Blade tip water spraying device and method for improving the stability of axial flow pump

Abstract

The present invention discloses a blade top water spraying device for improving the stability of an axial flow pump, comprising a booster pump, the booster pump being connected to a diversion box via a pipeline, the side wall of the diversion box being connected to a plurality of hoses, the plurality of hoses being evenly arranged circumferentially on the side wall of the diversion box; one end of each hose extending into the interior of the diversion box, and the other end being provided with a nozzle device. The present invention also discloses a blade top water spraying method for improving the stability of an axial flow pump, specifically: connecting the diversion box and the booster pump via a pipeline, tightly connecting the nozzle device to the rim end wall of the axial flow pump, and then stably spraying the water source into the impeller channel through the nozzle. The blade top water spraying device of the present invention installs the nozzle evenly circumferentially in the rim end wall of the axial flow pump, and uses the high-speed jet to drive the leakage vortex of the blade top of the axial flow pump to smoothly flow out of the impeller channel, thereby reducing the blockage of the blade top of the axial flow pump.

Description

Technical Field

[0001] The present invention belongs to the technical field of fluid mechanical equipment, and in particular relates to a blade tip water spraying device for improving the stability of an axial flow pump, and also relates to a blade tip water spraying method for improving the stability of an axial flow pump. Background Art

[0002] Axial flow pumps, with their low head, high flow rate, and high efficiency, are widely used in fields such as agricultural irrigation and ship propulsion. However, in actual operation, due to the presence of a hump in the flow-head curve of axial flow pumps, especially when operating at low flow rates, the head drops sharply, making rotational stall prone to occur, leading to hydraulic instability. When an axial flow pump stalls, vibration and noise levels increase, and efficiency plummets. Frequent entry into or prolonged operation in the instability zone can cause blade breakage, seriously affecting the safe and stable operation of the unit. Therefore, establishing a flow control method that can improve the stable operating range of axial flow pumps has become an urgent need to ensure their safe operation.

[0003] To address operational instability in fluid machinery, researchers have investigated various stabilization measures, including adjustable guide vanes, blade angle and clearance adjustments, and endwall treatments. Endwall treatments utilize grooves and slits to suppress the development of tip leakage vortices, effectively stabilizing the performance of axial-flow pumps. However, these treatments, which affect design-point efficiency and can generate incidental cavitation, currently hinder engineering application.

[0004] As an effective flow control method, tip water injection is widely used in compressors. Numerous results have shown that tip water injection can effectively improve the stable operating range of compressors without reducing peak efficiency. However, in the field of axial flow pumps, relevant flow control methods are currently lacking, especially the design of experimental devices for implementing tip water injection, and current research is relatively scarce. Summary of the Invention

[0005] The purpose of the present invention is to provide a blade top water spraying device for improving the stability of an axial flow pump, thereby solving the problem that the existing axial flow pump is prone to sudden drop in head when operating under low flow conditions.

[0006] Another object of the present invention is to provide a blade tip water injection method for improving the stability of an axial flow pump.

[0007] The technical solution adopted by the present invention is a blade top water spraying device for improving the stability of an axial flow pump, which includes a booster pump, which is connected to a diversion box through a pipeline, and the side wall of the diversion box is connected to multiple hoses, which are evenly arranged on the side wall of the diversion box along the circumferential direction; one end of each hose extends into the interior of the diversion box, and the other end is provided with a nozzle device.

[0008] The present invention is also characterized in that:

[0009] The nozzle device includes a sealing cover, a threaded hole is opened at the center of the sealing cover, the sealing cover is threadedly connected to the hose through the threaded hole, and the end of the hose is connected to the bottom of the threaded hole; the bottom of the sealing cover is connected to a water filling chamber, and a square through hole is provided at the center of the water filling chamber; the bottom of the water filling chamber is connected to a nozzle seat, and a crescent-shaped nozzle is provided at the center of the nozzle seat, the inlet of the crescent-shaped nozzle is located at the bottom of the square through hole, and the outlet of the crescent-shaped nozzle is located at the bottom of the nozzle seat, and the shape of the crescent-shaped nozzle from the inlet to the outlet is gradually reduced.

[0010] The three-dimensional structure of the crescent-shaped nozzle is obtained by rotating the two-dimensional geometric line. The two-dimensional geometric body is composed of two lines, including the first arc and the second arc. The radius of the first arc and the second arc are both R. The second arc is obtained by translating the first arc. The first arc and the second arc are tangent to each other at the end wall of the rim. The position of the second arc directly determines the throat height of the nozzle. h , h The size is controlled to be 2 to 6 times the tip clearance. The throat height is expressed as the minimum distance between the second arc and the first arc at the tangent point. Therefore, before determining the position of the second arc, the throat height needs to be determined first. Then, the first arc is translated to the right to the tangent point of the second arc to determine the position of the second arc.

[0011] The two-dimensional geometric line is centered on the central axis of the axial flow pump impeller. By sweeping left and right, a nozzle with a jet direction of 90° to the front line of the impeller leading edge can be obtained. Then, a crescent-shaped nozzle can be obtained by rotating through the center of the nozzle.

[0012] A plurality of through holes are provided on the upper surface of the sealing cover.

[0013] A pressure sensor is installed on the top of the diverter box.

[0014] The pipeline connecting the booster pump and the diversion box is provided with a solenoid valve, a flow meter and a pulse valve.

[0015] Each hose is provided with a valve.

[0016] Another technical solution adopted by the present invention is a method for spraying water on the blade tip to improve the stability of the axial flow pump, specifically:

[0017] Connect the diversion box and the booster pump through a pipeline, connect the booster pump outlet to the solenoid valve inlet to control the real-time flow of the pipeline; connect the solenoid valve outlet to the flow meter inlet to measure the real-time flow of the pipeline; connect the flow meter outlet to the pulse valve inlet, and connect the pulse valve outlet to the diversion box. Tightly connect the nozzle device to the rim end wall of the axial flow pump, and then spray the water source steadily into the impeller channel through the nozzle.

[0018] The beneficial effects of the present invention are as follows: the blade tip water spray device of the present invention for improving the stability of an axial flow pump has nozzles evenly installed circumferentially in the rim end wall of the axial flow pump, and uses a high-speed jet to drive the leakage vortex of the axial flow pump blade tip to smoothly flow out of the impeller channel, thereby reducing the blockage of the axial flow pump blade tip. On the other hand, the blade tip water spray device of the present invention can be used to study the influence of different water spray flow rates, water spray frequencies, water spray speeds, and water spray quantities on the stability margin and efficiency of the axial flow pump. After adopting the blade tip water spray device of the present invention, the optimal water spray parameters can be obtained, and the problem of a sharp drop in head when the axial flow pump is operating under low flow conditions can be effectively solved. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Schematic diagram of the structure of the blade top water spraying device for improving the stability of the axial flow pump according to the present invention;

[0020] Figure 2 It is a schematic structural diagram of a nozzle device in a blade top water spraying device for improving the stability of an axial flow pump according to the present invention;

[0021] Figure 3 This is a cross-sectional view of the internal structure of the nozzle device in the blade top water spraying device for improving the stability of the axial flow pump according to the present invention along the axial direction;

[0022] Figure 4 It is a two-dimensional geometric line diagram of the nozzle in the blade top water spraying device for improving the stability of the axial flow pump according to the present invention;

[0023] Figure 5 2. It is a schematic diagram of the assembly structure of the nozzle device of the blade top water spraying device for improving the stability of the axial flow pump according to the present invention;

[0024] Figure 6 This is a schematic diagram of the connection between the nozzle device and the axial flow pump rim end wall in the blade top water spraying device for improving the stability of the axial flow pump according to the present invention;

[0025] Figure 7 This is a graph showing the head characteristic curve of the steady-state jet flow of the blade top water spraying device used to improve the stability of the axial flow pump according to the present invention;

[0026] Figure 8 The present invention is a pulse jet head characteristic curve diagram of the blade top water spray device for improving the stability of the axial flow pump.

[0027] In the figure, 1. diversion box, 2. hose, 3. nozzle device, 4. sealing cover, 5. threaded hole, 6. water filling chamber, 7. through hole, 8. square through hole, 9. nozzle holder, 10. nozzle. DETAILED DESCRIPTION

[0028] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0029] Example 1

[0030] The present invention is used to improve the stability of the axial flow pump blade top water spray device, such as Figure 1 As shown, it includes a booster pump, which is connected to a diversion box 1 through a pipeline. The pipeline is provided with a solenoid valve, a flow meter and a pulse valve. The diversion box 1 is cylindrical and can withstand a maximum pressure of 1 MPa. A pressure sensor is installed on the top of the diversion box 1 to monitor the water spray pressure, thereby maintaining the operating stability of the water spray device.

[0031] The booster pump outlet is connected to the solenoid valve inlet to control the real-time flow of the pipeline; the solenoid valve outlet is connected to the flow meter inlet to measure the real-time flow of the pipeline. The measurement range is 4-60m 3 / h; the flow meter outlet is connected to the pulse valve inlet, and the pipeline is opened and closed by changing the duty cycle of the pulse valve, thereby realizing steady-state jet and pulse jet of blade tip water spray.

[0032] The side wall of the diverter box 1 is connected to multiple hoses 2, which are evenly arranged circumferentially on the side wall of the diverter box 1; each hose 2 is provided with a valve; preferably there are 6 hoses 2, with a length of 2m and a diameter of 0.02m; one end of each hose 2 extends into the interior of the diverter box 1, and the other end is provided with a nozzle device 3; after the water flows into the diverter box 1 and is fully mixed, it is ejected at high speed through the nozzle device 3.

[0033] like Figure 2 and Figure 3 As shown, the nozzle device 3 includes a sealing cover 4, a threaded hole 5 is opened at the center of the sealing cover 4, and its specifications refer to the national standard NPT1 / 2 standard model. The sealing cover 4 is threadedly connected to the hose 2 through the threaded hole 5, and the end of the hose 2 is connected to the bottom of the threaded hole 5; it is tightly connected to the hose 2 outlet on the side wall of the diversion box 1 through the threaded hole, and the junction between the two is wrapped with raw tape to ensure sealing; a plurality of through holes 7 are provided on the upper surface of the sealing cover 4 for fixing the nozzle device to the rim end wall; the bottom of the sealing cover 4 is connected to a water filling chamber 6, and the water filling chamber 6 A square through hole 8 is provided at the center; a nozzle seat 9 is connected to the bottom of the water filling chamber 6, and a crescent-shaped nozzle 10 is provided at the center of the nozzle seat 9. The inlet of the crescent-shaped nozzle 10 is located at the bottom of the square through hole 8, and the outlet of the crescent-shaped nozzle 10 is located at the bottom of the nozzle seat 9. The shape of the crescent-shaped nozzle 10 from the inlet to the outlet is gradually contracting; the Coanda effect is used at the outlet of the crescent-shaped nozzle 10 to make the outlet water flow and the rim end wall flow close to the wall. After the water enters the water filling chamber 6 and is fully mixed, it is ejected at high speed through the crescent-shaped nozzle 10.

[0034] The sealing cover 4, the water filling chamber 6, and the nozzle seat 9 are all rectangular; the sealing cover 4 is equal in size to the water filling chamber 6; the length of the nozzle seat 9 is less than the length of the water filling chamber 6;

[0035] Example 2

[0036] The three-dimensional structure of the crescent-shaped nozzle 10 is obtained by rotating a two-dimensional geometric line. The two-dimensional geometric body is composed of two lines, including a first arc and a second arc. Figure 4 As shown, the radii of the first arc and the second arc are both R, and the second arc is obtained by translating the first arc. The first arc and the second arc are both tangent to the rim end wall in order to ensure that the water flow at the nozzle outlet can flow along the rim end wall.

[0037] The specific process of determining the line types of the first arc and the second arc is as follows:

[0038] First, determine the position of the first arc. For the first arc: with the origin (0,0) as the center and R as the radius, a full circle can be obtained. The fourth quadrant arc is the contour line of the first arc.

[0039] Then, determine the position of the second arc; the position of the second arc directly determines the throat height of the nozzle h , h The size of the throat should be controlled at 2 to 6 times the tip clearance. Too large a throat height will result in a decrease in nozzle outlet velocity. The throat height is expressed as the minimum distance between the second arc and the first arc at the tangent point, such as Figure 4 As shown, before determining the position of the second arc, it is necessary to first determine the throat height, and then translate the first arc to the right to the tangent point of the second arc to determine the position of the second arc.

[0040] The distance between the two ends of the inlet of the crescent-shaped nozzle 10 is determined by the second arc. The throat height is determined, and the second arc is determined, that is, the distance between the two ends of the nozzle inlet can be determined.

[0041] The outlet position of the crescent-shaped nozzle 10 should be located before the leading edge of the impeller, so as to ensure that the nozzle can fully act on the impeller head position.

[0042] The two-dimensional geometric line is centered on the central axis of the axial flow pump impeller. By sweeping left and right, a nozzle with a jet direction of 90° to the front line of the impeller leading edge can be obtained. Then, by rotating the nozzle center, a crescent-shaped nozzle of the present invention can be obtained, that is, the jet at the crescent-shaped nozzle outlet forms a certain angle with the front line of the impeller leading edge, which can ensure that the jet acts on the impeller channel.

[0043] Schematic diagram of the structural assembly of the crescent-shaped nozzle, as shown in Figure 5 As shown, the axial chord length of the axial flow pump blade tip is Ca=40.2mm, the nozzle outlet jet position is 18%Ca away from the blade leading edge, the left side of the nozzle device is 9mm away from the center of the bolt, and the distance from the center of the nozzle device is 39.5mm. The center of the sealing cover is national standard NPT1 / 2, with a thickness of 20mm, and the size of the square through hole is 28mm*24mm.

[0044] Example 3

[0045] The present invention provides a blade tip water spraying method for improving the stability of an axial flow pump, specifically comprising:

[0046] like Figure 6 As shown, the diverter box 1 is connected to the booster pump through a pipeline, the booster pump outlet is connected to the solenoid valve inlet to control the real-time flow of the pipeline; the solenoid valve outlet is connected to the flow meter inlet to measure the real-time flow of the pipeline; the flow meter outlet is connected to the pulse valve inlet, and the pulse valve outlet is connected to the diverter box 1, and the nozzle device 3 is tightly connected to the rim end wall of the axial flow pump, and then the water source is stably sprayed into the impeller channel through the nozzle.

[0047] Example 4

[0048] Relying on the axial flow pump closed cycle test bench, the blade top water spraying device for improving the stability of the axial flow pump of the present invention is specifically described. The main design parameters of the axial flow pump are shown in Table 1:

[0049]

[0050] The key parameters for testing the hydraulic characteristics of an axial flow pump include speed, flow rate, inlet and outlet pressures, torque, and power. The inlet and outlet pressures are measured using pressure transmitters installed at the pump's inlet and outlet ports. The flow rate is measured using an electromagnetic flowmeter installed in the outlet pipeline. Torque and power are measured using a torque-tachometer installed between the pump and motor. All test equipment is connected to a control system that continuously records measured system data. During the experiment, the system flow rate is varied by controlling the outlet regulating valve to obtain the pump's characteristic curve.

[0051] The blade tip water spray device of the present invention, used to improve the stability of an axial flow pump, is used to simultaneously test the external characteristics of the axial flow pump. While testing the external characteristics of the axial flow pump, the blade tip water spray device is activated. By setting the pressure of the jet system and adjusting and changing the opening of the jet system's solenoid valve or the duty cycle of the pulse valve, axial flow pump blade tip water spray tests can be conducted at different spray flow rates and spray frequencies. Furthermore, by opening or closing the valve on the sidewall hose of the diverter box, axial flow pump blade tip water spray tests can be conducted at different nozzle numbers.

[0052] During the experiment, the following parameters were simultaneously recorded: pressure at the axial flow pump inlet and outlet, the jet system, flow rates at the axial flow pump outlet and the jet system, and the motor speed and torque. This data was transmitted to a display via a data transmission line and processed using the following formula to obtain the external characteristic curves of the axial flow pump with and without the tip water injection device for improving axial flow pump stability according to the present invention.

[0053] Axial flow pump head H and efficiency η The calculation formula is as follows:

[0054]

[0055] Where, and Respectively represent the test section readings of the inlet and outlet elbows of the inlet pipe, the unit is Pa; Z is the vertical height difference between the inlet and outlet sections of the pump; ρ is the density of the fluid in kg / m 3 ; g is the acceleration due to gravity, in m / s 2 ; Q is the flow rate through the pump, in m 3 / h; M is the spindle torque, in N·m; ω The spindle speed is in rad / s.

[0056] The blade top water spraying device for improving the stability of the axial flow pump of the present invention can be used to conduct experimental research on different water spraying flow rates, water spraying frequencies, water spraying speeds and quantities. The water spraying flow rate research range is 0~18m 3 / h; the research range of the number of water sprays is 0~6, and research on different arrangements with the same number can also be carried out. The research range of the water spray frequency is 0~∞Hz.

[0057] Example 5

[0058] Figure 7 The jet flow rate is given as 18m 3 / h, the number of nozzles is 6, and the jet frequency is ∞ Hz. This is a comparison of the lift of the axial flow pump under steady-state jet flow and that without the blade top water spraying device of the present invention. It can be found that the use of the blade top water spraying device of the present invention eliminates the hump phenomenon of the axial flow pump and greatly improves the stable operating range of the axial flow pump.

[0059] Example 6

[0060] Figure 8 The jet flow rate is given as 14m 3 / h, the number of nozzles is 6, the jet frequency is 0.5Hz, that is, the head comparison chart of the axial flow pump under pulse jet and the case without the blade top water spraying device of the present invention. It can be found that the use of the blade top water spraying device of the present invention eliminates the hump phenomenon of the axial flow pump and greatly improves the stable operation range of the axial flow pump.

Claims

1. A blade top water spraying device for improving the stability of an axial flow pump, characterized in that: The invention comprises a booster pump, wherein the booster pump is connected to a diversion box (1) through a pipeline, and the side wall of the diversion box (1) is connected to a plurality of hoses (2), and the plurality of hoses (2) are evenly arranged on the side wall of the diversion box (1) along the circumferential direction; one end of each hose (2) extends into the interior of the diversion box (1), and the other end is provided with a nozzle device (3), and the nozzle device (3) comprises a sealing cover (4), and a threaded hole (5) is provided at the center of the sealing cover (4), and the sealing cover (4) and the hose (2) are threadedly connected through the threaded hole (5), and the end of the hose (2) is connected to the bottom of the threaded hole (5); the bottom of the sealing cover (4) is connected to a water filling chamber (6), and a square through hole (8) is provided at the center of the water filling chamber (6); the water filling chamber (6) is provided with a square through hole (8); The bottom of the chamber (6) is connected to a nozzle seat (9), and a crescent-shaped nozzle (10) is provided at the center of the nozzle seat (9). The inlet of the crescent-shaped nozzle (10) is located at the bottom of the square through hole (8), and the outlet of the crescent-shaped nozzle (10) is located at the bottom of the nozzle seat (9). The shape of the crescent-shaped nozzle (10) from the inlet to the outlet is a tapered shape. The three-dimensional structure of the crescent-shaped nozzle (10) is obtained by rotating a two-dimensional geometric line. The two-dimensional geometric body is composed of two lines, including a first arc and a second arc. The radii of the first arc and the second arc are both R. The second arc is obtained by translating the first arc. The first arc and the second arc are both tangent to each other at the end wall of the wheel rim. The position of the second arc directly determines the throat height of the nozzle. h , h The size is controlled to be 2 to 6 times the tip clearance. The throat height is expressed as the minimum distance between the second arc and the first arc at the tangent point. Therefore, before determining the position of the second arc, the throat height needs to be determined first. Then, the first arc is translated to the right to the tangent point of the second arc to determine the position of the second arc. The two-dimensional geometric line is centered on the central axis of the axial flow pump impeller. By sweeping left and right, a nozzle with a jet direction of 90° to the front line of the impeller leading edge can be obtained. Then, a crescent-shaped nozzle can be obtained by rotating through the center of the nozzle.

2. The blade top water spraying device for improving the stability of an axial flow pump according to claim 1, characterized in that: The upper surface of the sealing cover (4) is provided with a plurality of through holes (7).

3. The blade top water spraying device for improving the stability of an axial flow pump according to claim 1, characterized in that: A pressure sensor is installed in the top of the diversion box (1).

4. The blade top water spraying device for improving the stability of an axial flow pump according to claim 1, characterized in that: A solenoid valve, a flow meter and a pulse valve are provided on the pipeline connecting the booster pump and the diversion box (1).

5. The blade top water spraying device for improving the stability of an axial flow pump according to claim 1, characterized in that: Each of the hoses (2) is provided with a valve.

6. A blade tip water spraying method for improving the stability of an axial flow pump, comprising: a blade tip water spraying device for improving the stability of an axial flow pump according to any one of claims 1 to 5, characterized in that: Specifically: The diversion box (1) is connected to the booster pump through a pipeline, the booster pump outlet is connected to the solenoid valve inlet, so as to control the real-time flow of the pipeline; the solenoid valve outlet is connected to the flow meter inlet, so as to measure the real-time flow of the pipeline; the flow meter outlet is connected to the pulse valve inlet, and the pulse valve outlet is connected to the diversion box (1), the nozzle device (3) is tightly connected to the wheel rim end wall of the axial flow pump, and then the water source is stably sprayed into the impeller channel through the nozzle.

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