Axial force self-balancing high cavitation-resistant centrifugal pump

Abstract

The present application relates to the technical field of aviation centrifugal pump design, and particularly relates to a high cavitation-resistance centrifugal pump with self-balanced axial force. The balance hole on the impeller will make the suction flow state of the impeller disorder. The oil inlet joint has radial balance oil inlet channels; the pump shell has axial pump shell cooling through holes and balance through holes connecting the front cavity B and the rear cavity A, the balance ring with an annular groove is accommodated in the rear cavity A, the balance oil inlet channels are aligned with the balance through holes; the motor has a motor cooling ring groove which is communicated with the pump shell cooling through holes; the motor shaft has a motor shaft hole, and the motor shaft end is provided with a self-locking nut which has a rearward injection inclined hole to guide the motor shaft hole liquid to be injected into the blade inlet edge of the closed impeller in a certain angle umbrella shape. The self-locking nut has strong foreign matter jamming resistance, can improve the high cavitation-resistance performance of the pump suction inlet, balance the axial force of the impeller, and balance the circulating cooling of the motor rotor.

Description

Technical Field

[0001] This invention relates to the field of aviation centrifugal pump design technology, and in particular to a high cavitation-resistant centrifugal pump with self-balancing axial force, which has high cavitation resistance, strong resistance to foreign matter, and automatic axial force balancing. Background Technology

[0002] Centrifugal pumps are essential power components for fluid transport in aircraft fuel and environmental control systems, especially for low-pressure, high-flow-rate applications, where they offer significant advantages over positive displacement pumps like gear pumps. With advancements in aircraft and aero-engine technology, the requirements for centrifugal pumps' single-stage boost pressure, cavitation resistance, foreign matter resistance, and long service life reliability are steadily increasing. Centrifugal pump boost pressure is gradually approaching the range of low-pressure gear pumps, and in some applications, centrifugal pumps are trending towards replacing gear pumps. However, increased boost pressure exacerbates cavitation at the impeller inlet and axial force imbalance, leading to decreased pump output flow-head and accelerated rotor axial wear. This severely impacts the reliability and lifespan of the centrifugal pump. Furthermore, aerospace centrifugal pumps require simple structure, small size, and light weight; existing centrifugal pumps, with their complex structures and numerous accessories, struggle to meet the high reliability and long service life demands of new aircraft models.

[0003] To address the combined challenges of high cavitation resistance and large axial force in existing centrifugal pumps, the following methods are commonly employed: adding a booster pump before the centrifugal pump or optimizing the design of the inducer to improve cavitation resistance; and using thrust ball bearings or impeller balancing holes to balance the axial force. For pipeline environments requiring strong resistance to foreign object jamming, the design of the inducer wheel at the front end of the centrifugal pump main impeller, designed to improve cavitation resistance, is easily damaged by foreign objects, even causing the main impeller to break and leading to pump failure. More seriously, it can damage precision valves and filters in the hydraulic system. Adding a booster pump to improve cavitation resistance complicates the entire hydraulic system structure and reduces reliability. To balance axial force, balance holes are often made on the impeller, but high-speed pressurized fluid leaking from these holes can impact the impeller's intake flow, causing turbulent flow and reducing flow stability at the impeller inlet, severely compromising cavitation resistance. Using thrust rolling bearings to balance axial force also requires a cup seal to prevent fluid from entering the bearing and damaging the bearing grease, resulting in a complex structure and service life and reliability that cannot meet the new requirements of aircraft technology development. Summary of the Invention

[0004] The purpose of this invention is to propose a high cavitation-resistant centrifugal pump with self-balancing axial force. While improving the cavitation resistance of pipeline pumps, it can also achieve automatic balancing of impeller axial force. It has a simple structure, few vulnerable parts, and can well meet the development needs of the aerospace field for long service life and high reliability.

[0005] The present invention relates to a self-balancing, cavitation-resistant centrifugal pump with axial force, comprising an oil inlet connector, a pump casing, a motor, and a motor controller connected sequentially from front to back.

[0006] The oil inlet connector has radially balanced oil inlet channels;

[0007] The pump casing has an axial pump casing cooling flow hole and a balance flow hole connecting the front cavity B and the rear cavity A. The front cavity B houses a closed impeller, and the rear cavity A houses a balance ring with an annular groove. The balance oil inlet channel is aligned and communicates with the balance flow hole.

[0008] The motor has a motor cooling ring groove that communicates with the pump casing cooling flow hole; the motor shaft has a motor shaft hole, and after the motor shaft passes through the closed impeller and the balance ring, a self-locking nut is installed at the end. The self-locking nut has a rearward-facing injection oblique hole to guide the liquid in the central hole of the motor shaft so that it is sprayed into the blade inlet edge of the closed impeller at a certain angle in an umbrella shape.

[0009] Advantageously, the bottom of the balance ring rests against the bottom end face of the closed impeller, the inner ring is fitted onto the motor shaft, the outer ring rests against the pump casing, and the annular groove opening faces rearward to bear the liquid pressure of the rear cavity A.

[0010] Advantageously, the inner ring end face of the balance ring sits on the stepped surface of the motor shaft by means of adjusting shims.

[0011] Advantageously, the central hole of the self-locking nut communicates with the motor shaft hole, and the opening direction of the spray oblique hole is through the bottom of the central hole of the self-locking nut obliquely backward.

[0012] Advantageously, the self-locking nut also has a milled edge on the outer ring surface for easy installation.

[0013] Advantageously, the motor shaft is supported and mounted in the motor housing by a first graphite bearing and a second graphite bearing, and the first graphite bearing and the second graphite bearing have radial clearance on the outer friction pair end face and axial oil groove on the inner ring face.

[0014] Advantageously, the motor housing is sealed to the pump housing end face on the inner side of the cooling ring groove by a first end face sealing ring, and the pump housing end face is sealed to the outer side of the motor cooling ring groove by a second end face sealing ring.

[0015] Advantageously, the motor rotor and motor stator have a gap through which cooling liquid can pass.

[0016] Advantageously, the outside of the balanced oil inlet channel is the oil inlet, and the pump housing is sealed on both sides of the oil inlet by a first radial sealing ring and a second radial sealing ring, respectively.

[0017] Advantageously, the closed impeller is fixed to the motor shaft by a locking washer.

[0018] Beneficial effects: This invention exhibits strong resistance to foreign object contamination, significantly improves the cavitation resistance of the pump inlet while balancing the impeller axial force, and also ensures proper cooling of the motor rotor. The overall structure is simple, small in size, lightweight, and highly integrated. This integrated approach effectively addresses the challenges faced by centrifugal pump impellers, including cavitation susceptibility, resistance to foreign objects, high axial force, and difficulty in motor cooling, eliminating the need for additional auxiliary systems and products and maximizing product design simplification. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the embodiments of the present invention will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the cross-sectional structure of the centrifugal pump of the present invention, showing the balanced liquid flow;

[0021] Figure 2 This is a schematic diagram of the longitudinal cross-sectional structure of the centrifugal pump of the present invention, showing the anti-cavitation liquid flow.

[0022] Figure 3 This is a schematic diagram of the pump casing;

[0023] Figure 4 This is a schematic diagram of the suction port connector;

[0024] Figure 5 This is a perspective view of the self-locking nut at the shaft end;

[0025] Figure 6 This is a sectional view of the self-locking nut at the shaft end;

[0026] Figure 7 This is a schematic diagram of the fluid passage of a graphite bearing. Detailed Implementation

[0027] See Figure 1 and Figure 2In the embodiment shown, the interrelationship of the various components of the axial force self-balancing high cavitation-resistant centrifugal pump is as follows: the pump casing 3 is connected to the motor 14 by screws, wherein the pump casing cooling flow hole 19 inside the pump casing 3 is aligned with the motor cooling ring groove 20 inside the motor 14, and the motor end face and the pump casing end face are sealed in the inner and outer parts of the cooling channel by a first end face sealing ring 15 and a second end face sealing ring 16, respectively, so as to isolate the anti-cavitation circulation channel from the balance ring channel; the balance ring 6 is a bottom ring structure, the adjusting shim 7 is mounted on the shaft shoulder of the motor shaft 8, the inner ring end face of the balance ring 6 sits on the adjusting shim 7, the closed impeller 5 sits on the bottom outer end face of the balance ring 6, and the closed impeller 5 is connected to the motor shaft 8 for transmission through a flat key. The self-locking nut 2 is screwed onto the threaded end of the motor shaft 8. The self-locking nut 2 and the closed impeller 5 are locked together by the locking washer 4. The lug of the locking washer 4 is first locked to the milled edge of the closed impeller 5. The self-locking nut 2 is screwed to the bottom and contacts the plane of the locking washer 4, so that the lug of the locking washer 4 is aligned with the milled edge of the self-locking nut 2, and the lug is bent to connect it to the self-locking nut 2 as one piece.

[0028] The balancing ring 6, which balances the axial force, has a small gap between its outer ring and the inner hole of the pump casing. Two to three narrow annular grooves can also be cut into the balancing ring 6 to provide a gap resistance seal, separating the front chamber (B) of the pump pressure chamber from the rear chamber (A) of the balancing chamber. The bottom outer end face of the balancing ring 6 serves as the mounting plane for the impeller hub. To improve the strength of the balancing ring, it is machined from titanium alloy, which also minimizes its weight. When performing dynamic balancing on the high-speed rotor, only the balancing ring is weighed down without compromising the geometric accuracy of the impeller, making it easy to adjust and maintain.

[0029] The impeller is designed as a closed impeller, with a small clearance fit between the impeller front end ring and the pump inlet connector, and a larger clearance between the front cover plate and the inlet connector. This reduces the leakage from the pump chamber into the suction port radially through the front cover plate and the front end ring, and can better balance the axial force.

[0030] The motor 14 has a liquid-cooled circulating structure. In order to isolate the rotor and stator of the brushless DC motor from the medium being transported, both the stator 11 and the rotor 10 are designed with titanium alloy shielding sleeves, and the thickness of the shielding sleeves is made as small as possible to reduce the eddy current loss during motor operation.

[0031] like Figure 3 As shown, the pump casing 3 has an axial cooling flow hole 19 and a balance flow hole 31 connecting the front cavity B and the rear cavity A. The flow channel is embedded in the reinforcing ribs outside the pump casing, achieving the flow guiding function with minimal size and weight, making the external structure simple and the whole machine coordinated.

[0032] The oil inlet sidewall of the oil inlet connector 1 has a balanced oil inlet channel 32, such as Figure 4 As shown, the outer side of the balanced oil inlet channel 32 is the oil outlet 24, and the inner side is the oil inlet 25.

[0033] The oil inlet connector 1 is installed into the pump housing 3. The balanced oil inlet channel 32 is connected to the rear cavity A of the pump housing 3 through the balanced flow hole 31. The oil inlet connector is provided with a first radial sealing ring 17 and a second radial sealing ring 18 for sealing. The oil inlet connector 1 is fastened to the housing 3 by screws.

[0034] like Figure 5-6 As shown, the specially designed self-locking nut 2 at the motor shaft end is designed to run in the opposite direction to the motor shaft rotation. The top of the self-locking nut 2 is designed as a spherical surface to conform to the inlet flow, thus stabilizing the flow. An oblique injection hole 23 is designed on the outer cylindrical surface to guide the liquid flow from the central hole of the motor shaft, causing it to be sprayed at a certain angle in an umbrella shape into the blade inlet edge of the closed impeller 5, in the same direction as the inlet flow, improving the cavitation margin and cavitation resistance of the device. To ensure that the self-locking nut 2 at the shaft end does not loosen under vibration, pressure impact, and other conditions, the specially designed self-locking nut 2 is combined with a locking washer 4. One end of the locking lug of the locking washer 4 is fastened to the milled edge 22 of the nut, and the other end is fastened to the milled edge of the impeller hub. To ensure that the locking lug of the locking washer 4 is aligned with the self-locking nut and the impeller hub locking edge when the self-locking nut is tightened to the correct position, an adjusting shim is used under the locking washer 4 to facilitate self-locking adjustment.

[0035] like Figure 7 As shown, the graphite bearing 9 located on the rear side of the balance ring 6 has self-lubricating properties. The oil leaking through the radial clearance 28 of the bearing on the outer friction pair end face 27 can enter the inner friction pair end face of the graphite bearing 9 and the motor rotor 10 along the axial oil groove 30 on the inner ring surface 29 of the graphite bearing, ensuring the cooling and hydrodynamic lubrication of the graphite bearing 9 and carrying away the wear material of the dynamic friction pair, thereby improving the service life of the bearing.

[0036] The graphite bearing design allows for high-speed friction between the motor shaft shoulder and the graphite bearing end face to completely balance the remaining axial force in the balance ring. Radial grooves are opened on the dynamic friction pair end face of the graphite bearing to guide flow and achieve the dynamic pressure lubrication function of the friction pair end face. Under a small residual axial force, the wear is small during long-term operation, and the entire bearing is immersed in the fluid being transported, so its frictional heat and wear materials can be carried away by the fluid, which can achieve long-life and high-reliability operation.

[0037] Based on the anti-cavitation performance design structure, a balancing axial force structure for the impeller is designed, breaking through the complex structures of previous balancing holes and balancing pipes, and adopting a specially designed balancing ring to simplify the structure. Compared with conventional centrifugal pumps, only one balancing ring is added and set on the side of the impeller rear cover plate, rotating with the impeller via key drive. The back cavity of the balancing ring is connected to the pump inlet through a cast flow channel on the casing, and the hydraulic pressure in the back cavity of the balancing ring is basically the same as that in the pump inlet; the front of the balancing ring is opposite to the impeller rear cover plate, and the hydraulic pressure on the front of the balancing ring is the same as that on the impeller rear cover plate. It is possible to design the diameter of the pressure-bearing surface of the balancing ring to be the same as the diameter of the impeller inlet ring to ensure that the generated axial force is consistent.

[0038] The implementation process of this invention is as follows: Connect the inlet and outlet of the pump to the pipeline, power the DC brushless motor, and make the motor rotor rotate at high speed through the controller. The motor drives the closed impeller 5 and the balance ring 6 to rotate at high speed. The closed impeller 5 draws in the fluid and does work on the fluid, outputting a medium with a certain flow rate and pressure. The pressurized medium enters the motor through the cooling flow hole on the back cover side of the impeller 5. After circulating in the motor, it passes through the center hole of the motor shaft 8 and is sprayed into the impeller blade inlet edge through the inclined hole on the self-locking nut 2 in an umbrella shape, which increases the kinetic energy and pressure energy of the impeller blade suction flow. At the same time, the high-speed jet destroys potential cavitation bubbles, directly and effectively improving the net positive suction head of the impeller suction device. Meanwhile, the cavity behind the balance ring 6 is connected to the pump inlet connector through the flow hole designed on the pump casing 3. The balance ring and the casing have a very small fit clearance, which prevents high-pressure fluid leakage at the impeller rear cover plate. The leaked trace liquid enters the pump suction port through the cast flow channel on the casing, which increases the fluid kinetic energy at the suction port to improve the anti-cavitation performance. The pressure in the rear cavity of the balance ring is not much different from the pressure of the inlet connector. The outer diameter of the balance ring is consistent with the outer diameter of the impeller front sealing ring, realizing automatic axial force balance. The remaining axial force causes the boss of the motor shaft 8 to press on the graphite bearing 9 to make high-speed rotation. The liquid in the rear cavity of the sealing balance ring is not the same as the circulating fluid inside the motor, which maximizes the automatic axial force balance effect.

Claims

1. A self-balancing centrifugal pump with high cavitation resistance, belonging to pipeline pumps in the aerospace field, comprising an oil inlet connector (1), a pump casing (3), a motor (14), and a motor controller (13) connected sequentially from front to back, characterized in that: The oil inlet connector (1) has a radial balanced oil inlet channel (32), with an oil inlet (24) on the outside and an oil outlet (25) on the inside; the pump housing (3) has an axial pump housing cooling flow hole (19) and a balanced flow hole (31) connecting the front cavity B and the rear cavity A, with the oil inlet (24) of the balanced oil inlet channel (32) aligned and communicating with the balanced flow hole (31); A closed impeller (5) is housed in the front cavity B, and a balance ring (6) with an annular groove is housed in the rear cavity A. The annular groove opens to the rear and bears the liquid pressure of the rear cavity A. The bottom of the balance ring (6) rests on the bottom end face of the closed impeller (5), and the inner ring end face sits on the step surface of the motor shaft (8) through the adjusting shim (7). The inner ring is fitted on the motor shaft (8), and the outer ring rests on the pump casing (3) and forms a small gap with the inner hole of the pump casing. The motor (14) has a motor cooling ring groove (20) which is connected to the pump casing cooling flow hole (19); the motor shaft (8) has a motor shaft hole (21), and after the motor shaft (8) passes through the balance ring (6) and the closed impeller (5), a self-locking nut (2) is installed at the end. The center hole of the self-locking nut (2) is connected to the motor shaft hole (21). The self-locking nut (2) has a rearward spray oblique hole (23). The opening direction of the spray oblique hole (23) is to pass through the bottom of the center hole of the self-locking nut (2) obliquely to the rear, so as to guide the liquid in the center hole of the motor shaft to be sprayed into the blade inlet edge of the closed impeller (5) at a certain angle in an umbrella shape; The motor rotor is made to rotate at high speed by the controller. The motor drives the closed impeller (5) and balance ring (6) to rotate at high speed. The pressurized medium enters the motor through the cooling flow hole (19) on the back cover side of the impeller (5). After circulating in the motor, it enters the impeller blade inlet side through the motor shaft hole (21) of the motor shaft (8) and the inclined hole on the self-locking nut (2). This increases the kinetic and pressure energy of the impeller blade suction flow. At the same time, the high-speed jet destroys potential cavitation bubbles. The cavity on the back side of the balance ring (6) is connected to the pump inlet joint through the flow hole designed on the pump casing (3). The balance ring (6) and the pump casing (3) have a very small fit clearance to prevent high pressure fluid leakage at the impeller back cover. The leaked trace liquid enters the pump inlet through the cast flow channel on the pump casing (3) to increase the fluid kinetic energy effect at the inlet and improve the anti-cavitation performance. The pressure in the back cavity of the balance ring is not much different from the pressure of the inlet joint. The outer diameter of the balance ring is consistent with the outer diameter of the front sealing ring of the impeller, realizing automatic axial force balance.

2. The high cavitation-resistant centrifugal pump according to claim 1, characterized in that: The self-locking nut (2) also has a nut milled edge (22) on the outer ring surface for easy installation.

3. The high cavitation-resistant centrifugal pump according to claim 1, characterized in that: The motor shaft (8) is supported and installed in the motor housing by a first graphite bearing (9) and a second graphite bearing (12). The first graphite bearing (9) and the second graphite bearing (12) have a radial clearance (28) on the outer friction pair end face (27) and an axial oil groove (30) on the inner ring face (29).

4. The high cavitation resistance centrifugal pump according to claim 3, characterized in that: The motor housing is sealed to the pump housing (3) end face by a first end face sealing ring (15) on the inner side of the cooling ring groove (20), and sealed to the pump housing (3) end face by a second end face sealing ring (16) on the outer side of the motor cooling ring groove (20).

5. The high cavitation resistance centrifugal pump according to claim 4, characterized in that: The motor rotor (10) and motor stator (11) have a gap through which cooling liquid passes.

6. The high cavitation-resistant centrifugal pump according to claim 4, characterized in that: The oil inlet (24) is sealed to the pump casing (3) by the first radial sealing ring (17) and the second radial sealing ring (18) on both sides.

7. The high cavitation-resistant centrifugal pump according to claim 1, characterized in that: The closed impeller (5) is fixed to the motor shaft (8) by a locking washer (4).

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