离心泵低噪声水力设计及动静干涉机理研究

发布时间：2018-04-11 13:17

本文选题：离心泵 + 流动诱导噪声　；参考：《江苏大学》2014年博士论文

【摘要】：本文是在国家杰出青年科学基金“离心泵基础理论和节能关键技术研究”(50825902)、国家科技支撑计划项目“百万千瓦级核电离心泵关键技术研究”(2011BAF14B04)和江苏省研究生创新基金“离心泵低噪声水力设计方法及关键技术研究”(CXZZ12-0679)的资助下开展工作。随着环境法规的出台,用户对产品的振动噪声指标提出更高的要求,掌握离心泵噪声产生机理以及如何在传统离心泵设计方法的基础上,通过优化几何参数提高离心泵的水力效率和降低离心泵的噪声水平,成为一个重要的研究课题。本文采用机理分析、试验测试和数值模拟相结合的方法对离心泵流动噪声的特性进行研究,旨在建立若干高效率低噪声离心泵水力设计准则。本文的主要工作和创造性成果有： 1.系统总结分析了离心泵噪声的分类和产生原因,提出现有的离心泵噪声测量和评价标准已不能满足其噪声评估的需要,离心泵流动诱导噪声是离心泵机组噪声测量和评估的关键。研究表明离心泵流动诱导噪声产生的重要因素是其内部流场的不稳定流体力,来源主要包括：动静部件间的干涉作用,非设计工况下的叶轮径向力和不稳定流动现象等。 2.搭建了离心泵流动诱导噪声测试平台,建立了无源四端网络法声学测试模型,试验研究了离心泵流动噪声随运行工况(变流量和变转速)的变化规律,分析了回流和空化发生时的流动噪声特性。通过研究叶轮切割对模型泵流动噪声声压级和空化性能的影响,提出叶轮和隔舌之间的最佳间隙值。结果表明：模型泵在小流量时发生回流,噪声声压级保持较高的水平,0.6Qd以后,声压级随流量的增大先减小,并在最高效率点达到最小,然后迅速增加；随着转速的提高,离心泵进、出口流动诱导噪声声压级呈线性上升,离心泵出口的流动噪声变化要比进口大；随着空化系数的减小,流动噪声的总声压级逐渐升高,并在达到极值后降低；模型泵叶轮和隔舌之间的最优间隙值为15%,间隙值小于最优值时,叶轮切割能明显降低流动噪声声压级并提升模型泵空化性能；在高效区运行时,流动噪声的主频为叶频及其倍频,轴频及其倍频也存在极值,回流现象发生时由于进口预旋造成流道堵塞,流动噪声的能量往轴频及超低频集中,空化现象发生时,随着空化系数的降低,噪声谱的能量往高频集中,但低频区叶片通过频率及其倍频的峰值逐渐减小直至消失。 3.采用结合计算流体力学和计算声学(CFD/CA)的混合算法对IS65-50-165模型泵的流动诱导噪声进行求解,并分析了声振耦合作用对流动诱导噪声计算的影响。发现流场求解时,采用Scale Adaptive Simulation (SAS)湍流模拟既能避免对网格和计算资源的过高需求,又能满足计算声源信息的需要。研究结果表明：距离隔舌位置近的监测点脉动强度较大,表明叶轮和蜗壳隔舌的动静干涉作用是引起流场脉动的主要原因,隔舌部位是主要的噪声源；经过试验验证,在泵高效运行区间内基于CFD/CA的数值计算求解误差在3.1%以内,完全能满足工程优化的需要,其中声学边界元法在叶频及其倍频噪声声压级求解方面有优势,声学有限元法虽然建模较复杂,但能直接展现流场体声源分布并考虑宽频湍流噪声的求解,计算结果与实际更加吻合；泵在非高效区运行时,仅采用偶极子声源进行声场计算将不能准确反映模型泵的声场特性；声振耦合作用对叶片通过频率下声压级的求解影响很小。 4.以叶频噪声声压级、扬程、效率和轴功率这四个指标作为判断标准,首次采用权矩阵方法借助数值模拟技术对离心泵叶轮进行多目标优化设计,得到一组水力模型优化方案。通过优化叶轮与原型叶轮的试验对比,发现该优化模型全部达标,验证了数值优化方法的可行性。通过PIV内流场测试发现：隔舌对流场影响很大,受叶轮和隔舌动静干涉影响,流场内速度的大小、云图分布都呈现周期性变化,这种干涉作用不但直接作用在隔舌附近流体,还能沿上游传播影响叶轮进口的流动；高效率低噪声离心泵叶轮设计的关键是选择合理的叶轮和隔舌间隙,以及减弱叶轮出口的尾流脉动。 5.提出了能较大幅度降低电动离心泵机组辐射噪声的引射装置,试验比较了原型泵、添加正常引射管径(dy=6mm)和偏大引射管径(dy=12mm)三种模型泵的性能,并首次数值计算了包含引射流在内的离心泵内部流场。研究结果表明：风扇空气动力学噪声是离心泵机组运行时产生辐射噪声中重要的组成部分,采用引射装置后,辐射噪声降低约8.3dB; dy=6mm时,模型泵扬程、效率和轴功率的变化均不大,小流量下模型泵的临界空化余量变小,加设引射管能够有效减弱回流强度,并降低回流发生的关键流量点；dy=6mm时,由于引射管较大地增加了叶轮实际流量,模型泵的轴功率增幅明显,而扬程和效率下降很快,同时,由于垂直入射的引射管流太大,造成回流发生时进口流场的进一步紊乱,抵消了其进口增压作用,并引起空化性能的恶化。 6.基于法国国立高等工程技术学校的动静干涉实验台,在某导叶式离心泵模型上进行了三孔探针、PIV、导叶叶片静压和进口流动噪声的瞬态测量等试验,通过评估导叶压力恢复能力和分析叶轮上、下游流场的瞬态特性,对离心泵动静干涉作用引起的湍流脉动机理进行了研究。研究结果表明：导叶内脉动的速度场存在变化明显的径向分量,表明模型泵整体等同于声源向外辐射噪声,速度场的切向脉动更加强烈表明声源具有明显的偶极子特征；按压力损失情况可以将导叶划分为无叶片区域、导叶进口至喉部区域和喉部下游区域,导叶静压恢复系数随流量的减小而变大；导叶设计流量下叶轮出口至导叶喉部区域的压力损失最小；小于设计流量时,压力损失主要集中在导叶无叶片区域,较大的液流角引起导叶进口的回流,复杂的流动结构造成较大的能量损失,并且随着流量的逐步减小叶轮进口发生回流,回流可以延伸到进口管形成失速团,这是小流量情况下湍流噪声的主要来源；大流量下压力损失主要发生在导叶喉部以后区域,导叶压力面附近的流动分离是压力损失和流动噪声的主要原因,但由于叶轮的阻隔下游的宽频湍流噪声不易传播到上游进口管。
[Abstract]:This article is in the "National Outstanding Youth Science Foundation of basic theory of centrifugal pump and energy-saving key technology research" (50825902), key technology research project "million kilowatt class nuclear ionization heart pump National Science and technology support" (2011BAF14B04) and low noise centrifugal pump hydraulic design method and key technology research and innovation fund of Jiangsu province "graduate" (CXZZ12-0679) to carry out the work of funding. With the environmental regulations, users put forward higher requirements on the vibration and noise index of the product, the generation mechanism of centrifugal pump noise and how to set the basic master meter method in the traditional centrifugal pump, by optimizing the geometric parameters of centrifugal pump to improve the hydraulic efficiency and reduce the noise level of centrifugal pump that has become an important research topic. This paper uses the analysis of the mechanism, characteristics and test method of combining numerical simulation on flow noise of centrifugal pump. The aim of this paper is to establish several hydraulic design criteria for high efficiency and low noise centrifugal pumps. The main work and creative achievements of this paper are as follows:
1. summarizes and analyzes the classification system of centrifugal pump noise and cause, put forward centrifugal pump noise measurement and evaluation of the existing standards can not meet the needs of the noise assessment, the centrifugal pump flow induced noise is the key measurement and assessment of noise of centrifugal pump unit. The results show that the important factors of centrifugal pump flow induced noise is unstable fluid the internal flow field of the source mainly includes: the interaction between static and dynamic components, radial force in non design conditions and unstable flow phenomena.
2. to build a test platform for centrifugal pump flow induced noise, a passive four terminal network method of acoustic test model, experimental study on the flow noise of centrifugal pump with the operating conditions (variable flow and variable speed) changes in the law, analyses the flow noise characteristics of reflux and cavitation occurs. The cutting effect on the flow model of the pump noise level and through the study of the impeller cavitation performance, put forward the optimum gap between the impeller and the casing tongue value. The results show that: the model pump reflux occurs when the flow rate is small, the noise sound pressure level to maintain a high level, after 0.6Qd, the sound pressure level decreases with the increasing of flow rate decreases, and reaches the minimum at the highest efficiency, then increased rapidly with; the improvement of speed, centrifugal pump, outlet flow induced noise level increased linearly, the flow noise changes of centrifugal pump export than import; with the decrease of cavitation coefficient, flow noise The total sound pressure gradually increased, and decreased in the distribution; optimal model clearance between the pump impeller and the tongue of the value of 15%, the gap value is less than the optimal value, the impellers can significantly reduce the sound pressure level of flow noise and enhance the model of pump cavitation performance; in high efficiency operation, frequency of flow noise and frequency for the leaf double shaft frequency and frequency are extreme, reflux phenomenon occurs due to the import of pre swirl caused by clogging, the flow noise energy to shaft frequency and low frequency, cavitation phenomenon occurs, with decreasing cavitation coefficient, the noise spectrum can amount to high concentration, but the peak frequency of blade passing frequency and its harmonics gradually decreased until disappeared.
3. combined with the use of computational fluid dynamics and acoustics (CFD/CA) hybrid algorithm of IS65-50-165 flow model of pump induced noise is solved, and analyzed the influence of acoustic coupling effect on the flow induced noise calculation. It was found that the flow solver, using Scale Adaptive Simulation (SAS) turbulence simulation can avoid excessive demand on the grid and calculation resources, and can satisfy the need of calculating the sound source information. The results show that: the distance between tongue position close to the monitoring point fluctuating intensity, show that the impeller and volute tongue of rotor stator interaction is mainly caused by the flow pulsation, the tongue position is the main noise source; through experiment, in the efficient operation of the pump within the range of CFD/CA based on the numerical calculation error is less than 3.1%, can fully satisfy the needs of engineering optimization, the acoustic boundary element method in frequency and blade frequency noise sound level Has the advantage of solving the acoustic finite element method modeling, although more complex, but can directly show the volume source distribution of flow field and solving the broadband turbulence noise into account, the calculation results agree with the actual work; pump running non efficient area, calculate the sound field will not accurately reflect the characteristics of sound field model of the pump using only the dipole source; the acoustic vibration coupling on the blade by affecting the sound pressure frequency is very small.
With 4. blade frequency noise level, head, shaft power and efficiency of these four indicators as the judgment standard, use technology to perform the multi-objective optimization design of centrifugal pump impeller numerical simulation of weight matrix method is adopted for the first time, a group of hydraulic model optimization. By comparison with the prototype impeller impeller optimization, the optimization model of all the standard, to verify the feasibility of numerical optimization method. Through testing the flow field of PIV found in the tongue: on the flow field is greatly affected by the impeller and tongue movement interference, flow velocity, cloud distribution changes of this period, not only a direct role in the interaction of fluid near the tongue, but also along the upstream propagation effect of impeller inlet flow; high efficiency and low noise design of centrifugal pump impeller is the key to reasonable selection of the impeller and the separation tongue gap, and weaken the impeller wake flow pulsation.
5. proposed can greatly reduce the radiation noise of ejector electric centrifugal pump unit, comparing the prototype pump, add normal ejector diameter (dy=6mm) and large diameter ejector (dy=12mm) performance of the three model pump, and for the first time, numerical calculation of the internal flow field of centrifugal pump includes the entrained flow, research. The results show that the fan aerodynamic noise is generated when the operation of the centrifugal pump unit is an important part of radiated noise, using the jetting device, the noise reduction of about 8.3dB; dy=6mm, head model of pump efficiency and shaft power are not large, small flow pump model the critical cavitation number becomes smaller, add the ejector tube can effectively weaken the strength and reduce the return, the key point of the recirculation flow; dy=6mm, the ejector can greatly increase the actual flow of the impeller, the pump shaft power model increases significantly, while the head and the efficiency At the same time, due to the large flow of the vertical incidence of the ejector tube, the flow field of the inlet is further disturbed when the flow occurs, which counteracts the import boosting effect and causes the deterioration of cavitation performance.
6. French national higher engineering schools movement based on the interference experiment of three hole probe, a guide vane type centrifugal pump model PIV, transient measurement test by static pressure and flow noise import blade, through the pressure recovery and the ability of analysis and evaluation of the guide vanes on the impeller, the transient characteristics of the turbulent flow field downstream. The mechanism of centrifugal pump caused by static interference were studied. The results show that: the pulsation of the guide blades velocity change the radial component obviously, show that the model is equivalent to the whole pump source to radiate noise, the velocity field of the tangential fluctuation more strongly indicate that the dipole sound source has obvious characteristics; according to the pressure loss can be the guide blade divided into the leaf area, the guide vane inlet to the throat area and downstream of the throat area, the guide vane static pressure recovery coefficient with the flow rate decreased; the guide vane design flow Under the impeller outlet guide vane to the throat region of minimal pressure loss; less than the design flow, the pressure loss is mainly concentrated in the guide vane without leaf area, large flow angle caused by the reflux of diffuser inlet, the complex flow structure caused a great loss of energy, and gradually decreased as the flow inlet of the impeller can be reflow, reflux the inlet pipe extends to the formation of stall, this is the case of small flow main source of turbulent noise; high flow pressure loss mainly occurred in the region after the guide vane throat, flow separation near the blade pressure surface is the main cause of pressure loss and flow noise, but due to the wide turbulence noise barrier downstream of the impeller is not easy spread to the upstream of the inlet tube.

【学位授予单位】：江苏大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TH311

【参考文献】