Rim water spraying active control method for realizing rapid recovery of axial flow pump after instability

Abstract

The invention discloses a rim water spraying active control method for realizing quick recovery of an axial flow pump after instability, which specifically comprises the following steps: acquiring flow and lift of adjacent working condition points, calculating to obtain a lift change rate ki, and when ki is between 0 and 0.11, considering that the axial flow pump enters an instability working condition, and turning to the next step; otherwise, the axial flow pump is not unstable; a nozzle used for spraying water is additionally arranged on the rim of the axial flow pump, and the axial flow pump is recovered from an unstable working condition to a stable working condition by momentum of water spraying jet flow to excite flow channel blockage caused by blade top leakage vortex and rim backflow of the axial flow pump, so that rapid recovery of the axial flow pump after instability is completed. According to the method, instability early warning is carried out through the hump characteristic of the lift curve of the axial flow pump, rim water spraying is used as a flow control means, and rapid recovery of the axial flow pump after instability can be achieved through combination of the hump characteristic and the rim water spraying.

Description

Technical Field

[0001] The present invention belongs to the technical field of hydraulic machinery stability control, and particularly relates to an active control method of rim water injection for realizing rapid recovery after the instability of an axial flow pump. Background Technique

[0002] As the core power equipment of the ship water jet propulsion system and major water diversion projects, the operation stability of the axial flow pump directly affects aspects such as the water resource allocation efficiency. In actual working conditions, the axial flow pump faces severe challenges: when in a small flow condition, flow separation is extremely likely to occur in the tip region, triggering the phenomenon of rotating stall. This instability effect will not only lead to direct problems such as increased vibration and noise of the unit, but may also cause malignant accidents such as blade fatigue fracture, seriously threatening the safe operation of the pump unit. Especially in dynamic working conditions such as ship tactical maneuvers and tidal water level fluctuations, conventional control means are difficult to meet the engineering requirements of rapid and stable recovery.

[0003] Regarding the instability problem of the axial flow pump, scholars have carried out multi-dimensional research and proposed control methods including adjustable guide vanes, blade angle adjustment, clearance optimization, and end wall treatment. However, when the axial flow pump inevitably enters the unstable working condition, the above measures cannot enable the axial flow pump to quickly resume stable operation. Generally in engineering, after detecting that the vibration of the axial flow pump increases, measures such as blade pitching and shutdown are adopted to restore stability, but these control means are difficult to react in real time and quickly according to the changes of the working conditions and inflow conditions during operation, which will seriously affect the normal operation of the system. Therefore, it is urgent to develop an instability recovery method based on flow control to achieve the rapid recovery of the axial flow pump after instability.

[0004] Regarding axial flow compressors and axial flow pumps, jet and water injection technologies based on the jet principle have been studied to a certain extent in the field of passive control. However, passive control cannot solve the problem of the axial flow pump recovering after instability. In the key issue of the axial flow pump instability recovery, there is still a lack of relevant flow control means, especially there are obvious blanks in experimental research. Summary of the Invention

[0005] The purpose of the present invention is to provide an active control method of rim water injection for realizing rapid recovery after the instability of an axial flow pump, and solve the problem that the prior art cannot realize the rapid recovery of the axial flow pump after instability.

[0006] The technical solution adopted by the present invention is an active control method of rim water injection for realizing rapid recovery after the instability of an axial flow pump, which is specifically implemented according to the following steps: Step 1: Obtain the flow rate and head of adjacent working condition points, and calculate the head change rate k i When k iWhen it is between 0 and 0.11, it is considered that the axial flow pump enters the unstable working condition, and it turns to step 2; otherwise, the axial flow pump does not become unstable. Step 2: Install a nozzle for water spraying on the rim of the axial flow pump, and use the momentum of the water spray jet to excite the flow channel blockage caused by the tip leakage vortex and rim backflow of the axial flow pump blades, so as to restore the axial flow pump from the unstable working condition to the stable working condition, thus completing the rapid recovery after the axial flow pump becomes unstable.

[0007] The characteristics of the present invention also lie in that In step 1, specifically: Monitor the flow rate of the axial flow pump, and select the data of adjacent working condition points that satisfy the flow rate ratio ζ The calculation formula of the flow rate ratio ζ is:

[0008] In the formula, Q i represents the flow rate value of the i th working condition point, Q i+1 represents the flow rate value of the i + 1 th working condition point; i= 1, 2, 3... N, where N is a positive integer; Select the data of adjacent working condition points that satisfy ζ with a value of 0.9 to 0.99 to calculate the head change rate; The heads corresponding to Q i and Q i+1 are denoted as H i , H i+1 so as to obtain the head change rate k i at different flow rates. When k i is between 0 and 0.11, it is considered that the axial flow pump enters the unstable working condition, triggers an instability alarm, and turns to step 2; otherwise, the axial flow pump does not become unstable.

[0009] The calculation formula of the head change rate k i is shown in the following formula:

[0010] In the formula, H i represents the head value of the i th working condition point, H i+1 represents the head value of the i +1th working condition point.

[0011] In step 2, specifically: Step 2.1: Install nozzles for water spraying on the rim of the axial-flow pump impeller. The profile design of the nozzles is as follows: both the inner and outer profiles of the nozzles are circular arcs. Step 2.2: Design the position and number of nozzles. The number of nozzles N is the same as the number of blades of the axial-flow pump runner, and the nozzle structures are also the same. The sum of the circumferential coverage ratios of the jets during the operation of all nozzles reaches 30% - 100%, that is, the nozzles must spray water within the range of 30% - 100% along the circumferential direction. Step 2.3: Design the water source for nozzle spraying. The water source for spraying needs to be input after being pressurized by a booster pump, and the designed head of this booster pump is more than 2 times the designed head of the axial-flow pump, and the designed flow rate is more than 5% of the designed flow rate of the axial-flow pump.

[0012] In step 2.1, specifically: The inner and outer circular arcs of the nozzle are represented by arc Ⅰ and arc Ⅱ respectively, and their centers are represented by O Ⅰ and O Ⅱ respectively. The throat height of the nozzle is represented by h, and the tip clearance is represented by τ. Among them, the design of the inner circular arc should meet the following conditions: the tangent of the intersection position of the inner circular arc arc Ⅰ and the inner wall surface of the rim forms an angle of with the inner wall surface of the rim, and the perpendicular distance d Ⅰ from its center O Ⅰ to the inner wall surface of the rim = 0.5d - 0.7d. According to the above two parameters, the designed radius r Ⅰ of the inner circular arc can be calculated as r Ⅰ = d / cos Ⅱ and the outer circular arc arc ; the design conditions for the outer circular arc are: the tangent of the intersection position of the outer circular arc arc Ⅱ and the inner wall surface of the rim forms an angle of Ⅱ with the inner wall surface of the rim. For the outer circular arc arc Ⅱ = 0.5d - 0.7d, and similarly, its designed radius r Ⅱ = d Ⅱ / cos .

[0013] The tangent of the intersection position of the inner circular arc arc Ⅰ and the inner wall surface of the rim forms an angle between 10° and 20°.

[0014] The tangent of the intersection position of the outer circular arc arc Ⅱ and the inner wall surface of the rim forms an angle Between 20~30°.

[0015] The nozzle throat height h is between 2 and 6 between.

[0016] The beneficial effects of the present invention are: The proposed method uses the hump characteristic of the axial flow pump's head curve as an instability warning and utilizes rim water spray as a flow control mechanism. This combination of the two can achieve rapid recovery after an axial flow pump instability. Activating rim water spray under shallow instability conditions (SS, where the head begins to decrease), transitional instability conditions (TS, where the head rapidly decreases), deep instability conditions (DS, where the head reaches its lowest point), and post-instability conditions (PS, where the head begins to rise again) resulted in recovery within 3 seconds, 3 seconds, 4 seconds, and 6 seconds, respectively. After entering the passive control phase and stabilizing, the axial flow pump's head increased by 25%, 38.8%, 54.7%, and 56.3%, respectively, compared to the axial flow pump prototype. Simultaneously, the rim water spray significantly suppresses tip leakage flow, gradually eliminating leading edge overflow and channel vortices. The complex, disordered vortices at the blade tips of the axial flow pump gradually transform into tip leakage vortices with a swirling vortex pattern, ultimately resolving the instability of the axial flow pump. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is the flow-head characteristic curve of the axial flow pump; Figure 2 The position and structure diagram of the nozzle; Figure 3 This is the flow-head characteristic curve of the axial flow pump using active control for rapid recovery after instability; Figure 4 This is the flow-efficiency characteristic curve of the axial flow pump using active control for rapid recovery after instability; Figure 5 This is the distribution diagram of the blade tip leakage flow of the axial flow pump prototype; Figure 6 This is the distribution diagram of the axial reversal flow area at 99% blade height of the axial flow pump prototype; Figure 7 This is the vortex distribution diagram in the impeller channel when the jet flow rate is 4%; Figure 8 This is the vortex distribution diagram in the impeller channel when the jet flow rate is 6%; Figure 9 This is the vortex distribution diagram in the impeller channel when the jet flow rate is 8%. DETAILED DESCRIPTION

[0018] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0019] Example 1 The active control method of rim water injection for rapid recovery after the instability of an axial flow pump according to the present invention is specifically implemented according to the following steps: Step 1: Take the head of the axial flow pump as the core criterion for "instability warning", and set the head change rate of the flow-head characteristic curve as the "instability warning" threshold. After reaching the threshold, transmit the signal to the rim water injection system through the "instability warning - water injection control" system, and the rim water injection can be implemented under different "instability warning" thresholds. The rim water injection system is interlocked with the outlet throttle valve of the axial flow pump. At the moment when the rim water injection is turned on, the system immediately locks the opening degree of the outlet throttle valve of the axial flow pump to maintain the constant outlet flow boundary. "Instability warning" method: Refer to GB / T3216 - 89 "Test Methods for Centrifugal Pumps, Mixed - flow Pumps, Axial - flow Pumps and Vortex Pumps" to monitor the head characteristics of the axial flow pump during the throttling process. During actual testing, gradually close the outlet valve of the axial flow pump from a large flow rate for throttling, obtain the flow rate under different flow conditions through a flow meter, and obtain the corresponding head through the inlet and outlet pressures; Real - time monitor the flow rate and head data, and select the adjacent operating point data that satisfy the flow rate ratio ζ The flow rate ratio ζ The calculation formula is:

[0020] In the formula, Q i represents the flow rate value of the i th operating point, Q i+1 represents the flow rate value of the i +1 th operating point; i= 1, 2, 3…N, N is a positive integer; Select the adjacent operating point data that satisfy the ζ value of 0.9 - 0.99 to calculate the head change rate; The head corresponding to Q i and Q i+1 is denoted as H i , H i+1 , so as to obtain the head change rate k i under different flow rates; The head change rate formula is as follows:

[0021] In the formula, H i represents the head value of the i th operating point, H i+1 represents thei The head value at +1 operating point; Analyze the head change rate k i When the magnitude of k i is between 0 and 0.11, it is considered that the axial flow pump enters the unstable condition, triggers the instability alarm, and proceeds to step 2; otherwise, the axial flow pump has not become unstable; When the head change rate k i is greater than 0 for the first time, it is considered that the axial flow pump enters the unstable condition and triggers the instability alarm. k i can be set to different values to study the instability recovery effect under different unstable conditions. k i The range of k i is taken as 0 - 0.11. The smaller the absolute value of Step 2: Install a nozzle for water spraying on the rim of the axial flow pump, control the opening and closing of the water spraying valve with a solenoid valve, and open the valve to spray water. Use the momentum of the water spray jet to stimulate the flow channel blockage caused by the tip leakage vortex and rim backflow of the axial flow pump, and restore the axial flow pump from the unstable condition to the stable condition. After restoration, close the solenoid valve, thus completing the rapid recovery after the axial flow pump becomes unstable. Specifically: Step 2.1: Profile design of the nozzle for rim water spraying; as Figure 2 shown, to effectively achieve the momentum excitation of the water spray jet, utilize the Coanda effect to ensure that the profile design of the nozzle meets the requirement that the jet stream adheres closely to the inner wall surface of the rim. According to the flow characteristics of the fluid and the ease of processing, both the inner and outer profiles of the nozzle are designed with circular arcs. Figure 2 As shown in Ⅰ and Ⅱ in Ⅰ for the positions and shapes of the inner and outer arcs, the inner and outer arcs are represented by the symbols arc Ⅱ and arc Ⅰ respectively, and their centers are represented by O Ⅱ and O Ⅰ respectively. The throat height of the nozzle is represented by h, and the tip clearance is represented by τ. The design of the inner arc should meet the following conditions: The tangent of the intersection position of the inner arc arc and the inner wall surface of the rim with the inner wall surface of the rim should be between 10° and 20°. The perpendicular distance d Ⅰ from its center O Ⅰ to the inner wall surface of the rim = 0.5d - 0.7d. Based on these two parameters, the calculated design radius r Ⅰ of the inner arc = d Ⅰ / cos . The design conditions for the outer arc are: The outer arc arc ⅡThe angle between the tangent line at the intersection position with the inner wall surface of the rim and the inner wall surface of the rim should be between 20° and 30°, and its angle value is affected by the angle. It is necessary to ensure that the outer arc arc Ⅱ and the inner arc arc Ⅰ form a contraction flow channel that is wide outside and narrow inside in the middle area, so as to ensure that the jet flows out closely along the inner wall surface of the rim. For the outer arc arc Ⅱ , its center O Ⅱ to the vertical distance d from the inner wall surface of the rim Ⅱ = 0.5d to 0.7d. Similarly, its design radius r Ⅱ = d Ⅱ / cos . To make the jet flow rate meet the flow rate requirements of momentum excitation, the throat height h of the nozzle should be between 2 and 6 .

[0022] Step 2.2, Design of the position of the nozzle for rim water spraying; To achieve an ideal jet momentum excitation effect, the determination of the nozzle position mainly refers to two parameters: the number of nozzles and the circumferential coverage ratio of the nozzles. Among them, the number of nozzles N should be the same as the number of runner blades of the axial flow pump, and the nozzle structure should also be the same to ensure that the jet flow rate at each circumferential position is controllable when the valve opens and closes. The sum of the circumferential coverage ratios of the jets when all nozzles are working should reach 30% - 100%, that is, the nozzles must spray water within the range of 30% - 100% along the circumferential direction.

[0023] Step 2.3, Design of the water source for rim water spraying; To meet the automatic control effect, the water source for spraying water needs to be input after being pressurized by a booster pump, and the designed head of this booster pump must be more than 2 times the designed head of the axial flow pump, and the designed flow rate must be more than 5% of the designed flow rate of the axial flow pump.

[0024] Example 2 Relying on the axial flow pump closed-loop test bench of the State Key Laboratory of Eco-Hydraulic Engineering in Arid Regions of Xi'an University of Technology, the main design parameters of this axial flow pump are shown in Table 1:

[0025] The main parameters for testing the hydraulic external characteristics of the axial flow pump include: rotational speed, flow rate, inlet and outlet pressures, torque, and power. The inlet and outlet pressures are measured by pressure transmitters installed at the inlet and outlet of the axial flow pump, the flow rate is measured by an electromagnetic flowmeter installed in the outlet pipeline, and the torque and power are measured by a torque speed meter installed between the pump and the motor. All test equipment is connected to the control system to achieve synchronous monitoring and continuous storage of experimental parameters. During the experiment, the instability warning conditions were changed, and rim water spraying was started under different instability conditions of the axial flow pump for instability recovery, and the influence of the instability conditions on the instability recovery effect was studied.

[0026] In the calculation of the external characteristics of an axial-flow pump, the rim water injection system injects additional energy into the axial-flow pump through an external water supply device. The energy separation method is required to eliminate its influence on the performance evaluation of the axial-flow pump. By combining experimental measurement with the principle of energy conservation, a quantitative characterization method for the net energy of rim water injection is established. After perfusion is completed on the closed test bench, keep the main drive unit of the axial-flow pump and the booster centrifugal pump in a shutdown state, independently activate the rim water injection system, and establish a fluid circulation through its entrainment effect. When the flow rate volatility of the experimental system is lower than ±0.5%, it is determined to be in a stable state, and the pressure at the inlet and outlet sections of the axial-flow pump, the outlet volume flow rate, and the jet flow rate parameters are synchronously collected.

[0027] Consider the net energy introduced by the rim water injection and establish equations for the inlet and outlet sections of the axial-flow pump: ,

[0028] After rearrangement, we can get:

[0029] In the formula, P 1, P 2 are the inlet gauge pressure and the outlet gauge pressure respectively, with the unit of Pa; v 1, v 2 are the average flow velocities at the inlet and outlet sections of the axial-flow pump respectively, with the unit of m / s; Q 1, Q 2 represent the inlet volume flow rate and the outlet volume flow rate respectively, with the unit of m 3 / h; A 1, A 2 are the areas of the inlet and outlet sections of the axial-flow pump respectively, with the unit of m 2 ; z 1, z 2 are the heights where the pressure measurement points at the inlet and outlet of the main channel of the axial-flow pump are located respectively, with the unit of m; H 0 is the increase in head caused by the net energy injected by the nozzle, with the unit of m.

[0030] Test the increase in the head H0 of the axial-flow pump caused by the rim water injection at different jet flow rates m inj , and fit the test data. The quadratic equation of the fitted curve is as follows: H 0 = 0.0016 m inj 2 + 0.0039 m inj - 0.1148 According to this equation, the increase in head at different jet flow rates can be obtained. The head H of the axial-flow pump is defined as:

[0031] The efficiency formula of the axial flow pump is defined as:

[0032] In the formula, M is the torque of the main shaft, with the unit of N·m; ω is the rotational speed of the main shaft, with the unit of rad / s.

[0033] Example 3 Figure 3 is the flow-head characteristic curve diagram for the rapid recovery after the axial flow pump becomes unstable. As can be seen from the figure, when the axial flow pump enters the unstable operating condition, the head shows a sudden drop trend. After the rim spraying is started to implement unstable recovery, the head of the axial flow pump increases linearly along the vertical direction rapidly. The increase in the head of the axial flow pump can be divided into two stages: (1) Unstable recovery stage: The head of the axial flow pump increases to near the "virtual" head, and this "virtual" head is obtained by performing a quadratic polynomial ( H =-1.39×10 - 4 Q 2 +0.027 Q +2.75) least squares fitting of the stable operating condition head curve, that is, the head that the axial flow pump might have if it does not become unstable. (2) Passive control stage: After the axial flow pump completes unstable recovery, the head further rises and finally stabilizes at the passive control level. In the shallow unstable operating condition (SS, where the head starts to drop), the transitional unstable operating condition (TS, the stage where the head drops rapidly), the deep unstable operating condition (DS, the lowest point of the head), and the post-unstable operating condition (PS, the point where the head starts to rise again), it takes 3 s, 3 s, 4 s, and 6 s respectively. After completing unstable recovery and entering the passive control stage and stabilizing, the head of the axial flow pump is increased by 25%, 38.8%, 54.7%, and 56.3% respectively compared to the prototype of the axial flow pump. Keeping the jet flow rate of the rim spraying unchanged and continuing to throttle the outlet of the axial flow pump, as the flow rate of the axial flow pump decreases, the head curve of the axial flow pump gradually changes from a negative slope to a positive slope, that is, the phenomenon that the head decreases as the flow rate decreases appears, but the "hump" characteristic does not appear. When implementing unstable recovery under different unstable operating conditions, the stabilized head curve is basically the same as the head curve of the axial flow pump under passive control.

[0034] Example 4 Figure 4It is the flow rate - efficiency characteristic curve for the rapid recovery after the axial - flow pump becomes unstable. As can be seen from the figure, after implementing rim spraying for instability recovery, similar to the variation trend of the head of the axial - flow pump, the efficiency of the axial - flow pump increases rapidly, and the final efficiency curve is basically the same as that of the axial - flow pump under passive control. Thus, it can be seen that by implementing rim spraying under different unstable operating conditions, the head and efficiency of the axial - flow pump can increase rapidly, and then quickly exit the unstable state. The instability warning condition has a slight impact on the instability recovery time and has no impact on the performance of the axial - flow pump after completing the instability recovery.

[0035] Example 5 Figure 5 It is the distribution of tip leakage flow under the prototype axial - flow pump's transitional instability condition. As can be seen from the figure, the tip flow of the axial - flow pump shows strong unsteadiness; at the same time, the interaction between another part of the leakage flow and the mainstream leads to the generation of passage vortex structures perpendicular to the blade surface in the channel.

[0036] Figure 6 It is the transient distribution of the 99% blade - height axial reverse - flow region under the prototype axial - flow pump's transitional instability condition. As can be seen from the figure, a large - area axial reverse - flow region appears in the tip region of the axial - flow pump, and its coverage range reaches 3 - 4 adjacent flow channels. This blocked region is the rotating stall group of the axial - flow pump, which is about 70% of the axial - flow pump's rotational speed.

[0037] Example 6 Figure 7 It is the vortex distribution in the impeller channel when the jet flow rate is 4% under the action of rim spraying. As can be seen from the figure, at this time, the tip leakage flow is inhibited to a certain extent, the forward extension range of the overflow along the axial direction at the leading edge of the leakage flow is slightly reduced, and the interaction between the passage vortex and the leading - edge overflow forms a larger vortex group. Combining with the head characteristics, it can be known that the head of the axial - flow pump continues to decrease at this time; for the blade channels without blockage, the shape of the tip leakage vortex is regular, showing a swirling state with a high vorticity distribution.

[0038] Figure 8 It is the vortex distribution in the impeller channel when the jet flow rate is 6% under the action of rim spraying. As can be seen from the figure, at this time, the jet flow velocity is relatively large, and it interacts with the mainstream to form a jet vortex. The inhibitory effect of rim spraying on the tip leakage flow is enhanced, and the leading - edge overflow phenomenon of the tip leakage flow almost disappears. At this time, the jet interacts with the leakage flow and the passage vortex to form a larger turbulent vortex, which fills the entire blade channel, and the head of the axial - flow pump reaches the lowest. After continuing to increase the jet flow velocity, the head of the axial - flow pump begins to increase.

[0039] Figure 9 It is the vortex distribution in the impeller channel when the jet flow rate is 8% under the action of rim spraying. As can be seen from the figure, at this time, in most channels, the tip leakage flow and the mainstream interact to form a swirling vortex with a high vorticity distribution and a regular shape. Due to the action of the adverse pressure gradient, a small - scale spiral breakage appears in some tip leakage vortices, and the tip flow field is "restored".

Claims

1. An active control method of rim water injection for achieving rapid recovery after the instability of an axial flow pump, characterized in that The implementation is specifically carried out according to the following steps: Step 1. Obtain the flow rate and head of adjacent operating points, and calculate the head change rate k i , when k i is between 0 and 0.11, it is considered that the axial flow pump enters the unstable operating condition, and go to Step 2; Otherwise, the axial-flow pump is not unstable. Step 2: Install nozzles for water spraying on the rim of the axial-flow pump. Utilize the momentum of the water jet to stimulate the flow channel blockage caused by the tip leakage vortex and the rim backflow of the axial-flow pump, and restore the axial-flow pump from the unstable working condition to the stable working condition, thereby completing the rapid recovery after the axial-flow pump becomes unstable.

2. The active control method of rim water injection for realizing rapid recovery after the instability of an axial flow pump as described in claim 1, characterized in that, In step 1, specifically: Monitor the flow rate of the axial flow pump and select the data of adjacent operating points that satisfy the flow rate ratio ζ The calculation formula for the flow rate ratio ζ is as follows: In the formula, Q i represents the flow rate value at the i th operating condition point, Q i+1 represents the flow rate value at the i +(th) operating condition point; i= 1, 2, 3…N, where N is a positive integer; Select adjacent operating condition point data that meet ζ with a value of 0.9 to 0.99 to calculate the head change rate; With Q i and Q i+1 The corresponding head is denoted as H i , H i+1 so as to obtain the head change rate at different flow rates k i When k i is between 0 and 0.11, it is considered that the axial flow pump enters the unstable working condition, triggers the instability alarm, and proceeds to step 2; otherwise, the axial flow pump does not experience instability.

3. The active control method of rim water injection for realizing rapid recovery after the instability of an axial flow pump as described in claim 1, characterized in that, Head change rate k i The calculation formula is as follows: In the formula, H i represents the head value at the i th operating condition point, H i+1 represents the head value at the i +1 th operating condition point.

4. The active control method of rim water injection for realizing rapid recovery after the instability of an axial flow pump as described in claim 3, characterized in that, In step 2, specifically: Step 2.1: Install nozzles for water spraying on the rim of the axial-flow pump. The profile design of the nozzles: both the inner and outer profiles of the nozzles are arc-shaped. Step 2.2: Design of the position and quantity of the nozzles: The number N of the nozzles is the same as the number of blades of the axial-flow pump runner, and the nozzle structures are also the same. The sum of the circumferential coverage ratios of the jets during the operation of all nozzles reaches 30% - 100%, that is, the nozzles must spray water within the range of 30% - 100% along the circumferential direction. Step 2.3: Design of the water source for the nozzles to spray water: The water source for spraying water needs to be input after being pressurized by a booster pump, and the designed head of this booster pump is more than twice the designed head of the axial-flow pump, and the designed flow rate is more than 5% of the designed flow rate of the axial-flow pump.

5. The active control method of rim water injection for realizing rapid recovery after the instability of an axial flow pump as described in claim 4, characterized in that In step 2.1, specifically: The inner and outer arcs of the nozzle are respectively represented by arc Ⅰ and arc Ⅱ Indicated by O, the centers of the two circles are respectively Ⅰ and O Ⅱ The nozzle throat height is represented by h, and the blade tip clearance is represented by τ; the design of the inner arc should meet the following conditions: Ⅰ The angle between the tangent line at the intersection with the inner wall of the rim and the inner wall of the rim is , whose center is O Ⅰ Vertical distance d to the inner wall of the rim Ⅰ =0.5d~0.7d, based on the above two parameters, the design radius r of the inner arc can be calculated Ⅰ =d Ⅰ / cos ; The design conditions of the outer arc are: outer arc Ⅱ The angle between the tangent line at the intersection with the inner wall of the rim and the inner wall of the rim is , for the outer arc Ⅱ , whose center is O Ⅱ Vertical distance d to the inner wall of the rim Ⅱ =0.5d~0.7d, and the design radius r can also be obtained Ⅱ =d Ⅱ / cos .

6. The active control method of rim water injection for realizing rapid recovery after the instability of an axial flow pump as described in claim 5, characterized in that, Inner arc Ⅰ The included angle between the tangent line at the intersection position with the inner wall surface of the rim and the inner wall surface of the rim is between 10° and 20°.

7. The active control method of rim water injection for realizing rapid recovery after the instability of an axial flow pump as described in claim 5, characterized in that, Outer arc Ⅱ The included angle between the tangent line at the intersection position of the outer arc and the inner wall surface of the rim and the inner wall surface of the rim is between 20° and 30°.

8. The active control method of rim water injection for achieving rapid recovery after the instability of an axial flow pump as described in claim 5, characterized in that, The throat height h of the nozzle is between 2 and 6 inclusive.

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