Document Type : Complete scientific research article
Authors
1
.Sc. in Water Structures, Department of Water Engineering, Agricultural Sciences and Natural Resources University of Khuzestan, Iran.
2
Associate Professor, Department of Water Engineering, Agricultural Sciences and Natural Resources University of Khuzestan, Iran.
3
Assistant Professor, Department of Water Engineering, Agricultural Sciences and Natural Resources University of Khuzestan, Iran.
4
Instructor, Department of Mechanical Engineering, Islamic Azad University, Behbahan, Iran.
10.22069/jwsc.2024.21567.3667
Abstract
Introduction: The occurrence of phenomena such as surges in complex devices such as turbines, and problems caused by neglecting safety precautions, may result in significant economic damage and losses to the transmission system. On the other hand, electricity production is a key factor in the economic and social development for developing countries. Recently, institutions involved in electricity supply have recommended pump as turbine projects as hydroelectric power plant for supplying electricity to rural areas due to their economic benefits. The issue under investigation in this study is the effect of pump shutdown on surge occurrence and its effects on the water transmission line.
Methodology: The case study project is the water transmission line to the city of Masjed Soleyman located in the northeast of Khuzestan province, Iran. In this study, by using WaterGEMS software, the route of the transmission line, the type and diameter of the pipes, pressure relief valves, tanks, etc., have been defined and modeled in steady state. After processing the line in steady state, in order to investigate the replacement of the PATs with pressure relief valves and its shut-down effect on the water hammer phenomenon created in the transmission line, the model created in WaterGEMS is called in the Bentley HAMMER CONNECT software to analyze the unsteady state condition. The phenomenon of surge has been investigated in three scenarios as follows: The first scenario involves studying the flow conditions in a steady state without any changes in the transmission line. The second scenario involves replacing the pressure relief valve at kilometer 054+0 from the Tang-e Mo reservoir with a reverse pump. The third scenario involves replacing the pressure relief valve at kilometer 700+3 from the Tang-e Mo reservoir with a reverse pump.
Results: When the pressure relief valves are working, the flow velocity in the pressure relief valve in 3+700 km, equivalent to 2.07 m/s, and the pressure before the pressure relief valve is equal to 157.7 meters of water and reaches 20 meters of water. Also, in the pressure relief valve 0+054 km from the reservoir, the speed is 2.1 m/s and the pressure decreases from 104.77 m to 13.2 m of water, respectively. For second scenario, in the first pressure relief valve, 91 meters of pressure is wasted. In this case, the PATs with turbine flow and pressure have replaced the existing pressure relief valves. The inlet and outlet valves of the first PAT are closed in 20 seconds and the flow through it is reduced to zero. Third scenario considers the water hammer impact resulting from shutdown of the PAT (at 3+700 km) on the transmission line. 137 meters of pressure is wasted in the second pressure relief valve. Also, the flow through it is 580.189 liters per second. In this case, the inlet and outlet valves of the PAT are closed in 20 seconds. It is necessary to explain that if the valves of the PAT (at 3+700 km) are closed, the downstream flow will also decrease; But due to the bypass of the PAT, the input flow to the downstream pumps does not reach zero and the pumps do not exit the circuit.
Conclusions: The results indicate that the occurrence of the surge due to the failure of the PAT(s) installed in the transmission line, despite the creation of positive and negative pressure waves in the transmission line, does not cause serious disturbance in the pipeline. It is also concluded that the thickness of the steel material selected for the pipeline has the required strength to withstand the maximum and minimum pressures.
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