CN1328484C - Supercritical air cooling steam turbine - Google Patents

Abstract

The invention relates to a supercritical air-cooled steam turbine suitable for thermal power plants in water-deficient areas. A supercritical air-cooled steam turbine is composed of a supercritical wet-cooled steam turbine high-pressure cylinder, a supercritical wet-cooled steam turbine medium-pressure cylinder and two low-pressure cylinders. Its characteristics That is, the two low-pressure cylinders are the low-pressure cylinders of the air-cooled steam turbine, the medium-pressure cylinder of the supercritical wet-cooled steam turbine and the low-pressure cylinder of the air-cooled steam turbine, and the two low-pressure cylinders of the air-cooled steam turbine are connected by low-pressure cylinder bearing seats, that is, the supercritical air-cooled steam turbine The high-pressure cylinder and medium-pressure cylinder have the same structure as the high-pressure cylinder and medium-pressure cylinder of the supercritical wet-cooled steam turbine. The two low-pressure cylinders of the supercritical air-cooled steam turbine are structurally improved so that the low-pressure exhaust steam of the steam turbine is cooled by direct air cooling, so that the supercritical air-cooled steam turbine not only has the advantages of low heat consumption rate of the supercritical wet-cooled steam turbine and high thermal efficiency of the unit, but also has the advantages of The subcritical air-cooled steam turbine consumes less water and can be used in water-scarce areas.

Description

Supercritical air-cooled steam turbine

technical field

The invention relates to a supercritical air-cooled steam turbine, which is suitable for thermal power plants in water-deficient areas and belongs to the technical field of steam turbines for power generation equipment.

Background technique

The Middle East, Central Asia and some African countries, as well as Northwest China, North China and Northeast my country, are all rich in coal or oil but short of water or arid. The construction of thermal power plants faces the problem of water shortage. Global water resources are decreasing day by day, and industrial and domestic water consumption is increasing day by day. The problem of water resource security in my country is becoming more and more serious. The per capita water resources are equivalent to one-fourth of the world's per capita, and the geographical distribution is extremely uneven. In the coal-rich areas such as Shanxi, Shaanxi, Inner Mongolia, Xinjiang, and Gansu in northern my country , water resources are very scarce. Subcritical air-cooled steam turbines, referred to as air-cooled steam turbines, are used in thermal power plants built in water-shortage areas at home and abroad. The low-pressure exhaust steam of the subcritical air-cooled steam turbine is cooled by a direct air-cooling system or an indirect air-cooling system, and its water consumption is only a quarter of that of a wet-cooled steam turbine with the same power, and the water-saving effect is remarkable. The air-cooled steam turbine currently used at home and abroad is a subcritical air-cooled steam turbine. The steam inlet parameters of the steam turbine are subcritical parameters, the main steam pressure is 16.67MPa, and the temperature range of the main steam and reheat steam is about 538°C to 540°C. The advantage of the subcritical air-cooled steam turbine is that it can be used in water-scarce areas. The main disadvantage of the subcritical air-cooled steam turbine is the high heat consumption rate of the system and the low thermal efficiency of the unit.

The inlet steam parameters of the supercritical wet-cooled steam turbine are supercritical parameters, the main steam pressure ranges from 22.2MPa to 24.99MPa, and the main steam and reheat steam temperatures range from 538°C to 579°C. The supercritical wet-cooled steam turbine is characterized by good economy. Compared with the subcritical wet-cooled steam turbine of the same power, the main advantage of the supercritical wet-cooled steam turbine is low heat consumption rate and high thermal efficiency of the unit. The heat consumption rate of the supercritical wet-cooled steam turbine is about 2 percentage points lower than that of the critical air-cooled steam turbine, and the thermal efficiency of the supercritical wet-cooled unit is about 2 percentage points higher than that of the critical air-cooled unit. As shown in Figure 1, it is a schematic diagram of the structure of the low-pressure cylinder of a supercritical wet-cooled steam turbine. It is mainly composed of a low-pressure cylinder, a low-pressure shaft, a bearing seat, a stationary blade, a moving blade, and an exhaust diffuser. Its structural characteristics are:

1. The height range of the last-stage moving blade 10 of the low-pressure cylinder of the supercritical wet-cooled steam turbine is between 800mm and 1200mm;

2. The height of the two low-pressure cylinders 8 and 9 of the supercritical wet-cooled steam turbine is 6000mm-9000mm, and the length is 6000mm-8000mmm;

3. Usually, the bearing seat 11 of the low-pressure cylinder is inside the low-pressure cylinder, and the cylinder-type bearing seat is used. The center line of the shaft system will rise and fall with the change of the exhaust temperature of the low-pressure cylinder, which will cause the bearing load to be redistributed and affect the stability of the shaft system. ;

4. The total length of the exhaust diffuser 12 of the low-pressure cylinder of the supercritical wet-cooled steam turbine is 1900mm-2500mm, the diameter of the diversion ring outlet of the exhaust diffuser is 4500mm-5000mm, and the initial diffusion angle of the outer wall of the exhaust diffuser is α ₂ is 15°-25°.

The low-pressure exhaust steam of the supercritical wet-cooled steam turbine is cooled by a circulating water system and a wet condenser. Its main disadvantage is that it consumes a lot of water and cannot be used in water-scarce areas.

Contents of the invention

The purpose of the present invention is to provide a supercritical air-cooled steam turbine that can be used in water-shortage areas, has low water consumption, low heat consumption rate and high thermal efficiency of the unit.

In order to achieve the above object, the solution of the present invention is to provide a supercritical air-cooled steam turbine, which is composed of a supercritical wet-cooled steam turbine high-pressure cylinder, a supercritical wet-cooled steam turbine medium-pressure cylinder and two low-pressure cylinders, characterized in that the low-pressure cylinder It is the first air-cooled steam turbine low-pressure cylinder and the second air-cooled steam turbine low-pressure cylinder, between the supercritical wet-cooled steam turbine medium-pressure cylinder and the air-cooled steam turbine low-pressure cylinder, and between the air-cooled steam turbine low-pressure cylinder and the air-cooled steam turbine low-pressure cylinder.

The height of the last-stage moving blades of the first air-cooled steam turbine low-pressure cylinder and the second air-cooled steam turbine low-pressure cylinder is shortened to 500mm-700mm.

The cylinder height H of the first air-cooled steam turbine low-pressure cylinder and the second air-cooled steam turbine low-pressure cylinder is reduced to 5000mm-7000mm, and the axial length L is reduced to 5500mm-6500mm.

The low-pressure cylinder bearing seat is outside the low-pressure cylinder of the first air-cooled steam turbine and the low-pressure cylinder of the second air-cooled steam turbine.

The total length _L1 of the exhaust diffuser tubes of the first air-cooled steam turbine low-pressure cylinder and the second air-cooled steam turbine low-pressure cylinder is shortened to 1000mm-1800mm, and the diameter of the guide ring outlet of the exhaust diffuser tube is reduced to 4000mm-4600mm , the initial diffusion angle α ₂ of the outer wall of the exhaust diffuser pipe 7 expands to 25°-35°.

The invention provides a supercritical air-cooled steam turbine. The steam turbine adopts supercritical steam inlet parameters, the main steam pressure ranges from 22.21MPa to 24.99MPa, and the temperature range of main steam and reheat steam is 538°C to 579°C, that is, supercritical The high-pressure cylinder and medium-pressure cylinder of the critical air-cooled steam turbine have the same structure as the high-pressure cylinder and medium-pressure cylinder of the supercritical wet-cooled steam turbine. The two low-pressure cylinders of the supercritical air-cooled steam turbine are structurally improved so that the low-pressure exhaust steam of the steam turbine is cooled by direct air cooling, so that the supercritical air-cooled steam turbine not only has the advantages of low heat consumption rate of the supercritical wet-cooled steam turbine and high thermal efficiency of the unit, but also has the advantages of The subcritical air-cooled steam turbine consumes less water and can be used in water-scarce areas.

Compared with the supercritical wet-cooled steam turbine with the same power, the height of the last-stage moving blades of the low-pressure cylinders of the two air-cooled steam turbines is shortened, and the low-pressure exhaust steam area of the supercritical air-cooled steam turbine is about 58% to 68% of the exhaust steam area of the supercritical wet-cooled steam turbine. It is suitable for supercritical air-cooled steam turbines with high back pressure. Since the low-pressure exhaust steam area of supercritical air-cooled steam turbines is small, the low-pressure exhaust cylinders of supercritical air-cooled steam turbines should adopt a structure with excellent aerodynamic performance, and the loss coefficient ξ _n of low-pressure exhaust cylinders <1.

The final stage of the supercritical air-cooled steam turbine uses relatively short moving blades to adapt to the characteristics of high back pressure and small volume flow of the air-cooled unit. The design back pressure of a supercritical air-cooled steam turbine is about 1 to 2 times higher than that of a supercritical wet-cooled steam turbine; The back pressure is about 3 times higher. The back pressure change of supercritical wet-cooled steam turbine depends on the warm bulb temperature, while the back pressure of supercritical air-cooled steam turbine depends on the dry bulb temperature. The atmospheric temperature has a large temperature difference between day and night, and the atmospheric temperature changes more frequently than the cooling water temperature, so the back pressure of the supercritical air-cooled steam turbine changes frequently. The supercritical air-cooled steam turbine adopts relatively short final stage blades. Under the condition of high back pressure and wide range of back pressure variation, it has high stage load, no flow blockage, and small shedding area, and the flow is required to be unblocked. The supercritical air-cooled steam turbine adopts relatively short final-stage moving blades, which can increase the stiffness of the moving blades and help reduce the peak dynamic stress of the blades.

The exhaust temperature of a supercritical air-cooled steam turbine operating under load is equal to the saturation temperature corresponding to the back pressure of the steam turbine. Due to the high back pressure of the supercritical air-cooled steam turbine and the large variation range of the back pressure, the low-pressure exhaust steam temperature of the supercritical air-cooled steam turbine is high and the variation range is large. The center line of the low-pressure cylinder of the supercritical air-cooled steam turbine will rise or fall with the change of the exhaust steam temperature of the low-pressure cylinder. Therefore, the supercritical air-cooled steam turbine should adopt a floor-standing bearing housing structure. The bearing housing of the low-pressure cylinder is directly supported on the foundation of reinforced concrete pouring. Ensure the stability of the shafting of the supercritical air-cooled steam turbine.

Since the low-pressure cylinder of the supercritical air-cooled steam turbine adopts a floor bearing seat, the original bearing seat in the low-pressure cylinder of the steam turbine is moved to the outside of the low-pressure cylinder of the steam turbine, so that the total length of the exhaust diffuser pipe of the low-pressure cylinder of the steam turbine is shortened, but the low-pressure cylinder of the steam turbine The shortening of the total length of the exhaust diffuser will make the exhaust aerodynamic performance of the low-pressure cylinder worse. By changing the outlet diameter of the guide ring of the exhaust diffuser and the initial divergence angle _α2 of the outer wall of the exhaust diffuser, the exhaust steam loss of the low-pressure cylinder of the steam turbine can be reduced, and the shortcoming of the relative distance shortening of the low-pressure exhaust cylinder can be compensated. The purpose of better aerodynamic performance of the low-pressure exhaust cylinder is achieved.

The invention has the advantages of low heat consumption rate, high thermal efficiency of the unit, and less water consumption, which is only a quarter of that of a supercritical wet-cooled steam turbine with the same power, and can be used in water-deficient areas.

Description of drawings

Fig. 1 is a structural schematic diagram of a low-pressure cylinder of a supercritical wet-cooled steam turbine;

Fig. 2 is a structural schematic diagram of a supercritical air-cooled steam turbine;

Fig. 3 is a structural schematic diagram of the low-pressure cylinder of a supercritical air-cooled steam turbine;

Fig. 4 is a schematic diagram of the structure of the last-stage diffuser tube of the low-pressure cylinder of the supercritical air-cooled steam turbine;

Detailed ways

Example:

Taking a 600MW supercritical air-cooled steam turbine as an example, the main steam pressure is 24.1MPa, the main steam temperature is 538°C, the reheat steam temperature is 538°C, and the design back pressure is 12.7KPa.

As shown in Figure 2, it is a structural schematic diagram of a supercritical air-cooled steam turbine, which is composed of a supercritical wet-cooled steam turbine high-pressure cylinder 1, a supercritical wet-cooled steam turbine medium-pressure cylinder 2, a first air-cooled steam turbine low-pressure cylinder 3 and a second air-cooled steam turbine low-pressure cylinder 4. Between the intermediate pressure cylinder 2 of the critical wet cooling steam turbine and the low pressure cylinder 3 of the first air cooling steam turbine, and between the low pressure cylinder 3 of the first air cooling steam turbine and the low pressure cylinder 4 of the second air cooling steam turbine are connected by floor bearing blocks 6 .

As shown in Figure 3, it is a schematic structural diagram of the low-pressure cylinder of a supercritical air-cooled steam turbine. The height of the last-stage blade 5 is 539.99mm; The length L is 5380mm; the low-pressure cylinder adopts the floor type bearing seat.

As shown in Figure 4, it is a schematic structural diagram of the last-stage diffuser tube of the low-pressure cylinder of a supercritical air-cooled steam turbine. The total length L1 of the exhaust diffuser tube 7 of the low-pressure cylinder 3 of the first air-cooled steam turbine and the low-pressure cylinder 4 of the second air-cooled steam turbine is 1130.37 mm. The outlet diameter of the diversion ring of the exhaust diffuser 7 is 4600mm, and the exhaust annular area of the final stage is 3.86×4m ² ; the initial diffusion angle α ₂ of the outer wall of the exhaust diffuser 7 is 31°; the exhaust diffuser The ratio of the total length L ₁ of 7 to the final blade 5 is 2.093, the loss coefficient of the diffuser ξ _n =0.953, and ξ _n <1 achieves an optimal design.

Claims (5)

1. overcritical air cooling turbine, form by overcritical wet cooling gas turbine high-pressure cylinder (1), overcritical wet cooling gas turbine intermediate pressure cylinder (2) and two low pressure (LP) cylinders, it is characterized in that, described low pressure (LP) cylinder is the first air cooling turbine low pressure (LP) cylinder (3) and the second air cooling turbine low pressure (LP) cylinder (4), between overcritical wet cooling gas turbine intermediate pressure cylinder (2) and the air cooling turbine low pressure (LP) cylinder (3), connected by floor model bearing support (6) between the first air cooling turbine low pressure (LP) cylinder (3) and the second air cooling turbine low pressure (LP) cylinder (4).

2. overcritical air cooling turbine according to claim 1 is characterized in that, the final stage moving blade (5) of the described first air cooling turbine low pressure (LP) cylinder (3) and the second air cooling turbine low pressure (LP) cylinder (4) highly foreshortens to 500mm-700mm.

3. overcritical air cooling turbine according to claim 1, it is characterized in that, the cylinder height H of the described first air cooling turbine low pressure (LP) cylinder (3) and the second air cooling turbine low pressure (LP) cylinder (4) is reduced to 5000mm-7000mm, and axial length L is reduced to 5500mm-6500mm.

4. overcritical air cooling turbine according to claim 1 is characterized in that, described low pressure (LP) cylinder bearing support (6) is in the outside of the first air cooling turbine low pressure (LP) cylinder (3) and the second air cooling turbine low pressure (LP) cylinder (4).

5. a kind of overcritical air cooling turbine according to claim 1 is characterized in that, the length overall (L of the steam discharge diffuser pipe (7) of the described first air cooling turbine low pressure (LP) cylinder (3) and the second air cooling turbine low pressure (LP) cylinder (4) ₁) shortening to 1000mm-1800mm, the guide ring outlet diameter (Φ) of steam discharge diffuser pipe (7) is reduced to 4000mm-4600mm, the initial angle of flare (α of the outer wall of steam discharge diffuser pipe (7) ₂) expand as 25 °-35 °.

Images