Influence of Blade Number on the Performance of Hydraulic Turbines in the Transition Stage

To analyze the effect of blade number on the performance of hydraulic turbines during the transient stage in which theflow rate is not constant,six hydraulic turbines with different blade numbers are considered.The instantaneous hydraulic performance of the turbine and the pressure pulsation acting on the impeller are investigated numerically by using the ANSYS CFX software.The ensuing results are compared with the outcomes of experimental tests.It is shown that thefluctuation range of the pressure coefficient increases with time,but the corresponding range for the transient hydraulic efficiency decreases gradually when theflow velocity transits to larger values.During the transition to smallflow velocity,thefluctuation range of the pressure coefficient gradually decreases as time passes,but the correspondingfluctuation range of its transient hydraulic efficiency gradually becomes larger.Thefluctuation range in the Z9 case is small during the transition.The main frequency of transient hydraulic efficiency pulsation is equal to the blade frequency.At the main frequency,Z7 has the largest amplitude of the hydraulic efficiency pulsation,Z10 has the smallest amplitude,and the difference between Z7 and Z9 is limited.As the number of blades grows,the pressure pulsation during the transition process gradually decreases,but the pressure pulsation of Z10 at the volute tongue is larger.In the steady state,Z9 has the highest efficiency and in the transient stage,the pressure coefficientfluctuation range is small.Accordingly,for the hydraulic turbine Z9,the performance is optimal.

Numerical investigation on the flow and power of small-sized multi-bladed straight Darrieus wind turbine

Straight Darrieus wind turbine has attractive characteristics such as the ability to accept wind from random direction and easy installation and maintenance. But its aerodynamic performance is very complicated,especially for the existence of dynamic stall. How to get better aerodynamic performance arouses lots of interests in the design procedure of a straight Darrieus wind turbine. In this paper,mainly the effects of number of blades and tip speed ratio are discussed. Based on the numerical investigation,an assumed asymmetric straight Darrieus wind turbine is proposed to improve the averaged power coefficient. As to the numerical method,the flow around the turbine is simulated by solving the 2D unsteady Navier-Stokes equation combined with continuous equation. The time marching method on a body-fitted coordinate system based on MAC (Marker-and-Cell) method is used. O-type grid is generated for the whole calculation domain. The characteristics of tangential and normal force are discussed related with dynamic stall of the blade. Averaged power coefficient per period of rotating is calculated to evaluate the eligibility of the turbine.

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.

Feasibility analysis for monitoring fatigue crack in hydraulic turbine blades using acoustic emission technique

In order to investigate the feasibility of monitoring the fatigue cracks in turbine blades using acoustic emission (AE) technique, the AE characteristics of fatigue crack growth were studied in the laboratory. And the characteristics were compared with those of background noise received from a real hydraulic turbine unit. It is found that the AE parameters such as the energy and duration can qualitatively describe the fatigue state of the blades. The correlations of crack propagation rates and acoustic emission count rates vs stress intensity factor (SIF) range are also obtained. At the same time, for the specimens of 20SiMn under the given testing conditions, it is noted that the rise time and duration of events emitted from the fatigue process are lower than those from the background noise; amplitude range is 49-74 dB, which is lower than that of the noise (90-99 dB); frequency range of main energy of crack signals is higher than 60 kHz while that in the noise is lower than 55 kHz. Thus, it is possible to extract the useful crack signals from the noise through appropriate signal processing methods and to represent the crack status of blade materials by AE parameters. As a result, it is feasible to monitor the safety of runners using AE technique.

Hydraulic turbine system identification and predictive control based on GASA-BPNN

Based on the characteristics of nonlinearity,multi-case,and multi-disturbance,it is difficult to establish an accurate parameter mod-el on the hydraulic turbine system which is limited by the degree of fitting between parametric model and actual model,and the design of con-trol algorithm has a certain degree of limitation.Aiming at the modeling and control problems of hydraulic turbine system,this paper proposes hydraulic turbine system identification and predictive control based on genetic algorithm-simulate anneal and back propagation neural network(GASA-BPNN),and the output value predicted by GASA-BPNN model is fed back to the nonlinear optimizer to output the control quantity.The results show that the output speed of the traditional control system increases greatly and the speed of regulation is slow,while the speed of GASA-BPNN predictive control system increases little and the regulation speed is obviously faster than that of the traditional control system.Compared with the output response of the traditional control of the hydraulic turbine governing system,the neural network predictive control-ler used in this paper has better effect and stronger robustness,solves the problem of poor generalization ability and identification accuracy of the turbine system under variable conditions,and achieves better control effect.

Computer Simulation of Turbulent Flow through a Hydraulic Turbine Draft Tube

Based on the Naviev-Stokes equations and the standard κ-ε turbulence model, this paper presents the derivation of the governing equations for the turbulent flow field in a draft tube. The mathematical model for the turbulent flow through a draft tube is set up when the boundary conditions, including the inlet boundary conditions, the outlet boundary conditions and the wall boundary conditions, have been implemented. The governing equations are formulated in a discrete form on a staggered grid system by the finite volume method. The second-order central difference approximation and hybrid scheme are used for discretization. The computation and analysis on internal flow through a draft tube have been carried out by using the simplee algorithm and cfx-tasc flow software so as to obtain the simulated flow fields. The calculation results at the design operating condition for the draft tube are presented in this paper. Thereby, an effective method for simulating the internal flow field in a draft tube has been explored.

Study on Contra-Rotating Small-Sized Axial Flow Hydro Turbine

It is thought that small hydropower generation is alternative energy, and the energy potential of small hydropower is large. The efficiency of small hydro turbines is lower than that of large one, and these small hydro turbine’s common problems are out of operation by foreign materials. Then, there are demands for small hydro turbines to keep high per- formance and wide flow passage. Therefore, we adopted contra-rotating rotors which can be expected to achieve high performance and low-solidity rotors with wide flow passage in order to accomplish high performance and stable opera- tion. Final goal on this study is development of an electric appliance type small hydro turbine which has high portability and makes an effective use of the unused small hydro power energy source. In the present paper, the performance and the internal flow conditions in detail of contra-rotating small-sized axial flow hydro turbine are shown as a first step of the research with the numerical flow analysis. Then, a capability adopting contra-rotating rotors to an electric appliance type small hydro turbine was discussed. Furthermore, the high performance design for it was considered by the numeri- cal analysis results.

A Fatigue Analysis of a Hydraulic Francis Turbine Runner

In this work, the estimation of crack initiation life of a hydraulic Francis turbine runner is presented. The life prediction is based on the local strain approach to predict the initiation life. First, the analysis is carried out in air and in water condition and the runner’s natural frequencies were calculated using the finite element (FE) method. The analysis in air is compared with experimental analysis in order to have a representative model of real runner and subsequently the numerical analysis was perform in water. In the case of the runner immersed in water, the added mass effect due to the fluid structure interaction (FSI) is considered. Second, the static and dynamic stresses were calculated according to life estimation. For the calculation of static stresses, the pressure distribution of water and the centrifugal forces were applied to the runner. The dynamic stresses were estimated for interactions between the guide vane and the runner. Lastly, the estimation of the crack initiation life of the runner was obtained.

A real-time measuring technology for studying distortion of hydraulic turbine blade castings during heat treatment process

During heat treatment process, the distortion behavior inevitably appears in hydraulic turbine blade castings. In this research, a technology was developed for real-time measurement of the distortion in hydraulic turbine blade castings at the still air cooling and forced air cooling stages during heat treatment process. The method was used to measure the distortion behavior at the cooling stages in both normalizing and tempering processes. At the normalization, the distortion at the blade comer near outlet side undergoes four stages with alternating bending along positive and negative directions. At the tempering stage, the distortion could be divided into two steps. The temperature difference between the two surfaces of blade casting was employed to analyze the distortion mechanism. The measured results could be applied to guide the production, and the machining allowance could be reduced by controlling the distortion behavior.

Influence of Different Transition Modes on the Performances of a Hydraulic Turbine

In order to analyze the response of a hydraulic turbine to a variation in the operating conditions,different laws of variation in time of the massflow rate have been considered.After validating the overall numerical framework through comparison with relevant experiments,the performances of the considered turbine have been analyzed from afluid-dynamic point of view.The results show that different time profiles of the massflow rate(in this work,for simplicity,referred to as“transition functions”)have a varying influence on the transient behavior of the turbine.When a quadratic function is considered for the case of largeflow,the transient head and torque increase gradually with time,thefluctuation amplitude of the transient hydraulic efficiency at the main frequency is the largest,and thefluctuation amplitude of the radial force is the smallest.For the smallflow case,the time profile with exponential nature leads to the best results.The transient head and torque decrease gradually with time,the pulsation amplitude of the transient hydraulic efficiency is the largest at the main frequency,and the pulsation amplitude of the radial force is the smallest.

2D Model of Guide Vane for Low Head Hydraulic Turbine： Analytical and Numerical Solution of Inverse Problem

Low-head hydraulic turbines are the subjects to individual approach of design. This comes from the fact that hydrological conditions are not of a standard character. Therefore, the design method of the hydraulic turbine stage has a great importance for those who may be interested in such an investment. As a first task in a design procedure the guide vane is considered. The proposed method is based on the solution of the inverse problem within the flame of 2D model. By the inverse problem authors mean a design of the blade shapes for given flow conditions. In the paper analytical solution for the simple cylindrical shape of a guide vane is presented. For the more realistic cases numerical solutions according to the axis-symmetrical model of the flow are also presented. The influence of such parameters as the inclination of trailing edge, the blockage factor due to blade thickness, the influence of loss due to dissipation are shown for the chosen simple geometrical example.

Two Concepts of Guide Vane Profile Design for a Low Head Hydraulic Turbine

Two concepts of the guide vanes channels design for a low head hydraulic turbine were investigated using 2D and 3D models. Model 2D was used to generate the geometry of profiles which form a blade channel. After that by means of 3D commercial code （ANSYS/Fluent v. 15）, the designed cascades were examined. The characteristic parameters of compared guide vanes have been presented. The problem of low head hydraulic turbine design is important from the technical point of view for usually not typical environmental circumstances, in which the hydropower plants are planned.

Prediction of Hydraulic Stability of Francis Turbines of Three Gorges Hydropower Station

The Francis turbine of Three Gorges hydropower station is one of the large turbines with great head variation in the world. The operational stability of the turbine has been the top subject for departments of design, research, manufacture and operation to be concerned about. During the course of preparing bid invitation documents and executing the contract for the Three Gorges left power plants turbogenerator units, the hydraulic stability of the turbine was regarded as the most important problem and specific stability indexes of the model turbine and the prototype turbine were respectively specified in the contract. In the model tests for turbine model acceptance, pressure fluctuation phenomena in the case of partial load were found to be different from the usual ones as people had known. Within the range of operating water head, there existed a peak value zone of pressure fluctuations with higher frequencies, and large amplitude pressure fluctuations simultaneously occurred in several localities from the spiral case entrance to the draft tube. On the basis of test results from the model, the influence of cavitation coefficient and aeration on pressure fluctuations is analyzed, and some measures to improve the hydraulic stability of turbines of Three Gorges hydropower station are expounded.

A Feasibility Study of Power Generation from Sewage Using a Hollowed Pico-Hydraulic Turbine

This study is concerned with the feasibility of power generation using a pico-hydraulic turbine from sewage flowing in pipes. First, the sewage flow rate at two connection points to the Toyogawa River-Basin Sewerage, Japan, was explored for over a year to elucidate the hydraulic energy potential of the sewage. Second, the performance of the pico-hydraulic turbine was investigated via laboratory experiments that supposed the turbine to be installed in the sewage pipe at the connection points. This study indicates that the connection points have hydraulic potential that can be used for power generation throughout the year. It also demonstrates that the pico-hydraulic turbine can be usefully employed for power generation from sewage flowing in the pipe at the connection points.

Terminal Sliding Mode Controllers for Hydraulic Turbine Governing System with Bifurcated Penstocks under Input Saturation

Terminal sliding mode controller method is introduced to enhance the regulation performance of the hydraulic turbine governing system(HTGS).For the purpose of describing the characteristics of controlled system and deducing the control rule,a nonlinear mathematic model of hydraulic turbine governing system with bifurcated penstocks(HTGSBF)under control input saturation is established,and the input/output state linearization feedback approach is used to obtain the relationship between turbine speed and controller output.To address the control input saturation problem,an adaptive assistant system is designed to compensate for controller truncation.Numerical simulations have been conducted under fixed point stabilization and periodic orbit tracking conditions to compare the dynamic performances of proposed terminal sliding mode controllers and conventional sliding mode controller.The results indicate that the proposed terminal sliding mode controllers not only have a faster response and accurate tracking results,but also own a stronger robustness to the system parameter variations.Moreover,the comparisons between the proposed terminal sliding mode controllers and current most often used proportional-integral-differential(PID)controller,as well its variant NPID controller,are discussed at the end of this paper,where the superiority of the terminal sliding mode controllers also have been verified.

Simulink/MATLAB Model for Assessing the Use of a Centrifugal Pump as a Hydraulic Turbine

A centrifugal pump used as a hydraulic turbine in producing power for a microhydropower system is multifaceted. Centrifugal pumps are far more ubiquitous than turbines in the turbomachinery market, therefore being more readily available to the consumer. Additionally, they are cheaper. Hydraulic turbines undergo rigorous CFD simulation design and testing to establish their blade geometries and ranges of operation. This results in a refined but very expensive final product. Centrifugal pumps are thus presented as a logical alternative seeing that they can physically perform the same task as a hydropower turbine albeit at a reduced efficiency. This paper presents the results of an analysis and simulation to assess the use of a centrifugal pump as a hydraulic turbine.

Giant Hydraulic Turbine Runner under construction

Four giant hydraulic turbines of Yantan Hydropower Sta-tion located on the Hongshui River,Guangxi Provinceare now under construction by the Harbin Electric Machinery Works(HEMW)of China Harbin Power-Plant Equipment Corporation(GROUP).The turbine will become the largest in dimension forFrancis type turbine ever made in China.The external diameter ofthe runner is 8.6 m,which is supposed to be ranked No.3 among thelargest runners of this category in the world.Each turbine is

WC-M coating to improve resistance of hydraulic turbines to cavitation erosion and abrasion

WC M hard faced ceramic coating was made on the substrate of steel by means of high velocity oxygen fuel flame (HVOF) thermal spraying. The resistance of this coating to cavitation erosion and abrasion (CEA) is about 2.5 times higher than that of 188 stainless steel, and is about 1.5 times higher than that of Stellite alloy (CoCrWC) made in America. When this coating were applied to the hydraulic power stations with more silt content in the flow water, which reaches 50 kg/m 3, the resistance of above mentioned coating to CEA was about 2 times to that of NiCr alloy coating, and is about 45 times to that of OCr13Ni4Mo stainless steel. In addition, the micro hardness, microstructures and electron probe analyzing of the WC M coating are all discussed.

基于SimHydraulics的兆瓦级风机液压型变桨系统仿真

基于MATLAB/SimHydraulics工具箱,对兆瓦级风机的液压型变桨系统进行了仿真研究。借助SimHydraulics工具箱内建的液压元器件模型,可以直接对变桨系统的液压原理图进行建模与仿真。仿真结果表明:利用SimHydraulics工具箱对兆瓦级风机变桨系统进行仿真研究的可行性,为进一步对风力发电机组全工况仿真提供了保证。

Numerical Study of the Effect of Splitter Blades on the Flow-Induced Noise of Hydraulic Turbine

In order to study the effect of splitter blades on the internal and external sound field of the hydraulic turbine,the paper chose a centrifugal pump with a specific speed ns=33 reversed as a hydraulic turbine as the research object,and added the short blades on the original impeller to form a new splitter impeller.Based on the Re-Normalization Group(RNG)k-εturbulence model to conduct numerical simulation for the hydraulic turbine,this thesis calculated the internal and external acoustic field by means of the acoustic boundary element(BEM)and finite element(FEM)and analyzed the noise radiation characteristics of the two models under different working conditions.The results show that the blade frequency is the main factor affecting the inlet and outlet sound pressure,and the optimized model decreases the inlet and outlet sound pressure levels by 6.84 and 7.24 dB in optimal working conditions.Rotor-stator interaction is the main reason for the flow-induced noise of hydraulic turbine volute appearing,the optimized model can effectively reduce the impeller and volute rotor-stator interaction and the flow-induced noise of volute.Outfield maximum sound pressure appears at the inlet and the volute tongue,which decreased by 1.84,6.07,and 5.24 dB at each operating condition.To sum up,splitter blades can improve hydraulic characteristics and flow field noise in the hydraulic turbine.