Stability Limits of Reversible-Pump Turbines in Turbine Mode of Operation and Measurements of Unstable Characteristics

2012 ◽  
Vol 134 (11) ◽  
Author(s):  
Grunde Olimstad ◽  
Torbjørn Nielsen ◽  
Bjarne Børresen
Keyword(s):  
Stability Criterion ◽  
Input Parameter ◽  
Static Stability ◽  
Pump Turbine ◽  
Water Column Stability ◽  
Pressure Dependency ◽  
Previous State ◽  
Input Variables ◽  
Unstable Part ◽  
Turbine Mode

Measurements have been performed on a reversible-pump turbine model installed in a closed loop conduit system. The characteristics of the unstable pump turbine in turbine mode show a hysteresis pattern. Hence the output of the system is dependent on the previous state of the flow and not only the input variables. The hysteresis pattern is a characteristic of the whole system, but is caused by the unstable pump turbine. The unstable part of the characteristics was measured by three different methods: 1) by transient sampling of data during the transition between operation modes, 2) by throttling valves that steepens the friction-loss curve, and 3) by switching the causality in the system such that the torque becomes an input parameter and the speed of rotation becomes an output parameter. In the valve throttling measurements a pressure dependency was seen for the characteristics at high nondimensional speeds. This was further investigated by additional measurements of the characteristics at three different pressure levels. A rigid-water-column stability analysis has been conducted. The classic H-Q criterion describes static stability for a pump turbine with constant speed of rotation. With the speed of rotation as a variable, there is a new static stability criterion in addition to the dynamic stability criterion.

scholarly journals Turbine mode start-up simulation of a variable speed Francis pump-turbine prototype – Part II: 3-D unsteady CFD and FEM

2021 ◽  
Vol 774 (1) ◽  
pp. 012070
Author(s):  
D. Biner ◽  
S. Alligné ◽  
V. Hasmatuchi ◽  
C. Nicolet ◽  
N. Hugo ◽  
...  
Keyword(s):  
Variable Speed ◽  
Pump Turbine ◽  
Start Up ◽  
Turbine Mode

scholarly journals Multiobjective Optimization of a Counterrotating Type Pump-Turbine Unit Operated at Turbine Mode

2014 ◽  
Vol 6 ◽  
pp. 467235 ◽  
Author(s):  
Jin-Hyuk Kim ◽  
Risa Kasahara ◽  
Toshiaki Kanemoto ◽  
Toru Miyaji ◽  
Young-Seok Choi ◽  
...  
Keyword(s):  
Multiobjective Optimization ◽  
Turbine Unit ◽  
Pump Turbine ◽  
Turbine Mode

Walking Stability Analysis of Multi-Legged Crablike Robot over Slope

2013 ◽  
Vol 572 ◽  
pp. 636-639
Author(s):  
Xi Chen ◽  
Gang Wang
Keyword(s):  
Mathematical Model ◽  
Stability Analysis ◽  
Stability Criterion ◽  
Stability Margin ◽  
Static Stability ◽  
Matlab Simulation ◽  
And Performance ◽  
The Stability ◽  
The Mathematical Model ◽  
The Relationship

This paper deals with the walking stability analysis of a multi-legged crablike robot over slope using normalized energy stability margin (NESM) method in order to develop a common stabilization description method and achieve robust locomotion for the robot over rough terrains. The robot is simplified with its static stability being described by NESM. The mathematical model of static stability margin is built so as to carry out the simulation of walking stability over slope for the crablike robot that walks in double tetrapod gait. As a consequence, the relationship between stability margin and the height of the robots centroid, as well as its inclination relative to the ground is calculated by the stability criterion. The success and performance of the stability criterion proposed is verified through MATLAB simulation and real-world experiments using multi-legged crablike robot.

A boundary vorticity diagnosis of the flows in a model pump-turbine in turbine mode

2020 ◽  
Vol 153 ◽  
pp. 1465-1478
Author(s):  
Guocheng Lu ◽  
Deyou Li ◽  
Zhigang Zuo ◽  
Shuhong Liu ◽  
Hongjie Wang
Keyword(s):  
Pump Turbine ◽  
Turbine Mode

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

Water ◽  
2019 ◽  
Vol 11 (12) ◽  
pp. 2554 ◽  
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.

Uplift and Mantle Thickness: A Sensitivity Study

2007 ◽  
Vol 25 (4) ◽  
pp. 273-299
Author(s):  
I. Lerche ◽  
K. Reicherter
Keyword(s):  
Heat Flux ◽  
Input Parameter ◽  
Sensitivity Study ◽  
Surface Heat ◽  
Water Density ◽  
Relative Contribution ◽  
Input Variables ◽  
Crustal Density ◽  
Parameter Values ◽  
Mantle Thickness

This paper derives an inverse set of equations for equilibrium situations to discuss the resolution and sensitivity of models used to describe tectonic uplift and thermal heat flux. The sensitivity of results to variations in single parameters away from a described set of canonical values is given first. This sensitivity study is followed by a detailed treatment describing the probabilities of obtaining mantle thickness, surface heat flux, thermal expansion coefficient, base crustal heat flux, and Moho temperature at or above particular values as the water density, crustal density, asthenospheric density, uplift, crustal thickness, average lithospheric density, base lithospheric temperature, and water depth to the free asthenosphere marker are all allowed to vary simultaneously around their canonical values. In addition, a relative contribution plot for each of the five output variables identifies which of the eight input variables is causing the greatest contribution to the uncertainty. In this way one can identify which variables need to have their ranges of uncertainty narrowed in order to be more precise about the chances of obtaining particular values for the five outputs. A skewness estimate also is given that enables one to determine the most likely directions one should expect improvement to occur with a probability plot of obtaining particular values, or higher, for each of the output variables. Numerical illustrations show how one goes about performing the quantitative assessments and also show how the inverse procedure allows one to be more definitive concerning the five output values, and their ranges of uncertainty, because of uncertainties in the eight input parameter values.

Influences of wear-ring clearance leakage on performance of a small-scale pump-turbine

2019 ◽  
Vol 234 (4) ◽  
pp. 454-469 ◽  
Author(s):  
Jianru Yan ◽  
Zhitao Zuo ◽  
Wenbin Guo ◽  
Hucan Hou ◽  
Xin Zhou ◽  
...  
Keyword(s):  
Flow Rate ◽  
Total Pressure ◽  
Labyrinth Seal ◽  
Work Capacity ◽  
Small Scale ◽  
Leakage Flow ◽  
Pump Mode ◽  
Pump Turbine ◽  
Flow Angle ◽  
Turbine Mode

Wear-ring clearance leakage would affect performance of pump-turbine significantly. In this paper, the variation of the leakage and efficiency of flat ring seal and labyrinth seal are numerically studied on one pump-turbine when the width of clearance is 0.2 mm and 0.5 mm. The result shows that the effect of leakage flow cannot be neglected. The pump-turbine performance affected by leakage in turbine mode is more than that in pump mode at the same sealing structure and width of clearance. Each component’s proportion of total pressure loss hardly varies with flow rate at pump mode, which is opposite to that at turbine mode. Leakage does not change proportionally with system flow rate. When the width of clearance decreases to 0.2 mm, the leakage is reduced obviously because the maximum entropy occurs in the front pump chamber. The mixing of leakage flow and mainstream at impeller inlet at pump mode will increase the total pressure and decrease the flow angle and relative flow angle. Finally, it reduces the impeller’s work capacity.

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