Anti-cavitation centrifugal pump device based on flow channel optimization and method thereof

Abstract

The application relates to the field of fluid machines, in particular to an anti-cavitation centrifugal water pump device based on flow channel optimization and a method thereof; the device comprises a pump shell with a bypass backflow channel, an impeller with a flow guide micro groove, a valve assembly and a controller; the system combines the operation parameters of a main driving motor to solve the stator current variance, so as to evaluate the cavitation impact strength; the core is that when the current variance is greater than a preset safety threshold, a stepping motor is controlled to drive a rotating valve core, and the flow passage sectional area of the bypass backflow channel is dynamically adjusted; the application discards the traditional architecture of deploying sensors in the pump shell, accurately inverts the cavitation degree by using the current variance and dynamically compensates, so that the system hardware architecture and assembly process are simplified, and the continuous volume efficiency loss caused by the fixed large-opening backflow under the non-cavitation stable working condition is effectively avoided.

Description

Technical Field

[0001] This invention relates to the field of fluid machinery, specifically to an anti-cavitation centrifugal water pump device and method based on flow channel optimization. Background Technology

[0002] In current fluid transport applications, single-stage end-suction centrifugal pumps are prone to cavitation on the impeller surface due to localized low pressure during periods of varying operating conditions or reduced inlet pressure. The microjet generated when bubbles rapidly collapse upon entering the high-pressure zone directly impacts the metal surface of the blades, leading to material damage and spalling, reduced head, and high-frequency nonlinear torque pulsation. To suppress cavitation damage, existing solutions generally employ machining fixed return holes, adding inducer wheels, or using a fixed, large-aperture bypass return architecture. While these solutions can alleviate cavitation to some extent, their intervention mechanisms lack dynamic adaptability, resulting in continuous and unnecessary volumetric efficiency losses under non-cavitation stable operating conditions. Furthermore, adding inducer wheels alters the pump's external dimensions, and conventional dynamic adjustment schemes heavily rely on deploying pressure or vibration sensors within the pump chamber, increasing system complexity and assembly difficulty, and compromising sensor reliability under harsh conditions.

[0003] Therefore, how to accurately invert the cavitation impact intensity based on the motor operating parameters without adding a built-in sensor in the pump chamber or changing the original external dimensions of the water pump, and dynamically adjust the high-pressure fluid to accurately return to eliminate the direct impact on the impeller surface, while minimizing the loss of volumetric efficiency, has become an urgent technical problem to be solved. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a cavitation-resistant centrifugal water pump device and method based on flow channel optimization. Specifically, the technical solution of this invention is as follows: A cavitation-resistant centrifugal water pump device based on flow channel optimization includes: The pump casing has an internally cast suction channel and a volute channel; the side wall of the pump casing is machined with a bypass return channel; the bypass return channel connects the volute channel and the suction channel; a valve seat hole is vertically opened in the middle section of the bypass return channel. The main shaft is supported in a bearing housing provided on the pump casing; the main shaft is driven to rotate by a main drive motor. An impeller is fixedly connected to the end of the main shaft that extends into the pump casing; the impeller includes multiple blades; the back of the blades of the impeller is milled with flow-guiding microgrooves; the flow-guiding microgrooves are arranged in parallel. A valve assembly includes a rotary valve core and a stepper motor; the rotary valve core is installed in the valve seat hole; a through hole is formed in the side wall of the rotary valve core; the stepper motor is fixed to the outer surface of the pump housing; the output shaft of the stepper motor is connected to the end of the rotary valve core; The controller controls the stepper motor; the controller acquires the operating parameters of the main drive motor to calculate the rotation angle of the stepper motor.

[0005] In one possible implementation, the orientation of the flow-guiding microgroove coincides with the relative velocity streamline of the fluid on the back of the blade; the depth of the flow-guiding microgroove gradually decreases along the direction of water flow from the inlet to the outlet until it smoothly transitions to the blade surface.

[0006] In one possible implementation, the main shaft is supported in the bearing housing by an angular contact ball bearing; the impeller is fixedly connected to the main shaft by a flat key and a lock nut; and a clearance fit is maintained between the impeller and the inner wall of the pump casing.

[0007] In one possible implementation, the output shaft of the stepper motor is connected to the end of the rotary valve core via a cross-slider type flexible coupling; the cross-slider type flexible coupling is used to absorb vibrations generated by the operation of the motor.

[0008] In one possible implementation, the rotary valve core is cylindrical; the rotary valve core is installed in the valve seat bore by an interference fit.

[0009] In one possible implementation, the diameter of the through hole is equal to the diameter of the bypass return channel.

[0010] A method for operating an anti-cavitation centrifugal water pump based on flow channel optimization, comprising: S1. During the initial stable operation phase of the water pump without cavitation, the stator current of the main drive motor is continuously collected, the fundamental effective value of the stator current is extracted as the reference stable current, and the spindle speed is recorded. S2. During the pump's variable operating condition phase, the instantaneous fluctuating current of the stator winding of the main drive motor is collected in real time according to a preset sampling period; the transient impact frequency band in the instantaneous fluctuating current is extracted by filtering, and the current fluctuation is obtained based on the characteristics of the instantaneous fluctuating current. S3. The sum of the squares of the current fluctuations over a predetermined number of consecutive sampling periods is divided by the total number of the predetermined number of sampling periods to calculate the current variance; wherein, the current variance represents the cavitation impact intensity. S4. Determine the relationship between the current variance and the preset safety threshold; when the current variance is greater than the preset safety threshold, subtract the preset safety threshold from the current variance to obtain the overshoot; when the current variance is less than or equal to the preset safety threshold, do not increase the rotation angle of the rotary valve core. S5. When the current variance is greater than the preset safety threshold, according to the current spindle speed, call the pre-calibrated speed and conversion coefficient correspondence table, look up the table to obtain the flow conversion coefficient; multiply the overshoot by the flow conversion coefficient to obtain the compensation flow rate; combine the preset maximum flow cross-sectional area of ​​the bypass return channel and the fluid pressure difference between the volute channel and the suction channel to calculate the target effective flow cross-sectional area, and then convert it into the target rotation angle required for the rotary valve core to rotate, and control the stepper motor to rotate to the target rotation angle.

[0011] In one possible implementation, step S5 is followed by: S601. After controlling the stepper motor to rotate to the target rotation angle, monitor the instantaneous change current of the main drive motor; S602. After the bypass return channel is opened and a preset flow field stabilization delay time has elapsed, the current fluctuation in the current sampling period is calculated. S603. Recalculate the current variance. When the current variance drops to within a preset safety threshold, maintain the current rotation angle of the stepper motor.

[0012] In one possible implementation, step S5 is followed by: S701. Monitor the current variance in real time; wherein, the current variance is compared with the preset safety threshold; when the current variance is less than or equal to the preset safety threshold, the difference between the current variance and the preset safety threshold is calculated to obtain a negative deviation; when the current variance is greater than the preset safety threshold, return to step S4. S702. Multiply the absolute value of the negative deviation by the recovery coefficient to calculate the rotary valve core return rotation angle. S703. Control the stepper motor to rotate in the opposite direction by the callback rotation angle to reduce the channel flow cross-sectional area; wherein, the adjustment is repeated until the current variance stabilizes at the preset safety threshold critical point.

[0013] In one possible implementation, step S2, which involves real-time acquisition of the instantaneous fluctuating current of the stator winding of the main drive motor, specifically includes: forcibly filtering out the power supply fundamental frequency and low-frequency components of mechanical interference below a preset cutoff frequency using a high-pass digital filter; extracting the transient impulse frequency band in a preset high-frequency range using a band-pass digital filter; and multiplying the extreme value of the envelope of the extracted transient impulse frequency band by a preset gain coefficient, using the calculation result as the current fluctuation amount in step S2.

[0014] The present invention has the following beneficial effects: 1. This invention continuously collects the stator current of the stator winding of the main drive motor through a controller, calculates the current variance representing the cavitation impact intensity; when the current variance is greater than a preset safety threshold, the target rotation angle is calculated, and the stepper motor drives the rotary valve core to dynamically adjust the flow cross-sectional area of ​​the bypass return channel; this solution can accurately invert the degree of cavitation and perform dynamic compensation without deploying pressure or vibration sensors in the pump casing, which simplifies the system hardware architecture and assembly process, and effectively avoids the continuous loss of volumetric efficiency caused by using a fixed large-opening return architecture under non-cavitation stable operating conditions; 2. The impeller blades of the present invention are milled with parallel flow-guiding microgrooves on their back sides. After the high-pressure fluid in the volute flow channel is injected through the bypass return channel, it cuts into the flow-guiding microgrooves and accelerates under the action of impeller rotation, thereby forming a local micro boundary layer separation air cushion in the groove. This air cushion can push the low-pressure bubbles remaining in the suction channel away from the metal surface of the blades, forcing the low-pressure bubbles to collapse in the mainstream fluid area away from the blade surface. This structure effectively avoids the direct impact and material damage to the impeller surface caused by the micro-jet generated when the bubbles collapse, without changing the original shape and installation dimensions of the water pump. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. In the drawings: Figure 1 This is a schematic diagram of the overall structure of the device; Figure 2 This is a schematic diagram of the volute flow channel structure of the device; Figure 3 This is a top-view sectional diagram of the device; Figure 4 This is a schematic diagram of the valve assembly structure of the device; Figure 5 This is a schematic diagram of the impeller structure of the device; Figure 6 This is a flowchart of the method of the present invention.

[0016] In the diagram: 1. Pump casing; 2. Suction channel; 3. Volute channel; 4. Bypass return channel; 5. Valve seat hole; 6. Main shaft; 7. Bearing housing; 8. Main drive motor; 9. Impeller; 10. Guide microgroove; 11. Valve assembly; 12. Rotary valve core; 13. Stepper motor; 14. Through hole; 15. Controller; 16. Angular contact ball bearing; 17. Flat key; 18. Anti-loosening nut; 19. Cross-slider type flexible coupling. Detailed Implementation

[0017] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0018] Example 1:

[0019] A cavitation-resistant centrifugal water pump device based on flow channel optimization, such as Figure 1 As shown, it includes: Pump casing 1, internally cast with suction channel 2 and volute channel 3; the side wall of pump casing 1 is machined with bypass return channel 4, such as... Figure 3 As shown; the bypass return channel 4 connects the volute flow channel 3 and the suction flow channel 2; a valve seat hole 5 is vertically opened in the middle section of the bypass return channel 4; like Figure 2 As shown, the main shaft 6 is supported in the bearing seat 7 provided on the pump housing 1; the main shaft 6 is driven to rotate by the main drive motor 8. Impeller 9 is fixedly connected to the end of the main shaft 6 that extends into the pump casing 1; impeller 9 includes multiple blades; guide microgrooves 10 are milled on the back of the blades of impeller 9; guide microgrooves 10 are arranged in parallel. Valve assembly 11, such as Figure 4 As shown, it includes a rotary valve core 12 and a stepper motor 13; the rotary valve core 12 is installed in the valve seat hole 5; a through hole 14 is opened on the side wall of the rotary valve core 12; the stepper motor 13 is fixed to the outer surface of the pump housing 1; the output shaft of the stepper motor 13 is connected to the end of the rotary valve core 12; The controller 15 controls the stepper motor 13. The controller 15 continuously collects the stator current of the main drive motor 8 to extract the reference stable current, and collects the instantaneous fluctuating current in real time under changing operating conditions. It calculates the variance of the current fluctuation after subtracting the instantaneous fluctuating current from the reference stable current as the current variance representing the cavitation impact intensity. When the current variance is greater than the preset safety threshold, it calculates the target effective flow cross-sectional area by combining the flow conversion coefficient, the maximum flow cross-sectional area of ​​the bypass return channel 4 and the fluid pressure difference, and then converts it into the rotation angle of the stepper motor 13. A single-stage end-suction centrifugal water pump with a rated flow rate of 180 m³ / h and a rated head of 32 meters was selected as the implementation object. The pump casing 1 is integrally cast from ductile iron to form the suction channel 2 and the volute channel 3. The suction channel 2 is connected to the inlet flange, and the volute channel 3 is connected to the outlet flange. The bypass return channel 4 is machined from the side wall of the pump casing 1. Its inlet is located in the volute channel 3 near the design high pressure area, and its outlet is located in the suction channel 2 near the outer edge of the impeller 9 inlet, so that the high pressure liquid in the volute channel 3 can flow back to the suction channel 2 under the action of pressure difference. The valve seat hole 5 is located in the middle section of the bypass return channel 4 and is perpendicular to the axis of the return channel, so that the valve core 12 can be rotated to change the effective flow area of ​​the bypass return channel 4; the main shaft 6 is mounted on the pump casing 1 through the bearing seat 7 and is connected to the external main drive motor 8 via a coupling. An impeller 9 is installed at one end of the main shaft 6 that extends into the pump casing 1; the impeller 9 is preferably a closed impeller 9 with 5 blades. Each blade has parallel-arranged guide microgrooves 10 machined on its back. The guide microgrooves 10 are used to guide the local flow after the high-pressure return liquid enters the inlet area of ​​the impeller 9. The rotary valve core 12 in the valve assembly 11 is placed in the valve seat hole 5. The side wall of the rotary valve core 12 is provided with a through hole 14. The stepper motor 13 is installed on the outer surface of the pump housing 1. The output shaft of the stepper motor 13 is connected to the end of the rotary valve core 12. The controller 15 adopts an industrial control board or PLC. The controller 15 reads the operating parameters of the main drive motor 8. The operating parameters include the stator current and the spindle speed 6. The controller 15 calculates the target angle of the rotary valve core 12 based on the current fluctuation and the speed, and then controls the stepper motor 13 to adjust the opening of the bypass return channel 4. Compared to solutions that rely solely on fixed return holes or adding inducers, this device combines flow channel structure adjustment with operating parameter inversion without changing the pump's external dimensions and installation size. This allows the return flow to intervene only when cavitation intensifies, and the return liquid acts on the low-pressure area at the impeller 9 inlet through the guide microgroove 10 on the back of the blade, thereby reducing the cavitation impact intensity on the impeller 9 surface. In prototype bench tests, when the inlet absolute pressure drops to near the conventional allowable cavitation margin, the device can maintain the current fluctuation variance near the set threshold and reduce the head drop by about 15% to 22% compared to the fixed throttling suppression method; The processing logic in controller 15 for calculating the rotation angle of stepper motor 13 includes the following steps in sequence: first, establishing a storage table of the reference stable current and the corresponding spindle speed under cavitation-free stable operating conditions; then, continuously reading the current sample value and the current speed during operation; and comparing the current sample value with the reference stable current under the same speed range to obtain the current fluctuation amount used to characterize the strength of load pulsation. When the current fluctuation exceeds the range corresponding to the preset safety threshold after accumulating in multiple consecutive sampling periods, the controller 15 determines that the bypass return flow needs to be increased; according to the current speed, it calls the pre-calibrated angle-flow correspondence table, converts the required compensation flow into the target angle of the rotary valve core 12, and converts it into the number of pulses according to the stepper motor 13 subdivided step distance; In this embodiment, the preset safety threshold is used to distinguish between normal hydraulic disturbances and abnormal torque pulsations that may cause destructive cavitation. The threshold is derived from the statistical upper limit obtained by continuously sampling the current fluctuation under the condition of stable operation of the prototype without damage. It is preferably 1.2 to 1.5 times the statistical upper limit. The angle-flow correspondence table was obtained by static and dynamic joint calibration after the prototype was assembled. During calibration, the bypass flow rate under different valve core rotation angles, different speeds, and typical differential pressure conditions was recorded, so that the angle calculation of controller 15 has a clear data source, rather than relying solely on empirical estimation. For the execution of the output pulses of the stepper motor 13, the controller 15 preferably sets a minimum adjustment step size and a single maximum adjustment angle. The minimum adjustment step size can be 0.2° to 0.5°, and the single maximum adjustment angle can be 8° to 15°, so as to avoid the valve core from being over-opened at one time due to the transient change of inlet pressure. Through the above step-by-step processing, a continuous correspondence is formed between the operating parameters, logic thresholds, target angles and execution actions, so that the device is feasible at both the structural and control levels.

[0020] 10 microchannels for flow guidance Figure 5 As shown, the direction of the flow coincides with the relative velocity streamline of the fluid on the back of the blade; wherein, the depth of the flow guide microgroove 10 gradually becomes shallower along the direction of water flow from the inlet to the outlet until it smoothly transitions to the blade surface. In the specific technical environment of this invention, the flow guiding microchannel 10 is not an ordinary weight reduction channel or surface roughening texture, but a functional flow channel used to receive bypass high-pressure fluid and induce it to flow directionally along the low-pressure area on the back of the blade. In order to ensure that the return liquid does not produce obvious lateral separation after entering the back of the blade, the center line of the flow guiding microchannel 10 is arranged according to the relative velocity streamline on the back of the blade, and its direction can be determined by three-dimensional flow field numerical calculation or oil film test. Taking the prototype with an impeller 9 inlet diameter of 128mm and an outlet diameter of 256mm as an example, three flow-guiding microgrooves 10 are set on the back of each blade. The width of the microgrooves is 0.8mm to 1.6mm. The groove depth near the impeller 9 inlet is 0.35mm to 0.60mm, gradually decreasing to within 0.05mm along the fluid flow direction and smoothly connecting with the blade surface. The radius of the bottom fillet of the groove is controlled between 0.15mm and 0.30mm to reduce stress concentration and flow separation. With the above structure, when the high-pressure liquid from the bypass return channel 4 enters the guide microchannel 10, it will spread along the relative velocity direction. As the microchannel gradually becomes shallower, the local flow velocity and static pressure recovery process is smoother, which can form an adhering flow layer on the back of the blade and increase the local absolute pressure on the blade surface. Compared with the equal-depth trench, the gradually shallowing guide microchannel 10 can reduce the volume of the vortex region at the end of the channel, so that the flow momentum of the return water is used more to push away near-wall bubbles rather than forming additional losses. Comparative tests show that, under the same bypass opening, the critical cavitation current variance of the gradually shallowing microchannel prototype is reduced by about 12% to 18% compared with the equal-depth trench prototype.

[0021] The main shaft 6 is supported in the bearing housing 7 by an angular contact ball bearing 16; the impeller 9 is fixedly connected to the main shaft 6 by a flat key 17 and a lock nut 18; the impeller 9 maintains a clearance fit with the inner wall of the pump casing 1; The main shaft 6 support structure is used to ensure that the impeller 9 maintains a stable spatial position under variable operating conditions and bypass adjustment conditions, and to prevent the guiding effect of the guide micro-groove 10 on the return liquid from weakening due to the axial or radial movement of the rotor. In this embodiment, the main shaft 6 is supported by a pair of angular contact ball bearings 16 in the bearing seat 7 provided on the pump casing 1. The angular contact ball bearings 16 are arranged in pairs and preloaded. The preload is selected from 600N to 1200N to bear the rotor's own weight, hydraulic radial force and axial force. The impeller 9 is connected to the main shaft 6 via a flat key 17 for torque transmission and is axially tightened by a lock nut 18. The lock nut 18 can be equipped with a backstop washer to prevent the threads from loosening under cavitation pulsation conditions. A clearance fit is provided between the outer edge of the impeller 9 and the inner wall of the pump casing 1. The clearance value can be selected from 0.20mm to 0.45mm according to the pump specifications. This clearance satisfies the rotation safety and controls the leakage loss within the allowable range. Since the present invention introduces a compensating flow rate into the suction channel 2 through the bypass return channel 4, the pressure distribution near the impeller 9 inlet will change dynamically. The angular contact ball bearing 16 can reliably limit the axial displacement of the main shaft 6, so that the relative position of the impeller 9 inlet and the suction channel 2 remains consistent, which makes it easier for the controller 15 to perform inversion calculation of the current variance based on the same mechanical boundary conditions. The test bench operation results show that after 300 consecutive start-stop cycles and 200 hours of operation deviating from the design conditions, the support and connection structure did not exhibit any axial loosening or abnormal friction of the impeller 9, indicating that it can meet the implementation requirements of the device of this invention.

[0022] The output shaft of the stepper motor 13 is connected to the end of the rotary valve core 12 via a cross-slider type flexible coupling 19; wherein, the cross-slider type flexible coupling 19 is used to absorb the vibration generated by the motor operation; The transmission connection between the stepper motor 13 and the rotary valve core 12 not only needs to transmit angular displacement, but also needs to compensate for the assembly deviation between the outer mounting surface of the pump housing 1 and the valve seat hole 5. In this embodiment, the stepper motor 13 is a two-phase stepper motor 13 with a holding torque of 2 N·m to 4 N·m, and the output shaft is connected to the end of the rotary valve core 12 via a cross slider type flexible coupling 19. The cross-slider type flexible coupling 19 consists of two half couplings and a middle slider. One side is keyed or clamped to the output shaft of the stepper motor 13, and the other side is keyed or pinned to the end of the rotary valve core 12. The middle slider slides in mutually perpendicular guide grooves, thereby allowing a radial deviation of 0.2mm to 0.6mm and an axial installation compensation of 0.5mm to 1.5mm. Since the centrifugal water pump will experience vibration changes before and after cavitation, if the output shaft of the stepper motor 13 is rigidly connected to the rotary valve core 12, the valve core is prone to jamming due to off-center load, resulting in an increase in the opening control error. After adopting the cross-slider type flexible coupling 19, the stepping pitch of the stepper motor 13 can be accurately and smoothly transmitted to the rotary valve core 12, while isolating part of the vibration of the pump casing 1 and the high-frequency micro-vibration of the motor itself, reducing the wear of the mating surface between the valve core and the valve seat hole 5. During prototype testing, within the effective range of pump body vibration velocity from 2.5 mm / s to 4.0 mm / s, the 12-degree feedback error of the rotary valve core was controlled within 1.2°, meeting the requirements for bypass return flow regulation.

[0023] The rotary valve core 12 is cylindrical; wherein, the rotary valve core 12 is installed in the valve seat hole 5 by interference fit; The rotary valve core 12 adopts a cylindrical structure. The purpose is to ensure that when the valve core rotates around its own axis, the outer circle of the valve core and the inner wall of the valve seat hole 5 maintain a constant geometric relationship, which facilitates the continuous adjustment of the effective flow cross-sectional area of ​​the bypass return channel 4 by the through hole 14. In this embodiment, the rotary valve core 12 can be made of 2Cr13 stainless steel or 40Cr steel with surface hardening treatment. An interference fit of 0.01mm to 0.03mm is provided between the outer diameter of the valve core and the diameter of the valve seat hole 5. The rotary valve core 12 is installed in the valve seat hole 5 by low temperature assembly or heat fitting. The interference fit here not only fixes the position of the valve core, but also forms a stable slewing bearing boundary to limit the leakage of high pressure backflow liquid along the outer circle of the valve core. To ensure the valve core can rotate, the interference fit installation in this embodiment is preferably understood as forming a slight interference preload between the outer circle of the valve core and the elastic anti-friction support layer or thin-walled bushing provided in the valve seat hole 5, and the bushing or support layer then forms a fixed fit with the valve seat hole 5; after assembly, the valve core rotates intermittently at low speed and small angle within the preload support boundary, rather than rotating continuously at high speed under a rigid, gapless metal-to-metal clamping state; This interference fit is mainly used to establish a sealing preload and gap elimination effect, so that when the valve core rotates under the drive of the stepper motor 13, there is no obvious external leakage, nor is there opening hysteresis due to excessive fit clearance; a local anti-friction liner made of polytetrafluoroethylene, graphite-filled base or sintered oil-containing material can be set in the valve seat hole 5, or a finely ground mating surface and lubricating medium can be used in the valve core rotation area to keep the valve core rotation starting torque within the output range of the stepper motor 13; The surface roughness is preferably controlled below Ra0.8; compared with cone valves or flat valves, cylindrical valve cores are easier to achieve continuous angle adjustment under the same driving torque, and the relationship between flow area and rotation angle is easier to calibrate; in the experiment, by calibrating the bypass flow corresponding to different rotation angles, a correspondence table between rotation angle and flow can be established, which can be called by controller 15, so that there is a repeatable correspondence between the control algorithm and the mechanical actuator; Thus, a clear causal relationship is formed between the cylindrical valve core, the interference preload support boundary, and the intermittent rotation of the stepper motor 13: because a preloaded cylindrical rotary structure is adopted, controllable rotation can be maintained while ensuring sealing and gap elimination, thereby enabling the bypass return flow to have a basis for repeated adjustment.

[0024] The diameter of through hole 14 is equal to the diameter of bypass return channel 4; The diameter of the through hole 14 on the rotary valve core 12 is set to be equal to the diameter of the bypass return channel 4. The purpose is to make the through hole 14 and the bypass return channel 4 form an approximately equal diameter connection when the valve core is rotated to the fully open position, thereby reducing the additional losses caused by sudden local contraction and expansion. Taking the prototype with a bypass return channel 4 diameter of 10mm as an example, the diameter of the through hole 14 of the rotary valve core 12 is also set to 10mm, and the machining tolerance is controlled within the range of ±0.03mm. When the valve core is in the fully open position, the fluid enters the bypass return channel 4 from the high pressure zone of the volute flow channel 3, and enters the suction flow channel 2 through the valve core through hole 14. The flow path cross-section changes smoothly and there is no sudden change in size, which is beneficial for the controller 15 to calculate the compensation flow based on the pressure difference and the maximum flow cross-sectional area. If the diameter of the through hole 14 is smaller than the diameter of the bypass return channel 4, even if the valve core is turned to the fully open position, a fixed throttling point will be formed at the position of the through hole 14, which will limit the maximum compensation flow and prevent it from reaching the design maximum value, thus affecting the suppression capability under severe cavitation conditions. If the diameter of the through hole 14 is larger than the diameter of the bypass return channel 4, the valve core wall thickness will decrease, the strength will decrease, and the relationship between the angle and the effective opening will show a nonlinear abrupt change, which is not conducive to fine control. Actual measurements show that when using the equal diameter design, the flow coefficient of the valve core when fully open is increased by about 8% to 13% compared with the reduced diameter design, and the flow regulation repeatability in the small opening range is more stable.

[0025] Example 2:

[0026] like Figure 6 As shown, the anti-cavitation centrifugal water pump operation method based on flow channel optimization includes: S1. During the initial stable operation phase of the water pump without cavitation, the stator current of the main drive motor 8 is continuously collected, the fundamental effective value of the stator current is extracted as the reference stable current, and the rotational speed of the main shaft 6 is recorded. S2. During the pump's variable operating condition phase, the instantaneous fluctuating current of the main drive motor's 8 stator windings is collected in real time according to the preset sampling period. The transient impact frequency band in the instantaneous fluctuating current is extracted by filtering, and the difference between the instantaneous fluctuating current and the reference stable current extracted in step S1 is used to obtain the current fluctuation amount. S3. The sum of the squares of the current fluctuations over a preset number of consecutive sampling periods is divided by the total number of preset sampling periods to calculate the current variance; where the current variance represents the cavitation impact intensity. S4. Determine the relationship between the current variance and the preset safety threshold. When the current variance is greater than the preset safety threshold, subtract the preset safety threshold from the current variance to obtain the overshoot. When the current variance is less than or equal to the preset safety threshold, do not increase the rotation angle of the rotary valve core 12. S5. When the current variance is greater than the preset safety threshold, according to the current spindle speed 6, call the pre-calibrated speed and conversion coefficient correspondence table, look up the table to obtain the flow conversion coefficient; multiply the overshoot by the flow conversion coefficient to obtain the compensation flow; combine the preset maximum flow cross-sectional area of ​​the bypass return channel 4 and the fluid pressure difference between the volute flow channel 3 and the suction flow channel 2 to calculate the target effective flow cross-sectional area, and then convert it into the target rotation angle required for the rotary valve core 12 to rotate, and control the stepper motor 13 to rotate to the target rotation angle; This operating method is used to invert the degree of cavitation impact based on the electrical parameters of the main drive motor 8 without setting up pressure sensors and vibration sensors in the pump chamber, and to control the stepper motor 13 to adjust the bypass return flow. In this invention, stator current refers to the phase current or line current of the three-phase stator winding of the main drive motor 8, which can be acquired by a Hall current sensor or a current transformer; reference steady current refers to the reference value of the fundamental effective value of the stator current when the water pump is free from cavitation, has a stable speed, and a flow rate close to the set value; current variance is an index obtained by energizing the fluctuation of the stator current relative to the reference steady current, and is used to characterize the intensity of torque pulsation caused by bubble collapse. In specific implementation, in S1, controller 15 continuously acquires the stator current of the main drive motor 8 at a sampling frequency of 5kHz to 20kHz, uses digital filtering to extract the fundamental effective value at 50Hz or the corresponding power supply frequency, and records it as the reference stable current I0. Simultaneously, it reads the speed n fed back from the speed sensor or frequency converter and sets it... And n are stored in controller 15; After entering the variable operating condition, S2 is executed, and controller 15 reads the instantaneous fluctuating current according to the preset sampling period. ,Will and The difference is used to obtain the current fluctuation. When executing S3, calculate within M consecutive sampling periods. The sum of squares divided by M gives the current variance. The parameter M is the preset total number of continuous sampling periods, which can be selected as 128, 256 or 512. When executing S4, With safety threshold In comparison, if Greater than Then calculate the overshoot:

[0027] like Less than or equal to If the current angle of the rotary valve core 12 is maintained, then when S5 is executed, the pre-calibrated flow conversion coefficient is called according to the rotational speed n. The compensated flow is obtained:

[0028] Combined with the maximum flow cross-sectional area of ​​the bypass return channel 4 and the fluid pressure difference between the high-pressure zone of the volute flow channel 3 and the low-pressure zone of the suction flow channel 2. The target valve core angle can be derived by reversing the relationship between flow rate and valve opening or by using the orifice flow equation. The controller 15 outputs a corresponding number of pulses to the stepper motor 13, causing the rotary valve core 12 to rotate to... ; To ensure clear data flow of the control logic in environments where there are no built-in pressure sensors in the hardware, fluid pressure difference... The specific algorithm path obtained is as follows: the controller 15 uses the continuously read spindle speed n as the addressing index to directly call the two-dimensional mapping table of water pump spindle speed 6 - cavitation-free pressure difference estimation established by offline testing in the memory to extract the corresponding data, and uses it as the benchmark for module operation. Input variables; Program algorithms rely on current With the extracted compensation flow First, the effective flow cross-sectional area required for the target is obtained through reverse calculation. Then, piecewise second-order interpolation addressing is performed within a pre-stored discrete coordinate array of this area and the valve actuator angle. Finally, the smooth and uninterrupted target valve core angle is calculated and established. This step involves introducing an explicit formula for the outflow of incompressible fluid from the orifice:

[0029] Used to calculate the target effective flow cross-sectional area ,in, For the target effective flow cross-sectional area, Preset the overall flow coefficient for the bypass return path included in the constant range of controller 15. For the input working fluid density, The calculated compensation flow rate, The pressure difference is the fluid pressure difference between the high-pressure zone of the volute flow channel and the low-pressure zone of the suction flow channel. Based on the above formula, the solution is directly substituted, eliminating the defect of relying solely on empirical calibration of the opening degree, and establishing a mathematical calculation process from stator electrical parameters to rotation opening degree command. After adopting this method, every piece of data in the controller 15 processing link participates in subsequent calculations. The reference steady current is used to calculate the current fluctuation, the current fluctuation is used to calculate the variance, the variance is used to calculate the overshoot, the overshoot is converted to the compensation flow through speed correlation, and the compensation flow is then mapped to the valve core angle. Therefore, the method has executability and parameter transmission integrity. In the prototype test, with a sampling frequency of 10kHz, M of 256, and a safety threshold of 1.35 times the average variance of the stable and damage-free working condition, the valve opening can be adjusted within 2 seconds after a sudden drop in inlet pressure of 0.03MPa. To ensure that the setting of the above parameters and thresholds is clear and repeatable, S1 to S5 are preferably executed in the following order: After the equipment is first installed or overhauled, select a working condition with sufficient inlet pressure, flow rate between 85% and 100% of rated flow rate, and vibration and noise within the normal range as the cavitation-free calibration working condition; Under this working condition, the controller 15 continuously records the effective value of the stator current fundamental wave for no less than 30 seconds, and calculates the average value according to the speed range to form a reference stable current library; The physical meaning of the reference stable current is the steady-state energy consumption level of the motor when the mechanical load is not affected by cavitation impact. The current deviation at any subsequent moment is calculated with reference to this reference. The preset safety threshold is not arbitrarily given, but is determined by the statistical results of the current variance under the non-cavitation calibration condition. The controller 15 first averages the current variance within multiple time windows, and then adds a safety margin. The safety margin is preferably 20% to 50% of the average value, thereby obtaining a comparison threshold that can distinguish between normal hydraulic pulsations and abnormal cavitation pulsations. Flow conversion factor The physical meaning is the target compensation flow increment corresponding to the unit current variance overshoot. Its source is the prototype calibration test: at different speeds, the bypass return channel 4 is opened step-by-step, and the correspondence between the valve core angle, bypass flow rate, and current variance decrease is recorded. A lookup table is then established according to the speed. During operation, the controller 15 prioritizes looking up the table according to the current speed. If the current speed falls between two calibrated speeds, then take two adjacent sets of calibrated values ​​and perform linear interpolation to avoid conversion jumps. For the process of inferring the target rotation angle from the compensated flow rate in S5, it is preferred to process it in three steps: First, based on the estimated pressure difference between the high pressure zone of the current volute flow channel 3 and the low pressure zone of the suction flow channel 2, determine the maximum achievable flow range of the bypass return flow channel 4 under the current pressure difference. The required compensation flow rate is then compared with the maximum achievable flow rate range. When the required compensation flow rate exceeds the achievable upper limit, the target value is limited to the flow rate corresponding to the upper limit to prevent the controller 15 from issuing an unexecutable command. The minimum valve core rotation angle that meets the flow rate requirement is found from the pre-calibrated angle-flow rate correspondence table and converted into the number of pulses of the stepper motor 13. The angle-flow correspondence table is preferably discretely calibrated at 5° or smaller angle intervals, and more densely calibrated points are used in the small opening region to improve the adjustment accuracy in the early stage of slight cavitation; if S4 determines... Less than or equal to The meaning of maintaining the current operating state of the rotary valve core 12 is that the controller 15 does not add a new valve opening pulse in this sampling window, while continuing to retain the monitoring and comparison functions of subsequent windows, rather than stopping the entire detection process. With the above additional constraints, the source, logical function and data flow of the reference stable current, preset safety threshold, flow conversion factor, target rotation angle and corresponding execution pulse are all clearly defined, which can avoid the method description from being limited to the functional or mechanistic descriptions at the result level.

[0030] Step S5 is followed by: S601. After controlling the stepper motor 13 to rotate to the target rotation angle, monitor the instantaneous change current of the main drive motor 8. S602. After the bypass return channel 4 is opened and the preset flow field stabilization delay time has elapsed, the current fluctuation of the current sampling period is calculated. S603. Recalculate the current variance. When the current variance drops to within the preset safety threshold, maintain the current rotation angle of the stepper motor 13. After the valve core opening adjustment is completed, the high-pressure fluid in the volute flow channel 3 will enter the suction flow channel 2 through the bypass return flow channel 4. This process corresponds to S601 to S603. In order to ensure that the return liquid can cut into the guide micro-groove 10 on the back of the blade, the orientation of the outlet of the bypass return flow channel 4 in the suction flow channel 2 is preferably to form an angle of 10° to 35° with the circumferential velocity direction of the impeller 9 inlet, so that the return liquid jet obtains a velocity component that matches the flow direction on the back of the blade near the inlet of the impeller 9. Here, the flow is cut into the guide microchannel 10 under the action of centrifugal force generated by the rotation of impeller 9. In engineering terms, it is preferred to understand that the relative velocity field established by the rotation of impeller 9, the pressure difference in the blade passage, and the near-wall induced flow work together to enable the return jet to obtain a wall-attached velocity component that develops downstream along the channel when it is close to the back of the blade, so as to enter the guide microchannel 10. The key point is the traction and orientation effect of the rotating impeller 9 on the local flow field, rather than relying solely on centrifugal force to radially press the fluid into the microchannel. After the high-pressure fluid enters the flow guide microchannel 10, the local flow velocity increases due to the decrease in the cross-section of the microchannel along the flow path, and the flow state near the wall changes, forming a local micro boundary layer separation air cushion in the channel; the meaning of this micro boundary layer separation air cushion in this invention is that the backflowing high-pressure liquid forms a local isolation flow layer with a certain thickness and velocity gradient in the near-wall area on the back of the blade, causing the bubbles that have been formed or are about to adhere to the metal surface to deviate from the wall surface. This does not require the formation of a stable, large-area cavity, nor does it require the retention of a macroscopic gas cushion layer on the blade surface. Instead, it requires the formation of a short-term, localized low-adhesion isolation zone between the local high-energy wall-adhering liquid layer and the bubble-rich layer to change the trajectory of the bubbles moving against the wall. After the remaining low-pressure bubbles are pushed to the mainstream area away from the blade's metal surface, even if they collapse, their impact energy is absorbed by the surrounding liquid and does not directly act on the blade surface. By comparing high-speed photography and blade surface weight loss tests, it was found that after setting up the flow-guiding microgroove 10 and introducing controlled bypass backflow, the density of typical pits in the 0 to 20 mm range on the back of the blade inlet was significantly reduced, and the mass loss after 72 h accelerated cavitation test was reduced by about 20% to 28% compared with the prototype without microgroove structure. The flow mechanisms of S601 to S603 can be understood in the observable order as follows: In S601, after the controller 15 turns the valve core to the target angle, the bypass return channel 4 establishes a stable pressure difference driven flow from the high pressure area of ​​the volute to the low pressure area of ​​the suction. The high pressure fluid does not diffuse randomly into the suction channel 2, but enters the area near the inlet of the impeller 9 in the form of a directional jet restricted by the outlet orientation. After entering, the jet first exchanges momentum with the main suction flow, and then moves close to the back of the blade under the action of the relative velocity field induced by the rotation of the impeller 9. When the high-pressure fluid enters the guide microchannel 10 in S602, the fluid velocity gradient near the bottom of the channel increases due to the constraint effect of the microchannel on the near-wall fluid. A local velocity transition zone is formed between the high-energy liquid near the channel opening and the original low-velocity near-wall liquid. The local micro boundary layer separation air cushion referred to in this embodiment refers to the state in which the velocity transition zone isolates the bubbles that are originally easy to accumulate near the wall from the metal wall for a short time. Its essence is a local isolation zone formed between the high-energy liquid layer attached to the wall and the bubble enrichment layer, rather than a continuously closed macroscopic air chamber. Entering S603, when the remaining low-pressure bubbles move downstream along the back of the blade, due to the shearing and pushing effect of the high-energy liquid layer near the wall, the trajectory of the bubble center shifts towards the mainstream area; once the bubbles leave the extremely thin boundary layer near the metal surface, their subsequent collapse locations will appear more often at the location away from the wall, so that the impact load is no longer concentrated on the metal surface of the blade. To facilitate engineering implementation, the following phenomena can be used to verify whether the process has been established: First, under high-speed photography, it can be observed that the near-wall bubble adhesion time on the back of the blade is shortened; Second, under the same inlet pressure, after the bypass is opened, the pitting on the inlet section on the back of the blade is reduced rather than the entire area changing simultaneously; Third, while the current variance decreases, the peak value of the pump body's high-frequency noise is simultaneously reduced. The above phenomena collectively demonstrate that the micro boundary layer separation air cushion has a clear physical meaning, formation conditions, and technical role in this invention, and is not an abstract functional description. From a causal perspective, it is precisely because the bypass return jet is guided to the back of the blade in the relative velocity field induced by the rotating impeller 9 and is constrained near the wall by the gradually shallowing guide microchannel 10 that a local high-energy wall-adhering liquid layer is formed near the blade surface. Furthermore, because this wall-adhering liquid layer increases the liquid momentum near the wall and shortens the residence time of the bubbles near the wall, the bubbles tend to collapse at the distance from the wall, ultimately reducing the direct impact on the metal surface of the blade.

[0031] Step S5 is followed by: S701. Real-time monitoring of current variance; wherein, the current variance is compared with a preset safety threshold for determination; when the current variance is less than or equal to the preset safety threshold, the difference between the current variance and the preset safety threshold is calculated to obtain a negative deviation; when the current variance is greater than the preset safety threshold, return to step S4. S702. Multiply the absolute value of the negative deviation by the recovery coefficient to calculate the return rotation angle of the rotary valve core 12. S703, control the stepper motor 13 to rotate in reverse and adjust the rotation angle to reduce the cross-sectional area of ​​the channel; wherein, repeatedly adjust until the current variance stabilizes at the preset safety threshold critical point; This operating method is used to avoid the loss of volumetric efficiency caused by the valve core maintaining a large opening for a long time; after executing S5, the controller 15 continues to monitor the current variance at the same sampling frequency. And execute S701; when Less than or equal to the safety threshold At that time, calculate the negative deviation:

[0032] At this time, ε is zero or negative; when When the value exceeds the safety threshold, the system does not execute a callback but directly returns to S4 to recalculate the compensation opening; in S702, controller 15 multiplies the absolute value of the negative deviation by the recovery coefficient. The rotation angle of the rotary valve core 12 is obtained. Coefficient of recovery It can be calibrated according to pump type, speed and backflow sensitivity, with typical values ​​ranging from 5° / variance unit to 25° / variance unit; When S703 is executed, the controller 15 sends a reverse pulse to the stepper motor 13, causing the valve core to press... By reducing the effective cross-sectional area of ​​the bypass return channel 4, and then recalculating the current variance and repeating the judgment, the system can be kept stable near the safety threshold. In this method, there is a clear correspondence between real-time monitoring, current variance comparison, negative deviation calculation, recovery coefficient conversion and stepper motor 13 reverse control, and there are no invalid parameters. Compared with the fixed large opening anti-cavitation method, this back-off method can reduce the excess backflow while meeting the cavitation suppression requirements. The prototype ran continuously for 8 hours under fluctuating inlet pressure. After adopting the back-off strategy, the average bypass flow was reduced by about 18% to 30% compared with the control method of only opening and not closing. The effective flow of the pump outlet was restored and the head fluctuation range was reduced. To avoid ambiguity between the sign of the negative deviation and the reverse action of the motor, this embodiment uses the negative deviation obtained in S701 as the determination quantity for the existence of a callback demand, and its absolute value as the input quantity for calculating the callback amplitude; that is, when Less than or equal to the safety threshold At that time, the controller 15 recognizes that the system has entered the recoverable opening range, and then inputs |ε| into the callback calculation module; the function of this module is not to re-determine whether cavitation exists, but to determine how much bypass opening should be recovered based on the current safety margin. Its preferred logic structure includes: a deviation determination unit, an amplitude conversion unit, and an execution limiting unit; the deviation determination unit receives the current current variance and the safety threshold, and outputs a status signal indicating whether to maintain the opening degree or allow callback; the amplitude conversion unit receives |ε|, the current speed, and the recovery coefficient. Output the theoretical callback angle; After the execution limiting unit combines the judgment function for the variance change trend within a specific number of sampling windows, the minimum step size parameter, and the single maximum callback angle limit condition, and performs rigorous calculation code to prevent out-of-bounds constraints on the theoretical callback angle, the closing action command is officially sent to the hardware control port. The code flow and rate limiting logic based on software are explained in detail: A circular queue storage area is established in the system data buffer to store the historical variance changes of the sampling windows of the last three periods. The verification program checks the data in this temporary queue in real time. Only when the variance stored in the queue shows a continuous and non-increasing steady-state sequence will the verifier port output a master enable high-level signal that allows subsequent actions to be executed. Within this constraint framework, preferably, it is further necessary to ensure that the results calculated from at least two consecutive newly entered sampling window periods can accurately match the target data. Less than or equal to the safety threshold The fundamental principle is to avoid frequent reciprocating chatter and wear of mechanical actuators caused by sudden changes in waveforms within individual random sampling windows at the system's underlying level; Meanwhile, to prevent the valve core from retracting unexpectedly, a trimming and limiting algorithm is incorporated into the pre-processing stage before issuing the terminal anti-pulse command. If the calculated single theoretical conversion pullback angle exceeds the maximum limit ratio of 20% to 35% of its current relative effective opening range, or even exceeds the rated extreme value standard of valve angle set at 5° to 12° in the absolute operating dimension, the control end will determine it as an over-threshold trigger and directly perform upper limit amplitude constraint processing on the variable according to the aforementioned corresponding tolerance upper limit. This fundamentally avoids the danger of insufficient pressure supply and aggravated cavitation caused by an excessively small bypass diameter at the execution level. By implementing multi-point interception planning at the detailed level of the above system execution, the causal transformation of operating parameters into physical execution becomes more rigorous and traceable: relying on the system to capture the multi-dimensional continuous variance reduction trend in real time to achieve fault tolerance enable confirmation, and relying on precise locking of over-limit quantities to limit the amplitude control to ensure the operational safety boundary of mechanical components, this recovery system solution becomes a standard method that can be operated and implemented through code programming.

[0033] In step S2, the real-time acquisition of the instantaneous fluctuation current of the 8 stator windings of the main drive motor specifically includes: forcibly filtering out the power supply fundamental frequency and low-frequency components of mechanical interference below the preset cutoff frequency using a high-pass digital filter; extracting the transient impulse frequency band in the preset high-frequency range using a band-pass digital filter; and multiplying the extreme value of the envelope of the extracted transient impulse frequency band by a preset gain coefficient, and using this product as an additional term superimposed on the difference in step S2 to form the final current fluctuation amount. The physical basis of step S2 is defined; when cavitation occurs in the centrifugal water pump, the steam bubbles formed near the surface of the impeller 9 will collapse rapidly after entering the local high-pressure zone. The collapse process generates micro-jet and local impact load, which is applied to the impeller 9 and transmitted to the main shaft 6, causing the main shaft 6 to be subjected to high-frequency nonlinear torque pulsation. For a pump unit driven by a main drive motor 8, the electromagnetic torque output by the motor needs to be dynamically balanced with the mechanical load torque. Therefore, the torque pulsation on the mechanical side will be reflected in the stator current. Based on this electromechanical coupling relationship, this invention uses the fluctuation part of the instantaneous variable current relative to the reference stable current as the electrical characterization quantity of cavitation impact. To improve the accuracy of the inversion, the power frequency component can be filtered out and the high frequency disturbance can be enhanced in the controller 15 to distinguish the low frequency current changes caused by power grid fluctuations and ordinary load changes from the high frequency nonlinear current changes caused by bubble collapse. To ensure that the frequency blocking boundary process has a clear quantitative judgment standard, the power frequency component filtering is specifically manifested at the code execution level as follows: the controller 15 calls the high-pass digital filter algorithm to lock the characteristic cutoff frequency boundary threshold at 150Hz, and forcibly cut off the 50Hz power supply fundamental, even multiple harmonics and large amplitude mechanical interference items below 100Hz caused by the impeller 9 rotation speed frequency. Correspondingly, the high-frequency disturbance enhancement processing involves configuring a bandpass digital filter to further extract the isolated transient impulse frequency band in the 500Hz to 2000Hz range, and assigning the extreme values ​​of the envelope of this frequency band to a fixed multiplier to achieve a gain operation of 5 to 10 times, thereby ensuring that the evaluation value of the variance of the current dominated by the weak high-frequency sudden energy caused by bubble collapse is guaranteed and eliminating confusion error. Taking a centrifugal water pump prototype driven by a 45kW asynchronous motor as an example, when the inlet pressure gradually decreases to near the point of destructive cavitation, the energy in the torque fluctuation frequency band of the main shaft increases, which is consistent with the increasing trend of the mean square value of the stator current fluctuation. The correlation coefficient between the two can reach more than 0.8. The results demonstrate that using instantaneous variable current to calculate current fluctuation and current variance has a clear physical basis, can be used to characterize cavitation impact intensity, and provide input for subsequent valve core angle control.

[0034] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A cavitation-resistant centrifugal water pump device based on flow channel optimization, characterized in that, include: The pump casing (1) has an internally cast suction channel (2) and volute channel (3); the side wall of the pump casing (1) is machined with a bypass return channel (4); the bypass return channel (4) connects the volute channel (3) and the suction channel (2); a valve seat hole (5) is vertically opened in the middle section of the bypass return channel (4). The main shaft (6) is supported in the bearing seat (7) provided on the pump housing (1); the main shaft (6) is driven to rotate by the main drive motor (8); An impeller (9) is fixedly connected to the end of the main shaft (6) that extends into the pump casing (1); the impeller (9) includes multiple blades; the back of the blades of the impeller (9) is milled with flow guide microgrooves (10); the flow guide microgrooves (10) are arranged in parallel; The valve assembly (11) includes a rotary valve core (12) and a stepper motor (13); the rotary valve core (12) is installed in the valve seat hole (5); the side wall of the rotary valve core (12) has a through hole (14); the stepper motor (13) is fixed to the outer surface of the pump housing (1); the output shaft of the stepper motor (13) is connected to the end of the rotary valve core (12); The controller (15) controls the stepper motor (13); the controller (15) continuously collects the stator current of the main drive motor (8) to extract the reference stable current, and collects the instantaneous variable current in real time under changing working conditions, and calculates the variance of the current fluctuation after subtracting the instantaneous variable current from the reference stable current as the current variance representing the cavitation impact intensity. When the current variance is greater than the preset safety threshold, the target effective flow cross-sectional area is calculated by combining the flow conversion coefficient, the maximum flow cross-sectional area of ​​the bypass return channel (4) and the fluid pressure difference, and then converted into the rotation angle of the stepper motor (13).

2. The anti-cavitation centrifugal water pump device based on flow channel optimization according to claim 1, characterized in that, The direction of the flow-guiding microgroove (10) coincides with the relative velocity streamline of the fluid on the back of the blade; the depth of the flow-guiding microgroove (10) gradually becomes shallower along the direction of water flow from the inlet to the outlet until it smoothly transitions to the surface of the blade.

3. The anti-cavitation centrifugal water pump device based on flow channel optimization according to claim 1, characterized in that, The main shaft (6) is supported in the bearing housing (7) by an angular contact ball bearing (16); wherein, the impeller (9) is fixedly connected to the main shaft (6) by a flat key (17) and a lock nut (18); the impeller (9) and the inner wall of the pump casing (1) maintain a clearance fit.

4. The anti-cavitation centrifugal water pump device based on flow channel optimization according to claim 1, characterized in that, The output shaft of the stepper motor (13) is connected to the end of the rotary valve core (12) via a cross-slider type flexible coupling (19); the cross-slider type flexible coupling (19) is used to absorb the vibration generated by the motor operation.

5. The anti-cavitation centrifugal water pump device based on flow channel optimization according to claim 4, characterized in that, The rotary valve core (12) is cylindrical; the rotary valve core (12) is installed in the valve seat hole (5) by interference fit.

6. The anti-cavitation centrifugal water pump device based on flow channel optimization according to claim 5, characterized in that, The diameter of the through hole (14) is equal to the diameter of the bypass return channel (4).

7. An operating method for the anti-cavitation centrifugal water pump device based on flow channel optimization as described in claim 1, characterized in that, include: S1. During the initial cavitation-free stable operation phase of the water pump, the stator current of the main drive motor (8) is continuously collected, the fundamental effective value of the stator current is extracted as the reference stable current, and the rotational speed of the main shaft (6) is recorded. S2. During the pump's variable operating condition phase, the instantaneous fluctuating current of the stator winding of the main drive motor (8) is collected in real time according to the preset sampling period; the transient impact frequency band in the instantaneous fluctuating current is extracted by filtering, and the difference between the instantaneous fluctuating current and the reference stable current extracted in step S1 is used to obtain the current fluctuation amount. S3. The sum of the squares of the current fluctuations over a predetermined number of consecutive sampling periods is divided by the total number of the predetermined number of sampling periods to calculate the current variance; wherein, the current variance represents the cavitation impact intensity. S4. Determine the relationship between the current variance and the preset safety threshold; when the current variance is greater than the preset safety threshold, subtract the preset safety threshold from the current variance to obtain the overshoot; when the current variance is less than or equal to the preset safety threshold, do not increase the rotation angle of the rotary valve core (12). S5. When the current variance is greater than the preset safety threshold, according to the current rotational speed of the main shaft (6), call the pre-calibrated rotational speed and conversion coefficient correspondence table, and look up the flow conversion coefficient; multiply the overshoot by the flow conversion coefficient to obtain the compensation flow rate; calculate the flow rate by combining the preset maximum flow cross-sectional area of ​​the bypass return channel (4) and the fluid pressure difference between the volute channel (3) and the suction channel (2), and use the formula The target effective flow cross-sectional area was calculated. , in the formula To compensate for the data usage, Preset the overall flow coefficient for the bypass return channel. For fluid pressure difference, The working fluid density is then used to perform piecewise second-order interpolation addressing within a pre-stored discrete coordinate array of the target effective flow cross-sectional area and the valve actuator rotation angle, which is converted into the target rotation angle required for the rotary valve core (12) to rotate, and the stepper motor (13) is controlled to rotate to the target rotation angle.

8. The operating method according to claim 7, characterized in that, Following step S5: S601. After controlling the stepper motor (13) to rotate to the target rotation angle, monitor the instantaneous change current of the main drive motor (8); S602. After the bypass return channel (4) is opened and a preset flow field stabilization delay time has elapsed, the current fluctuation of the current sampling period is calculated. S603. Recalculate the current variance. When the current variance drops to within a preset safety threshold, maintain the current rotation angle of the stepper motor (13).

9. The operating method according to claim 7, characterized in that, Following step S5: S701. Monitor the current variance in real time; wherein, the current variance is compared with the preset safety threshold; when the current variance is less than or equal to the preset safety threshold, the difference between the current variance and the preset safety threshold is calculated to obtain a negative deviation; when the current variance is greater than the preset safety threshold, return to step S4. S702, Multiply the absolute value of the negative deviation by the recovery coefficient to calculate the back-rotation angle of the rotary valve core (12); S703, control the stepper motor (13) to rotate in the opposite direction by the callback rotation angle to reduce the channel flow cross-sectional area; wherein, repeatedly adjust until the current variance is stable at the preset safety threshold critical point.

10. The operating method according to claim 7, characterized in that, In step S2, the real-time acquisition of the instantaneous fluctuation current of the stator winding of the main drive motor (8) specifically includes: forcibly filtering out the power supply fundamental wave and low-frequency components of mechanical interference below the preset cutoff frequency through a high-pass digital filter; extracting the transient impulse frequency band of the preset high-frequency range using a band-pass digital filter; and multiplying the extreme value of the envelope of the extracted transient impulse frequency band by a preset gain coefficient, and using the product as an additional term superimposed on the difference in step S2 to form the final current fluctuation amount.

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