Runner Design Research Articles

Effect of tangential absolute velocity at outlet on open flume turbine performance

To address the electricity crisis in Indonesia, the use of open flume pico hydro turbines is a potential solution because Indonesia has 19 GW of hydropower resources at mini, medium, and pico scales. There are two concepts for the design of an open flume pico hydro turbine runner: Euler and Nechleba. Euler’s concept recommends that the absolute tangential velocity at the outlet of the blade be zero to optimise power absorption. By contrast, Nechleba explains that to reduce flow separation at the outlet of the blade (separation can reduce efficiency), tangential absolute velocity at the outlet of the blade must not be zero. Accordingly, this study compares the performance of blades designed with these two concepts using a computational fluid dynamics method. The results showed that the maximum efficiency of the blade using the Euler concept was 70.08%, while the blade using the Nechleba concept was 74.39%. Based on the results, a runner design concept that assumes a non-zero tangential absolute velocity at the outlet of the blade is recommended for use in designing an open flume pico hydro turbine runner.

The effect of wheel and nozzle diameter ratio on the performance of a Turgo turbine with pico scale

A Turgo turbine with a pico scale (<5 kW) is one solution to supplying electrical energy in remote areas because of its low construction costs and ease of maintenance. Based on empirical equations, the ratio of the wheel (D) and nozzle diameter (d), or D∕d, of a Turgo turbine must be determined precisely because it affects wheel velocity, which has an impact on performance and/or efficiency. However, the optimum D∕d ratio has not yet been clearly determined. To find the optimum D∕d ratio for a Turgo turbine with a pico scale that can produce maximum electrical power, this study will examine five variations of the D∕d ratio: 11.6, 13.8, 14.7, 22 and 27.5. In order for this turbine to be implemented in remote areas, coconut shell is proposed as the material for its blades. The results of the analysis, which used a one-way analysis of variance (ANOVA) test with a confidence level of 92.5%, show that the D∕d ratio had a significant influence on performance. Based on the results, aD∕d ratio of 22 produces the highest efficiency – 34.97% with an electric power of 5.34 W (13.21 Vdc ± 0.1 Vdc and 396.4 mA ± 7.46 mA) – compared to the other ratios. Thus, the pico-scale Turgo turbine runner design is optimized​ at the D∕d ratio of 22. Furthermore, coconut shell blades can be implemented for a pico-scale Turgo turbine.

Numerical and Experimental Analysis on Runner and Gate Positioning for Magnesium Alloy Die-Casted Test Piece

High Pressure Die Casting (HPDC) is a manufacturing process producing complex and precise products by injecting molten material into mold cavity at top speed and pressure. The quality of product is highly related with mold cavity design. Casting defects due to inappropriate mold design will affect mechanical properties, surface quality and product life cycle. Optimization of runner system is essential to manufacture complex and precision product design with minimal defects. The combination of runner and gating system is investigated in this paper. This paper investigated the effect of runner and gating optimization in reducing the gas porosity inside casting by evaluating the fluid and thermal distribution behavior in experimental and Computational Fluid Dynamic (CFD). The gas porosity generated in the molten magnesium alloy is due to the turbulent flow and the inconsistency of the fluid flow to push the gas bubble away from the main casting. This paper includes an X-ray of a sample product that shows correlation between gas porosity and CFD results. Results show that localize porosity gathered at the bottom of the main casting. Based on localized porosity position, runner and gating system is modified and numerical simulation is carried out for analysis. An inspection instrument step-type test piece is taken as an investigation sample to illustrate the technique of design modifications and improvements. Process parameters considered in this paper are injection speed, injection pressure, melt temperature and mold temperature. This paper proposed new runner designs that can generate balanced velocity and temperature distribution inside mold cavity, improving the solidification process aimed for reducing casting defects.

Design, Fabrication and Testing of Hydraulic Turbine Runner for a Double Suction Centrifugal Pump in Turbine Mode

Design, Fabrication and Testing of Hydraulic Turbine Runner for a Double Suction Centrifugal Pump in Turbine Mode

Multiscale simulation of erosive wear in a prototype-scale Pelton runner

The technical capacity to predict the erosion process is instrumental for the optimization of the runner designs and operation strategies of hydroelectric plants. A multiscale model of erosion recently formulated by the authors and validated on a laboratory-scale jet impingement case is used to study the erosion of a prototype-scale Pelton runner. The model is shown to provide physically-sound descriptions of the sediment impact condition distributions on the bucket surface; furthermore, the erosion distribution obtained is explained in terms of these underlying impact condition distributions. The model predictions for the erosion depth distribution on the bucket surface are validated with the corresponding experimental data, resulting in an average error of 35% for eight point-wise comparisons, 14% for line-averaged values along four transversal sections, and 4% for the surface-averaged erosion depth, directly linked to the total eroded mass. A careful error propagation analysis of the comparison between simulation and field data yields an uncertainty of ±22%. Based on these considerations, the modeling error is estimated to be 26±22%. The results obtained, namely quantitative predictions of the erosion of industrial-scale hydraulic machines, have no precedent in the literature; they demonstrate the accuracy and transferability of the multiscale model of erosion and suggest an improvement over the state-of-the-art computational fluid dynamics models based on empirical erosion correlations.

Development and Prospect of the Pumped Hydro Energy Stations in China

Pumped hydro energy storage (PHES) has been recognized as the only widely adopted utility-scale electricity storage technology in the world. It is able to play an important role in load regulation, frequency and phase modulation and black starts in power systems. Due to its outstanding functions, this technology has been widely used worldwide.This paper introduces PHES including its functions and the technologies briefly to supply a comprehensive cognition of this technology. The key technologies of PHES, such as design and manufacture of reversible pump-turbine runners, design of heavy-duty thrust bearings and shaft sealings, startup of unit etc., are important for the PHES. In addition, more and more new technologies, such as operation with seawater, underground lower reservoirs, adjustable speed units etc., were put forward and used in PHES to make it perform better.This paper focuses on the development of PHES in China. Thanks to a rapid development of China’s economy in the recent years, PHES has gained a fast development. At present, China has owned the biggest installed capacity (29.9 GW by the end of 2018) of PHES the world. PHES has been an indispensable part of the power grid to increase the stability of the grid and improve the penetration of sustainable energy such as wind power, solar energy etc. With the employment of new technologies. China’s new PHES stations, such as Guangzhou, Tianhuangping, Xilongchi PEHS etc., have become the representatives of the world’s most advanced level. Based on the requirement of the current power grid for PHES, some new PHES have been under construction and more PHES are in the planning and design stage.

Investigation of the effect of gaps between the blades of open flume Pico hydro turbine runners

This study will analyze the impact of gap size in two different runners called runner A (five blades) and B (six blades) to provides recommendations in design and manufacture of open flume turbine runners so that maximize the conversion of kinetic and potential energy. There are three methods was used to investigate its: analytical method is used to design the turbine; experimental to determine the actual turbine performance; computational fluid dynamics (CFD) to study the physical phenomena and re-check the velocity triangle on the runner to validate the design and manufacturing process. Using the results obtained, gaps between the blades can alter the velocity vector on the outlet and unbalance the rotation of runner; this imbalance could cause cavitation. Then, the decreasing torque is assumed because water pressure in the draft tube is similar to atmospheric pressure. Two conditions must be satisfied to maximize the performance of the turbine: swirling flow is required after the water flows past the runner in order to minimize the radial velocity on the outlet so that the draft tube can function properly; the dimensions of the blade must be carefully selected to avoid the formation of gaps between the blades.

On the design of propeller hydrokinetic turbines: the effect of the number of blades

A design study of propeller hydrokinetic turbines is explored in the present paper, where the optimized blade geometry is determined by the classical Glauert theory applicable to the design of axial flow turbines (hydrokinetic and wind turbines). The aim of the present study is to evaluate the optimized geometry for propeller hydrokinetic turbines, observing the effect of the number of blades in the runner design. The performance of runners with different number of blades is evaluated in a specific low-rotational-speed operating conditions, using blade element momentum theory (BEMT) simulations, confirmed by measurements in wind tunnel experiments for small-scale turbine models. The optimum design values of the power coefficient, in the operating tip speed ratio, for two-, three- and four-blade runners are pointed out, defining the best configuration for a propeller 10 kW hydrokinetic machine.

Optimization of the Runner Numerical Design Dimensions using the Simulation Program

The proper design of the gating system including the tempering and venting of the mold significantly influences the final quality of the casting and economize the costs of the foundries. The initial numerical design of the gating system is often sufficient for creating of the documentation for the mold design, but without the practical experience of the designer, it does not reveal the hidden problem emerging from the melt flow through the gating system as well as the temperature and gas mode of the mold.The contribution is dedicated to the optimization of the runner dimensions determined by the numerical calculation. The theoretical part presents the methodology, based on which the gating system was designed for a particular type of the pressure casting. The experimental part is dedicated to the influence of the cross sectional area of the runner on the change of the melt temperature before entering the ingate. It was assumed that the larger runner cross section gives the melt greater volume and heat capacity and thus the melt enters the ingate with the higher temperature. The obtained temperature results are then compared witht he melt flow rate values, based on which an optimal sulotion for the runner design dimensions is determined.

Evaluation of gap influence on the dynamic response behavior of pump-turbine runner

Purpose The gaps between runner and nearby structures play an important role in the dynamic response of runner, especially for pump-turbines. This paper aims to evaluate the gap influence on the added mass and dynamic stress of pump-turbine runner and provide an improved method to predict the resonance of runner. Design/methodology/approach Acoustic-structural coupling method was used to evaluate the added mass factors of a reduced scale pump-turbine with different axial and radial gap size between runner and nearby rigid walls. Improved one-way fluid-structural interaction (FSI) simulation was used to calculate the dynamic stress of the runner, which takes into account fluid added mass effect. The time-dependent hydraulic forces on the runner surfaces that were obtained from unsteady CFD simulation were transferred to the runner structure as a boundary condition, by using mesh-matching algorithm at the FSI surfaces. Findings The results show that the added mass factors increase as the gap size decreases. The axial gaps have greater influence on the added mass factors for the in-phase (IP) modes than the counter-phase (CP) and crown-dominant (CD) modes, while the CP and CD modes are very sensitive to the radial gaps. The largest added mass factor is observed in (2 + 4)ND-CP mode (resonance mode). The results reveal that the transient structural dynamic stress analysis, with the consideration of gaps and fluid added mass, can accurately predict the resonance phenomenon. Resonance curve of the pump-turbine has been obtained which agrees well with the test result. The gap fluid has great influence on the resonance condition, while for non-resonance operating points, the effect of gaps on the dynamic stress amplitude is quite small. Originality/value This paper provides an accurate method to analyze the dynamic response during runner design stage for safety assessment. The resonance curve prediction has more significance than previous methods which predict the resonance of runner by modal or harmonic analysis.

Development of wide operating range runner for Francis turbine upgrading

The proposed paper describes the upgrading procedure of the six units installed at HPP Stejaru in Romania in the sixties of the last century. The power plant is furnished with two identical 55 MW units and four identical 28 MW units. The scope of the upgrading was same for all units, to install new runner and wicket gate assembly into the existing spiral case and draft tube. The paper is focused especially on the procedure of the hydraulic design of the new Francis type runner due to demanding request for unusually wide range of operation for such type of turbine. The most challenging was the condition of adoption of wicket gate height, which was insufficient regarding specific speed of the new runner. The first CFD computations confirmed that the standard design of the runner was not able to fulfill the expected parameters. Therefore, the automatic mathematical designer driven optimization process was applied. The results of the optimization iteration process were confirmed during development tests and finally approved by additional acceptance tests carried out at the neutral laboratory as was required in tender specification. The performance features of the new turbine were found as excellent especially applicable for wide range of operation heads and outputs. Even in the marginal operation there are not expected any troubles with the cavitation or excessive pressure pulsations and turbine vibrations. The manufacturing process of the new components is now in the progress.

Dynamics and stability of running on rough terrains.

Stability of running on rough terrain depends on the propagation of perturbations due to the ground. We consider stability within the sagittal plane and model the dynamics of running as a two-dimensional body with alternating aerial and stance phases. Stance is modelled as a passive, impulsive collision followed by an active, impulsive push-off that compensates for collisional losses. Such a runner has infinitely many strategies to maintain periodic gaits on flat ground. However, these strategies differ in how perturbations due to terrain unevenness are propagated. Instabilities manifest as tumbling (orientational instability) or failing to maintain a steady speed (translational instability). We find that open-loop strategies that avoid sensory feedback are sufficient to maintain stability on step-like terrains with piecewise flat surfaces that randomly vary in height. However, these open-loop runners lose orientational stability on rough terrains whose slope also varies randomly. The orientational instability is significantly mitigated by minimizing the tangential collision, which typically requires sensory information and anticipatory strategies such as leg retraction. By analysing the propagation of perturbations, we derive a single dimensionless parameter that governs stability. This parameter provides guidelines for the design and control of both biological and robotic runners.

Multiobjective optimization design of ultrahigh-head pump turbine runners with splitter blades

The traditional design method, design-experiment-design, is time consuming and difficult. In the present paper, an efficiency design system for pump-turbine runners, the multiobjective optimization design system, which includes 3D inverse design, Computational Fluid Dynamics (CFD), Design Of Experiment (DOE), Radial Basis Function (RBF) and Multi Objective Genetic Algorithm (MOGA), is presented and then applied to design a scaled ultrahigh-head pump turbine runner. First, the control parameters, blade loading and the splitter work ratio, and the runner efficiencies under pump and turbine mode were selected as input variables and optimization objectives respectively. Then the DOE was applied to select the sample runners, and the CFD was used to predict the efficiencies of the sample runners under different modes. The relationship between input variables and objectives was built by RBF based on CFD results. Finally, the MOGA was applied to generate and search the good overall performance runners according to the relationship built by RBF. The results indicate that: the pump mode efficiency of preferred runner is increases by 0.34% and the turbine mode efficiency by 2.07% compared to the initial runner. With the improvement of efficiency, the pressure and streamline distribution are improved obviously.

Optimisation of a pump-as-turbine runner using a 3D inverse design methodology

In this paper the optimisation of a pump-as-turbine runner using a 3D inverse design methodology is presented. The baseline design is based on an existing runner designed with TURBOdesign1 by Zhu et al.[1, 2], that was then optimised by the genetic algorithm in Isight. In the work presented here the baseline design will be further optimised by minimizing secondary flow and profile loss factors while keeping the same meridional profile, stacking characteristics and work distribution in pump mode. The performance curves suggest that minimizing the secondary loss factor leads to an increase of the pump mode efficiency, whereas minimizing the profile loss coefficient benefits the turbine mode efficiency. These results strengthen the understanding of the trade-offs involved and provide guidelines for the design of runners for pump-as-turbine applications.

Experimental research on flow field in the draft tube of pump turbines based on LDV

A large number of pumped storage power plants will be put into operation in China. The current development of modern pump storage power plants aims towards a higher flexibility and stability in operation, and an extended operation range of the hydraulic machine. These projects have a large number of problems. For problems of the turbine units, the optimization of pump turbine is very crucial to ensure the unit’s high efficiency and stability. The velocity distribution on the runner outlet is very important to optimize the pump turbine. In this paper, the velocity on runner outlet was tested by LDV (Laser Doppler Velocimetry). The axial velocity and circumferential velocity on runner outlet were tested at different working points by LDV. The velocity distribution can provide important reference for the runner design.

Refurbishment of twin Francis turbines – maximizing the annual production

Before the invention of the Kaplan turbine, Francis turbines were also built as twin Francis turbines. An example for such a single-regulated horizontal axis twin Francis turbine is the hydro power plant Meitingen – 3 units with an inlet chamber and a single-sided shaft led through. This plant, which is located on a diversion channel, went in operation in 1922 with a nominal power of 11.6 MW for the three machine sets providing an annual production of 72.6 GWh. Due to cracks and cavitation damages, one of the units should be replaced, yet, after a comprehensive study the decision for a major mechanical and electrical refurbishment was taken. The geometry was scanned on-site and a CAD model was generated. The RANS calculation for the whole power plant provided information on the overall performance, the losses referring to each component and the flow situation in each of the turbines. An optimization of the runner design was carried out and an increase of 14.8% of the annual production could be realized. All of the units were brought into operation after the refurbishment and the performance level was checked successfully by means of an on-site efficiency measurement campaign according to IEC 60041.

Simulation of Multi-cavity Micro-injection System for Reducing Cavity Filling Deviation

In micro-injection molding, it is important to make each cavity filled uniformly. However, there are several factors that cause deviation in cavity filling. These factors include the mold temperature differential between runners and the diameter differential of gates or runners caused by mold manufacturing tolerances. In this study, we conducted numerical analysis to identify the major factors that cause cavity filling deviation and suggest a considerably robust design for microinjection mold to minimize the deviation. In the numerical simulation, we used thermophysical property values of EP-7000, one of the polycarbonate series polymers used for injection molding. The Cross-Arrhenius model was adopted with regard to the viscosity of the polymer. To model the specific heat and the thermal conductivity, we used the piecewise-linear method. Further, the volume of fluid method and the piecewise-linear interface scheme were used to visualize the polymer flow. Sixteen-cavity injection mold was modeled, and simulations were done for four different variations (the mold temperature, the runner diameter, the gate thickness, and a combination of the mold temperature and the runner diameter). Numerical analysis indicated that the case of mold temperature exhibited a difference of up to 28 % in instant cavity filling rate and the case of combination showed a difference of up to 33 %. We suggested designs employing convergent runner and resin reservoir to reduce deviation. As a result, the convergent runner design could reduce the instant cavity filling rate deviation by 20 %, while the resin reservoir design reduced the deviation by 18 %. The combination of these two could reduce the deviation by up to 22 %.

Effect of runner design on the externally solidified crystals in vacuum die-cast Mg-3.0Nd-0.3Zn-0.6Zr alloy

The microstructure and tensile properties of a vacuum-assist high-pressure die casting (HPDC) Mg-3.0Nd-0.3Zn-0.6 Zr alloy and the effect of runner design on the externally solidified crystals (ESCs) were investigated. The microstructure of the alloy mainly comprised ESCs (large primary α-Mg grains) formed in the chamber, small primary α-Mg grains crystalized in the cavity, divorced eutectic Mg12Nd and a small amount of Mg12(NdxZn1-x) or Mg12(NdxZnyZr1-x-y) phases in the region near the shrinkage. The average ESCs grain size decreased as the distance from the center increased remarkably. The employment of ESCs collector contributed to the depression of ESCs grain size, particularly in center region. On the contrary, the grain size of small primary α-Mg has overall slightly downward trend from center to skin region, and the size difference was small. The employment of an ESCs collector effectively decreased the number and size of the ESCs, and accordingly both strength and elongation of the alloy were improved. This specially design ESCs collector improve the runner system and optimize the mold design. The elongation of the alloy approached 10%.

Do not be Afraid of Small High-Speed Francis Turbines

Abstract In the first quarter of the last century hydraulic power plants were equipped with high-speed Francis turbines even in the situation when a contemporary project manager would suggest Kaplan turbine. The reason is simple. Mr. Kaplan patented his turbine only in 1912 [1], https://en.wikipedia.org/wiki/Viktor_Kaplan . Those high-speed Francis turbines have just reached their lifetime. Mainly runners need repair. Our customers’ respond is that even renowned firms refuse to deliver runners with better parameters. Offer is to replace whole turbine with Kaplan or to make a copy of the existing runner. This paper presents experience and results of such a high-speed runner design. The runner substituted the one of Prokopa &amp; sons from 1939 in powerhouse and mill at Křemže stream. Virtual prototyping technique has been used.

Design and Analysis of an Operative Inlet

This paper describes the effect of intake manifold with the application of intake runner as the operative inlet used in racing car that participate in Formula Student (FSAE) competition. The design analysis of the runner is carried out to give uniform distribution of the air flow getting into engine. Air flow behavior plays an important role in order to provide better air fuel mixture inside the intake manifold before it is drawn to the combustion chamber. The results from this study indicate that longer runner gives low percentage of pressure loss but cause the air velocity to drop. Changing the outlet diameter of runner gives higher velocity at the smaller diameter and highest angle resulted higher air mass flow rate inside the runner. The new design of runner is built of 60mm length, 55mm outlet diameter and 55° angle and the results show 0.05% improvement occur in air flow distribution at the end of each runner outlet.