基于近场声压法的离心泵噪声特性试验研究

采用近场声压法在开式试验台上对IS65-50-160A型离心泵进行了噪声特性试验研究,在变流量和恒流量情形下得到了泵噪声随汽蚀余量的变化规律及频率特性,分析了流量、汽蚀余量及泵入口吸入空气对A声级噪声和不同频率下声压级的影响.结果表明:在变流量情形下,非汽蚀工况下泵的A声级随流量增加而增大,且在高效率区达到最大值;汽蚀初生时,A声级噪声出现显著下降现象;深度汽蚀工况下,A声级噪声显著增加;以1 000Hz和2 000Hz为代表的高频声压级对整体A声级噪声的形成贡献较大;绝大多数流量下的声压级分别在250Hz和1 000Hz时出现峰值,该噪声峰值频率均与叶片通过频率相关.在恒流量下的汽蚀过程中,调节泵入口阀门导致汽蚀发生后,受入口吸入空气影响,泵的A声级噪声显著下降;本研究用泵的汽蚀特征频率为250Hz,该频率汽蚀状态下的声压级峰值比汽蚀前升高了5.9～16.4dB.     

水泵水轮机导叶动态水力矩特性分析

采用SST k-ω湍流模型对某高水头水泵水轮机进行全流道三维非定常数值模拟,分别对在水轮机工况和水泵工况运行下的导叶动态力矩特性进行分析。结果表明:在水轮机工况下,随着流量的增大,不同位置处导叶的动态水力矩变化规律一致,力矩值由正值变为负值,力矩脉动频率与转轮叶片数相关,流量越大,叶频影响越显著;在水泵工况下,最高扬程工况时导叶水力矩脉动频率主频为转频且脉动幅值较大,而最低扬程工况下导叶水力矩脉动主频为叶频,力矩脉动幅值较小。     

轴流泵优化设计及压力脉动特性研究

为探究明渠流对轴流泵装置性能的影响及提升大型低扬程轴流泵装置的整体水力性能,基于泵装置悬空高度、明渠进水池宽度、明渠出水池宽度三个参数,对大型低扬程泵装置进行三维非定常数值模拟计算,通过优化分析选出最优轴流泵装置模型,优化后的模型水力效率由81.3%提升为84.5%,进一步分析了最优轴流泵装置模型在不同流量工况下的流场特性及压力脉动特性。结果表明,小流量工况下运行的泵装置压力脉动时域特性明显优于额定流量工况和大流量工况,转轮进口及导叶进出口处测点压力脉动系数值均不超过0.01;转轮进口处三种流量工况下最大脉动系数均低于0.015,小流量、大流量工况下导叶出口处的压力脉动系数接近0,额定流量工况下导叶出口处的压力脉动系数为0.122。     

混流泵内压力脉动测量与分析

以比转速为336的某导叶式混流泵为例,沿流体流动方向在泵进口、叶轮出口、导叶出口、泵出口4个位置设置监测点,对比了0.6Q_d、0.8Q_d、Q_d、1.2Q_d、1.4Q_d(Q_d为设计流量)5种工况下的压力脉动情况。结果表明,泵进口和泵出口压力脉动幅值较低,导叶进口处脉动幅值最高,且小流量工况较大流量工况脉动剧烈,小流量工况下,泵内运行不稳定,出现回流、漩涡等,引起复杂、无规律的压力脉动;各工况下,泵进口处在叶频到7倍轴频范围内均出现了较为紊乱的脉动;与设计工况相比,非设计工况的脉动情况更为复杂。     

低比转速混流式水轮机流动噪声数值模拟

为预测低比转速混流式水轮机的主要流动噪声,采用重整化群RNGκ-ε模型和FW-H模型,计算了不同导叶与转轮叶片径向间距时水轮机导叶与转轮壁面上压力脉动构成的偶极子声源产生的流动噪声,分析了导叶与转轮叶片径向间距对水轮机压力脉动及噪声特性的影响,以及压力脉动与流动噪声之间的关系。结果表明,导叶末端和转轮叶片进口背面压力脉动最剧烈,是主要的偶极子噪声源,压力脉动和流动噪声的离散噪声在叶频及其谐频处出现峰值;随导叶与转轮叶片径向间距增大,压力脉动幅值减小,流动噪声减小,因此适当增大水轮机导叶与转轮叶片径向间距是一种有效降低流动噪声的途径。     

1000MW级核主泵内部非定常流动特性

为了对1000 MW核主泵内部流场进行深入分析,应用商业计算软件CFD对核主泵进行了非定常数值模拟,得到主泵内部压力脉动特性。结果表明:核主泵内部压力脉动呈现周期性变化,叶轮叶片对流体的影响频率为转频f=24.2 Hz的整数倍及其谐波;在叶轮内脉动幅度从叶片前缘到后缘逐渐增加,而在导叶内从叶片前缘到后后缘逐渐减小,在泵壳内变化相对较小;不同工况下,脉动幅值在额定工况下最小,在小流量工况时最大,并且偏离额定流量越多,压力脉动越严重。     

颗粒直径及浓度对高速离心泵非定常特性的影响

为探究不同颗粒直径、颗粒浓度对高速离心泵非定常特性的影响,以一台比转速为67的高速离心泵作为研究对象,利用ANSYS CFX软件建立的Mixture混合多相流模型进行了数值模拟计算,分析了高速泵的外特性、内部流场以及压力脉动变化规律。计算结果表明:随着颗粒体积分数的增加,效率最优工况点在向小流量处偏移,并且叶轮进口越偏向大流量工况,效率下降得越快,适当增加颗粒直径,对固液两相流的输送有积极作用;在不同颗粒浓度下,叶轮流道内的压力脉动主频均出现在叶频及倍频处,在颗粒体积分数为0.65%、颗粒直径为D=0.15 mm时,随着进口流量的增加,固相体积在叶轮流道处占比逐渐减小,在叶轮进口处颗粒占比逐渐增大;随着颗粒浓度的增大,叶轮流道内及隔舌处的压力均减小,叶轮流道内、隔舌处的压力和叶轮的径向力增减速度快慢的分界点在颗粒直径D=0.1 mm附近。     

压气机近失速点的性能仿真及可转导叶的影响

压气机的不稳定边界包括失速边界和喘振边界,对压气机工作特性有着重大的影响,甚至会对其造成严重损害,所以研究清楚近失速点的流场有着重要的意义。本文以某2.5级跨音速轴流压气机为研究对象,运用CFX计算其在全工况七种转速下的特性线;重点研究近失速点的内部流场,对比近设计点与近堵塞点流场状态,探究多级轴流压气机的失速特性与失速机理。对可转导叶的角度进行调整,将叶片向着叶片前缘吸力面方向和相反方向旋转相同的角度,计算50%,80%,100%转速下的特性线,发现在中高转速下流量压比特性线向左下平移,效率压比特性线向左平移更为明显,说明将叶片向着叶片前缘吸力面方向旋转可以起到推迟失速发生的作用。     

压气机不同运行工况下湿压缩性能分析

湿压缩技术能够有效提高燃气轮机输出功,降低燃气轮机对大气环境的依赖程度.该技术对压气机的影响因素非常复杂,压气机的运行工况对湿压缩效果的影响甚大.本研究采用CFX软件对某型三级轴流压气机在不同工况下的干、湿压缩过程进行三雏数值模拟.结果表明:压比不变的情况下,高转速时压气机近失速边界处质量流量增加,低转速时质量流量下降...     

螺旋混流式喷水推进泵压力脉动的数值研究

为研究螺旋混流式喷水推进泵动静干涉的压力脉动特性,运用ANSYS Fluent软件基于RNGκ-ε湍流模型,采用SIMPLEC算法进行变流量工况下非定常数值模拟,分析变流量工况下泵内各监测点的时域和频域特性。结果表明,螺旋混流式喷水推进泵内压力脉动的振源主要位于叶轮与导叶交界处,压力系数的幅值最大,且压力脉动自交界面处分别向上、下游传播并逐渐减弱。在叶轮旋转区域,压力系数的幅值受径向位置的影响较强,在导叶静止区域,压力系数的幅值受径向位置的影响较弱。各监测点压力脉动的主频不受流量变化的影响,均为叶片通过频率。在叶轮进出口,压力系数受流量变化影响最为明显;叶轮出口处的压力脉动频谱较宽。在远离叶轮旋转区域,压力系数受流量变化的影响较小,监测点的主频集中在叶频处,压力脉动幅值较小,无高频脉动出现。研究成果可为喷水推进泵的噪声及振动控制提供参考。     

Correlation Research between Turbulent Pressure Pulsation and Internal Sound Field Characteristics of Centrifugal Pump

In order to study the correlation between the internal flow noise of the centrifugal pump and the turbulent pressure pulsation,a single-stage single-suction centrifugal pump was used as the research object by the combination of numerical calculation and experiment.Based on the RNG k-?model and the N-S equation,the model pump was simulated numerically by CFD.A dipole sound source was extracted by the turbulent pulse action of the volute wall surface according to the FW-H equation.The acoustic field of the model pump was solved on the basis of the boundary element method,and the sound pressure distribution of the internal flow field under the action of the dipole sound source of the volute wall and the frequency response of the inlet and outlet fields were obtained.The results show that the distribution of hydrodynamic noise inside the centrifugal pump is related to the pressure pulsation,presenting obvious dipole distribution and disturbance at the tongue.The sound pressure value of the field is mainly concentrated in the blade passing frequency and double frequency,in which the blade passing frequency is the strongest,and the sound pressure value decreases obviously under other double frequency.The main frequency of hydrodynamic noise is the blade passing frequency.     

颗粒浓度对高比转速离心泵非定常特性的影响

为了分析颗粒浓度对高比转速离心泵非定常特性的影响,采用Mixture混合多相流模型,利用CFX软件进行数值模拟,分析了不同颗粒浓度时的瞬时湍动能、压力脉动及径向力。研究表明:随着颗粒浓度的增加,效率有所下降,清水条件下的离心泵效率最优;随着颗粒浓度的增大,叶轮内的瞬时湍动能明显增强,叶轮流道内及隔舌处的压力值均减小,脉动幅值均增大,作用在叶轮上的径向力会增大,而作用在隔舌处的径向力会减小;在不同颗粒浓度下,叶轮流道内的压力脉动主频均出现在转频处;隔舌处的压力脉动主频出现在叶频处;叶轮流道内、隔舌处的压力值和压力脉动幅值增减速度快慢的分界点和叶轮上、隔舌处的径向力增减速度快慢的分界点均在颗粒浓度为1%附近。     

弧形锯齿尾缘对叶片气动噪声影响及机理的研究

以弧形锯齿尾缘叶片为研究对象,同时设置三角形锯齿尾缘和直尾缘叶片作为参照组,采用大涡模拟结合声类比方程的方法,对比分析不同攻角下3种叶片的声压级指向性、噪声频谱特性。通过分析3种叶片周围涡结构,进一步对弧形锯齿尾缘所特有的声学机理进行研究。结果表明：同三角形锯齿一样,弧形锯齿结构并未改变叶片声压级指向性呈偶极子分布的规律;弧形锯齿尾缘有效降低中高频段的噪声,低频段降噪效果不明显;锯齿结构影响尾缘处展向涡的发展,进而对叶片气动噪声产生影响,且弧形锯齿尾缘对尾部涡结构的影响程度大于三角形锯齿尾缘。     

Performance enhancement of a pump impeller using optimal design method

This paper presents the performance evaluation of a regenerative pump to increase its efficiency using optimal design method.Two design parameters which defme the shape of the pump impeller,are introduced and analyzed.Pump performance is evaluated by numerical simulation and design of experiments(DOE).To analyze three-dimensional flow field in the pump,general analysis code,CFX,is used in the present work.Shear stress turbulence model is employed to estimate the eddy viscosity.Experimental apparatus with an open-loop facility is set up for measuring the pump performance.Pump performance,efficiency and pressure,obtained from numerical simulation are validated by comparison with the results of experiments.Throughout the shape optimization of the pump impeller at the operating flow condition,the pump efficiency is successfully increased by 3 percent compared to the reference pump.It is noted that the pressure increase of the optimum pump is mainly caused by higher momentum force generated inside blade passage due to the optimal blade shape.Comparisons of pump internal flow on the reference and optimum pump are also investigated and discussed in detail.     

直喷式柴油机表面辐射噪声频谱分析研究

采用工程法和简易法,运用大气压模拟测试系统,以某四缸柴油机为研究对象,测试计算柴油机整机噪声在81,90,101 kPa海拔下随转速的变化,以及在标准工况下1/3倍频程声压级.分析测试结果表明:表面辐射噪声随转速增加而增大,且随海拔的不同也会增大,缸盖辐射噪声在1 200～1 500 Hz内较大,主要是燃烧噪声所致.     

带脊状结构风力机翼型的噪声特性研究

采用大涡模拟和声类比的方法,以NACA0018翼型为研究对象,研究脊状结构对翼型远场噪声的影响。分别模拟来流速度为12和24 m/s,在6°攻角下布置脊状结构的翼型流场,对应的基于弦长雷诺数约为8.0×10⁴和1.6×10⁵。通过FW-H方程计算大涡模拟提取的声源项,得到Riblet-Q和Riblet-H翼型的流场和声场。非定常流场计算结果表明:6°攻角下Riblet-H翼型能够改善翼型边界层分离情况,抑制涡结构脱落,从而减小翼型表面压力脉动和接收点处声压波动,同时能提高翼型的气动性能。逆压梯度段脊状结构可有效减小频率在0~3000 Hz内的噪声。进一步研究表明,该状态下的噪声主要由边界层引起的涡脱落噪声主导。     

Pump-induced fluctuating pressure in a reactor coolant pipe

An analytical model is proposed to describe the propagation of pressure pulsations originated at the pump outlet through the inlet pipe of a pressurised water reactor (PWR). Pressure pulsations data from a pre-critical vibration monitoring programme (PVMP) for a C-E reactor are presented and compared with those calculated by the analytical model. The propagation of pump-induced pressure pulsation is important because of the potential for vibration and resultant damage of reactor internals.

The theory of pump-induced pressure pulsation distributions in the coolant annulus in a PWR has been developed by Penzes¹ and by Bowers and Horvoy² on the assumption that the pressure pulsations are due to excitations at the inlet nozzles. The pressures in the annulus are calculated based on prescribing the pressure at the inlet nozzles and on the concept of time dependent body force in the governing differential equations. The analytical model presented in the present paper and the theory given by Penzes¹ and Bowers and Horvoy² describe the propagation of pump-induced pressure pulsations in the critical regions (from the pump outlet through the inlet pipe and the coolant annulus in a PWR) for deterministic loads on PWR internals.

In the present analytical model the pressure pulsations are assumed to travel in plane waves so that the governing equation is one-dimensional in nature. The boundary condition at the pump outlet end of the inlet pipe is a time-dependent harmonic function; amplitudes for pump related frequencies are established based on an existing theory for hydraulic noise in centrifugal pumps.³ At the inlet nozzle end of the inlet pipe, due to the complexity of its acoustic characteristic, three types of boundary condition are considered—open, closed and piston-spring supported. Therefore, the analytical model essentially consists of a one-dimensional wave equation with time-dependent non-homogeneous boundary conditions. Closed-form solutions for the problem are derived using a linear transformation technique which reduces the problem to one involving a non-homogeneous differential equation with homogeneous boundary conditions.

Numerical examples are given for a typical reactor. Pressure power spectral density data are presented for data taken at inlet nozzles during a C-E PVMP. Distinct peaks at various pump related frequencies such as rotor speed, twice rotor speed, blade passing frequency and twice blade passing frequency, are observed. RMS pressures predicted by the analytical model at pump related frequencies are compared with those from PVMPs. The spatial distributions of the pressure field along the length of the inlet pipe for the three typical boundary conditions are given. Finally, the effect of the pipe geometry on the pressure field and the acoustic frequencies is analysed.     

基于塔筒添加螺旋线的风力机降噪性能优化研究

为降低风力机对周围居民的噪声污染,提出一种用于分布式风力机的塔架表面缠绕螺旋线的降噪方案。以S2030翼型风力机为计算模型,以螺旋线高度、螺距、螺头数、覆盖范围及旋向为因素,近尾迹辐射噪声总声压级为评价指标进行正交试验,在额定工况下利用ANSYS Fluent数值模拟平台LES/FWH方法进行数值计算。结果表明：螺旋线高度h为5.5 mm、螺距P/d为0.5、螺头数N为4、覆盖面积为全部、旋向为逆时针时为最优组合。各因素对总声压级影响的程度由大到小为螺距>高度>覆盖范围>螺头数>旋向。塔架缠绕螺旋线能有效降低200~2000 Hz中高频噪声声压级。降噪效果随轴向距离的增大而增大,最高可降低总声压级13.19 dB（A）。     

齿形襟翼对风力机翼型气动噪声影响的数值研究

为分析齿形襟翼（SGF）尾缘对风力机翼型气动性能及噪声特性的影响,利用SST k-ω湍流模型对装设Gurney襟翼（GF）和SGF的NACA0018翼型进行数值模拟,研究齿高和齿宽对气动性能和静压分布的影响,并采用大涡模拟（LES）对气动性能最优的SGF进行噪声预估和涡结构分析。结果表明：SGF可有效提高翼型升力系数并延迟失速;SGF-0.8-6.7模型可使最大升阻比提高8.61%,失速攻角延迟3°,其在拓宽高升力区间、延迟失速等方面具有最优性能;SGF翼型上下翼面噪声无明显差异,平均声压级随攻角增大而提高;SGF-0.8-6.7模型的尾迹噪声随攻角增大呈现先增后减的变化趋势,随距离增加而降低;翼型辐射噪声呈典型偶极子状,GF噪声小攻角下降低,而大攻角下则增大,SGF在不同攻角下均降噪显著,最大降噪量达10.2 dB;SGF尾涡稳定有序,能耗及损失降低,由此使气动性能和噪声得以明显改善。