Steam turbine generator unit

Abstract

The steam turbine generator unit comprises a boiler, a front steam turbine and a main steam turbine, the main steam turbine comprises a high-pressure cylinder, an intermediate-pressure cylinder, a low-pressure cylinder and an intermediate-low pressure combined cylinder which are arranged on a main shaft of the main steam turbine at the same time, and the main shaft of the main steam turbine is connected with a first generator; the front steam turbine is connected with a second generator, a steam exhaust port of the front steam turbine is connected with a steam inlet of the high-pressure cylinder through a first interstage pipeline, and an exhaust port of the intermediate-pressure cylinder is connected with a steam inlet of the low-pressure cylinder through a second interstage pipeline; the boiler is connected with the front steam turbine and the high-pressure cylinder through a main steam pipeline, and the boiler is connected with the medium-pressure cylinder and the medium-low pressure combined cylinder through a reheat steam pipeline. The front steam turbine has the working mode of running in series with the main steam turbine or running in parallel with the main steam turbine. The running efficiency of the medium-pressure cylinder and the low-pressure cylinder is improved, and therefore the energy utilization rate of steam is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of power generation equipment, and in particular to a steam turbine generator set. Background Art

[0002] Power generation from coal-fired power plants is a complex energy conversion process involving the interconversion of multiple energy forms. A steam turbine generator system primarily consists of a boiler, steam turbine, generator, and auxiliary systems. In the boiler, coal is fed into the combustion chamber and burned, releasing a large amount of heat energy. The feedwater in the boiler is heated and evaporated by the heating surfaces, forming high-temperature, high-pressure steam. Once the steam enters the turbine, it rotates the blades at each stage, converting the thermal energy into mechanical energy. The mechanical energy output by the turbine is converted into electrical energy by the generator and output via transmission lines.

[0003] Steam turbine cylinders can be divided into high-pressure, intermediate-pressure, and low-pressure cylinders based on the steam inlet parameters. The high-pressure cylinder, located at the front of the turbine, is the initial stage where the main steam enters the cylinder. Exhaust steam from the high-pressure cylinder enters the boiler reheater for heating before entering the intermediate-pressure cylinder to perform work. The intermediate-pressure cylinder exhaust steam then enters the low-pressure cylinder. Exhaust steam from the low-pressure cylinder enters the condenser, condenses into water, and enters the heat recovery system.

[0004] Existing units are typically built with maximum power generation as the goal. Therefore, the design of the turbine's intermediate and low-pressure cylinders is typically based on rated operating conditions to ensure maximum turbine efficiency at rated conditions and guarantee the unit's power generation. However, with the development of new energy sources and the construction of new power systems, coal-fired power is gradually shifting towards regulating and supporting power sources. Large-capacity supercritical units generally operate at medium to low loads, unable to fully utilize their advantages of high efficiency at rated load.

[0005] However, in existing steam turbine units, the intermediate and low-pressure cylinders are designed for rated operating conditions, resulting in a significant decrease in efficiency at low and medium loads. This lack of high efficiency across a wide load range significantly reduces the turbine's operating efficiency. Therefore, a redesign of the structure of the intermediate and low-pressure cylinders is necessary to improve their efficiency at low and medium loads.

[0006] Currently, the technology of combining medium and low pressure cylinders is a key research direction in steam turbine design. This type of turbine, unlike turbines with separate high and low pressure cylinders, eliminates the connecting pipe between the medium and low pressure cylinders, resulting in higher efficiency and improved safety and reliability. It is primarily used in combined cycle units and thermal power generation unit retrofits to improve efficiency, flexibility, and peak-shaving capabilities. However, current medium and low pressure combined cylinder technology is primarily used to replace the original separate medium and low pressure cylinders. Therefore, the medium and low pressure combined cylinders are still designed to match rated operating conditions, and therefore cannot solve the problem of low efficiency of steam turbine generator sets under medium and low load conditions. Summary of the Invention

[0007] The purpose of the present invention is to solve the deficiencies in the prior art and to provide a steam turbine generator set.

[0008] The present invention discloses a steam turbine generator set, comprising a boiler, a pre-installed steam turbine and a main steam turbine. The main steam turbine comprises a high-pressure cylinder, an intermediate-pressure cylinder, a low-pressure cylinder and an intermediate-low-pressure combined cylinder which are simultaneously arranged on the main shaft of the main steam turbine. The main shaft of the main steam turbine is connected to a first generator. The pre-installed steam turbine is connected to a second generator. The exhaust port of the pre-installed steam turbine is connected to the steam inlet of the high-pressure cylinder via a first inter-stage pipeline, and the exhaust port of the intermediate-pressure cylinder is connected to the steam inlet of the low-pressure cylinder via a second inter-stage pipeline. The boiler is connected to the pre-installed steam turbine and the high-pressure cylinder via a main steam pipeline, and is connected to the intermediate-pressure cylinder and the intermediate-low-pressure combined cylinder via a reheat steam pipeline. The pre-installed steam turbine has a working mode of operating in series with the main steam turbine or in parallel with the main steam turbine.

[0009] Preferably, the medium- and low-pressure combined cylinder includes a medium-pressure cylinder body and a low-pressure cylinder body that are interconnected and arranged in series. The medium-pressure cylinder body and the low-pressure cylinder body constitute an integral cylinder body component. Medium-pressure flow stator blades and low-pressure flow stator blades are arranged inside the cylinder body component. The medium-pressure flow stator blades and the low-pressure flow stator blades are coaxially arranged. The medium-pressure flow stator blades are located in a cavity inside the medium-pressure cylinder body, and the low-pressure flow stator blades are located in a cavity inside the low-pressure cylinder body. A steam inlet and a steam exhaust port are provided on the cylinder body component, and the steam inlet and the steam exhaust port are respectively located at both ends of the cylinder body component.

[0010] Preferably, the main steam pipeline includes a first main steam pipeline and a second main steam pipeline, the first main steam pipeline connects the boiler and the pre-installed steam turbine, the second main steam pipeline connects the boiler and the high-pressure cylinder, and a first valve is provided on the first main steam pipeline; a second valve is provided on the second main steam pipeline; a third valve is provided on the first interstage pipeline; the reheat steam pipeline includes a first reheat pipeline and a second reheat pipeline, the first reheat steam pipeline connects the boiler and the medium-pressure cylinder, the second reheat steam pipeline connects the boiler and the medium- and low-pressure combined cylinder; a sixth valve is provided on the second reheat steam pipeline.

[0011] Preferably, the front steam turbine, high-pressure cylinder and medium-pressure cylinder are respectively connected to the high-pressure heating reflux system through a high-pressure heating circuit, and a fifth valve and a condenser branch are provided on the high-pressure heating circuit connected to the front steam turbine, and a fourth valve is provided on the condenser branch; the condenser branch, the exhaust port of the low-pressure cylinder and the exhaust port of the medium and low-pressure combined cylinder are all connected to the condenser, and the condenser is connected to the low-pressure heating reflux system; the low-pressure heating reflux system is connected to the high-pressure heating reflux system; the exhaust steam of the low-pressure cylinder and the medium and low-pressure combined cylinder passes through the condenser, the low-pressure heating reflux system and the high-pressure heating reflux system in turn to form reheated steam and return to the boiler; the exhaust steam of the front steam turbine, high-pressure cylinder and medium-pressure cylinder passes through the high-pressure heating reflux system to form reheated steam and return to the boiler.

[0012] Preferably, when the second valve and the fourth valve are closed and the first valve and the third valve are opened, the pre-turbine and the main steam turbine operate in series; when the first valve, the second valve and the third valve are opened and the fourth valve is closed, the pre-turbine and the main steam turbine operate in parallel.

[0013] Preferably, the operation method of the steam turbine generator set is as follows: Set the zero output load operating point of the medium and low pressure combined cylinders and the load operating point of the front steam turbine; When the steam turbine generator set is in the operating condition between the rated load condition and the load condition point of the front steam turbine, the first valve, the third valve, the fourth valve, and the fifth valve are closed, and the second valve and the sixth valve are opened; the front steam turbine is not put into operation, and the high-pressure cylinder, the intermediate-pressure cylinder, the low-pressure cylinder, and the intermediate-low-pressure combined cylinder are put into operation; When the steam turbine generator set is at the load condition point of the front steam turbine or at a condition between the load condition point of the front steam turbine and the zero output load condition point of the medium and low pressure cylinders, the first valve, the third valve and the fifth valve are closed, the second valve and the fourth valve are opened, the front steam turbine is put into operation, and the opening of the sixth valve is adjusted so that the reheated steam enters the medium pressure cylinder and the low pressure cylinder first through the reheated steam pipeline; When the steam turbine generator set is in the medium and low pressure combined cylinder zero output load operating point or the operating condition below the medium and low pressure combined cylinder zero output load operating point, the first valve, the third valve and the fifth valve are closed, the second valve and the fourth valve are opened, the front steam turbine is put into operation, and the opening of the sixth valve is adjusted to switch the medium and low pressure combined cylinder to the zero output state.

[0014] Preferably, the ratio A of the medium and low pressure combined cylinder zero output load operating point to the rated load operating condition is calculated by the following formula: A=S1 / (S1+S2); Where, S1 is the sum of the flow areas of the medium-pressure cylinder and the low-pressure cylinder, which is the first flow area; S2 is the flow area of the medium- and low-pressure combined cylinder, which is the second flow area; The ratio B of the pre-turbine load condition point to the rated load condition is calculated by the following formula: B=S3 / (S3+S4); Where S3 is the total flow area of the high-pressure cylinder, intermediate-pressure cylinder, low-pressure cylinder, and intermediate- and low-pressure combined cylinder, and S4 is the flow area of the front steam turbine.

[0015] Preferably, the flow area of the front steam turbine is smaller than the flow area of the high-pressure cylinder.

[0016] As a preferred embodiment, in an accident condition, the fourth valve is opened and the remaining valves are closed, and the exhaust steam of the front steam turbine all enters the condenser; in a low-load condition, the fifth valve is opened, and the exhaust steam of the front steam turbine is used as a supplementary heating steam source for the high-pressure heating reflux system to increase the feed water temperature.

[0017] The beneficial effects of the present invention are: 1. The pre-installed steam turbine has the working modes of running in series or in parallel with the main steam turbine. Under low and medium loads, the pre-installed steam turbine can pre-work through the series operation mode, thereby improving the energy utilization rate of the main steam turbine's inlet steam and avoiding the efficiency degradation of the main steam turbine due to load reduction. Under high load conditions, the steam flow rate can be increased through the parallel operation mode, and the total power generation can be increased through the coordinated power generation of the dual generators. At the same time, the pre-installed steam turbine can divert part of the steam to reduce the load pressure of the high-pressure cylinder of the main steam turbine.

[0018] 2. Based on the existing steam turbine unit, the present invention creatively adds the structure of medium and low pressure combined cylinder, forming two sets of parallel cylinder structures: medium pressure cylinder + low pressure cylinder and medium and low pressure combined cylinder. The two sets of cylinder structures can work in parallel. In traditional steam turbine units, the single steam flow path (flow from medium pressure cylinder to low pressure cylinder) under medium and low load conditions will lead to "excess" flow area due to the reduction of steam flow, which is easy to cause vortex, steam leakage and other losses. This improvement in the present invention can divert steam to two groups of cylinders: one part of the steam flows to the low-pressure cylinder after passing through the medium-pressure cylinder to perform normal work; the other part of the steam directly enters the medium- and low-pressure combined cylinder (whose flow area is optimized according to medium and low loads), avoiding efficiency degradation caused by insufficient flow in a single passage; under high load conditions: two groups of cylinders receive steam at the same time, increasing the flow capacity and improving the total work; under medium and low loads: the steam distribution ratio can be adjusted by a valve to allow more steam to enter the medium- and low-pressure combined cylinder (whose design is more suitable for low-flow conditions), avoiding "throttling losses" caused by load reduction of the main steam turbine, and can reduce coal consumption under medium and low load conditions of the unit, with wide load and high efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a schematic diagram of the system structure of Example 1 of the present invention.

[0020] Figure 2 This is a schematic diagram of the system structure of Example 2 of the present invention.

[0021] Figure 3 This is a schematic diagram of the system structure of Example 3 of the present invention.

[0022] In the figure: 1. Boiler, 2. Pre-turbine, 3. High-pressure cylinder, 4. Medium-pressure cylinder, 5. Low-pressure cylinder, 6. Combined medium- and low-pressure cylinder, 7. First generator, 8. Second generator, 9. Main turbine shaft, 10. First valve, 11. Second valve, 12. Third valve, 13. Fourth valve, 14. Fifth valve, 16. High-pressure heating return system, 17. Low-pressure heating return system, 18. Condenser branch, 19. Clutch, 20. Heating pipeline. DETAILED DESCRIPTION

[0023] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention are within the scope of protection of the present invention.

[0024] It should be understood by those skilled in the art that, in the disclosure of the present invention, the terms "longitudinal", "transverse", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, which are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, the above terms should not be understood as limiting the present invention.

[0025] It is to be understood that the term "one" should be understood as "at least one" or "one or more", that is, in one embodiment, the number of an element may be one, while in another embodiment, the number of the elements may be multiple, and the term "one" should not be understood as a limitation on the quantity.

[0026] Example 1: like Figure 1 As shown, a steam turbine generator set includes a boiler 1, a pre-steam turbine 2, and a main steam turbine. The main steam turbine includes a high-pressure cylinder 3, an intermediate-pressure cylinder 4, a low-pressure cylinder 5, and an intermediate-low-pressure combined cylinder 6 arranged simultaneously on the main steam turbine main shaft 9. The main steam turbine main shaft 9 is connected to a first generator 7; the pre-steam turbine 2 is connected to a second generator 8, the exhaust port of the pre-steam turbine 2 is connected to the steam inlet of the high-pressure cylinder 3 via a first inter-stage pipeline, and the exhaust port of the intermediate-pressure cylinder 4 is connected to the steam inlet of the low-pressure cylinder 5 via a second inter-stage pipeline; the boiler 1 is connected to the pre-steam turbine 2 and the high-pressure cylinder 3 via a main steam pipeline, and the boiler 1 is connected to the intermediate-pressure cylinder 4 and the intermediate-low-pressure combined cylinder 6 via a reheat steam pipeline; the pre-steam turbine 2 has a working mode of operating in series with the main steam turbine or in parallel with the main steam turbine.

[0027] The boiler 1 of the present invention supplies steam to both the pre-stage steam turbine 2 and the high-pressure cylinder 3 via the main steam pipeline. The reheat steam pipeline is connected to the intermediate-pressure cylinder 4 and the combined intermediate- and low-pressure cylinder 6. Exhaust steam from the pre-stage steam turbine 2 enters the high-pressure cylinder 3 via the first interstage pipeline, while exhaust steam from the intermediate- and low-pressure cylinder 4 enters the low-pressure cylinder 5 via the second interstage pipeline. The high-pressure cylinder 3, intermediate- and low-pressure cylinder 4, low-pressure cylinder 5, and combined intermediate- and low-pressure cylinder 6 are arranged in series on the main turbine shaft 9 and connected to a first generator 7. The pre-stage steam turbine 2 is independently connected to a second generator 8.

[0028] The pre-turbine 2 can operate in series or in parallel with the main turbine, with the switching between these modes controlled by valves installed in the pipeline. In the series mode, the main steam enters the pre-turbine 2 first, rotating its blades and driving the second generator 8 to generate electricity. After passing through the pre-turbine 2, the exhaust steam (still at relatively high parameters) enters the high-pressure cylinder 3 through the first interstage pipeline, continuing to participate in the energy conversion process of the main turbine. At low and medium loads, the series operation of the pre-turbine 2 allows the pre-turbine 2 to pre-process work, improving the energy utilization of the main turbine's inlet steam and preventing the main turbine's efficiency degradation caused by reduced load. In the parallel mode, the main steam supplies steam to both the pre-turbine 2 and the high-pressure cylinder 3 simultaneously, with both performing work in parallel: the pre-turbine 2 drives the second generator 8 to generate electricity, while the high-pressure cylinder 3 drives the main turbine shaft 9 and the first generator 7 according to the traditional process. Under high load conditions, the steam flow is increased by operating in parallel mode, and the total power generation is increased through the coordinated power generation of the dual generators. At the same time, the front steam turbine 2 can divert part of the steam to reduce the load pressure of the high-pressure cylinder 3 of the main steam turbine.

[0029] The series operation mode of the present invention is suitable for medium and low load peak regulation. The steam inlet volume and parameters of the main steam turbine are flexibly adjusted by the front steam turbine 2 to avoid efficiency losses caused by frequent start and stop of the unit or deep load reduction. The parallel mode is suitable for high load or base load operation. The power generation capacity is improved by the parallel steam supply of the dual steam turbines to adapt to the load fluctuation requirements of the power grid. In the prior art, the medium and low pressure cylinders 5 are designed according to the rated operating conditions. At medium and low loads, the steam parameters deviate from the design values, resulting in a significant decrease in efficiency in the turbine. When the front steam turbine 2 of the present invention is operated in series, the "front steam turbine 2 works + main steam turbine reuse" mode is used to make the main steam turbine steam inlet parameters closer to the design conditions, thereby reducing energy losses.

[0030] Building upon existing steam turbine units, this invention creatively adds a combined intermediate and low-pressure cylinder 6, creating two parallel cylinder structures: the intermediate-pressure cylinder 4 and the low-pressure cylinder 5, and the combined intermediate and low-pressure cylinder 6. These two cylinder structures can operate in parallel. The combined intermediate and low-pressure cylinder 6 eliminates the traditional connecting pipe between the intermediate and low-pressure cylinders, reducing steam flow resistance and heat loss. The structure of the combined intermediate and low-pressure cylinder 6 is optimized for medium and low-load operating conditions (e.g., by adjusting the number of blade stages and flow area), further improving the turbine's operating efficiency under off-rated conditions.

[0031] The two cylinder groups can be adjusted during the design phase based on actual conditions. The ratio of the flow area of the combined intermediate- and low-pressure cylinder 6 to the combined flow areas of the intermediate- and low-pressure cylinders 4 and 5 can be set to 4:6, 5:5, 3:7, 2:8, 1:9, and other ratios, depending on actual needs. The flow area of the combined intermediate- and low-pressure cylinder 6 is smaller than the combined flow areas of the other intermediate- and low-pressure cylinders 5 to facilitate switching the combined intermediate- and low-pressure cylinder 6 to a low- or zero-output state. The combined structure of the two cylinder groups can meet the steam intake requirements for rated operating conditions. The ratio of the intermediate- and low-pressure cylinders to the combined intermediate- and low-pressure cylinder 6 can be used to determine the load point at which the combined intermediate- and low-pressure cylinder 6 switches to a zero-output state.

[0032] In traditional steam turbine units, the single steam flow path (from the intermediate-pressure cylinder 4 to the low-pressure cylinder 5) results in an "excess" flow area under low- and medium-load conditions due to reduced steam flow, which can easily lead to losses such as eddy currents and steam leakage. This improvement in the present invention splits the steam flow into two groups of cylinders: one portion flows through the intermediate-pressure cylinder 4 to the low-pressure cylinder 5 for normal work; the other portion directly enters the combined intermediate- and low-pressure cylinder 6 (whose flow area is optimized for low- and medium-load conditions), avoiding the efficiency loss caused by insufficient flow in a single path. Under high-load conditions, both groups of cylinders receive steam simultaneously, increasing flow capacity and total work output. Under low- and medium-load conditions, the steam distribution ratio can be adjusted using a valve to allow more steam to enter the combined intermediate- and low-pressure cylinder 6 (which is designed to better suit low-flow conditions), avoiding "throttling losses" caused by reduced load in the main steam turbine. This reduces coal consumption in low- and medium-load conditions and offers high efficiency over a wide load range.

[0033] The combined medium- and low-pressure cylinder 6 includes an intermediate-pressure cylinder 4 and a low-pressure cylinder 5, which are interconnected and arranged in series. The intermediate-pressure cylinder 4 and the low-pressure cylinder 5 form a single, integrated cylinder component. The cylinder component is internally provided with intermediate-pressure flow stator blades and low-pressure flow stator blades. The intermediate-pressure flow stator blades and the low-pressure flow stator blades are coaxially arranged. The intermediate-pressure flow stator blades are located within a cavity within the intermediate-pressure cylinder 4, while the low-pressure flow stator blades are located within a cavity within the low-pressure cylinder 5. The cylinder component is provided with a steam inlet and a steam exhaust port, with the steam inlet and exhaust ports located at either end of the cylinder component. The combined medium- and low-pressure cylinder 6 does not have a regenerative steam extraction port, and has only one steam inlet and exhaust port. Furthermore, no connecting pipe or butterfly valve is provided between the intermediate- and low-pressure cylinders 4 and 5. The steam inlet and exhaust ports are located at either end of the cylinder component, and steam flows continuously from one end of the cylinder component to the other before being discharged. The medium-pressure cylinder 4 and the low-pressure cylinder 5 are connected in series. The steam does not need to pass through the medium- and low-pressure connecting pipes in the traditional separate cylinder structure, and the expansion and work process from medium pressure to low pressure is completed directly inside the cylinder. The elimination of independent connecting pipes in the medium- and low-pressure combined cylinder 6 can eliminate the resistance along the pipeline, local resistance (such as elbows and valves), and eddy current loss, allowing the steam energy to act more directly on the blades to work. The combined cylinder design can reduce this part of the loss and improve the thermal efficiency of the unit. The cylinder components are cast in one piece, and the material can be selected from chromium-molybdenum-vanadium steel, etc. The one-piece cylinder structure has a more uniform temperature field distribution, avoiding thermal deformation of the separate cylinder structure caused by the temperature difference of the flange.

[0034] The main steam pipeline includes a first main steam pipeline and a second main steam pipeline. The first main steam pipeline connects boiler 1 with pre-turbine 2, and the second main steam pipeline connects boiler 1 with high-pressure cylinder 3. A first valve 10 is installed on the first main steam pipeline; a second valve 11 is installed on the second main steam pipeline; and a third valve 12 is installed on the first interstage pipeline. The reheat steam pipeline includes a first reheat pipeline and a second reheat pipeline. The first reheat steam pipeline connects boiler 1 with intermediate-pressure cylinder 4, and the second reheat steam pipeline connects boiler 1 with the combined intermediate- and low-pressure cylinder 6. A sixth valve is installed on the second reheat steam pipeline. The combined control of these valves switches the operating state of each cylinder.

[0035] The pre-turbine 2, high-pressure cylinder 3, and intermediate-pressure cylinder 4 are each connected to a high-pressure heating and return system 16 via a high-pressure heating circuit. The high-pressure heating circuit connected to the pre-turbine 2 is equipped with a fifth valve 14 and a condenser branch. The condenser branch is equipped with a fourth valve 13. The condenser branch, the exhaust port of the low-pressure cylinder 5, and the exhaust port of the combined intermediate- and low-pressure cylinder 6 are all connected to the condenser, which is connected to a low-pressure heating and return system 17. The low-pressure heating and return system 17 is connected to the high-pressure heating and return system 16. The exhaust steam from the low-pressure cylinder 5 and the combined intermediate- and low-pressure cylinder 6 passes through the condenser, the low-pressure heating and return system 17, and the high-pressure heating and return system 16 in sequence, forming reheated steam that is returned to the boiler 1. The exhaust steam from the pre-turbine 2, high-pressure cylinder 3, and intermediate-pressure cylinder 4 passes through the high-pressure heating and return system 16, forming reheated steam that is returned to the boiler 1. Furthermore, the low-pressure cylinder 5 is equipped with an exhaust port, which is connected to the low-pressure heating and return system 17 via a pipeline.

[0036] In the present invention, the steam circulation and heat recovery system includes two major parts: a high-pressure heating and reflow system 16 and a low-pressure heating and reflow system 17. The exhaust steam from the front steam turbine 2, the high-pressure cylinder 3, and the medium-pressure cylinder 4 enters the high-pressure heating and reflow system 16 through the high-pressure heating circuit, where the steam releases heat to heat the feed water, and after cooling itself, forms reheated steam that returns to the boiler 1, completing the heat recovery of the high-pressure section. The exhaust steam (exhaust steam) from the low-pressure cylinder 5 and the medium- and low-pressure combined cylinder 6 enters the condenser and condenses into water, and passes through the low-pressure heating and reflow system 17 and the high-pressure heating and reflow system 16 in turn, and is heated step by step to form reheated steam that returns to the boiler 1; in addition, the exhaust port of the low-pressure cylinder 5 introduces part of the steam into the low-pressure heating and reflow system 17, which is used to heat the condensed water and improve the heat recovery efficiency.

[0037] A fifth valve 14 and a condenser branch are installed on the high-pressure heating circuit of the pre-turbine 2. When the unit is operating at low or medium load, the fourth valve 13 can be opened, allowing some steam to flow directly into the condenser via the condenser branch, reducing the amount of steam entering the high-pressure heating return system 16. This reduces the work load of the pre-turbine 2 and the high-pressure cylinder 3 and achieves flow regulation. At high load, the fourth valve 13 is closed, allowing all steam to flow through the high-pressure heating circuit, ensuring full energy utilization.

[0038] When the second valve 11 and the fourth valve 13 are closed and the first valve 10 and the third valve 12 are opened, the pre-turbine 2 operates in series with the main steam turbine; when the first valve 10, the second valve 11 and the third valve 12 are opened and the fourth valve 13 is closed, the pre-turbine 2 operates in parallel with the main steam turbine.

[0039] The flow area of the pre-turbine 2 is smaller than the flow area of the high-pressure cylinder 3 .

[0040] The operation method of the steam turbine generator set is as follows: Set the zero output load operating point of the medium and low pressure combined cylinders and the load operating point of the front steam turbine; When the steam turbine generator set is operating at a load condition between the rated load and the load condition at which the pre-turbine is put into operation, the first valve 10, third valve 12, fourth valve 13, and fifth valve 14 are closed, while the second valve 11 and sixth valve are open. Pre-turbine 2 is not in operation, and the high-pressure cylinder 3, intermediate-pressure cylinder 4, low-pressure cylinder 5, and combined intermediate- and low-pressure cylinder 6 are in operation. Under this operating condition, the sixth valve is fully open and can meet the steam inlet requirements of the intermediate and low-pressure cylinders at rated load. Under this operating condition, the sixth valve is dynamically adjusted as the operating conditions change. As the steam load decreases, the opening of the sixth valve is adjusted to reduce the steam inlet to the combined intermediate- and low-pressure cylinder 6, allowing reheated steam to enter the intermediate- and low-pressure cylinders 4 and 5 preferentially, ensuring that the reheated steam entering the intermediate- and low-pressure cylinders 4 and 5 meets the design value.

[0041] When the steam turbine generator set is in the operating condition of the pre-turbine load operation point or between the pre-turbine load operation point and the medium and low pressure combined cylinder zero output load operation point, the first valve 10, the third valve 12 and the fifth valve 14 are closed, the second valve 11 and the fourth valve 13 are opened, the pre-turbine 2 is put into operation, and the opening of the sixth valve is adjusted so that the reheated steam enters the medium pressure cylinder 4 and the low pressure cylinder 5 through the reheated steam pipeline in priority; under this operating condition, since the flow area of the pre-turbine 2 is relatively small (the flow area of the pre-turbine 2 in the present invention is smaller than the flow area of the high pressure cylinder 3), compared with the main steam directly entering the high pressure cylinder 3, the main steam entering the pre-turbine 2 can increase the main steam pressure by holding the pressure, and the exhaust pressure after the main steam enters the pre-turbine 2 to do work is the same as the main steam pressure entering the high pressure cylinder 3 of the original thermal system, so the steam entering the high pressure cylinder 3 does not change, and has little effect on the high pressure cylinder 3. For example, the main steam pressure of the original thermal system at 70% load is 22 MPa. By holding the pressure in the pre-steam turbine 2, the main steam pressure can be increased to the rated main steam pressure of 28 MPa. Therefore, the main steam pressure entering the pre-steam turbine 2 is 28 MPa, and the exhaust pressure of the pre-steam turbine 2 is the original main steam pressure of 22 MPa, and enters the high-pressure cylinder 3; for the high-pressure cylinder 3, under the current load condition, the inlet steam pressure of the original thermal system and the thermal system of the present invention is both 22 MPa, and the inlet steam flow rate does not change much (the only difference from the original thermal system is a small part of the steam entering the newly added heater), so the high-pressure cylinder 3 does not need to be designed separately.

[0042] When the steam turbine generator set is at or below the zero-output load point of the medium- and low-pressure combined cylinders, the first valve 10, the third valve 12, and the fifth valve 14 are closed, the second valve 11 and the fourth valve 13 are opened, the pre-turbine 2 is put into operation, and the opening of the sixth valve is adjusted to switch the medium- and low-pressure combined cylinder 6 to a zero-output state. Under this operating condition, the sixth regulating valve switches the medium- and low-pressure combined cylinder 6 to a low-output or zero-output state. While ensuring the minimum steam inlet flow rate of the medium- and low-pressure combined cylinder 6, the remaining reheated steam enters the intermediate pressure cylinder 4 and then the low pressure cylinder 5. It is worth mentioning that the zero-output state of the medium- and low-pressure combined cylinder 6 refers to an operating state in which, during the operation of the steam turbine generator set, the steam flow direction and flow rate are adjusted to ensure that the medium- and low-pressure combined cylinder 6 reaches the minimum designed air intake, so that the steam inside the medium- and low-pressure combined cylinder 6 does not participate in work and its main shaft does not output mechanical energy (i.e., it does not contribute power to the generator). When necessary, the fourth valve 13 can be opened to transport excess steam from the pre-turbine 2 to the condenser.

[0043] By designing the flow area of the pre-mounted steam turbine 2 and varying the ratios of the intermediate and low-pressure cylinders 5 to the intermediate and low-pressure combined cylinder 6, the steam turbine unit can operate in different modes under varying load conditions. After the pre-mounted steam turbine 2 is commissioned, the main steam pressure parameters can be increased by holding back the pressure, thereby improving the thermal system cycle efficiency, thereby increasing unit efficiency and reducing coal consumption. Heating the feedwater with the exhaust steam from the pre-mounted steam turbine 2 can increase the feedwater temperature, thereby reducing unit coal consumption. By switching the intermediate and low-pressure combined cylinder 6 to a low-output or zero-output state, the steam inlet to the intermediate and low-pressure cylinders 5 can be aligned with their design values, thereby improving the efficiency of the intermediate and low-pressure cylinders, thereby improving unit efficiency and reducing unit coal consumption.

[0044] During an accident condition, the fourth valve 13 is opened and the remaining valves are closed, and the exhaust steam of the pre-installed steam turbine 2 all enters the condenser; during a low-load condition, the fifth valve 14 is opened, and the exhaust steam of the pre-installed steam turbine 2 is used as a supplementary heating steam source for the high-pressure heating return system 16 to increase the feed water temperature.

[0045] The ratio A of the zero-output load operating point of the medium and low-pressure combined cylinder to the rated load operating point is calculated using the following formula: A=S1 / (S1+S2); Where, S1 is the sum of the flow areas of the medium-pressure cylinder and the low-pressure cylinder, which is the first flow area; S2 is the flow area of the medium- and low-pressure combined cylinder, which is the second flow area; The ratio B of the pre-turbine load condition point to the rated load condition is calculated by the following formula: B=S3 / (S3+S4); Where S3 is the total flow area of the high-pressure cylinder, intermediate-pressure cylinder, low-pressure cylinder, and intermediate- and low-pressure combined cylinder, and S4 is the flow area of the front steam turbine.

[0046] This invention uses flow area as a benchmark to determine the load switching point, directly linking the switching logic to the equipment's actual flow capacity, thereby precisely defining the zero-output switching load point. Flow area is positively correlated with steam flow. Using the aforementioned formula, this invention determines the zero-output load operating point for the combined intermediate and low-pressure cylinders, as well as the load operating point for the pre-turbine, quantifying the steam-carrying capacity of both the "intermediate pressure cylinder + low-pressure cylinder" and the "combined intermediate and low-pressure cylinder" system.

[0047] Taking the ratio of the sum of the flow areas of the medium-pressure cylinder and the low-pressure cylinder to the flow area of the medium- and low-pressure combined cylinder as 6:4 as an example, the zero-output load operating point of the medium- and low-pressure combined cylinder is 60% of the rated load.

[0048] The load operating point of the front steam turbine can be set to 95% rated load, 90% rated load, 85% rated load, 80% rated load, etc.

[0049] Example 2: like Figure 2 As shown, Example 2 differs from Example 1 in that, in Example 2, the main steam turbine main shaft is connected to the pre-turbine main shaft via a clutch 19, and the main steam turbine main shaft and the pre-turbine main shaft are coaxially arranged. The second generator connected to the pre-turbine is eliminated. The clutch 19 is used to connect and disconnect the main steam turbine main shaft 9. When the pre-turbine is in operation, the clutch connects the pre-turbine to the main steam turbine, allowing them to operate coaxially. When the pre-turbine is not in operation, the clutch disconnects the pre-turbine from the main steam turbine main shaft.

[0050] The remaining structures of Example 2 are the same as those of Example 1.

[0051] Example 3: like Figure 3 As shown, the difference between Example 3 and Example 1 is that in Example 3, a heating pipe 20 is connected to the exhaust port of the pre-turbine. Due to the high exhaust pressure parameter of the pre-turbine, the steam exhausted by the pre-turbine can be supplied to the cogeneration unit through the heating pipe 20, thereby meeting the high-pressure industrial steam supply demand of the cogeneration unit and achieving heat supply. A valve is installed on the heating pipe to control the flow rate of the heating pipe.

[0052] The present invention is not limited to the above-mentioned optimal implementation mode. Anyone can derive other forms of products under the inspiration of the present invention. However, no matter what changes are made in the shape or structure, any technical solution that is the same or similar to that of the present application falls within the scope of protection of the present invention.

Claims

1. A steam turbine generator set, characterized in that: It includes a boiler, a front steam turbine and a main steam turbine. The main steam turbine includes a high-pressure cylinder, an intermediate-pressure cylinder, a low-pressure cylinder and an intermediate-low-pressure combined cylinder arranged simultaneously on the main shaft of the main steam turbine. The main shaft of the main steam turbine is connected to the first generator; the front steam turbine is connected to the second generator, the exhaust port of the front steam turbine and the steam inlet of the high-pressure cylinder are connected through the first inter-stage pipeline, and the exhaust port of the intermediate-pressure cylinder and the steam inlet of the low-pressure cylinder are connected through the second inter-stage pipeline; the boiler is connected to the front steam turbine and the high-pressure cylinder through the main steam pipeline, and the boiler is connected to the intermediate-pressure cylinder and the intermediate-low-pressure combined cylinder through the reheat steam pipeline; the front steam turbine has a working mode of running in series with the main steam turbine or in parallel with the main steam turbine.

2. A steam turbine generator set according to claim 1, characterized in that: The medium- and low-pressure combined cylinder includes a medium-pressure cylinder body and a low-pressure cylinder body that are interconnected and arranged in series. The medium-pressure cylinder body and the low-pressure cylinder body constitute an integral cylinder body component. Medium-pressure flow stator blades and low-pressure flow stator blades are arranged inside the cylinder body component. The medium-pressure flow stator blades and the low-pressure flow stator blades are coaxially arranged. The medium-pressure flow stator blades are located in a cavity inside the medium-pressure cylinder body, and the low-pressure flow stator blades are located in a cavity inside the low-pressure cylinder body. A steam inlet and a steam exhaust port are provided on the cylinder body component, and the steam inlet and the exhaust port are respectively located at both ends of the cylinder body component.

3. The steam turbine generator set according to claim 1, characterized in that: The main steam pipeline includes a first main steam pipeline and a second main steam pipeline. The first main steam pipeline connects the boiler and the pre-installed steam turbine, and the second main steam pipeline connects the boiler and the high-pressure cylinder. A first valve is provided on the first main steam pipeline; a second valve is provided on the second main steam pipeline; a third valve is provided on the first interstage pipeline; the reheat steam pipeline includes a first reheat pipeline and a second reheat pipeline. The first reheat steam pipeline connects the boiler and the medium-pressure cylinder, and the second reheat steam pipeline connects the boiler and the medium- and low-pressure combined cylinder; a sixth valve is provided on the second reheat steam pipeline.

4. The steam turbine generator set according to claim 3, characterized in that: The pre-installed steam turbine, high-pressure cylinder, and medium-pressure cylinder are respectively connected to the high-pressure heating reflux system through a high-pressure heating circuit. The high-pressure heating circuit connected to the pre-installed steam turbine is provided with a fifth valve and a condenser branch, and the condenser branch is provided with a fourth valve; the condenser branch, the exhaust port of the low-pressure cylinder, and the exhaust port of the medium- and low-pressure combined cylinder are all connected to the condenser, and the condenser is connected to the low-pressure heating reflux system; the low-pressure heating reflux system is connected to the high-pressure heating reflux system; The exhaust steam from the low-pressure cylinder and the combined medium- and low-pressure cylinder passes through the condenser, the low-pressure heating and reflux system, and the high-pressure heating and reflux system in sequence to form reheated steam and return to the boiler; the exhaust steam from the front steam turbine, the high-pressure cylinder, and the medium-pressure cylinder passes through the high-pressure heating and reflux system to form reheated steam and return to the boiler.

5. The steam turbine generator set according to claim 4, characterized in that: When the second valve and the fourth valve are closed and the first valve and the third valve are opened, the pre-turbine and the main steam turbine operate in series; when the first valve, the second valve and the third valve are opened and the fourth valve is closed, the pre-turbine and the main steam turbine operate in parallel.

6. The steam turbine generator set according to claim 4, characterized in that: The operation method of the steam turbine generator set is as follows: Set the zero output load operating point of the medium and low pressure combined cylinders and the load operating point of the front steam turbine; When the steam turbine generator set is in the operating condition between the rated load condition and the load condition point of the front steam turbine, the first valve, the third valve, the fourth valve, and the fifth valve are closed, and the second valve and the sixth valve are opened; the front steam turbine is not put into operation, and the high-pressure cylinder, the intermediate-pressure cylinder, the low-pressure cylinder, and the intermediate-low-pressure combined cylinder are put into operation; When the steam turbine generator set is at the load condition point of the front steam turbine or at a condition between the load condition point of the front steam turbine and the zero output load condition point of the medium and low pressure cylinders, the first valve, the third valve and the fifth valve are closed, the second valve and the fourth valve are opened, the front steam turbine is put into operation, and the opening of the sixth valve is adjusted so that the reheated steam enters the medium pressure cylinder and the low pressure cylinder first through the reheated steam pipeline; When the steam turbine generator set is in the medium and low pressure combined cylinder zero output load operating point or the operating condition below the medium and low pressure combined cylinder zero output load operating point, the first valve, the third valve and the fifth valve are closed, the second valve and the fourth valve are opened, the front steam turbine is put into operation, and the opening of the sixth valve is adjusted to switch the medium and low pressure combined cylinder to the zero output state.

7. The steam turbine generator set according to claim 6, characterized in that: The ratio A of the medium and low pressure combined cylinder zero output load condition point to the rated load condition is calculated by the following formula: A=S1 / (S1+S2); Where, S1 is the sum of the flow areas of the medium-pressure cylinder and the low-pressure cylinder, which is the first flow area; S2 is the flow area of the medium- and low-pressure combined cylinder, which is the second flow area; The ratio B of the pre-turbine load condition point to the rated load condition is calculated by the following formula: B=S3 / (S3+S4); Where S3 is the total flow area of the high-pressure cylinder, intermediate-pressure cylinder, low-pressure cylinder, and intermediate- and low-pressure combined cylinder, and S4 is the flow area of the front steam turbine.

8. The steam turbine generator set according to claim 1, characterized in that: A clutch is provided between the main steam turbine main shaft and the front steam turbine main shaft.

9. The steam turbine generator set according to claim 1, characterized in that: During accident conditions, open the fourth valve and close the remaining valves, and all the exhaust steam from the front steam turbine enters the condenser; during low-load conditions, open the fifth valve, and the exhaust steam from the front steam turbine serves as a supplementary heating steam source for the high-pressure heating return system to increase the feed water temperature.

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