A water pump impeller with good flow guiding property

Abstract

This invention discloses a water pump impeller with good flow guiding properties, including an upper cover plate and a lower cover plate opposite to the pump shaft. Multiple main blades and multiple guide shell blades are circumferentially spaced between the upper and lower cover plates. The main blades have a pressure surface and a back pressure surface. The guide shell blades are located between adjacent main blades and are constructed as hollow shells integrally formed with the upper cover plate. An array of throttling orifices is formed on the flow-facing wall of the guide shell blades facing the back pressure surface, and a return channel communicating with the guide cavity is formed on the side of the guide shell blades facing the lower cover plate. The throttling orifice array is used to draw in low-energy fluid accumulated in the rear separation zone of the back pressure surface of the main blades. The drawn-in fluid flows sequentially through the guide cavity and the return channel before re-entering the main flow. This invention can actively draw in and remove low-energy fluid from the back pressure surface of the main blades while simultaneously achieving orderly fluid circulation, thus improving the pump's hydraulic efficiency and operational stability.

Description

Technical Field

[0001] This invention belongs to the technical field of pump body impeller structure, specifically a water pump impeller with good flow guiding properties. Background Technology

[0002] The impeller is a core component of a pump, and its structure directly determines the pump's efficiency, head, and operational stability. Therefore, optimizing the impeller structure to improve the pump's hydraulic efficiency is an important factor to consider when designing the impeller structure.

[0003] According to the search, Chinese invention patent CN110410359B discloses an "impeller, centrifugal pump and electric pump". This patent achieves a certain improvement effect by adding auxiliary blades or diverting blades between adjacent main blades to suppress flow separation on the back pressure surface.

[0004] However, this scheme has the following shortcomings: the auxiliary blades are solid structures and can only play a guiding role, but cannot effectively draw in and remove the low-energy fluid that has been generated; at the same time, the disturbed fluid remains in the flow channel and fails to achieve orderly circulation, so the improvement in efficiency is limited.

[0005] Therefore, it is necessary to design an impeller structure that can actively draw in and remove low-energy fluid from the back pressure surface of the main blades while achieving orderly fluid circulation, so as to further improve the hydraulic efficiency and operational stability of the pump. Summary of the Invention

[0006] To address the problems mentioned in the background section, the present invention adopts the following technical solution.

[0007] A water pump impeller with good flow guiding properties includes an upper cover plate and a lower cover plate opposite to the pump shaft. The upper and lower cover plates together define a fluid chamber. An axial inlet communicating with the fluid chamber is located at the center of the lower cover plate, and a radial outlet is formed at the outer periphery of the fluid chamber. Multiple main blades and multiple guide vanes are circumferentially spaced between the upper and lower cover plates. A flow channel extending from the axial inlet to the radial outlet is formed between adjacent main blades. The main blades have a pressure surface and a back pressure surface. The guide vanes are located between adjacent main blades. Between the main blades, the guide shell blades are constructed as hollow shells integrally formed with the upper cover plate, forming a guide cavity inside. A throttling orifice array is opened on the front wall of the guide shell blades facing the back pressure surface, and a return channel communicating with the guide cavity is opened on the side of the guide shell blades facing the lower cover plate. The outlet of the return channel is connected to the fluid inlet in the axial direction. The throttling orifice array is used to draw in the low-energy fluid accumulated in the middle and rear separation zone of the back pressure surface of the main blades. The drawn fluid flows back into the mainstream after passing through the guide cavity and the return channel in sequence.

[0008] Compared with the prior art, the beneficial effects of the present invention are as follows: Improving hydraulic efficiency: By setting an array of throttling holes on the blades of the guide shell, the natural pressure difference between the back pressure surface and the axial inlet during impeller rotation is used to passively draw low-energy fluid from the rear separation zone of the back pressure surface of the main blade. The low-energy fluid is then orderly transported through the guide cavity and return channel to the vicinity of the axial inlet and re-enters the mainstream, avoiding eddy current losses caused by the retention of low-energy fluid in the flow channel, thereby significantly improving the impeller's head and hydraulic efficiency.

[0009] Improved operational stability: The return channel directs the fluid in the guide cavity to the axial inlet area, making the pressure distribution on both sides of the impeller more balanced. This effectively reduces the additional axial thrust caused by the accumulation of low-energy fluid on the back pressure surface, reduces bearing load and vibration, and extends the service life of the pump unit.

[0010] Improved flow quality: The guide shell blades and the upper cover plate are integrally molded, which not only ensures the sealing of the hollow shell, but also simplifies the manufacturing process. The guide shell blades are located between adjacent main blades. On the one hand, they play a guiding role, and on the other hand, the throttling hole array on the flow-facing wall is specifically designed to draw low-energy fluid from the back pressure surface. The two work together to effectively suppress flow separation, improve the flow uniformity inside the impeller, and reduce vibration and noise. Attached Figure Description

[0011] Figure 1 This is a three-dimensional structural diagram of the pump in this invention.

[0012] Figure 2 This is a partial cross-sectional three-dimensional structural diagram of the pump in this invention.

[0013] Figure 3 This is a three-dimensional structural diagram of the upper and lower cover plates of the pump in this invention.

[0014] Figure 4 This is a three-dimensional structural diagram of the upper and lower cover plates of the pump in this invention.

[0015] Figure 5 This is a planar structural diagram of the upper and lower cover plates of the pump in this invention.

[0016] Figure 6 This is a planar structural diagram of the pump's main blades and the guide shell blades in this invention.

[0017] Figure 7 In this invention Figure 6 Enlarged view of point A.

[0018] In the diagram, 1. Upper cover plate; 2. Pump shaft; 3. Lower cover plate; 4. Fluid chamber; 5. Axial inlet; 6. Radial outlet; 7. Main blade; 8. Guide shell blade; 9. Pressure surface; 10. Back pressure surface; 11. Guide inner cavity; 12. Throttling orifice array; 13. Return channel; 14. Guide jacket; 15. Placement angle; 16. Wrap angle. Detailed Implementation

[0019] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below in conjunction with specific embodiments.

[0020] It should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention.

[0021] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0022] like Figures 1-7 As shown, a water pump impeller with good flow guiding properties according to the present invention includes an upper cover plate 1, a lower cover plate 3 opposite to the pump shaft 2 of the water pump, the upper cover plate 1 and the lower cover plate 3 together defining a fluid chamber 4; the lower cover plate 3 has an axial inlet 5 communicating with the fluid chamber 4 at its center, and the outer periphery of the fluid chamber 4 forms a radial outlet 6; a plurality of main blades 7 and a plurality of guide shell blades 8 are circumferentially spaced between the upper cover plate 1 and the lower cover plate 3, and a flow channel extending from the axial inlet 5 to the radial outlet 6 is formed between adjacent main blades 7, the main blades 7 having a pressure surface 9 and a back pressure surface 10; the guide shell blades 8 are disposed on the... Between two adjacent main blades 7, the guide shell blade 8 is constructed as a hollow shell integrally formed with the upper cover plate 1, and a guide cavity 11 is formed inside it; a throttling orifice array 12 is opened on the flow-facing wall of the guide shell blade 8 facing the back pressure surface 10, and a return channel 13 communicating with the guide cavity 11 is opened on the side of the guide shell blade 8 facing the lower cover plate 3, and the outlet of the return channel 13 is in fluid communication with the axial inlet 5; the throttling orifice array 12 is used to draw low-energy fluid accumulated in the rear separation zone of the back pressure surface 10 of the main blade 7, and the drawn fluid flows back into the mainstream after passing through the guide cavity 11 and the return channel 13 in sequence.

[0023] In this structure, when the impeller rotates at high speed around the pump shaft 2, the fluid enters the fluid chamber 4 through the axial inlet 5 at the center of the lower cover plate 3, and flows radially to the outlet 6 under the driving action of the main blades 7. During this process, the pressure surface 9 of the main blades 7 pushes the fluid to do work, while the back pressure surface 10 bears the adverse pressure gradient. Especially in the middle and rear region of the impeller, due to the thickening of the boundary layer and the adverse pressure effect, a low-speed separation zone is easily formed near the back pressure surface 10, accumulating a large amount of low-energy fluid. This part of low-energy fluid not only causes energy loss, but also induces flow pulsation and noise, seriously restricting the efficiency and stability of the pump.

[0024] At this point, the guide shell blades 8, arranged between adjacent main blades 7, begin to function. The upstream wall of the guide shell blades 8 faces the back pressure surface 10 of the main blades 7, and the array of throttling orifices 12 formed on it constitutes the intake port for low-energy fluid. Because the total pressure of the fluid in the separation zone of the back pressure surface 10 is low, while the interior of the guide cavity 11 is in a relatively low-pressure state due to the connection between the return channel 13 and the axial inlet 5, a stable pressure difference driving potential energy is formed between the two. Under the action of this pressure difference, the low-energy fluid accumulated in the rear separation zone of the back pressure surface 10 is continuously drawn into the throttling orifice array 12 and flows into the guide cavity 11.

[0025] The drawn-in fluid then flows along the inner cavity 11 of the guide vane 8 and is discharged through the return channel 13 opened on the side of the guide vane 8 facing the lower cover plate 3. The outlet of the return channel 13 is fluidly connected to the axial inlet 5, allowing this portion of the low-energy fluid, after being re-guided, to merge into the mainstream entering from the axial inlet 5 and participate in the impeller's power cycle again. In this way, the low-energy fluid in the separation zone, which would otherwise cause energy loss, is effectively recovered and utilized, reducing the generation of dead zones and vortices in the flow and improving the uniformity of velocity distribution within the flow channel.

[0026] Furthermore, the profile of the upstream wall of the guide shell blade 8 and the profile of the back pressure surface 10 of the main blade 7 remain parallel and equidistant within the distribution section of the throttling orifice array 12, forming a guide interlayer 14 with a gradually decreasing cross-sectional area along the flow direction between the back pressure surface 10 and the upstream wall. This guide interlayer 14, on the one hand, guides the remaining fluid that has not been drawn in to adhere more quickly to the back pressure surface 10, suppressing further expansion of the separation zone; on the other hand, it ensures that the throttling orifice array 12 is always in a suitable suction position, improving suction efficiency.

[0027] In one embodiment, the outer radius of the impeller is defined as R1 in a projection plane perpendicular to the impeller axis, and the radial distance from the starting position of the head of the guide housing blade 8 to the axis is defined as R2. The ratio of R2 to the outer radius of the impeller R1 is 0.62 to 0.78.

[0028] In this structure, the starting position of the head of the guide shell blade 8 is precisely constrained radially. The impeller outer edge radius is defined as R1, and the radial distance from the starting position of the head of the guide shell blade 8 to the impeller axis is defined as R2, with the ratio of R2 to R1 limited to between 0.62 and 0.78. This geometric relationship is established based on in-depth research into the location of the initial flow separation region in the rear part of the back pressure surface 10 of the main blade 7. When the head of the guide shell blade 8 is precisely located in this region, the orifice array 12 can intervene immediately and draw in low-energy fluid clusters that have not yet fully developed, thereby achieving the best separation suppression effect with minimal energy consumption. Therefore, controlling the ratio within the preferred range of 0.62 to 0.78 allows the head of the guide shell blade 8 to be precisely aligned with the leading edge of the high-risk separation zone, initiating active suction before separation deteriorates, thus achieving the optimal balance between suction efficiency and flow disturbance.

[0029] In one embodiment, the orifice array 12 has a non-uniformly distributed orifice area ratio along the radial direction. In the radial middle section region of the guide shell blade 8, the orifice area accounts for 3% to 8% of the frontal wall area of ​​that region. The radial middle section region is defined as the range between 0.65 times the outer radius of the impeller and 0.85 times the outer radius of the impeller. In the radial head region of the guide shell blade 8, the orifice area accounts for less than or equal to 2% of the frontal wall area of ​​that region. The radial head region is defined as the range from the starting position of the head of the guide shell blade 8 to 0.65 times the outer radius of the impeller.

[0030] In this structure, the orifice array 12 adopts a non-uniform distribution strategy in the radial direction to adapt to the differences in the degree of flow separation at different radial positions in the rear part of the back pressure surface 10 of the main blade 7. Specifically, in the radial mid-section region of the guide shell blade 8, that is, the range from 0.65 times the impeller outer edge radius to 0.85 times the impeller outer edge radius, the orifice area accounts for 3% to 8% of the frontal wall area in this region. This radial mid-section region corresponds to the core section where the flow separation is most intense and the low-energy flow accumulates the most. Setting a higher orifice density here can provide sufficient suction flow to remove a large amount of accumulated low-energy fluid in a timely manner, thereby effectively suppressing the formation and development of separation vortices and ensuring the uniformity of velocity distribution in the flow channel.

[0031] Within the radial head region of the guide vane 8, specifically from the initial position of the guide vane 8 to 0.65 times the outer radius of the impeller, the proportion of the opening area to the upstream wall area is controlled to be less than or equal to 2%. This radial head region is located upstream or at the initial edge of the separation zone, where the low-energy fluid is still in the initial accumulation stage and the flow separation is relatively mild. Therefore, only a low suction capacity is needed to maintain the stability of the wall adhesion. Using a lower opening density avoids unnecessary flow loss due to excessive suction, while reducing interference with the main flow field. This allows the suction effect of the guide vane 8 to be concentrated in the most needed area, achieving precise delivery of suction energy.

[0032] By using this radially non-uniformly distributed perforation design, the entire guide shell blade 8 can achieve the optimal suppression effect on the flow separation in the rear part of the back pressure surface 10 of the main blade 7 with minimal suction flow cost, thereby further improving the impeller's guiding efficiency and operational stability.

[0033] In one embodiment, the diameter of a single throttling orifice in the orifice array 12 is 0.5 to 2.0 mm.

[0034] In this structure, the diameter of a single throttling orifice in the orifice array 12 is limited to the range of 0.5 to 2.0 mm. This orifice diameter range allows the fluid to pass through each orifice under the influence of viscous force driven by the cross-wall pressure difference generated by the impeller rotation. The flow rate and pressure difference have an approximately linear relationship, thereby avoiding the sudden flow rate caused by inertial effects and keeping the suction process stable and controllable. This, together with the non-uniform opening area ratio design of the orifice array 12, forms the basis for the fine control of the active suction system.

[0035] In one embodiment, the return channel 13 includes a radial groove section disposed inside the lower cover plate 3 and a collection cavity section disposed near the axial region of the lower cover plate 3.

[0036] In this structure, the return channel 13 is constructed as two functionally complementary sections: a radial groove section located inside the lower cover plate 3 and a collection section located near the axis of the lower cover plate 3. The radial groove section extends radially along the lower cover plate 3, with one end connected to the outlet of the guide cavity 11 and the other end extending radially inward to the region near the axis of the lower cover plate 3. The fluid drawn into the guide cavity 11 naturally tends to move outward under the centrifugal force generated by the impeller rotation, while the return channel 13 needs to guide this fluid to overcome the centrifugal force and flow backward towards the axis. The radial groove section undertakes the main guiding task, and its cross-sectional area can be set to monotonically increase along the direction towards the axis, thereby reducing the flow resistance between the outlet of the guide cavity 11 and the collection section, compensating for the outward driving effect of the rotating centrifugal force on the liquid in the cavity, and ensuring that the fluid can flow smoothly inward. Through this structural design, the return channel 13 realizes the orderly recovery and reuse of the pumped fluid, allowing the low-energy fluid that originally accumulated in the rear separation zone of the back pressure surface 10 to flow back into the mainstream and participate in the impeller's work cycle, thereby improving the overall energy utilization rate while suppressing separation.

[0037] In one embodiment, the profile of the frontal wall of the guide shell blade 8 is parallel and equidistant from the profile of the back pressure surface 10 within the distribution section of the throttling orifice array 12, so that a guide interlayer 14 with a gradually decreasing cross-sectional area along the flow direction is formed between the back pressure surface 10 and the frontal wall.

[0038] In this structure, the profile of the frontal wall of the guide shell blade 8 is parallel and equidistant from the profile of the back pressure surface 10 of the main blade 7 within the distribution section of the throttling orifice array 12. The distance between the frontal wall of the guide shell blade 8 and the back pressure surface 10 of the main blade 7 remains constant along the fluid flow direction, thereby forming a guide interlayer 14 with a gradually decreasing cross-sectional area along the flow direction between the back pressure surface 10 and the frontal wall. The inlet of the guide interlayer 14 is located near the starting end of the throttling orifice array 12, and the outlet extends to the radial outlet 6 region.

[0039] This parallel and equidistant profile design has a clear hydrodynamic function. First, the tapering geometry of the flow-guiding interlayer 14 exerts a continuous acceleration effect on the fluid flowing through it, increasing the fluid's kinetic energy as it flows through this region, thus effectively resisting the flow separation tendency caused by the adverse pressure gradient. Even if some fluid shows a deceleration tendency in the near-wall region of the back pressure surface 10, the acceleration effect of the flow-guiding interlayer 14 can promote its re-attachment to the wall, maintaining flow stability. Second, the presence of the flow-guiding interlayer 14 ensures that the orifice array 12 is always in a stable flow field environment with well-defined geometric boundaries. Since the distance between the upstream wall and the back pressure surface 10 remains constant, the incoming flow conditions at all points of the orifice array 12 tend to be consistent, allowing each orifice to operate under similar pressure differential and flow velocity conditions, thereby ensuring the uniformity and predictability of the suction process.

[0040] The flow-guiding interlayer 14 and the orifice array 12 work synergistically. The flow-guiding interlayer 14 accelerates the fluid and suppresses separation, creating a stable low-energy fluid supply source for the orifice array 12. Meanwhile, the orifice array 12 removes the low-energy fluid accumulated near the inner wall of the flow-guiding interlayer 14 through suction, preventing it from developing into a large-scale separation vortex. These two elements complement each other, enabling the flow-guiding shell blades 8 to achieve efficient suppression of flow separation in the rear part of the back pressure surface 10 of the main blades 7 with relatively low suction flow rate.

[0041] In one embodiment, the spanwise height of the guide housing blade 8 is less than that of the main blade 7, and there are gaps of 0.3 to 1.0 mm between the blade tip and the blade root of the guide housing blade 8 and the upper cover plate 1 and the lower cover plate 3, respectively. These gaps are used to suppress excessive leakage on one side due to impeller eccentricity.

[0042] In this structure, the spanwise height of the guide vane 8 is set to be less than that of the main vane 7, so that a gap of 0.3 to 1.0 mm is formed between the tip of the guide vane 8 and the upper cover plate 1 and between the root of the vane 8 and the lower cover plate 3.

[0043] When the impeller becomes radially eccentric during operation, the flow channel width between the main blade 7 and the guide shell blade 8 will be unevenly distributed in the circumferential direction. Without this gap, if the sealing surfaces between the guide shell blade 8 and the upper cover plate 1 and lower cover plate 3 come into contact or become excessively close, it will cause a sudden increase in suction flow on one side and insufficient suction on the other, disrupting the original uniform suction effect of the orifice array 12, and even causing localized overheating or mechanical rubbing. However, by setting a gap of 0.3 to 1.0 mm, even if the impeller becomes eccentric to a certain extent, this gap can act as a fluid resistance balancing element, automatically adjusting the leakage flow at each circumferential position. This adaptive adjustment mechanism effectively suppresses excessive leakage on one side caused by impeller eccentricity, maintaining the stability and consistency of the suction performance of the orifice array 12.

[0044] Furthermore, this gap provides necessary clearance for the guide shell blades 8, preventing rigid contact between the blades and the cover plate due to thermal expansion or centrifugal deformation, thus improving the reliability and durability of the impeller operation. Therefore, this gap range, in conjunction with the spanwise height design of the guide shell blades 8, constitutes an indispensable engineering detail in the active suction system of this invention.

[0045] In one embodiment, the pressure surface 9-shaped line and the back pressure surface 10-shaped line of the main blade 7 are both composite curved surfaces smoothly spliced ​​from multiple arc segments, and the outlet placement angle 15 of the main blade 7 is 20° to 30°, and the wrap angle 16 of the main blade 7 is 30° to 50°.

[0046] In this structure, both the pressure surface 9 and back pressure surface 10 of the main blade 7 adopt a composite surface design composed of multiple smoothly joined arcs. This composite surface is not a simple combination of circular arcs, but rather a smooth spatial curve with gradually changing curvature formed by maintaining tangential continuity at the connection points of arc segments with different radii of curvature. The profile of the pressure surface 9 begins near the axial inlet 5, first receiving the incoming flow with a convex arc segment with a larger radius of curvature, and then smoothly transitioning to a concave arc segment with a smaller radius of curvature, ensuring that the fluid remains in close contact with the blade surface during acceleration without detaching. The profile of the back pressure surface 10 coordinates with this design, using a concave arc segment on the inlet side to adapt to the fluid's direction of change, and a convex arc segment on the outlet side to guide the fluid to flow out smoothly, thereby establishing a balanced pressure distribution throughout the flow channel.

[0047] Meanwhile, the outlet angle 15 of the main blade 7 is limited to between 20° and 30°. The outlet angle 15 refers to the angle between the tangent of the tail profile of the main blade 7 at the radial outlet 6 and the circumferential tangent at that point. The size of this angle directly affects the velocity and direction of the fluid leaving the impeller: when the outlet angle 15 is close to 20°, the radial component of the fluid is larger, which is beneficial for obtaining a higher head; when it is close to 30°, the circumferential component increases, which is beneficial for improving flow rate and efficiency. Controlling the outlet angle 15 within this range achieves a good balance between head, efficiency, and flow stability, allowing the fluid to enter the volute or guide vanes with a suitable velocity vector, reducing impact losses.

[0048] The wrap angle 16 of the main blade 7 is limited to between 30° and 50°. The wrap angle 16 refers to the central angle corresponding to the projection of the main blade 7 profile onto a plane perpendicular to the impeller axis. It determines the curvature of the blade from the inlet to the outlet and the flow channel length. If the wrap angle 16 is too small (less than 30°), the blade will be too straight, preventing the fluid from achieving sufficient energy conversion, thus affecting both head and efficiency. If the wrap angle 16 is too large (greater than 50°), the flow channel will be too narrow and long, increasing frictional losses and easily causing flow separation in the rear part of the back pressure surface 10. Controlling the wrap angle 16 within the range of 30° to 50° ensures that the main blade 7 has a moderate curvature and flow channel length, guaranteeing sufficient work by the fluid while maintaining low flow resistance.

[0049] The aforementioned composite curved surface profile, outlet placement angle 15, and wrap angle 16 work together to create the superior hydrodynamic performance of the main blade 7. The composite curved surface profile ensures smooth fluid adhesion to the blade surface, the outlet placement angle 15 optimizes the fluid outlet condition, and the wrap angle 16 balances work capacity and flow losses. This combined design lays the foundation for the efficient and stable operation of the main blade 7, and also creates favorable inflow conditions for the active suction system of the guide vane blade 8, allowing the guide vane blade 8 to focus more on dealing with the local separation problem in the rear part of the back pressure surface 10, thereby achieving further improvement in overall performance.

[0050] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0051] The specific embodiments described herein are merely illustrative of the spirit of the invention. Those skilled in the art to which this invention pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them, without departing from the spirit of the invention or exceeding the scope defined by the appended claims.

Claims

1. A water pump impeller with good flow guiding properties, characterized in that: Includes an upper cover plate (1), and the upper cover plate (1) is provided with a lower cover plate (3) opposite to the pump shaft (2) of the water pump. The upper cover plate (1) and the lower cover plate (3) together define a fluid chamber (4). The lower cover plate (3) has an axial inlet (5) at its center that communicates with the fluid chamber (4), and the outer periphery of the fluid chamber (4) forms a radial outlet (6). Multiple main blades (7) and multiple guide shell blades (8) are arranged circumferentially between the upper cover plate (1) and the lower cover plate (3). A flow channel is formed between adjacent main blades (7) extending from the axial inlet (5) to the radial outlet (6). The main blades (7) have a pressure surface (9) and a back pressure surface (10). The flow guide shell blade (8) is located between two adjacent main blades (7). The flow guide shell blade (8) is constructed as a hollow shell integrally formed with the upper cover plate (1), and a flow guide cavity (11) is formed inside it. The flow guide shell blade (8) has a throttling hole array (12) on the front wall facing the back pressure surface (10), and a return channel (13) communicating with the flow guide inner cavity (11) is opened on the side of the flow guide shell blade (8) facing the lower cover plate (3). The outlet of the return channel (13) is in fluid communication with the axial inlet (5). The throttling orifice array (12) is used to draw low-energy fluid accumulated in the rear separation zone of the back pressure surface (10) of the main blade (7). The drawn fluid flows back into the main stream after passing through the guide cavity (11) and the return channel (13).

2. A water pump impeller with good flow guiding properties according to claim 1, characterized in that: In the projection plane perpendicular to the impeller axis, the outer edge radius of the impeller is defined as R1, and the radial distance from the starting position of the head of the guide shell blade (8) to the axis is R2. The ratio of R2 to the outer edge radius R1 of the impeller is 0.62 to 0.

78.

3. A water pump impeller with good flow guiding properties according to claim 1, characterized in that: The orifice array (12) has a non-uniformly distributed orifice area ratio along the radial direction. In the radial middle section region of the guide shell blade (8), the orifice area accounts for 3% to 8% of the area of ​​the frontal wall in that region. The radial middle section region is defined as the range between 0.65 times the outer radius of the impeller and 0.85 times the outer radius of the impeller. In the radial head region of the guide shell blade (8), the orifice area accounts for less than or equal to 2% of the area of ​​the frontal wall in that region. The radial head region is defined as the range between the starting position of the head of the guide shell blade (8) and 0.65 times the outer radius of the impeller.

4. A water pump impeller with good flow guiding properties according to claim 1, characterized in that: The diameter of a single throttling orifice in the orifice array (12) is 0.5 to 2.0 mm.

5. A water pump impeller with good flow guiding properties according to claim 1, characterized in that: The return channel (13) includes a radial groove section inside the lower cover plate (3) and a collection cavity section near the axis region of the lower cover plate (3).

6. A water pump impeller with good flow guiding properties according to claim 1, characterized in that: The profile of the frontal wall of the guide shell blade (8) is parallel and equidistant from the profile of the back pressure surface (10) within the distribution section of the throttling hole array (12), so that a guide interlayer (14) with a gradually decreasing cross-sectional area along the flow direction is formed between the back pressure surface (10) and the frontal wall.

7. A water pump impeller with good flow guiding properties according to claim 1, characterized in that: The spanwise height of the guide shell blade (8) is less than that of the main blade (7). There is a gap of 0.3 to 1.0 mm between the tip and root of the guide shell blade (8) and the upper cover plate (1) and the lower cover plate (3), respectively. This gap is used to suppress excessive leakage on one side caused by impeller eccentricity.

8. A water pump impeller with good flow guiding properties according to claim 1, characterized in that: The pressure surface (9) profile and back pressure surface (10) profile of the main blade (7) are both composite curved surfaces smoothly spliced ​​from multiple arcs, and the outlet placement angle (15) of the main blade (7) is 20° to 30°, and the wrap angle (16) of the main blade (7) is 30° to 50°.

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