Semi-open centrifugal pump impeller and its optimization design

Abstract

A process for optimizing the design of a semi-open centrifugal pump impeller involves the steps of, reducing the number of long blades and adding a medium length splitter blade and a short length splitter blade having varying circumferential distances between any two optimized long blades. Each medium length and short length splitter blade have the same outlet position, profile and thickness as the optimized long blade; however, the medium length and short length splitter blades have different inlet positions relative to the optimized long blade. The long blade, medium length splitter blade and short length splitter blade are arranged in circumferential sequence along the direction of rotation of the impeller. This optimization improves various problems arising from the original semi-open centrifugal pumps, including low efficiency, significant loss at the inlet, inlet cavitation, separation of boundary layers at the blade inlets, narrow lift range of the dead point and excessive noise.

Claims

1. A method of optimizing a design of a semi-open centrifugal pump impeller rotatable in a direction of rotation and having a predetermined number of long blades fitted on the impeller, each long blade having a first radial length with a first blade angle for an outlet side of a pressure surface of the long blades and a second blade angle for an outlet side on a suction surface of the long blades; a circumferential portion of said long blades on an inlet side of the long blades having a first thickness dimension; a circumferential portion of said long blades on an outlet side of the long blades having a second thickness dimension, comprising the steps of: reducing the predetermined number of long blades to a lower number of optimized long blades to optimize performance of said pump impeller; adding medium length and short length splitter blades having varying circumferential positioning between adjacent optimized long blades, each said medium length splitter blades having a second radial length shorter than said first radial length of said long blade, each said short length splitter blades having a third radial length shorter than said second radial length of said medium length splitter blades, each of said medium length and short length splitter blades having identical outlet positions, profile and thickness dimension as the optimized long blades, the medium length and short length splitter blades having different inlet positions than the optimized long blades; and arranging said lower optimized number of long blades, said medium length splitter blades and said short length splitter blades in a circumferential sequence along a direction of rotation of said impeller, with one of said medium length splitter blades and one of said short length splitter blades being positioned between sequential said optimized long blades.

2. The method of claim 1 wherein the blade angle for the outlet side on the pressure surface of the long blades before the optimization is set as α.sub.Z1 the blade angle for the outlet side on the suction surface of the long blades before the optimization is set as α.sub.b1, a thickness of the circumferential portion of said long blades on the inlet side of the long blades before the optimization is set as d.sub.j1, a thickness of the circumferential portion of said long blades on the outlet of the long blades before the optimization is set as d.sub.c1.

3. The method of claim 2, wherein, the above-mentioned optimized long blades as well as the medium and short length splitter blades have identical epiphyseal lines as the long blades before optimization.

4. The method of claim 1, wherein the blade angle for the outlet side on a front end of each of said optimized long blades is defined as α.sub.Z2=K.sub.2α.sub.Z1, where a represents the blade angle of the long blades before optimization and K.sub.2 represents the correction coefficient and K.sub.2=1˜1.2; the blade angle for the outlet side on the suction surface of optimized long blades is defined as α.sub.b2=K.sub.3α.sub.b1, where K.sub.3 represents the correction coefficient and K.sub.3=0.8˜1.

5. The method of claim 1, wherein, the thickness of the circumferential portion of said long blades on the inlet side of optimized long blades is d.sub.j2=K.sub.4d.sub.j1, where d.sub.j1 represents a thickness of said long blades at respective blade inlets and K.sub.4 represents the correction coefficient and K.sub.4=0.5˜0.8; a thickness of the circumferential portion of said long blades on the inlet side of optimized long blades (2) is, d.sub.c2=K.sub.5d.sub.c1 where d.sub.c1 represents the thickness of said long blades before optimization and K.sub.5 represents the correction coefficient and K.sub.5=1.2˜2.

6. The method of claim 1, wherein, the number of optimized long blades Z.sub.2=K.sub.1Z.sub.1, is calculated and then rounded, where Z.sub.1 represents the number of long blades before optimization and K.sub.1 denotes the correction coefficient and K.sub.1=0.4˜0.6; the number of medium length splitter blades is Z.sub.3, the number of short splitter blades is Z.sub.4 and identical to that of the long blades, Z.sub.2; the diameter of inlet side on the medium length splitter blades (3) is $d_2=\frac{3d_4+2d_1}{3},$ a diameter of an inlet side on the short splitter blades (4) is $d_3=\frac{2d_4+3d_1}{3},$ where d.sub.4 represents an outer diameter of the impeller; d.sub.1 denotes a diameter of an inlet side on the optimized long blades; a dip angle (β.sub.2) of the inlet side on the medium-length splitter blades, a dip angle (β.sub.3) of inlet side on the short splitter blades and a dip angle (β.sub.1) of inlet side on the optimized long blades shall conform to the following relationship, which is β.sub.1=β.sub.2=β.sub.3.

7. The method of claim 1, wherein, a circumferential spacing angle (θ.sub.2) of the medium-length splitter blades and a circumferential spacing angle (θ.sub.1) of the short splitter blades shall conform to the following relationships: ${\theta }_1=\frac{60\left(\cos {\alpha }_{z2}+\cos {\alpha }_{b2}\right)}{Z_2\cos {\alpha }_{z2}};$ ${\theta }_2=\frac{120\left(\cos {\alpha }_{z2}+\cos {\alpha }_{b2}\right)}{Z_2\cos {\alpha }_{z2}};$ where Z.sub.2 denotes the number of optimized long blades; α.sub.Z2 represents the first blade angle of outlet side on the pressure surface of the optimized long blades; α.sub.b2 indicates the blade angle of outlet side on the suction surface of the optimized long blades.

8. The method of claim 1, wherein, a hub of an inlet side on the impeller is chamfered, a fillet radius (R.sub.1) at an inner diameter (d) of hub and a diameter (d.sub.5) of hub for an inlet side on the impeller shall conform to the relationship: R.sub.1=K.sub.6(d.sub.5−d), where K.sub.6 is the correction coefficient and K.sub.6=0.05˜0.25.

9. The method of claim 1, wherein, the pressure surface (9) of outlet side (8) on the blades is chamfered, its fillet radius (R.sub.2) and a thickness (d.sub.c2) of the circumferential portion of said long blades on the outlet side (8) of blades shall conform to the relationship: R.sub.2=K.sub.7d.sub.c2, where d.sub.c2 represents the thickness of the circumferential portion of said long blades and K.sub.7 is the correction coefficient and K.sub.7=0.2˜0.4.

10. The method of claim 1, wherein the medium and short length splitter blades are arranged with varying circumferential distances in between any two optimized long blades; the medium and short length splitter blades having the same outlet position, profile and thickness as the optimized long blades, the medium and short length splitter blades having different inlet position to the optimized long blades; the above-mentioned optimized long blades as well as the short and medium length splitter blades being arranged in circumferential sequence along the direction of rotation of said impeller.

11. An optimization design of the semi-open centrifugal pump impeller according to claim 1, wherein, the above-mentioned optimized long blades as well as the medium and short length splitter blades have identical epiphyseal line as the long blades before optimization.

12. An optimization design of the semi-open centrifugal pump impeller according to claim 1, wherein, the blade angle for the outlet side on the front end of the optimized long blades is α.sub.Z2=K.sub.2α.sub.Z1, where α.sub.Z1 represents the blade angle for the outlet side on the front end of the long blades before optimization and K.sub.2 represents the correction coefficient and K.sub.2=1˜1.2; the blade angle for the outlet side on the suction surface of the optimized long blades being α.sub.b2=K.sub.3α.sub.b1, where α.sub.b1 represents the blade angle for the outlet side of the long blades on the suction surface before optimization and K.sub.3 represents the correction coefficient and K.sub.3=0.8˜1.

13. An optimization design of the semi-open centrifugal pump impeller according to claim 1, wherein, the thickness of the circumferential portion of said long blades on an inlet side of the optimized long blades (2) is d.sub.j2=K.sub.4d.sub.j1, where d.sub.j1 represents the thickness of the circumferential portion of said long blades on the inlet side before optimization and K.sub.4 represents the correction coefficient and K.sub.4=0.5˜0.8; a thickness of the circumferential portion of said long blades on the inlet side of the optimized long blades (2) is d.sub.c2=K.sub.5d.sub.c1, where d.sub.c1 represents the thickness of the circumferential portion of said long blades before optimization and K.sub.5 represents the correction coefficient and K.sub.5=1.2˜2.

14. An optimization design of the semi-open centrifugal pump impeller according to claim 1, wherein, the number of optimized long blades Z.sub.2=K.sub.1Z.sub.1, which is calculated and then rounded, where Z.sub.1 represents the number of long blades before optimization and K.sub.1 denotes the correction coefficient and K.sub.1=0.4˜0.6; the number of medium length splitter blades being Z.sub.3, the number of short splitter blades being Z.sub.4 and identical to that of long blades, Z.sub.2; a diameter of an inlet side on the medium length splitter blades is $d_2=\frac{3d_4+2d_1}{3},$ a diameter of an inlet side on the short splitter blades being $d_3=\frac{2d_4+3d_1}{3},$ where d.sub.4 represents a outer diameter of the impeller; d.sub.1 denotes a diameter of an inlet side on the optimized long blades; a dip angle (β.sub.2) of an inlet side on the medium-length splitter blades, a dip angle (β.sub.3) of an inlet side on the short splitter blades and a dip angle (β.sub.1) of an inlet side on the optimized long blades shall conform to the following relationship, which is β.sub.1=β.sub.2=β.sub.3.

15. An optimization design of the semi-open centrifugal pump impeller according to claim 1, wherein, a circumferential spacing angle (θ.sub.3) of the medium-length splitter blades and that (θ.sub.1) of the short splitter blades shall conform to the following relationships: ${\theta }_1=\frac{60\left(\cos {\alpha }_{z2}+\cos {\alpha }_{b2}\right)}{Z_2\cos {\alpha }_{z2}};\mathrm{and}$ ${\theta }_2=\frac{120\left(\cos {\alpha }_{z2}+\cos {\alpha }_{b2}\right)}{Z_2\cos {\alpha }_{z2}};$ where Z.sub.2 denotes the number of optimized long blades; α.sub.Z2 represents a blade angle of an outlet side on a pressure surface of the optimized long blades; α.sub.b2 indicates a blade angle of an outlet side on the suction surface of the optimized long blades.

16. An optimization design of the semi-open centrifugal pump impeller according to claim 1, wherein, a hub of an inlet side on the impeller is chamfered, a fillet radius (R.sub.1), an inner diameter (d) of hub and a diameter (d.sub.5) of a hub for an inlet side on the impeller shall conform to the relationship: R.sub.1=K.sub.6(d.sub.5−d), where K.sub.6 is the correction coefficient and K.sub.6=0.05˜0.25.

17. An optimization design of the semi-open centrifugal pump impeller according to claim 1, wherein, a pressure surface of an outlet side on the long blades is chamfered, its fillet radius (R.sub.2) and a thickness (d.sub.c2) of a circumferential portion of said long blades on an outlet side (8) of the long blades shall conform to the relationship: R.sub.2=K.sub.7d.sub.c2, where K.sub.7 is the correction coefficient and K.sub.7=0.2˜0.4.

18. An optimization design of the semi-open centrifugal pump impeller according to claim 1, wherein the medium and short length splitter blades are arranged with varying circumferential distances in between any two optimized long blades; the medium and short length splitter blades have the same outlet position, profile and thickness as the optimized long blades, the medium and short length splitter blades as mentioned above have different inlet position to the optimized long blades; the above-mentioned optimized long blades as well as the short and medium length splitter blades are arranged in circumferential sequence along the direction of the spinning of the impeller.

19. An optimization design of a semi-open centrifugal pump impeller having a number of long blades fitted on the impeller before optimization, each said long blade having a first radial length, a blade angle for an outlet side on a pressure surface of the long blades before optimization is set as α.sub.Z1, a blade angle for an outlet side on a suction surface of the long blades before the optimization is set as α.sub.b1, a thickness dimension of a circumferential portion of said long blades on inlet side of the long blades before the optimization is set as d.sub.j1, a thickness dimension of a circumferential portion of said long blades on the outlet of the long blades before the optimization is set as d.sub.c1, comprising the steps of: the number of long blades after optimization is lower than before optimization; medium length and short length splitter blades are added and arranged with varying circumferential distances in between any two optimized long blades; the medium length splitter blades having a second radial length shorter than said first radial length and said short length splitter blades having a third radial length shorter than said second radial length, the medium and short length splitter blades having the same outlet position, profile and thickness as the optimized long blades, and the medium and short length splitter blades having different inlet position to the optimized long blades; the above-mentioned optimized long blades as well as the short and medium length splitter blades are arranged in circumferential sequence along a direction of rotation of said impeller.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is the vertical plane of the impeller shaft prior to the optimization;

(2) FIG. 2 is the vertical plane of the impeller shaft following the optimization and shows the enlarged image of the pressure surface of outlet blades;

(3) FIG. 2B is an enlargement corresponding to circle B in FIG. 2;

(4) FIG. 3 is the vertical plane of the axial surface following the optimization and shows the enlarged image of the hub at the inlet side;

(5) FIG. 3A is an enlargement corresponding to circle A in FIG. 3; and

(6) FIG. 4 presents the performance comparison before and after the optimization.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

(7) The specific implementation processes of the present invention are further illustrated below in conjunction with the accompanying drawings and specific embodiments. Based on the attached schematic diagrams and the real case, the invention will be further elaborated, to which the protection of it is not limited though. In the drawings: 1—epiphyseal line; 2—optimized long blades; 3—medium length splitter blades; 4—short splitter blades; 8—outlet side; 9—pressure surface of blades; 10—suction surface of blades; 11—long impeller blades before optimization.

(8) As shown in FIG. 1, the object of optimization is A1-typed semi-open centrifugal pump impeller, the rated rotating speed of which is 2900 times per minute. The relevant parameters of the long blades before optimization are as follows. The number of blades Z.sub.1=6, the outer diameter of blades d.sub.4=200 mm, the diameter of blades at the inlet side d.sub.1=85.2 mm, the dip angle of blades at the inlet side β.sub.1=130°. The blade angle (α.sub.Z1) of blade for outlet 8 at the pressure surface 9 of blade 2 is identical to that (α.sub.b1) for outlet side 8 at the suction surface 10 of blade 2 and α.sub.Z1=α.sub.b1=29°. The thickness of circumferential blades at blade inlets d.sub.j1=6.5 mm, the thickness of circumferential blades at blade outlets d.sub.c1=14.6 mm, the inner diameter of the hub d=23 mm, and the diameter of the hub at blade inlets d.sub.5=35 mm.

(9) As shown in FIGS. 2 and 3, the optimization is detailed as follows. The number of optimized long blades 2 is lower than that of long blades 11 before optimization. The medium length splitter blade 3 and short splitter blade 4 are arranged with varying circumferential distances in between any two optimized long blades as mentioned above. The medium length splitter blade 3 and short splitter blade 4 as mentioned above have the same outlet position, profile and thickness as the optimized long blade 2. The medium length splitter blade 3 and short splitter blade 4 as mentioned above have different inlet position to the optimized long blades. The above-mentioned optimized long blade 2 as well as the medium length splitter blade 3 and short splitter blade 4 are arranged in circumferential sequence along the direction of impeller spinning. The above-mentioned optimized long blade 2 as well as the medium length splitter blade 3 and short splitter blade 4 have the same epiphyseal line 1 as the long blade 11 before optimization.

(10) The blade angle for outlet 8 at the pressure surface 9 of the optimized blade 2 α.sub.Z2=K.sub.2α.sub.Z1, where K.sub.2 is the correction coefficient and K.sub.2=1˜1.2, that is, α.sub.Z2=33°. K.sub.2 is taken as 1.15.

(11) The blade angle for outlet side 8 at the suction face 10 of the optimized blade 2 α.sub.b2=K.sub.3α.sub.b1, where K.sub.3 is the correction coefficient and K.sub.3=0.8˜1, that is, α.sub.b2=26. K.sub.3 is taken as 0.9.

(12) The thickness of circumferential blades for inlet side on the optimized blade 2 d.sub.j2=K.sub.4d.sub.j1, where K.sub.4 is the correction coefficient and K.sub.4=0.5˜0.8, that is, d.sub.j2=3.9. K.sub.3 is taken as 0.6.

(13) The thickness of circumferential blades for outlet on the optimized blade 2 d.sub.c2=K.sub.5d.sub.c1, where K.sub.5 is the correction coefficient and K.sub.5=1.2˜2, that is, d.sub.c2=26.3. K.sub.5 is taken as 1.8.

(14) For the optimized blade 2, the number of blades Z.sub.2=K.sub.1Z.sub.1, which is calculated and rounded. In this equation, K.sub.1 is the correction coefficient and K.sub.1=0.4˜0.6, that is, Z.sub.2=3. K.sub.1 is taken as 0.5.

(15) The number (Z.sub.3) of blades for the medium-length splitter blade 3, the number (Z.sub.4) of blades for the short splitter blade 4 and the number (Z.sub.2) of blades for the long blade 2 are equal.

(16) The diameter of inlet side on the medium-length splitter blade

(17) $3d_2=\frac{3d_4+2d_1}{3}=123.5.$

(18) The diameter of inlet side on the short splitter blade

(19) $4d_3=\frac{2d_4+3d_1}{3}=161.7,$
where, d.sub.4 represents the outer diameter of the impeller and d.sub.1 denotes the diameter of inlet side on the optimized long blade 2.

(20) The dip angle (β.sub.2) of inlet side on the medium-length splitter blade 3, the dip angle (β.sub.3) of inlet side on the short splitter blade 4 and the dip angle (β.sub.1) of inlet side on the optimized long blade 2 shall conform to the following relationship, which is β.sub.1=β.sub.2=β.sub.3=130°.

(21) The circumferential spacing angle (θ.sub.3) of the optimized blade 2 and the number (Z.sub.2) of impeller blades shall conform to the following relationship, which is

(22) ${\theta }_3=\frac{360}{Z_2}=120.$

(23) The circumferential spacing angle (θ.sub.2) of the medium-length splitter blade 3 and that (θ.sub.1) of the short splitter blade 4 shall conform to the following relationships.

(24) ${\theta }_1=\frac{60\left(\cos {\alpha }_{z2}+\cos {\alpha }_{b2}\right)}{Z_2\cos {\alpha }_{z2}}=41.6°;$${\theta }_2=\frac{120\left(\cos {\alpha }_{z2}+\cos {\alpha }_{b2}\right)}{Z_2\cos {\alpha }_{z2}}=83.2°;$
where Z.sub.2 denotes the number of optimized long blades. α.sub.Z2 represents the blade angle of outlet side 8 on the pressure surface 9 of the optimized long blade 2, and α.sub.b2 indicates the blade angle of outlet side 8 on the suction surface 10 of the optimized long blade 2.

(25) The hub A of inlet on the impeller is chamfered. The fillet radius (R.sub.1), the inner diameter (d) of hub and the diameter (d.sub.5) of hub for the inlet side on the impeller shall conform to the relationship R.sub.1=K.sub.6 (d.sub.5−d), where K.sub.6 is the correction coefficient and K.sub.6=0.05˜0.25, that is, R.sub.1=K.sub.6(d.sub.5−d)=1.2. K.sub.6 is taken as 0.1.

(26) The front end B of outlet on the blades is chamfered. Its fillet radius (R.sub.2) and the thickness (d.sub.c2) of circumferential blades on the outlet side of blades shall conform to the relationship R.sub.2=K.sub.7d.sub.c2, where K.sub.7 is the correction coefficient and K.sub.7=0.2˜0.4, that is, R.sub.2=K.sub.7d.sub.c2=7.9. K.sub.7 is taken as 0.3.

(27) FIG. 4 presents a comparison of pump performance before and after the optimization, from which it can be seen clearly that such an optimization improves pump efficiency and increase the lift range to some degree, especially that of the dead point. The maximum lift is increased by 13.2%, the maximum flow is improved by 14.3%, and the maximum efficiency is enhanced by 3.8%, which indicates that the hydraulic performance of the semi-open centrifugal pump is genuinely optimized.

(28) The semi-open centrifugal pump impeller consists of the optimized long blade 2 along with the medium-length splitter blade 3 and the short splitter blade 4. The medium length splitter blade 3 and short splitter blade 4 are arranged with varying circumferential distances in between any two optimized long blades as mentioned above. The medium length splitter blade 3 and short splitter blade 4 as mentioned above have the same outlet position, profile and thickness as the optimized long blade 2. The medium length splitter blade 3 and short splitter blade 4 as mentioned above have different inlet position to the optimized long blades. The above-mentioned optimized long blade 2 as well as the medium length splitter blade 3 and short splitter blade 4 are arranged in circumferential sequence along the direction of impeller spinning.

(29) Despite the above-mentioned real case being preferentially selected for the invention, it is not restricted to that. As long as there is no deviation from the essence of the invention, the technical personnel in this field are capable of making any notable improvement, substitution or modification, all of which fall within the category of protection by the invention.

(30) According to the design described in detail above, the number of long blades is changed and the medium and short length blades are added to improve in-channel circulation and reduce the loss of front cover leak, which is effective in enhancing the lift range of the dead point for pump and its efficiency and reducing cavitation.

(31) According to this optimization design, the hub of inlet side on the impeller is optimized by chamfering. When there is fluid passing through the hub of inlet side on the impeller, the separation of boundary layers occurs and vortex is induced. When the pressure is low, inlet cavitation could occur, which results in loss and channel blockage. To address this problem, our invention proposes chamfering of the hub of inlet side on the impeller to form a transition surface, which could reduce the loss when fluid passes through. Meanwhile, cavitation can be reduced significantly, which is conducive to reducing impact loss at the inlet and channel resistance.

(32) According to the design described above, the thickness of blades on the inlet side and outlet side of the impeller is optimized, that is, the inlet blades are reduced in thickness, the outlet blades are increased in thickness, and the pressure surface of impeller outlet is chamfered. In doing so, the flow area is effectively increase at the inlet side, the pressure difference is reduced at the suction surface of the outlet blades, as well as vortex and cavitation are reduced for the impeller outlet.

(33) According to the design adopted in the invention, a comparison is performed of the semi-open centrifugal pump before and after optimization. It is clearly seen that such an optimization improves pump efficiency and increases the lift range to some extent, especially that of the dead point. The maximum lift is increased by 13.2%, the maximum flow is improved by 14.3%, and the maximum efficiency is enhanced by 3.8%, which indicates that the hydraulic performance of the semi-open centrifugal pump is genuinely optimized.

(34) Finally, it should be noted, the above embodiments are merely illustrative of the technical solution of the present invention rather than limiting. Although the present invention is illustrated in detail with reference to the preferred embodiments, it should be understood by those of ordinary skill in the art, modifications or equivalent replacements can be made to the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention, which also fall within the scope of claims of the present invention.