of pulley drive is acquired through vibration test and analysis on the crankshaft front-end, and measures to reduce the impact factor are introduced.This thesis also carries out vibration test and analysis on high-pressure fuel pipes of a certain engine to determine the causes of pipe abruption and put forward improvement approaches.The noise level of a diesel engine is determined through the measurement of its sound power. The main noise sources of the diesel engine are identified with the sound intensity method, and measures for noise reduction are suggested.As to the excessive vibration of crankshaft front-end, stress analysis shows that safety factor under impact load condition is too low, and as a result the dangerous cross section of the crankshaft should be thickened for reinforcement. The free frequency of crankshaft front-end is calculated, and theoretically resonance vibration is avoided. With the test amplitude of vibration, the actual impact factor of pulley drive is determined. Finally, thickening the dangerous cross section and adding a transition pulley as a buffer settle the problem of excessive impact of pulley drive on the crankshaft front-end. Since test and analysis results show that the root cause of high-pressure fuel pipes abruption lies in the inconsistent vibrations of both ends of fuel pipes, the problem can be solved by changing the resonance speed with the change of pipe bracket stiffness as well as changing the connecting mode between injection pump and transmission gear. The main noisesources of an engine are identified and sorted as cylinder head, exhaust manifold,gearbox and injection pump according to each part’s contribution to the overallnoise.更多还原