内燃机噪声源识别与噪声控制技术研究

内燃机工作时产生强烈的噪声,无论其应用于何种场合,降噪都是一个很重要的问题.本文着重剖析了用于内燃机噪声源识别的各种方法,并分别从燃烧噪声、机械噪声、进排气噪声和风扇噪声等方面进行了分析并提出了具体的解决措施.     

汽油机燃烧压力与燃烧噪声分析

为了深入研究汽油机的燃烧噪声产生的机理,达到在发动机设计阶段实现对燃烧噪声预测目的,提出根据汽油机的气缸压力与压缩压力计算燃烧压力与燃烧噪声的方法。采用FFT方法对缸内压力、压缩压力、燃烧压力以及气体共振激励力进行了频谱特性分析,确定了各频带范围内燃烧噪声的贡献量。理论分析结果表明:在小于1 000 Hz的频率下,压缩压力引起的噪声占主要地位,在1 000~10 000 Hz的频率段,燃烧噪声占主导,而在大于15 000 Hz的频率范围内,气体共振激励力引起的噪声较大。在中频段汽油机的转速对燃烧噪声的影响较大。     

内燃机噪声的形成原因及减小措施

通过柴油机气流噪声、机械噪声和燃烧噪声的各自形成原因的研究，依据噪声产生的部位及其产生的机理，结合生产实践，利用频谱分析，指出减小柴油机3种噪声应分别采取的措施。     

内燃机机械噪声的声强测量和识别技术及其控制方法

阐述了声强测量和识别技术的基本原理和发展现状,并具体说明声强技术在噪声测量和识别中的应用.讨论了如何在识别噪声源之后对内燃机机械噪声进行控制.     

内燃机燃烧噪声与机械噪声的测试方法研究

由于内燃机目前在汽车、轮船等机械上使用的特别多,在运行的时候经常会出现燃烧噪声和机械噪声的情况。所以对这种噪声问题进行识别和测试,就变得非常必要。本文利用建模的方法,对内燃机运行噪声进行了测试。     

维纳滤波器在燃烧噪声分离中的应用

目前分离内燃机燃烧噪声常用的方法主要有传递函数法、多元线性回归法,这两种方法均将内燃机的总噪声分为燃烧噪声和机械噪声两部分,并且假设实验获得的倒拖噪声为机械噪声,以此达到分离燃烧噪声的目的。然而上述两种方法所得到的燃烧噪声中还包含活塞敲击所形成的间接燃烧噪声。本研究测取了某汽油机转速为4 500 r/min和2 000 r/min转速下多个负荷工况的总噪声、缸压和振动数据,并利用-15～85℃A ATDC的时间窗对测量信号进行了截取,基于倒拖法将机械噪声分离。利用缸压信号和燃烧噪声信号构建了维纳滤波器对燃烧噪声进行了滤波,实现了直接燃烧噪声和间接燃烧噪声的分离。计算结果表明该汽油机活塞敲击产生的间接燃烧噪声主要集中于500～8 000 Hz的频率段。     

降低某中吨位叉车机外辐射噪声试验研究

针对某款国产中吨位叉车机外辐射噪声严重超标的现状,应用试验方法进行噪声源识别,并计算各主要噪声源的声能占比。根据噪声源识别的基础,分别对发动机机体辐射噪声、排气噪声以及风扇散热系统噪声进行针对性的有效改进,最终的测试结果发现综合治理后的叉车达到了国标要求,司机舒适度有了显著提升。     

某发动机机械噪声分解

本文通过对某国六汽油机进行机械噪声分解试验,提出了较为通用的发动机机械噪声分解方法,得到了各运动件占整机噪声的占比和频谱,为发动机机械噪声研究积累了相应的经验以及发动机的机械噪声优化指明了方向.     

中、小型内燃机电站噪声频谱试验研究及降噪措施

通过试验研究确定内燃机电站噪声频谱,找出主要的噪声来源,采取相应降噪措施,有效的降低了内燃机电站的噪声。     

Separation of combustion noise and piston-slap in diesel engine—Part I: Separation of combustion noise and piston-slap in diesel engine by cyclic Wiener filtering

The main purpose of this study is to characterize the relative noise given out by a diesel engine, around the Top Dead Centre (TDC) by quantifying the proportions of “mechanical noise” originating mainly from piston-slap on the one hand and ‘thermal noise” originating from combustion on the other hand. Two different approaches are described here to solve this problem.In the first part of the paper, the cylinder pressure is measured and used as a reference in order to reconstruct the thermal noise. Next, we propose a method based on applying a cyclic Wiener filter to the measured cylinder pressure in order to separate the noises of mechanical and thermal origins. The final result is to reduce the engine resulting noise.The second part of the paper is devoted to blind source separation (BSS) methods applied on signals issued from accelerometers placed on one of the cylinders. It develops a BSS method based on a convolutive model of non-stationary mixtures and introduces a new method based on the joint diagonalization of time varying spectral matrices of the observations. Both methods are then applied to real data and the estimated sources are finally validated by several physical arguments.     

Blind source separation of internal combustion engine piston slap from other measured vibration signals

Internal combustion engines have several vibration sources, such as combustion, fuel injection, piston slap and valve operation. For machine condition monitoring or design improvement purposes, it is necessary to separate the vibration signals caused by different sources and then analyse each of them individually. However, traditional frequency analysis techniques are not very useful due to overlap of the different sources over a wide frequency range. This paper attempts to separate the vibration sources, especially piston slap, by using blind source separation techniques with the intention of revealing the potential of the new technique for solving mechanical vibration problems. The BSS method and the Blind least mean square algorithm using Gray's variable norm as a measure of non-Gaussianity of the sources is briefly described and separation results for both simulated and measured data are presented and discussed.     

波束形成噪声源识别性能的仿真分析及应用

波束形成声源识别技术因具有在中高频的分辨率高的特点而被广泛应用于工程实际中。基于平面波和球面波的假设,以扇形轮阵列为例,进行了延时求和算法的单声源、多声源的声源识别性能仿真,结果表明:自主开发的算法程序是正确的,能够准确地识别单个及多个声源。进行了互功率谱及除自谱的互功率谱算法的声源识别性能仿真对比,结果表明:两种算法均可以准确定位声源,且除自谱的互功率谱算法可以有效地抑制旁瓣,提高了声源识别性能。为进一步验证算法程序的准确性,进行了工程试验,得到单一频率的声源成像图,开发了便于查看任意频带下数据结果的用户界面,同时与基于PULSE获得的声源成像结果进行对比,验证了算法程序的准确性。     

机械噪声的产生及其控制方法

对设备产生机械噪声的原因以及噪声的传播与辐射形式作了简要的说明和分析。例举了机械设备中常见的几种噪声源,并对其传播形式作了扼要叙述,同时针对噪声源的控制原则与步骤进行了较详细的介绍。     

Condition monitoring techniques for an internal combustion engine

Various condition monitoring techniques were applied during a laboratory engine test in order to understand the wear processes occurring and to determine a suitable method which could be applicable to the detection and diagnosis of abnormal engine conditions in practice. Fuel consumption rates were measured in conjunction with chemical analysis of the used oil by Fourier Transform Infrared Spectroscopy, and the various contaminant inspection methods. For the contaminant inspection of the wear debris in the lubricating oil, the quantitative and qualitative techniques of the Rotary Particle Depositor (RPD), Particle Quantifier (PQ), Spectrometric Oil Analysis, and Image Analyser Systems were applied and the results compared. The effectiveness of each to be able to respond to wear failure was also compared. Evaluation showed that, of the methods examined, the combination of RPD and PQ was the most suitable technique for the detection of abnormal wear occurring in the engine combustion zone. It is, therefore, suggested that this combination can be directly applied to internal combustion engines as an effective condition monitoring method.     

内燃机配气机构噪声控制

为降低内燃机配气机构振动噪声,以某125型摩托车发动机配气机构为研究对象,利用高次多项式对凸轮型线进行优化设计.配气机构多体动力学仿真表明:优化后的配气机构没有出现飞脱和反跳现象,进、排气气门丰满程度有所增加,在各个转速下,气门的最大振动加速度降低了65%左右,气门与摇臂的撞击力有所降低,且气门与气门座间的撞击力明显下降.在此基础上,制作了凸轮样件并对优化前后配气机构进行声功率测试试验.结果表明:在测量转速范围内声功率级均降低1.5～2dB.     

基于SolidWorks的内燃机构造与运动仿真

基于对内燃机构造和工作原理的研究,通过SolidWorks软件,利用其提供的零件建模、实体装配、工程图及动画制作的功能,将内燃机结构如气缸体、曲柄连杆机构、配气机构等结构进行三维参数化设计,完成内燃机基本机构的建模、装配和零件图的出图以及利用COSMOSMotion进行内燃机运动仿真。     

内燃机活塞优化设计及分析

基于活塞的结构和工作原理,运用Pro Tools M-Powered软件建立了有限元模型。依托该模型,对活塞的负荷边界、应力和位移进行了分析,最终实现对活塞的优化设计。     

工程机械驾驶室内部噪声源识别的小波分析方法

为降低工程机械驾驶室内部噪声,达到CE（Europen Communities）认证规定限值,必须确定其噪声源.按照CE认证标准对某工程机械的驾驶室内部噪声进行了测试,运用传统傅立叶变换和小波分析对测试信号进行了分析,确定了驾驶室内部的主要噪声源,并且证明了小波分析在噪声信号分析中比传统傅立叶变换更加有效、准确.研究结果为驾驶室降噪提供了实际和理论指导.