scholarly journals Hysteresis Characteristic in Hump Region of a Pump-Turbine Model

2016 ◽  
Author(s):  
Deyou Li ◽  
Hongjie Wang ◽  
Jinxia Chen ◽  
Torbjørn K. Nielsen ◽  
Daqing Qin ◽  
...  
Keyword(s):  
Guide Vane ◽  
Pressure Sensors ◽  
Low Frequency ◽  
Rotational Frequency ◽  
Hysteresis Phenomenon ◽  
Pump Turbine ◽  
Hysteresis Characteristic ◽  
Hydraulic Losses ◽  
Measurement Direction ◽  
Turbine Model

The hump characteristic is one of the major instabilities in pump-turbines. When pump-turbines operate in the hump region, strong noise and serious fluctuations could be observed, which are harmful to the safe and stable operations and even destroy the whole unit as well as water conveyance system. In this paper, a low specific speed (nq = 36.1 min−1) pump-turbine model was experimentally investigated. Firstly, the hump characteristic was obtained under 19 mm guide vane opening. More interestingly, when the hump characteristic was measured in two directions (increasing and decreasing the discharge), the hysteresis characteristic was found during the hump region. The analysis of performance characteristics reveals that the hump instability is resultant of Euler momentum and hydraulic losses, and different Euler momentum and hydraulic losses in the two development processes lead to hysteresis phenomenon. Then, 12 pressure sensors were mounted in the different parts of the pump-turbine model to obtain the time and frequency characteristics. The analysis of fast Fourier transform confirms that the hump characteristic is related to the low-frequency (0.04–0.15 times rotational frequency) vortices. The occurrence and cease of vortices depend on the operating condition and measurement direction, which contribute to the hysteresis characteristic. Finally, the type of the low-frequency vortices was analyzed through the cross power spectrum.

scholarly journals Hysteresis Characteristic in the Hump Region of a Pump-Turbine Model

2016 ◽  
Author(s):  
Deyou Li ◽  
Hongjie Wang ◽  
Jinxia Chen ◽  
Torbjørn K. Nielsen ◽  
Daqing Qin ◽  
...  
Keyword(s):  
Guide Vane ◽  
Pressure Sensors ◽  
Low Frequency ◽  
Rotational Frequency ◽  
Stable Operation ◽  
Hysteresis Phenomenon ◽  
Pump Turbine ◽  
Hydraulic Losses ◽  
Measurement Direction ◽  
Turbine Model

The hump feature is one of the major instabilities in pump-turbines. When pump-turbines operate in the hump region, strong noise and serious fluctuations can be observed, which are harmful to their safe and stable operation and can even destroy the whole unit as well as water conveyance system. In this paper, a low specific speed (nq = 36.1 min−1) pump-turbine model was experimentally investigated. Firstly, the hump characteristic was obtained under 19 mm guide vane opening conditions. More interestingly, when the hump characteristic was measured in two directions (increasing and decreasing the discharge), characteristic hysteresis was found in the hump region. The analysis of performance characteristics reveals that the hump instability is the result of Euler momentum and hydraulic losses, and different Euler momentum and hydraulic losses in the two development processes lead to the hysteresis phenomenon. Then, 12 pressure sensors were mounted in the different parts of the pump-turbine model to obtain the time and frequency characteristics. The analysis of the corresponding fast Fourier transform confirms that the hump characteristic is related to low-frequency (0.04–0.15 times rotational frequency) vortices. The occurrence and cessation of vortices depend on the operating condition and measurement direction, which contribute to the hysteresis feature. Finally, the type of the low-frequency vortices was analyzed through the cross power spectrum.

scholarly journals Simulation and Experimental Investigation of the Stay Vane Channel Flow in a Reversible Pump Turbine at Off-Design Conditions

2017 ◽  
Vol 61 (2) ◽  
pp. 94 ◽  
Author(s):  
Sandro Erne ◽  
Gernot Edinger ◽  
Anton Maly ◽  
Christian Bauer
Keyword(s):  
Transient Flow ◽  
Guide Vane ◽  
Low Frequency ◽  
Rotating Stall ◽  
Design Flow ◽  
Flow State ◽  
Mean Flow ◽  
Load Range ◽  
Pump Turbine ◽  
Stall Inception

This work presents the assessment of the mean flow field and low frequency disturbances in the stay vane channel of a model pump turbine using transient numerical simulations and LDV-based measurements. The focus is laid on transient CFD simulations of characteristic flow states in the stay vane channel when operating at off-design conditions in pump mode. Experimental and numerical investigations obtained a shifting velocity distribution between the shroud and hub of the distributor when continuously increasing the discharge in the part-load range. Simulations captured the occurrence of this changing flow state in the stay vane channel reasonably well. A further increase of the discharge showed a uniformly redistributed mean flow of both hub and shroud side. Monitoring points and integral quantities from measurements and transient simulations were used to interpret the development of transient flow patterns in the stay vane channel at the operating point of strongest asymmetrical flow. During simulation and measurement, a dominant rotating stall inception was observed near the design flow of the pump turbine. At this point where the stall becomes severe, a high level of correlation between the signals of the upper and lower stalled flow in the stay vane channel was calculated. Further simulations for different guide vane positions predicted a strong influence of the guide vane position on the structure of rotating stall.

scholarly journals Hysteresis Characteristic in the Hump Region of a Pump-Turbine Model

Energies ◽  
2016 ◽  
Vol 9 (8) ◽  
pp. 620 ◽  
Author(s):  
Deyou Li ◽  
Hongjie Wang ◽  
Jinxia Chen ◽  
Torbjørn Nielsen ◽  
Daqing Qin ◽  
...  
Keyword(s):  
Pump Turbine ◽  
Hysteresis Characteristic ◽  
Turbine Model

Experimental Investigations of the Onset of Rotating Stall

2008 ◽  
Author(s):  
P. B. V. Johansson ◽  
M. Henriksson
Keyword(s):  
Time Domain ◽  
Pressure Sensors ◽  
Low Frequency ◽  
Pressure Profile ◽  
Rotational Frequency ◽  
Rotating Stall ◽  
Test Facility ◽  
Experimental Investigations ◽  
Measurement Signal ◽  
Low Pass

This work focuses on analysis of data obtained in experimental investigations of a military fan in a whole-engine test facility. The data was simultaneously obtained by using multiple pressure sensors located at different axial and angular positions in the fan. In particular, the origin of rotating stall was investigated by analyzing the experimental data both in the frequency-time domain as well as the correlation in time between the typical pressure profile and the pressure profile for each revolution of the rotor. First, the measurement signal was high-pass filtered with a cut-off frequency slightly lower than the spool rotational frequency. These high frequency data were subjected to a typical pressure distribution test. Second, the measurement signal was low-pass filtered slightly lower than the spool rotational frequency. The low frequency part was investigated in the frequency-time domain. A quantitative measurement of an indicator of rotating stall is presented and its limitation for practical use is discussed.

scholarly journals On the Rotor Stator Interaction Effects of Low Specific Speed Francis Turbines

2019 ◽  
Vol 2019 ◽  
pp. 1-11 ◽  
Author(s):  
Einar Agnalt ◽  
Igor Iliev ◽  
Bjørn W. Solemslie ◽  
Ole G. Dahlhaug
Keyword(s):  
Guide Vane ◽  
Pressure Fluctuations ◽  
Angular Position ◽  
Pressure Sensors ◽  
Pump Turbine ◽  
Blade Loading ◽  
Loading Case ◽  
Rotor Stator Interaction ◽  
Low Specific Speed ◽  
Specific Speed

The rotor stator interaction in a low specific speed Francis model turbine and a pump-turbine is analyzed utilizing pressure sensors in the vaneless space and in the guide vane cascade. The measurements are analyzed relative to the runner angular position by utilizing an absolute encoder mounted on the shaft end. From the literature, the pressure in the analyzed area is known to be a combination of two effects: the rotating runner pressure and the throttling of the guide vane channels. The measured pressure is fitted to a mathematical pressure model to separate the two effects for two different runners. One turbine with 15+15 splitter blades and full-length blades and one pump-turbine with six blades are investigated. The blade loading on the two runners is different, giving different input for the pressure model. The main findings show that the pressure fluctuations in the guide vane cascade are mainly controlled by throttling for the low blade loading case and the rotating runner pressure for the higher blade loading case.

Transient Pressure Pulsations of a Model Pump-Turbine During Power Failure

2017 ◽  
Author(s):  
Jinhong Hu ◽  
Wei Zeng ◽  
Jiandong Yang ◽  
Renbo Tang
Keyword(s):  
Rotational Speed ◽  
Guide Vane ◽  
Dynamic Pressure ◽  
Pressure Sensors ◽  
Open Loop ◽  
Operating Conditions ◽  
Pressure Pulsations ◽  
Transient Pressure ◽  
Pump Turbine ◽  
Power Failure

Pump-turbine can operate in either pump mode or turbine mode. The quick response to load changes as well as the ability to store energy makes it essential to the stability of power grid. When a pump-turbine works in different condition, flow-induced instabilities occur, including Rotor Stator Interaction (RSI) between the runner and vanes, vortex formations and back flow regions. To understand these complicated flow dynamics, experimental and numerical investigations have been conducted by many researchers. Among these researches, many experiments on model test rigs are mainly focused on steady state, and knowledge for instabilities during transients is still lacking. In this paper, power failure experiments with constant guide van opening are conducted on an open-loop test rig. During the process, the operating point of the pump-turbine in the 4 quadrant characteristics moves from pump region through the brake region, turbine region to turbine brake region. Finally the pump-turbine settled down at runaway rotational speed. In our experiments, flow rate, rotational speed, torque, pressure in the spiral casing and the draft tube inlet are measured. Especially, dynamic pressure sensors mounted in the guide vane channels are used to measure transient pressure pulsations. Measured data are analyzed in both time domain and frequency domain. Results indicate that during power failure pressure pulsations in the vane channels vary significantly with the operating conditions. In the pump region, pressure pulsations are mainly composed of RSI. In the brake region, intensive stochastic noises occur, and the amplitude of RSI rises. In the turbine region, the magnitude of pressure pulsations drops sharply as the noise intensity goes down. In the turbine brake region, significant noises appear, and the amplitude of RSI increases dramatically.

Entropy production analysis of hysteresis characteristic of a pump-turbine model

2017 ◽  
Vol 149 ◽  
pp. 175-191 ◽  
Author(s):  
Deyou Li ◽  
Hongjie Wang ◽  
Yonglin Qin ◽  
Lei Han ◽  
Xianzhu Wei ◽  
...  
Keyword(s):  
Entropy Production ◽  
Pump Turbine ◽  
Hysteresis Characteristic ◽  
Production Analysis ◽  
Turbine Model

Numerical simulation of hysteresis characteristic in the hump region of a pump-turbine model

2018 ◽  
Vol 115 ◽  
pp. 433-447 ◽  
Author(s):  
Deyou Li ◽  
Hongjie Wang ◽  
Yonglin Qin ◽  
Xianzhu Wei ◽  
Daqing Qin
Keyword(s):  
Numerical Simulation ◽  
Pump Turbine ◽  
Hysteresis Characteristic ◽  
Turbine Model

Impact of guide vane opening angle on the flow stability in a pump-turbine in pump mode

2016 ◽  
Vol 231 (13) ◽  
pp. 2484-2492 ◽  
Author(s):  
Di Zhu ◽  
Ruofu Xiao ◽  
Ran Tao ◽  
Weichao Liu
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Flow Regime ◽  
Flow Rate ◽  
Guide Vane ◽  
Low Flow ◽  
Opening Angle ◽  
Pump Mode ◽  
Pump Turbine ◽  
Hydraulic Losses

In the pump mode (storage mode) of a pump-turbine, unstable head variations occur as the flow rate decreases, leading to unstable, unsafe operation. Thus, the hydrodynamics of pump-turbines in the unstable operating range should be investigated to improve their designs. This study presents experimental and numerical studies of the hydrodynamics. The experiments investigated the external characteristics with the head instabilities captured by both the model tests and the computational fluid dynamics simulations. The computational fluid dynamics model used detached eddy simulations to study the flow details which showed that hydraulic losses were the reason for the unstable head variations and the poor flow regime was the source of the losses. In the unstable, low flow rate range, the flow direction is no longer consistent with the guide vane direction, so undesirable flow structures develop in the passages. Therefore, appropriate guide vane opening angles are needed to improve the flow regime and reduce the hydraulic losses. These will enhance the operating stability and safety in engineering applications.

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