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

Energies ◽  
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.

The Transient Response of Orifices and Very Short Lines

1972 ◽  
Vol 94 (2) ◽  
pp. 483-489 ◽  
Author(s):  
J. E. Funk ◽  
D. J. Wood ◽  
S. P. Chao
Keyword(s):  
Steady State ◽  
Pressure Drop ◽  
System Analysis ◽  
Transient Flow ◽  
Transient Behavior ◽  
Short Term ◽  
State Equations ◽  
Steady State Condition ◽  
Orifice Flow ◽  
Flow Through

It is generally assumed that orifices and valves follow closely their steady-state characteristics during transient operation. However, this assumption of quasisteady behavior may lead to errors in predicting transient flow conditions under certain circumstances. In order to evaluate the transient behavior of an orifice, a differential equation relating the flow through and the pressure drop across an orifice was derived. An extension was made to include an axial dimension for the orifice. The solution of this equation for transient flow through an orifice subjected to a step change in pressure drop across the orifice is significantly different than that obtained using the steady state relationship. An experiment was designed to evaluate the theoretical results in which an orifice on the end of a line was subjected to a sudden pressure change and the resulting transient pressures were observed. It was found that a significant short term transient occurs before the orifice flow reaches the new steady state condition. The observed short term transient agrees well with that predicted by the theory. It is concluded that the behavior of an orifice can deviate considerably from that predicted by steady-state equations during periods of rapid pressure or flow changes. The dynamic description of orifice flow may be combined with a larger system analysis (e.g., using the method of characteristics) to more accurately predict the overall transient performance of flow systems.

Modeling TBM Components by Using RELAP5 Code

2013 ◽  
Author(s):  
Yaoli Zhang ◽  
Tianji Peng
Keyword(s):  
Steady State ◽  
Light Water Reactor ◽  
Component Level ◽  
Flow Paths ◽  
Steady State Condition ◽  
Transient Conditions ◽  
Hydraulic Behavior ◽  
Neutron Multiplier ◽  
Estimate System ◽  
Relap5 Code

RELAP5 is a best estimate system code suitable for the analysis of all transients and postulated accidents in Light Water Reactor systems. It was usually used to solve plant thermal-hydraulic problems on system scale. RELAP5 was used to study thermal-hydraulic behavior on component level in this paper. The Test Blanket Module (TBM) was a key component in Chinese Helium-Cooled Solid Breeder (CN HCSB) system. One sub-module of TBM was simulated by RELAP5/MOD3.4. The flow paths, Be pebbles neutron multiplier as well as Li4SiO4 pebbles tritium breeder of TBM were modeled by using hydrodynamic components models as well as heat structure models provided by RELAP5. Steady-state condition was studied and the results were compared with CFD results provided by Fluent code. The steady-state results were in consistent with CFD results when the sub-module was well modeled by RELAP5. The results showed that RELAP5 could be used to solve thermal-hydraulic problems on component scale when the component was well modeled. With a detail-modeled TBM, the transient conditions of CN HCSB system could be simulated more precisely by RELAP5.

Study on the Hydraulic Transients of Pump-Turbines Load Successive Rejection in Pumped Storage Plant

2007 ◽  
Author(s):  
Jian Zhang ◽  
Weihua Lu ◽  
Jianyong Hu ◽  
Boqin Fan
Keyword(s):  
Draft Tube ◽  
Maximum Pressure ◽  
Hydraulic Transients ◽  
Pump Turbine ◽  
Hydraulic Unit ◽  
Interval Time ◽  
Minimum Pressure ◽  
Practical Operation ◽  
Water Conveyance ◽  
Pumped Storage

During the calculation of hydraulic transients in pumped storage plants, the speed change of reversible pump-turbine has great relation with the pressure of water conveyance system, and results in the minimum pressure at draft tube does not occur while all sets in the same hydraulic unit reject load simultaneously, but occurs in the combined conditions of load successive rejection. Based on the hydraulic characteristic of reversible pump-turbine, the reason why the minimum pressure at draft tube occur in the combined conditions and the dangerous interval time are analyzed bonding with the water conveyance system layout of pumped storage plants and the practical operation of pump-turbine. The research indicate that when reversible turbines in the same hydraulic unit reject load successively, the maximum pressure at spiral case maybe lower to some extent compared with load rejections simultaneously, but the change of minimum pressure drop at draft tube is great along with different interval time, which endangers the water conveyance system badly, especially in high head pumped storage plants, and should be pay great attention to it. Combining the practical operation of pump-turbine with calculation in theory, it would be the dangerous interval time of load successive rejection of pump-turbines after the first pump-turbine rejects load and its runaway speed achieve speed peak, the pressure of draft tube would drop the minimum once the other set in the same hydraulic unit also reject load at the moment.

scholarly journals The Dynamic of Synchronous Generator under Unbalanced Steady State Operation: A Case of Virtual Generator Laboratory

2015 ◽  
Vol 5 (6) ◽  
pp. 1292
Author(s):  
Sugiarto Kadiman ◽  
Arif Basuki ◽  
Mytha Arena
Keyword(s):  
Steady State ◽  
Synchronous Generator ◽  
Simulation Method ◽  
General Concept ◽  
Virtual Laboratory ◽  
Synchronous Generators ◽  
Steady State Condition ◽  
Generator Model ◽  
Steady State Operation ◽  
Unbalanced Voltage

The purpose of this study is to design and develop a synchronous generator virtual laboratory for undergraduate student courses, which can be treated as an accessorial tool for enhancing instruction. Firstly, the study reviews the general concept and algorithm of synchronous generator model. Secondly, the simulation method of this system is discussed. Finally, the paper introduces its example and analysis. One of the major objectives of this project is the dynamics of synchronous generators connected to the 500 kV EHV Jamali (Jawa-Madura-Bali) System under unbalanced steady state condition that could be modeled as a balanced synchronous generator’s model with unbalanced voltage inputs. The balanced synchronous generator model based on the rotor’s qd0 reference frame was chosen to substitute generator’s model embeded in loadflow analysis. The verification of the proposed generator’s model was checked by comparing it with a PSS Tecquiment NE9070 simulator. The unbalanced voltage inputs of generator were derived utilizing the loadflow analysis by determining the phase and sequence currents, and average bus voltages of the 500 kV EHV Jamali grid considering unbalanced portion variations. Meanwhile, the load locations having significant effect on the test generators are obtained by using the electricity tracing method. The developed virtual laboratory with a given example demonstrated the usefulness of the tool for studying synchronous generator under unbalanced steady-state operation.

Numerical and Experimental Investigation on Unsteady Inflow Conditions of a Pump-Turbine at Low Load

2014 ◽  
Author(s):  
S. Erne ◽  
G. Edinger ◽  
E. Doujak ◽  
C. Bauer
Keyword(s):  
Draft Tube ◽  
Flow Behavior ◽  
Low Frequency ◽  
Wall Pressure ◽  
Time Dependent ◽  
Discrete Fourier Transformation ◽  
Computational Domain ◽  
Pressure Measurements ◽  
Transient Pressure ◽  
Pump Turbine

This paper examines the occurrence of prerotation and reversal flow in the conical draft tube of a pump-turbine by using different turbulence models and compares the results to experiments. The computational domain consists of the entire geometry of a reduced scale pump-turbine. The results based on time-dependent computational fluid dynamics (CFD) are compared to laser doppler velocimetry (LDV) and wall-pressure-measurements in the conical part of the draft tube. Beside the LDV measurements, pressure fluctuations induced by complex flow patterns are also recorded and analyzed. The capability of simulations is assessed by an evaluation of the global integral values of the pump-turbine. The velocity profiles in axial and circumferential directions are compared at two measurement planes for two part-load operating points. The increased wall pressure distribution caused by swirling inflow is compared to the time averaged wall static-pressure from experiments. When operating at unstable pump conditions, an unsteady flow behavior arises in form of co-rotating vortices upstream of the impeller inlet. Analysis of the inlet flow shows continuously appearing and decaying vortex ropes in the conical draft tube. On the basis of these observations, discrete fourier transformation (DFT) analysis provides the power spectrum of the simulated time dependent pressure signal in the draft tube cone, where significant peaks below the runner rotational frequency are observed. The spectral analysis applied to transient pressure measurements at the draft tube wall shows dominant peaks in the low frequency region, which may indicate weak vortex structures rotating at low frequency.

Mechanism and influence factors of hydraulic fluctuations in a pump-turbine

2021 ◽  
pp. 095765092110285
Author(s):  
Xiaolong Fu ◽  
Deyou Li ◽  
Hongjie Wang ◽  
Guanghui Zhang ◽  
Xianzhu Wei
Keyword(s):  
Guide Vane ◽  
Three Dimensional ◽  
Influence Factors ◽  
Simulation Method ◽  
Power Station ◽  
Pump Turbine ◽  
Available Energy ◽  
Exciting Forces ◽  
Pump Storage Power ◽  
Pumped Storage

Pumped-storage power technology is currently the only available energy storage technology in the grid net, and its reliability is receiving attention increasingly. However, when a pump-turbine unit undergoes runaway transitions, hydraulic fluctuations intensively affect the reliable operation of a pumped-storage power station. To reduce hydraulic fluctuations, this study investigated the formation mechanism of hydraulic fluctuations and explored its influence factors. In this study, a developed one-dimensional and three-dimensional (1 D-3D) coupling simulation method was adopted. Transient runaway transitions of a pump-turbine with three different inertias (0.5 J, 1 J, and 2.0 J) at three different guide vane openings (21°, 15°, and 12°, respectively) were simulated and compared. The results suggest that, at smaller guide vane openings (15° and 12°), water hammer owing to the increase in rotational speed is the primary unstable issue compared to the pulsation of radial hydraulic exciting forces on the runner. However, at a larger guide vane opening (21°), the latter owing to the back-flow near the runner inlet is the primary unstable issue. Moreover, it is found that a sufficiently large inertia improves the hydraulic fluctuations of the pump-storage power station, particularly in reducing the pulsation of radial hydraulic exciting loads on the runner. The findings of this study provide a valuable reference for determining suitable rotor inertia.

A New Methodology for Suppressing Pressure Pulsation in a Draft Tube by Grooved Runner Cone

2011 ◽  
Author(s):  
Takeshi Sano ◽  
Masayuki Ookawa ◽  
Hiromi Watanabe ◽  
Nobuaki Okamoto ◽  
Hiroshi Yano ◽  
...  
Keyword(s):  
Pressure Fluctuation ◽  
Pressure Pulsation ◽  
Draft Tube ◽  
Water Injection ◽  
Hydraulic Turbine ◽  
High Amplitude ◽  
Negative Influence ◽  
Spiral Groove ◽  
Pump Turbine ◽  
Partial Load

High amplitude of pressure fluctuation is observed in a draft tube, for the case of partial load operation. Several methods had been reported to decrease the amplitude so far, such as, air or water injection to the draft tube, fins on the draft tube surface, or runner replacement with optimized velocity profile at runner exit. However, several problems for each method can be considered, such as, negative influence on efficiency, high cost, technical difficulties for installation, and so on. To solve these problems and satisfy the demand for decreasing the amplitude of pressure fluctuation simultaneously, a new runner cone with grooves on the surface was developed. As for the case with reversible pump turbine, grooved runner cone was developed with unsteady draft tube calculation based on Design of Experiment (DOE) method, and confirmed by model tests. Finally, developed runner cone was installed to the prototype pump turbine, and predicted performance was confirmed by on-site tests. Using this result, development of a new runner cone for hydraulic turbine had been started. For this case, meridian shape of the runner cone was also selected as a design parameter. Finally, we obtained the optimized shape, “diverged runner cone with spiral groove”, and the performance is confirmed by the model test. In this paper, details of development, especially for the case of hydraulic turbine and considerations of the mechanism are treated.

scholarly journals Transient Simulation for a Pumped Storage Power Plant Considering Pressure Pulsation Based on Field Test

Energies ◽  
2019 ◽  
Vol 12 (13) ◽  
pp. 2498 ◽  
Author(s):  
Lei Zhang ◽  
Jian Zhang ◽  
Xiaodong Yu ◽  
Jiawen Lv ◽  
Xiaoying Zhang
Keyword(s):  
Single Unit ◽  
Pressure Pulsation ◽  
Working Condition ◽  
Draft Tube ◽  
Pressure Rise ◽  
Power Station ◽  
Rise Rate ◽  
Spiral Case ◽  
Time Average ◽  
Pumped Storage

In this study, fast Fourier transform and inverse transform are adopted for noise reduction filtering the data of load rejection pressure of a single unit in a one-tube, four-unit pumped storage power station. Five-spot triple smoothing method is used to extract the time-average and pulsation value of the water hammer pressure of the spiral case and draft tube inlet. The reasonable correction formula is put forward, and the pulsating pressure rise rate of the spiral case (4.44%) and the draft tube inlet (−1.22%) are obtained. A mathematical model is also established for the transition process of the water conveyance and power generation system of the pumped storage power station, and the field single-unit load rejection condition is simulated. The simulation results are consistent with the measurements, and the accuracy of the calculation model in predicting the time-average pressure of water hammer is verified. Thus, the extreme successive load rejection conditions can be simulated based on the proposed model. Combining with the pulsating pressure rise rate of unit, the actual extreme value of extreme working condition is reasonably calculated. The conclusion shows that the pressure of spiral case and draft tube inlet after considering pressure pulsation can meet the control requirements, avoid the damage caused by extreme working condition test to unit, and ensure the operation safety of unit.

scholarly journals Computational Performance of Disparate Lattice Boltzmann Scenarios under Unsteady Thermal Convection Flow and Heat Transfer Simulation

Computation ◽  
2021 ◽  
Vol 9 (6) ◽  
pp. 65
Author(s):  
Aditya Dewanto Hartono ◽  
Kyuro Sasaki ◽  
Yuichi Sugai ◽  
Ronald Nguele
Keyword(s):  
Heat Transfer ◽  
Steady State ◽  
Natural Convection ◽  
Lattice Boltzmann ◽  
Numerical Results ◽  
Convection And Heat Transfer ◽  
Steady State Condition ◽  
Physical Systems ◽  
Flow And Heat Transfer ◽  
Computational Performance

The present work highlights the capacity of disparate lattice Boltzmann strategies in simulating natural convection and heat transfer phenomena during the unsteady period of the flow. Within the framework of Bhatnagar-Gross-Krook collision operator, diverse lattice Boltzmann schemes emerged from two different embodiments of discrete Boltzmann expression and three distinct forcing models. Subsequently, computational performance of disparate lattice Boltzmann strategies was tested upon two different thermo-hydrodynamics configurations, namely the natural convection in a differentially-heated cavity and the Rayleigh-Bènard convection. For the purposes of exhibition and validation, the steady-state conditions of both physical systems were compared with the established numerical results from the classical computational techniques. Excellent agreements were observed for both thermo-hydrodynamics cases. Numerical results of both physical systems demonstrate the existence of considerable discrepancy in the computational characteristics of different lattice Boltzmann strategies during the unsteady period of the simulation. The corresponding disparity diminished gradually as the simulation proceeded towards a steady-state condition, where the computational profiles became almost equivalent. Variation in the discrete lattice Boltzmann expressions was identified as the primary factor that engenders the prevailed heterogeneity in the computational behaviour. Meanwhile, the contribution of distinct forcing models to the emergence of such diversity was found to be inconsequential. The findings of the present study contribute to the ventures to alleviate contemporary issues regarding proper selection of lattice Boltzmann schemes in modelling fluid flow and heat transfer phenomena.

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