CN104405457B - A kind of energy gradient utilization system of back pressure turbine heat supply - Google Patents

Abstract

The invention provides a kind of energy gradient utilization system of back pressure turbine heat supply, driven by Thermal generation unit extracted steam from turbine, comprise small steam turbine and small generator, connected by coupling between small steam turbine and small generator, the steam inlet of small steam turbine is communicated with steam inlet pipe, steam inlet pipe is provided with admission modulating valve, steam inlet pipe entry end is communicated with the high pressure extraction pipe of main steam turbine respectively with main steam pipe, the steam-expelling port of small steam turbine is communicated with factory steam equipment, small generator is connected with the station service electrical system of power plant by electric transmission line, also comprise regulating system, this regulating system is formed by being with single pump hydraulic speed governor and corrugated tube list sliding valve style pressure governor, described band list pump hydraulic speed governor and corrugated tube list sliding valve style pressure governor are arranged in parallel, run according to heat load for controlling back pressure turbine or run by electric load mode.

Description

An Energy Cascade Utilization System for Back Pressure Steam Turbine Heat Supply

technical field

The invention relates to an energy cascade utilization system for back-pressure steam turbine heat supply, which adopts steam extraction from the main steam turbine of the unit to drive a back-pressure small steam turbine generator set, and an energy cascade utilization device system for exhaust steam heat supply of the small steam turbine, which belongs to the coal-fired power generation technology field.

Background technique

At present, most cogeneration units use steam extraction from the main steam turbine for heat supply, and some back pressure units use exhaust steam from the main steam turbine for heat supply. The pressure and temperature parameters of the steam extracted by the main steam turbine are usually higher than the demand of heat users. It is necessary to reduce the parameters through the desuperheater and pressure reducer to supply heat users such as industrial steam or municipal heating. The desuperheater and pressurizer cause the loss of steam extraction energy of the main steam turbine, which affects the power generation efficiency of the combined heat and power unit. The pressure and temperature of the exhaust steam of the main steam turbine of the back pressure unit are relatively low, which usually cannot meet the parameter requirements of industrial steam, and can only be used for municipal heating.

The structure of the traditional back-pressure steam turbine unit belongs to the prior art. For example, a back-pressure steam turbine is disclosed in the document CN201110196Y, which includes a cylinder 7, a front bearing block 2, a rear bearing block 10, supported on the front bearing block 2, a rear The chassis 21 on the lower side of the bearing seat 10 is provided with a speed governor 1 on the front bearing seat 2, and the bearing 3 and the bearing 4 supporting the rotor 11 are installed in the front bearing seat 2, and the thermometer 5 is installed on the front bearing seat 2, and the cylinder The compound speed impeller blade 8 in 7 is installed on the rotor 11, the steam seal 9 is arranged between the cylinder 7 and the rotor 11, the exhaust pipe 6 is installed on the body of the cylinder 7, and the rotor 11 on the side of the rear bearing seat 10 is installed There is a coupling 12, and the bottom of the steam chamber of the cylinder 7 is equipped with a nozzle group 19 and a turning vane ring 20. The distance between the side of the front bearing seat 2 and the rear bearing seat 10 close to the cylinder 7 and the center of the impeller blade 8 in the cylinder 7 is 361.5cm, the inner diameter of the impeller blade 8 is 130cm, the outer diameter is 400cm, the distance between the exhaust pipe 6 on the front and rear sides of the cylinder 7 and the center of the impeller blade 8 is 291.5cm, and the front end of the cylinder 7 is provided with a main steam valve 13, emergency Breaker 16, regulating steam valve connecting rod 18, emergency breaker connecting rod 17 is set between emergency breaker 16 and main steam valve 13, steam valve seat frame 14 is set on the lower side of main steam valve 13, the steam turbine The inlet steam pressure is 2.5Mpa, the inlet steam temperature is 350°C, the exhaust steam pressure is 0.4Mpa, the power range is 75KW, the rated speed is 3000rpm/min, and the tripping speed is 3320rpm/min. The back pressure steam turbine can accurately meet the user's requirements for product power and save energy

The document CN201301734U also discloses a back pressure steam turbine, which cancels the 4-13 pressure stages of the original unit, retains the 4, 8-12 pressure stage impellers as balance weights, and sets the middle split sealing volute and the middle cylinder. At the same time, the auxiliary parts of the unit are modified accordingly. The modified back-pressure steam turbine consists of a front bearing box, a thrust support bearing, a high-pressure steam chamber, a front cylinder, a double-row regulating stage, and a second Composed of 2nd pressure stage, 3rd pressure stage, middle cylinder, middle split plugged volute, balance weight, rear cylinder, and rear bearing seat, the thrust support bearing is located in the front bearing box, and the front bearing box is connected to the high-pressure steam chamber According to the structure, it is connected with the front cylinder. The rotor between the front cylinder and the middle cylinder is designed with double-row adjustment stages, the second pressure stage, and the third pressure stage. The rear bearing seat is located in the rear cylinder. In the setting of the middle cylinder Partial plugging of the volute, back pressure exhaust port and balance weight, and the balance weight is the impeller of the 4th, 8th to 12th pressure stages of the original condensing steam turbine. The built-in back-pressure rear cylinder composed of the middle split sealing volute, rib plate and built-in steam seal reduces the steam exhaust volume, greatly reduces the loss of tail airflow, and improves the efficiency of the unit; the special line design ensures the strength of the volute. Satisfies the requirements of the steam turbine operating under various harsh working conditions while ensuring the back pressure and exhaust pressure. The flow structure of the condensing 12MW steam turbine before the transformation adopts a single cylinder structure composed of front, middle and rear sections. The flow part is composed of a double-row regulating stage and 12 pressure stages. The front cylinder is equipped with 6 high-pressure steam chambers. 50-60 to adjust the steam valve; the front bearing is a thrust support joint bearing, and the rear support bearing is an elliptical bearing. The modified flow structure of the back-pressure steam turbine includes: (1) The rotor of the steam turbine is modified, the original re-velocity stage and two pressure stages are retained, and all the pressure stage blades and impellers after the 4th to 13th stages are removed are retained as counterweights The block is used, and the front steam seal is changed from Φ445mm to Φ300 to reduce the axial thrust of the unit. (2) The front and rear cylinders remain unchanged, and the middle cylinder is modified to install a horizontal split-type sealing volute, and a new rear shaft seal is established at the volute, and a back pressure exhaust port is set; the original exhaust cylinder is still retained for use. As the supporting part of the No. 2 bearing. (3) Replace the original six regulating steam valves with diameters (φ50～60)mm with six regulating steam valves of φ70mm to increase the steam intake capacity. (4) The distance between the center of the front and rear bearings after transformation remains unchanged, and the connection method with the generator remains unchanged. In order to ensure that the basic design size of the original turbo-generator unit remains unchanged. Adjustment system: The original adjustment system remains unchanged, and the back pressure exhaust pressure protection device is added. Thermal system: (1) The design conditions of the back-pressure steam turbine and the condensing steam turbine are the same or close, and the parameters of the main steam and water supply system, and part of the heat recovery equipment system (including high-pressure heaters, high-pressure deaerators, etc.) are all changed Not big, so keep using it. (2) Install a new shaft seal heater with 2 fans (1 open and 1 standby) to establish the air system of the back pressure machine to receive the door lever, shaft seal leakage and heater exhaust air. (3) The condenser is discarded, the rubber ball cleaning and water jet pumping system are discarded, and the circulating water system is out of service (the booster circulating cooling water system to the auxiliary equipment is reserved. (4) The drainage pipeline is changed accordingly, and the The original hydrophobic expansion tank. (5) Increase the back pressure exhaust pipeline, and add a check valve and a safety valve on the back pressure pipeline. (6) Renovate the steam seal system. The diameter of the front steam seal before the transformation is 445mm, of which The first gear leaks steam to the high-pressure heater, the second gear leaks steam to the pressure equalization tank, and the third gear leaks steam to the shaft seal heater. After the transformation, the diameter of the front seal is 300mm, and the diameter of the seal is reduced to ensure that the modified unit The axial thrust is within a reasonable range. Among them, the first stage of the front steam seal leaks steam to the high-pressure heater (it remains unchanged before the transformation), and the second stage leaks steam to the newly added shaft seal heater. Due to the leakage of the back pressure machine The steam volume is large, and the pressure equalizing box of the original unit cannot meet the requirements of large steam leakage. The steam leakage of the third gear is still to the shaft seal heater (it remains unchanged from before the transformation). The steam leakage of the first gear of the built-in steam seal is increased to the new The second gear leaks to the original shaft seal heater. The original rear steam seal of the unit remains unchanged. The technology of transforming the condensing steam turbine into a back pressure steam turbine is to improve the efficiency of the unit and reduce the coal consumption. Reuse after transformation provides an effective way; while ensuring that the external structure of the unit does not change, only the flow part is modified. This provides an effective way to obtain high benefits with low cost and low investment.

The traditional main steam turbine extraction heat supply and the back pressure unit use the main steam exhaust steam heat supply to use the energy of the steam unreasonably. The pressure and temperature are too low to meet the parameter requirements of industrial steam, so it can only be used for municipal heating.

Contents of the invention

In order to solve the above technical problems, the present invention proposes an energy cascade utilization system for back pressure steam turbine heating, which is driven by steam extraction of coal-fired generator set, and designed according to the steam pressure, temperature, and flow rate of heat users. The main steam of the unit or the high-pressure extraction steam of the main turbine drives the small steam turbine generating set to generate electricity after the flow is controlled by the electric control valve. The exhaust steam of the small steam turbine meets the pressure, temperature, and flow requirements of industrial steam, and is directly supplied to industrial steam. The power generated by the small steam turbine generator set can be connected to the utility power system of the power plant to drive the auxiliary equipment of the set.

According to the first aspect of the present invention, the back pressure steam turbine heating energy cascade utilization system of the present invention includes a small steam turbine and a small generator, the small steam turbine and the small generator are connected by a coupling, and the small steam turbine The steam inlet is connected with the steam inlet pipe, and the steam inlet pipe is equipped with a steam inlet regulating valve. The inlet end of the steam inlet pipe is respectively connected with the main steam pipe and the high-pressure steam extraction pipe of the main steam turbine. Connected, the small generator is connected to the utility power system of the power plant through the transmission line.

According to the second aspect of the present invention, the energy cascade utilization system for back pressure steam turbine heat supply according to the present invention is characterized in that the back pressure steam turbine is driven by the steam extraction of the steam turbine of the coal-fired power generation unit.

According to the third aspect of the present invention, the energy cascade utilization system for back pressure steam turbine heat supply according to the present invention is characterized in that it also includes an adjustment system, the adjustment system is composed of a hydraulic governor with a single pump and a wave tube unit The spool valve pressure regulator is composed of the hydraulic governor with a single pump and the corrugated tube single spool valve pressure regulator arranged in parallel.

Since the back pressure steam turbine takes into account both power generation and heat supply (that is, steam supply to industrial steam equipment), the regulating system needs to adjust the two parameters of speed and back pressure. There is a corresponding relationship between the power generation and the heat supply, and the exhaust steam of the back pressure steam turbine has a corresponding relationship with the steam intake. If the steam supply required by industrial steam equipment increases, it is necessary to increase the steam intake of the steam turbine, so that the power generation will increase accordingly. The maximum heat supply depends on the maximum power generation, that is to say, the operation mode of the back pressure steam turbine should be adjusted according to the heat load (that is, the steam consumption required by the industrial steam equipment). At this time, the intake steam of the back pressure steam turbine The regulating valve is controlled by a corrugated tube single-slide valve pressure regulator. Since the steam consumption required by industrial steam equipment is constantly changing, it is necessary to ensure that the exhaust pressure of the back pressure steam turbine is stable within a certain range to meet the demand for steam consumption. , it is necessary to use the pressure regulator to maintain the operation mode of the heat load. Under the action of the pressure regulator, the steam intake of the steam turbine changes with the steam consumption required by the industrial steam equipment, and the power generated by the generator also changes accordingly. The steam consumption As the amount of steam increases, the amount of steam passing through the steam turbine increases, and the generating power of the generator also increases; conversely, when the amount of steam used decreases, the amount of steam passing through the steam turbine decreases, and the generating power of the generator also decreases. In this case, the electric energy generated by the generator cannot be balanced with the needs of the user at all. Usually, it should be connected to the grid for operation to synchronize the speed of the generator with the grid. Since the cycle rate of the grid is jointly maintained by the generators in the grid, relatively It is said to be relatively stable. At this time, the speed of the back pressure steam turbine does not need to be adjusted. The main task of the regulating system is to maintain the stability of the exhaust pressure.

If it is necessary to operate according to the electric load mode, the voltage regulator is in the exit state, so that the steam turbine operates under the control of the governor, so as to ensure the balance between the electric load of the utility power system and the steam intake of the steam turbine, and ensure that the speed is at the rated value, but It cannot be guaranteed that the exhaust volume of the steam turbine is balanced with the steam consumption required by the heat user.

According to the fourth aspect of the present invention, the energy cascade utilization system for back pressure steam turbine heat supply according to the present invention is characterized in that the hydraulic governor with a single pump includes a speed sensing mechanism, a transmission mechanism and a steam distribution mechanism. Mechanism; the pressure regulator is a pressure sensing mechanism, which receives the change pulse of the back pressure, and then adjusts the flow of steam entering the steam turbine according to the change of the back pressure.

According to the fifth aspect of the present invention, the energy cascade utilization system for back pressure steam turbine heat supply according to the present invention is characterized in that the rotational speed sensing mechanism is a hydraulic type, which consists of a radial drilling pump, an oil injector and a pressure The radial drilling pump converts the change of the rotating speed into the change of the outlet oil pressure, and controls the displacement of the slide valve of the pressure converter to change the pulse oil pressure; the radial drilling pump is directly driven by the main shaft of the steam turbine, and the oil injector is directed to the The inlet of the radial drilling pump supplies oil. When the steam turbine rotates, the impeller of the radial drilling pump rotates to generate centrifugal force to increase the pressure of the liquid.

According to the sixth aspect of the present invention, the energy cascade utilization system for back pressure steam turbine heat supply according to the present invention is characterized in that the oil pressure increment of the radial bore pump is proportional to the square of the rotational speed.

According to the seventh aspect of the present invention, the energy cascade utilization system for back pressure steam turbine heating according to the present invention is characterized in that the oil injector includes a nozzle, a diffuser pipe and a mixing chamber; when the radial borehole pump When the high-pressure oil is ejected from the nozzle at high speed, the oil flow in the mixing chamber is ejected from the diffuser pipe together with the high-pressure oil under the action of ejection, and a low-pressure area is formed in the mixing chamber at the same time, so that the oil is supplied to the inlet of the radial drilling pump.

According to the eighth aspect of the present invention, the energy cascade utilization system for back pressure steam turbine heat supply according to the present invention is characterized in that the pressure converter converts the oil pressure change signal of the radial bore pump into a slide valve displacement, and thereby manipulate the transfer mechanism.

According to the ninth aspect of the present invention, the energy cascade utilization system for back pressure steam turbine heat supply according to the present invention is characterized in that the steam distribution mechanism includes a steam inlet regulating valve drive mechanism for driving the steam inlet regulating valve Regulates the flow of steam into the steam turbine.

According to the tenth aspect of the present invention, the energy cascade utilization system for back pressure steam turbine heat supply according to the present invention is characterized in that the transmission mechanism receives a single-pump hydraulic governor and a corrugated tube single-slide valve type The change signal of the pressure regulator is amplified, and then the driving mechanism of the steam inlet regulating valve of the steam distribution mechanism is manipulated to drive the steam inlet regulating valve to adjust the steam flow into the steam turbine.

Description of drawings

FIG. 1 is an overall schematic diagram of the energy cascade utilization system for heat supply by a back pressure steam turbine described in the present application.

Detailed ways

As shown in Figure 1, the energy cascade utilization system for back pressure steam turbine heating according to the present invention includes a small steam turbine 2 and a small generator 4, and the small steam turbine and the small generator are connected by a coupling 3, and the small steam turbine The steam inlet of the steam inlet is connected with the steam inlet pipe, and the steam inlet regulating valve 1 is arranged on the steam inlet pipe. The steam equipment is connected, and the small generator is connected to the utility power system of the power plant through the transmission line. The small steam turbine 2 is a back pressure steam turbine.

The main steam or the high-pressure extraction steam of the main steam turbine enters the small steam turbine 2 after the flow is controlled by the steam inlet regulating valve 1 of the small steam turbine. The exhaust steam of the small steam turbine 2 is supplied with industrial steam. The small steam turbine 2 drives the small generator 4 to generate electricity through the coupling 3, and the generated energy is connected to the utility power system of the power plant.

The back-pressure steam turbine is driven by steam extraction from the steam turbine of the coal-fired generating set.

The energy cascade utilization system for back pressure steam turbine heating also includes a regulating system, which is composed of a single-pump hydraulic governor and a corrugated tube single-slide valve pressure regulator. The single-pump hydraulic The type governor is set in parallel with the corrugated tube single slide valve pressure regulator.

Since the back pressure steam turbine takes into account both power generation and heat supply (that is, steam supply to industrial steam equipment), the regulating system needs to adjust the two parameters of speed and back pressure. There is a corresponding relationship between the power generation and the heat supply, and the exhaust steam of the back pressure steam turbine has a corresponding relationship with the steam intake. If the steam supply required by industrial steam equipment increases, it is necessary to increase the steam intake of the steam turbine, so that the power generation will increase accordingly. The maximum heat supply depends on the maximum power generation, that is to say, the operation mode of the back-pressure steam turbine is adjusted according to the heat load (that is, the steam consumption required by industrial steam equipment), and the inlet steam of the back-pressure steam turbine The regulating valve is controlled by a corrugated tube single-slide valve pressure regulator. Since the steam consumption required by industrial steam equipment is constantly changing, it is necessary to ensure that the exhaust pressure of the back pressure steam turbine is stable within a certain range to meet the demand for steam consumption. , it is necessary to use the pressure regulator to maintain the operation mode of the heat load. Under the action of the pressure regulator, the steam intake of the steam turbine changes with the steam consumption required by the industrial steam equipment, and the power generated by the generator also changes accordingly. The steam consumption As the amount of steam increases, the amount of steam passing through the steam turbine increases, and the generating power of the generator also increases; conversely, when the amount of steam used decreases, the amount of steam passing through the steam turbine decreases, and the generating power of the generator also decreases. In this case, the electric energy generated by the generator cannot be balanced with the needs of the user at all. Usually, it should be connected to the grid for operation to synchronize the speed of the generator with the grid. Since the cycle rate of the grid is jointly maintained by the generators in the grid, relatively It is said to be relatively stable. At this time, the speed of the back pressure steam turbine does not need to be adjusted. The main task of the regulating system is to maintain the stability of the exhaust pressure.

If it is necessary to operate according to the electric load mode, the voltage regulator is in the exit state, so that the steam turbine operates under the control of the governor, so as to ensure the balance between the electric load of the utility power system and the steam intake of the steam turbine, and ensure that the speed is at the rated value, but It cannot be guaranteed that the exhaust volume of the steam turbine is balanced with the steam consumption required by the heat user.

The hydraulic governor with a single pump includes a speed sensing mechanism, a transmission mechanism and a steam distribution mechanism; the steam distribution mechanism includes a steam inlet regulating valve driving mechanism, which is used to drive the steam inlet regulating valve to adjust the steam flow entering the steam turbine . The pressure regulator is a pressure sensing mechanism, which receives the change pulse of the back pressure, and then adjusts the steam flow into the steam turbine according to the change of the back pressure. The pressure regulator is mainly composed of a corrugated tube, slide valve, compression spring, regulator handwheel and eccentric wheel. When the heat load increases, the back pressure decreases, the corrugated tube extends downward, and the thimble drives the slide valve to move down. When the valve moves down, it will drive the steam inlet regulating valve drive mechanism of the steam distribution mechanism, so that the steam inlet regulating valve will be opened to increase the amount of steam entering the steam turbine; when the heat load decreases, the working process is opposite to the above.

The rotational speed sensing mechanism is hydraulic and consists of a radial borehole pump, an oil injector and a pressure transducer. The radial borehole pump converts the change of rotational speed into the change of outlet oil pressure, and controls the slide valve of the pressure transducer to generate Displacement changes the pulse oil pressure; the radial drilling pump is directly driven by the main shaft of the steam turbine, and the oil injector supplies oil to the inlet of the radial drilling pump. When the steam turbine rotates, the impeller of the radial drilling pump rotates to generate centrifugal force to increase the liquid pressure. The oil pressure increment of the radial drilling pump is proportional to the square of the rotational speed. The working principle of the radial borehole pump is that when the external load decreases or increases, the speed of the steam turbine rises or falls away from the stable speed. Since the oil pressure increment of the radial borehole pump is proportional to the square of the speed, it can be used This characteristic of the pump acts as the rotational speed sensing element of the speed control system.

The oil injector includes a nozzle, a diffuser tube and a mixing chamber; when the high-pressure oil of the radial drilling pump is ejected from the nozzle at high speed, the oil flow in the mixing chamber is ejected from the diffuser pipe together with the high-pressure oil under the ejection action, At the same time, a low-pressure area is formed in the mixing chamber to supply oil to the inlet of the radial drilling pump.

The pressure converter converts the oil pressure change signal of the radial drilling pump into the displacement of the slide valve, and thereby manipulates the transmission mechanism. The transmission mechanism receives and amplifies the change signal of the single-pump hydraulic governor and the corrugated tube single-slide valve pressure regulator, and then manipulates the steam inlet regulating valve driving mechanism of the steam distribution mechanism to adjust the steam entering the steam turbine. flow.

The system approach of the present invention has been illustrated and explained with reference to schematic process diagrams. Based on the above description, additional variations and modifications will be obvious to those skilled in the art, all of which fall within the protection scope of the present application, and the protection scope of the present invention is determined by the appended claims.

Claims (6)

1. A cascaded energy utilization system for back pressure steam turbine heating, characterized in that it comprises a small steam turbine and a small generator, the small steam turbine and the small generator are connected by a coupling, the steam inlet of the small steam turbine is connected to the steam inlet The steam inlet pipe is connected with a steam inlet regulating valve, the inlet end of the steam inlet pipe is respectively connected with the main steam pipe and the high-pressure steam extraction pipe of the main steam turbine, the steam outlet of the small steam turbine is connected with industrial steam equipment, and the small generator It is connected to the utility power system of the power plant through the transmission line; The back pressure steam turbine is driven by steam extraction from the steam turbine of the coal-fired generating set; The energy cascade utilization system for back pressure steam turbine heat supply also includes a regulation system, the regulation system is composed of a single-pump hydraulic governor and a corrugated tube single-slide valve pressure regulator, and the single-pump The hydraulic governor is set in parallel with the corrugated tube single slide valve regulator; The hydraulic governor with a single pump includes a speed sensing mechanism, a transmission mechanism and a steam distribution mechanism; the pressure regulator is a pressure sensing mechanism, which receives the change pulse of the back pressure, and then adjusts the steam turbine according to the change of the back pressure. steam flow; The rotational speed sensing mechanism is hydraulic and consists of a radial borehole pump, an oil injector and a pressure transducer. The radial borehole pump converts the change of rotational speed into the change of outlet oil pressure, and controls the slide valve of the pressure transducer to generate Displacement changes the pulse oil pressure; the radial drilling pump is directly driven by the main shaft of the steam turbine, and the oil injector supplies oil to the inlet of the radial drilling pump. When the steam turbine rotates, the impeller of the radial drilling pump rotates to generate centrifugal force to increase the liquid pressure. 2. The energy cascade utilization system for back pressure steam turbine heat supply as claimed in claim 1, characterized in that the oil pressure increment of the radial bore pump is proportional to the square of the rotational speed. 3. The energy cascade utilization system of back pressure steam turbine heat supply as claimed in claim 2, wherein said oil injector comprises a nozzle, a diffuser pipe and a mixing chamber; When the nozzle is ejected at high speed, the oil flow in the mixing chamber is ejected from the diffuser pipe together with the high-pressure oil under the action of ejection, and at the same time a low-pressure area is formed in the mixing chamber, so that the oil is supplied to the inlet of the radial drilling pump. 4. The energy cascade utilization system for back pressure steam turbine heat supply as claimed in claim 1, characterized in that, the pressure transducer converts the oil pressure change signal of the radial bore pump into the displacement of the slide valve, and This actuates the transfer mechanism. 5. The energy cascade utilization system for back pressure steam turbine heat supply as claimed in claim 4, wherein said steam distribution mechanism comprises a steam inlet regulating valve drive mechanism for driving the steam inlet regulating valve to adjust the steam entering the steam turbine. steam flow. 6. The energy cascade utilization system for back pressure steam turbine heat supply as claimed in claim 5, wherein the transmission mechanism receives a single-pump hydraulic governor and a corrugated tube single-slide valve pressure regulator. The signal is changed and amplified, and then the driving mechanism of the steam inlet regulating valve of the steam distribution mechanism is manipulated to drive the steam inlet regulating valve to adjust the steam flow entering the steam turbine.