OPTIMAL DESIGN METHOD FOR JET-TYPE SELF-PRIMING CENTRIFUGAL PUMP

Abstract

An optimal design method for cutting at an impeller inlet provides a parameter selection and an optimal method for cutting lengths of a vertical side and a horizontal side, of the inlet, a diameter of the inclined position of the front and rear cover plates, the wall thickness δ1 of the front cover plate and the rear cover plate at an exit of the impeller after the inclination optimization, the number and wrap angle Φ of the long blades after optimization, an inlet diameter Dsi, arc length, axial offset degree, inclination angle, and the thickness of the splitter blades. The method is simple in implementation and can effectively improve the performance of the jet-type self-priming centrifugal pumps.

Claims

1: An optimized design method of jet self-priming centrifugal pump, it includes the optimization of the impeller blade to optimize the impeller blade is to set splitter blades between the long blades of the pump including the choice of the number of blades Z, the long blade inclusion after optimized Φ.sub.1, the inlet diameter of the splitter blades D.sub.si, the length of arc of split blades S.sub.2, the circumferential offset angle of splitter blades θ.sub.1 and the tilt angle of splitter blades a.sub.2; the relationship between the number of long blades on the optimized pump Z.sub.2 and the number of long blades in the original pump Z.sub.1 is as follows:
Z.sub.2=Z′*Z.sub.1  (5) where Z′ is the correction coefficient and Z′=0.6; optimized scroll of long blade Φ.sub.1 and the original model of scroll of long blade Φ, original pump long blade number Z.sub.1, optimized number of long blade on the pump Z.sub.2 are satisfied the following equation:
Φ.sub.1=Z.sub.1Φ/K.sub.ΦZ.sub.2  (6) where K.sub.Φ is the coefficient of the scroll of blade and K.sub.Φ=0.9426; the impeller inlet diameter of the splitter blades D.sub.si and the impeller outlet diameter D.sub.2 are satisfied the following equation:
D′=D.sub.si/D.sub.2  (7) where D′ is the correction coefficient and D′=(0.4˜0.8) the length of arc of split blades S.sub.2 and the length of arc of long blades S.sub.1 are satisfied the following equation:
K.sub.5=S.sub.2/S.sub.1  (8) where K.sub.5 is the correction coefficient and K.sub.5=(0.4˜0.8) the circumferential offset angle of splitter blades θ.sub.1 and the angle between two adjacent long blades θ are satisfied the following equation:
K.sub.6=θ.sub.1/θ  (9) where K.sub.6 is the correction coefficient and K.sub.6=(0.4˜0.6) the tilt angle of splitter blades a.sub.2 and the tilt angle of long blades a.sub.1 are satisfied the following equation:
K.sub.7=a.sub.2/a.sub.1  (10) and where K.sub.7 is the correction coefficient and K.sub.7=(0.5˜0.9).

2: The optimal design method of the jet self-priming centrifugal pump according to claim 1, wherein the inlet and outlet thickness of the splitter blades is consistent with that of the inlet and outlet thickness of the long blades.

3: The optimal design method of the jet self-priming centrifugal pump according to claim 1, further including cutting the impeller through the water side, wherein the vertical side cutting length a and the hub diameter of impeller d.sub.h are satisfied the following equation:
K.sub.1=a/d.sub.h  (1) where K.sub.1 is the correction coefficient and K.sub.1=(0.01˜0.05).

4: The optimal design method of the jet self-priming centrifugal pump according to claim 3, further including cutting the impeller through the water side, wherein, the horizontal side cutting length b and the hub diameter of impeller d.sub.h are satisfied the following equation:
K.sub.2=b/d.sub.h  (2) where K.sub.2 is the correction coefficient and K.sub.2=(0.02˜0.08)

5: The optimal design method of the jet self-priming centrifugal pump according to claim 1, wherein the impeller front shroud and the impeller back shroud were designed by tilting, it includes the design of the pitch position diameter D.sub.t, and the design of the pitch position diameter of the impeller front shroud and the impeller back shroud D.sub.t and the impeller outlet diameter D.sub.2 are satisfied the following equation:
K.sub.3=D.sub.t/D.sub.2  (3) where K.sub.3 is the correction coefficient and K.sub.3=(0.75˜0.95).

6: The optimal design method of the jet self-priming centrifugal pump according to claim 5, wherein the design of tilting includes the thickness of the impeller front shroud and the impeller back shroud, by this way, the optimized thickness of the impeller front shroud and the impeller back shroud δ.sub.1 and the original thickness of the impeller front shroud and the impeller back shroud δ.sub.2 are satisfied the following equation:
K.sub.4=δ.sub.1/δ.sub.2  (4) where K.sub.4 is the correction coefficient and K.sub.4=(0.6˜0.9).

7: The optimal design method of the jet self-priming centrifugal pump according to claim 1, wherein the result of the optimized number of long blade on the pump Z.sub.2 calculated by the correction coefficient Z′ and the number of long blades in the original pump Z.sub.1 is taken upward.

8: The optimal design method of the jet self-priming centrifugal pump according to claim 7, wherein the number of long blades on the optimized pump Z.sub.2 is equal to the number of splitter blades Z.sub.3.

Description

THE APPENDED DRAWINGS

[0035] FIG. 1 is a leaf wheel axle diagram of the invention and an enlarged view of the cutting at the inlet of the impeller.

[0036] FIG. 2 is the impeller plan of the original model

[0037] FIG. 3 is the impeller plan of the optimized model

[0038] FIG. 4 is the performance curve of the original model pump of the invention

[0039] FIG. 5 shows the performance curve of the optimized model pump

[0040] In the diagram, 1 means impeller inlet; 2 means impeller front shroud; 3 means impeller back shroud; 4 means splitter blades; 5 means long blade of the original model; 6 means long blade of the Optimized model.

IMPLEMENTATION OF THE EASE

[0041] Further details of the invention are given below in combination with attached drawings and specific implementation cases, but the scope of protection of the invention is not limited.

[0042] The invention relates to an optimized design method for a jet self-priming centrifugal pump which includes the optimization of the inlet 1, the impeller front shroud 2, the impeller hack shroud 3 and the blades.

[0043] when the liquid passes through the inlet side of the impeller, it will produce shock and then impact loss. In order to reduce the loss, the invention cuts the inlet side of the impeller to make it a buffer zone, so that the loss is much smaller when the liquid flows through this area, which can effectively reduce the impact loss of the inlet.

[0044] In order to make the inlet into the desired buffer zone, the cutting scheme adopted in the invention is that we select the appropriate cutting length on both sides (the vertical side and the horizontal side) of the inlet, the cutting length of the vertical sides called a, and the cutting length of the horizontal sides called b. And, the vertical side cutting length a and the horizontal side cutting length b is determined by the quantitative relation between a, b and the huh diameter the hub diameter of impeller d.sub.h, and they are satisfied the following equation:

K.sub.1=a/d.sub.h  (1)

[0045] d.sub.h is the hub diameter of impeller, mm

[0046] K.sub.1 means the correction coefficient and K.sub.1=(0.01˜0.05)

K.sub.2=b/d.sub.h  (2)

[0047] K.sub.2 means the correction coefficient and K.sub.2=(0.02˜0.08)

[0048] When the impeller rotates, there is friction loss between the outer surface of the front shroud and the hack shroud of the impeller and the liquid by the rapid rotating speed of the impeller. The loss is related to the diameter of the impeller, which is called disk friction loss. The invention optimizes the tilting design of the front shroud and the back shroud of the impeller so as to reduce the friction loss without changing the outside diameter of the impeller.

[0049] For setting the slant optimization parameters of the front shroud and the back shroud of the impeller, in the first, the invention determines the pitch position diameter D.sub.t, and then determines the optimized thickness of the impeller front shroud and the impeller back shroud δ.sub.1. When these two parameters are determined, the slant design of the front shroud and the back shroud cover plate is also determined.

[0050] For selecting the pitch position diameter D.sub.t, the invention establishes a quantitative relation with the impeller outlet diameter D.sub.2:

K.sub.3=D.sub.t/D.sub.2  (3)

[0051] K.sub.3 means the correction coefficient and K.sub.3=(0.75˜0.95)

[0052] Therefore, in the case that the impeller outlet diameter is known as D.sub.2, the pitch position diameter D.sub.t can be determined by the correction coefficient K.sub.3.

[0053] For the selection of the parameters of the optimized thickness of the impeller front shroud and the impeller back shroud δ.sub.1, the present invention establishes the δ.sub.1 and the original thickness of the original thickness of the impeller front shroud and the impeller back shroud δ.sub.2 to a quantitative relationship, and they are satisfied the following equation:

K.sub.4=δ.sub.1/δ.sub.2  (4)

[0054] K.sub.4 means the correction coefficient and K.sub.4=(0.6˜0.9)

[0055] Therefore, δ.sub.1 can be determined by the correction coefficient K.sub.4 when the δ.sub.2 is known.

[0056] What optimizes the impeller blades is that the splitter blades are arranged between the long blades of the original model the invention includes the choice of the number of blades Z, the scroll of long blade after optimized Φ.sub.1, the inlet diameter of the splitter blades D.sub.sl, the length of arc of splitter blades S.sub.2, the circumferential offset angle of splitter blades θ.sub.1, the tilt angle of splitter blades a.sub.2, and the optimized thickness of splitter blades at the inlet and outlet.

[0057] The design method of setting splitter blades between long blades is adopted to increase the head when the valve is completely closed and reduce the blockage at the inlet of the impeller. The methods adopted are as follows:

[0058] With the increase of blade number of impeller, the head increases obviously. However, too many blades will cause a large amount of hydraulic friction loss, which, on the contrary, reduces the efficiency of the pump. At the same time, the increase of the number of blades will lead to the increase of power, so it is particularly important to select an appropriate number of blades Z, In order to change the outside diameter and not overpower, a new method of adding splitter blades is proposed. A quantitative relationship was established between original pump long blade number Z.sub.1 and optimized number of long blade on the pump Z.sub.2, the relation is used to determine the optimized number of blades Z.sub.2. The expression is set up as follows:

Z.sub.2=Z′*Z.sub.1  (5)

[0059] Z′ means the correction coefficient and Z′=0.6;

[0060] The calculated result of Z.sub.2 is taken upward. Since the number of the splitter blade is equal to Z2, Z3 can be determined when Z2 is known.

[0061] In order to determine the optimized scroll of long blade Φ.sub.1, optimized scroll of long blade Φ.sub.1 and the original model of scroll of long blade Φ, original pump long blade number Z.sub.1, optimized number of long blade on the pump Z.sub.2 are adopted to establish a quantitative relationship:

Φ.sub.1=Z.sub.1Φ/K.sub.ΦZ.sub.2  (6)

[0062] K.sub.Φ means the coefficient of the scroll of blade and K.sub.Φ=0.9426;

[0063] So after the known Φ, Z.sub.1 and the Z2 calculated by Z′,Φ.sub.1 can be determined. The impeller inlet diameter of the splitter blades D.sub.si relates to the length of the splitter blades. Theoretically speaking, the longer the blade length is, the bigger the head, However, it can be seen from the study that the inlet will be blocked and the head will be reduced because of the too long splitter blades, which will also lead to a decrease in efficiency. But, if the splitter blade is too short it will not improve the structure of jet—wake at the outlet and improve the efficiency of the pump. Therefore, the quantitative relation between the impeller inlet diameter of the splitter blades D.sub.si and the impeller outlet diameter D.sub.2 is proposed to determine D.sub.si, they are satisfied the following equation:

D″=D.sub.si/D.sub.2  (7)

[0064] D′ means the correction coefficient and D′=(0.4˜0.8)

[0065] So you can determine D.sub.si by D″ when you know D.sub.2.

[0066] When choosing the parameters of the length of arc of split blades S.sub.2, a quantitative relationship between the length of arc of splitter blades S.sub.2 and the length of arc of long blades S.sub.1 is proposed. The relationship is as follows:

K.sub.5=S.sub.2/S.sub.1  (8)

[0067] K.sub.5 means the correction coefficient and K.sub.5=(0.4˜0.8)

[0068] So you can determine S.sub.2 by K.sub.5 when you know S.sub.1.

[0069] According to the flow slip theory in the centrifugal pump, the velocity distribution in the impeller passage is not uniform, so the splitter blade cannot be arranged in the middle of the flow passage, and it needs to be offset to the back of the long blade, which is conducive to improving the “jet-wake” structure at the outlet and improving the performance of the pump. The invention determines the circumferential position of the splitter blade by the ratio of the circumferential offset Angle of splitter blades θ.sub.1 to the angle between two adjacent long blades θ, and the relationship is as follows:

K.sub.6=θ.sub.1/θ  (9)

[0070] K.sub.6 means the correction coefficient and K.sub.4=(0.4˜0.6)

[0071] So you can determine θ.sub.1 by K.sub.6 when you know θ, and the circumferential offset position of the splitter blade can be determined.

[0072] The tilting position of the splitter blade can be determined by the tilt angle of splitter blades a.sub.2, so the quantization relationship is established by the tilt angle of splitter blades a.sub.2 and the tilt Angle of long blades a.sub.1:

K.sub.7=a.sub.2/a.sub.1  (10)

[0073] K.sub.7 means the correction coefficient and K.sub.7=(0.5˜0.9)

[0074] The invention designs the inlet and outlet thickness of the splitter blade. For the invention, the inlet and outlet thickness of the splitter blade is consistent with the long blade.

[0075] The implementation process of the invention is illustrated by taking low specific speed Jet self-priming centriftigal pump as an example. And the specific parameters of the pump are as follows: rated power is 800 w, specific speed is 32, head H is 121.39 ft, mass flow rate Q is 3700 L/H, speed n is 2775 r/m, efficiency η is 14.3%, impeller diameter D.sub.2 is 121 mm, width of blade outlet b.sub.2 is 4 mm, the original model of scroll of long blade Φ is 100°, blade inlet angle β.sub.1 is 19.3°, blade outlet angle β.sub.2 is 35°, the hub diameter the hub diameter of impeller d.sub.h is 19 mm, number of blades Z is 6, the original thickness of the impeller front shroud and the impeller back shroud δ.sub.2 is 2 mm.

[0076] As is shown in FIG. 1, the liquid passes through the inlet side of the impeller 1, it will produce shock the cutting scheme adopted in the invention is that we select the appropriate cutting length on both sides (the vertical side and the horizontal side) of the inlet to make it a buffer zone, and the cutting length of the vertical sides called a, and the cutting length of the horizontal sides called b. The diameter of the impeller hub d.sub.h is 19.2 mm, so you can figure out what a and b are by using (1) and (2). In this design, k.sub.1 and k.sub.2 were selected by CFD numerical calculation, after the numerical calculation, k.sub.1=0.02, k.sub.2=0.03, a=0.4 mm and b=0.6 mm.

[0077] From FIG. 1, the invention includes impeller front shroud 2 and the impeller back shroud 3 were designed by tilting. And D.sub.2=117 mm, we determine the modified coefficient k.sub.3 by CFD numerical calculation, after the numerical calculation, K.sub.3=0.932, Therefore, the pitch position diameter D.sub.t is calculated by (3). As a result, D.sub.t=109 mm.

[0078] From FIG. 1, the original thickness of the impeller front shroud and the impeller back shroud δ.sub.2 is 2 mm, we determine the modified coefficient k.sub.4 by CFD numerical calculation, after the numerical calculation, K.sub.4=0.75. Therefore, the optimized thickness of the impeller front shroud and the impeller back shroud δ.sub.1 is calculated by (4). As a result, δ.sub.1=1.5 mm.

[0079] From FIG. 2, the original pump long blade number Z.sub.1 is 6, and from FIG. 3, you can get the optimal method of the splitter blade. The optimized number of long blade on the pump Z.sub.2 is calculated by (5). As a result, Z.sub.2=4, the calculated result of Z.sub.2 is taken upward, further Z.sub.3=4.

[0080] From FIG. 2, the original model of scroll of long blade 5 Φ is 100° and Z.sub.1=6, Z.sub.2=4. So the optimized scroll of long blade 6 Φ.sub.1 is calculated by (6). As a result, Φ.sub.1=162°.

[0081] From FIG. 3, you can determine the impeller inlet diameter of the splitter blades D.sub.si by (7). And the impeller outlet diameter D.sub.2 is 117 min, we determine the modified coefficient D′ by CFD numerical calculation, after the numerical calculation, D′=0.72, Therefore, D.sub.si can be calculated by (7). As a result, D.sub.si=84.2 mm.

[0082] From FIG. 3, the length of arc of long blades S.sub.1 is 64 mm, and we determine the modified coefficient K.sub.5 by CFD numerical calculation, after the numerical calculation, K.sub.5=0.6. Therefore, the length of arc of split blades S.sub.2 can be calculated by (8). As a result, S.sub.2=38.5 mm.

[0083] From FIG. 3, the angle between two adjacent long blades θ is 72°, the modified coefficient K.sub.6 can be calculated by CFD numerical calculation, after the numerical calculation, K.sub.6=0.4. Therefore, the circumferential offset angle of splitter blades θ.sub.1 can be calculated by (9). As a result, θ.sub.1=28.8°.

[0084] From FIG. 3, the tilt angle of long blades a.sub.1 is 55°, the modified coefficient K.sub.7 can be calculated by CFD numerical calculation, after the numerical calculation, K.sub.7=0.8. Therefore, the tilt angle of splitter blades a.sub.2 can be calculated by (10). As a result, a.sub.2=44°.

[0085] The inlet and outlet thickness of the splitter blade is consistent with the long blade in the invention. And the thickness of the inlet of the splitter blade is 3 mm, the thickness of the outlet of the splitter blade is 7 mm, the thickness in the middle of the splitter blade is 53 mm.

[0086] As is shown in awe 4, we can see the performance curve of the original model of jet self-priming centrifugal pump, and the FIG. 5 shown that the performance curve of the optimized jet self-priming centrifugal pump. Comparing to two figure, it can be clearly seen that the flow-head curve drops sharply after the optimization. As a result, the pump efficiency is improved and the head is raised without exceeding the rated power. We optimize the pump by the above geometric parameters, as a result, the head was increased to 131.23 ft, the mass flow rate Q becomes 3600 L/H, the rotating speed n up to 2995 r/m, the efficiency was increased to 17.2%, and the noise was reduced to 78 dB. The impeller optimization is completed on the jet self-priming centrifugal pump with rated power of 800 w.