| In order to alleviate the contradiction between water supply and demand in the region,Long distance water conveyance projects,even trans-regional and inter basin water conveyance projects,have become an inevitable trend of water supply projects at present stage.The number and scale of it are increasing and enlarging,which is one of the major characteristics of water conservancy in China in twenty-first Century.The contradiction between supply and demand of water resources in Shanxi province is more prominent,the long distance water supply project is an important part of the new water source project in our province.In order to fundamentally solve the water problem in Shanxi,the Shanxi Provincial Committee and the provincial government,in accordance with the Central Committee's decision to accelerate the development of water conservancy reform and development,and the requirements of the State Development and Reform Commission and the Ministry of water resources,the Shanxi large water network project of "two vertical ten transverse,six rivers connected and covering the whole province" was fully planned in 2011.In order to ensure the stable operation of the project under the design condition,the key technical problems such as the steady operation of the project,the hydraulic dispatching of cascade pumping stations,the hydraulic transition process and the safety protection of water hammer should be deeply calculated and analyzed.Based on Shanxi Xiangning County along the Yellow River Water Supply Project,the operation characteristics calculation and research of the cascade water supply pump station and the gravity flow water supply project are carried out.In order to make the water supply system safe,efficient and economical,the reasonable operation suggestion and water hammer protection measures are put forward for the project.The contents of this paper are as follows:(1)The steady state operation parameters of the pumping stations at all levels in the cascade water extraction project are calculated.The working point of steady state operation is the basic hydraulic characteristic parameter of water hammer calculation.A steady state mathematical model of a pump with constant speed and parallel operation of the same type and the same type of pumps under variable speed parallel operation is established.The steady working points of pumping stations at different levels are solved respectively.(2)The simulation calculation of the hydraulic transition process of the pumping stations at all levels in the cascade water extraction project.The mathematical model of hydraulic transition process is established,and the basic principle of the characteristic line method is applied to solve the mathematical model of water hammer calculation.Based on the calculation result of water hammer in pumping station,the causes of water hammer are analyzed,and the suggestion of pipeline protection is put forward.(3)The working principles and boundary conditions of various water hammer protection measures such as hydraulic control butterfly valve and air valve are analyzed,and the corresponding mathematical models are established,so as to provide basis for the simulation and calculation of the water hammer of different protective measures.(4)According to the operation range of flow in Shanxi Xiangning County along the Yellow River Water Supply Project of pumping stations at all levels,by changing the number and pump speed operation mode,change rule of the flow and power of hydraulic parameters.The hydraulic balance analysis is carried out for the different flow demand of the two stage station.The rational water pump operation mode should be selected for the first class pump station and the first stage pump station under the different flow demand.(5)The gravity Xiangning Shanxi County water supply project of water pipe flow,steady running conditions;the protective measures,calculated at the end of the needle valve in the closed mode under different hydraulic transition process,analysis of the change of pipeline water hammer pressure,the optimal valve closing law;on the basis of water pipeline valve water hammer the calculation results,put forward reasonable pipeline protection scheme,to ensure the safe operation of the project.(6)Using Visual Basic 6.0 as the development language and SQL Sever 2000 as the auxiliary tool,the numerical simulation software for hydraulic characteristics of gravity flow water conveyance system is developed.The steady state analysis module of gravity flow water supply project and the water hammer analysis module are set up,and the functions of data export and graphic output of the calculation results of various working conditions are realized.Through the analysis and study of this paper,it provides technical support for the safety and economic operation of the high lift,small flow and long distance yellow pumping station of Shanxi province.In view of the complex transient conditions of water hammer,the change mechanism of the inlet and exhaust flow coefficient of the air valve has not been fully revealed,and the influence of the engineering calculation results is great.Further research is needed. |
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