小波分析在泵的汽蚀初生诊断中的应用

针对泵在汽蚀的初生阶段的声信号为非平稳信号．采用频谱分析不能有效地发现汽蚀初生的症结，本文探索采用小波分析方法，通过对声信号进行多尺度小波分解．从而很好地检测出泵汽蚀的初生。     

叶片泵初生气蚀的小波包识别方法

通过小波包分析方法,对叶片泵入口压力脉动信号进行了信号分析处理,获得了初生汽蚀信号的各尺度频谱和能量特征值。试验测试信号分析结果表明：汽蚀初生信号尺度能量特征值可作为初生汽蚀状态进行定量识别的判据。     

全空化模型预测离心泵汽蚀性能的准确度

文献[2]采用两相流全空化模型计算了离心油泵输送粘油的汽蚀性能,但因缺乏试验数据,故无从知道计算的必需汽蚀余量与其试验值的差别。另外,目前还没有关于利用空化模型预测泵初生空化方面的研究;同时,全空化模型预测离心泵汽蚀性能准确度的评估目前还不多见。因此,本文采用全空化模型预测文献[3,4]的试验离心泵输送水时的汽蚀性能,获得了初生空化系数-流量曲线和扬程-有效汽蚀余量曲线,探讨了泵扬程与叶轮内部汽液体积比的关系以及非凝结气体浓度、紊流模型对扬程-有效汽蚀余量关系曲线的影响。本文的计算方法、经验和结果对实际工程中的离心泵汽蚀性能的预测和流动模型的选择有借鉴作用。     

油田用离心泵汽蚀性能的数值分析与试验

为了准确预测油田用离心泵的汽蚀性能,本文使用计算流体力学软件Fluent中的Mixture多相流模型与汽蚀模型相结合对离心泵内的汽蚀现象进行数值模拟,并通过油田用离心泵汽蚀性能试验对数值计算结果进行验证。在验证模拟结果可行的基础上,对离心泵结构及工作参数对其汽蚀性能的影响进行了数值分析,结果表明:叶轮采用6叶片较4和8叶片汽蚀性能更优;叶轮转速越小,离心泵抗汽蚀性能越好;离心泵进口流量越大,抗汽蚀性能越差。     

用自相关分析检测离心泵汽蚀的试验研究

汽蚀发生时,离心泵进口原有压力脉动成分和强度会发生变化,本文对离心泵进口压力进行了测试并进行了自相关分析,分析认为,通过自相关运算,能够提取压力脉动信号中的两种汽蚀特征量,所得结论有助于离心泵汽蚀的检测。     

螺旋离心泵的汽蚀性能分析

以150×100LN-32型螺旋离心泵为研究对象,对其汽蚀过程和汽蚀条件进行了分析.使用经验计算公式对其汽蚀余量进行了计算,并通过试验验证了计算值.采用Fluent软件,选用标准k-ε模型和汽蚀模型,对螺旋离心泵的汽蚀过程进行了模拟,找出了其最容易发生汽蚀的部位.从泵汽蚀基本方程出发,通过对螺旋心泵的结构进行分析,指出其汽蚀部位最容易发生汽蚀的原因、具有多级加能的作用和其具有优良的抗蚀性能.     

航空燃油离心泵抗汽蚀优化设计及仿真

针对航空燃油离心泵工作时出现的汽蚀问题,采用正交试验法对离心泵叶轮进行优化设计.选取叶轮出口直径D2、叶轮出口宽度b2、叶片数Z、叶片厚度H为正交试验的4个因素,完成了正交试验并对试验结果进行极差分析,得到了以泵汽蚀余量为优化指标的影响排序,并最终获得最优参数组合.通过流场仿真对现用离心泵和优化后离心泵的泵汽蚀余量和蒸...     

基于空化模型的多级离心泵汽蚀性能分析

应用Rayle igh-P lesset气泡方程建立离心泵空化模型,并与气液两相湍流控制方程耦合求解,得到了多级离心泵内三维湍流场及气液相分布,捕捉到气泡的初生、发展及冷凝过程。计算了不同流量下的离心泵的必需汽蚀余量并与实测结果进行了对比分析。     

航空离心泵高效抗汽蚀优化方法

针对航空增压离心泵汽蚀问题,给出了一种效率与汽蚀双目标优化设计方法。该方法首先建立离心泵的能量损失和汽蚀余量分目标函数;其次使用遗传算法对速度系数法所设计的离心泵性能参数进行寻优;最后以CFD仿真软件为平台建立离心泵的流道模型,对优化前后离心泵的压力和速度流场进行了仿真分析,并对优化前后离心泵的流量-效率、流量-汽蚀特性进行了对比研究。仿真结果表明:设计点流量下,优化后泵的效率提高了1.2%,必须汽蚀余量降低了12.51%,其他工况均优于优化前,说明该优化设计方法是可行、有效的。     

空化诱发离心泵振动特性的试验研究

离心泵内出现空化(汽蚀)时将诱发强烈的振动,本文对离心泵空化诱导振动特性进行了详细试验测量,重点分析了空化在各频段内振动强度的变化规律。随有效空化余量的降低,空化程度加剧,泵体测点上全频段范围内的振动特性在各个方向表现出相似的规律。通过对4000~8000 Hz频段内所得振动加速度的均方根进行分析,可以更有效地判断泵内空化的初生及发展过程,并且定义该频段信号为空化敏感频段。在临界汽蚀点附近时,不同测点处全频段范围内振动强度会经历一个急剧增加的过程,并到达极大值。     

基于小波变换的隐Markov模型离心泵故障诊断方法研究

根据离心泵故障振动信号的特点,本文提出了一种结合小波变换与隐Markov模型(HMM)的离心泵故障诊断方法。小波变换具有多分辨率分析并且在时频两域都具有表征信号局部特征能力的特点,利用Daubechies小波对振动信号进行一维8尺度的小波分解,然后从中提取一维信号的低频系数作为特征向量,将其输入到各个状态HMM进行训练,其中输出概率最大的状态即是离心泵的运行状态,从而实现离心泵的故障诊断。最后通过2BA-6A离心泵试验系统验证了该方法的有效性。     

长短叶片离心泵汽蚀性能数值模拟分析及实验研究

为提高离心泵的汽蚀性能,利用CFD数值模拟分析与实验研究相结合的方法对长短叶片离心泵在不同汽蚀余量时叶轮内部气液两相的分布规律进行分析研究,分析了3种不同短叶片进口直径在不同汽蚀工况时气泡分布情况对叶轮内部流动和性能的影响。分析结果表明:选择合理短叶片的进口直径可以有效提高离心泵的抗汽蚀性能,避免叶轮进口堵塞和流道内发生漩涡汽蚀。当汽蚀余量减小到一定程度,离心泵短叶片进口直径为0.65D2(D2为叶轮外径)时,在长叶片和短叶片的背面都会出现漩涡汽蚀区;当离心泵短叶片进口直径为0.75D2时,在长叶片背面与短叶片工作面间的流道内会出现两个漩涡汽蚀区;当离心泵短叶片进口直径为0.85D2时,离心泵的抗汽蚀性能最佳。     

Surge detection methods using empirical mode decomposition and continuous wavelet transform for a centrifugal compressor

The occurrence of surge in a centrifugal compressor results in large oscillations in pressure and flow. To avoid damaging the compressor because of surge, we develop several surge detection methods in this study. Considering the incipient surge phenomenon, the Empirical mode decomposition (EMD) and the Morlet Continuous wavelet transform (CWT) methods are selected. Both methods are validated through experimental data collected from surge tests conducted on the three-stage Ingersoll-Rand Centac centrifugal compressor at Toyota Motor Manufacturing in Kentucky, USA. For incipient surge detection, the EMD-based method can determine the threshold 1 sec earlier than the Morlet CWT-based method. Therefore, the EMD method can be used to implement the incipient surge detection scheme on the tested centrifugal compressor for safety considerations.     

离心泵进口结构参数改进措施

在简要叙述离心泵的结构和工作原理之后,着重说明如何改进离心泵进口的结构参数,以提高离心泵的抗汽蚀能力,为减轻和预防离心泵汽蚀提供理论依据。     

Cavitation pulse extraction and centrifugal pump analysis

This study extracted cavitation pulses from hydrophone signals sampled in a centrifugal pump and analyzed their characteristics. The modified and simplified Empirical mode decomposition (EMD) algorithm was proposed for extracting cavitation pulses from strong background noise. Experimental results showed that EMD can effectively suppress noise and obtain clear cavitation pulses, facilitating the identification of the number of pulses associated with the degree of cavitation. The cavitation characteristics were modeled to predict the value of incipient cavitation. Then, we proposed a method for detecting the wear of the impeller surface. That is, the information on the impeller surface of the centrifugal pump, including the roughness of the impeller surface and its wear trends, were quantified based on the net positive suction head available of incipient cavitation. The findings indicate that the proposed technique is suitable for condition monitoring of the pump.     

Numerical investigation of suction vortices behavior in centrifugal pump

A numerical simulation on suction vortices behavior in a centrifugal pump was carried out to investigate their influence on the internal flow through impellers including formation and shedding of cavitation by using a finite-volume method and k-ω Shear Stress Transport turbulence model. For cavitating flow, a two phase homogeneous cavitation model was used. A full three-dimensional flow in a single-section centrifugal pump consisting of a six blade impeller and shroud ring was computed with structured mesh. A constant suction vortex is imposed as a boundary condition. Vortices behavior was investigated according to the variation of flow rates of two pump systems with and without suction vortices. From the results, suction vortices induced biased flow structure and more cavitations, especially at the low flow rate condition. Complicated internal flow phenomena through impellers such as formation of cavitations, growing and shedding of the vortex, flow separation and flow unsteadiness due to the suction vortices are investigated and discussed.     

基于小波分析的离心式注水泵机械振动实时监测方法

为保证注水泵机组安全稳定运行,减少管理人员工作量,提出基于小波分析的离心式注水泵机械振动实时监测方法。探究注水泵作业流程与结构特征,结合多种常见故障类型分析结果,构建水泵输入、输出功率与生产效率的动力学模型;考虑到注水泵特性,以压电加速度传感器作为主要监测设备,明确信号采样要求,通过量化处理将模拟信号变换为数字信号,便于信号分析;当监测信号内低频成分丰富时,确定母小波和变换系数,经伸缩与平移处理完成连续小波变换与反变换;当低频分量不足时,引入小波包理论,分割小波空间,合理分解不同频带的信号,保证监测信息不丢失,获取信号特征,实现机械振动实时监测。仿真实验证明,该方法具有较强的信号处理能力,可通过监测信息准确判断出设备故障类型。     

液压泵故障的小波变换诊断方法

分析了小波变换的时 -频局部化特性及基于多分辨分析的信号小波分解重构算法 ,研究了信号局部奇异性在小波变换下的特性。根据故障信号和噪声的局部奇异性在小波变换下的模极大值在不同尺度上的传播特性不同的特点 ,并利用小波分解重构算法 ,对泵壳振动加速度信号进行了分解、去噪和重构。大大改善了监测信号的信噪比 ,对故障特征信号进行了时域定位 ,提取了故障特征频率。     

Feature extraction using wavelets and classification through decision tree algorithm for fault diagnosis of mono-block centrifugal pump

Monoblock centrifugal pumps are employed in variety of critical engineering applications. Continuous monitoring of such machines becomes essential in order to reduce the unnecessary break downs. Vibration based approaches are widely used to carry out the condition monitoring tasks. Decision tree, fuzzy logic, support vector machine and artificial neural networks are some of the classification algorithms employed for condition monitoring and fault diagnosis. In the present study, fault discriminating capability of wavelets in its continuous form with the application of J48 algorithm is analyzed. Vibration signals are extracted from the experimental setup. The continuous wavelet transform (CWT) is calculated for different families and at different levels which form the feature set. The features are then fed as an input to the classifier (J48 algorithm, a WEKA implementation) and the classification accuracies are calculated. Then, the results are validated to find classification capability of CWT features for monoblock centrifugal pump. The different faults considered for this study are cavitation (CAV), impeller fault, bearing fault (FB) and both bearing and impeller fault.     

离心泵汽蚀与最大允许安装高度的确定

离心泵吸入高度过高是造成汽蚀的关键因素。文中简要叙述离心泵内产生汽蚀的原因,着重说明离心泵最大允许安装高度的计算方法,并指出了减轻和预防离心泵汽蚀的措施,可给工程技术人员提供一定帮助。