A FAST LAGRANGIAN SIMULATION METHOD FOR FLOW ANALYSIS AND RUNNER DESIGN IN PELTON TURBINES

In the present work,an alternative numerical methodology is developed for a fast and effective simulation and analysis of the complex flow and energy conversion in Pelton impulse hydro turbines.The algorithm is based on the Lagrangian approach and the unsteady free-surface flow during the jet-bucket interaction is simulated by tracking the trajectories of representative fluid particles at very low computer cost.Modern regression tools are implemented in a new parameterization technique of the inner bucket surface.Key-feature of the model is the introduction of additional terms into the particle motion equations to account for various hydraulic losses and the flow spreading,which are regulated and evaluated with the aid of experimental data in a Laboratory Pelton turbine.The model is applied to study the jet-runner interaction in various operation conditions and then to perform numerical design optimization of the bucket shape,using a stochastic optimizer based on evolutionary algorithms.The obtained optimum runner attains remarkably higher hydraulic efficiency in the entire load range.Finally,a new small Pelton turbine(150 kW) is designed,manufactured and tested in the Laboratory,and its performance and efficiency verify the model predictions.     

EFFECT OF ENLARGED FREE JET ON ENERGY CONVERSION IN PELTON TURBINE

NOMENCLATURE Q —flow rate H— head Dref —diameter of pitch circle B —inner width of bucket ω —angular speed of runner QDH —unit discharge Sn —needle strokesn—relative needle stroke Dinj —diameter of injector inlet Dt —diameter of nozzle throat D     

NUMERICAL PREDICTION OF SILT ABRASIVE EROSION IN HYDRAULIC TURBINE

1.INTRODUCTIONTherearemanyhydraulicturbinesoperatedinsiltladenriversintheworld.Thepresenceofsolidparticlesintheflowoftencauseabrasivedegradationofcertainpartsofthehydraulicturbinewhichareespeciallyexposedtotheflow.Theerosivewearduetohydroabrasiondependsprimarilyonthesurfacematerialandonthematerialoftheabrasiveparticlesinwater.Thefluiddynamicsoftheparticlemotionalsoplayaveryimportantroleinthistribologicalsystem.Therelativevelocityofparticlesandthefrequencyofimpactarekeyfactorsindetermining…     

NUMERICAL PREDICTION OF VORTEX FLOW IN HYDRAULIC TURBINE DRAFT TUBE FOR LES

The three-dimensional unsteady turbulent flow is studied numerically in the whole flow passage of hydraulic turbine, and vortex flow in the draft tube is predicted accurately in this paper. The numerical prediction is based on the Navier-Stokes equations and Large-Eddy Simulation （LES） model. The SIMPLE algorithm with the body fitted coordinate and tetrahedroid grid system is applied for the solution of the discretization governing equations.     

NUMERICAL MODELING PURIFICATION PERFORMANCE OF POT TEST

A three-dimensional mathematical model was developed to simulate the pollutant removal efficiency of the soil and plants in the pot test. The advection, dispersion, diffusion, adsorption, biochemical reaction and plant uptake processes were taken into account in the model. The three-dimensional modified Richards equation was used in simulating flow field. The mass balance law was employed in deriving the equation for pollutant transport, where the diffusion and dispersion were described with the Fick-type law, the adsorption was macroscopically expressed as form isotherm, and the bio-chemical degradation process was assumed to follow the Monod kinetics. The mathematical model was descretized by the finite element numerical method. In the pot test, the hydraulic loading was assumed to have the intermittent pattern simulating the rainfall duration and the occurrence of frequency, and the concentrations of pollutants in the influent and effluent were measured. The computed overall removal rates for the COD_Cr and TN in four cases are in the range of 90.62% ? 95.43% and 85.01% ? 96.46%, respectively. The differences between the computed and tested overall removal rates for the COD_Cr and TN are smaller than 5%. The time-varying oscillation pattern of the concentrations of the COD_Cr and TN were rationally simulated, which showed that the model presented in this article could be used to assess the pollutant removal efficiency of the soil and plants in related cases.     

STUDIES ON GREY MODEL DYNAMIC PREDICTION TO CAVITATION DAMAGE OF TURBINES

1 .　INTRODUCTION[1,2 ]Withthedevelopmentofhydroelectricpowerindustry ,therehaveappearedatendencyofusinghighheadsaswellaslargedischarge ,whichmayleadtoseriouscavitationdamageofturbines .Cav itationdamageandfailuresofturbineshaveoc curedfrequentlyinhydroelectric power projectsbothathomeandabroad .Itsmechanismiscom plexanditsinfluencingfactorsarenumerous ,suchasflowvelocity ,flow pressure ,fluctuating pres sure ,qualityofwater ,manufacturingtechnologyofturbines ,structuralcharacteristicsando…     

玛依纳水电站现场水轮机效率试验

水轮机效率是水轮机性能的重要指标,流量测量是原型水轮机效率试验中最重要、测试难度最大、测点较多的环节。介绍了流量测量的常用试验方法、测量原理、综合误差,并以哈萨克斯坦玛依纳水电站（采用冲击式水轮机）为例,重点介绍了相对法和超声波法的试验原理、现场应用情况、试验结论及注意事项。研究结果表明：对于在不具备热力学法和内置式超声波流量计测量流量的玛依纳水电站,应当采用相对法和外夹式超声波流量计来测量流量。根据该建议,成功实现了大管径、大壁厚管道流量的准确测量,取得的原型水轮机效率试验结果,得到了业主方的认可。     

NUMERICAL SIMULATION AND ANALYSIS OF PRESSURE PULSATION IN FRANCIS HYDRAULIC TURBINE WITH AIR ADMISSION

In this article, the three-dimensional unsteady multiphase flow is simulated in the whole passage of Francis hydraulic turbine. The pressure pulsation is predicted and compared with experimental data at positions in the draft tube, in front of runner, guide vanes and at the inlet of the spiral case. The relationship between pressure pulsation in the whole passage and air admission is analyzed. The computational results show: air admission from spindle hole decreases the pressure difference in the horizontal section of draft tube, which in turn decreases the amplitude of low-frequency pressure pulsation in the draft tube; the rotor-stator interaction between the air inlet and the runner increases the blade-frequency pressure pulsation in front of the runner.     

NUMERICAL PREDICTION OF SUBMARINE HYDRODYNAMIC COEFFICIENTS USING CFD SIMULATION

The submarine Hydrodynamic coefficients are predicted by numerical simulations.Steady and unsteady Reynolds Averaged Navier-Stokes(RANS) simulations are carried out to numerically simulate the oblique towing experiment and the Planar Motion Mechanism(PMM) experiment performed on the SUBOFF submarine model.The dynamic mesh method is adopted to simulate the maneuvering motions of pure heaving,pure swaying,pure pitching and pure yawing.The hydrodynamic forces and moments acting on the maneuvering submarine are obtained.Consequently,by analyzing these results,the hydrodynamic coefficients of the submarine maneuvering motions can be determined.The computational results are verified by comparison with experimental data,which show that this method can be used to estimate the hydrodynamic derivatives of a fully appended submarine.     

A NOVEL DESIGN OF COMPOSITE WATER TURBINE USING CFD

This paper presents computational investigation of a novel design of composite material axial water turbine using Computational Fluid Dynamics(CFD).Based on three-dimensional numerical flow analysis,the flow characteristics through the water turbine with nozzle,wheel and diffuser are predicted.The extract power and torque of a composite water turbine at different rotating speeds were calculated and analyzed for a specific flow speed.The simulation results show that using nozzle and diffuser can increase the pressure drop across the turbine and extract more power from available water energy.These results provide a fundamental understanding of the composite water turbine,and this design and analysis method is used in the design process.     

NUMERICAL CALCULATION OF SOLID-LIQUID T WO PHASE FLOW BETWEEN STAY VANES IN HYDRAULIC TURBINE

1.　INTRODUCTIONMany phenomena of silt-laden water flow can be seen in most rivers of China.Theabrasion of silt-laden water flow to hydraulic turbine has become the most concern forhydraulic power station or pump station.It is always of interest to many engineers andresearchers because of its seriously destroying to the blade ofhydraulic turbine.And mostoftheir works are mainly the performance effect caused by silt-laden water flow,namely thestudy ofouter characteristic.Surface coatisful…     

THE HYDRODYNAMIC CHARACTERISTICS OF FREE VARIABLEPITCH VERTICAL AXIS TIDAL TURBINE

The hydrodynamic characteristics of free variable-pitch vertical axis tidal turbine are investigated by combining experime-ntal and numerical simulations.The variations of hydrodynamics are obtained based on testing the kinematics and the dynamics of the turbine under different flow and structural conditions.Through analyzing the movement of the turbine and the characteristics of the flow field by numerical simulations,it is shown how the turbine’s performance is improved.     

FLUID DYNAMIC PERFORMANCE OF GROOVED PLANING BOAT AND ITS EFFECT ON RESISTANCE

NOMENCLATUREφ———stress tensor of fluid n———unit vector of inner normal onSsurfaceRf———frictional resistanceRr———residuary resistanceα———angle of attack(°)Fτ———resultant force of viscosity tangencystressL———hydrodynamic liftU———speed of uniformity incoming flowV———speed of hull surfaceLp———length of chine projectedVg———speed of groove top surfacenZ→———unit vector projection of outer normalalong axesZonSsurfaceZ0———highness of water surface(Z)…     

NUMERICAL ANALYSIS OF THE PERFORMANCE OF HORIZONTAL AND WAVY SUBSURFACE FLOW CONSTRUCTED WETLANDS

A three-dimensional numerical model is proposed for modeling the TP transport in the Horizontal Subsurface Flow(HSSF) and Wavy subsurface Flow(WSSF) constructed wetland in this article.Both numerical simulations and physical experiments indicate that the removal efficiency of WSSF is higher than that of HSSF.The difference of performance in removing pollutants,e.g.,Total Phosphorus(TP),between HSSF and WSSF is numerically analyzed from three interactive aspects,that is,the hydraulic behavior,the substrate a...     

EXPERIMENTAL INVESTIGATION OF CHARACTERISTIC FREQUENCY IN UNSTEADY HYDRAULIC BEHAVIOUR OF A LARGE HYDRAULIC TURBINE

The features of unsteady flow such as pressure variation and fluctuation in a large hydraulic turbine usually lead to the instability of operation.This article reports the recent in site investigation concerning the characteristic frequencies in pressure fluctuation,shaft torsional oscillation and structural vibration of a prototype 700 MW Francis turbine unit.The investigation was carried out for a wide load range of 200 MW-700 MW in the condition of water head 57 m-90 m.An extensive analysis of both time-history and frequency data of these unsteady hydraulic behaviours was conducted.It was observed that the pressure fluctuation in a draft tube is stronger than that in upstream flow passage.The low frequency with about one third of rotation frequency is dominative for the pressure fluctuation in part load range.Also the unsteady features of vibration of head cover and torsional oscillation of shaft exhibited the similar features.Numerical analysis showed that the vibration and oscillation are caused by vortex rope in the draft tube.In addition,a strong vibration with special characteristic frequency was observed for the head cover in middle load range.The pressure fluctuation in the draft tube with the same frequency was also recorded.Because this special vibration has appeared in the designed normal running condition,it should be avoided by carefully allocating power load in the future operation.     

灯泡贯流式水轮发电机组电厂的厂用电问题

针对灯泡贯流式水轮发电机位于水下和转动惯量小的特点，从该类型水电站厂用电的可靠性出发，提出了灯泡贯流式水轮发电机组电厂在与电力系统联系薄弱的情况下必须考虑设置厂用电的保安备用电源问题．并分析了保安备用电源的取得方式及厂用电接线．     

乌溪江水电厂机组状态检修的思考

为提高水电机组的经济效益和市场竞争力，最大限度地延长机组检修周期，降低检修运行成本，必须开展状态检修。文中简要介绍了乌溪江水电厂实施状态检修的原则和总体思路，着重阐述了为实现总体思路所进行的机组状态检修的探索、规划和实施情况，以及目前开展机组状态检修存在的问题，进而阐明了最终乌溪江水电厂所有设备状态检修的目标。     

NUMERICAL PREDICTION OF LINE BUOYANT JETS IN CROSS FLOWS

1 .　ＩＮＴＲＯＤＵＣＴＩＯＮＡｂｕｏｙａｎｔｊｅｔｉｓｄｅｆｉｎｅｄａｓａｓｏｕｒｃｅｏｆｂｕｏｙａｎｔｆｌｕｘａｎｄｉｎｉｔｉａｌｍｏｍｅｎｔｕｍｏｒｖｏｌｕｍｅｆｌｕｘｅｓ .Ｌｏｎｇｍｕｌｔｉｐｏｒｔｏｃｅａｎｓｅｗｅｒｔｈｅｏｕｔｆａｌｌｄｉｆｆｕｓｅｒｓｃａｎｂｅａｌｗａｙｓａｐｐｒｏｘｉｍａｔｅｄａｓｔｗｏ ｄｉｍｅｎｓｉｏｎａｌｌｉｎｅｂｕｏｙａｎｔｊｅｔｓ .Ｂｕｔｆｏｒｔｈｅｌｉｎｅｂｕｏｙａｎｔｊｅｔｓｏｆｆｉｎｉｔｅｌｅｎｇｔｈ ,ｔｈｅｄｉｓｐｅｒｓｉｏｎｏｆｔｈｅｄｉｓｃｈａ…     

NUMERICAL MODELING OF COMPOUND CHANNEL FLOWS

A numerical model capable of predicting flow characteristics in a compound channel was established with the 3-D steady continuity and momentum equations along with the transport equations for turbulence kinetic energy and dissipation rate. Closure was achieved with the aid of algebraic relations for turbulent shear stresses. The above equations were discretized with implicit difference approach and solved with a step method along the flow direction. The computational results showing the lateral distribution of vertical average velocities and the latio of total flow in the compound channel agree well with the available experimental data.     

NUMERICAL SIMULATION OF THE HYDRODYNAMIC PERFORMANCE OF AN UNSYMMETRICAL FLAPPING CAUDAL FIN

A comprehensive numerical simulation of the hydrodynamic performance of a caudal fin with unsymmetric flapping motion is carried out. The unsymmetrical motion is induced by adding a pitch bias or a heave bias. A numerical simulation program based on the unsteady panel method is developed to simulate the hydrodynamics of an unsymmetrical flapping caudal fin. A CFD code based on Navier-Stokes equations is used to analyze the flow field. Computational results of both the panel method and the CFD method indicate that the hydrodynamics are greatly affected by the pitch bias and the heave bias. The mean lateral force coefficient is not zero as in contrast with the symmetrical flapping motion. By increasing the pitch bias angle, the mean thrust force coefficient is reduced rapidly. By adding a heave bias, the hydrodynamic coefficients are separated as two parts: in one part, the amplitude is the heave amplitude plus the bias and in the other part, it is the heave amplitude minus the bias. Analysis of the flow field shows that the vortex distribution is not symmetrical, which generates the non-zero mean lateral force coefficient.