CN102619577A - Device for inhibiting clearance leakage of blade tip and reducing steam flow exciting force - Google Patents

Abstract

The invention discloses a device for suppressing blade tip clearance leakage and reducing steam flow excitation force, comprising: a blade tip shroud and a supporting shell fixed on the inner surface of the cylinder, characterized in that: An annular groove, a fluid dissipating chamber is arranged in the annular groove, a baffle disk is arranged on the blade tip shroud, the outer end of the baffle disk is located in the annular groove of the supporting shell, and A baffle ring is provided on the supporting shell and is located on both sides of the baffle plate, and the baffle ring is connected in the annular groove through an elastic connecting piece. The leakage gas in the device of the invention flows radially along the blades, eliminating the phenomenon of axial spiral flow, and the gas flow directions on both sides of the baffle plate are opposite, the steam flow force is partially offset, and the steam flow force is relatively small. The device of the invention adjusts the gap between the choke ring and the choke plate by introducing pressure gas into the adjustment chamber, and the gap adjustment is convenient.

Description

A device for suppressing blade tip clearance leakage and reducing steam flow excitation force

technical field

The invention relates to a device applied to a steam turbine. The device can reduce the leakage of the tip clearance of the steam turbine and the excitation force of the steam flow, and improve the performance of the steam turbine.

Background technique

At present, it is generally accepted at home and abroad that the loss caused by the leakage of working medium in the blade tip clearance is one of the main factors affecting the efficiency of steam turbines. Leakage in the blade tip clearance will also generate steam flow excitation force, induce steam flow excitation failure, and seriously affect the safe, stable and reliable operation of the unit. With the development of steam turbines towards large capacity and high parameters and the continuous improvement of modern society's requirements for energy saving and emission reduction of large equipment, it is becoming more and more important to reduce the leakage of steam turbine blade tip clearance and the induced steam flow excitation force.

At present, the main measures to reduce the tip leakage at home and abroad include two aspects: (1) Improved design of the tip shape. For blades with shrouds, change the shape of the outer surface of the shrouds from smooth to non-smooth, such as opening grooves on the shrouds to increase leakage flow resistance, etc.; for blades without shrouds, change The shape of the top outer surface is changed from a smooth plane to a honeycomb plane, etc. (2) Improved design of the inner surface of the cylinder. The most common method is to arrange a comb-shaped seal between the inner surface of the cylinder and the tip shroud. The general trend is: the number of sealing teeth is increasing, and the sealing form is becoming more and more complex. In recent years, some new technologies have also appeared, such as: adding a guide ring on the inner surface of the cylinder, and adopting a non-uniform gap design between the inner surface of the cylinder and the blade tip, etc. The main measures to reduce the exciting force of the steam flow include two aspects: (1) Reduce the leakage of the tip of the blade. The smaller the leakage, the smaller the exciting force of the steam flow; (2) Reduce the unevenness of the leakage along the circumferential direction, such as: adjust the eccentricity of the rotor in the cylinder, etc.

The above techniques are effective in reducing tip clearance leakage and steam flow excitation force, but the effect depends largely on the size of the tip clearance. The smaller the blade tip clearance, the better the effect. For steam turbines, in order to prevent dynamic and static friction and possible accidents such as blade breakage, the blade tip clearance cannot be made very small.

Contents of the invention

In view of the above problems, the present invention proposes a new device capable of reducing the leakage of the blade tip of the steam turbine and the excitation force of the steam flow.

The technical solution adopted by the present invention to solve its technical problems is:

A device for suppressing blade tip clearance leakage and reducing steam flow excitation force, comprising: a blade tip shroud and a support shell fixed on the inner surface of a cylinder, characterized in that an annular groove is arranged in the support shell , a fluid dissipating chamber is provided in the annular groove, a spoiler is provided on the blade tip shroud, the outer end of the spoiler is located in the annular groove of the support shell, and a spoiler is provided on the support shell There is a baffle ring and the baffle ring is located on both sides of the baffle plate, and the baffle ring is connected in the annular groove through an elastic connecting piece.

The choke ring also has a force plate parallel to the side of the annular groove, and a pressure regulating chamber is arranged on the side of the annular groove, and the pressure regulating gas is passed through the pressure regulating chamber. , the stress plate of the choke ring is arranged in the pressure regulating chamber and the distance between the choke ring and the choke plate is adjusted under the action of the pressure regulating gas.

The elastic connector is an axial spring.

The choke ring also includes a spring mounting plate, and the two ends of the axial spring are respectively fixed on the spring mounting plate and the side of the annular groove.

The device of the invention is provided with a baffle disk on the blade tip shroud, and a baffle ring is arranged on both sides of the baffle disk. The choke ring is connected with the support shell through an axial spring, and the support shell is installed on the inner surface of the cylinder. A pressure regulating chamber is designed between the choke ring and the supporting shell. When the unit is running, the gap between the choke ring and the choke plate is adjusted by introducing pressurized gas into the adjustment chamber.

The specific principle of this device is analyzed as follows:

(1) The combination of the choke ring and the baffle plate increases the resistance in the process of gas leakage flow, there are more vortices in the chamber, the energy dissipation is large, and the gas leakage is reduced;

(2) The combination of the choke ring and the baffle plate changes the direction of the steam flow excitation force and reduces its action area on the rotor, thus effectively alleviating the steam flow excitation problem;

(3) The gap between the choke ring and the choke plate can be adaptively adjusted by changing the gas pressure in the adjustment chamber.

Compared with the prior art, the beneficial effects of the device for reducing tip clearance gas leakage and steam flow excitation force proposed by the present invention are as follows:

(1) By setting a baffle plate on the shroud and a choke ring between the baffle plate and the supporting shell, the resistance during the gas leakage process is increased. In addition to the traditional energy dissipation mechanism, multiple 90-degree right-angle turns are added to the fluid leakage path of the device of the present invention. During this process, multiple vortices will be formed, the energy dissipation is large, the effect of turbulent flow increasing resistance is obvious, and the leakage volume is also reduced accordingly. smaller. Numerical simulation calculation results using fluid dynamics (CFD) software show that, compared with the traditional comb-teeth sealing device installed on the blade tip, the leakage of the device of the present invention is reduced by 30% to 50%.

(2) The direction of gas leakage and flow on both sides of the baffle plate is opposite, and the exciting force of the steam flow on both sides can be partially offset. In addition, the exciting force of the steam flow mainly acts along the axial direction, and the radial steam flow force has a smaller action area. Therefore, the exciting force of the steam flow will be small. The CFD numerical simulation results show that compared with the traditional blade tip comb seal, the exciting force of the blade tip clearance of the device of the present invention is greatly reduced.

(3) After the pressurized gas is introduced into the adjustment chamber, the gap between the choke ring and the choke plate can be adjusted adaptively according to the needs, avoiding friction, and the gap can be adjusted to a small value, thereby greatly improving the sealing effect. the

Description of drawings

Fig. 1 is a schematic diagram of the device structure of the present invention;

Fig. 2 is a schematic diagram of the local structure of the device of the present invention;

Fig. 3 is a schematic diagram of the structure of the choke ring of the present invention;

Fig. 4 is the change trend of the proportion of fluid leakage in the blade tip clearance of the device of the present invention and the traditional blade tip comb-tooth seal device as the mainstream ratio with the rotating speed;

Fig. 5 is the change trend of the flow loss of the blade tip gap with the rotating speed between the device of the present invention and the traditional blade tip comb-tooth seal device.

In Fig. 1, 1 is the supporting shell, 2 is the annular groove, 3 is the blade tip shroud, 4 is the choke ring, 5 is the baffle plate, and 6 is the fluid dissipation chamber;

In Fig. 2, 1 is a supporting shell, 7 is a pressure regulating chamber, 8 is a spring, 9 is a pressure regulating valve, 10 is a force plate, and 11 is a spring mounting plate;

In Fig. 3, 10 is a force plate, and 11 is a spring mounting plate.

Detailed ways

A device for suppressing blade tip clearance leakage and reducing steam flow excitation force, comprising: a blade tip shroud 3 and a support shell 1 fixed on the inner surface of the cylinder, an annular groove 2 is arranged in the support shell 1, and the support shell 1 is provided with a fluid dissipating chamber 6, a baffle plate 5 is provided on the tip shroud 3, and a choke ring 4 is provided in the annular groove 2, and the choke ring 4 is located on both sides of the baffle plate 5 . The choke ring 4 is provided with a force plate 10 parallel to the side of the annular groove 2, and the force plate 10 and the side of the annular groove 2 form a pressure regulating chamber 7, and the gas is introduced into the pressure regulating chamber through the pressure regulating valve 9 7, and acts on the force plate 10, thereby adjusting the distance between the choke ring 4 and the baffle plate 5. A fluid dissipation chamber 6 is formed between the choke plate 5 and the choke ring 4 . A spring mounting plate 11 is also provided on the choke ring 4 . Both ends of the axial spring 8 are respectively fixed on the spring mounting plate 11 and the side surfaces of the annular groove 2 .

As shown in Figure 1, a spoiler is designed on the blade tip shroud, and spoiler rings are designed on both sides of the spoiler. The combination of the choke plate/choke ring can effectively reduce the leakage of the tip of the steam turbine, and can greatly reduce the exciting force of the steam flow, so as to achieve the effect of increasing efficiency and reducing vibration.

As shown in Fig. 2, under the obstruction of the baffle plate, the gas leakage in the device of the present invention mainly flows along the radial direction of the blades. Due to being hindered by the baffle plate during the gas leakage process, there is no helical flow phenomenon of the leakage fluid. The direction of fluid flow on both sides of the baffle plate is opposite, and the force of steam flow on both sides can be partially offset. Thus, the main source of the steam flow exciting force can be eliminated, and the steam flow exciting force in the new device will be very small. Figure 3 shows the structure of the choke ring, the gas pressure in the pressure regulating chamber can adjust the distance between the choke ring and the choke plate by acting on the force plate.

Fig. 4 has provided the ratio of gas leakage in the device of the present invention and the traditional blade tip comb-tooth seal to the mainstream with the speed change trend; Fig. 5 has provided the gap flow in the device of the present invention and the traditional blade-tip comb-tooth seal Loss variation trend with speed. It can be seen that compared with the traditional blade-tip comb-teeth seal, the leakage of the device of the present invention is significantly reduced, and the flow loss caused by leakage is correspondingly reduced.

Table 1 shows the comparison of steam flow excitation force between the device of the present invention and the traditional blade tip comb-tooth seal device.

Table 1

the Radial excitation force/N Tangential excitation force/N traditional device 1658 -2739 The device of the present invention 299 -139

It can be seen that compared with the traditional blade-tip comb-teeth seal, the exciting force of steam flow in the device of the present invention is greatly reduced, and the device of the present invention has a stronger ability to resist steam flow excitation.

Claims (4)

1. one kind is suppressed the blade tip clearance leakage and reduces the steam flow excitation power apparatus; Comprise: leaf top girth band (3) and be fixed on the supporting housing (1) on the cylinder face; It is characterized in that: an annular groove (2) is set in described supporting housing (1); In supporting housing (1), be provided with fluid dissipation chamber (6), on leaf top girth band (3), be provided with choked flow dish (5), the outer end of this choked flow dish (5) is positioned at the annular groove (2) of described supporting housing (1); On supporting housing (1), be provided with the both sides that block ring (4) and block ring (4) are positioned at choked flow dish (5), described block ring (4) is connected in the annular groove (2) through a Flexible Connector.

2. inhibition blade tip clearance according to claim 1 leaks and reduces the steam flow excitation power apparatus; It is characterized in that: described block ring (4) also have with the stressed plate (10) of described annular groove (2) parallel sided; Also be provided with a pressure regulating cavity chamber (7) in described annular groove (2) side; Logical pressure regulation gas in this pressure regulating cavity chamber (7), the stressed plate (10) of described block ring (4) are arranged in the described pressure regulating cavity chamber (7) and in the distance of adjusting the effect of pressure regulation gas under between block ring (4) and the choked flow dish (5).

3. inhibition blade tip clearance according to claim 2 leaks and reduces the steam flow excitation power apparatus, and it is characterized in that: described Flexible Connector is axle spring (8).

4. inhibition blade tip clearance according to claim 3 leaks and reduces the steam flow excitation power apparatus; It is characterized in that: described block ring also comprises spring mounting plate (11), and the two ends of described axle spring (8) are separately fixed on the side of spring mounting plate (11) and annular groove (2).

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