CALCULATION OF SPLITTING VANES AND INNER FLOW ANALYSIS FOR CENTRIFUGAL PUMP IMPELLER

The calculation method for vane numbers is obtained on the intention that itshould have no back flow area in the flow passage of centrifugal passage. Then a criterion that thedesign of splitting vanes of centrifugal compound impeller should ensure that the back flow arearatio be the minimum is proposed. On the basis of the criterion, the slippery theory is used as oneof CFD methods to analyze the inner flow field of the impeller of various kinds of splitting vanesdesign, therefore, the optimized design of splitting vanes is obtained and which agrees with that ofsome testing results.

Transient simulation of a pump-turbine with misaligned guide vanes during turbine model start-up

Experimental studies of a model pump-turbine S-curve characteristics and its improvement by misaligned guide vanes （MGV） were extended to prototype pump turbine through 3-D transient flow simulations. The unsteady Reynolds-averaged Navier-Stokes equations with the SST turbulence model were used to model the transient flow within the entire flow passage of a reversible pump-turbine with and without misaligned guide vanes during turbine model start-up. The unstable S-curve and its improvement by using misaligned guide vane were verified by model test and simulation. The transient flow calculations were used to clarify the variations of pressure pulse and internal flow behavior in the entire flow passage. The use of misaligned guide vanes can eliminate the S-curve characteristics of a pump-turbine, and can significantly increase the pressure pulse amplitude in the entire flow passage and the runner radial forces during start-up. The MGV only decreased the pulse amplitude on the guide vane suction side when the rotating speed was less than 50% rated speed. The hydraulic reason is that the MGV dramatically changed the flow patterns inside the entire flow passage, and destroyed the symmetry of the flow distribution inside the guide vane and runner.

Analysis of the Impact of the Space Guide Vane Wrap Angle on the Performance of a Submersible Well Pump

In order to study the influence of the wrap angle relating to the space guide vane of a submersible well pump(250QJ125)on the flow field and pump performance,seven possible configurations have been considered(obtained by changing the blade wrap angle while keeping unchanged all the other parameters).Such configurations have been numerically simulated in the framework of a computational model based on the Reynolds time-averaged N-S equations,the RNG k-εturbulence approach and the SIMPLE algorithm.The impact exerted by different wrap angles of the guide vane on the performance of the pump,the internal losses of the guide vane and the flow field distribution in the bladeless area at the guide vane outlet has been assessed via cross-comparison of all these cases.The results show that the wrap angle has a significant influence:the wrap angle with the highest head is different from that with the highest efficiency,and changes in this angle have a more significant effect on the head than efficiency.A moderate raise of the wrap angle can improve the properties of the flow,reduce turbulence losses and enhance the energy conversion rate inside the guide vane.Different wrap angles can also lead to different fluid circulation modes in the bladeless area from guide vane outlet to impeller inlet,while they have a weak influence on the absolute value of the velocity of the fluid entering the impeller.

Influence of the Axial Position of the Guide Vane on the Fluctuations of Pressure in a Nuclear Pump

The influence of the axial mount position of the guide vane on the pressure fluctuation in a nuclear pump(AP1000)is investigated.The characteristics of the three-dimensional flow inside the nuclear pump are analyzed by means of numerical simulation.Results indicate that when the axial relative distance between the guide vane and the pumping chamber is reduced,in conditions of“small flow,”the efficiency of the pump increases,the pressure inside the pumping chamber decreases,while the losses related to the guide vane grow.Under large flow conditions,as the efficiency of the pump decreases,the losses for the guide vane and the pumping chamber increase.The pressure fluctuation in the annular pumping chamber is basically determined by the rotation frequency and the blade passing frequency.The magnitude of these fluctuations is affected by the guide vane axial position.In particular,the smallest possible amplitude is obtained when the outlet central plane of the guide vane coincides with the outlet axis of the pumping chamber.

Effect of guide vane outlet angle on pump performance and impeller radial force in an axial-flow heart pump

To study the effect of guide vane outlet angle on pump performance and impeller radial force in an axial-flow heart pump,guide vane outlet angle β4 is considered to be 20°,15°,10°,5° and 3°respectively. Based on ANSYS Fluent,numerical results of pump head and efficiency are validated by experiment results,in which Xanthan gum solutions are used with concentration of 0.06 wt. % as working fluid. Then,the effects of β4 on pump performance and impeller radial force are discussed,the errors of head and efficiency between test and simulation are within 5%. The results also indicate that the pump performance and efficiency are much better than those of other angles when guide vane outlet angle β4 is 10°,and the maximum variations in head and efficiency are 1. 9% and2. 2%,respectively. With β4 increasing,the pulsation of radial force decreases firstly and then increases,when β4 is 10°,the minimum pulsation is 0.0392 N,which is about 80% of the maximum pulsation amplitude.

Influence of long and short guide vanes on hydraulic performance of water-jet pump

Different guide vane structures will affect the flow inside the pump,and then affect the transformation of the pressure energy and kinetic energy,and change the velocity distribution of the pump outlet.In order to study the influence of long and short guide vanes on the water-jet pump,on the basis of conventional design,eight schemes of guide vane with different vertical heights were designed in the method of computational fluid dynamics for numerical calculation,the performance curve of water-jet pumps with different long and short guide vanes was obtained,and finally the influence of different guide vanes on hydraulic performance and internal flow was analyzed.The results show that all of schemes reducing the height of blade can improve the head and efficiency.In the schemes reducing the height on the shroud,the guide vanes that the height of the blade is equal to the height difference between hub and shroud in impeller have the highest head and efficiency.In all schemes decreasing the blade height,with the increase of the height difference,the velocity increases gradually and the distribution of turbulence kinetic energy becomes more reasonable in the guide vane outlet.The schemes reducing the height on the hub have more reasonable distribution of velocity and turbulence kinetic energy according to schemes reducing the height on the shroud.The guide vanes of long and short blades can be used to stagger the position of the diffusion flow generated by adjacent blades,which can reduce the effect of the velocity circulation and make the flow of the outlet position more stable.

Effect of Rotating Speed Fluctuation on External Hydraculic Performance of a Vane Pump

The rotating speed fluctuation for turbomachinery is a common problem, which will cause severe destruction for equipments and basis when the fluctuation is very strong. In this paper,in order to study the transient response characteristics of a radial vane pump subjected to slight( 5%) and strong( 20%)fluctuating rotational speeds, the variation characteristics of the external hydraulic performances are numerically predicted by means of computational fluid dynamics( CFD) technology. The results manifest that the responses of head and flow rate are different relative to the fluctuating characteristics of rotational speed. The response of the former is very satisfied in synchronism,while that of the latter is hysteretic. Meanwhile,it is found that the variation tendencies of the static pressures at the inlet and outlet of the pump are completely opposite, while the response characteristics of the dynamic pressures at the inlet and outlet are nearly identical.Subsequently,in order to further reveal the transient behavior during the instantaneous operating periods,two non-dimensional parameters are employed to deeply analyze it. The result shows that the variation tendencies of these two parameters are also approximately opposite.Moreover,the quasi-steady assumption is not able to be used to accurately assess the transient flow during transient operating periods. The comparison results show that the transient behavior does not show obvious distinctions between slight and strong fluctuating rotating speeds.

导叶安装角度对离心泵叶轮结构特性的影响

为提高带导叶蜗壳式离心泵的运行稳定性,研究了不同导叶安装角度对离心泵性能及叶轮结构力学响应的影响.以某带导叶蜗壳泵为研究对象,首先对其进行流场数值模拟,再通过静态和瞬态结构分析模块将水压力载荷导入叶轮结构,以实现单向流固耦合分析,研究不同导叶安装角度下叶轮变形与等效应力变化规律,最后通过模态分析研究叶轮结构的振动特性.结果表明:随着导叶安装角度减小,泵的高效区向小流量工况偏移,并且最高效率逐渐增大,最大提高2.1%;单向流固耦合分析得到的稳态结果与瞬态结果规律一致,其中叶轮最大变形量和最大等效应力值都随流量的增大而减小,在设计工况附近,都随导叶安装角度的减小而减小,最大差值为3.3%,且最大等效应力值变化的幅值较小;预应力对叶轮干模态固有频率的影响可忽略不计,与干模态对比,湿模态下的固有频率有较显著下降.

改变导叶翼型对水泵水轮机“S”特性的影响

针对水泵水轮机“S”特性区域的不稳定性问题,提出使用改型活动导叶翼型进行性能提升.以某水泵水轮机模型为研究对象,采用SST k-ω湍流模型对水泵水轮机全流道进行三维数值计算,通过对活动导叶翼型的改型设计,得出流量-转速模拟曲线,分析水泵水轮机组“S”特性改善情况.将计算与试验结果进行对比,并对改型活动导叶翼型前后机组的无叶区进行压力脉动分析.结果表明:在保证整体效率依然保持在92%附近的前提下,新的活动导叶翼型对机组的“S”特性依旧具有改善效果;无叶区压力脉动主要是受到活动导叶叶栅区域的分流在此重新聚集影响,并且与转轮叶片的动静相互扰动引起的;改型后的活动导叶降低了无叶区的压力脉动幅值,提升了水泵水轮机运行中的并网稳定性.

基于AMESim的新型变排量机油泵建模与仿真研究

以一种新型叶片柱塞复合形式的二级变量叶片泵为研究对象,其主要特点是将叶片顶端嵌入到定子中,转子、叶片、定子同时转动,减小了高速时的叶片冲击。推导叶片柱塞复合作用下泵的瞬时流量特性公式。基于AMESim仿真平台搭建比例电磁阀、瞬时流量、变量机构模型,并对二级变量叶片泵特性进行仿真,并通过台架试验进行相关验证。实验结果表明:该泵在中低速下压力-流量曲线吻合较好,说明流量和变排量建模准确;加减速曲线说明泵在比例阀不同占空比时,压力调节具有稳定性。

沙集泵站改造叶轮选型及流道改形研究

针对沙集泵站空化汽蚀较为严重,在工程加固改造时主体结构不变,无法通过降低站房底板增加叶轮淹没深度,从而提高空化性能的实际问题,采用计算流体动力学CFD方法,考虑泵站进口不同水位,对水泵装置全流道内部流动进行数值分析,研究水泵空化和能量特性。小幅降低叶轮中心高程,不仅未能减小空化范围,反而降低了泵装置效率,不宜采用。通过优选水泵水力模型、降速、增径并适当修整流道等方法,在保证泵装置能量性能的前提下,提高水泵空化性能。结果表明,采用方案一:叶轮直径增至1.68 m,转速降至250 r/min,基本消除了叶片进水边附近的附着空化,同时能够满足泵站特征水位组合下的流量和效率。成果也可用于类似泵站的设计和机组的选型。

抽水蓄能机组水轮机工况启动过程内部流场分析

本文采用CFD数值模拟的方法,模拟计算了抽水蓄能机组在水轮机工况启动过程内部流场特征。得到了在活动导叶开启过程中的速度、压力随时间的瞬态分布规律,讨论了蓄能机组开启过程中外特性的变化曲线。结果表明:活动导叶的开启规律可以大体分为五个阶段。活动导叶的开启规律是先缓慢开启,然后以较快的速度关闭,最后再保持到空载的开度,从第四阶段,导叶再逐渐打开直到额定开度。转轮扭矩和机组流量呈现出先增大后减小的趋势,当导叶逐渐打开时,转轮扭矩和机组流量再逐渐上升。本文为研究蓄能机组水轮机工况下启动过程的内部流动变化提供了参考依据,同时对提高水轮机工况的启动稳定性具有重要意义。

喷嘴导流片对喷水推进泵性能的影响

本文提出减少径向高度和导流片环绕导流锥分布这2种喷嘴导流片结构,通过DES-FEM耦合的方法研究了喷嘴导流片对喷水推进泵推力及噪声性能的影响。结果表明,随着喷嘴导流片径向高度减少,喷水推进泵推力增大0.61%,流量略微增大而扭矩略微降低,内流噪声主频仍为导叶叶频但幅值降低2.43%,总声压级略微升高;导流片环绕导流锥分布时,喷水推进泵推力提高1.03%,流量增大0.76%,扭矩提高,声压级主频处幅值降低2.05%,总声压级降低,内流噪声主频由导叶偏移至叶轮处,但两者声压级幅值差异较小;各方案频谱中均存在叶轮叶频谐频;内流噪声能量主要集中在中低频段。

导叶叶片数对LNG四级潜液泵轴向力及首级叶轮流场的影响研究

应用CFD技术研究了导叶叶片数对LNG潜液泵首级叶轮压力和轴向力分布的影响,对一、三级导叶同时设计7、8、9三种叶片数,采用K-epsilon湍流模型进行了多工况数值模拟,并采用液氮工质进行了相关外特性试验验证,得到LNG泵内部首级叶轮压力分布以及轴向力特性。结果表明:潜液泵所受总轴向力在导叶数为8时最小,泵的整体效率最优。作用在首级叶轮上后盖板的轴向力大于前盖板。其中,导叶数为8时首级叶轮前后盖板轴向力最小,压力分布最均匀;而导叶数为9时,与叶轮叶片数9相同,运转时会有共同的倍频出现,在相同的倍频上振动累加,并诱发共振,导致前后盖板的轴向受力最大,叶轮前盖板所受轴向力相对于其他方案平均增加了3.45%;后盖板轴向受力绝对值平均增加1.88%。综上,导叶数为8时潜液泵的水力效率最优。

超大扬程变幅大型导叶式混流泵选型研究

浙江省杭州市九溪排涝泵站,装设有6台大型导叶式混流泵,单机流量50 m^(3)/s,单台电动机功率10000 kW,为国内目前在建单机流量最大的导叶式混流泵。水泵受上游来水和下游钱塘江潮位的影响,扬程变化幅度很大,最低扬程1.71 m,设计扬程14.0 m,最高扬程15.4 m。为保证泵组在超大扬程变化范围内保持安全稳定运行,结合九溪泵站建筑物布置和运行情况,充分利用下游挡潮闸提高最低扬程,详细分析比较全调节和变频调节对优化低扬程运行工况的作用,并采取综合措施提高泵组结构设计刚强度,从多角度对泵组运行工况和选型方案进行优化分析,并提出泵组变频调节和运行优化建议,为类似泵站提供参考。

用于催化裂化装置强制循环泵的三元导叶设计方法及性能分析研究

强制循环泵是催化裂化装置烟气热量回收系统中重要的水循环动力设备,蜗壳为半球形结构带导叶的LUV型泵是一种广泛应用的强制循环泵,其导叶结构对泵的性能有着至关重要的影响。本文针对强制循环泵二元导叶在不同叶高处的进口叶片安装角与水流角不匹配的问题,发展了采用后盖板和前盖板的叶片中弧线角度分布和叶片厚度分布来构建叶型的三元导叶叶片结构设计方法,并数值研究了导叶后盖板和前盖板处进出口叶片安装角对泵额定工况效率和内部流动特性的影响。结果表明:随着前后盖板叶片进出口安装角中一个变量的增大,额定流量点效率均先增大后减小;设计的三元导叶方案比二元导叶方案在额定工况下的效率提高了0.9%;后盖板附近的叶片安装角与水流角的匹配性对泵的效率起到了更加重要的作用;三元导叶方案在后盖板附近0.1叶高截面上进口水流角与叶片安装角的匹配关系得到改善,此截面上的旋涡区减少,导叶内的能量耗散减小。

基于数据驱动的离心泵轴承特征分析及寿命预测

离心泵是工业中能量转换和流体输送的核心设备,其部件滚动轴承的可靠性对整个机组的安全运行尤为关键。为了解决目前滚动轴承寿命预测问题,对滚动轴承剩余寿命的最佳预测方案进行了研究。首先,从数据驱动和试验出发,利用试验台采集所得的离心泵轴承正常及故障状态下的数据,分析了时域、频域、时频域各特征在不同工况中的表现差异,发现了时域特征、频域特征、小波包分解能量特征、完全自适应噪声完备集合经验模态分解(CEEMDAN)能量特征可以捕捉到不同工况下的故障信息;然后,以单调性、趋势性指标加权分数为依据,结合特征的敏感性分析结果,优选出了轴承在全寿命周期中表现突出的12个特征,经核主成分分析(KPCA)-长短期记忆网络(LSTM)降维处理后,构建出了能够表征离心泵轴承退化过程的一维特征量;最后,对比分析了LSTM网络、反向传播(BP)网络和卷积神经(CNN)网络的预测效果。研究结果表明:LSTM网络的均方根误差(RMSE)为0.402,平均绝对百分比误差(MAPE)为0.332,预测精度在三者中最好,模型平均训练时间为12.6 s,可见LSTM网络在预测精度及模型训练时间上更具优势。

滚柱式叶片泵凹槽腔内流场分析

通过使用流体仿真软件ANSYS/Fluent,采用动网格的方式,在滚柱自转速度为13589 r/min时,对滚柱式叶片泵凹槽腔内的流场特性进行仿真分析。滚柱在凹槽腔内缩回和伸出运动分别对应排油和吸油状态,主要阐明了滚柱在这两种运动状态下,凹槽腔内流场的压力与速度矢量的变化情况。

导叶安放位置对离心泵蜗壳水力损失影响的数值研究

针对导叶安放位置对蜗壳水力损失影响的问题,对不同导叶安放位置下离心泵水动力特性进行了数值分析,并加以试验验证。首先,选取了5组不同的导叶安放位置,并开展了外特性试验以验证数值模拟结果的准确性;其次,基于数值模拟结果,分析了导叶安放位置对过流部件总压降变化的影响规律;然后,采用回转面展开的方式,研究了不同导叶位置下蜗壳进口来流条件变化,分析了导叶位置对蜗壳来流的影响;最后,分析蜗壳流道由进口至出口的总压变化规律,结合流场分布分析了导叶位置对蜗壳水力损失影响规律。研究结果表明:不同导叶位置下离心泵扬程和效率最大差异分别约为4.8%和3.5%;受蜗壳出口段漩涡影响严重,蜗壳水力损失变化明显高于其他部件;在θd 4位置时,出口段漩涡影响最小,蜗壳水力损失显著下降;隔舌位于导叶流道中间位置时,蜗壳来流均匀,蜗壳水力损失显著下降,泵性能更优。

水泵水轮机非同步导叶启动工况三维模拟研究

水泵水轮机低水头启动时,空载工况附近S特性明显,工况点进入后,机组宏观参数易发生振荡。为研究低水头启动工况机组快速稳定的内流机理,设置非同步导叶,引入调速器参数,通过三维模拟分析启动全过程宏观参数、压力脉动与流态的演变规律。结果表明,启动过程初期导叶同步开启,转速较小,转轮叶道内产生大范围失速涡,压力呈低频高幅值波动;转速上升过程中,流态逐渐平顺,压力脉动逐渐降低;进入调速器调节阶段后,工况点进入S区,压力脉动呈高频高幅值,而非同步导叶破坏了无叶区产生的高速水环,促使机组快速稳定。