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 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.

Study on the Reversible Pump-Turbine Closing Law and Field Test

2006 ◽  
Author(s):  
Jian Zhang ◽  
Jianyong Hu ◽  
Ming Hu ◽  
Jie Fang ◽  
Ning Chen
Keyword(s):  
Field Test ◽  
Turning Point ◽  
Large Range ◽  
Rotation Speed ◽  
Sudden Change ◽  
Pressure Rise ◽  
Pump Turbine ◽  
Water Conveyance ◽  
Three Stages ◽  
Pumped Storage

In the operation of pumped storage plant, the sudden change of load in the large range often happen, the design of reversible pump-turbine emergency closing law should satisfy limit of rotation speed-rise and pressure-rise. The broken-line closing law of reversible pump-turbine usually used in pumped storage plants is discussed and based on full hydraulic characteristic of reversible pump-turbine, the broken-line closing law of three stages with delayed segment is designed, virtues and defects of the pump-turbine emergency closing law are also analyzed. Numerical calculation and field test indicate that water hammer in pumped storage plant water conveyance system caused by wicket gate closing together with rotation speed-rise, is effectively reduced by the closing laws presented above, especially to the latter, its turning point position can change following the different operating case, the detection of poor robustness is overcome. A new idea for the design of the reversible pump-turbine emergency closing law is proposed with good prospects.

scholarly journals ANALISIS AERODINAMIKA PADA PERMUKAAN BODI KENDARAAN MOBIL LISTRIK GASKI (GANESHA SAKTI) DENGAN PERANGKAT LUNAK ANSYS 14.5

2017 ◽  
Vol 5 (2) ◽  
Author(s):  
Yudi Prihadnyana ◽  
Gede Widayana ◽  
Kadek Rihendra Dantes
Keyword(s):  
Fluid Flow ◽  
Flow Rate ◽  
Body Modification ◽  
The Body ◽  
Vehicle Body ◽  
Maximum Pressure ◽  
Air Velocity ◽  
Electric Cars ◽  
Minimum Pressure ◽  
Electric Car

Dengan perkembangan teknologi yang semakin maju bentuk dari bodi sebuah kendaraan sangatlah diperhitungkan untuk mencapai tujuan-tujuan tertentu. Untuk itu, dilakukan analisis Aerodinamika pada pemukaan bodi mobil listrik gaski dengan menggunakan perangkat lunak Ansys 14.5, yang bertujuan untuk mengetahui aliran fluida dan nilai koefisient drag pada mobil listrik Gaski bodi standar dan modifikasi. Setelah proses analisis dilakukan, didapatkan hasil velocity udara maksimum body standar sebesar 17,4324 m/s dan body modifikasi sebesar 17,7321 m/s dan pressure maksimum yang terjadi pada mobil listrik Gaski body standar sebesar 83,2143 Pa, dan minimum sebesar -189,879 Pa. sedangkan pressure maksimum yang terjadi pada mobil listrik Gaski body modifikasi sebesar 83,2143 Pa. dan minimum pressure diperoleh -182,128 Pa. nilai Koefisient drag dari mobil listrik Gaski body standar sebesar 0,00474 sedangkan pada body modifikasi sebesar 0,00407. Dari hasil peneletian tersebut didapatkan bahwa setalah dilakukan modifikasi pada bodi mobil listrik gaski terdapat beberapa perubahan diantaranya terjadi peningkatan kecepatan laju aliran udara atau velocity udara meningkat 1,72 % sedangkan tekanan yang diterima oleh bodi setelah dimodifikasi menurun 1,39 % dan Nilai koefisien drag pada mobil listrik gaski dapat diturunkan 14,14 % setelah dimodifikasi.Kata Kunci : kata kunci : Aerodinamika, aliran fluida, bodi kendaraan, With the technological development of the more advanced form of the body of a vehicle is very calculated to achieve certain goals. For that purpose, Aerodynamic analysis was performed on the electric car body surface by using Ansys 14.5 software, which aims to find out the fluid flow and coefficient value of drag on electric car Gaski standard body and modification. After the analysis process is done, the result of the maximum air velocity of the standard body is 17,4324 m / s and body modification of 17,7321 m / s and the maximum pressure happened to electric car Gaski body standard equal to 83,2143 Pa, 189,879 Pa. While the maximum pressure that occurs on electric cars Gaski body modification of 83.2143 Pa. And the minimum pressure obtained -182.128 Pa. Coefficient value of drag from electric car Gaski body standard of 0,00474 while at body modification equal to 0,00407. From the results of the research was found that after modification on the body of electric car gaski there are some changes such as increase the speed of air flow rate or air velocity increased by 1.72%, while the pressure received by the body after modification decreased 1.39% and the value of drag coefficient on Electric car gaski can be derived 14.14% after modified.keyword : Keywords : Aerodynamic, fluid flow rate, Vehicle body.

Trapped air in ventilated excised rat lungs

1976 ◽  
Vol 40 (6) ◽  
pp. 915-922 ◽  
Author(s):  
D. G. Frazer ◽  
K. C. Weber
Keyword(s):  
Stress Relaxation ◽  
Flow Rate ◽  
Lung Volume ◽  
Transpulmonary Pressure ◽  
Maximum Pressure ◽  
Lung Inflation ◽  
Minimum Pressure ◽  
Trapped Air ◽  
Rat Lungs ◽  
Reference Pressure

Degassed excised rat lungs were ventilated in a water-filled plethysmograph with the carina as the zero pressure reference. Pressure-volume curves were recorded from a minimum transpulmonary pressure (Pmin) of -5 cmH2O to a maximum pressure (Pmin) of 30 cmH2O. An index of the minimun volume for the lung (Vm) divided by the maximum lung volume for the same cycle (Vmax) was used as an index of the amount of air trapped within the lung. As the flow rate was decreased from 38.2 to 1.9 ml/min, there were significant increases in the amount of air trapped in the lung. As the maximum pressure was decreased to 25 and 20 cmH2O, or the minimum pressure was increased to 6 and 11 cmH2O, the amount of trapped air in the lung significantly decreased. The rate of lung inflation had a much greater influence on the amount of trapped air than either the deflation rate or stress relaxation. The results are consistent with the theory that bubbles are formed during inflation and are the main cause of air trapped in the excised lung.

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

1969 ◽  
Vol 91 (3) ◽  
pp. 387-395 ◽  
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.

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

2019 ◽  
Vol 141 (8) ◽  
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.

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