Axial flow pump design method based on impeller and guide vane placing angle matching

Abstract

The invention relates to an axial flow pump design method based on impeller and guide vane placement angle matching, which comprises the following steps: step 1, determining the outer diameter D2 of an impeller and the diameter dh of a hub of an axial flow pump, and calculating the circumferential speed u2 of an outlet of the impeller according to a formula # imgabs0 #; 2, the flow Q, the outer diameter D2 of the impeller and the diameter dh of a hub are known, and the axial surface speed vm2 of the impeller is calculated; 3, presetting an impeller outlet setting angle beta b2, and calculating the relative speed w2 of the impeller outlet; 4, calculating the circumferential component of the absolute speed of the impeller outlet; 5, according to the geometrical relationship of the impeller outlet speed triangles, the included angle alpha < 2 > of the impeller outlet absolute speed and the circumferential speed is calculated; and 5, selecting the guide vane inlet placement angle to be equal to the included angle alpha 2 between the impeller outlet absolute speed and the circumferential speed. The impeller and the guide vane can be designed according to the impeller blade outlet placing angle and the guide vane inlet placing angle, flowing in the axial flow pump can be improved, the impeller and the guide vane with better adaptability are obtained, and therefore hydraulic loss is reduced, and the efficiency of the whole pump is improved.

Description

Technical Field

[0001] The present invention relates to an axial flow pump design method, and specifically to a hydraulic design method for an axial flow pump, which can take into account the impeller blade outlet placement angle and the guide vane inlet placement angle to design the impeller and guide vanes, improve the flow in the axial flow pump, obtain a more optimally adapted impeller and guide vanes, thereby reducing hydraulic losses and improving the efficiency of the entire pump. Background Art

[0002] As a general fluid machinery, axial flow pumps are widely used in industries such as drainage and irrigation, and play an important role in the national economy. In axial flow pumps, impellers and guide vanes are generally used together, so the matching design between impellers and guide vanes is very important. Summary of the invention

[0003] In view of the above problems, the main purpose of the present invention is to provide a hydraulic design method for an axial flow pump, which can take into account the impeller blade outlet placement angle and the guide vane inlet placement angle to design the impeller and guide vanes, thereby improving the flow in the axial flow pump and obtaining more optimally adapted impellers and guide vanes, thereby reducing hydraulic losses and improving the efficiency of the entire pump.

[0004] The present invention solves the above technical problems through the following scheme: an axial flow pump design method based on the matching of impeller and guide vane placement angles, the axial flow pump design method based on the matching of impeller and guide vane placement angles comprises the following steps:

[0005] Step 1: Determine the axial flow pump impeller outer diameter D2 and hub diameter d h , according to the formula Calculate the circumferential velocity u2 of the impeller outlet;

[0006] Step 2: Flow rate Q, impeller outer diameter D2 and hub diameter d h It is known that according to the formula Calculate the impeller axial velocity v m2 ;

[0007] Step 3: Preset the impeller outlet placement angle β b2 , according to the formula And the geometric relationship of the impeller outlet triangle is used to calculate the relative velocity w2 at the impeller outlet;

[0008] Step 4: Calculate the circumferential component v of the impeller outlet absolute velocity based on the geometric relationship of the impeller outlet velocity triangle 2(u) for:

[0009] Step 5: According to the geometric relationship of the impeller outlet velocity triangle, the angle α2 between the impeller outlet absolute velocity and the circumferential velocity is calculated as:

[0010] Step 5: Select the guide vane inlet placement angle to be equal to the angle α2 between the impeller outlet absolute velocity and the circumferential velocity.

[0011] The positive progressive effect of the present invention is that: the present invention provides an axial flow pump design method based on the matching of impeller and guide vane placement angles; the present invention can take into account the impeller blade outlet placement angle and the guide vane inlet placement angle to design the impeller and guide vane, which can improve the flow in the axial flow pump and obtain more optimally matched impellers and guide vanes, thereby reducing hydraulic losses and improving the efficiency of the entire pump, thereby achieving the purpose of energy saving. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is an expanded view of the axial flow pump impeller and the intermediate flow surface cascade of the guide vane of the present invention.

[0013] Figure 2 It is an axial view of the impeller and guide vanes in the present invention.

[0014] Figure 3 This is the turbulent kinetic energy flow field diagram.

[0015] Figure 4 This is the flow field diagram of the expanded surface of the cascade. DETAILED DESCRIPTION

[0016] Preferred embodiments of the present invention are given below in conjunction with the accompanying drawings to illustrate the technical solutions of the present invention in detail.

[0017] Figure 1 It is an expanded view of the axial flow pump impeller and the intermediate flow surface cascade of the guide vane of the present invention. Figure 2 : is an axial view of the impeller and guide vane in the present invention. Figure 1 and 2 As shown: The axial flow pump design method based on the matching of the impeller and the guide vane placement angle provided by the present invention comprises the following steps:

[0018] Step 1: Determine the axial flow pump impeller outer diameter D2 and hub diameter d h , according to the formula Calculate the circumferential velocity u2 of the impeller outlet;

[0019] Step 2: Flow rate Q, impeller outer diameter D2 and hub diameter d h It is known that according to the formula Calculate the impeller axial velocity v m2 ;

[0020] Step 3: Preset the impeller outlet placement angle β b2 , according to the formula And the geometric relationship of the impeller outlet triangle is used to calculate the relative velocity w2 at the impeller outlet;

[0021] Step 4: Calculate the circumferential component v of the impeller outlet absolute velocity based on the geometric relationship of the impeller outlet velocity triangle 2(u) for:

[0022] Step 5: According to the geometric relationship of the impeller outlet velocity triangle, the angle α2 between the impeller outlet absolute velocity and the circumferential velocity is calculated as:

[0023] Step 5: Select the guide vane inlet placement angle to be equal to the angle α2 between the impeller outlet absolute velocity and the circumferential velocity.

[0024] The following is a specific implementation example:

[0025] The invention uses a specific speed n s = Take 570 axial flow pump as an example: Figure 1 This is an expanded view of the axial flow pump impeller and the intermediate flow surface cascade of the guide vane of the present invention. Figure 2 1 is the relative velocity w2 of the impeller outlet, 2 is the circumferential velocity u2 of the impeller outlet, 3 is the absolute velocity v2 of the impeller outlet, and 4 is the axial velocity v m2 , 5 is the angle between the impeller outlet circumferential speed and the circumferential speed α2, 6 is the angle between the impeller outlet relative speed and the circumferential direction β2, 7 is the guide vane inlet placement angle α3, 8 is the guide vane outlet placement angle α4, which is usually 90°, 9 is the impeller outer diameter D2, and 10 is the hub diameter d h When α 3＝ When α2, it is more conducive to the flow in the guide vane.

[0026] Circumferential speed

[0027] Axis speed

[0028] Relative speed

[0029] Absolute velocity circular component

[0030] Angle between absolute speed and circumferential speed

[0031] The guide vane inlet placement angle

[0032] In this case, when designing the impeller blades, the blade outlet placement angle is designed to be 50°, the impeller outer diameter D2 = 250mm, and the hub diameter d h =140mm, design flow rate Q=670m 3 / h, speed n = 1450r / min, according to the above formula, the angle between the absolute speed and the circumferential speed is 21°, so when designing the guide vane, the guide vane blade inlet placement angle is 21°.

[0033] Figure 3 is the turbulent kinetic energy flow field diagram, such as Figure 3 As shown, it can be seen that the overall turbulent kinetic energy in the flow basin is small, indicating that the flow field loss is small, and there are few places where the turbulent kinetic energy is concentrated, indicating that the overall flow field is relatively uniform.

[0034] Figure 4 is the flow field diagram of the expanded surface of the cascade. Figure 4 As shown, it can be seen that after the fluid comes out of the impeller outlet, it can flow into the next flow basin guide vane smoothly without collision, and the absolute velocity direction of the fluid is also relatively consistent with the placement of the guide vane, which is beneficial to reducing the flow field loss here.

[0035] Table 1: Table 1 shows the hydraulic performance of different guide vane inlet placement angles in the present invention.

[0036] Table 1

[0037] Q / Q <![CDATA[Q(m 3 / h)]]> H(m) η(%) P(kW) H leaf(m) η leaves (%) Guide vane loss (%) 0.90 60165 9.13 69.00 21.67 1076 81.34 -15.12 1.00 668.50 9.10 76.11 21.75 10.24 85.65 -11.27 110 73535 864 8080 2142 952 8897 .900

[0038] From Table 1, we can see that the hydraulic performance meets the design requirements and the CFD calculation results are better.

[0039] Through CFD calculation and analysis, it can be found that when the guide vane inlet placement angle is the angle derived from the formula, it has better hydraulic performance and flow field distribution, which is beneficial to reduce hydraulic loss and improve the performance of the whole pump. This angle is derived from theoretical calculation. Since the fluid is an unsteady flow field during the operation of the impeller, the velocity distribution is not uniform, so the hydraulics can be further optimized based on this calculated angle.

[0040] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected, and the scope of the present invention to be protected is defined by the attached claims and their equivalents.

Claims

1. A design method for an axial flow pump based on the matching of the impeller and guide vane placement angles, characterized in that: The axial flow pump design method based on the matching of impeller and guide vane placement angles comprises the following steps: Step 1: Determine the axial flow pump impeller outer diameter D2 and hub diameter d h , according to the formula Calculate the circumferential velocity u2 of the impeller outlet; Step 2: Flow rate Q, impeller outer diameter D2 and hub diameter d h It is known that according to the formula Calculate the impeller axial velocity v m2 ; Step 3: Preset the impeller outlet placement angle β b2 , according to the formula And the geometric relationship of the impeller outlet triangle is used to calculate the relative velocity w2 at the impeller outlet; Step 4: Calculate the circumferential component v of the impeller outlet absolute velocity based on the geometric relationship of the impeller outlet velocity triangle 2(u) for: Step 5: According to the geometric relationship of the impeller outlet velocity triangle, the angle α2 between the impeller outlet absolute velocity and the circumferential velocity is calculated as: Step 5: Select the guide vane inlet placement angle to be equal to the angle α2 between the impeller outlet absolute velocity and the circumferential velocity.

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