《论文（设计）基于相干分析的离心式压缩机噪声源识别[J].doc》由会员分享，可在线阅读，更多相关《论文（设计）基于相干分析的离心式压缩机噪声源识别[J].doc（8页珍藏版）》请在三一办公上搜索。
1、基于相干分析的离心式压缩机噪声源识别 王 睿 李宏坤/大连理工大学机械学院振动工程研究所 陈养毅/中国石化国际事业有限公司摘要：从离心式压缩机振动和噪声信号的功率谱出发，研究了其振动和噪声的相干性。对比振动和噪声的功率谱，找出二者的特性与联系。最后经过相干变换得到振动和噪声的相干关系，并结合工程实践，证明相干性分析在离心式压缩机噪声源识别领域的可行性。关键词：离心式压缩机；相干分析；噪声源 中图分类号：TH452 文献标识码：B文章编号：1006-8155（2008）01-0007-04Identification for Noise Source of Centrifugal Compres
2、sor Based on Coherent AnalysisAbstract: In this paper, the coherent of vibration and noise is investigated according to the power spectrum of vibration and noise signals of centrifugal compressor. By comparing the power spectrum of vibration and noise, the characteristics and relationship of them ar
3、e found out. Then coherent transform is applied to obtain the coherent relationship of vibration and noise. According to project practice, the feasibility of coherent analysis has been proved in the field of the noise source identification for centrifugal compressor. Key words: centrifugal compresso
4、r; coherent analysis; noise source0 引言如何有效准确地检测出压缩机的噪声源，是环境噪声治理与压缩机优化设计的关键。压缩机各部件的工作状态通过一定的传递路径反映于振动和噪声中，对振动和噪声信号进行分析可有效地了解压缩机内部各部件的工作状态，判定压缩机的工作特性。对压缩机的振动和噪声信号的相干分析，是为了进一步找出振动和噪声之间的联系，相干分析可以进行设备噪声源的识别，根据分析结果，设计人员可对引起振动和噪声较大的零部件进行二次设计，为压缩机性能的改进提供可靠的理论依据。笔者根据压缩机噪声源的特点，进行噪声和振动信号的测试，并采用相干分析对压缩机的主要噪声源分析
5、和识别。并以国产某离心式压缩机组噪声源识别的过程，说明此方法的有效性。1 压缩机噪声特性压缩机噪声源是一种综合性的噪声源，它包括机械噪声、空气动力噪声以及电气噪声等。机械噪声：是由不平衡、机械碰摩以及结构共振产生，并通过轴、轴承、壳体向空间传播；空气动力噪声：是由气流脉动噪声和涡流噪声组成，气流脉动噪声是由于旋转的叶片周期性打击空间某固定空气质点而引起空气的压力脉动分量，产生相应的压缩脉冲而形成的；涡流噪声，也称紊流噪声，是一个宽频带的连续谱。涡流噪声是风机叶片在转动时，使在叶片后面的周围气体产生涡流，使空气发生扰动，形成压缩与稀疏的变化过程，当湍动气流中的压强脉动含有可听声频率成分,且强度足
6、够大时,则辐射出噪声1,4-5。离心式压缩机空气动力性噪声是气流脉动噪声和涡流噪声共同作用、相互混杂的结果。其中以气流脉动噪声为主要噪声源，在宽频带上常常有一个或几个突出的峰值就是气流脉动噪声，一般超出连续部分515dB。目前，很多拥有离心式压缩机的企业的工作条件都不能满足上述要求，当前国内外生产的离心式压缩机噪声一般都在100dB以上，严重影响正常的工作。噪声源识别是有效降噪的前提和基础。笔者根据离心式压缩机噪声的特点，对其噪声源分析与准确定位，以便为压缩机优化设计提供理论依据。2 噪声相干性分析2.1 相干函数的基本概念相干函数2-3是在频域上描述系统输入或输出的两个信号的相关程度的实值函
7、数。系统的相干分析对应于频域中的相关分析。相干函数是度量任意两个信号的因果程度的实值函数，可用来检测频响函数计算的有效性。在实际工程中，实测的输入输出两者的相干函数通常都小于1，计算的有效性要求相应的相干函数值大于0.75。笔者是利用双通道同时检测的噪声和振动信号进行相干分析，计算两者的相干程度，从而确定噪声源的位置。2.2 常相干函数表达式常相干函数是相干函数的基础,表达式为 （1） 式中 为频率；为输入信号和的常相干函数；为输入信号到的频响函数；为输入信号的自谱；为输出信号的自谱；为与的互谱。3 离心式压缩机噪声和振动测试3.1 测点位置 采用双通道同时进行噪声和振动检测。以压缩机组中第二
8、段的测点布置举例，由于压缩机组各段结构相似，故其它段的测点位置依此类推。图1是压缩机组二段噪声测点的俯视图。图1 压缩机组二段测点布置俯视图3.2 等效连续A声级测试数据检测压缩机组周围的等效连续A声级（水平测点位置距离压缩机组1m6，单位：dB）。 表1 压缩机组周围1 m处等效连续A声级 dB测点1234567等效连续A声级101.4103.1103.4103.9103.8103.2103.2测点891011121314等效连续A声级103.2102.5101.9102.6102.2103.9103.8可见，生产现场的离心式压缩机组的噪声超过了100dB，找出其噪声源是噪声治理的当务之急。
9、4 噪声源分析4.1 离心式压缩机噪声源分析离心式压缩机内部噪声源可以通过测量得到的主要频率与轴频相除得到相关参数： （1） 这里得到的大小与压缩机某级叶轮的叶片数相吻合（数值误差5%）。这样就找出本段压缩机缸体内的主要噪声源。4.2 时、频域噪声源分析利用PDM2000测试数据采集仪，对正常工况下工作的压缩机组的振动和噪声信号进行双通道同时采样。振动测点在机壳上和进、出气口等位置；由于压缩机组外形尺寸大于1 m，故噪声测点距离机组1 m，并垂直于振动测点；采样频率为25.6kHz，分析频率为10 kHz。下面是一个测点的振动和噪声的时域与频域信号。 （a）振动时域信号 （b）噪声时域信号 图
10、2 振动、噪声时域信号（a）振动频域信号 （b）噪声频域信号图3 振动、噪声频域信号从图3a和图3b的频域信号对比看出，在噪声信号中，频率为，和的噪声是主要噪声源。频率为的振动是主要振动源，也是噪声信号中的主要成分之一。通过测量得到的轴频。由式（1）可知，和。通过对本段压缩机内部的结构分析，可以找到拥有叶片数量为21的叶轮。频率为和的噪声，显然不是来自此段压缩机缸体。而且通过对比所有的测量信号，发现噪声信号中都含有频率为的噪声信号。那么找到频率为的噪声源，就是必须解决的问题也是确定本压缩机组噪声源的关键。下面使用相干分析的办法，找到相关程度最高的信号，以确定频率为的噪声源位置。4.3 相干分析
11、一组信号的功率谱如图4所示。（a）振动信号功率谱 （b）噪声信号功率谱图4 振动、噪声信号功率谱图4a和图4b比较分析可知，压缩机的振动信号频率与噪声信号频率成分较为相似，频域分布具有很强的相关性，且造成振动和噪声最大的主要频率（）基本一致。对频域信号进行相干变换，得到图5。图5 振动和噪声的相干分析图5分析可知，造成振动和噪声最大的主要频率（）的相干性达到88%。依此可知，振动和噪声频率特性具有很强的相关性。找到相干性最好的点，结合压缩机的内部结构分析，就可找到压缩机组频率为的噪声源位置。4.4 倍频程分析对噪声信号带阻滤波，过滤掉主要频率周围的一段噪声频率，并通过倍频程分析，来对比去掉主要
12、频率前后，压缩机组噪声的声压级大小。使用汉宁窗对4.3中的噪声信号分别进行带阻滤波，上限截止频率为1850Hz，下限截止频率为1750Hz。并对得到的滤波信号分别进行1/3倍频程变换，考察频率为的噪声对声压级的影响程度。图6 未滤波倍频程图7 带阻滤波倍频程对比图6和图7看出，未滤波信号等效A声级是102.95dB，带阻滤波信号等效A声级是100.12dB。如果信号中没有频率为的噪声，那么等效A声级将降低2.83dB。5 结论 实践证明，通过在强噪声背景下离心式压缩机振动、噪声物理量的测量和对振动、噪声信号的常相干变换分析，可基本实现离心式压缩机噪声源的识别，此方法具有一定的理论意义和工程实用
13、价值。参 考 文 献1 王珍，赵之海，杨春立，等.蜗旋压缩机振动噪声特性的应用研究J. 压缩机技术，2005（5）：17-19.2 陈茉莉，李瞬酩.信号源识别的相干函数法J.中国机械工程，2007(1)：95-100.3 史习智,等.信号处理与软计算M.高等教育出版社，2003.4 潘仲麟，翟国庆.噪声控制技术M.化学工业出版社，2006.5 王珍，赵洪健，胡萍.基于神经网络的蜗旋压缩机噪声的振动测量方法研究J.振动与冲击，2006(25S)：1022-1024.6 洪宗辉，潘仲麟.环境噪声控制工程M.高等教育出版社，2002.本文其他作者：王宏/沈阳鼓风机(集团)有限公司收稿日期：2007-
14、07-26 大连市 116024Editors note: Judson Jones is a meteorologist, journalist and photographer. He has freelanced with CNN for four years, covering severe weather from tornadoes to typhoons. Follow him on Twitter: jnjonesjr (CNN) - I will always wonder what it was like to huddle around a shortwave radio
15、 and through the crackling static from space hear the faint beeps of the worlds first satellite - Sputnik. I also missed watching Neil Armstrong step foot on the moon and the first space shuttle take off for the stars. Those events were way before my time.As a kid, I was fascinated with what goes on
16、 in the sky, and when NASA pulled the plug on the shuttle program I was heartbroken. Yet the privatized space race has renewed my childhood dreams to reach for the stars.As a meteorologist, Ive still seen many important weather and space events, but right now, if you were sitting next to me, youd he
17、ar my foot tapping rapidly under my desk. Im anxious for the next one: a space capsule hanging from a crane in the New Mexico desert.Its like the set for a George Lucas movie floating to the edge of space.You and I will have the chance to watch a man take a leap into an unimaginable free fall from t
18、he edge of space - live.The (lack of) air up there Watch man jump from 96,000 feet Tuesday, I sat at work glued to the live stream of the Red Bull Stratos Mission. I watched the balloons positioned at different altitudes in the sky to test the winds, knowing that if they would just line up in a vert
19、ical straight line we would be go for launch.I feel this mission was created for me because I am also a journalist and a photographer, but above all I live for taking a leap of faith - the feeling of pushing the envelope into uncharted territory.The guy who is going to do this, Felix Baumgartner, mu
20、st have that same feeling, at a level I will never reach. However, it did not stop me from feeling his pain when a gust of swirling wind kicked up and twisted the partially filled balloon that would take him to the upper end of our atmosphere. As soon as the 40-acre balloon, with skin no thicker tha
21、n a dry cleaning bag, scraped the ground I knew it was over.How claustrophobia almost grounded supersonic skydiverWith each twist, you could see the wrinkles of disappointment on the face of the current record holder and capcom (capsule communications), Col. Joe Kittinger. He hung his head low in mi
22、ssion control as he told Baumgartner the disappointing news: Mission aborted.The supersonic descent could happen as early as Sunday.The weather plays an important role in this mission. Starting at the ground, conditions have to be very calm - winds less than 2 mph, with no precipitation or humidity
23、and limited cloud cover. The balloon, with capsule attached, will move through the lower level of the atmosphere (the troposphere) where our day-to-day weather lives. It will climb higher than the tip of Mount Everest (5.5 miles/8.85 kilometers), drifting even higher than the cruising altitude of co
24、mmercial airliners (5.6 miles/9.17 kilometers) and into the stratosphere. As he crosses the boundary layer (called the tropopause), he can expect a lot of turbulence.The balloon will slowly drift to the edge of space at 120,000 feet (22.7 miles/36.53 kilometers). Here, Fearless Felix will unclip. He
25、 will roll back the door.Then, I would assume, he will slowly step out onto something resembling an Olympic diving platform.Below, the Earth becomes the concrete bottom of a swimming pool that he wants to land on, but not too hard. Still, hell be traveling fast, so despite the distance, it will not
26、be like diving into the deep end of a pool. It will be like he is diving into the shallow end.Skydiver preps for the big jumpWhen he jumps, he is expected to reach the speed of sound - 690 mph (1,110 kph) - in less than 40 seconds. Like hitting the top of the water, he will begin to slow as he appro
27、aches the more dense air closer to Earth. But this will not be enough to stop him completely.If he goes too fast or spins out of control, he has a stabilization parachute that can be deployed to slow him down. His team hopes its not needed. Instead, he plans to deploy his 270-square-foot (25-square-
28、meter) main chute at an altitude of around 5,000 feet (1,524 meters).In order to deploy this chute successfully, he will have to slow to 172 mph (277 kph). He will have a reserve parachute that will open automatically if he loses consciousness at mach speeds.Even if everything goes as planned, it wo
29、nt. Baumgartner still will free fall at a speed that would cause you and me to pass out, and no parachute is guaranteed to work higher than 25,000 feet (7,620 meters).It might not be the moon, but Kittinger free fell from 102,800 feet in 1960 - at the dawn of an infamous space race that captured the hearts of many. Baumgartner will attempt to break that record, a feat that boggles the mind. This is one of those monumental moments I will always remember, because there is no way Id miss this.
