舰船用泵倾斜出口边叶轮的径向力研究

舰船用泵的振动噪声影响到舰船的隐蔽性,减振降噪是当下关注的重要议题。舰船用泵在小流量工况运行时,常因作用于叶轮上的径向力分布不均而引发机械振动,进而产生噪声。在水力设计方面,可以采用叶轮出口边倾斜设计的方法来改善船用泵在小流量工况下的径向力特性。运用数值模拟与试验相结合的方法来研究径向力脉动分布及其特性,模拟结果表明:出口边倾斜布置相较于传统的出口边垂直布置可以有效改善叶轮的径向力特性,而水力性能变化不大。因而,完全可以在不改变泵结构的前提下,将直叶片叶轮更换为斜叶片叶轮,进而取得良好的降噪效果。     

梯形断面蜗壳式离心泵作透平叶轮的设计与试验

为提高非圆形断面蜗壳式离心泵作透平的效率,以一比转速为193的梯形断面螺旋形蜗壳式离心泵为原型,设计了适应此类泵作透平运行的透平专用叶轮。根据原型泵梯形断面蜗壳几何参数,依据面积相等的原则,推导梯形断面几何参数与当量圆断面半径的换算关系式;依据等速度矩定律确定叶轮进口速度矩,推导出叶片进口安放角与设计流量的关系表达式;对于叶片进口较宽的情况,在轴面投影图中划分三条流线,分别计算三条流线与叶片出口边交点处的出口安放角;基于ANSYS BladeGen与NX软件建立新叶轮的三维模型,制作试验叶轮,开展外特性试验,并进行数值模拟分析。结果表明:新叶轮将透平最高效率由71.9%提高到了77.3%,较原型叶轮透平最高效率提高了7.5%,且新叶轮在75~130 m~3/h的流量区间均能高于72%的效率运行,效率曲线较平坦,高效区运行范围宽。数值计算结果分析表明新叶轮进口能较好地适应螺旋形蜗壳的出流;从叶片进口到叶片出口,液体压能得以较均匀地转换,叶轮内的水力损失较原型泵叶轮内部显著减小。透平试验高效点与给定的设计流量一致,验证了该文提出的透平叶轮设计理论和方法是合理可行的。     

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。     

叶片安放角对无轴泵喷推进器性能的影响

为揭示叶片安放角对无轴泵喷推进器运行特性的影响规律,采用计算流体动力学方法对无轴泵喷推进器在不同叶片安放角内部流动进行了数值模拟,分析了泵外特性、推力、内部流场分布以及压力脉动的变化规律。结果表明：设计工况下随着叶片安放角的增大,模型泵喷扬程和推力逐渐增大,效率逐渐降低,相较于叶片安放角0°,叶片安放角为+4°时扬程增大5.99%、推力增大2.08%、效率降低7.6%;叶片进口边压力明显下降,叶轮内流体流速逐渐减小,叶轮出口漩涡强度逐渐增强,漩涡面积减小;叶片安放角的变化对于泵喷内压力脉动的主频没有影响,但对主频处的幅值具有明显的影响,尤其是轮缘和流道中部压力脉动。研究结果对于低噪声无轴泵喷推进器的设计具有一定的参考价值。     

离心压缩机大流量三元流叶轮的试验研究

本文对多级离心压缩机用的大流量三元叶轮的轮毂比大,相对宽度大,进口马赫数高,又要求轴向尺寸小的气动特点。论述了给定载荷的叶片设计方法和最佳叶片载荷分布型状;在无粘准三元设计计算中如何采用熵梯度使叶轮进口和出口流场计算与实际粘性流动相符合等问题。     

两相流纸浆泵的使用

液相、气相和固相是物质存在的三种形态。其中任何两种形态的物质混合在一起形成流体,就叫做“两相流”。目前,国内现有的大多数纸浆泵,都是按清水（一相流）的理论设计而生产的,由于其设计和实际运行条件不一致,导致该类泵使用寿命短,效率低,腐蚀严重。而近几年问世的CLX型系列两相流纸浆泵,是根据具有世界先进水平的“蔡氏理论”设计生产的,它的叶轮、纸浆流道设计,摒弃了清水（一相流）的理论局限,使其能与抽吸流质的水和固体混合物（两相流）相适应,是我国造纸行业的一种换代新型高效节能产品。其特点是: 1.泵体、涡壳、流道进行了重大改进,便于高浓度两相流介质抽送,提高了效率; 2.叶轮叶片由三叶封闭式改为两叶敞开式,叶片形状及角度也进行了改进设计、适应6％以下浓度介质抽送需要; 3.该系列泵进口和出口部位均为减小介质抽送阻力而进行了改进; 4.采用的联轴节,使拆卸、维修方便,无须移动电     

小流量高扬程液氢泵水力优化和抗空化的结构设计

针对液氢在低温系统或低温储罐中输送的应用需求，依靠泵设计经验参数取值而设计的小流量高扬程液氢泵，相似定律转换为模型泵，试验测试其外特性得到：在额定工况下，与理论扬程相比，泵内存在6 m水力损失，同时，液氢总是处于近饱和状态，特别当泵前低温流体的进口压力降低或波动时，离心式液氢泵极易发生空化，造成扬程下降。以提高液氢泵的抗空化特性和提高泵水力效率为目标，建立小流量高扬程液氢泵的多目标优化设计方法，依据小流量高扬程液氢泵模型泵的外特性测试结果，对泵头的几何结构参数进行优化设计，结果表明：叶轮入口直径增大1.5 mm、直角的叶片进、出口安放角减小为60°、叶轮出口直径减小0.5 mm、叶片进口宽度减小0.1 mm,叶片出口宽度减小0.3 mm,减小流体出口间隙，有利于泵减小水力损失，提高泵效率，并改善泵的空化性能。本研究采用的计算方法为小流量高扬程液氢泵高效水力模型的优化设计提供参考，研究结果为小流量高扬程液氢泵的结构优化和获得工作特性的实验研究提供理论依据。     

降低离心式纸浆泵压力脉动的措施

分析了离心泵内压力脉动的产生机理,分别阐述了汽蚀、回流、涡流、离心泵叶轮形状及叶轮出口与隔舌相互干扰对纸浆泵压力脉动的影响。总结出了降低压力脉动的4条途径：提高泵的抗汽蚀性能;控制进口回流;减弱出口涡流;改变叶轮和隔舌的形状,完善叶轮与隔舌参数的匹配。分析得出：从泵的水利设计方面来优化叶轮和隔舌的参数,是降低纸浆泵压力脉动的最有效方法。     

消息报道

MC中浓浆泵通过鉴定山风广州水泵厂历经3年多研制成功的专利产品——MC型中浓浆泵顺序通过鉴定。MC型中浓浆泵（又称螺旋式无堵塞泵）的叶轮采用独特的螺旋叶片和离心叶片一体化结构，使该泵同时具有容积泵和离心泵的特性，可输送高浓度、高粘性液体。输送纸浆浓度可达12呢，带干物质的污水浓度13％，泥浆和纤维浓度14拓。它对浆料、杂质的抽吸能力、通过能力及泵的效率均明显优于离心杂质泵和旋流泵，吸程高，抗汽蚀性能好，可输送固、液、气三相混合物。该泵可广泛用于造纸、纺织、印染、市政排污、医药、食品、冶炼等工程的中高浓度纸…     

叶片修圆对蜗壳式轴流泵反转作透平的性能影响

为了利用轻化工行业中低扬程、大流量的液体余压能,以国内某企业生产的一台比转速为900的PLK XII型蜗壳式轴流泵为研究对象。对模型泵叶片的进口边和出口边分别进行了修圆处理(即在叶片的背面、工作面和叶顶的交线处倒圆角),建立叶片无修圆、进口修圆、出口修圆和进出口同时修圆4种叶轮的三维模型,然后使用ANSYS ICEM对模型进行非结构化四面体网格划分,并基于ANSYS Fluent对不同方案进行CFD定常数值模拟计算,得到了泵工况和透平工况下的外特性以及内部流动信息。研究表明:叶片进口处修圆会使模型泵的效率提升0.78%,但因为叶片有效面积的减少,扬程降低1.6%,轴功率降低1.5%。叶片出口修圆会使液力透平的效率提升0.92%,水头降低1.25%,轴功率降低1.31%。叶片进口修圆后进口附近的压力和速度分布得到了一定的改善,并且减小了叶片工作面的低压区面积,降低了汽蚀发生的可能性。     

钝尾缘叶片三维建模方法的研究

钝尾缘风力机翼型目前被多数用于大型风力机叶片叶根与最大弦长处,这是因为气动上,钝尾缘翼型能够提高升力系数斜率、降低翼型不敏感性;而结构上,钝尾缘翼型与相同厚度翼型相比增加了截面面积和转动惯量[1],论文依据钝尾缘特点,提出设计钝尾缘翼型方案,并以58米长度叶片为例,设计钝尾缘翼型形状,以及此区域主模型的分模方式,完成三维模型建立,为后续有限元建模及模具加工制造提供基础。     

基于钝尾缘翼型叶片的三维风力机性能分析

随着风力机向大型化发展,为有效提升风力机叶片的性能以及结构强度,将钝尾缘翼型应用于风力机叶片设计。以NACA639XX系列翼型为基准翼型,通过Hicks-Henne型函数和钝尾缘函数对翼型进行参数化拟合,使用多岛遗传算法优化得到层流钝尾缘翼型族(USST-XXX)。将此翼型族中相对厚度为21%的USST-211翼型与NACA63921层流翼型替换NREL PhaseVI叶片截面的S809翼型,建模得到两种三维风力机叶片,采用数值模拟的方法,对这两种叶片不同风速下的流场进行分析,并与NREL Phase VI风力机叶片的气动性能进行对比。数值模拟结果表明,在额定风速附近,采用层流钝尾缘翼型所构造的新叶片风力机的风能利用系数高于其他两种叶片。研究结果表明优化得到的层流钝尾缘翼型族可以有效提升风力机气动性能,在大型水平轴风力机叶片设计方面具有良好的应用前景。     

Dynamic stress analysis of sewage centrifugal pump impeller based on two-way coupling method

Current research on the operational reliability of centrifugal pumps has mainly focused on hydrodynamic instability. However, the interaction between the fluid and structure has not been sufficiently considered; this interaction can cause vibration and dynamic stress, which can affect the reliability. In this study, the dynamic stresses in a single-blade centrifugal pump impeller are analysed under different operating conditions; the two-way coupling method is used to calculate the fluid-structure interaction. Three-dimensional unsteady Reynolds-averaged Navier-Stokes equations are solved with the SST k-o9 turbulence model for the fluid in the whole flow passage, while transient structure dynamic analysis is used with the finite element method for the structure side. The dynamic stresses in the rotor system are computed according to the fourth strength theory. The stress results show that the highest stress is near the loose bearing and that the equivalent stress increases with the flow rate because the dynamic stresses are closely related to the pressure load. The stress distributions on the blade pressure side, suction side, leading edge, and trailing edge are each analysed for different flow rates; the highest stress distribution is found on the pressure side. On the blade pressure side, a relatively large stress is found near the trailing edge and hub side. Based on these results, a stress distribution prediction method is proposed for centrifugal pumps, which considers the interaction between the fluid and structuxe. The method can be used to check the dynamic stress at different flow rates when optimising the pump design to increase the pump reliability.     

叶片后缘加厚对轴流风机性能的影响

为解决NACA65系列翼型叶片后缘轮廓线内切圆半径收敛至0引起的铸造工艺问题,采用三次多项式函数生成叶片后缘厚度函数,精确调整叶片后缘末端厚度.基于Ansys软件对不同叶片后缘厚度的风机进行流体仿真,并分析其气动性能与静力结构特性.结果表明叶片后缘增厚使得叶片附面层分离损失增加,尾迹与叶栅主流区的掺混损失增大.叶片载荷...     

应用复合进化算法的叶栅气动优化设计方法的研究

采用结合进化算法和单纯形法的复合进化算法为优化算法,对跨音速轴流压气机叶栅进行气动优化设计。气动性能评价采用Reynolds平均Navier Stokes方程求解技术,采用Baldwin Lomax紊流模型封闭求解的方程。优化设计目标是最大化静压比。设计变量是叶栅型线的Bezier曲线控制点坐标。优化设计结果表明优化设计得到的叶栅具有高静压比和良好的气动性能,同时证明了复合进化算法是一种高效寻优算法。     

微型轴流式血泵叶轮流场CFD计算分析

通过对人工血泵中血液的流体动力分析,计算血液流场的结构和流动性能,可以较好地了解设计血泵的血液流动和流场对血液造成的损伤。本文通过对一种微型轴流式血泵叶轮流场采用CFD方法进行了计算和分析,结论:计算了该叶轮在满足正常人体供血时的工作转速和驱动功率,为磁耦合驱动的设计提供了理论数据;血液经过螺旋叶片,速度分布梯度变小,有利于血液的均匀流动,减少了对血液的破坏,叶轮流场结构基本合理。但是,叶轮边缘间隙处存在局部高剪切区,由于局部压差的存在,流场在出口处出现局部回流。     

后缘小翼智能旋翼有限偏角减振效果分析

建立了适合带后缘小翼的缩比模型智能旋翼减振优化分析方法。考虑小翼运动引起的气动力和惯性力对旋翼系统的影响,建立带后缘小翼的旋翼气动弹性分析模型,使用一种高效的代理模型方法计算带后缘小翼的翼型气动力。使用隐式梯形公式求解气弹耦合动力学方程得到桨叶的弹性响应,采用力积分法计算桨叶剖面振动载荷与桨毂载荷。以小翼操纵输入为设计变量,以桨毂载荷幅值为目标函数建立优化问题,使用最速下降法求解最佳减振效果对应的小翼偏转规律。结果表明本模型计算的结构与气动载荷可靠,对不同前进比状态,后缘小翼都能有效降低桨毂垂向振动载荷。使用直接约束法和目标权重法都能模拟小翼偏转能力不足的情况,小翼偏转能力对减振效果有明显影响,偏转能力不足时后缘小翼仍具有一定的减振效果。     

Influence of blade thickness on transient flow characteristics of centrifugal slurry pump with semi-open impeller

As the critical component, the impellers of the slurry pumps usually have blades of a large thickness. The increasing excretion coefficient of the blades affects the flow in the impeller resulting in a relatively higher hydraulic loss, which is rarely reported. In order to investigate the influence of blade thickness on the transient flow characteristics of a centrifugal slurry pump with a semi-open impeller, transient numerical simulations were carried out on six impellers, of which the meridional blade thickness from the leading edge to trailing edge varied from 5-10 mm, 5-15 mm, 5-20 mm, 10-10 mm, 10-15 mm, and 10-20 mm, respectively. Then, two of the six impellers, namely cases 4 and 6, were manufactured and experimentally tested for hydraulic performance to verify the simulation results. Results of these tests agreed reasonably well with those of the numerical simulation. The results demonstrate that when blade thickness increases, pressure fluctuations at the outlet of the impeller become severe. Moreover, the standard deviation of the relative velocity in the middle portion of the suction sides of the blades decreases and that at the outlet of the impeller increases. Thus, the amplitude of the impeller head pulsation for each case increases. Meanwhile, the distribution of the time-averaged relative flow angle becomes less uniform and decreases at the outlet of the impeller. Hence, as the impeller blade thickness increases, the pump head drops rapidly and the maximum efficiency point is offset to a lower flow rate condition. As the thickness of blade trailing edge increases by 10 mm, the head of the pump drops by approximately 5 m, which is approximately 10 % of the original pump head. Futhermore, it is for the first time that the time-averaged relative flow angle is being considered for the analysis of transient flow in centrifugal pump. The presented work could be a useful guideline in engineering practice when designing a centrifugal slurry pump with thick impeller blades.

     

AERODYNAMIC OPTIMIZATION FOR TURBINE BLADE BASED ON HIERARCHICAL FAIR COMPETITION GENETIC ALGORITHMS WITH DYNAMIC NICHE

A global optimization approach to turbine blade design based on hierarchical fair competition genetic algorithms with dynamic niche (HFCDN-GAs) coupled with Reynolds-averaged Navier-Stokes (RANS) equation is presented. In order to meet the search theory of GAs and the aerodynamic performances of turbine, Bezier curve is adopted to parameterize the turbine blade profile, and a fitness function pertaining to optimization is designed. The design variables are the control points' ordinates of characteristic polygon of Bezier curve representing the turbine blade profile. The object function is the maximum lift-drag ratio of the turbine blade. The constraint conditions take into account the leading and trailing edge metal angle, and the strength and aerodynamic performances of turbine blade. And the treatment method of the constraint conditions is the flexible penalty function. The convergence history of test function indicates that HFCDN-GAs can locate the global optimum within a few search steps and have high robustness. The lift-drag ratio of the optimized blade is 8.3% higher than that of the original one. The results show that the proposed global optimization approach is effective for turbine blade.     

An investigation on the effects of irregular airfoils on the aerodynamic performance of small axial flow fans

In this paper, the effects of airfoils on the aerodynamic performance of small axial flow fans were investigated to reduce airflow turbulence on the blade surface and to improve the aerodynamic performance of small axial flow fans. Irregular airfoils where several convex grooves are bound in the blade pressure surface of the fans have two kinds. The wave-shaped edge is bound to the blade trailing edge of the fans and is designed from the smooth airfoil of the fans. The filtered N-S equations with the finite volume method and the standard k-? turbulence model were adopted to carry out the steady simulation calculation. The large eddy simulation and the FH-W noise models were adopted to carry out the unsteady numerical calculation and aerodynamic noise prediction. The results of simulation calculation are in good agreement with the tests, which proves that the numerical calculation method is feasible. The spectrum characteristics of aerodynamic noise of the smooth airfoil and the two kinds of irregular airfoils were analyzed. Although the fans of the three airfoils are regarded as noise sources, the vortex distribution features in the unsteady flow field are also described. Noise reduction mechanisms of the irregular designs of the airfoils were also discussed. The results of this research may provide proof of the parameter optimization and the structural design of small axial flow fans with low noise.