【作者】 廖力达；

【导师】 何清华；

【作者基本信息】 中南大学 ， 机械工程， 2012， 博士

【摘要】 随着工程机械行业的迅猛发展,人们对于工程机械的综合性能提出了更高的要求,对于工程机械的舒适性和噪声控制的要求也越来越严格,节能环保技术已成为今后国际上工程发展趋势的主流。随着国内工程机械产品对欧美地区出口量的逐年增长,减振降噪成为我们不得不面对的难题,要想冲破这个技术壁垒,就必须满足欧美特有的强制性噪音标准。因此,降低以挖掘机为代表的工程机械噪声的需求十分迫切。对于以柴油机为动力的液压履带式挖掘机而言,挖掘机的噪声大部分来自柴油机,而柴油机噪声声源识别是降低其噪声的首要工作。因此,开展对挖掘机用柴油机的噪声特性研究有着重要的理论意义和巨大的工程实用价值。本文是在国家“863计划”课题《小型挖掘机用柴油机关键技术与产品开发》(课题编号2009AA045103)基础上引申发展而来,针对课题为山河智能装备股份有限公司SWE50G3小型挖掘机开发的4B2-38M34柴油机进行了噪声声源识别和噪声特性研究。由于在带有消声器的柴油机中噪声的主要成分是表面辐射噪声,因此本文的噪声声源识别分析的是柴油机表面噪声源零部件。而因为挖掘机在作业过程中负载是瞬变的、转速是波动的,所以噪声特性分析的是挖掘阻力、转速与噪声之间的动态关系。本文通过如下方法来确定挖掘机用柴油机噪声源：首先,通过有限元振型模态分析,得到挖掘机用柴油机各主要零部件对应于噪声测试方向上的振型模态及此振型下的主频；其次,利用声成像识别技术,对声强和声阵列测试结果进行噪声成像分析找到最大噪声源所在区域,并记录噪声信号；然后,利用小波分析,对噪声信号进行处理,确定主要噪声所在的频段,减少信号处理的计算量；接着,利用独立分量分析方法,在主要噪声频段的信号进行分离,得到代表各噪声源信号的独立分量,并提取各独立分量的主频；最后,将噪声成像显示最大噪声区域内各零部件的振型模态分析与独立分量作对比,找到与某独立分量主频相一致的振型主频率,此振型对应的零部件即为主要噪声发声部件。经过噪声声源识别,最终确认了油底壳、气门室盖、机体、飞轮壳和缸盖等主要噪声源零部件。本文通过如下方法研究了挖掘机用柴油机噪声特性：首先以SWE50G3挖掘机为样机,在Inventor环境中建立了挖掘机工作装置三维模型,获得了工作装置的结构参数；其次对挖掘机工作装置进行了运动学和动力学分析,根据lagrange动力学方程,推导出了挖掘机挖掘阻力计算方程式；然后,采用铲斗拖动砝码的方式进行了试验测试,通过对比拉力传感器测量数据与计算挖掘阻力,验证了计算方程式的有效性；最后,利用测得的挖掘机实际工作时工作装置倾角信号和液压缸压力信号,代入挖掘阻力计算公式得到实际挖掘阻力,将挖掘阻力、柴油机转速与实测挖掘机机外辐射噪声进行相关性分析,得出了挖掘机工作时机外辐射噪声主要受柴油机油门位置影响,其瞬态工况噪声高于稳态工况的结论。根据噪声源分析的结果,提出了对挖掘机用柴油机的改进意见,采用增加加强筋的方式提高了油底壳、机体、飞轮壳和缸盖刚度,采用优化外形的方式提高了气门室盖刚度,采取在曲轴上加装扭矩减震器的方式减小激振力向柴油机表面的传播,使柴油机整体噪声降低了2dB。更多还原

【Abstract】 With the rapid development of construction machinery industry, requests for the construction machine which has a higher integrated character are raised by people. Energy-saving and environment friendly has already become a prevailing trend. As the volume of exports of domestic construction machinery to US and European countries becomes bigger, there is now a problem we have to face—vibration and noise, we have to enhance the quality of our products to meet the impulsive standard of US and European countries. Therefore, there is an urgent need to reduce noise of construction machinery like excavator. The premier task is to find noise sources. For a crawler-type hydraulic excavat or powered by diesel engine, the main noise source is diesel engine. So it is of importance theoretical meaning and huge practical value to do a research on noise characteristic of excavator diesel engine.This thesis was based on a Project(2009AA045103) supported by the National High Technology Research and Development Program of China. The identification of noise source of4B2-38M34diesel engine equipped in SWE50G3excavator was developed by Sunward Intelligent Equipment Co., Ltd, as well as noise characteristic research. Surface radiated noise is the dominating part if there equips a muffler, so the analysis of noise source in this paper was focused on surface part of diesel engine. Noise characteristic analysis presented a dynamic connection among digging resistance, speed and noise for the load was transient and speed was fluctuated.The noise source of diesel engine was identified through the following approach:first, vibration modals and corresponding natural frequencies of different parts of diesel engine were obtained by finite element modal analysis. Second, according to the results of acoustic intensity and acoustic array, the biggest noise source was found through acoustic image identification technology, and then recorded noise signals. Third, the frequency domain of dominating noise was confirmed by using wavelet analysis. Then, signals in frequency domain of dominating noise was separated to get independent signals which were given by different noise sources, and then extracted the domain frequency from relevant independent signal. At last, main noise parts could be found after comparing the domain frequencies of vibration modals with independent signals’. It was confirmed that oil pan, valve cap, body, flywheel casing and cylinder head were main noise parts.The noise characteristic of diesel engine was researched through the following way:first, a three dimensional model of SWE50G3was obtained under Inventor environment, and construction parameters of the equipment were got. Second, kinematics and dynamics were analyzed and digging resistance calculation equation was deducted. Third, a test that the bucket dragged weight was conducted, the validity of calculation equation was verified by comparing the result of pull sensor with calculation digging resistance. Finally, actual digging resistance was obtained using obliquity signal and cylinder pressure signal measured in working condition. According to the digging resistance, speed and actual external radiated noise, a conclusion that actual external radiated noise increased as the accelerator became larger was received.Some measures to make a progress to diesel engine were proposed: rigid of oil pan, body, flywheel casing and cylinder head were enhanced by adding reinforce rib; rigid of valve cap was enhanced by optimizing its shape; crank equipped with a torque damper was also adopted to reduce transmission of force from the internal to the surface of diesel engine, decreasing the whole noise by2dB(A).更多还原