WO2021134818A1

WO2021134818A1 - Inducer with high anti-cavitation performance

Info

Publication number: WO2021134818A1
Application number: PCT/CN2020/071060
Authority: WO
Inventors: 付强; 朱荣生; 王秀礼; 龙云; 陈一鸣
Original assignee: 江苏大学
Priority date: 2020-01-03
Filing date: 2020-01-09
Publication date: 2021-07-08
Also published as: CN111188791A

Abstract

An inducer with high anti-cavitation performance. An outer side of an inducer hub (6) is at least provided with two axial flow channels (3, 4) that do not communicate with each other, and any adjacent axial flow channels (3, 4) are separated from each other by a flow channel partition plate (2). The inducer can improve anti-cavitation erosion performance.

Description

An inducer with high anti-cavitation performance

Technical field

The invention relates to the field of fluid machinery, in particular to an inducer with high anti-cavitation performance.

Background technique

Inducer wheels are mostly used in aviation, aerospace, refrigeration and other occasions that require high cavitation. In the field of aviation and aerospace, because aerospace vehicles need to work at high altitudes or space far away from the ground, and restricted by the space size and structural quality of the aircraft, the structural size and quality of the propellant supply system are strictly limited. In order to minimize the size and quality of the structure, the propellant pump needs a higher speed, and in order to reduce the quality and scale of the tank pressurization system, the propellant tank needs a lower pressure. According to the characteristics of high speed and low inlet pressure of the propellant pump in the propellant supply system, the propellant pump is required to have very high anti-cavitation performance.

At present, the method of adding an inducer in front of the centrifugal impeller is usually used to improve the anti-cavitation performance of the pump, but the improvement is limited, and when the working conditions deviate from the design point far away, it is limited by the anti-cavitation performance of the inducer itself. Its anti-cavitation performance still does not meet the requirements of normal operation under low inlet pressure. In aerospace jet engines, it is necessary to pressurize and transport extremely low temperature fluids such as liquid hydrogen or liquid oxygen. In order to maintain its suction performance, an inducer is required. In the liquid rocket engine turbo pump, in order to obtain a smaller mass and a larger thrust-to-mass ratio, the inducer in the high-speed inducer centrifugal pump often works under potential cavitation conditions. Although the potential cavitation in the flow channel will not have a significant impact on the steady-state output parameters of the pump, the head, power and efficiency, it will change the dynamic characteristics of the system and cause the pressure and flow of the hydraulic system to self-oscillate under certain conditions. Severe cavitation oscillations will reduce reliability and even cause damage.

A foreign patent discloses a design of an inducer used to push high-viscosity fluid into a centrifugal pump. A very close gap is formed between the spiral blade of the inducer and the shell of the inducer, and the spiral blade is configured to allow the fluid to pass through. When the device flows to the pump, the pressure is increased to solve the problem of the fluid rotating with the inducer blades. However, the efficiency of the entire device is not high and cannot meet the needs of some occasions.

Foreign patents disclose that the inducer is arranged in multiple stages, and the rotation direction of the multi-stage inducer is changed by increasing the slope of the helix of the inducer, and the rotational momentum is removed, thereby reducing the cavitation margin. At the same time, the inner wall of the casing is provided with a spiral groove opposite to the direction of rotation of the inducer, so that the vortex flows in the groove instead of in the tip clearance, thereby reducing the possibility of the fluid generating tip cavitation. However, the performance curve of this technology becomes unstable under the occasion of high specific speed, which is worthy of discussion.

The work done by the blades of the inducer on the medium is achieved by the lift of the blade profile, and does not rely on centrifugal force at all. When the inducer rotates, the blade produces a certain centrifugal force, which causes the medium to produce a radial flow component along the blade. This radial flow makes its anti-cavitation performance worse and the unit performance deteriorates. At the same flow rate, the larger the geometric size of the inducer, the stronger the radial centrifugal force effect, which is also an important factor restricting the inducer to further improve the anti-cavitation performance and enlargement of the inducer. If the above problems are to be solved, it is necessary to eliminate or suppress the centrifugal force and radial flow of the blades.

In the prior art, the impeller of a centrifugal pump is designed with double flow channels. The centrifugal impeller uses centrifugal force to do work on the medium to convert kinetic energy into pressure energy. The work of the centrifugal impeller on the medium is realized by the centrifugal force generated by the blades. The setting of dual-channels strengthens the radial flow in the impeller channel, thereby strengthening the centrifugal force of the centrifugal impeller. The setting of the dual-channel impeller reduces the pressure pulsation, weakens the impact of the outflow, and reduces the impact of dynamic and static interference, but it will Increasing the displacement coefficient results in the blockage of the impeller channel of the centrifugal pump and the increase of the flow rate, which leads to the decrease of its anti-cavitation performance.

As shown in Figure 1, the traditional inducer is a high specific speed impeller. There is only one axial flow channel, and there is no centrifugal force that promotes the separation of liquid and air bubbles. Its external characteristic is that its performance decreases during cavitation. Slow, no obvious sudden decline stage, that is, no serious impact on performance. The characteristic value to measure the cavitation performance of the rust guide wheel is the specific cavitation speed C, as shown in the following formula:

In the formula: n----rotation speed of inducer, unit r/min;

Q----The flow through the inducer, in m ³ /s;

NPSH _R ----The cavitation margin of the inducer, in m.

It can be seen from the above formula that the higher the requirement for anti-cavitation performance, that is _{, the lower the required NPSH R, the} greater the cavitation specific speed C. Due to the limitation of the existing technical level, it is difficult to greatly increase the C value by using the traditional inducer structure.

Summary of the invention

Aiming at the deficiencies in the prior art, the present invention provides an inducer with high anti-cavitation performance, which improves the anti-cavitation performance by increasing the number of multiple axial flow channels.

The present invention achieves the above-mentioned technical objects through the following technical means.

An inducer with high anti-cavitation performance. At least two layers of axial flow passages are arranged on the outer side of the hub of the inducer, and any adjacent axial flow passages are separated by a flow passage partition plate.

Further, at least one blade is provided in any of the axial flow passages, and the exit area of any of the axial flow passages is less than or equal to the inlet area.

Further, the sweeping and rounding treatment of the inlet edge of the blade has a sweep angle ranging from 10° to 180°, which can further improve the anti-cavitation performance of the induced impeller.

Further, the blade is a spiral blade, and the pitch of the spiral blade is a constant pitch or a variable pitch or a combination of the constant pitch and the variable pitch.

Furthermore, the two ends of the flow channel dividing plate are respectively provided with a flow guide structure to prevent the tip leakage and further improve the anti-cavitation performance.

Further, the axial flow passage includes an outer axial flow passage and at least one inner axial flow passage; the outer axial flow passage is located on the outer side of the inducer, and at least one layer of the inner axial flow passage is located on the outer side Between the axial flow channel and the hub.

Further, in the outer axial flow channel, the outer radius of the inlet side of the blade is greater than or equal to the outer radius of the outlet side of the blade, and the outer flow line of the outer blade on the outer axial flow channel is equal to the axis line The angle β is 0°～45°.

Further, the cross-sectional flow area of the inner axial flow channel of each layer decreases according to the increase of the distance to the hub.

Further, the outer flow line of the outer blade on the outer axial flow channel is provided with an outer rim cover plate to prevent the tip leakage and further improve the anti-cavitation performance.

Further, the hub structure of the inducer is a hollow structure.

The beneficial effects of the present invention are:

1. The inducer with high anti-cavitation performance of the present invention has the axial flow channel of the inducer set into a multi-layer axial flow channel, and an additional flow channel partition plate is added between adjacent axial flow channels, which can be effective It suppresses the centrifugal force of the inducer blade and the radial flow in the inducer, thereby improving its anti-cavitation performance.

2. In the high anti-cavitation inducer of the present invention, the cross-sectional flow area of the inner axial flow channel of each layer decreases according to the increase of the distance to the hub, so that the degree of twisting of the blade is reduced, so that The blades are designed more reasonably, and are more consistent with the working mechanism of the inducer, which reduces the design error, which has a better effect on restraining the radial effect of the blades on the medium.

3. In the inducer with high cavitation resistance of the present invention, the multi-layer axial flow channel structure can reduce the flow rate through each axial flow channel and obtain a lower cavitation margin, thereby making the whole induction The anti-cavitation performance of the wheel.

4. In the inducer with high cavitation resistance of the present invention, the two ends of the flow channel partition plate are respectively provided with a flow guide structure, and the blade inlet edge is swept back and rounded, which can further improve the resistance of the present invention. Cavitation performance.

5. In the inducer with high anti-cavitation performance of the present invention, the blade outlet edges in different axial flow channels are arranged at a staggered angle, which can improve the uniformity of the outflow of the inducer.

Description of the drawings

Fig. 1 is a schematic diagram of the structure of a traditional inducer in the prior art.

Fig. 2 is an axial projection view of the inducer according to embodiment 1 of the present invention.

Fig. 3 is a schematic diagram of the axial flow channel area of the inducer according to the embodiment 1 of the present invention.

Fig. 4 is an axial cross-sectional view of the inducer according to Embodiment 1 of the present invention.

Fig. 5 is a left side view of Fig. 2.

Fig. 6 is an axial projection view of the inducer according to Embodiment 2 of the present invention.

FIG. 7 is an axial projection view of the inducer according to Embodiment 3 of the present invention.

In the picture:

1- Hub axial streamline; 2- runner divider A; 3- axial runner A; 301- blade inlet side A; 302- blade A; 303- blade outlet side A; 304- inlet area A 305-outlet area A; 4-axial flow path B; 401-blade inlet side B; 402-blade B; 403-blade outlet side B; 404-inlet area B; 405-outlet area B; 5-outer Streamline; 6-wheel hub; 7-outer rim cover plate; 8-axial flow channel C; 9-flow channel separator B.

Detailed ways

The present invention will be further described below with reference to the drawings and specific embodiments, but the protection scope of the present invention is not limited to this.

Example 1 is an inducer with two layers of axial flow channels. As shown in Figures 2, 3 and 5, the inducer with high cavitation resistance according to the present invention, the inducer hub 6 is made of the The hub axial flow line 1 is a central area formed by rotating 360° around the axis of the inducer. The outer side of the inducer hub 6 is provided with an axial flow channel A 3 and an axial flow channel B 4 which are not connected to each other, and the axial flow The channel A 3 and the axial flow channel B 4 are separated by a channel separating plate A 2. The axial flow passage A 3 is the inner axial flow passage, and the axial flow passage B 4 is the outer axial flow passage. The outer axial flow passage is located on the outside of the inducer, and the inner axial flow passage is located on the outer shaft. Between the surface runner and the wheel hub. The included angle α between the hub axial surface streamline 1 and the axial center line is 0° to 45°, so that the water inlet area can be increased and the flow velocity can be reduced. The water outlet area of the axial flow channel A or the axial flow channel B is smaller than the water inlet area, that is, the water outlet area A 305 is smaller than the water inlet area A 304, and the water outlet area B 405 is smaller than the water inlet area B 404. At least one blade is provided in each axial flow channel. The blades in the same axial flow channel are evenly arranged in the flow channel. In order to improve the anti-cavitation performance, the blade inlet side A 301 and the blade inlet side B 401 are swept back and rounded, and the sweep angle ranges from 10° to 180°. The blade 3 is arranged between the outer side of the hub 6 and the inner side of the flow channel dividing plate A 2, and the blade 4 is arranged on the outer side of the flow channel dividing plate A 2. When the number of blades in the same axial flow channel is not less than 2, the blades are evenly arranged in the flow channel. When the medium enters the outer edge of the inlet, the medium on the hub side has accepted the action of the blade in advance and moved to the outer edge, thereby improving the anti-cavitation conditions at the outer edge inlet where cavitation is most likely to occur. In order to improve the uniformity of the flow out of the inducer, the blade inlet edges and blade outlet edges in the different axial flow channels are arranged in a staggered manner, that is, the blade outlet edge A 303 and the axial flow channel B in the axial flow channel A The blade exit side B 403 in the middle is staggered.

As shown in FIG. 4, the blade is a spiral blade, and the pitch of the spiral blade is a constant pitch or a variable pitch or a combination of the constant pitch and the variable pitch. The two ends of the flow channel dividing plate A 2 are respectively provided with a diversion structure, in order to reduce the resistance to the water flow. The diversion structure is a pointed streamline structure.

As shown in Figure 2, in the axial flow channel A, the inner radius R _{1 of} the blade inlet side A 301 is less than or equal to the inner radius R _{3 of} the blade outlet side A 303; In the flow channel B, the outer radius R _{2 of} the blade inlet side B 401 is greater than or equal to the outer radius R _{4 of} the blade outlet side B 403; the outer flow line 5 of the outer blade on the axial flow channel B is equal to The included angle β of the axis line is 0°～45°.

Taking an inducer with two axial flow passages as an example, the cavitation specific speed C value of the axial flow passage is shown in the following formula:

Where:

n----rotation speed of inducer, unit r/min;

Q ₁ ----The flow through the axial flow channel A, in m ³ /s;

Q ₂ ----The flow through the axial flow channel B, in m ³ /s;

NPSH _R ----The cavitation margin of the inducer, in m.

_{If the flow rate Q 1} passing through the axial flow channel A is the same as the flow rate Q _{2 of the} axial flow channel B, the axial flow channel cavitation specific rotation speed C value is shown in the following formula.

Compared with the traditional single axial flow channel, the flow rate through each axial flow channel is significantly reduced. Under the condition of maintaining the same C value, a lower NPSH _R can be obtained, which also makes the entire inducer The cavitation ratio C value can be greatly improved.

Embodiment 2 is an inducer with 3 layers of axial flow channels that are not connected to each other. As shown in FIG. 6, the outer side of the hub 6 of the inducer is provided with an axial flow channel A 3, an axial flow channel B 4, and an axial surface. Flow channel C 8, the axial flow channel A 3 and the axial flow channel C 8 are separated by a flow channel dividing plate B 9, and the axial flow channel B 4 and the axial flow channel C 8 are separated by a flow channel Board A 2 is isolated. The axial flow passage A 3 and the axial flow passage C 8 are both inner axial flow passages, and the axial flow passage B 4 is the outer axial flow passage. The outer axial flow passage is located on the outside of the inducer. The surface flow channel is located between the outer axial surface flow channel and the hub. The blade 3 is arranged between the streamline side 1 of the hub axis and the inner side of the flow channel dividing plate B9, the blade 8 is arranged between the flow channel dividing plate B 9 and the flow channel dividing plate A 2, and the blade 4 is arranged in the flow channel Outside of partition A2. The cross-sectional flow area of the inner axial flow channel of each layer decreases as the distance from the hub increases. It can be seen from the figure that the cross-sectional flow area of the axial flow channel A 3 is larger than the cross-sectional flow area of the axial flow channel C 8.

Embodiment 3 is shown in Fig. 7, on the basis of embodiment 1, the outer flow line 5 of the axial flow channel B 4 is provided with an outer rim cover plate 7 to prevent the tip leakage and further improve the anti-cavitation performance.

In the actual operation process, the inducer pressurizes the propellant to generate a certain head to increase the inlet pressure, avoid cavitation, and improve the cavitation performance. However, during the high-speed operation of the inducer, its operating conditions often change, especially when the internal partial pressure drops below the saturated vapor pressure and cavitation occurs, which will lead to strong cavitation inside the inducer and cause performance. Decrease and strengthen the vibration of the system structure, thereby affecting the reliability of the entire device system and the service life of the inducer.

Take the cavitation process on blade A 302 as an example. Under the condition of large NPSH, there is no cavitation in the flow field, and the flow field at the inlet side A 301 of the circumfluence blade appears to be separated by a surface layer and forms a hysteresis. Stop zone: When the cavitation margin is equal to the cavitation margin of the device, a vortex area is generated in the stagnation zone. As the cavitation margin decreases, cavitation occurs in the vortex and continues to increase, the cavitation zone begins to expand, and the noise increases; as the cavitation margin decreases, the cavitation in the vortex zone separates from the blades and enters the mainstream, leading to The fluid medium in the wheel forms an unsteady jet state, and periodically implicated cavitation appears on the surface of the blade A 302. At this time, the head and power begin to decrease, and the noise and structural vibration are the largest; as the cavitation margin is further reduced, the cavitation The bubble fills the axial flow channel A, and the fluid forms a stable jet state. At this time, the noise and structural vibration quickly drop to the state when no cavitation occurs, and the device head and power drop drastically. The cavitation bubble is closed in the inducer and continues to elongate. Its closure occurs at a position farther and farther downstream from the inducer cascade. After the transition to the separated flow condition, the noise and vibration in the pump decrease sharply, and the inlet The vortex at the location tends to disappear, and the main flow fills the entire flow section.

In the present invention, at least two layers of axial flow passages are provided on the outside of the inducer hub, and any adjacent axial flow passages are separated by a flow passage partition plate. The bubbles generated in the outer flow line 5 are in the axial direction. In the process of forward movement, the bubbles are controlled at a local position on the outer edge, and at the same time, they slowly condense in the multiple flow passages of the inducer and then collapse. There is no blockage of the entire flow passage, which delays the development of cavitation and weakens the effect of cavitation. The degree of influence of the inducer's supercharging ability

The embodiments are the preferred embodiments of the present invention, but the present invention is not limited to the above-mentioned embodiments. Without departing from the essence of the present invention, any obvious improvements, substitutions or substitutions can be made by those skilled in the art. The variants all belong to the protection scope of the present invention.

Claims

An inducer with high anti-cavitation performance, characterized in that at least two layers of axial flow passages are provided on the outer side of the hub of the inducer, and any adjacent axial flow passages pass through a flow passage separation plate (2, 9) Isolation.
The inducer with high anti-cavitation performance according to claim 1, wherein at least one blade is provided in any of the axial flow passages, and the outlet area of any of the axial flow passages is less than or equal to the inlet area.
The inducer with high anti-cavitation performance according to claim 2, wherein the inlet edge of the blade is swept and rounded, and the swept angle ranges from 10° to 180°.
The inducer with high anti-cavitation performance according to claim 2, wherein the blades are spiral blades, and the pitch of the spiral blades is equal or variable pitch or a combination of equal and variable pitch.
The inducer with high anti-cavitation performance according to claim 1, characterized in that the two ends of the flow channel dividing plate (2, 9) are respectively provided with a diversion structure.
The inducer with high anti-cavitation performance according to any one of claims 1-5, wherein the axial flow channel comprises an outer axial flow channel and at least one inner axial flow channel (3, 8 ); The outer axial flow passage is located outside the inducer, and at least one layer of the inner axial flow passage (3, 8) is located between the outer axial flow passage and the hub.
The inducer with high anti-cavitation performance according to claim 6, wherein in the outer axial flow channel, the outer radius of the inlet side of the blade is greater than or equal to the outer radius of the outlet side of the blade; The included angle β between the outer flow line (5) of the outer blade on the outer axial flow channel and the axial center line is 0°-45°.
The inducer with high anti-cavitation performance according to claim 6, characterized in that the cross-sectional flow area of the inner axial flow channel (3, 8) of each layer decreases according to the increase of the distance to the hub.
The inducer with high anti-cavitation performance according to claim 6, characterized in that the outer flow line (5) of the outer blade on the outer axial flow channel is provided with an outer rim cover (7).
The inducer with high anti-cavitation performance according to claim 9, characterized in that the structure of the hub (6) of the inducer is a hollow structure.