RU2418986C1 - Turbo-pump unit - Google Patents

Abstract

FIELD: engines and pumps. ^ SUBSTANCE: unit includes housings, centrifugal pump 1, screw 14, two gas turbines 15, 16 and outer and inner shafts 3, 11, Shaft 11 is installed inside shaft 3 on bearings 12, 13. Pump includes centrifugal impeller 4 with hub 5 having inner cavity 34. Impeller 4 is fixed on shaft 3 which is installed in bearing 9 protected with seal 47. Turbines 15, 16 are installed in housing 23 with inlet and outlet branch pipes 51, 52, and include guide vanes 21, 22 and impellers 17, 18. Impellers 17, 18 are installed on shafts 3, 11; screw is installed on shaft 3. Impeller 18 of turbine 16 has smaller diametre than impeller 17 of turbine 15. Impeller 17 of turbine 15 is installed in rear cavity 25 made inside housing 23 of turbine in its central part. Gas supply channel to turbine 16 is made inside outer shaft 3 and connects cavity of inlet branch pipe 51 to cavity 54 before turbine 16. Gas outlet channel is made in the form of annular slot 57, which connects rear cavity 45 of turbine 16 to outlet branch pipe 52 of turbine 15. ^ EFFECT: improving cavitation properties of pump included in turbine-pump unit, and providing removal of axial forces. ^ 4 cl, 6 dwg

Description

The invention relates to pump engineering and can be used in any technical field for pumping liquids that do not contain abrasive inclusions, including for pumping cryogenic liquids. It is preferable to use the pump in turbopump units (TNA) of liquid-propellant rocket engines, including those operating on cryogenic components.

Known screw centrifugal pump according to the patent of the Russian Federation for invention No. 2094660, comprising a detachable body, centrifugal impellers (impellers), auger, shaft and support units in the form of sliding and rolling bearings. The pump has poor cavitation properties.

Known screw centrifugal pump according to the patent of the Russian Federation No. 2106534, IPC 6 F04D 13/04, publ. 03/10/98. This centrifugal screw pump comprises a housing, an impeller and an auger mounted on a shaft. The auger improves the cavitation properties of the pump, since it has better cavitation properties than a centrifugal impeller. The screw provides an increase in the cavitation properties of the pump, but it is mechanically connected to the impeller of the pump and has the same angular rotation speed with it. This does not allow the pump to be operated at very high speeds, for example 40..100 thousand rpm, therefore, such pumps are not currently used.

Known turbopump assembly according to the patent of the Russian Federation No. 2300021, which contains a multistage centrifugal pump and a single-stage turbine. To reduce the dimensions, the pump and turbine are designed for the maximum permissible strength rotational speed of the TNA rotor. At the same time, the cavitational qualities of the pump are deteriorating.

Known turbopump assembly (TNA) according to the patent of the Russian Federation for the invention No. 2232300 C2, prototype. This TNA contains housings, a centrifugal pump, comprising, in turn, a centrifugal impeller with a hub having an internal cavity mounted to a shaft that is mounted in a bearing protected by a seal, and a screw, two turbines installed in a housing with inlet and exhaust pipes and including nozzle apparatuses and impellers, and external and internal shafts, the last of which is installed inside the external shaft on bearings, while the turbine impellers are installed on the external and internal shafts, the screw is mounted on the external m shaft and the second turbine impeller is formed smaller in diameter than the first turbine impeller.

Disadvantages: poor cavitation qualities of a centrifugal pump, especially when it is operating at high speeds, as well as poor unloading of axial forces. When gas is supplied to the turbine from the side opposite to the pump inlet, the axial forces acting on the turbine rotor and the pump rotor are directed in one direction, i.e. add up to the absolute value.

The objective of the invention is to improve the cavitation properties of the pump and to ensure the unloading of the axial forces of the internal and intermediate shafts.

The solution of these problems was achieved in a turbopump assembly containing housings, a centrifugal pump, which, in turn, contains a centrifugal impeller with a hub having an internal cavity mounted to the shaft, which is installed in a bearing protected by a seal, an auger, two turbines installed in a housing with inlet and exhaust nozzles and including nozzle devices and impellers, and external and internal shafts, the last of which is mounted inside the external shaft on bearings, while the turbine impellers are mounted on in the external and internal shafts, the screw is mounted on the external shaft, and the impeller of the second turbine is made smaller in diameter than the impeller of the first turbine, according to the invention both turbines are gas, the impeller of the first turbine is installed in the rear cavity made inside the turbine casing in its central parts, and the channel for supplying gas to the second turbine is made inside the external shaft and communicates the cavity of the turbine inlet pipe with a cavity in front of the second turbine, and the gas outlet channel is made in the form of an annular gap connecting the back cavity of the turbine with the exhaust pipe of the turbine. Inside the hub there is an internal cavity and through holes connecting the internal cavity of the hub with the cavity inside the centrifugal impeller. Centrifugal flow controllers are installed inside the through holes. At the rear end of the centrifugal impeller and at the front end of the impeller of the first turbine, seals are made under which discharge cavities are located.

The invention is illustrated in figure 1 ... 6, where:

figure 1 shows a drawing of a turbopump unit,

figure 2 is a section along aa,

figure 3 - view B of the first embodiment,

figure 4 - view B of the second option,

figure 5 - view B of the third option,

figure 6 - design of the piston.

The turbopump unit (Fig. 1) contains a centrifugal pump 1 and two turbines 2. The centrifugal pump 1 contains an external shaft 3, which is made hollow. A centrifugal impeller 4 is installed on the outer shaft 3. The centrifugal impeller 4 contains a hub 5, blades 6, a front wall 7 and cavities 8 between the blades 6 and the front wall 7. The outer shaft 3 is mounted on a bearing 9 in the housing 10. The inner shaft 11 extends inside the hub 5 and mounted on a radial and thrust internal bearings 12 and 13, respectively. On the inner shaft 11 from the entrance to the centrifugal impeller 4, a screw 14 is installed.

The turbines 2 contain the first and second turbines 15 and 16, respectively, while these turbines are independent of each other, i.e. not mechanically coupled and can rotate at different angular speeds. A rotor impeller 4 of the centrifugal pump is fixed at one end of the outer shaft 3, and an impeller 17 of the first turbine 15 is mounted at its opposite end. A screw 14 is installed at one end of the inner shaft 11, and an impeller 18 of the second turbine 16 is installed at the opposite end of the inner shaft 11. The impellers 17 and 18 comprise impellers 19 and 20, respectively. In front of the working blades 19 and 20, nozzle devices 21 and 22 are fixed respectively. The working blades 19 and 20 and nozzle devices 21 and 22 are installed in the housing 23 of the turbines 2. Between the first turbine 15 and the second turbine 16 a diaphragm 24 is installed. Between the housing 23 of the two turbines 2 and an outer shaft 3 in the central part has a rear cavity 25 in which a second turbine 16 is installed. The impeller 18 of the second turbine 16 has a smaller diameter than the impeller 17 of the first turbine 15. This is necessary so that the second turbine 16 is less powerful, than the first i am turbine 15.

An input housing 26 having a cavity 27 and an output housing 28 having a cavity 29 are connected to the housing 10 of the centrifugal pump 1. A front seal 30 is made between the housing 10 and the centrifugal impeller 2. From the rear end of the centrifugal impeller 4, its hub 5 is made the rear seal 31 and the discharge cavity 32. Inside the hub 5, an intermediate cavity 33 is made. In the hub 5 of the centrifugal wheel 4, an internal cavity 34 and holes 35 are made (FIGS. 1 and 3). The holes 35 connect the cavity 8 with the intermediate cavity 33 and are designed to return selected for the lubrication of the bearings of the flow rate of the pumped product to the centrifugal impeller 4. The holes 35 are made either at an angle of 90 ° (i.e., radially Fig. 3 and 4 or perpendicular to pump axis, FIG. 5), or at an acute angle to the pump axis (i.e., at an angle of less than 90 °). This will exclude the movement of the introduced heated leakage of the pumped product towards the pump inlet and thereby improve its cavitation properties. Radial holes 36 are formed on the inner shaft 11 against the intermediate cavity 33. The inner cavity 34 with radial holes 36 made in the inner shaft 11 connects the intermediate cavity 33 with the cavity of the shaft 37 made inside the inner shaft 11.

Inside the holes 35 can be installed centrifugal flow control 38 (Fig.4 ... 5). Centrifugal flow control 38 is made with the possibility of reducing the flow of the pumped product through them with increasing speed of the external shaft of the pump.

The design of the centrifugal flow controller 38 is shown in figure 4 ... 6. It contains a seat 39, a valve 40 with a stem 41 and a piston 42. A spring 43 is installed inside the seat 39, abutting against the piston 42 and creating a force directed to the axis of the pump OO., I.e. opening the centrifugal flow controller 38. In the piston 42, holes 44 are made (6) to return part of the flow rate of the pumped product into the centrifugal impeller 4.

Inside the outer shaft 3 between the centrifugal pump 1 and the two turbines 2 there is a rear cavity 45 sealed with an internal seal 46. A bearing 13 is installed in this cavity (Fig. 1). An external seal 47 is installed between the centrifugal pump 1 and the two-stage turbine 2, which separates the bearing 9 from both turbines 2. The radial holes 48 are made in the inner shaft 11 and connect the cavities 45 and 37 to lubricate the bearings 9 and 13. The radial holes 49 are made in the outer shaft 3. The bearing 9 is installed in the housing 50. Both turbines 2 have an inlet pipe 51 connected to the housing 23, made on the side of the centrifugal pump 1, and an exhaust pipe 52, made on the opposite side. A supply channel having openings 53 formed in the outer shaft 3 and a cavity 54 inside this shaft is connected to the second stage of the turbine 16. A discharge channel is provided from the second turbine 16, having holes 55 made in the cylindrical wall 56 and an annular gap 57 connecting the cavity 58 between the diaphragm 24 and the cavity 59 inside the pipe 52. An unloading cavity 60 is made on the impeller 17 of the first turbine 15 from the pump side .

When starting the turbopump assembly, gas is supplied through the inlet 51 to the inside of the turbine 2 and passes through the nozzle apparatus 21, the working blades 19. An insignificant part of the total gas flow rate (10 ... 15%) enters through the openings 53 into the cavity 54 and then into the nozzle apparatus 22 and the rotor blades 20 of the second turbine 16, the outer shaft 3 with a centrifugal impeller 4 and the inner shaft 11 with the screw 14 are untwisted. The inner shaft 11 rotates 3 ... 4 times at a lower speed than the outer shaft 3. The shafts 3 and 11 rotate in one side, but with different angular speeds .. Inside the centrifugal impeller 4 and the output thereof, i.e., in the cavity 29, the pressure of the pumped product increases, and part of it (5 ... 7%) through the rear seal 31 enters the discharge cavity 32, passes through the bearing 7, the inclined holes 49, the radial holes 48 into the cavity 37 and through the radial holes 36 enter the inner cavity 33 and further into the holes 35 and returns to the cavity 8 of the centrifugal impeller 4.

Since the screw 14 rotates with an angular speed 2 ... 3 times less than the centrifugal impeller 4, this prevents cavitation at its inlet. Due to the reduced revolutions of the screw 14 itself, cavitation at their inlet edges is also excluded. The screw 14 increases the pressure in the cavity between the screw 14 and the centrifugal impeller 4, creating favorable conditions from the point of view of preventing cavitation at the entrance to the screw 14. There is no bypass of the heated pumped product to the entrance to the screw 14 and to the entrance to the centrifugal impeller 4, since the bypass is organized inside the centrifugal impeller 4. In the presence of a centrifugal flow controller 38, with an increase in the speed of rotation of the impeller, the relative flow rate of the pumped product decreases (in% of the total flow), lzuemogo for lubrication. Naturally, the absolute leakage rate of the pumped product used for lubrication does not decrease, but remains the same or increases slightly. This is due to the fact that the centrifugal forces acting on the valve 40 increase, the valve 40 compresses the spring 42, the gap between the valve 40 and the seat 39 decreases. This will increase the efficiency of the centrifugal pump 1 and at the same time improve its cavitation properties, as it limits the bypass of the heated pumped product into the centrifugal impeller 4 and prevents the reduction of its volumetric efficiency.

When TNA operates in the discharge cavities 32 of the centrifugal pump 1 and in the discharge cavity 60 of the turbine 2, a reduced pressure of the pumped product and gas, respectively, occurs. This helps to reduce the axial forces acting on the outer shaft 3. The unloading of the axial forces acting on the inner shaft 11 is due to the fact that the axial forces acting on the screw 14 and the impeller 18 of the second turbine 16 are compensated.

The application of the invention allowed:

1) significantly improve the cavitation properties of the pump through the use of two screws, reducing the speed of rotation of the screw;

2) to provide unloading of axial forces of internal and external shafts;

3) to design a pump of very high power by increasing the speed of the centrifugal impeller of the pump to the maximum permissible strength;

4) to prevent a stall of the flow of the pumped component in the pump due to cavitation at its inlet;

5) create a turbopump unit with a minimum weight and dimensions with high pressure and performance.

Claims (4)

1. A turbopump assembly comprising housings, a centrifugal pump, comprising, in turn, a centrifugal impeller with a hub having an internal cavity mounted on a shaft that is mounted in a bearing protected by a seal, an auger, two turbines installed in a housing with an inlet and exhaust pipes and including nozzle devices and impellers, and the outer and inner shafts, the last of which is installed inside the outer shaft on bearings, while the turbine impellers are installed on the outer and inner shafts, auger mounted on the external shaft, and the impeller of the second stage of the turbine is made of a smaller diameter than the impeller of the first turbine, characterized in that both turbines are gas, the impeller of the first turbine is installed in the rear cavity, made inside the turbine casing in its central part, and the channel the gas supply to the second turbine is made inside the external shaft and communicates the cavity of the turbine inlet pipe with a cavity in front of the second turbine, and the gas exhaust channel is made in the form of an annular gap connecting the back cavity of the turbine with exhaust pipe of the turbine. 2. The turbopump assembly according to claim 1, characterized in that the inside of the hub has an internal cavity and through holes connecting the internal cavity of the hub with the cavity inside the centrifugal impeller. 3. The turbopump assembly according to claim 2, characterized in that centrifugal flow controllers are installed inside the through holes. 4. The turbopump assembly according to claim 1, or 2, or 3, characterized in that at the rear end of the centrifugal impeller and at the front end of the impeller of the first turbine there are seals under which the discharge cavities are located.

Images