Influence of blade outlet angle on performance of low-specific-speed centrifugal pump

In order to analyze the influence of blade outlet angle on inner flow field and performance of low-specific-speed centrifugal pump, the flow field in the pump with different blade outlet angles 32.5° and 39° was numerically calculated. The external performance experiment was also carried out on the pump. Based on SIMPLEC algorithm, time-average N-S equation and the rectified k-? turbulent model were adopted during the process of computation. The distributions of velocity and pressure in pumps with different blade outlet angles were obtained by calculation. The numerical results show that backflow areas exist in the two impellers, while the inner flow has a little improvement in the impeller with larger blade outlet angle. Blade outlet angle has a certain influence on the static pressure near the long-blade leading edge and tongue, but it has little influence on the distribution of static pressure in the passages of impeller. The experiment results show that the low-specific-speed centrifugal pump with larger blade outlet angle has better hydraulic performance.     

Knowledge Mining of Low Specific Speed Centrifugal Pump Impeller Based on Proper Orthogonal Decomposition Method

To clarify the complex relation between the pump blade shape and its corresponding hydraulic performance, the knowledge mining method of centrifugal pump impeller based on proper orthogonal decomposition(POD) was proposed. The pump blade shape was parameterized by cubic Bezier curve. The Latin hypercube design method was employed to supply the necessary samples for producing the perturbations of blade wrap angle, and blade angle at inlet and outlet. The hydraulic efficiency and head were optimized by NSGA-II and RBF hybrid algorithm. The Pareto-optimal solutions were obtained. In order to further illustrate the relationship between the centrifugal pump blade shape and its hydraulic performance, the POD method was used to discover the effects of optimized blade shape to the flow solutions. For the optimization of centrifugal pump MH48-12.5, blade shape and relative velocity field in impeller from Pareto-optimal solutions were analyzed. The results demonstrate that larger blade angle and smaller wrap angle increase the average kinetic energy in impeller, resulting in higher pump head design. Smaller blade angle and larger wrap angle decrease the velocity gradient from the pressure side to suction side, resulting in smaller hydraulic loss and higher efficiency design.     

Investigation on inlet recirculation characteristics of double suction centrifugal compressor with unsymmetrical inlet

The inlet recirculation characteristics of double suction centrifugal compressor with unsymmetrical inlet structures were studied in numerical method, mainly focused on three issues including the amounts and differences of the inlet recirculation in different working conditions, the circumferential non-uniform distributions of the inlet recirculation, the recirculation velocity distributions of the upstream slot of the rear impeller. The results show that there are some differences between the recirculation of the front impeller and that of the rear impeller in whole working conditions. In design speed, the recirculation flow rate of the rear impeller is larger than that of the front impeller in the large flow range, but in the small flow range, the recirculation flow rate of the rear impeller is smaller than that of the front impeller. In different working conditions, the recirculation velocity distributions of the front and rear impeller are non-uniform along the circumferential direction and their non-uniform extents are quite different. The circumferential non-uniform extent of the recirculation velocity varies with the working conditions change. The circumferential non-uniform extent of the recirculation velocity of front impeller and its distribution are determined by the static pressure distribution of the front impeller, but that of the rear impeller is decided by the coupling effects of the inlet flow distortion of the rear impeller, the circumferential unsymmetrical distribution of the upstream slot and the asymmetric structure of the volute. In the design flow and small flow conditions, the recirculation velocities at different circumferential positions of the mean line of the upstream slot cross-section of the rear impeller are quite different, and the recirculation velocities distribution forms at both sides of the mean line are different. The recirculation velocity distributions in the cross-section of the upstream slot depend on the static pressure distributions in the intake duct.     

两级动叶可调轴流风机内流特征的数值模拟

采用Fluent软件对某600 MW机组配套的两级动叶可调轴流一次风机进行了全三维定常数值模拟,分析了风机第一、第二级叶轮内流特征和动叶安装角对风机性能的影响.结果表明：第二级叶轮出口总压整体呈现高压区和次高压区交替分布的特征,且比第一级叶轮的对称性差;第一、第二级叶轮叶片压力面、吸力面的总压和静压分布规律相似;第二级叶轮叶片压力面和吸力面相应位置上的静压值均大于第一级叶轮叶片;随着动叶安装角的增大,第一、第二级叶轮的总压升系数和静叶的扩压系数均增大,且第二级叶轮大于第一级叶轮,表明第二级叶轮的做功能力和静叶的扩压能力均比第一级叶轮的大.     

Numerical investigation of pressure distribution in a low specific speed centrifugal pump

To study the pressure distribution of the volute casing, front casing and back casing in a prototype centrifugal pump, the pressure experiments and numerical simulations are carried out at six working conditions in this paper. The experimental results shows that the asymmetry of static pressure distribution on volute casing and front cavity is caused by the tongue of the volute and it may result in high radial and axial resultant force which can cause vibration and noise in the centrifugal pump. With the increasing of flow rate, the asymmetry of static pressure distribution and the magnitude of static pressure values reduce. The numerical results indicate that the pressure fluctuation near the tongue is strongest and it becomes slighter at point away from the tongue. With the increasing of flow rate, the local high-pressure region in impeller passage reduces and the flow becomes smoother accordingly, whereas the fluid speed becomes much higher which may cause further flow losses. The results predicted by numerical simulation are in coincident with the experimental ones. It shows that the turbulence model for simulating the flow field in centrifugal pumps is feasible.     

Investigation of the flow in the impeller side clearances of a centrifugal pump with volute casing

The paper is concerned with the fluid flow in the impeller side clearances of a centrifugal pump with volute cas-ing.The flow conditions in these small axial gaps are of significant importance for a number of effects such as disk friction,leakage losses or hydraulic axial thrust to name but a few.In the investigated single stage pump,the flow pattern in the volute turns out to be asymmetric even at design flow rate.To gain a detailed insight into the flow structure,numerical simulations of the complete pump including the impeller side clearances are accom-plished.Additionally,the hydraulic head and the radial pressure distributions in the impeller side clearances are measured and compared with the numerical results.Two configurations of the impeller,either with or without balancing holes,are examined.Moreover,three different operating points,i.e.:design point,part load or overload conditions are considered.In addition,analytical calculations are accomplished to determine the pressure distri-butions in the impeller side clearances.If accurate boundary conditions are available,the 1D flow models used in this paper can provide reasonable results for the radial static pressure distribution in the impeller side clearances.Furthermore,a counter rotating wake region develops in the rear impeller side clearances in absence of balancing holes which severely affects the inflow and outflow conditions of the cavity in circumferential direction.     

三级轴流式油气混输泵内流场压力脉动特性

为研究轴流式油气混输泵含气工况级间相互影响以及流道内压力脉动特性,应用Fluent软件数值模拟了三级油气混输泵在设计流量下的全流场瞬态,获得了混输泵内两相运动特征和流动部件内压力脉动情况,并分析了压力脉动时域和频域。结果表明,动静干涉是产生静压波动的主要因素,静压波动均值从入口到出口逐渐增大,级内动静交界处耦合作用较小,级间动静交界处耦合作用则较为明显。各级压缩单元叶轮进口均为脉动最剧烈的地方,距离叶轮进口越远,压力脉动幅值越小,在叶轮出口达到最小。在压缩单元内,流动方向的压力脉动主频幅值逐渐降低。首级叶轮出口、二级叶轮中间和出口以及末级叶轮中间位置压力脉动频率主要为2倍叶频,其他监测点压力脉动频率均为1倍叶频。气相对压力脉动频率影响较小,仅影响幅值。研究结果可为混输泵的结构优化设计及流动诱导振动控制提供参考。     

固液两相流对离心泵压力脉动特性的影响

为了研究含沙水流下径向式导叶离心泵内的压力脉动变化规律,采用大涡模拟和Mixture多相流模型相结合的数值模拟方法,并结合SIMPLEC算法,对输送固液两相流介质的径向式导叶离心泵进行了全流道三维非定常数值计算,并在叶轮与导叶交接面及蜗壳出口段处,将固液两相介质与清水介质时的计算结果进行对比分析。数值计算结果表明,离旋转轴越远处压力脉动幅值越小;导叶与蜗壳内叶频是压力脉动主要频率,且在1倍叶频处最大;导叶内压力脉动幅值均大于蜗壳内,且随着颗粒粒径的增大,压力脉动幅值逐渐减小;蜗壳隔舌处的压力脉动幅值大于蜗壳其他部位;在叶轮与导叶交接面处,清水介质时压力脉动幅值大于固液两相介质时,固液两相介质时脉动波形滞后于清水介质时0.003 5 s;蜗壳出口段,固液两相时压力脉动幅值均大于清水时。     

叶轮材质对船用泵振动性能的影响

为研究叶轮材质对船用离心泵振动性能的影响,分别对一船用泵的金属叶轮和ABS叶轮进行同条件试验,对比分析其振动性能。结果表明,两种材质叶轮的振动水平在0.6Qd、0.8Qd、Qd、1.2Qd、1.4Qd五个工况下呈现出随流量先减小后增大的趋势;进口法兰振动水平最低,出口法兰振动随流量偏离设计点呈现增大趋势;两种材质叶轮在0.8Qd、Qd、1.2Qd三个工况下振动烈度排序为:底座泵体顶端托架出口法兰进口法兰连接板;B级钢叶轮和ABS塑料叶轮在振动性能上整体趋势保持一致。研究成果可为船用泵水力性能优化及新材料应用提供参考。     

跨音速离心压气机级间静压测量研究

为获得车用涡轮增压器离心压气机各元件进出口及周向静压分布,开展了跨音速离心压气机级间静压测试研究。研究结果表明:蜗舌结构未造成导风轮进口静压分布周向不均匀(导风轮进口周向压力波动在2.5 kPa之内);蜗舌结构导致短叶片轮缘静压分布的周向不均匀性;同一转速下,跨音速流动最高效率工况周向静压分布不均匀;叶轮跨音速时,蜗壳沿着流动方向进行减速扩压;同一转速下,扩压器静压提升变化很小(约在3 kPa之内),而叶轮静压提升变化很大(约13～50 kPa),叶轮静压提升的改变决定压比流量特性线的陡峭程度。     

The change of the inlet geometry of a centrifugal compressor stage and its influence on the compressor performance

The impact on the compressor performance is important for designing the inlet pipe of the centrifugal compressor of a vehicle turbocharger with different inlet pipes. First, an experiment was performed to determine the compressor performance from three cases: a straight inlet pipe, a long bent inlet pipe and a short bent inlet pipe. Next, dynamic sensors were installed in key positions to collect the sign of the unsteady pressure of the centrifugal compressor. Combined with the results of numerical simulations, the total pressure distortion in the pipes, the pressure distributions on the blades and the pressure variability in the diffuser are studied in detail. The results can be summarized as follows: a bent pipe results in an inlet distortion to the compressor, which leads to performance degradation, and the effect is more apparent as the mass flow rate increases. The distortion induced by the bent inlet is not only influenced by the distance between the outlet of the bent section and the leading edge of the impeller but also by the impeller rotation. The flow fields in the centrifugal impeller and the diffuser are influenced by a coupling effect produced by the upstream inlet distortion and the downstream blocking effect from the volute tongue. If the inlet geometry is changed, the distributions and the fluctuation intensities of the static pressure on the main blade surface of the centrifugal impeller and in the diffuser are changed accordingly.     

不同叶轮高速部分流泵非定常压力场数值分析

为研究高速部分流泵由于叶轮和蜗壳的动静干涉而产生压力脉动情况,采用Fluent 6.3软件中S-A湍流方程和滑移网格技术(SM),分别选取直叶轮和复合直叶轮,在设计工况点进行非定常的数值模拟,分析中间截面总压和静压分布云图,发现复合直叶轮的总压高于直叶轮,而静压相近;在出口和蜗壳内壁圆周的0°,90°,180°和270°处布置4个监测点,比较总压脉动情况看出,复合叶轮的峰值明显高于直叶轮,而峰值之间的波动幅度要比直叶轮的小.     

考虑进气预旋的离心压缩机流动的数值分析

对某单级离心压缩机内的流动进行了数值模拟.计算结果表明,扩压器内压力最大的位置出现在蜗舌附近;当进口无预旋或预旋不大时,叶轮内流动参数的周向分布和一周叶片的受力情况是不对称的;在进口大预旋条件下,除蜗舌附近的周向位置外,叶轮内流动参数和主叶片受力趋于周向对称分布.     

结构参数对混流式循环水泵性能影响的数值模拟

在混流泵的设计改造中,常用方法是改变叶片的进出口角、改变进口边以及叶轮外径的切削。这些结构参数的改变,也改变了泵的性能。保持泵蜗壳和叶轮外形尺寸不变,改变叶片进出口角的大小、调节进口边、适当切削叶轮外径,设计出一系列的泵,并借助于FLUENT软件模拟泵的内部流场,然后,改变工况求得对应流量的扬程,从而绘制出结构参数改变时对应的泵性能曲线,总结结构参数变化对性能曲线影响的规律。     

交错叶片式双吸泵流动特性分析

为探究交错叶片式双吸泵的内部流动特性,本文基于CFD性能预测方法,在0.19Q_0~1.54Q_0不同流量工况下对某型号交错叶片式双吸泵全流道进行了数值模拟,并研究了泵外特性变化规律,分析泵压力、流速、流线和湍动能分布情况。结果表明:交错叶片式双吸泵效率高,额定工况下效率达到86.2%,高效区范围广,在额定流量工况附近,效率保持在80%以上;泵内部流动稳定,无明显漩涡与回流;在小流量工况下,泵内部流动变得紊乱,在叶轮流道间、叶轮与压水室交界处和隔舌附近存在明显脱流与漩涡,湍动能耗散严重,导致泵效率急剧下降。通过本文研究能对这类双吸泵的高效使用提供一定指导,并为该泵的进一步优化提供一定的参考。     

射流泵内部流动的实验研究

实验研究射流泵内有限空间水射流与其周围低速水流间的紊动混合。在射流泵11个轴向位置上布置了测压点：1个在渐缩锥形喉管入口,6个在喉管,4个在扩散管。用U型管测量11个测压点的壁面压强。用粒子图像速度场仪(PIV)对射流泵喉管入口和喉管内有限空间水射流进行测量。获得了4种流量比情况下射流泵对称面流场的速度矢量和轴心速度分布。测量结果为射流泵内部流动分析提供了可靠依据。     

Numerical investigation of influence of the clocking effect on the unsteady pressure fluctuations and radial forces in the centrifugal pump with vaned diffuser

The relative position between the diffuser vane and the volute tongue (clocking effect) has a great effect on the performance of the single-stage centrifugal pump, which however, is often ignored by designers. In this paper, the influence of clocking effect on the unsteady pressure fluctuation in a centrifugal pump and on the radial force of impeller is investigated. The hydrodynamic performance of the centrifugal pump with vaned diffuser was experimentally measured. Numerical simulation based on the Reynolds-averaged Navier–Stokes (RANS) combined with the SST k-w turbulence model was used to obtain hydrodynamic performance of the centrifugal pump. The numerical results of the hydrodynamic performance were in agreement with the experimental data. The results show that the clocking effect has great influence on the pressure fluctuation and on the unsteady radial force imposed on the impeller. When the diffuser vane approaches the volute tongue, the pressure fluctuation intensity in volute is relatively lower. Meanwhile, relatively larger radial force on the impeller and the lower efficiency are obtained when the diffuser vane is near the volute tongue. Thus, it is suggested that the volute tongue should be located near the middle of two diffuser vanes to obtain better performance.     

吸入室对双吸中开泵汽蚀特性的影响

针对双吸中开泵吸入室结构的自由性和复杂性加大了设计难度、改变了叶轮的进口流动环量及均匀度并影响泵的汽蚀性能,采用理论方法研究了叶轮进口环量对汽蚀性能的影响,并对一单级双吸中开式离心泵的吸入室进行了优化改型,用数值模拟和试验方法验证了改进型半螺旋吸入室对叶轮汽蚀特性的改善效果。结果表明,进口稍微带正环量能改善叶轮的汽蚀性能,但正环量加大到一定程度后汽蚀又会逐渐恶化;吸入室对叶轮汽蚀的影响因素包括叶轮进口环量和进口流场的均匀度,改进型的半螺旋吸入室提供了叶轮进口的正环量,并提高了叶轮进口流场的均匀度、大幅降低了泵的必需汽蚀余量。     

基于正交试验方法的虹吸式水轮机进水口流态优化

为了研究进水口流态对虹吸式水轮机水力性能的影响,采用CFD研究手段对包括进水池在内的虹吸式水轮机进行了全流道三维流场数值模拟计算。通过正交试验法分析发现,虹吸式水轮机在进水池内的最优布置方案为水轮机的悬空距离为叶轮直径的1/2,后壁距为叶轮直径的1.8倍,侧壁距为叶轮直径的1.9倍。通过对虹吸式水轮机的输出功率、水力效率及叶轮进口断面轴向流速分布等参数的分析比较,最终确定出适应该模型的最优方案,将效率从74.8%提升至84.5%,水力性能得到有效改善。     

基于正交试验的光伏水泵性能优化

以光伏水泵为研究对象,基于试验测试和理论分析建立光伏水泵出水量计算预测方法。采用正交试验设计优化方案,选取泵叶轮结构参数为优化变量,通过数值模拟和试验研究的方法,对该光伏水泵的性能进行优化和试验验证。结果表明：经优化后,光伏水泵系统的最低出水值下降至330 W/m²,水泵每日工作时长提升;光照辐射强度稳态时的泵出口压力脉动相较优化前有小幅提升,光照辐射强度瞬态变化时泵出口压力脉动波动幅度更平稳;优化后的模型泵叶轮进口低压区面积明显减小,叶轮出口压力显著增加,同时叶轮流道内速度分布更为均匀。