Structure for improving anti-cavitation performance and operation stability of fuel pump at low flow rate

Abstract

This invention discloses a structure for improving the anti-cavitation performance and operational stability of a fuel pump at low flow rates, comprising an inducer, an impeller, a shaft, a housing, a stationary ring, an upper bearing, and a lower bearing. A flow guide is installed at the upper end of the housing. The main body of the flow guide is a rotating structure, with an inlet straight pipe section coaxially arranged in the upper part of the main body. An arc-shaped groove is formed between the main body and the outer wall of the lower end of the straight pipe section. A ring of wedge-shaped flow guide plates is fixed to the inner wall of the main body by connecting ribs, forming a flow channel between the wedge-shaped flow guide plates and the inner wall of the main body. The upper end of the flow channel communicates with the arc-shaped groove, and the upper end of the wedge-shaped flow guide plates extends into the arc-shaped groove, forming a U-shaped structure. During low-flow operation, the return fuel from the inducer enters the flow channel and ultimately flows back through the arc-shaped groove to the bottom of the inlet straight pipe section, avoiding impact on the incoming flow and causing flow turbulence.

Description

Technical Field

[0001] This invention relates to aviation application technology, and to a structure that improves the anti-cavitation performance of fuel pumps at low flow rates and enhances the operational stability of fuel pumps. Background Technology

[0002] Centrifugal pumps for aviation fuel are widely used in aircraft fuel systems for fuel supply and transportation. During high-altitude flight, the pressure at the fuel pump inlet decreases, making it prone to cavitation, which adversely affects the pump's performance, lifespan, and reliability. Due to the high-altitude cavitation caused by aircraft flight, fuel pumps require high cavitation resistance. The inducer and impeller, as the main moving hydraulic components of the fuel pump, have a crucial impact on the overall cavitation performance due to their structure and inlet flow conditions. Considering the operating characteristics of the fuel pump, the design must accommodate both high-flow and low-flow operating scenarios. For aircraft cruise, the typical operating condition is low flow. When the fuel pump operates at low flow, the inlet angle of attack of the inducer increases, making it more difficult for fuel to pass through the inducer. Furthermore, fuel impacting the inlet working surface of the inducer can easily generate backflow and form vortices, further hindering incoming flow and thus affecting the fuel pump's performance. Summary of the Invention

[0003] The purpose of this invention is to provide a structure that improves the anti-cavitation performance and operational stability of a fuel pump at low flow rates. This structure effectively reduces the backflow and vortex phenomena of liquid on the inlet working surface of the inducer under low flow conditions, diverts the backflow generated by the inducer so that it does not collide with the incoming flow, improves the hydraulic efficiency of the fuel pump, improves the inlet flow conditions of the fuel pump, reduces pressure pulsation, and thus improves the operational stability of the fuel pump.

[0004] To achieve the above objectives, the present invention employs the following technical solution:

[0005] A structure for improving the low-flow cavitation resistance and operational stability of a fuel pump includes an inducer, an impeller, a shaft, a housing, a stationary ring, an upper bearing, and a lower bearing. The inducer and impeller are installed inside the housing. The inducer is an axial-flow impeller, and the impeller is a centrifugal impeller. The inducer and impeller are respectively mounted on the upper and lower parts of the shaft. The shaft drives the inducer and impeller to rotate via a flat key. A stationary ring is placed at the lower end of the shaft. The lower end of the stationary ring and the bottom end of the shaft are respectively equipped with an upper bearing and a lower bearing. Both the lower bearing and the lower bearing are graphite bearings, mainly used for support and thrust. The housing is a volute-shaped collector used to pressurize the fuel after it has been accelerated by the inducer and impeller.

[0006] A flow guide is installed at the upper end of the shell. The main body of the flow guide is a rotating structure. An inlet straight pipe section is coaxially arranged in the upper part of the main body, and an arc-shaped groove is formed between the main body and the outer wall of the lower end of the straight pipe section. A ring of wedge-shaped flow guide plates is fixed on the inner wall of the main body by connecting ribs. A flow channel is formed between the wedge-shaped flow guide plates and the inner wall of the main body. The upper end of the flow channel is connected to the arc-shaped groove, and the upper end of the wedge-shaped flow guide plates extends into the arc-shaped groove, forming a U-shaped structure. In low-flow operation, the return fuel from the inducer enters the flow channel and finally flows back through the arc-shaped groove to the bottom of the inlet straight pipe section, avoiding impact on the incoming flow and causing flow turbulence.

[0007] Furthermore, the upper edge of the wedge-shaped guide plate is parallel to the lower edge of the inlet straight pipe section, which facilitates the guide device to redirect the generated liquid back to the inlet of the inducer, while reducing flow loss.

[0008] Furthermore, a mounting plate is provided on the outer wall of the bottom end of the main body for docking and installation with the upper part of the shell.

[0009] Furthermore, the outer surface of the wedge-shaped drainage plate is parallel to the inner surface of the main body, and the inner surface of the wedge-shaped drainage plate is an arc-shaped convex surface, so that the thickness of the wedge-shaped drainage plate is the greatest in the middle, and the thickness gradually decreases from the middle to the upper and lower ends; the thickness at the thinnest point at the upper end is preferably 0.8 mm, and the thickness at the thinnest point at the lower end is preferably 0.5 mm, which can reduce the impact loss caused by liquid backflow. The maximum thickness of the wedge-shaped drainage plate is preferably 1 to 2.5 mm, more preferably 1.5 mm.

[0010] Furthermore, the angle between the outer wall of the main body and the shaft is 5 to 12°, preferably 8°. In this scheme, since the outer wall of the wedge-shaped guide plate is arranged parallel to the inner wall of the main body, the angle is also the inclination angle between the flow channel and the shaft. If the inclination angle of the flow channel is too small, the inlet flow area will be reduced and the flow capacity will decrease. If the inclination angle of the flow channel is too large, the fluid loss will be increased and the flow capacity will be reduced.

[0011] Furthermore, the width d of the flow channel is 3 to 8 mm, preferably 5 mm. If the distance is too large, the inlet flow area will be reduced and the flow capacity will decrease. If the distance is too small, the fluid loss will be increased and the flow capacity will be reduced.

[0012] Furthermore, the ratio of the axial length of the wedge-shaped guide plate to the lead of the inducer wheel is 0.5 to 1, preferably 0.6. The short guide distance means that the backflow velocity cannot be effectively reduced, and the backflow impacts the guide, increasing flow loss.

[0013] Furthermore, the connecting rib is a rectangular thin sheet structure, the connecting rib is evenly and vertically distributed along the circumference, and the surface of the connecting rib is parallel to the axis; the number of connecting ribs is preferably 3 to 8, more preferably 6 pieces; under low flow conditions, the fuel generates vortices upward along the outer edge of the inducer, and the connecting rib can act as a separation disc to separate and break the vortex.

[0014] Furthermore, the connecting rib has a thickness of 1-2 mm and is connected to the middle position of the wedge-shaped drainage plate to improve structural strength.

[0015] Furthermore, the gap between the outer edge of the inducer wheel and the upper cover plate of the impeller and the inner wall of the housing is preferably 0.2mm. This ensures that the rotating parts will not rub against the housing and reduces hydraulic loss, thereby improving the efficiency of the fuel pump.

[0016] Furthermore, the impeller blades are twisted blades, and the blade inlet is pre-rotated to reduce the impact loss at the inlet.

[0017] Furthermore, the impeller is preferably a structure with long and short blades, which can reduce impeller inlet blockage.

[0018] Furthermore, the impeller blade outlet is machined with a triangular notch, the included angle of which is preferably 80° to 150°, more preferably 120°. This notch can eliminate the backflow zone at the outlet, improve the impact of secondary backflow at the outlet on performance, and thus improve the performance in the low flow rate zone.

[0019] Furthermore, the impeller employs a labyrinth seal, and the sealing ring groove can be located on the upper cover plate of the impeller or on the housing near the impeller inlet.

[0020] Furthermore, the sealing ring groove is stepped and has a width of 0.5 to 1.5 mm, preferably 1.0 mm. When the impeller rotates, the fuel will generate a throttling effect when passing through the tortuous labyrinth groove, thereby achieving the purpose of preventing leakage, reducing the hydraulic loss of the pump, and improving the performance of the fuel pump.

[0021] Compared with the prior art, the present invention has the following technical features:

[0022] This invention provides a structure that improves the cavitation resistance and operational stability of a fuel pump at low flow rates. This design effectively mitigates backflow and vortex phenomena at the inlet working surface of the inducer under low flow conditions, diverting the backflow generated by the inducer and preventing it from colliding with the incoming flow, thus improving the hydraulic efficiency of the fuel pump. It also improves the inlet flow conditions of the fuel pump, reduces pressure pulsation, and consequently enhances the operational stability of the fuel pump. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the structure of the present invention;

[0024] Figure 2 This is an axial sectional view of the drainage device of the present invention;

[0025] Figure 3 This is a schematic diagram of the impeller body of the present invention;

[0026] Figure 4 This is an axial sectional view of the housing of the present invention;

[0027] Figure 5 This is a schematic diagram of the upper bearing of the present invention.

[0028] Wherein: 1-flow guide, 1a-wedge-shaped flow guide plate, 1b-connecting rib, 1c-flow channel inclination angle, 1d-flow channel width, 2-inducer wheel, 3-impeller, 3a-long blade, 3b-short blade, 3c-notch, 4-shaft, 5-shell, 5a-sealing ring groove, 6-stationary ring, 7-upper end bearing, 8-lower end bearing. Detailed Implementation

[0029] See Figure 1 A structure for improving the cavitation resistance and operational stability of a fuel pump at low flow rates includes a diverter 1, an inducer 2, an impeller 3, a shaft 4, a housing 5, a stationary ring 6, an upper bearing 7, and a lower bearing 8. The diverter 1 and housing 5 are connected. The inducer 2 is an axial-flow impeller, and the impeller 3 is a centrifugal impeller. The inducer 2 and impeller 3 are respectively mounted on the shaft 4, which drives the inducer 2 and impeller 3 to rotate via a key. A stationary ring 6 is placed at the lower end. The lower end of the stationary ring 6 and the bottom end of the shaft 4 are respectively equipped with the upper bearing 7 and the lower bearing 8. Both the lower bearing 7 and the lower bearing 8 are graphite bearings, mainly used for support and thrust. The housing 5 is a volute-shaped collector used to collect the fuel after it has been accelerated by the inducer 2 and impeller 3. The diverter 1 has a diversion channel.

[0030] The flow channel consists of a thin wedge-shaped flow guide plate 1a and a connecting rib, which is used to guide the return fuel to the inlet under low flow conditions to avoid impacting the incoming flow and causing flow turbulence.

[0031] The angle between the flow channel and the axis is generally 5 to 12°, preferably 8°. If the flow channel inclination angle 1c is too small, the inlet flow area will be reduced and the flow capacity will decrease. If the flow channel inclination angle 1c is too large, the fluid loss will be increased and the flow capacity will be reduced.

[0032] The width of the flow channel between the wedge-shaped guide plate 1a and the shell of the guide device 1 is 3-8 mm, preferably 5 mm. If the distance is too large, the inlet flow area will be reduced and the flow capacity will decrease. If the distance is too small, the fluid loss will be increased and the flow capacity will be reduced.

[0033] The ratio of the length of the wedge-shaped guide plate 1a to the lead of the inducer wheel 2 is 0.5 to 1, preferably 0.6. The short guide distance means that the backflow velocity cannot be effectively reduced, and the backflow impacts the guide, increasing the flow loss.

[0034] The maximum thickness of the wedge-shaped drainage piece 1a is preferably 1 to 2.5 mm, more preferably 1.5 mm;

[0035] The wedge-shaped drainage plate 1a is thinner at both ends, with the upper end preferably having a thickness of 0.8 mm and the lower end preferably having a thickness of 0.5 mm, which can reduce the impact loss caused by liquid backflow.

[0036] The top of the flow guide 1 is designed with a U-shaped flow channel. The outlet side of the U-shaped flow channel is parallel to the upper end of the wedge-shaped flow guide plate 1a, which makes it easy for the flow guide 1 to guide the generated liquid back to the inlet of the inducer wheel 2, while reducing flow loss.

[0037] The connecting ribs 1b are evenly distributed along the circumference. The number of connecting ribs 1b is preferably 3 to 8, and more preferably 6. Under low flow conditions, fuel generates vortices upward along the outer edge of the inducer wheel 2. The connecting ribs 1b can act as a separation disc to separate and break the vortex.

[0038] The thickness of the connecting rib 1b is 1-2 mm, and it is connected to the thicker part of the wedge-shaped drainage plate 1a to improve the structural strength;

[0039] The distance between the outer edge of the inducer wheel 2 and the upper cover plate of the impeller 3 and the housing 5 is preferably 0.2mm. This ensures that the rotating parts will not rub against the housing 5 and reduces hydraulic loss, thereby improving the efficiency of the fuel pump.

[0040] The impeller blades are twisted blades, and the blade inlet is pre-rotated to reduce the impact loss at the inlet;

[0041] The impeller 3 is preferably a combination structure of long blades 3a and short blades 3b, which can reduce impeller inlet blockage;

[0042] The impeller blade outlet has a triangular notch 3c, the included angle of the notch 3c is preferably 80° to 150°, more preferably 120°. This notch 3c can eliminate the backflow zone at the outlet, improve the impact of secondary backflow at the outlet on performance, and thus improve the performance in the low flow rate zone.

[0043] The impeller adopts a labyrinth seal, and the sealing ring groove 5a can be located on the upper cover plate of the impeller or on the housing close to the impeller inlet;

[0044] The sealing ring groove 5a is stepped and has a width of 0.5 to 1.5 mm, preferably 1.0 mm. When the impeller rotates, the fuel will generate a throttling effect when passing through the tortuous sealing ring groove 5a, thereby achieving the purpose of preventing leakage, reducing the hydraulic loss of the pump, and improving the performance of the fuel pump.

[0045] The working process of this invention is as follows:

[0046] When the fuel pump is working normally, fuel enters the inducer wheel through the straight section of the siphon. The inducer wheel and impeller, driven by the shaft, accelerate the fuel flow. The accelerated fluid is then pressurized by the casing and delivered to the aircraft fuel system at the required pressure and flow rate. To ensure the normal and stable operation of the shaft during operation, upper and lower bearings are arranged at the bottom of the shaft to provide support and thrust during operation.

[0047] When the fuel pump operates under low flow conditions, backflow and vortices are generated at the edges of the inducer and the inner wall of the housing. The backflow and vortices flow upward through the guide channel of the guide device. When passing through the connecting rib, the vortex is separated and flows back into the inlet of the inducer through the guide channel. This effectively avoids backflow fuel from colliding with inlet fuel, which would cause fuel pump cavitation and reduce performance and stability.

[0048] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A structure for improving the cavitation resistance and operational stability of a fuel pump at low flow rates, characterized in that, Includes an inducer (2), an impeller (3), a shaft (4), a housing (5), a stationary ring (6), an upper bearing (7) and a lower bearing (8). The inducer (2) and the impeller (3) are installed inside the housing (5). The inducer (2) is an axial flow impeller, and the impeller (3) is a centrifugal impeller. The inducer (2) and the impeller (3) are respectively installed on the upper and lower parts of the shaft (4). The shaft (4) drives the inducer (2) and the impeller (3) to rotate through a flat key. A stationary ring (6) is placed at the lower end of the shaft (4). The lower end of the stationary ring (6) and the bottom end of the shaft (4) are respectively equipped with an upper bearing (7) and a lower bearing (8). The housing (5) is used to pressurize the fuel that has been accelerated by the inducer (2) and the impeller (3). A flow guide (1) is installed at the upper end of the shell (5). The main body of the flow guide (1) is a rotating body structure. A straight inlet pipe section is coaxially arranged in the upper part of the main body. An arc groove is formed between the main body and the outer wall of the lower end of the straight pipe section. A ring of wedge-shaped flow guide plates (1a) is fixed on the inner wall of the main body by connecting ribs (1b). A flow channel is formed between the wedge-shaped flow guide plates (1a) and the inner wall of the main body. The upper end of the flow channel is connected to the arc groove, and the upper end of the wedge-shaped flow guide plates (1a) extends into the arc groove to form a U-shaped structure. The outer surface of the wedge-shaped guide plate (1a) is parallel to the inner surface of the main body. The inner surface of the wedge-shaped guide plate (1a) is an arc-shaped convex surface, which makes the thickness of the wedge-shaped guide plate (1a) the largest in the middle and gradually decreases from the middle to the upper and lower ends. The angle (1c) between the outer surface of the wedge-shaped guide plate (1a) and the shaft (4) is 5 to 12°. The maximum thickness of the wedge-shaped guide plate (1a) is 1 to 2.5 mm. The ratio of the axial length of the wedge-shaped guide plate (1a) to the lead of the inducer wheel (2) is 0.5 to 1.

2. The structure for improving the low-flow cavitation resistance and operational stability of a fuel pump according to claim 1, characterized in that, The upper edge of the wedge-shaped guide plate (1a) is parallel to the lower edge of the inlet straight pipe section.

3. The structure for improving the low-flow cavitation resistance and operational stability of a fuel pump according to claim 1, characterized in that, The connecting rib (1b) is a rectangular thin sheet structure. The connecting rib (1b) is evenly and vertically distributed along the circumference, and the surface of the connecting rib is parallel to the axis (4). The thickness of the connecting rib is 1-2 mm, and it is connected to the middle position of the wedge-shaped drainage plate (1a).

4. The structure for improving the low-flow cavitation resistance and operational stability of a fuel pump according to claim 1, characterized in that, The impeller (3) has a long and short blade structure. The blades of the impeller (3) are twisted blades. The blade inlet is pre-rotated to reduce the impact loss at the inlet.

5. The structure for improving the low-flow cavitation resistance and operational stability of a fuel pump according to claim 1, characterized in that, The blade outlet of the impeller (3) is machined with a triangular notch (3c), and the included angle of the notch is 80° to 150°.

6. The structure for improving the low-flow cavitation resistance and operational stability of a fuel pump according to claim 1, characterized in that, The impeller (3) adopts a labyrinth seal, and the sealing ring groove is located on the upper cover plate of the impeller or on the housing close to the inlet of the impeller (3); the sealing ring groove is stepped and has a width of 0.5 to 1.5 mm.

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