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Abstract: The hydraulic principle and characteristics of full hydraulic control pressure regulating valve are expounded. The calculation principle of transition process and parameter setting when using pressure regulating valve are analyzed. During the operation of the hydropower station, when the hydrogenerator suddenly load shedding, the governor automatically controls the turbine to quickly close the guide vane, the pressure pipelines Produced within the pressure and the unit speed increased. For power plants with longer pressure diversion channels, changing the guide vane closing time may not always allow both pressure and speed rise to be within acceptable limits. For the time being, it is common to adopt the methods of setting surge tanks or pressure regulating valves to solve the contradiction between pressure and speed rise and ensure the safe operation of the power station. However, setting surge pipes requires large investment and long construction period, while some power plants are limited to topography and geological conditions, and it is also difficult to build surge tanks. Therefore, there is a clear advantage for this type of small- and medium-sized power plants to adopt the pressure regulating valve scheme . The current production of full hydraulic control TFW-type pressure regulator and guide vane hydraulic linkage features, safe, reliable, low investment, short duration and other advantages. Since the 80s of last century, nearly 100 hydropower stations in China have been canceled surge tanks, the use of TFW-type hydraulic control valve, has not occurred with a safety accident. Zhejiang Jin Hang, Xuanping Creek and other hydropower stations have been safely operated for many years. Even in developed countries, such as Norway, large numbers of pressure regulating valves are used in hydropower stations instead of surge tanks (the rated head is 158m and the single-capacity TJΦRHM hydropower station is 60MW one example). Pressure regulator valve hydraulic principle, characteristics, the transition process for the following elaboration. 1, full hydraulic control pressure regulating valve hydraulic principle Full hydraulic pressure control TFW type pressure regulating valve basic movements are: fast open, slowly closed; small load changes, the pressure regulator valve does not move; rejection greater load, the pressure The valve is open and has the performance of closing two sections of the guide vane; the pressure regulating valve does not work when the load is increased. The modified governor special main valve and pressure regulating valve hydraulic control system shown in Figure 1, which is characterized by all the direct use of pressure oil for control and operation, the hydraulic principle is as follows: (1) unit load unchanged. The main pressure valve piston in the "balance position", the pressure oil through the P1 chamber through the throttle A into the pressure regulator valve closing chamber TG, the pressure regulator opens the chamber TK through the exhaust chamber O2. As the pressure regulator valve closing chamber pressure greater than the water on the valve thrust, so the pressure regulator valve is closed. If the pressure regulator valve is already open, it will move toward the closing side. (2) when the unit reduces the load (about 15% of the rated output of the unit). As the main pressure valve on the smaller amount of displacement, in the "part load reduction" position, only a small amount of pressure oil from the P1 chamber through the throttle A into the guide vane relay closing chamber JG cavity slowly turn the guide vane, pressure regulator The pressure in the valve closing chamber slightly decreases, but it is still larger than the water thrust on the valve disc. The pressure regulating valve opens the chamber TK to drain the oil chamber O2, so the pressure regulating valve remains closed. (3) When the unit instantaneous rejection of large load (more than 15% of the unit rated output). Main pressure valve piston on the larger amount of displacement, in the "rejection of a larger load" position, a large number of pressure oil directly through the TK cavity into the pressure regulating valve relay open the chamber, the pressure regulator valve opens quickly, and the regulator closes the cavity TG and Guide vane relay closed chamber JG connectivity, guide vane relay opening chamber JK drain row O2, guide vane quickly closed. So the pressure regulator valve opens quickly, the guide vane closes quickly, both are synergistic and the lag time is zero. (4) When the unit by load. Main pressure valve piston down, in the "load" position, the pressure oil P1 directly into the guide vane relay opening chamber, the pressure regulator valve closing chamber pressure slightly reduced, but still greater than the water on the valve thrust, pressure regulating valve Open the chamber TK through the exhaust chamber O2, so the pressure regulator valve remains closed. (5) two guide vanes closing device. When the pressure regulator valve starts to open rapidly, due to the restriction of the throttle valve C, the hydraulic pressure rapidly rises, the hydraulic check valve opens, and the pressure regulating valve closes the pressure oil in the cavity TG and enters the guide vane relay closing chamber JG. The amount of oil back to the governor through the throttle valve back to the tank, so the pressure valve to open faster, ahead of the open limit ring limit position, then guide vane relay is not in the fully closed position, only through a small amount The pressure oil from the throttle valve A is slowly closed, thus functioning as a two-stage closing of the guide vane. (6) If the pressure regulating valve fails, the unit can only be shut down slowly by a small amount of pressure oil from the throttle A to ensure that the pressure in the water supply pipe does not rise above the allowable value. (7) the role of the throttle. â‘ Throttle valve A: When the regulating valve fails, the guide vane slow-closing time also determines the closing time of the regulating valve; â‘¡ Throttle valve C: Set the opening pressure of the hydraulic check valve to ensure the quick check valve Open; â‘¢ throttle D: set the guide vane turning off the two positions. 2, Pressure regulating valve characteristics The existing domestic hydraulic control pressure regulating valve is divided into 7 varieties according to diameter and head. It is mainly produced by Sichuan Jiajiang Hydraulic Machinery Factory and Chongqing Hydraulic Turbine Factory. The main parameters are shown in Table 1. (1) structural features. TFW-type pressure regulating valve body with guide vane energy dissipation and gas valve shell, cone or circular valve plate, balance chamber, relay, guide oil chamber, the piston stroke limit ring, into the drain and fill valve And so on. Relay and guide the oil chamber directly connected with the valve shell as a whole, small size, simple structure, compact layout. (2) flow characteristics. According to the type and the Yx / Dx value of the spool valve unit flow Q1x 'see Table 2, resulting in the corresponding pressure regulator Q =, which can draw a variety of pressure regulating valve opening and flow curve . (3) operating characteristics. The range of the minimum operating pressure of the pressure regulating valve is generally between 1.3 and 2.0 MPa, and increases as the working head of the pressure regulating valve increases. The highest operating pressure is generally 2.5 MPa. (4) layout points. Regulator valve arrangement should be as much as possible without increasing unit spacing and span, and with the governor, inlet valve and other coordination arrangements. For vertical units, generally arranged in front of the volute or volute inlet section, for the horizontal unit is generally arranged in the turbine inlet valve volute before the import of steel. Pressure relief valve discharge mode should consider the energy dissipation effect, although the water flow through the pressure regulator to eliminate most of the energy, but should consider the elimination of the remaining energy. 3, set the pressure regulating valve power plant transition process assumes that the turbine, pressure regulating valve flow and time linear relationship, and well matched each other, and therefore the entire water diversion system also showed a linear relationship between the flow changes. Set the regulator after the adjustment characteristics and flow and time changes shown in Figure 2. The solid line in the figure 1 is the process of quick closing of the guide vane; the broken line 2 is the slow closing of the process of the guide vane when the pressure regulating valve is not moving; the dashed line 3 is the process of opening and closing of the pressure regulating valve. In order to control the turbine speed increases, inflection point flow Qg generally choose to open near the no-load, so the turbine no additional energy to make the unit speed continues to rise. At the same time to limit the increase of water pressure, the reduction of unit flow should be controlled within a certain range. 3.1 Calculation Criteria (1) After sudden load rejection, the maximum pressure rise rate of the relevant volute should be considered as follows: â‘ 70% ~ 50% when the rated head is less than 40m; â‘¡ When the rated head is 40 ~ 100m, Should be 50% ~ 30%; â‘¢ rated head greater than 100m, should be less than 30%. After the installation of pressure regulating valve, the pressure rise control conditions in a smaller boost range, combined with the design of the diversion system and the site shut-off device to adjust, access to better shut down. (2) When the load rejection rate of the unit is raised, the rate of increase of the speed is to be considered as follows: â‘ When the unit capacity accounts for a large proportion of the total power system capacity and the frequency regulation task should be less than 45%; â‘¡ When the unit capacity accounts for the total power system capacity Less proportion or bear the base load, should be less than 55%. Taking into account the current allowable increase in speed tends to increase, it is recommended to install a pressure regulating valve after the rate of increase in the calculation of 50% control. (3) When the unit sudden load and partial load rejection, the pressure drop should ensure that the entire pressure pipe has a positive pressure margin of more than 2m in the dead water level of the reservoir. 3.2 Variable Description In addition to the variables described in Figure 2, the variables involved in the calculation are as follows: (1) Ts': unit full closing time without pressure increase and control rate increase; (3) ζ: Allowable rate of pressure increase; (4) QTM: Allowing the unit to reduce the flow rate; (5) Yg: Turbine no-load relative opening; (6) Yk: Turbine when the pressure regulator fully open when the relative opening of the relay. 3.3 Calculation Method (1) According to β seeking Ts' and pressure regulating valve opening time Txk. Calculating Ts' is the same as when no pressure regulating valve is installed, and can be calculated according to the formula in "Hydropower Machinery Design Manual" (Hydraulic Machinery). Thus, Txk = (1-Yg) × Ts' is obtained. When using a guide vane closure law, Txk = Ts'. (2) Find turbine slow closing time Tsm according to ζ. Calculating Ts' is the same as when no pressure regulating valve is used, and can be obtained by using Allevi's formula back calculated according to the characteristics of water hammer phase. (3) Reduced QTM for traffic allowed by the computer group. According to the linear relationship, the time before the regulator starts to close is Txk + Tp, while the allowable rate of unit flow reduction is (Txk + Tp) / Tsm. Therefore, QTM = (Txk + Tp) / Tsm × QT. Calculation, due to the uncertainty of Tp, simplified calculation using QTM = Txk / Tsm × QT is safe. (4) Calculate the pressure relief valve discharge Qx and opening Yx. The decrease of turbine flow rate and the increase of pressure relief valve discharge lead to the change of over flow of the water diversion system. Therefore QTM≤QT-QX-Qg should be guaranteed, and the relief valve discharge QTMis obtained. According to the flow characteristics of the pressure regulator to calculate the required opening Yx, and select the regulator models and parameters. (5) Check the unit caused by the pressure drop. At this point the pressure regulator does not move, the calculation can be a unit from the sudden increase of the load to full load, the calculation method is the same with no pressure regulator valve, according to the formula design manual to calculate the pressure drop , In order to determine a reasonable increase in boot time. (6) Check the rejection part of the load when the pressure regulator valve is still open when the pressure drop. (1) Calculate the hydraulic turbine relay opening when the pressure regulating valve is fully open: Yk = (Tsm + Txk-Ts) / Tsm; (2) According to the curve of the unit relay stroke and the guide vane opening, check the guide vane opening Ï„0, Characteristic curve Check the unit flow rate Q1 ', calculate the turbine flow QT = Q1' × D12 × H (1/2); â‘¢ According to the pressure regulator valve opening to calculate the full-pressure regulator flow: QX =; â‘£ If QX> QT , The pressure drop occurs at the initial stage: Calculate the average flow velocity V of the water diversion system and calculate the flow rate change ΔV = (QX-QT) × V / QT. Calculate the time that the guide vane relay shuts off from Yk opening Tk = Yk × Ts Calculate the pipe characteristic coefficient Ï = a × ΔV / (2 × g × H), σ = L × ΔV / (g × H × Tk), and calculate the pressure drop according to the phase sequence of the maximum water hammer judged by ÏÏ„0. (7) Determine if the pressure piping needs to be optimized according to the pressure drop calculation result. 4, the pressure regulating valve setting parameters regulator before the unit, governor, hydraulic devices and pressure regulating valve equipment should be fully installed and meet the requirements of the start of trial operation, according to the results of the adjustment guarantee calculation of the parameters The tuning. (1) The initial adjustment of the throttle to a certain position, the simulation action several times to rule out the air in the pipeline. (2) cut off the regulator, adjust the throttle A, set the slow closing time of the guide vane. (3) into the pressure regulating valve, adjust the throttle D, setting two turning off the inflection point position. (4) adjust the throttle C, set the starting hydraulic pressure check valve. (5) guide vane fast closing time and increased load starting time is still set by the special main valve opening size. 5 Conclusion (1) TFW-type pressure regulating valve with full hydraulic control with safe, reliable, simple structure, easy adjustment and maintenance, no lag time, less investment and so on, so since the 1980s, the domestic has Nearly 100 hydropower stations in the design canceled the surge tank and the use of TFW-type hydraulic control pressure regulating valve; even if hydropower stations in developed countries are also extensive use of pressure regulator instead of surge tank (Norway TJΦRHM hydropower station is one of the Power station rated head 158m, stand-alone capacity of 60MW). (2) Since the pressure regulating valve of the control system does not operate under the conditions of small load disturbance, and the water flow inertia time constant T? W of such plants is large, for the power station with the pressure regulating valve, When the device, the transient feedback strength bt and buffer time constant Td and related technical parameters, to be as large as possible adjustable range. (3) Due to the different characteristics of the flow characteristics of the unit and the flow characteristics of the pressure regulating valve, it is difficult to match exactly the same, and the pressure drop often occurs during the initial closing period and the closing closing period of the guide vane. Therefore, the opening and closing laws of the pressure regulating valve and the turbine guide vane are reasonably selected , So that the entire diversion system flow changes, can reduce or avoid the pressure drop. (4) The stainless steel sealing ring can be used for the pressure regulating valve of the high-head power station to improve the sealing effect and prolong the sealing life so as to reduce the energy waste. (5) At present, the operating hydraulic pressure of most small and medium speed governors has been raised to 4 ~ 16MPa, and the computer monitoring system is also put into operation in most hydropower stations. In order to adapt to this change, the pressure regulating valve also needs to be improved accordingly (such as adding a pressure regulating valve stroke signal device to participate in the operation control of the generating unit to prevent the load increasing when the pressure regulating valve is still on).