A Design Method for a Cavitation-Resistant Centrifugal Pump Impeller

Abstract

The present invention discloses a design method for an anti-cavitation centrifugal pump impeller. By designing the working surfaces of the long blades and short blades and the backs of the long blades and short blades as positively curved twisted concave surfaces, the flow area of the intermediate flow surface is increased, and the flow velocity is reduced to lower the required net positive suction head (NPSH) and improve the anti-cavitation ability of the impeller. When the impeller designed by this method is at the limit low pressure at the inlet, there is basically no bubble aggregation phenomenon, the improvement effect of the anti-cavitation performance is remarkable, and the efficiency is significantly improved under the small flow rate condition; within the entire range of the inlet pressure design requirements, the impeller has good anti-cavitation performance. The anti-cavitation performance of the impeller is improved without sacrificing the impeller efficiency, without changing its fixed external dimensions and interfaces, and only the blade profile needs to be locally modified on the basis of the existing impeller. Moreover, it is easy to promote and has high application value.

Description

Technical Field

[0001] The present invention belongs to the field of engine fuel centrifugal pumps, and particularly relates to an impeller of a centrifugal pump with low specific speed and cavitation resistance. Background Art

[0002] Due to the complex and variable load of aero-engines, when the engine fuel centrifugal pump operates under off-design conditions, complex flows such as separation, flow separation, and vortex cavitation often occur inside, resulting in cavitation damage. At the same time, the cumulative damage caused by cavitation will cause the low-pressure area inside the impeller to rapidly expand from the impeller inlet to the impeller outlet end, which will further promote the generation of cavitation bubbles and the expansion of the cavitation bubble volume inside the impeller, resulting in more serious inhibition of the energy conversion of the fuel pump, directly affecting the reliable operation and service life of the fuel supply system. In the face of the special requirements of high-performance fighter jets, how to ensure the hydraulic performance and operation reliability of the fuel pump has become an important topic in the field of centrifugal pump design. It is urgent to master the design methods for improving the efficiency and cavitation resistance of engine fuel centrifugal pumps.

[0003] There are many current design methods for improving the cavitation resistance of centrifugal pumps, such as: designing an inducer, designing long and short blades, using twisted blades, increasing the inlet area of the casing, etc.

[0004] Although the existing design methods for improving the cavitation resistance of impellers can achieve the purpose of improving cavitation resistance, they will reduce the efficiency of the centrifugal pump or require changing the solidified structure of the centrifugal pump. However, during the product development process of engine fuel centrifugal pumps, they are often restricted by the installation space, interface dimensions, and production cycle, resulting in a reduced feasibility of modifying its structure to enhance cavitation resistance. Summary of the Invention

[0005] In order to improve the cavitation resistance of the centrifugal pump impeller without sacrificing efficiency, without changing its solidified external dimensions and interfaces, and meeting the machining operability, the present invention proposes a design method for a cavitation-resistant centrifugal pump impeller.

[0006] In order to achieve the above task, the present invention adopts the following technical solutions:

[0007] A design method for a cavitation-resistant centrifugal pump impeller, by designing the working surfaces of long blades and short blades and the backs of long blades and short blades as concave surfaces with positive curvature twists, increasing the flow area of the middle flow surface, and reducing the flow velocity to reduce the required net positive suction head and improve the cavitation resistance of the impeller.

[0008] Furthermore, by designing the working surfaces of long blades and short blades and the backs of long blades and short blades as concave surfaces with positive curvature twists, and increasing the flow area of the middle flow surface, the specific design method is as follows:

[0009] According to the performance index parameters and structural forms, calculate the impeller parameters by referring to the design manual;

[0010] Determine the meridional projection diagram of the impeller according to the impeller parameters and the axial installation position of the impeller;

[0011] Conduct blade profile design according to the conformal transformation method of the grid, including determining the design parameters of long blades and short blades, as well as determining the profile characteristic parameters of long blades, and obtaining long blades according to the design parameters and profile characteristic parameters; obtain short blades by means of intercepting according to the designed long blades;

[0012] Conduct impeller geometric structure design according to the installation position.

[0013] Furthermore, the impeller parameters are calculated with reference to the design manual according to the performance index parameters and the structural form, wherein the impeller parameters include:

[0014] The equivalent diameter d0 of the impeller, the impeller inlet diameter D j , the impeller outer diameter D2, and the impeller outlet width b.

[0015] Furthermore, the determination of the meridional projection diagram of the impeller according to the impeller parameters and the axial installation position of the impeller includes:

[0016] The front cover streamline, the middle streamline, and the rear cover streamline; the front and rear cover streamlines are composed of an axial straight line segment, a radial straight line segment, and a curve segment located between the two straight line segments, and the straight line segment and the curve segment are smoothly transitioned.

[0017] Furthermore, the determination of the design parameters of long blades and short blades includes:

[0018] The long blade inlet diameter D L =K L *D j and the short blade inlet diameter D s =K S *D2, where K L is the long blade inlet diameter coefficient, and K S is the short blade inlet diameter coefficient;

[0019] Determine the long blade and short blade inlet position points P L , P S , where P L is the intersection point of the circle with a diameter of D L and the front cover streamline, and P S is the intersection point of the circle with a diameter of D s and the front cover streamline;

[0020] Among them, the number of long blades and short blades is equal, and they are arranged staggered and evenly around the impeller axis.

[0021] Furthermore, K L =1 to 1.05; KS = 0.55 to 0.67. The specific value can be determined by referring to the magnitude of the similarity discrimination number - specific speed. When the specific speed ≤ 60, K L and K S both take the small values of 1 and 0.55. When 60 ≤ specific speed ≤ 100, K L and K S take values by interpolation in (1.01 - 1.04) and (0.56 - 0.66). When the specific speed > 100, K L and K S both take the large values of 1.05 and 0.67.

[0022] Furthermore, the determination of the blade profile characteristic parameters of the long blades includes:

[0023] The number of blades Z, the inlet setting angle β of the long blade close to the front cover plate 5a and the inlet setting angle β of the long blade close to the rear cover plate 7a and the inlet setting angle β of the middle flow surface 6a and the wrap angle θ of the long blade, the outlet setting angle β of the long blade close to the front cover plate 5b and the outlet setting angle β of the middle flow surface 6b and the outlet setting angle β of the long blade close to the rear cover plate 7b . Define the difference coefficient K of the inlet setting angle of the long blade βa = β 6a / β 5a and the difference coefficient K of the outlet setting angle of the long blade βb = β 6b / β 5b ;

[0024] Among them, the values of each parameter are:

[0025] 12° ≤ β 5a ≤ 17°;

[0026] β 7a = β 5a + 5°;

[0027] 110° ≤ θ ≤ 155°;

[0028] The value of Z is: N long blades and N short blades, where the value of N is 2, 3, or 4.

[0029] 18° ≤ β 5b ≤ 25°;

[0030] β 7b = β 5b ;

[0031] β 6a = K βa * β 5a, where K βa = 0.53 to 0.83;

[0032] β 6b = K βb *β 5b , where K βb = 1.25 to 1.50.

[0033] Further, the value of θ can be determined by referring to the magnitude of the similarity discrimination number - specific speed. When the specific speed ≤ 60, it is taken within the range of 135° - 155° according to the interpolation method; when 60 ≤ specific speed ≤ 100, it is taken within the range of 115° - 134° according to the interpolation method; when the specific speed > 100, it is taken within the range of 110° - 114°;

[0034] For β 5b , when the flow - head or flow - boost performance curve requires to be smooth, β 5b is taken as 18° - 22°; when the flow - head performance curve requires to be steep, β 5b is taken as 23° - 25°;

[0035] For K βa , when the value of N is 2, the value range of K βa is 0.76 - 0.83; when the value of N is 3, the value range of K βa is 0.65 - 0.75; when the value of N is 4, the value range of K βa is 0.53 - 0.64.

[0036] Further, the short blades are obtained by intercepting according to the designed long blades, including:

[0037] According to the blade profile characteristic parameters of the long blades, the inlet diameter D L of the long blades, the inlet installation point P L of the long blades, and the outer diameter D2 of the impeller, determine the blade profile of the long blades and the inlet position line of the long blades in the meridional plane projection diagram; arrange 2N long blades evenly around the impeller axis, and take out every other N long blades from the 2N long blades for interception, and these intercepted blades are used as short blades.

[0038] Further, taking out every other N long blades from the 2N long blades for interception, the specific interception method is:

[0039] First, in the meridional plane projection diagram of the long blades, according to the inlet diameter D s of the short blades and the inlet installation position point P s of the short blades, obtain the inlet position line of the short blades; intercept the long blades by rotating the inlet position line of the short blades along the impeller axis to obtain the short blades.

[0040] Compared with the prior art, the present invention has the following technical features:

[0041] The impeller design method proposed by the present invention increases the flow area of the intermediate flow surface and reduces the flow velocity by designing the working surface and the back surface of the blade as a positively curved twisted concave surface, so as to reduce the required net positive suction head and improve the cavitation resistance of the impeller. When the impeller designed by this method is at the limit low pressure at the inlet, there is basically no bubble aggregation phenomenon, and the improvement effect of the cavitation resistance performance is significant. The efficiency is significantly improved under the small flow rate condition; within the entire inlet pressure design requirement range, the impeller has good cavitation resistance performance. The cavitation resistance of the impeller is improved without sacrificing the impeller efficiency. Without changing its solidified external dimensions and interfaces, only the blade profile needs to be locally modified on the basis of the existing impeller, and it is easy to promote, and has high application value. Brief Description of the Drawings

[0042] Figure 1 is a schematic diagram of the meridian plane structure of the impeller flow passage. Among them, (a) is a schematic diagram of the impeller flow passage, and (b) is a schematic diagram of the inlet position lines of the long blades and short blades;

[0043] Figure 2 (a) and (b) of are respectively a schematic diagram of the blade arrangement and a schematic diagram of a group of long and short blades;

[0044] Figure 3 (a) of is a schematic diagram of the inlet diameters of the long and short blades; (b) is a front view of the blade, (c) is a schematic diagram of the blade profile parameters of the long blade close to the front cover plate and the rear cover plate; (d) is a schematic diagram of the blade profile parameters of the intermediate flow surface;

[0045] Figure 4 is a schematic diagram of the impeller designed by this method;

[0046] Figure 5 is Figure 4 a sectional view of ;

[0047] Figure 6 (a) and (b) of are sectional schematic diagrams of the prior art impeller and the impeller of the present invention;

[0048] Figure 7 (a) and (b) of are comparative diagrams of the cavitation bubble distributions in the impeller flow passage of the prior art impeller and the impeller of the present invention under the cavitation state;

[0049] Figure 8 (a) and (b) of are comparative diagrams of the flow rate-boost value and the flow rate-efficiency curves of the prior art impeller and the impeller of the present invention at the rated speed.

[0050] Description of the reference numerals in the figure: 1 - Equivalent diameter of the impeller, 2 - Impeller inlet diameter, 3 - Impeller outer diameter, 4 - Impeller outlet width, 5 - Flow line of the front cover plate, 6 - Intermediate flow line, 7 - Flow line of the rear cover plate, 8 - Long blade, 9 - Short blade, 801 - Working surface of the long blade, 901 - Working surface of the short blade, 802 - Back surface of the long blade, 902 - Back surface of the short blade, 10 - Front cover plate of the impeller, 11 - Rear cover plate of the impeller. Detailed implementation mode

[0051] A large number of practices have proved that the conditions for cavitation in a centrifugal pump are determined by the pump itself and the suction device. The conditions determined by the pump itself are related to the flow situation inside the pump, that is, the required net positive suction head NPSHr of the pump, which is the net positive suction head required for the pump not to cavitate. The empirical calculation formula:

[0052]

[0053] Wherein:

[0054] V0 - Absolute velocity at the impeller inlet, m / s;

[0055] W0 - Relative velocity inside the impeller, m / s;

[0056] λ - Blade inlet circumferential flow pressure drop coefficient, usually taking 0.15 - 0.3, the smallest at the optimal operating point, and the λ value increases with the change of the incidence angle when deviating from the optimal operating condition.

[0057] The smaller the NPSHr, the smaller the pump pressure drop, the smaller the NPSHa required to be provided by the device, and the better the cavitation resistance of the pump.

[0058] What is related to the suction device refers to the device net positive suction head NPSHa, which is the surplus energy that the pump itself can provide exceeding the vaporization pressure head.

[0059]

[0060] Wherein:

[0061] Ps - Suction liquid surface pressure

[0062] V s - Velocity at the suction port, m / s;

[0063] P v - Vaporization pressure, Pa.

[0064] When the required net positive suction head NPSHr ≥ the device net positive suction head NPSHa, the centrifugal pump will not cavitate.

[0065] Structurally, the suction device refers to the part from the suction liquid level to the front of the pump inlet, and the part from the pump inlet to the pump outlet is the pump itself. Due to the flow around the blades, the lowest pressure point in the pump usually occurs slightly behind the back of the blade inlet. Here, the circumferential velocity is large, the relative velocity is relatively large, and the inlet pressure loss and the pressure drop caused by the flow around increase accordingly. In addition, at the inner wall of the flow path turn, due to the centrifugal force effect, the flow velocity is large and the pressure is low. When the pressure here is equal to the vaporization pressure of the fluid, cavitation begins to occur in the pump. Theoretically, if the pressure obtained by subtracting all the pressure drops from the suction liquid level of the pump to the lowest pressure point from the suction liquid level is less than the vaporization pressure, cavitation will occur in the pump. Control volumes are selected at the pump inlet, the impeller inlet, and from the blade inlet to the lowest pressure point respectively, and the basic cavitation equation of the pump can be obtained by using the Bernoulli equation:

[0066] NPSH a = NPSH r

[0067] To sum up, the smaller the NPSHr, the smaller the pressure drop of the pump, the smaller the NPSHa that the device must provide, and the better the cavitation resistance performance of the pump.

[0068] However, for the engine fuel centrifugal pump, the net positive suction head available (NPSHa) of the device is often affected by the pre-booster pump and the fuel control system pipeline, and the feasibility of increasing the NPSHa of the device is almost zero. In other words, as long as the required net positive suction head (NPSHr) can be reduced, the cavitation resistance performance of the fuel centrifugal pump can be improved. NPSHr is positively correlated with the absolute velocity V0 at the impeller inlet, the relative velocity W0 in the impeller, and the blade inlet flow-around pressure drop coefficient λ. And the blade inlet disturbance pressure drop coefficient λ is positively correlated with the deviation degree between the actual operating conditions and the designed conditions of the pump. Therefore, as long as the absolute velocity V0 and the relative velocity W0 at the impeller inlet or in the impeller are reduced, the purpose of reducing the required net positive suction head (NPSHr) can be achieved.

[0069] Therefore, an efficient cavitation-resistant centrifugal pump impeller design method is invented. By designing the working surfaces of the long blades and short blades and the backs of the long blades and short blades as positively curved twisted concave surfaces, the flow area of the middle flow surface is increased, and the flow velocity is reduced to lower the required net positive suction head and improve the cavitation resistance ability of the impeller. In addition, to ensure the hydraulic design efficiency of the impeller, the outlet installation angle of the middle flow surface of the impeller blades is slightly increased in the design method.

[0070] The centrifugal pump impeller designed by this method has a relatively high efficiency and strong cavitation resistance performance. Under the extreme inlet pressure conditions, there is no obvious bubble aggregation.

[0071] The steps of the impeller design method are as follows:

[0072] Step 1, according to the performance index parameters and structural form, refer to the design manual to calculate the impeller parameters including: the equivalent diameter of the impeller 1 (d0), the impeller inlet diameter 2 (D j)、Outer diameter of the impeller 3 (D2), outlet width of the impeller 4 (b).

[0073] Step 2: Determine the meridional projection diagram of the impeller according to the impeller parameters calculated in Step 1 and the axial installation position of the impeller. As Figure 1 shown, it includes:

[0074] Front shroud streamline 5, middle streamline 6, and rear shroud streamline 7; the front and rear shroud streamlines are composed of an axial straight line segment, a radial straight line segment, and a curved line segment located between the two straight line segments. The straight line segment and the curved line segment are smoothly transitioned to ensure that the cross-sectional area of the flow passage changes uniformly.

[0075] Step 3: Design the blade profile of the impeller.

[0076] Design the blade profile according to the conformal transformation method of the square grid. The profile should be smooth, unidirectional bending, and preferably slightly convex and straight. As Figure 2 shown.

[0077] The said blades include: multiple long blades 8, multiple short blades 9, working surface of the long blade 801, working surface of the short blade 901, back surface of the long blade 802, and back surface of the short blade 902. Among them, the long blades 8 and the short blades 9 are arranged alternately and evenly around the impeller axis.

[0078] Determine the design parameters of the long blades and the short blades:

[0079] As Figure 1 、 2 、3 shown, the inlet diameter of the long blade D L = K L * D j and the inlet diameter of the short blade D s = K S * D2 (where K L is the inlet diameter coefficient of the long blade, K S is the inlet diameter coefficient of the short blade (K L = 1 - 1.05; K S = 0.55 - 0.67. The specific values can be determined by referring to the similarity discriminant number - specific speed. When the specific speed ≤ 60, K L 、K S both take the small values 1, 0.55; when 60 ≤ specific speed ≤ 100, K L 、K S are taken according to the interpolation method in (1.01 - 1.04), (0.56 - 0.66); when the specific speed > 100, K L 、K S both take the large values 1.05, 0.67.

[0080] Determine the inlet position points P L 、PS , where P L is the intersection point of the circle with diameter D L and the streamline of the front cover plate, and P S is the intersection point of the circle with diameter D s and the streamline of the front cover plate.

[0081] Determine the blade profile characteristic parameters of the long blades:

[0082] The number of blades Z, the inlet setting angle β 5a of the long blade close to the front cover plate, the inlet setting angle β 7a of the long blade close to the rear cover plate, the inlet setting angle β 6a of the middle flow surface, the wrap angle θ of the long blade, the outlet setting angle β 5b of the long blade close to the front cover plate, the outlet setting angle β 6b of the middle flow surface, and the outlet setting angle β 7b of the long blade close to the rear cover plate. Define the difference coefficient K βa of the inlet setting angle of the long blade = β 6a / β 5a and the difference coefficient K βb of the outlet setting angle of the long blade = β 6b / β 5b .

[0083] The blade geometric parameters are as follows:

[0084] 12° ≤ β 5a ≤ 17°;

[0085] β 7a = β 5a + 5°;

[0086] 110° ≤ θ ≤ 155°; The value can be determined by referring to the magnitude of the similarity discrimination number - specific speed. When the specific speed ≤ 60, the value is taken in the range of 135° - 155° according to the interpolation method; when 60 ≤ specific speed ≤ 100, the value is taken in the range of 115° - 134° according to the interpolation method; when specific speed > 100, the value is taken in the range of 110° - 114°.

[0087] The value of Z is: N long blades, N short blades, where the value of N is 2, 3, or 4.

[0088] 18° ≤ β 5b ≤ 25°. When the flow rate - head or flow rate - boost performance curve requires to be stable, β 5b takes 18° - 22°; when the flow rate - head performance curve requires to be steep, β 5b takes 23° - 25°;

[0089] β 7b = β 5b ;

[0090] β 6a =K βa *β 5a , where K βa = 0.53 to 0.83; when N takes the value of 2, the value range of K βa is 0.76 - 0.83; when N takes the value of 3, the value range of K βa is 0.65 - 0.75; when N takes the value of 4, the value range of K βa is 0.53 - 0.64.

[0091] β 6b =K βb *β 5b , where K βb = 1.25 to 1.50.

[0092] According to the profile characteristic parameters of the above long blades and the inlet diameter D L of the long blades, the inlet installation point P L of the long blades, and the outer diameter D2 of the impeller, determine the profile of the long blades and the inlet position line of the long blades in the meridional plane projection diagram; arrange 2N long blades evenly around the impeller axis, and take out every other N long blades from the 2N long blades for cutting, and these cut blades are used as short blades;

[0093] The specific cutting method is as follows:

[0094] First, in the meridional plane projection diagram of the long blades, obtain the short blade inlet position line according to the short blade inlet diameter D s and the short blade inlet installation position point P s ; cut the long blades by rotating the short blade inlet position line along the impeller axis to obtain short blades.

[0095] Step 4, design the geometric structure of the impeller according to the installation position, including: the front cover plate 10 of the impeller, the rear cover plate 11 of the impeller, and the hub; thus, a complete impeller is obtained through the design of the front cover plate, the rear cover plate, the long blades, the short blades, and the hub.

[0096] Example:

[0097] In an embodiment of the present invention, the cavitation-resistant impeller designed according to the method of the present invention includes: a hub, a front cover plate, a rear cover plate, short blades, and long blades. The long and short blades are evenly arranged circumferentially along the hub. The radial position D L of the long blade inlet =K L *D2 (where D j is 93 mm, and K L is the short blade inlet position length coefficient K L = 0.99. The radial position Ds = K s * D2 (where R is 90 mm, K s is the length coefficient K of the short blade inlet position s = 0.67.

[0098] The relevant parameters of the impeller design in this embodiment are as follows:

[0099] β 5a = 14°;

[0100] β 6a = 19°;

[0101] θ = 132°;

[0102] Z = 4 long blades, 4 short blades;

[0103] β 5b = 20°;

[0104] β 7b = β 5b = 20°;

[0105] β 6a = K βa * β 6a = 0.78 * 14° = 11°;

[0106] β 6b = K βb * β 6b = 1.3 * 20° = 26°

[0107] Figure 6 Figures show the meridian plane structure diagrams of the impellers designed by the prior art and the method of the present invention, including the working surface (surface 801) of the long blade, the back surface (surface 802) of the long blade, the working surface (surface 901) of the short blade, and the back surface (surface 902) of the short blade. The working surface and the back surface of the impeller blade designed by the method of the present invention are positive-curvature twisted concave surfaces.

[0108] Figure 7 Figure shows the comparison diagram of the cavitation distribution of the impellers designed by the prior art and the method of the present invention under the design condition when the inlet pressure is the lowest. The area marked by the red line in the figure is the cavitation aggregation area. It can be seen that the impeller designed by the method of the present invention has basically no obvious cavitation aggregation, and the cavitation resistance performance is significantly improved.

[0109] Figure 8Under the design conditions, a comparison is made between the flow rate-boost value and the flow rate-efficiency curve of the impeller of the prior art and the impeller designed by the method of the present invention at the rated speed. As can be seen from the figure, at the rated condition, the simulation efficiencies of the impeller of the prior art and the impeller designed by the method of the present invention are both 78%. At the same speed, the boost value of the impeller designed by the method of the present invention is slightly increased at different flow rates. Under the small flow rate condition, the efficiency of the impeller designed by the method of the present invention is increased by about 1.5%. That is, the efficiency of the impeller designed by the method of the present invention is significantly improved under off-design conditions.

[0110] In summary, this embodiment sufficiently demonstrates that the impeller designed by the method of the present invention not only has good cavitation resistance but also can improve efficiency. When improving the design on the basis of the existing impeller, its solidified external dimensions and interfaces are not changed. Only slight modification of the blades is required, which is highly operable and easy to promote, and has high practical value.

[0111] The above embodiments are only used to illustrate the technical solutions of the present application, not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the various embodiments of the present application, and should all be included in the protection scope of the present application.

Claims

1. A design method for an anti-cavitation centrifugal pump impeller, characterized in that, By designing the working surfaces and the back surfaces of the long blades and short blades as concave surfaces with positive curvature twists, the flow area of the middle flow surface is increased, and the flow velocity is reduced to lower the required net positive suction head (NPSH) and improve the cavitation resistance of the impeller. Among them, by designing the working surfaces and the back surfaces of the long blades and short blades as concave surfaces with positive curvature twists to increase the flow area of the middle flow surface, the specific design method is as follows: According to the performance index parameters and structural forms, refer to the design manual to calculate the impeller parameters. Determine the meridional projection diagram of the impeller according to the impeller parameters and the axial installation position of the impeller. Conduct blade profile design according to the conformal transformation method of the grid, including determining the design parameters of the long blades and short blades, as well as determining the profile characteristic parameters of the long blades. Obtain the long blades according to the design parameters and profile characteristic parameters; obtain the short blades by the method of intercepting according to the designed long blades. Conduct impeller geometric structure design according to the installation position.

2. The design method of the anti-cavitation centrifugal pump impeller according to claim 1, characterized in that, The impeller parameters calculated by referring to the design manual according to the performance index parameters and structural forms, among which the impeller parameters include: Equivalent diameter d0 of impeller, impeller inlet diameter D j , impeller outer diameter D2, impeller outlet width b.

3. The design method of the anti-cavitation centrifugal pump impeller according to claim 1, wherein, The determination of the meridional projection diagram of the impeller according to the impeller parameters and the axial installation position of the impeller includes: The front shroud streamline, the middle streamline and the rear shroud streamline; the front and rear shroud streamlines are composed of a straight line segment in the axial direction, a straight line segment in the radial direction, and a curve segment between the two straight line segments, and the straight line segment and the curve segment are smoothly transitioned.

4. The anti-cavitation centrifugal pump impeller design method according to claim 1, characterized in that, The determination of the design parameters of the long blades and short blades includes: Inlet diameter D of the long blade L = K L * D j and the inlet diameter D of the short blade s = K S * D2, where K L is the inlet diameter coefficient of the long blade, and K S is the inlet diameter coefficient of the short blade; Determine the inlet position points P L , P S , where P L is the intersection point of the circle with diameter D L and the front cover streamline, and P S is the intersection point of the circle with diameter D s and the front cover streamline; Among them, the number of long blades and short blades is equal, and they are arranged staggeredly and evenly around the impeller axis.

5. The anti-cavitation centrifugal pump impeller design method according to claim 4, characterized in that, K L = 1 to 1.05; K S = 0.55 to 0.67, and the specific value can be determined by referring to the magnitude of the similarity discrimination number - specific speed. When the specific speed ≤ 60, K L and K S both take the smaller values of 1 and 0.55; when 60 ≤ specific speed ≤ 100, K L and K S take values in (1.01 - 1.04) and (0.56 - 0.66) according to the interpolation method; when the specific speed > 100, K L and K S both take the larger values of 1.05 and 0.

67.

6. The design method of the anti-cavitation centrifugal pump impeller according to claim 1, characterized in that, The determination of the profile characteristic parameters of the long blades includes: The number of blades Z, the inlet setting angle β of the long blade close to the front cover plate 5a 、the inlet setting angle β of the long blade close to the rear cover plate 7a 、the inlet setting angle β of the middle streamline 6a 、the wrap angle θ of the long blade, the outlet setting angle β of the long blade close to the front cover plate 5b 、the outlet setting angle β of the middle streamline 6b 、the outlet setting angle β of the long blade close to the rear cover plate 7b , define the difference coefficient K of the inlet setting angle of the long blade βa =β 6a / β 5a and the difference coefficient K of the outlet setting angle of the long blade βb =β 6b / β 5b ; Among them, the values of each parameter are: 12°≤β 5a ≤17°； β 7a ＝β 5a +5°； 110° ≤ θ ≤ 155°; The value of Z is: N long blades and N short blades, where the value of N is 2, 3, or 4. 18°≤β 5b ≤25°； β 7b ＝β 5b ； β 6a = K βa * β 5a , where K βa = 0.53 to 0.83; β 6b = K βb *β 5b , where K βb = 1.25 to 1.

50.

7. The design method of the anti-cavitation centrifugal pump impeller according to claim 6, characterized in that, The value of θ can be determined by referring to the magnitude of the similarity discriminant number - specific speed. When the specific speed ≤ 60, take values in the range of 135° - 155° according to the interpolation method; when 60 ≤ specific speed ≤ 100, take values in the range of 115° - 134° according to the interpolation method; when the specific speed > 100, take values in the range of 110° - 114°. For β 5b , when the flow rate - head or flow rate - boost performance curve is required to be smooth, β 5b is taken as 18° - 22°; when the flow rate - head performance curve is required to be steep, β 5b is taken as 23° - 25°; For K βa , when N takes the value of 2, the value range of K βa is 0.76 - 0.83; when N takes the value of 3, the value range of K βa is 0.65 - 0.75; when N takes the value of 4, the value range of K βa is 0.53 - 0.

64.

8. The design method of the anti-cavitation centrifugal pump impeller according to claim 1, characterized in that The method of obtaining the short blades by intercepting according to the designed long blades includes: According to the blade profile characteristic parameters of the long blades, the inlet diameter D of the long blades L , the inlet installation point P of the long blades L , and the outer diameter D2 of the impeller, determine the blade profile of the long blades and the inlet position line of the long blades in the meridional plane projection diagram; arrange 2N long blades evenly around the impeller axis, and take out every other N long blades from the 2N long blades for intercepting, and these intercepted blades are used as short blades.

9. The design method of the anti-cavitation centrifugal pump impeller according to claim 8, characterized in that, Take out every other N long blades from the 2N long blades for interception, and the specific interception method is: First, in the meridian plane projection diagram of the long blade, according to the inlet diameter D of the short blade s , and the inlet installation position point P of the short blade s to obtain the inlet position line of the short blade; the long blade is intercepted by rotating the inlet position line of the short blade along the impeller axis to obtain the short blade.

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