Research On Hydraulic Calculation Of Surge Chamber Of Lala Mountain Hydropower Station

When designing a hydropower station with a diversion pressure piping system,in order to ensure the safe and stable operation of the hydroelectric generating set and the pressure diversion channel system,it is often necessary to set up a surge chamber.There are four kinds of surge-chamber traditionally,such as impedance type,differential type,chamber type and overflow type and so on.For diversion-type power plants with short diversion channels,especially those plants with water flow inertia time constant Tw between 2 and 4,whether a surge chamber is needed requires comparison and calculation.The surge chamber provides a large free water surface,which is equivalent to dividing the water diversion system into two sections,which can alleviate the water hammer wave.The pressure pipeline downstream of the surge chamber is shortened because of the transmission distance of the water hammer wave,so the size of the water hammer wave is also weakened,which can improve the operating conditions and power supply quality of the unit.In recent years,with the vigorous development of China's hydropower industry,more and more hydropower stations have been built or are under construction in China.Most hydropower stations with long diversion channels are equipped with surge tanks.The paper described the current status of domestic and international research and development of the hydraulic transition process of the diversion power generation system,and explained the important role of the surge chamber in the system.Discussed whether the diversion power generation system needed to set up the surge chamber and the four measures to replace the surge chamber,which were pressure regulating valve,safety valve-burst membrane system,water resistance,and diverter.No matter of which method,it could alleviate the load dumping conditions of the system,but it had no effect on small fluctuations.Only by adjusting the parameters of the turbine governor can the small fluctuations be resolved.The thesis took the engineering data of Lalashan Hydropower Station in Batang County,Ganzi Prefecture,Sichuan Province as an example,and preliminarily judged that the water inertia time constant of the power station is 2.8s,and the surge chamber was between the range that can be set and not set;It was recommended to set up a pressure regulating chamber in the area where the governor has poor governing performance.The thesis applied the characteristic line calculation method in the basic theory of transient flow to establish the mathematical model of the diversion and power generation system of the hydropower station with surge tank and the mathematical model of thediversion and generation system of the hydropower station without surge chamber,and compile the corresponding calculation program based on it.Various working conditions were drawn up in accordance with the requirements of the specification,and a detailed calculation and adjustment study of the hydraulic transition process of the diversion and power generation system of the hydropower station was carried out.We found that the adjustment of the scheme without the surge chamber ensures that the increase in the speed of the computer group and the increase in the pressure of the volute cannot meet the requirements of the relevant design specifications,and the stability of the small fluctuations is poor.The dynamic quality of the regulating system with the surge chamber scheme was obviously better than the scheme without the surge chamber.It is determined that this hydropower station needs to set up a surge chamber.The thesis gave the water level fluctuation process and volute pressure change value of the surge chamber during the hydraulic transition process,gave the structure and size suggestions of the surge chamber of this hydropower station,analyzes the scheme with surge chamber and the case without surge chamber.The scheme adjustment guaranteed the calculation results.The small fluctuation stability of the diversion power generation system with and without surge chamber was calculated,and some research results with reference value to the actual project were obtained.