Evolution of Vortex At The Runner Area of Pump-Turbine Under The Runaway Condition

Abstract To study the evolution principle of the coherent structure in the low flow rate runaway condition, the pump-turbine of the certain pumped storage power plant is employed. The transient dynamic stress of the runner has been numerically simulated and examined in this study, in order that can probe the mechanism of channel vortices acting on the blade and the evolution of their coherent structure in the runner. Based on the Realizable k-ε turbulent model, the unsteady flow of the whole pump-turbine channels is calculated. Results show that the flow in the runner channels presents with the turbulence state, and with many different scales vortices. These vortices structures are mainly distributed in the inlet region of the blade, the area of the blade trailing edge and the middle section of the runner channels. These vortex structures affect the distribution of the blade pressure load. Moreover, vortices structure at the inlet of the runner depends on the change of the attack angle. In the flow region formed at the outlet of the blade near the suction surface and the runner cone, the blade has a limited effect to the fluid, thus the vortex structure depends on the Coriolis force and the centrifugal force joint action.

Download Full-text

Simulation of Flow in Turbopump Vaneless and Vaned Diffusers with Fluid Injection

International Journal of Rotating Machinery ◽

10.1155/s1023621x00000063 ◽

2000 ◽

Vol 6 (1) ◽

pp. 57-65

Author(s):

Ali Ogut ◽

Diego Garcia Pastor

Keyword(s):

Flow Separation ◽

Flow Region ◽

Design Flow ◽

Low Flow ◽

Fluid Injection ◽

Bottom Surface ◽

Suction Surface ◽

Vaned Diffuser ◽

Flow Rates ◽

Wide Range

In future space missions by NASA there will be a need for “Space Transfer Vehicles” to perform varying orbital transfers and descents. This requires engines capable of producing different levels of thrust. To accomplish this, the turbopumps employed in these engines should efficiently provide a wide range of flow outputs. However, current fuel and oxidizer turbopumps with vaned diffusers do not perform efficiently at off-design (low) flow rates mainly due to flow separation in the vaned diffuser.This paper evaluates the effectiveness of boundary layer control by fluid injection (blowing) for suppressing or eliminating the flow separation in a vaned diffuser. A 3-D flow model including vaneless and vaned diffusers of a liquid hydrogen (LH2) turbopump is studied using the CFD code FIDAP. The paper presents the results of the model at design and offdesign flow conditions.The model results showed that flow separation occurs at the top or suction surface of the vaneless diffuser and at the bottom or pressure surface of the vaned diffuser at off-design flow rates. When fluid injection was applied through the bottom surface of the vaned diffuser, the separated flow region was reduced almost entirely, resulting in an increase in pressure recovery of up to 21% with varying fluid injection rates. Results also showed that there is an optimum injection rate which is most effective in reducing or eliminating the region of flow separation.

Download Full-text

A Meanline Model for Impeller Flow Recirculation

Volume 6: Turbomachinery, Parts A, B, and C ◽

10.1115/gt2008-51349 ◽

2008 ◽

Cited By ~ 10

Author(s):

Xuwen Qiu ◽

David Japikse ◽

Mark Anderson

Keyword(s):

Flow Rate ◽

Recirculation Zone ◽

Reverse Flow ◽

Low Flow ◽

Suction Surface ◽

Blade Loading ◽

Flow Recirculation ◽

Impeller Outlet ◽

Active Flow ◽

Low Flow Rate

Flow recirculation at the impeller inlet and outlet is an important feature that affects impeller performance, especially the power consumption at a very low flow rate. Although the mechanisms for this flow phenomenon have been studied, a practical model is needed for meanline modeling of impeller off-design performance. In this paper, a meanline recirculation model is proposed. At the inlet, the recirculation zone acts as area blockage to relieve the large incidence of the active flow at a low flow rate. The size of the blockage is estimated through a critical area ratio of an artificial “inlet diffuser” from the inlet to throat. The intensity of the reverse flow can then be calculated by assuming a linear velocity profile of meridional velocity in the recirculation zone. At the impeller outlet, a recirculation zone near the suction surface is established to balance the velocity difference on the pressure and suction sides of the blade. The size and the intensity of the outlet recirculation zone is assumed related to blade loading, which can be evaluated based on flow turning and Coriolis force. A few validation cases are presented showing a good comparison between test data and prediction by the model.

Download Full-text

Pressure Analysis in the Draft Tube of a Pump-Turbine under Steady and Transient Conditions

Energies ◽

10.3390/en14164732 ◽

2021 ◽

Vol 14 (16) ◽

pp. 4732

Author(s):

Jing Yang ◽

Yue Lv ◽

Dianhai Liu ◽

Zhengwei Wang

Keyword(s):

Steady State ◽

Pressure Pulsation ◽

Transient Flow ◽

Draft Tube ◽

Simulation Method ◽

Wall Pressure ◽

Pump Turbine ◽

Steady State Condition ◽

Transient Conditions ◽

Pumped Storage

Pumped-storage power stations play a regulatory role in the power grid through frequent transition processes. The pressure pulsation in the draft tube of the pump-turbine under transient processes is important for safe operation, which is more intense than that in the steady-state condition. However, there is no effective method to obtain the exact pressure in the draft tube in the transient flow field. In this paper, the pressure in the draft tube of a pump-turbine under steady-state and transient conditions are studied by means of CFD. The reliability of the simulation method is verified by comparing the real pressure pulsation data with the test results. Due to the distribution of the pressure pulsation in the draft tube being complex and uneven, the location of the pressure monitoring points directly affects the accurate judgement of cavitation. Eight monitoring surfaces were set in the straight cone of the draft tube and nine monitoring points were set on each monitoring surface to analyze the pressure differences on the wall and inside the center of the draft tube. The relationships between the pressure pulsation value inside the center of the draft tube and on the wall are studied. The “critical” wall pressure pulsation value when cavitation occurs is obtained. This study provides references for judging cavitation occurrences by using the wall pressure pulsation value in practical engineering.

Download Full-text

Experiences on Startup and Trial Operation at Yards Creek Pumped Storage Project

Journal of Basic Engineering ◽

10.1115/1.3571131 ◽

1969 ◽

Vol 91 (3) ◽

pp. 387-395 ◽

Cited By ~ 1

Author(s):

R. J. Swed ◽

K. H. Yang

Keyword(s):

Pump Turbine ◽

Exchange Of Information ◽

Pumped Storage

Many problems were encountered during the startup and trial operation at Yards Creek. This paper describes the major problems and how they were resolved. There are many questions about pump-turbine operation that remain unanswered. Exchange of information and experience is needed. The authors hope that this article will help to stimulate this exchange of information.

Download Full-text

Passive Control of Unstable Characteristics of a High Specific Speed Diagonal-Flow Fan by an Annular Wing

Volume 1: Turbomachinery ◽

10.1115/90-gt-159 ◽

1990 ◽

Cited By ~ 1

Author(s):

Kenji Kaneko ◽

Toshiaki Setoguchi ◽

Masahiro Inoue

Keyword(s):

Flow Rate ◽

Geometrical Parameter ◽

Energy Input ◽

Passive Control ◽

Internal Flow ◽

Flow Region ◽

Low Flow ◽

Performance Tests ◽

Flow Measurements ◽

Specific Speed

A passive control of an unstable characteristics of a high specific speed diagonal-flow fan has been proposed. It is possible to eliminate the unstable characteristics of pressure-flow rate curve in a low flow region without deterioration of performance at design point. The control action is done naturally (passively) without any energy input. The inlet nozzle of an ordinary diagonal-flow fan was replaced by an annular wing with Göttingen 625 airfoil section. The mechanism of the passive control and the optimum geometrical parameter are discussed on the basis of the performance tests and internal flow measurements.

Download Full-text

Modelling and Reducing Fuel Flow Pulsation of a Fuel-Metering System by Improving Response of the Pressure Control Valve During Pump Mode Switching in a Turbofan Engine

ASME/BATH 2019 Symposium on Fluid Power and Motion Control ◽

10.1115/fpmc2019-1604 ◽

2019 ◽

Author(s):

Seiei Masuda ◽

Fumio Shimizu ◽

Masaki Fuchiwaki ◽

Kazuhiro Tanaka

Keyword(s):

Control Valve ◽

Flow Region ◽

Pressure Control ◽

Low Flow ◽

Mode Switching ◽

Pump Mode ◽

Turbofan Engine ◽

Fuel Pump ◽

Fuel Flow ◽

Pressure Control Valve

Abstract In an aircraft turbofan engine, a fuel metering unit meters and supplies the required fuel to the engine according to the flight situation. When a centrifugal fuel pump (CFP) is used as the fuel pump, the ratio of hydraulic power per weight can be increased by raising the rated rotational speed, so the weight of the fuel pump can be decreased compared to when using a gear pump (GFP). There is an advantage that it can be reduced significantly. However, since the operating range of the fuel pump is wide, it is not effective to use CFP in an extremely low flow rate region because the fuel temperature rises due to its PQ characteristics and a large loss. Therefore, it is considered effective to combine CFP and GFP as pressure sources, and to use GFP in the low flow region and CFP in the high flow region. For that purpose, it is necessary to have a pump mode switching mechanism. The disadvantage in this case is that changing the pump mode causes a large pressure change of the fuel pressure source, which in turn causes fuel flow pulsations. There are three possible ways to solve this problem. The first method is to keep the differential pressure control valve (DPCV) unit response constant, which keeps the metering valve differential pressure constant in FMS. A second method is to remove high frequency components that the DPCV cannot follow pressure changes in the fuel control system. A third method is to keep the pressure difference between the two fuel sources small and to reduce the amplitude of the applied disturbance. In this paper, the first method, which makes DPCV response high response, is verified by modeling and simulation, and its effectiveness is confirmed.

Download Full-text

Inter-Blade Vortex and Vortex Rope Characteristics of a Pump-Turbine in Turbine Mode under Low Flow Rate Conditions

Water ◽

10.3390/w11122554 ◽

2019 ◽

Vol 11 (12) ◽

pp. 2554 ◽

Cited By ~ 1

Author(s):

Seung-Jun Kim ◽

Jun-Won Suh ◽

Young-Seok Choi ◽

Jungwan Park ◽

No-Hyun Park ◽

...

Keyword(s):

Flow Rate ◽

Stokes Equations ◽

Low Flow ◽

Renewable Energy Resources ◽

Two Phase ◽

Constant Frequency ◽

Pump Turbine ◽

Vortex Rope ◽

Turbine Mode ◽

Low Flow Rate

Pump-turbines are often used to provide a stable power supply with a constant frequency in response to intermittent renewable energy resources. However, existing pumped-storage power stations often operate under off-design conditions because of the increasing amounts of inconsistent renewable resources that have been added to the grid. Under off-design low flow rate conditions, inter-blade vortex and vortex rope phenomena usually develop in the runner and draft tube passages, respectively, in turbine mode. These vortices cause complicated flow patterns and pressure fluctuations that destabilize the operation of the pump-turbine system. Therefore, this study investigates the influence of correlation between the inter-blade vortex and vortex rope phenomena under low flow rate conditions. Three-dimensional steady- and unsteady-state Reynolds-averaged Navier–Stokes equations were calculated with a two-phase flow analysis using a shear stress transport as the turbulence model. The inter-blade vortices in the runner passages were captured well at the low flow rate conditions, and the vortex rope was found to develop within a specific range of low flow rates. These vortex regions showed a blockage effect and complicated flow characteristics with backflow in the passages. Moreover, higher unsteady pressure characteristics occurred at locations where the vortices were especially pronounced.

Download Full-text

No-Load Stability Analysis of Pump Turbine at Startup-Grid Integration Process

Journal of Fluids Engineering ◽

10.1115/1.4043057 ◽

2019 ◽

Vol 141 (8) ◽

Cited By ~ 1

Author(s):

Ziwen Zhao ◽

Hao Zhang ◽

Diyi Chen ◽

Xiang Gao

Keyword(s):

Stability Analysis ◽

Theoretical Basis ◽

Grid Integration ◽

Integration Process ◽

Pump Turbine ◽

Plant Model ◽

Disturbance Intensity ◽

Pumped Storage ◽

Load Stability ◽

Step Disturbance

This paper focuses on no-load stability during startup-grid integration process. First, no-load operating dynamic character under startup-grid integration process is studied by bifurcation diagram, based on a classical pumped storage plant model. Second, the no-load stability of pump turbine was analyzed by introducing step disturbance and slopes. Finally, the results indicate that the no-load operating point is easy to be disturbed and some factors, such as different disturbance intensity and slopes, have different influence on no-load stability. These methods and results will supply theoretical basis for operating the pumped storage plant steadily.

Download Full-text