A static and dynamic model for hydraulic transient calculation of three-throttled-orifice surge tank was established based on the basic equations of surge tank, by using structure matrix method (matrix analysis of structure?). Control conditions in an engineering practice were calculated by a simplified model and a three-throttled-orifice model respectively. The results indicate that the maximum pressure at the volute end, the maximum rising rate of unit speed and the water level extremum of the surge tank are basically identical by using these two models, but the minimum pressure at draft tube inlet is significantly different. The three-throttled-orifice model was found capable of calculate the flow between throttled orifices at constant state and the pressure behavior at draft tube inlet during the transition accurately. The selection of the resistance factor is discussed in the end, and it is proved that the resistance factor is allowed to have a certain tolerance in the transition calculation, which will not obviously affect the maximum pressure at draft tube inlet and water level extremum of the surge tank. This research can provide reliable reference for the transient calculation of three-throttled-orifice surge tank in similar engineering practice.
The analysis of hydraulic disturbance is an important part of the analysis of the hydraulic transient process of a hydropower station. This paper introduces the relationship between the grid-connected operation mode of the power station and the hydraulic disturbance by the power station system, and performs simulation calculations under the same boundary conditions according to the hydraulic disturbance test cases, and predicts the extreme control conditions which provides the basis for the safe operation of the power station. It also provides reference for the design and calculation of similar projects.
In the process of calculating the analytical formula of the critical stable section area of the surge tank, the influence of the time constant of the flow inertia in the pressure pipe is ignored by all the formulas, including Thoma’s formula and the E/N correction formula. In this paper, a fifth-order analytical model of a hydraulic turbine generator set with a surge tank is established after considering the inertia of the flow in the pressure pipe. Then, the relationship between the flow inertia in the pressure pipe and the critical stable section area of the surge tank is systematically analyzed by using this fifth-order analytical model. Finally, combined with a typical hydropower station, the influence of flow inertia of the pressure pipe on the stable section of the surge tank caused by the changes of head, flow and the length of the pressure channel is analyzed.
Accurate prediction of transition process is an important issue in the design and operation of pumped storage power station. In this paper, combined with load rejection test of J Pumped-storage Power Station, the basic equation of water flow motion and the element matrix equation of the turbine were established first, and the calculation model was established through HYSIM software. Then for the 100% load rejection control condition, the inversion calculation and analysis of actual load rejection test under the same boundary condition were carried out. According to the comparison process line between numerical simulation and measured data of the surge-chamber water level, a comprehensive combination calculation was used to calibrate the impedance coefficient of surge-chamber. Finally, based on the calibrated impedance coefficient, a new calculation model was established, and the inversion calculation was carried out again. By comparing the numerical simulation and measured data of volute and tail pipe pressure, the pressure pulsation characteristics of the characteristic parameters of the unit were obtained, and the correction value of pressure pulsation was obtained. The calibration method and pressure pulsation correction method adopted in this paper can provide a reference for the inversion analysis of load rejection test in similar power stations.
K hydropower station is a hydraulic engineering with the main task of power generation, which is also a typical hydropower station with low head, large discharge and long tail water conveyance system. The hydraulic characteristics of these-type hydropower stations are of high water inertia, large amplitude of surge chamber water level fluctuation and poor stability of units. Therefore, due to the control requirements of the stability, the area of the horizontal section of the surge chamber is usually large, which leads to the long period of water level fluctuation of the surge chamber and the relatively long time of unit output oscillation in the transition process, and the regulating quality of the unit is often difficult to meet the control requirements due to the large inertia time constant of the water flow in the water conveyance system and the unique characteristic curve of unit. It is important to design appropriately to ensure the safe and stable operation of the hydropower station. In this paper, it is shown the process of hydraulic design of these-type stations. According to the design of K hydropower station, the simple surge chamber and restricted orifice surge chamber are compared in terms of hydraulic characteristics including the head loss of steady operation, the water level fluctuation of transition process and the stability of operation. Based on the optimized restricted orifice surge chamber, the overall calculation and analysis of the hydraulic transition process and the stability analysis of K hydropower station are carried out, it is concluded that the unit stability quality of the K power station is fine and the maximum pressure of pipe is in control, which provide strong support for the safe and stable operation of K station. The comprehensive and thorough analysis in this paper can provide reference for the design of the similar projects.
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