基于流固耦合的离心泵启动过程瞬态叶片动应力特性

为研究离心泵启动过程的叶片的应力和变形情况,针对IS65-50-160的离心泵启动过程瞬态内部流场和结构场进行了双向流固耦合联合求解。其中流场计算基于RANS方程与SST湍流模型;结构场计算基于弹性体结构动力学方程;对叶轮叶片在双向流固耦合作用下的变形和应力分布进行了计算,获得了离心泵启动过程中瞬时效应对叶片应力和应变的影响规律。研究结果表明:叶片的最大等效应力和应变呈振荡上升趋势,振动强度先减小后增大;在离心泵启动过程中,叶片进口与后盖板的交界处出现应力集中,叶片的变形量从后盖板到前盖板呈递增的趋势;叶片的最大等效应力和应变量都大于稳态工况下的最大等效应力和应变量。     

基于流固耦合方法的跨声速叶片气动和强度性能研究

为研究流固耦合对跨声速压气机叶片气动和强度性能的影响,采用商用软件ANSYS-CFX/Multiphysics研究了跨声速叶片在气动力和离心力共同作用下的气动性能变化规律,通过单向和双向两种耦合方法对比分析了叶片的强度性能。结果表明:叶片在气动力和离心力共同作用下,叶尖前缘变形量最大,气动性能与冷态叶片相比有明显变化,叶尖激波位置前移,堵塞流量增大。双向流固耦合与单向耦合相比,叶片的总体变形量增大约1.1%,最大等效应力增大0.8%左右。研究结果表明工程设计应采用双向流固耦合方法进行叶片气动性能设计和强度校核,以提高压气机的安全性和可靠性。     

分流叶片离心泵非定常流动及动力学特性分析

为了研究在流固耦合作用下分流叶片对低比转数离心泵内部非定流动及结构动力特性的影响,以高温熔盐泵为研究对象,采用计算流体力学软件ANSYS CFX12.1和有限元软件ANSYS Workbench对有/无分流叶片的两种方案高温熔盐泵,进行了考虑泵内部流场和结构场的相互作用的双向流固耦合求解。对比分析了两种方案对泵非定常流动及结构动力特性的影响,结果表明:流固耦合作用使得各监测点的压力脉动和径向力脉动规律和幅值均发生了明显变化,说明在该类泵的流场模拟中,流固耦合作用较明显,不可忽视;分流叶片的添置减小了流场内压力脉动及径向力脉动幅值;带分流叶片转子的变形量变化梯度、等效应力变化梯度、最大变形量及最大应力值均小于不带分流叶片转子,且带分流叶片转子等效应力随时间的变化也明显小于不带分流叶片转子。即分流叶片的添置不仅有利于提高转子的承载能力,而且还有利于改善转子的变形和受力,从而提高转子的抗疲劳能力。     

高压气井完井管柱系统的轴向流固耦合振动研究

目前针对石油完井管柱的研究没有考虑瞬变流诱发的管柱运动,而实际的管柱与管内流体存在相互影响、相互作用。对完井管柱系统流固耦合振动响应进行了初步分析与探索,给出了适用于气井完井管柱流固耦合分析的数学模型,提供了采用特征线法对耦合模型进行解耦以及采用插值方法进行数值求解的具体过程,并以现场数据为例,预测分析了天然气不稳定流动引起的流体压力、管柱应力、管柱振动速度的耦合响应过程。研究结果表明：天然气不稳定流动使管柱处于交变应力状态,并诱发管柱往复运动,这将加剧完井管柱结构的疲劳破坏与磨损破坏。该结果对预防完井管柱先期实效有实际工程意义     

潮流能水轮机叶轮压力脉动特性分析

潮流能水轮机周围流场的压力脉动是影响水轮机运行稳定性的关键因素之一。基于CFD单、双向流固耦合方法和滑移网格技术,对水平轴潮流能水轮机叶轮实施了三维数值模拟。通过分析水轮机周围流场的非定常流动,得到了三种不同工况下叶轮的应变特征、各监测点的水压力脉动和频域振动特性。计算结果显示:双向流固耦合计算得到的最大变形量与最大应力值均较单向流固耦合时略大,随着水流速度的增加,叶轮叶片的应变量增幅与有效应力增幅逐渐降低;水轮机的压力脉动幅值由叶尖到叶根基本呈递减趋势;水轮机压力脉动的主频率集中在相应工况的叶频附近,且水轮机叶片背面的压力脉动比正面的波动程度要剧烈。     

弯曲输流管道流固耦合动力特性分析

管道中流体和弹性体之间的相互作用是引起管道振动的主要原因,这种流固耦合作用对管道动力特性有直接影响。以流固耦合理论为基础,对脉动压力作用下的弯曲输流管道建立流体动力学模型及固体运动模型,在ANSYS Workbench中分别进行双向流固耦合受力分析、单双向流固耦合对比分析和模态分析,并考虑脉动压力,壁厚和管径等参数的影响。结果表明,弯管最大应力发生在入口和出口附近上下部,最大变形发生在转角及中间处;双向耦合作用下弯管最大等效应力与最大变形量均大于单向耦合;双向耦合作用下弯管固有频率明显降低,且固有频率随壁厚和管径的增大呈非线性增长。     

离心泵噪声研究的综述和展望

回顾了离心泵噪声研究的国内外现状。首先总结了离心泵噪声的来源,并对离心泵噪声来源的研究进行分类评述：机械结构影响离心泵噪声的研究,包括蜗壳几何形状与叶轮影响离心泵噪声的研究;流体动力影响离心泵噪声的研究,包括对汽蚀、流固耦合与湍流诱发噪声的研究。而后从离心泵诱发噪声的数学模型推导、数值计算与试验研究三个方面对研究离心泵噪声所使用的方法进行了总结;最后讨论了目前研究存在的一些问题和今后的研究方向。     

不同曲率情况下的液压管道流固耦合特性仿真研究

管道布局影响流体流动特性与管道应力分布。利用有限元方法对不同曲率情况下管道的流固耦合特性进行了分析,研究了流固耦合作用对不同曲率管道位置等效应力的影响。研究结果表明:流体对弯曲管道在弯曲壁面产生额外的作用力导致管道发生变形,且角度的改变会导致两端进出口位置应力发生较大的波动;管道曲率变化对弯管在弯曲附近位置应力影响较大,随着弯曲角度的增加管道弯曲处应力先减小后增大再减小,而内侧和两侧的应力改变幅度不同;管道曲率半径的改变会影响管道的受力分布。通过分析得出管道布局按R30(R/d=1.5)相比其他管道的模型布局更为合理的结论。     

不同湍流模型下旋转叶片气固耦合动力学特性的研究

本文对轴流式压气机内旋转叶片在不同湍流模型的气固耦合作用下的动力特性进行了研究。利用FSI（fluid-structure interaction）的双向顺序耦合算法,采用CFX和ANSYS对压气机内气体和旋转叶片分别计算,并通过迭代求解,获得叶片在气流作用下的动力学响应。为了研究耦合场内对叶片动力特性的影响,本文对某一级转子叶片进行流固耦合计算,由于在模拟流场计算中,不同的湍流模型对计算结果影响较大,采用3种湍流模型：标准κ-ε湍流模型(standard κ-ε)、重正化群κ-ε湍流模型（renormalization group κ-ε,RNG κ-ε）和大涡湍流LES模型（Large eddy simulation）,获得了叶片在瞬态流场变化下的动力特性,并比较了不同湍流模型对计算的影响,为工程上对压气机内转子工作特性的分析提供一个可行的方法。     

大跨柔性空间结构风压和耦合风效应分析

研究大跨柔性空间结构的表面风压和流固耦合风效应.引入流体运动控制方程和大涡模拟湍流模式,提出风与结构的流固耦合方程的迭代求解过程.提出张拉索膜结构的加载预应力态、稳定态和耦合态等三个受载状态概念和统一形式的动力方程表达.以某典型索穹顶结构为例,采用以风时程为荷载的动力响应时程方法、单向耦合算法和双向耦合算法,开展结构风效应的数值计算和比较.研究发现,动力响应时域方法和单向耦合算法的结构平均位移计算结果基本相同,但前者的结构风振系数较大.双向耦合算法的结构平均位移计算结果小于前两种方法,但风振系数在三种方法中最大.     

Experimentelle Analyse der Leckageströmung an Deckbändern einer Niedergeschwindigkeits-Axialturbine bezüglich der Strömungsverteilung und der Leistung

The experimental investigation of the influence of different shrouds on the aerodynamics and the efficiency of an axial turbine is the objective of this work. The flow- and pressure measurements are presented for two geometrically different shrouds in a 1,5-stage axial turbine. One case deals with a shroud, which covers the blade completely in axial direction. A second case consists of a shortened shroud with less weight, which leaves the inlet and outlet of the blade tip unshrouded. As a result a pressure-loss analysis along the flow channel is presented. Furthermore the distributions of pressure-loss coefficient and the aerofoil circulation of the rotor blade along the channel height are calculated in the rotating frame of reference from the measurements. The variation of the shroud geometry influences the flow near the trailing-edge plane at the rotor outlet. Finally the influences for both shrouds are compared in performance and efficiency under two different loadings. The shortened shroud of decreased weight leads to up to 5 percent loss in efficiency and 11 percent loss in performance.     

Fatigue failure analysis of holding U-bolts of a cooling fan blade

Fatigue failure of holding U-bolt of a cooling fan blade is analyzed. Fractography of the fracture surface reveals the characteristics of a fatigue fracture. Finite element modeling is used for stress analyzing. Analysis of the loading conditions indicates that the bolts are under multiaxial fatigue. Effective alternating and mean stresses are obtained based on the multiaxial fatigue criteria. By using the modified Goodman approach and considering the notch effect, effective stress amplitude, is obtained for all nodes. The highest stress amplitude is obtained at six critical nodes. Fatigue life for the most critical node is determined as 3.63 million cycles.     

Inverse design optimisation of a novel range hood based on intelligent algorithms and computational fluid dynamics simulations

Our aim in the present study is to increase grease separation by optimising the discharge performance of cooking oil fumes. A novel range hood with an outer cylinder and guide vanes of exhaust (GVE) is proposed. The geometric configuration of the hood is optimized by a reverse design method developed by coupling back propagation neural networks, mind evolutionary algorithms, and computational fluid mechanics. The primary objective of the range hood is to maximise the exhaust airflow rate with good grease separation. At the optimised conditions, the inlet and outlet blade angles are 80° and 176°, respectively, while the heights of the blade and guide vane are 0.180 and 0.245 m, respectively. The optimal number of blades and guide vanes are 29 and 7, respectively, while the optimal diffuser diameter is 0.340 m. The proposed range hood exhibits excellent performance of grease particle separation compared to multi-blade centrifugal fans with volutes. In addition, the outer cylinder and GVE of the range hood exhibit a large separation efficiency for particles in the size range of 1–4 μm, while impeller blades mainly separate grease particles in the size range of 4–10 μm.     

Kombination von Radial- und Seitenkanalstufen für Turboverdichter

Unsteady gas pressure oscillations occur at impeller outlet and diffuser of radial and side channel compressors, engendered by the blades grid of the impeller. They have effect beyond the limits of inlet and outlet. If a radial stage is coupled to a side channel stage, then the unsteady gas pressure oscillations of the side channel stage have an effect inside the radial stage affecting flow and characteristic curve. Because of that, the radial stages unstable characteristics and the limit of rotating stall can be moved to lower volume flows or completely suppressed by connecting a side channel stage before or behind it. Therefore the permissible range of operation of combined compressor stages can be extended compared with a radial compressor stage. Moving the limit of rotating stall of the radial compressor stage and lower the gas pressure oscillations caused by Rotating Stall as a result of the side channel stages unsteady gas pressure oscillations will be proved experimental. As a criterion for Rotating Stall in radial compressor stages also the proportion between RMS of gas pressure oscillations and the total pressure increase in the radial compressor stage can be used.     

Investigations on fluid friction of rotational disks with and without modified outlet sections in real centrifugal pump casings

In order to examine the relation between the height of disk friction losses and the geometry of disks in real centrifugal pump housing disks without and with modified outlet sections with various numbers, angles and widths are investigated. Disks with modified outlet sections were examined to approach a real impeller in real centrifugal pump housing. The outlet channels of this impeller are formed out, the rest of channels is replaced by firm material. Experimental results of disks without modified outlet sections show that the disk friction coefficient decreases with the increase of the Reynolds number, but becomes smaller with small values of the disk width and high values of the gap. The inset of the volute has only small influence on disk friction coefficient. Experiments on disk friction conducted with and without the cover of the impeller shroud show that the cover has more influence for high values of the axial gap. Experimental results of disks with modified outlet sections show that the disk friction coefficient don’t changes with the Reynolds number, but generally the number and the angle of the outlet sections of disks have an important influence on the disk friction coefficient.     

多翼离心风机气动噪声的降噪

针对多翼离心风机气动噪声的主要噪声源提出降噪方案。首先,对于多翼离心风机涡流噪声的降噪,主要通过优化叶轮、蜗壳的结构几何参数和在叶轮出口加装旋转扩压器等方式进行。其次,对于多翼离心风机旋转噪声的降噪,主要通过改变蜗舌形式进行。最后对优化进出口安装角的叶轮和在叶轮出口加装旋转扩压器这两种降噪措施进行试验验证。结果表明,改进后的风机与原型相比达到显著的降噪效果。     

Fracture analysis of impeller blade of a locomotive draught-fan

This paper presents the failure analysis of the impeller blade of a locomotive draught-fan. Visual examination indicates that blade was fractured at the 15–33 mm distance from the blade root and the failure mode is instantaneous fracture. Metallurgical observation reveals that the fractured blade had been repair-weld on the upper surface (the convex side) and the lower surface (the concave side) of blade before fracture. Many casting defects produced by welding are presented at the interface between the repair-welding region and the substrate as well as within the repair-welding region. The crack was originated from three large shrinkage cavities at the interface between the repair-welding region and the substrate due to the stress concentration at the pores, and propagated from the concave side toward the convex side of blade. Finite element method (FEM) was utilized to determine the static stress of the blade under operation conditions and dynamic characteristic of blade. FEM results indicate that failure did not occur at the maximum stress area due to static forces and the mechanical resonance of blades did not contribute to blade failure.     

Numerical simulation of a centrifugal slurry pump handling solid-liquid mixture: Effect of solids on flow field and performance

The effect of solids on a centrifugal slurry pump performance is a major concern to the design of slurry transportation system. In the present study, the multiphase modeling of centrifugal slurry pump is performed using two models, Mixture and Eulerian-Eulerian multiphase. Sliding mesh approach is employed for unsteady simulation of the pump. The accuracy of the simulations is ascertained by comparing the performance characteristics of the pump obtained numerically and experimentally. Experimental results are obtained by measurements in a pilot plant test rig with three different mean size sand particulate slurries. The Eulerian-Eulerian multiphase model predicted the effect of the solids on pump performance close to the experimental results as compared to Mixture model. The obtained accuracy with Eulerian-Eulerian model for predicting the effect of solids on head and efficiency is around ±2% and ±3%, respectively. The predicted results using Eulerian-Eulerian model confirm that the head and efficiency of the pump decrease with the increase in particle size and concentration. The particles of high specific gravity show less reduction in head and efficiency of the pump. Further, the effect of variation in particle size and concentration on the flow field in the impeller and casing has also been analyzed at best efficiency point operation. Non-homogeneous suspension of particles inside the blade channels and casing passages is examined. The particulate concentration is observed higher near the impeller back shroud, pressure side of the blades, and non-suction side of the casing as compared to other locations.     

高速离心泵叶片断裂分析

对高速离心泵断裂叶片的材料成分,断口和力学性能进行了分析,确定了其断裂模式为腐蚀疲劳断裂,叶片根部加工粗糙,造成局部应力集中是导致叶片断裂的主要原因,对叶片的结构设计进行了探讨。     

发动机振动对排气歧管低周疲劳寿命影响研究

发动机排气歧管在动态热负荷与整机振动载荷耦合作用的恶劣环境中工作,在热负荷单独作用时其部分区域就已经发生塑性变形,而整机振动载荷的耦合作用将使其疲劳失效问题更为严峻。为量化整机振动载荷对排气歧管低周疲劳损伤的影响,以某三缸增压发动机为研究对象,首先,基于流固耦合方法获得了排气歧管在标定工况和怠速工况下内外流场的换热边界,并联合增压器、催化器等部件温度和换热边界对两工况下排气系统的温度场进行计算。然后,根据温度场计算结果,耦合螺栓预紧力的作用,对怠速工况下的弹性应力场以及标定工况下的弹性和弹塑性应力场进行了计算,并基于标定工况下的弹塑性应力场,应用模态瞬态动力学对标定工况下的整机振动载荷作用下的动应力进行分析。最后,依据标定和怠速工况下的弹性应力场、标定工况下的动应力场结果,参照发动机低周疲劳试验标准分别建立了排气歧管常规高温低周疲劳与整机振动-热耦合低周疲劳分析模型,引入Neuber准则对两者的载荷谱进行应力-应变修正后采用主应变法进行疲劳寿命评估。结果表明：排气歧管疲劳破坏风险点主要位于高温拉应力区域,叠加振动载荷会使整体疲劳寿命下降接近25.2%,部分区域下降幅度甚至高达57%。研究结果为排气歧管整机瞬态振动-热耦合低周疲劳寿命预测提供了一定的理论依据和参考。