Comparisons between numerical calculations and measurements in vaned diffuser of SHF impeller

The paper presents analysis of the performance and the internal flow behaviour in the vaned diffuser of a radial flow pump using PIV(particle image velocimetry)and pressure probe traverses.PIV measurements have already been performed at middle height inside one diffuser channel passage for a given speed of rotation and various mass flow rates.These results have been already presented in several previous communications.New experiments have been performed using a three-hole pressure probe traverses from hub to shroud diffuser width at different radial locations between the two diffuser geometrical throats.Numerical simulations are also realized with the commercial codes Star CCM+7.02.011 and CFX.Frozen rotor and fully unsteady calculations of the whole pump have been performed.Comparisons between numerical results,previous experimental PIV results and new probe traverses one's are presented and discussed for one mass flow rate.In this respect,a first attempt to take into account fluid leakages between the rotating and fixed part of the pump has been checked since it may affects the real flow structure inside the diffuser.

Design of a Centrifugal Compressor with Low Solidity Vaned Diffuser(LSVD) for Large-Scale Compressed Air Energy Storage(CAES)

Compressed Air Energy Storage(CAES) has tremendous promotional value in the intermittent renewable energy supply systems. CAES has special requirements for compressor(e.g. heavy load, high pressure ratio, wide range). With advantages of higher efficiency and wider operation range, IGC(Integrally Geared Compressors) is selected to fulfill the special requirements of the large-scale CAES. To get a better aerodynamic performance, in this paper, based on the analysis of internal flow of centrifugal compressor, a multi-objective one-dimensional optimization design program was put forward combined with modified Two-Zone model and a low solidity vaned diffuser(LSVD) design method. Then, a centrifugal compressor aerodynamic component optimization design system was established with the three-dimensional blade optimization design method based on neural network and genetic optimization algorithm. Then a validation was done by redesigning the Krain-Impeller to get better performance. Finally, the aerodynamic design of the first stage of IGC was completed. The CFD calculation results indicated that the total-to-total pressure ratio of the first stage was 2.51 and the polytropic efficiency was 91.0% at the design point. What’s more, an operation margin and surge margin of the compressor was about 26.5% and 16.4% respectively.

Numerical Investigation of the Centrifugal Compressor Stability Improvement by Half Vaned Low Solidity Diffusers

Centrifugal compressors for the fuel cell vehicles often operate near the surge line compared with the turbocharger compressors.Low solidity and half vaned diffusers are recognized as good ways to improve the stability of the centrifugal compressor.The presented work investigated four diffuser configurations (i.e.,the vaneless diffuser (VLD),full-height low solidity vaned diffuser (LSVD),hub-side half vaned diffuser (HVD) and shroud-side half vaned diffuser (SVD)) through steady-state and unsteady numerical simulations.The results show that the best performance is achieved by the LSVD,HVD and SVD at the design,surge and choke conditions.The flow rate at the surge operating point of the HVD has decreased by 15.53% compared with the LSVD,and 9.21% compared with the VLD.At near surge operating point,a longitudinal suction side passage vortex is formed on the hub of the LSVD and rotates as circumferential stall cells.A hairpin vortex is formed along the leading edge and is dragged by the main flow along the suction side as a local vortex shedding.The mechanism of the stability improvement by half vaned diffusers is that the tip leakage vortex migrates from the clearance side to the vane mounting side and replenishes the low-momentum zone on the mounting side.The best position where the half vaned diffuser should be mounted is based on the impeller outlet flow conditions,namely,the location of the wake region,where the meridional velocity and relative stagnation pressure is low.

Optimum Profiles of Endwall Contouring for Enhanced Net Heat Flux Reduction and Aerodynamic Performance

Successfully utilized non-axisymmetric endwalls to enhance turbine efficiencies(aerodynamic and turbine inlet temperatures)by controlling the characteristics of the secondary flow in a blade passage.This is accomplished by steady-state numerical hydrodynamics and deep knowledge of the field of flow.Because of the interaction between mainstream and purge flow contributing supplementary losses in the stage,non-axisymmetric endwalls are highly susceptible to the inception of purge flow exit compared to the flat and any advantage rapidly vanishes.The conclusions reveal that the supreme endwall pattern could yield a lowering of the gross pressure loss at the design stage and is related to the size of the top-loss location being productively lowered.This has led to diminished global thermal exchange lowered in the passage of the vane alone.The reverse flow adjacent to the suction side corner of the endwall is migrated farther from the vane surface,as the deviated pressure spread on the endwall accelerates the flow and progresses the reverse flow core still downstream.The depleted association between the tornado-like vortex and the corner vortex adjacent to the suction side corner of the endwall is the dominant mechanism of control in the contoured end wall.In this publication,we show that the non-axisymmetric endwall contouring by selective numerical shape change method at most prominent locations is advantageous in lowering the thermal load in turbines to augment the net heat flux reduction as well as the aerodynamic performance using multi-objective optimization.

Applications of Additively Manufactured Adjustable Vaned Diffusers in Centrifugal Compressor

As a variable-condition adjustment technology,the adjustable vaned diffusers(AVDs)can expand the working flow range of the compressor in the compressed air energy storage(CAES)system and improve its aerodynamic performance.In order to investigate the regulatory mechanism of AVDs and capture the details of vane loading distribution for the diffuser design optimization,additively manufactured AVDs for testing in a centrifugal compressor closed test facility are designed and implemented.Firstly,the regulation law of AVDs was summarized by numerical analysis and experimental support,and the corresponding vane loading data was extracted for the distribution law.Then,based on the distribution characteristics,3D diffuser models were designed suitably for the adjustable components.Then,the laser selective melting(SLM)technology and die steel material 1.2709 were selected for metal printing according to the actual operating environment.Finally,performance testing and accuracy detection were performed on the finished test pieces,almost all inlet hole’s deviations were within the 0.3 mm tolerance.The research results indicated that additive manufacturing can significantly improve the accessibility of the internal flow channels of the diffuser,and derive the load of the blade on the pressure surface and suction surface in detail,also provide adjustable functions for variable operating conditions.It can not only break through the traditional processing bottleneck of the complicated internal flow channels of AVDs but also improve the design matching degree with adjustable components;simultaneously,it ensures high performance with high precision and effectively shortens the long lead time.

Performance prediction and flow analysis in the vaned distributor of a pump turbine under low flow rate in pump mode

The main goal of this work is to investigate the possible different flow patterns existing in pump turbine under off-design conditions in pump mode. Numerical simulations by solving the Navier-Stokes equation, coupled with the "SST k-ω" turbulence model, were carried out. Flow characteristics were assumed to be stalled in the appropriate region of ?ow rate levels of Q/QD=0.15–0.61. The simulation result was compared with experimental data and they showed good agreement. Consequently, velocity fields in three axial locations in stay vanes and guide vanes were analysed in details. It was shown that "jet-wake" flow pattern exists near the band, which changes little in the whole shape with flow rate increasing; to the middle location of vanes, reverse flow begins to appear on the interface between the runner and guide vanes, which will disappear gradually as the flow rate increases; massive reverse flow is captured near the crown, whose intensity will be weakened as the flow rate increases. Ultimately, it was found that the special head-flow profile can be ascribed to the special hydraulic loss characteristics of the stay vanes and guide vanes.

3D Vane⁃XD⁃mDixon序列在胸椎增强MRI中的应用效果评价

目的探究3D⁃VANE⁃XD⁃mDixon序列在胸椎增强核磁共振成像(MRI)成像中对图像质量的影响及其应用价值。方法收集临床怀疑胸椎病变患者63例,行常规胸椎MRI后补充3D⁃T1WI⁃mDixon⁃TSE及3D⁃Vane⁃XD⁃mDixon序列。计算并测量两种扫描序列图像的椎体信噪比(SNR)、对比噪声比(CNR),并采用5分法对图像进行主观评分,比较两个序列对胸椎的诊断价值。结果在客观评分方面,3D⁃Vane⁃XD⁃mDixon序列图像与T1WI⁃mDixon⁃TSE序列图像的SNR分别为258.30(41.63,1982.67),133.05(18.90,584.34);CNR分别为114.67(22.32,740.17),23.44(6.44,224.77)。3D⁃Vane⁃XD⁃mDixon序列的SNR、CNR均高于T1WI⁃mDixon⁃TSE序列(Z=-4.042,P<0.001;Z=-4.107,P<0.001)。在主观评分方面,2名诊断医师对T1WI⁃mDixon⁃TSE和3D⁃Vane⁃XD⁃mDixon图像主观评分分别为3.03±0.53,3.09±0.47;4.17±0.50,3.96±0.69。3D⁃Vane⁃XD⁃mDixon序列(kappa=0.723)与T1WI⁃mDixon⁃TSE(kappa=0.685)的一致性均较好(kappa>0.61),具体表现为3D⁃Vane⁃XD⁃mDixon序列图像的整体质量评分明显优于T1WI⁃mDixon⁃TSE序列图像,且差异具有统计学意义(P<0.001)。结论使用3D⁃Vane⁃XD⁃mDixon序列,可明显提高胸椎增强图像质量,为疾病诊断提供精准的图像信息。

Numerical and experimental study on the particle erosion and gas–particle hydrodynamics in an integral multi-jet swirling spout-fluidized bed

In this paper,using the computational fluid dynamics based on Euler Lagrange and the commercial software Barracuda VR,the gas-particle hydrodynamics and the erosion of particles on the inner wall and internal components of the spouted bed in the integrated multi-jet swirling spout-fluidized bed(IMSSFB)are studied.Erosion experiments have obtained the characterization of particle erosion on internal components and verified the relevant numerical models.The results show that:the particle distribution within the IMSSFB is uneven due to the cyclonic effect of the axial swirl vane(ASV),resulting in particle erosion for the ASV being concentrated on one side;when the gas reaches the top,too high an erosion gas velocity leads to gas backflow.As the filling height increases,there is a tendency for the erosion position of the particles on the ASV to expand upwards.However,the effect of increasing gas velocity on the erosion position is insignificant.

船体风机叶片对中速船水动力性能影响的计算分析

The importance of reducing ship resistance is growing considerably as a result of the increase in atmospheric emissions and the drive towards green shipping through decarbonization.Until this point,Energy Saving Devices(ESD),in particular,Hull Vane®(HV),have been widely applied as a potential technique for reducing wave-making resistance for vessels with higher Froude Number(Fr).The advantages of HV for a medium-speed vessel,where the wave-making component accounts for almost 50%of total resistance,have yet to be investigated.This study presents the computational analysis of the KCS model(1∶75.5);for a particular trim condition by using the VOF method and RANS solver.The hull acts as a candidate vessel for the class of medium-speed characteristics.A total of 36 numerical simulations were carried out to study the changes in resistance and motion characteristics of the vessel with and without HV.To validate the numerical setup,the experimental work of Hou et al(2020)on the DTMB hull was used.The effectiveness of HV can be comprehended by the reduction percentage in total resistance,trim,sinkage,and transom wave height,in comparison to bare hull condition.The reduction in total resistance extends up to 6%for Fr=0.32 with configuration 2 with negative AoF.The CFD results indicate that there is a reduction in trim up to 57%for the maximum speed with a corresponding Fr=0.34 with a positive angle of foil(AoF).The trim correction effect is increasing with the depth of submergence of HV.Concerning sinkage,there occurs nearly a 31%reduction for Fr=0.34 with a positive AoF.There exists a substantial reduction in the height of the transom wave with the inclusion of HV,the results of which are discussed in detail.From the presented results,retrofitting the Hull Vane®is effective in the selected speed range but pronouncing as the speed of the vessel increases.

VSV系统对CFM56发动机喘振的影响分析

航空发动机喘振是发动机衰退过程中的常发的故障,而发动机VSV系统的工作状态直接影响发动机的喘振裕度。以CFM56—3发动机的VSV系统为研究对象,讨论其工作机理,分析其对处于衰退期的CFM56—3发动机稳定工作的影响,提出相应的维修注意事项。从而为研究以VSV故障为诱因的喘振提供理论依据,为相关维修提供工程参考。

Influence of propagation direction on operation performance of rotating detonation combustor with turbine guide vane

Due to the pressure gain combustion characteristics,the rotating detonation combustor(RDC)can enhance thermodynamic cycle efficiency.Therefore,the performance of gas-turbine engine can be further improved with this combustion technology.In the present study,the RDC operation performance with a turbine guide vane(TGV)is experimentally investigated.Hydrogen and air are used as propellants while hydrogen and air mass flow rate are about 16.1 g/s and 500 g/s and the equivalence ratio is about 1.0.A pre-detonator is used to ignite the mixture.High-frequency dynamic pressure transducers and silicon pressure sensors are employed to measure pressure oscillations and static pressure in the combustion chamber.The experimental results show that the steady propagation of rotating detonation wave(RDW)is observed in the combustion chamber and the mean propagation velocity is above 1650 m/s,reaching over 84%of theoretical Chapman-Jouguet detonation velocity.Clockwise and counterclockwise propagation directions of RDW are obtained.For clockwise propagation direction,the static pressure is about 15%higher in the combustor compared with counterclockwise propagation direction,but the RDW dominant frequency is lower.When the oblique shock wave propagates across the TGV,the pressure oscillations reduces significantly.In addition,as the detonation products flow through the TGV,the static pressure drops up to 32%and 43%for clockwise and counterclockwise propagation process respectively.

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.

Sensitivity analysis of the vane length and passage width for a radial type swirler employed in a triple swirler configuration

The design of axial or radial swirlers typically governs a number of geometrical parameters that are determined by the desired flow field.In the meantime,the number of unknown parameters increases with the number of concentrically mounted swirlers.The available literature is nonetheless limited,and designers are obligated to increase the number of initial assumptions.In this article,three kinds of triple swirlers are employed and simulations are performed to determine the effect of each parameter on the swirler performance.Based on the correlation provided,overlengthening the radial vane length could result in significant changes in the flow field from the jetlike pattern to a wide swirl-jet angle due to the Coanda effect.Passage width should also have the potential to alter the swirl-jet angle and velocity field at the exit of the swirler.

Settling,consolidation and shear strength behaviour of coal tailings slurry

The volume change and shear strength behaviour of tailings slurry with the changes in gravimetric moisture content is important to effectively utilise the storage volume and analysis of dam failure potential.Consolidation testing of tailings from a slurry-like to soil-like state is a critical task,and conventional consolidation apparatus does not have the capability of doing such testing,as the tailings slurries contain high water content.Settling tests conducted on slurries having a 25%solids concentration showed very low efficiency;final sediment was still slurry-like.An intrinsic point was identified based on pore water pressure dissipation during consolidation tests in a slurry consolidometer that can define two states of the tailings i.e.slurry-like and soil-like.In the slurry-like state,the volume change was greater for Slurry 2 than Slurry 1,while the inverse was observed in the soil-like state.The evolution of peak vane shear strength with the changes in moisture content was almost similar for both samples and obeyed the power function.Regression models have been developed and validated to predict the shear strength of materials at any gravimetric moisture content or void ratio.

Investigation on Mechanical Characteristics of Air Jet Acting on Nozzle Vanes of VNT

Extensive experimental studies are performed using force sensors to measure actuating forces of nozzle ring devices of variable nozzle turbines. Torques from pneumatic action applied onto axles of nozzle vanes have been calculated. Test results obtained through repeated experiments are quite congruent,confirming the effectiveness of this simple method. Results have indicated that,with a fixed opening angle of guide vane,pneumatic torque increases with mass flow of air jet in the turbine; moreover,under the same mass flow rate,torque decreases with reducing opening angle,even possibly change direction down to negative. The results have also provided a modus operandi for designing nozzle-adjusting devices as well as validation data for numerical study on changes of pneumatic torque onto guide vanes under full engine operating conditions.

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.

Erosion Characteristics of Hydraulic Turbine Guide-Vane End Clearance in Sediment Water Flow: A Simplified Model Analysis

The effect of clearance flow on the erosion characteristics of a circular cylinder with a backward facing step in sediment-laden water flow is analyzed numerically with the mixture model and the re-normalization group (RNG) k-ε turbulence model. Thirty-six monitoring points are set up on different stream surfaces to collect information on the impact erosion under different flow conditions, where the Initial Sediment Volume Fraction (ISVF) is set to 0.05, 0.075, 0.1, 0.125, and 0.15;particle diameter is set to 0.05 mm, 0.15 mm, 0.25 mm, 0.35 mm, and 0.45 mm respectively. The distribution of particle velocity and Local Solid-Phase Volume Fraction (LSVF) along different stream surfaces are calculated, based on which the trend of erosion is qualitatively evaluated. ISVF and particle diameter play different roles on the impact erosion index parameter () on the different wetted walls. Relative wear rate of numerical estimation agrees well with the practical one under the same working condition. Numerical analysis demonstrates that guide vane with a negative curvature end surface (concave surface) can decrease erosion damage effectively, which may provide a reference for optimal design and maintenance of hydraulic turbine.

A Novel Wind Energy Conversion System with Storage for Spillage Recovery

This paper proposes a new system configuration for integrating a compressed air energy storage system with a conventional wind turbine. The proposed system recycles the mechanical spillage of blades and stores it for later electricity generation with assistance from a rotary vane machine. The configuration and operational policy is explained, and a comparative case study shows that the proposed system recovers investment costs through savings on electricity procurement and revenue through power export.

Determining the Scour Dimensions Around Submerged Vanes in a 180°Bend with the Gene Expression Programming Technique

Submerged vanes are installed on rivers and channel beds to protect the outer bank bends from scouring.Also,local scouring occurs around the submerged vanes over time,and identifying the effective factors on the scouring phenomena around these submerged vanes is one of the important issues in river engineering.The most important aimof this study is investigation of scour pattern around submerged vanes located in 180°bend experimentally and numerically.Firstly,the effects of various parameters such as the Froude number(Fr),angle of submerged vanes to the flow(α),angle of submerged vane location in the bend(θ),distance between submerged vanes(d),height(H),and length(L)of the vanes on the dimensionless volume of the scour hole were experimentally studied.The submerged vanes were installed on a 180°bend whose central radius and channel width were 2.8 and 0.6 m,respectively.By reducing the Froude number,the scour hole volume decreased.For all Froude numbers,the biggest scour hole formed atθ=15°.In all models,by increasing the Froude number,the scour hole volume significantly increases.In addition,by increasing the submerged vanes’length and height,the scour hole dimensions also grow.Secondly,using gene expression programming(GEP),a relationship for determining the scour hole volume around the submerged vanes was provided.For this model,the determination coefficients(R2)for the training and test modes were computed as 0.91 and 0.9,respectively.In addition,this study performed partial derivative sensitivity analysis(PDSA).According to the results,the PDSA was calculated as positive for all input variables.