RU2572468C2 - Sealing of shaft of turbine pump unit (versions) - Google Patents

Abstract

FIELD: machine building.

SUBSTANCE: under suggested invention is shaft seal of the turbine pump unit containing impeller, located between pump and turbine installed on shaft, the smooth side of the impeller is connected with blade side of the impeller using the bypass holes, made in its disk; holes connecting smooth and blade sides of the impeller are displaced from the axis of symmetry of between blades channel along the rotor rotation direction; in the pump casing between the smooth side of the impeller and pump the ribs are made; between the blade side of the impeller and turbine additional seal is made; in the turbine casing between the turbine and blade side of the impeller the by-pass holes are made with output to the blade side of the impeller; and in case between the smooth side of the impeller and pump the ribs are made.

EFFECT: exclusion of liquid boiling in seal, minimization of pump leaks to turbine during cooldown.

6 cl, 5 dwg

Description

The present invention relates to the field of turbomachinery, namely to high-speed high-pressure centrifugal pumps, and can be used in the field of rocket science, in turbopump units (TNA) of liquid-propellant rocket engines (LRE).

The performance and parameters of the turbopump unit is significantly affected by the operation of the separation seal between the pump and the turbine. Incorrect operation of the separation seal can lead either to a breakthrough of gas from the turbine cavity to the pump cavity, or to increased leakage of liquid from the pump to the turbine and deterioration of the characteristics of both the pump and the turbine. Breakthrough of high-pressure gas from the turbine cavity into the pump cavity leads to damage and loss of the operable state of the bearings due to their insufficient cooling, and the ingress of gas into the flow part of the pump leads to cavitation failure. This is the cause of the emergency shutdown of the liquid rocket engine. Leakage from the pump to the turbine leads to a significant decrease in the efficiency of the unit due to a decrease in the useful gas flow through the nozzle apparatus, distortion of the gas flow and ballasting after the nozzle apparatus by leakage of cold liquid. In addition, leakage of cryogenic liquid into the turbine can cause large temperature gradients in the disk of the turbine impeller, high thermal stresses and cause cracks in the disk with its subsequent destruction. It should be noted that in the practice of turbine engineering, a bearing of a turbine support is often installed in the cavity of the separation seal, the operability of which depends on the operation of the separation seal.

In general, the separation seal between the pump and the turbine must satisfy the following requirements:

- prevent gas leaks from the turbine into the pump;

- provide a minimum, stable amount of leakage from the pump to the turbine;

- to ensure the operability of the turbopump unit at all engine operating modes, including when the allowable wear of the unit structural elements appears.

In some cases, an additional requirement is imposed on the separation seal to minimize leakage from the pump to the turbine when the rotor is not rotating. First of all, the requirement is for the TNA of engines running on cryogenic fuel components, since leaks at engine start can lead to emergency situations.

Thus, the separation system of the cavities of the pump and turbine ТНА deserves special attention during the development and operation of the liquid propellant rocket engine. The main objective of such a seal is to eliminate the possibility of gas entering the turbine into the pump with a minimum reduction in the efficiency of the heat pump.

In TNA liquid propellant rocket engines operating on high-boiling fuel components in separation seals, impeller seals are widely used. This seal makes it possible to almost completely eliminate fluid leakage into the turbine cavity, which is especially important for small-sized ТНА, where even a small leakage during operation leads to a significant decrease in efficiency. In an impeller seal, a leak into a turbine cavity is determined only by the evaporation of the liquid from the gas-liquid interface in the impeller. Moreover, such a leak practically does not affect the characteristics of the turbine.

Known shaft seal of a turbopump assembly containing an impeller located between the pump and the turbine mounted on the shaft (Design and engineering of liquid rocket engines / G.G. Gakhun, V.I. Baulin, V.A. Volodin, etc.; Under the general. Edited by G.G. Gakhun. - M .: Mechanical Engineering, 1989. - 424 p., Fig. 10.19 (p. 220) - prototype).

Such a shaft seal of a turbopump assembly as applied to a liquid propellant rocket engine has the following disadvantages.

The use of an impeller (hydrodynamic radial) seal when separating the cavities of the turbine and the pump pumping cryogenic liquid leads to its heating and boiling in the seal, which causes gas to enter from the turbine cavity into the pump cavity. In addition, if it is necessary to cool down the leakage of liquid from the pump into the turbine will have a significant value.

The objective of the invention is to eliminate the boiling of liquid in the seal, minimizing leaks from the pump cavity into the turbine cavity during cooling.

In the present invention, the technical effect is achieved by the fact that in the shaft seal of the turbopump assembly containing an impeller with holes connecting the smooth and scapular sides located between the pump and the turbine mounted on the shaft according to the invention:

- the holes connecting the smooth and scapular sides of the impeller are offset from the axis of symmetry of the interscapular channel in the direction of rotation of the rotor;

- ribs are made in the pump housing between the smooth side of the impeller and the pump;

- between the blade side of the impeller and the turbine an additional seal is made;

- in the turbine housing between the turbine and the impeller side of the impeller, bypass openings are made with access to the impeller side of the impeller;

- ribs are made in the pump housing between the smooth side of the impeller and the pump.

The proposed shaft seal of a turbopump assembly is shown in FIG. 1, in FIG. 2, 3, 4, 5 - options for sealing the shaft of a turbopump assembly, where:

1 - impeller;

2 - pump;

3 - turbine;

4 - shaft;

5 - smooth (back) side of the impeller;

6 - blade side of the impeller;

7 - holes;

8 - bypass channel;

9 - scapula;

10 - interscapular canal;

11 - phase boundary;

12 - liquid;

13 - gas;

14 - consolidation;

15 - ribs;

16 - bypass holes;

17 - channels;

18 - impeller;

19 - outlet pipe of the pump;

20 - inlet tube.

The shaft seal of the turbopump assembly (Fig. 1) contains an impeller 1, located between the pump 2 and the turbine 3, mounted on the shaft 4. In the impeller disk, holes 7 are made connecting its smooth and blade sides. The holes 7 are shifted in the direction of rotation of the shaft relative to the axis of symmetry of the interscapular channel 10. Between the blade side 6 of the impeller and the turbine 3 can be made additional seal 14 (Fig. 2). Between the smooth side 5 of the impeller and the pump 2 can be made radial ribs 15 (Fig. 3). To reduce fluid leakage through the impeller, the bypass holes 16 connected by channels 17 to the impeller 18 are made in the turbine casing from the impeller side 6 of the impeller (Fig. 4). Alternatively, at high pressure in the turbine 3, the bypass holes 16 are connected to the discharge pipe 19 of the pump 2, for example, using the supply pipe 20 (Fig. 5).

During operation of the turbopump unit, the turbine 3 drives the pump, while the impellers of the pump and turbine, the impeller 1 rotate at the same angular speed, since they are mounted on the same shaft 4, which is supported by bearings. The liquid from the pump through the bypass channels 8 enters the impeller 1, and it can be supplied from the output of the impeller or from the output of the pump outlet housing. Due to the rotation of the impeller on its blade side 6, facing the turbine 3, a mirror is formed - the phase boundary 11 of the liquid 12 and gas 13. The flow of fluid through the holes 7 connecting the smooth (back) 5 and blade 6 of the side of the impeller 1, ensures its circulation and eliminates the boiling of fluid in the cavity of the impeller. The distance from the axis of rotation of the impeller to the axis of the holes 7 should be less than the distance from the axis of rotation of the impeller to the location of the phase boundary 11 - the mirror.

The angular arrangement of the holes 7 to ensure uniform supply of fluid into the interscapular channel 10 is shifted in the direction of rotation of the rotor. This ensures reliable separation of the pump 2 and turbine 3 with minimal leakage into the turbine cavity, caused only by evaporation from the phase boundary in the interscapular channels 10 of the impeller 1. Depending on the pressure drop, mirror formation can occur below the impeller blades, which can lead to large leaks . To avoid this, radial ribs 15 are made on the housing between the pump 2 and the smooth side 5 of the impeller, while ensuring alignment and an additional pressure drop.

To minimize the leakage of liquid from the pump to the turbine during the cooling process of the unit between the blade side of the impeller 6 and the turbine 3, an additional seal 14 is made, which can be non-contact, contact or opening when a certain pressure is reached. When making the bypass holes 16 in the housing from the scapular side of the impeller 6, the working fluid under pressure enters the bypass holes 16 through channels 17 made in the housing. The fluid through the channels 17 comes from the outlet of the impeller 18 of the pump 2. At a pressure in the turbine 3 exceeding or close to the pressure at the outlet of the impeller 18, the fluid through the channels 17 to the bypass holes 16 comes from the outlet of the pump 2 from the outlet pipe 19, for example, by the supply pipe 20, which provides fluid from the pump outlet pipe 19 to the channels 17. When the shaft 4 rotates, the blades 9 and the interscapular channels 10 of the impeller 1 are successively communicated with these bypass holes 16. When the holes 16 and the interscapular are aligned the channel 10 the liquid is injected into the cavity 10 interblade channel of the impeller. Such injections reduce the temperature in the interscapular channel 10 of the impeller, which eliminates the boiling of the working fluid in it.

A similar impeller seal can be used to separate the pump and the environment.

Thus, in the turbopump unit, reliable separation of the pump and turbine cavities is ensured in all operating modes with high efficiency of the unit, including when the pump is cold, which ensures reliable operation of the ТНА as part of a liquid propellant rocket engine.

Claims (6)

1. The shaft seal of the turbopump assembly, comprising an impeller with holes connecting the smooth and blade sides located between the pump and the turbine mounted on the shaft, characterized in that the holes connecting the smooth and blade sides of the impeller are offset from the axis of symmetry of the interscapular channel in the direction of rotation rotor. 2. The shaft seal of the turbopump assembly according to claim 1, characterized in that an additional seal is made between the impeller side of the impeller and the turbine. 3. The shaft seal of the turbopump assembly according to claim 1, characterized in that fins are made in the housing between the smooth side of the impeller and the pump. 4. The shaft seal of the turbopump assembly, comprising an impeller located between the pump and the turbine mounted on the shaft, characterized in that bypass openings are made in the housing between the turbine and the impeller side of the impeller and exit to the impeller side of the impeller. 5. The shaft seal of the turbopump assembly according to claim 4, characterized in that an additional seal is made between the impeller side of the impeller and the turbine. 6. The shaft seal of the turbopump assembly according to claim 4, characterized in that the ribs are made in the housing between the smooth side of the impeller and the pump.

Images