Hydraulic Transition Process Analysis Of Large Pumping Station

As a developing country, China’s economy is based on agriculture. For the reasons of large population and vast territory, the uneven distribution of resources is a big problem, especially the imbalance of the water resource. Water is resourceful in the south of China, but is comparatively deficient in the northwest. The uneven distribution of water resources bring disadvantages to our country’s economy development, and lead to frequent droughts and floods, which greatly affected the lives and property of our people. In order to alleviate the problem of water shortage areas, large-scale water pumping station obtained a dramatic rise. Hydraulic transient problems (also called water hammer) in the water system of pumps station are always come out in the long-distance water system. Water hammer phenomenon has been a problem currently plaguing engineers. Especially the water hammer caused by pumping-off is the most serious phenomenon. The unsteady flows in a pump system are thought belongs to the unsteady flows in a pressure system, thus the changes of boundary conditions, as well as the occurrence of regulative or non-regulative operating conditions will turn the steady flows into transient flows. Generally, several water pumps share one same surge tank and penstock. If a certain factor cause one of the pumps to work in a state of transition of large fluctuation, the pressure changes between the upstream and the downstream of the pump station, as well as its diversion and tailrace systems, will influence the other pump sets working under the same surge tank and penstock, making them in a transition process as well. Consequently a hydraulic disturbance arises. To ensure a safe and steady working condition of the pump sets, it is of crucial significance to analyze the degree of this disturbance, and minimize its influences of the systematic parameters. The main works of this paper are listed in the following:(1) Taking a pumping station project with large scale centrifugal pumps as working example, an extreme transient flow in the pumping system caused by tripping pump due to electric supply failure was analyzed.(2) Based on the corresponding mathematical model of the hydraulic components and the flow equation, employ the method of characteristics, apply the numerical simulation method, and using the software of the Deltares WANDA3.71, we build the mathematical model of the regulation system of the pump station.(3) Analysis several factors that will have influence on the hydraulic disturbance between the units, such as the operating conditions, the parameters of the surge shaft, and the parameters of the pipeline.(4) Pumping-off water hammer on parallel units in the pump station were calculated and analyzed. Calculated the operating conditions under the pumps’ parallel operation, and analyzed the hydraulic disturbance of the system when the tripping pump occurs.The results show that the rest running pumps in the system due to a sudden tripping pump disturbance are heavy disturbed when the tripping pump is suddenly failed from the pumping system. The flow rate and input power for the working pumps are greatly jumped shortly. The strongly transient impulsion to the pumping system is quite significant.