离心泵输送粘油时叶轮内部流动测量

在最优和小流量工况下,利用二维激光多普勒测速计分别测量了大出口角离心泵叶轮输送粘油时的内部流动,分析了内部流动特征。试验表明,在叶片吸力面存在已经分离的尾流,压力面不存在射流,叶轮内部流动为分离流动,不符合射流/尾流模型;由最优变到小流量工况,尾流宽度增加。为了提高叶轮输送粘油时的水力性能,应该削弱或消除分离的尾流。     

叶片扩压器内部非定常流动的PIV测量

通过试验和对数据的进一步处理，获得了叶片扩压器内部非定常流场的分布情况。详细分析了叶片扩压器内部的非定常流动现象和流动规律。通过研究发现在叶片扩压器进口处，高速区位于扩压器流道的左下角，低速区位于扩压器流道的右上角。随着流动的发展，流道左上角逐渐演变为一个大范围的高速区。     

现代流动测试技术在流体机械流动分析中的应用

介绍现代流动测试技术的特点、发展趋势及其在流体动力设备研发方面的应用情况。主要工作有：热线风速仪技术(HWA)用于离心压缩机扩压器流场测试研究、用于湍流边界层的减阻控制研究；粒子图像速度场仪技术(PIV)用于叶轮机械动／静相干非定常流场的研究、用于管道内横向射流的研究；激光多普勒测速技术(LDV)用于风机叶轮流场的测试研究等。     

无叶扩压器内部非定常流动的PIV测量

利用激光粒子成像速度仪(PIV)测量了无叶扩压器内部的非定常流场.试验发现在无叶扩压器内,沿扩压器宽度方向,气流速度分布是不均匀的,在靠近叶轮叶片吸力面侧形成了一个低速区,这个低速区是由叶轮出口的尾迹流造成的.这个低速区的存在影响了无叶扩压器的扩压能力和效率.     

短叶片转角对开缝叶片离心鼓风机叶轮性能的影响

以数值模拟的方式,对某开缝叶片离心鼓风机叶轮内部流动进行了研究,探讨了短叶片转角对离心叶轮流场及性能的影响,比较了叶片表面极限流线图谱的差异,分析了边界层分离区、叶片尾迹区及夹缝射流区流场的相互影响。     

离心泵快速开阀过程瞬态特性分析

为探究离心泵快速开阀过程瞬态流动特性,进行了非定常流场仿真.分析了瞬态压力、叶轮内涡流以及叶片表面压力脉动等变化规律,对优化离心泵性能及进一步研究泵阀启动流动分析提供参考.结果表明开阀过程泵出口压力先下降后上升;相同流量下,瞬态过程叶轮内部静压值低于稳态值,叶轮流道内漩涡数量和面积大于稳态值;叶片表面各监测点压力脉动表...     

离心泵叶轮内部粘油流动激光测速计测量

利用二维激光测速计系统准确地测量了离心泵输送粘度为４８ｍｍ２／ｓ粘油时最优和小流量工况叶轮内部流动。试验表明,叶片吸力面有很宽的尾流,压力面不存在射流,叶轮内部流动属主流／尾流模型。尾流位于吸力面／前盖板、吸力面／后盖板拐角处,并覆盖整个吸力面。由最优工况变到小流量工况,尾流有扩大趋势。     

离心叶轮流场对背压脉动的响应特性研究

本文首先采用数值模拟方法开展高速离心压缩机叶轮出口下游背压脉动的流场响应特性研究，分析指出高转速离心叶轮的气动性能波动随着背压脉动频率的增加而增大，但不同背压脉动频率下各时刻的流场分布具有相似结构。然后采用动态模态分解（DMD）方法对背压脉动下非定常流动的模态场进行分析，不同脉动频率下的非定常流场均包含叶轮转频的各阶谐波模态，流场响应的零阶模态为反映平均流场的基本模态，各阶谐波模态均为极限环模态，其它均为近似极限环振荡或衰减模态，流场响应的非定常成分主要由一阶谐波模态贡献。DMD分析结果表明：DMD方法能够对叶轮非定常流场变化特性进行降阶解构及准确预测。     

低比转速离心泵叶轮的设计

通过对叶轮内液液流动分析，提出了减小叶轮出口射流－尾流结构的措施。为减小圆摩擦损失，对时轮结构采取了适量车削前后盖板，周向修圆叶片的方法。     

利用三维紊流数值模拟进行离心叶轮设计比较

通过设计工况和非设计工况下叶轮内三维紊流数值模拟,比较了两种离心叶轮中的内部流动,以时均的N－S方程和标准k-ε模型为基础,在贴体坐标系中运用SIMPLEC算法进行计算,计算得到了两种叶轮内的流速,压力场分布,预估了水力效率,并与效率试验值进行了比较。计算结果表明,三维扭曲叶片叶轮在流速场,压力场分布,能量性能等方面均优于圆柱叶片叶轮。     

低比转速离心泵叶轮的设计

通过对叶轮内液流流动分析 ,提出了减小叶轮出口射流——尾流结构的措施。为减小圆盘摩擦损失 ,对叶轮结构采取了适量车削前后盖板、周向修圆叶片的方法。     

极低比转速叶轮内流体的流动分析和叶轮的设计

通过分析得出影响低比转速离心泵效率的主要原因是在叶轮出口存在二次流、边界层的分离等而引起的射流一尾迹结构并提出了改进的方法。实例表明文中提出的加大叶轮出口宽度,采用较大的叶片出口安放角,较大的叶片包角和叶片的线型前部采用较小曲率半径,后部分采用较大的曲率半径等叶轮设计方法能够设计出具有较高效率和较好性能的低比转速离心泵。     

低比转数离心泵驼峰现象的CFD分析

为揭示低比转数离心泵性能曲线产生驼峰现象的内流机理,采用RANS方法算法对一低比转数离心泵2个方案(有驼峰和无驼峰)下的内部进行了全流场CFD计算,重点分析了驼峰现象产生时2个方案内部流动结构的差异。结果表明:性能曲线出现驼峰时,2个方案的靠近蜗壳隔舌的叶轮流道内的流动结构差异最为明显;该流道内叶片压力面的低速区会明显增大并伴有漩涡流动;该流道进口也会出现明显的漩涡流动引起进口冲击损失增加;同时该流道出口的"射流-尾迹"现象也会突变,引起出口(混合)水力损失增加。因此这些损失的增大是引起驼峰现象的重要原因。     

高速离心叶轮叶片开缝的数值研究

提出在离心叶轮吸力面尾部开缝抽吸的方法,在叶片吸力面尾部对低速流体区域进行抽吸,以减弱由叶轮内二次流所导致的射流—尾迹结构。以Krain高速离心叶轮为例,建立抽吸模型,并进行了数值计算。数值仿真结果表明,在压气机流量范围内,叶轮尾部开缝抽吸可以减少叶片表面的分离区域,改善叶轮内部流场的流动状况,有效地提高离心叶轮性能。     

EFFECTS OF SPLITTER BLADES ON THE LAW OF INNER FLOW WITHIN CENTRIFUGAL PUMP IMPELLER

Analysis on the inner flow field of a centrifugal pump impeller with splitter blades is carried out by numerical simulation. Based on this analysis, the principle of increasing pump head and efficiency are discussed. New results are obtained from the analysis of turbulence kinetic energy and relative velocity distribution: Firstly, unreasonable length or deviation design of the splitter blades may cause great turbulent fluctuation in impeller channel, which has a great effect on the stability of impeller outlet flow; Secondly, it is found that the occurrence of flow separation can be decreased or delayed with splitter blades from the analysis of blade loading; Thirdly, the effect of splitter blades on reforming the structure of "jet-wake" is explained from the relative velocity distribution at different flow cross-sections, which shows the flow process in the impeller. The inner flow analysis verifies the results of performance tests results and the PIV test.     

串列叶片对离心风机叶轮性能及内部流场的影响

对串列叶片式离心风机叶轮的内部流场采用NUMECA软件进行了数值模拟研究,分析了串列叶轮不同相对周向位置因子对离心叶轮性能的影响,并对串列叶轮与原始叶轮进行了详细的流场对比分析。结果表明:相对周向位置因子对离心叶轮性能影响较大,当相对周向位置因子取0.05⁰.20时串列叶轮在性能上均有所提高且取0.10时性能达到最好;串列叶片能有效地削弱叶轮出口射流-尾迹结构对流场的影响,改善叶轮出口的速度均匀性,对控制风机的气动噪声有十分有利的影响。     

非设计工况下斜流泵叶轮进出口环量变化分析

基于RNG k-ε湍流模型对斜流泵内部三维流场进行了数值计算,重点针对非设计工况下的斜流泵叶轮进出口环量分布特征进行了分析。研究结果显示,在设计点附近的叶轮进口环量受叶片进口边影响较大,不同采样线的环量分布具有一定差异,小流量工况下受到叶轮进口回流的影响,不同采样线的环量分布趋于一致。叶轮出口环量分布受采样线位置影响较小,在设计流量点时,叶轮出口呈等环量分布。在小流量工况点,受到叶轮出口回流的影响,叶轮出口外缘处的环量数值显著增大。通过研究还发现,从叶轮出口流道通过轮毂一侧回流进入叶轮的流体微团具有与叶轮旋转方向相反的圆周速度分量,其环量数值甚至低于同工况下的叶轮进口环量值。     

Exit flow measurements of a centrifugal pump impeller

Discharge flows from a centrifugal pump impeller with a specific speed of 150 [rpm, m³/min, m] were experimentally investigated. A large axisymmetric collector instead of a volute casing was installed to obtain circumferentially uniform flow, i.e. without interaction of the impeller and the volute. The unsteady flow was measured at the impeller exit and vaneless diffuser using a hot film probe and a pressure transducer. The flow at impeller exit showed pronounced jet-wake flow patterns. The wake, which was on the suction/hub side at high flow rate, became enlarged pitchwisely on both the hub and the shroud side as the flow rate decreases. The pitchwise non-uniformity of the flow rapidly decreased along the downstream and the nonuniformity almost disappeared at radius ratio of 1.18 for medium flow rate. The mean vaneless diffuser flow was reasonably predicted using a one dimensional analysis when an empirical constant was used to specify the skin friction coefficient. The data can be used for a centrifugal pump impeller design and validation of CFD codes and flow modeling.     

Discharge flow measurements of a centrifugal turbomachinery

The objective of this research is to obtain a better insight into the flowfield in a centrifugal turbomachinery. To investigate this turbomachinery flowfield, measurements have been made with hot-wire sensors at the exit of a centrifugal impeller. The measured data at the discharge show a jet-wake type of flow pattern which results in a strong vorticity field. The flow with high velocity found on the pressure side tends to move to the low pressure region present at the suction side of an impeller blade as a form of roll-up around the blade trailing edge. This flow motion is believed to cause an unsteady flow separation at the suction side of the blade and consequently to disturb the flow in the adjacent passage.     

Numerical simulation and analysis of flow characteristics in the front chamber of a centrifugal pump

We performed numerical simulations to study the flow characteristic in a centrifugal pump based on the RANS equations and the RNG k-ε turbulent model. The flow field, including the front and back pump chambers, the impeller wear-ring, the impeller passage, the volute casing, the inlet section and outlet section was calculated to obtain accurate numerical results of fluid flow in a centrifugal pump. The flow characteristic was studied from the internal flow structure in pump chambers, the radial velocity at impeller outlet as well as the pressure inside of the pump, the circumferential velocity and the radial velocity in front pump chamber. The variation of flow parameters in internal flow versus flow rate in the centrifugal pump was analyzed. The results show that the overall performance of the pump is in good agreement with the experimental data. The simulation results show that the distribution of flow field in the front pump chamber is axial asymmetry. The energy dissipation at the impeller outlet is larger than other areas. The distribution of the circumferential velocity and that of radial velocity are similar along the axial direction in the front pump chamber, but the distribution of flow is different along the circumferential and the radial directions. It was also found that the vorticity is large at the impeller inlet compared with other areas.