CN105864098A - Design method for double-end folded edge blade structure of impeller of middle-high-ratio rotating speed centrifugal pump - Google Patents

Abstract

The invention provides a design method for a double-end folded edge blade structure of an impeller of a middle-high-ratio rotating speed centrifugal pump. Blades are staggered at the position of an inlet and an outlet of the impeller through the folded edge blades, and the staggered blades are designed to have different inlet placement angles and wrap angles and have different widths at the position of the inlet of the impeller. According to the requirement of the folded edge blades, the impeller inlet equivalent diameter, the impeller inlet diameter, the impeller outlet diameter, the impeller outlet width, the blade outlet placement angles, the blade wrap angles, the arc length corresponding to the outlet position between the folded edge upper blade and the folded edge lower blade of the impeller and the impeller blade thickness are reasonably designed, and an impeller runner is divided into two runner bodies. When the middle-high-ratio rotating speed centrifugal pump runs under the non-design work condition, normal running of the pump is well guaranteed through the two runner bodies.

Description

A kind of method for designing of middle higher specific speed centrifugal pump impeller both-end edge folding blades structure

Technical field

The present invention relates to higher specific speed impeller vane of centrifugal pumps construction design method in one, particularly to higher specific speed in one The method for designing of centrifugal pump impeller both-end edge folding blades structure.

Background technology

Pump is a kind of application universal machine the most widely, of a great variety, has inseparable relation with the life of the mankind, all It is the place having liquid to flow, nearly all has the operation work of pump.Along with scientific and technological level constantly improves, the neck that pump uses Territory the most constantly expands.Centrifugal pump structure is varied, is the one being most widely used in various pump, is widely used in city In each department of the social lifes such as feedwater, petrochemical industry, shipping industry, space flight and aviation, agricultural irrigation and national economy.Cause This proposes the highest requirement to centrifugal pump performance, such as anti-cavitation performance, the requirement of inclined stable conditions operation, low noise The requirement of vibration and high reliability etc..Traditional centrifugal pump impeller Hydraulic Design Method is theoretical and the combination of experience, can not At utmost meet constantly appearance newly designs requirement.Therefore, in order to continue to meet, these constantly occur newly designs requirement, need Structure to be improved designs, and places short blade at impeller channel near exit exactly such as the design of low-specific-speed short blade offset and can improve Hydraulic performance in impeller and the pump housing.Running environment recently as middle higher specific speed centrifugal pump is continually changing, in may causing Higher specific speed centrifugal pump runs under off-design behaviour.Traditional impeller Hydraulic Design Method can make centrifugal pump run under multi-state, It can however not ensure that the operating point of centrifugal pump deviation is exactly the multi-state point of design.Therefore, may result in middle higher specific speed can not be just Normal operation can produce noise and vibration, aggravating working environment, is unfavorable for production efficiency.

Summary of the invention

For problem produced in middle higher specific speed centrifugal pump running, the invention provides higher specific speed centrifugal pump in one The method for designing of impeller both-end edge folding blades structure.Making blade stagger at impeller import and export by edge folding blades, design is staggered Blade has different import laying angles and cornerite and has different width at impeller inlet, rationally sets according to the requirement of edge folding blades Count out the import equivalent diameter of impeller, impeller inlet diameter, impeller outlet diameter, impeller outlet width, blade exit laying angle, Arc length that between subtended angle of blade, the upper and lower blade of impeller flanging, exit is corresponding, impeller blade thickness, make impeller channel be divided into two, Central higher specific speed centrifugal pump runs under off-design behaviour, and two runners well ensure that pump runs normally.Can effectively subtract Light blade loads, improves anti-cavitation performance and the feasibility of operation of centrifugal pump；Realize above-mentioned purpose be the technical scheme is that 1, impeller inlet equivalent diameter D₀Determined by following formula:

$D_0=\left\{\begin{array}{cc}(0.41n^{-1.13}{Q}^{0.18}{H}^{0.45}+0.05H+0.5Q^{1.3})& (H\≤50,Q\≤3600)\\ (0.84n^{0.07}{Q}^{0.58}{H}^{-0.3}+50H^{-1.21}+4.5+0.03Q^{0.8})& (H>50,Q\≤3600)\\ (5.31n^{-0.33}{Q}^{0.33}{H}^{-0.02}+0.077n^{-1}{H}^{0.5}+0.3H^{-2.2})& (H>50,Q>3600)\\ (Q^{0.017}+0.11)(2.7n^{-0.33}{Q}^{0.33}{H}^{-0.02}+23.4n^{-1}{H}^{0.5})& (H\≤50,Q>3600)\end{array}\right.$

In formula:

D₀Impeller inlet equivalent diameter, m；

Q flow, m³/s；

H lift, m；

N rotating speed, rev/min；

2, impeller blade entrance width b₁Determined by below equation:

(a) impeller flanging blade entrance width b₁₁Determined by below equation:

$b_{11}=\left\{\begin{array}{cc}0.24Q^{0.6}{H}^{-0.25}-0.72n^{-1.1}{H}^{0.4}+0.0012n^{-2.1}{Q}^{0.2}{H}^{-0.12}& (H\&GreaterEqual;50,Q>3600)\\ -0.00444n^{0.89}{Q}^{1.09}{H}^{-1.1}+0.72Q^{0.6}{H}^{-0.25}-14.1n^{-1}{H}^{0.48}& (H\&GreaterEqual;50,Q\&le;3600)\\ 0.23Q^{0.5}{H}^{-0.25}+1.32n^{-1}H+0.2n^{-1}{Q}^{1.02}{H}^{-1.5}& (H<50,Q>3600)\\ 0.0039{\mathrm{nQH}}^{-1.1}-0.81Q^{0.5}{H}^{-0.25}+7.33n^{-1}{H}^{0.5}& (H<50,Q>3600)\end{array}\right.$

(b) impeller flanging lower blade entrance width b₁₂Determined by below equation:

$b_{12}=\left\{\begin{array}{cc}0.161Q^{0.6}{H}^{-0.25}-0.482n^{-1.1}{H}^{0.4}+0.0008n^{-2.1}{Q}^{0.2}{H}^{-0.12}& (H\&GreaterEqual;50,Q>3600)\\ -0.003n^{0.89}{Q}^{1.09}{H}^{-1.1}+0.48Q^{0.6}{H}^{-0.25}-9.45n^{-1}{H}^{0.48}& (H\&GreaterEqual;50,Q\&le;3600)\\ 0.1541Q^{0.5}{H}^{-0.25}+0.884n^{-1}H+0.134n^{-1}{Q}^{1.02}{H}^{-1.5}& (H<50,Q>3600)\\ 0.0029{\mathrm{nQH}}^{-1.1}-0.543Q^{0.5}{H}^{-0.25}+4.911n^{-1}{H}^{0.5}& (H<50,Q>3600)\end{array}\right.$

In formula:

b₁₁Upper impeller inlet width, m；

b₁₂Lower impeller entrance width, m；

N rotating speed, rev/min；

Q flow, m³/s；

H lift, m；

3, impeller outlet diameter D₂Determined by following formula:

$D_2\left\{\begin{array}{cc}50.1(1.3Z^{0.04}-1.1)(0.0002H+0.88)n^{-0.83}{Q}^{-0.1}{H}^{0.375}& (H\&le;50,Q\&le;3600)\\ 50.1(0.016Z+0.934)(0.06932InH+0.72)n^{-0.83}{Q}^{-0.1}{H}^{0.375}& (H>50,Q\&le;3600)\\ 49.9(0.042Z+0.82)(0.007Q^2+0.03Q+0.92)n^{-0.83}{Q}^{0.083}{H}^{0.375}& (H>50,Q>3600)\\ 49.9(0.7Z^{-0.1}+1.02)(0.0015Q+0.83)n^{-0.83}{Q}^{0.083}{H}^{0.375}& (H\&le;50,Q>3600)\end{array}\right.$

In formula:

D₂Impeller outlet diameter, m；

The Z number of blade, piece；

N rotating speed, rev/min；

Q flow, m³/s；

H lift, m；

4, vane inlet lays angle beta₁Size is determined by following formula:

A angle beta is laid in the flanging blade import of () impeller₁₁Determined by below equation:

${\mathrm{\&beta;}}_{11}=\left\{\begin{array}{cc}arctan\left(\right(0.07Z+0.7\left)\frac{8.1}{{\mathrm{nD}}_0^2{b}_{11}}\right)& (Q\&le;3600)\\ \arctan \left(\right(1.21Z^{0.02}+0.02\left)\frac{6.9}{{\mathrm{nD}}_0^2{b}_{11}}\right)& (Q>3600)\end{array}\right.$

B angle beta is laid in the flanging lower blade import of () impeller₁₂Determined by below equation:

${\mathrm{\&beta;}}_{12}=\left\{\begin{array}{cc}arctan\left(\right(0.07Z+0.7\left)\frac{8.1}{{\mathrm{nD}}_0^2{b}_{12}}\right)& (Q\&le;3600)\\ \arctan \left(\right(1.21Z^{0.02}+0.02\left)\frac{6.9}{{\mathrm{nD}}_0^2{b}_{12}}\right)& (Q>3600)\end{array}\right.$

In formula:

β₁₁Blade import laying angle, °；

β₁₂Lower blade import laying angle, °；

D₀Impeller inlet equivalent diameter, m；

b₁₁Upper impeller inlet width, m；

b₁₂Lower impeller entrance width, m；

Q flow, m³/s；

The Z number of blade, piece；

5, angle beta is laid in impeller blade outlet₂Determined by below equation:

A angle beta is laid in the outlet of () impeller flanging blade₂₁Determined by below equation:

${\mathrm{\&beta;}}_{21}=H(0.71+3.9\frac{Z}{H}+0.0049H-0.16Z+0.0003)$

B angle beta is laid in the outlet of () impeller flanging lower blade₂₂Determined by below equation:

${\mathrm{\&beta;}}_{22}=H(0.0003H+0.87)(0.87+3.9\frac{Z}{H}+0.0059H-0.14Z)$

In formula:

β₂₁Blade outlet laying angle, °；

β₂₂Lower blade outlet laying angle, °；

H lift, m；

The Z number of blade, piece；

6, blade exit width b₂Size is determined by following formula:

(a) impeller flanging blade exit width b₂₁Determined by below equation:

$b_{21}=0.0057(-0.005D_2^2+0.03D_2+0.987)n^{0.5}{Q}^{0.5}{H}^{-0.5}$

(b) impeller flanging lower blade outlet mouth width b₂₂Determined by below equation:

$b_{22}=0.0133(-0.006D_2^2+0.031D_2+0.99)n^{0.5}{Q}^{0.5}{H}^{-0.5}$

In formula:

b₂₁Blade exit width, m；

b₂₂Lower blade exit width, m；

D₂Impeller outlet diameter, m；

N rotating speed, rev/min；

Q flow, m³/s；

H lift, m；

7, subtended angle of bladeSize is determined by following formula:

(a) impeller flanging blade corneriteDetermined by below equation:

(b) impeller flanging lower blade corneriteDetermined by below equation:

In formula:

Blade cornerite, °；

Lower blade cornerite, °；

D₀Impeller inlet diameter, m；

D₂Impeller outlet diameter, m；

The Z number of blade, piece；

8, the arc length size that between the upper and lower blade of impeller flanging, exit is corresponding is determined by below equation:

A arc length l that between the upper and lower blade of () impeller flanging, import department is corresponding₁Size is determined by below equation:

B arc length l that between the upper and lower blade of () impeller flanging, exit is corresponding₂Size is determined by below equation:

In formula:

l₁The arc length that between the upper and lower blade of impeller flanging, import department is corresponding, m；

l₂The arc length that between the upper and lower blade of impeller flanging, exit is corresponding, m；

D₀Impeller inlet equivalent diameter, m；

D₂Impeller outlet diameter, m；

Blade cornerite, °；

Lower blade cornerite, °；

9, the import and export thickness S of impeller blade is determined by below equation:

(a) impeller edge folding blades import department thickness S₁Determined by below equation:

$\left\{\begin{array}{c}{S}_{11}=0.0042D_0+0.0002\\ S_{12}=0.004D_0+0.0001\end{array}\right.$

(b) impeller edge folding blades exit thickness S₂Determined by below equation:

$\left\{\begin{array}{c}{S}_{21}=0.002D_2+0.0004\\ S_{22}=0.002D_2+0.0003\end{array}\right.$

In formula:

S₁₁Impeller flanging blade import department thickness, m；

S₁₂Impeller flanging lower blade import department thickness, m；

S₂₁Impeller flanging blade exit thickness, m；

S₂₂Impeller flanging lower blade exit thickness, m；

D₂Impeller outlet diameter, m；

D₀Impeller inlet equivalent diameter, m.

The invention has the beneficial effects as follows:

By the optimum structure parameter of higher specific speed centrifugal pump in the blade appropriate design at flanging impeller outlet, improve centrifugal pump Performance and running in stability.

Accompanying drawing explanation

Fig. 1 is the plane figure of the embodiment of the present invention.

Fig. 2 is the axial plane figure of the embodiment of the present invention.

Fig. 3 is that the present invention implements impeller blade schematic diagram.

Fig. 1: β₁₁Blade stagger angle, β₁₂Lower blade stagger angle, β₂Blade exit established angle,On Subtended angle of blade,Lower blade cornerite.

Fig. 2: D₀Impeller inlet equivalent diameter, D₂Impeller outlet diameter, b₁₁Blade entrance width, b₁₂Lower blade Entrance width, b₂Blade exit width, S₁₁Impeller flanging blade import department thickness, S₁₂Impeller flanging lower blade import department Thickness, S₂₁Impeller flanging blade exit thickness, S₂₂Impeller flanging lower blade exit thickness.

Fig. 3: 1 impeller blade, 2 impeller lower blades, l₁The arc length that between blade, import department is corresponding up and down, l₂Up and down The arc length that between blade, exit is corresponding.

Detailed description of the invention

Design requires: design conditions flow is 0.096764 cube of meter per second, and design conditions lift is 60 meters, rotating speed is 2900 turns/ Second, g takes 10 meters/square metre, and the number of blade takes 5 pieces.

The numerical value of impeller structure parameter: D can be obtained according to data above₀=170mm；D₂=390mm；β₁₁=17 °；β₁₂=18 °； β₂₁=21 °；β₂₂=21 °；b₁₁=11mm；b₁₂=8mm；b₂₁=10mm；b₂₂=7mm；S₁₁=6mm； S₁₂=5mm；S₂₁=7mm；S₂₂=6mm；

In the design process, the selection of other coefficient needs to carry out coefficient according to concrete practical situation and chooses, and the spiral case such as impeller is joined Number needs to select according to the actual motion of pump.

Above, by the present invention with reference to illustrating that embodiment is made, but the present invention is not limited to above-described embodiment, also wraps Containing the other embodiments in the range of present inventive concept or variation.

Claims (9)

1. the method for designing of higher specific speed centrifugal pump impeller both-end edge folding blades structure in a kind, it is characterised in that: centrifugal in design During pump impeller blade, impeller blade both-end uses layering folded edges；Wherein impeller inlet equivalent diameter D₀Determined by following formula:

$D_0=\left\{\begin{array}{cc}(0.41n^{-1.13}{Q}^{0.18}{H}^{0.45}+0.05H+0.5Q^{1.3})& (H\&le;50,Q\&le;3600)\\ (0.84n^{0.07}{Q}^{0.58}{H}^{-0.3}+50H^{-1.21}+4.5+{0.03}^{0.8})& (H>50,Q\&le;3600)\\ (5.31n^{-0.33}{Q}^{0.33}{H}^{-0.02}+0.077n^{-1}{H}^{0.5}+0.3H^{-2.2})& (H>50,Q>3600)\\ (Q^{0.017}+0.11)(2.7n^{-0.33}{Q}^{0.33}{H}^{-0.02}+23.4n^{-1}{H}^{0.5})& (H\&le;50,Q>3600)\end{array}\right.$

In formula:

D₀Impeller inlet equivalent diameter, m；

Q flow, m³/s；

H lift, m；

N rotating speed, rev/min.

The method for designing of a kind of middle higher specific speed centrifugal pump impeller both-end edge folding blades structure the most as claimed in claim 1, its feature It is: impeller blade entrance width b₁Determined by below equation:

(a) impeller flanging blade exit width b₁₁Determined by below equation:

$b_{11}=\left\{\begin{array}{cc}0.24Q^{0.6}{H}^{-0.25}-0.72n^{-1.1}{H}^{0.4}+0.0012n^{-2.1}{Q}^{0.2}{H}^{-0.12}& \left(H\&GreaterEqual;50,Q>3600\right)\\ -0.00444n^{0.89}{Q}^{1.09}{H}^{-1.1}+0.72Q^{0.6}{H}^{-0.25}-14.1n^{-1}{H}^{0.48}& \left(H\&GreaterEqual;50,Q\&le;3600\right)\\ 0.23Q^{0.5}{H}^{-0.25}+1.32n^{-1}H+0.2n^{-1}{Q}^{1.02}{H}^{-1.5}& \left(H<50,Q>3600\right)\\ 0.0039{\mathrm{nQH}}^{-1.1}-0.81Q^{0.5}{H}^{-0.25}+7.33n^{-1}{H}^{0.5}& \left(H<50,Q>3600\right)\end{array}\right.$

(b) impeller flanging blade exit width b₁₂Determined by below equation:

$b_{12}=\left\{\begin{array}{cc}0.161Q^{0.6}{H}^{-0.25}-0.482n^{-1.1}{H}^{0.4}+0.0008n^{-2.1}{Q}^{0.2}{H}^{-0.12}& \left(H\&GreaterEqual;50,Q>3600\right)\\ -0.003n^{0.89}{Q}^{1.09}{H}^{-1.1}+0.48Q^{0.6}{H}^{-0.25}-9.45n^{-1}{H}^{0.48}& \left(H\&GreaterEqual;50,Q\&le;3600\right)\\ 0.1541Q^{0.5}{H}^{-0.25}+0.884n^{-1}H+0.134n^{-1}{Q}^{1.02}{H}^{-1.5}& \left(H<50,Q>3600\right)\\ 0.0029{\mathrm{nQH}}^{-1.1}-0.543Q^{0.5}{H}^{-0.25}+4.911n^{-1}{H}^{0.5}& \left(H<50,Q>3600\right)\end{array}\right.$

In formula:

b₁₁Upper impeller inlet width, m；

b₁₂Lower impeller entrance width, m；

N rotating speed, rev/min；

Q flow, m³/s；

H lift, m.

The method for designing of a kind of middle higher specific speed centrifugal pump impeller both-end edge folding blades structure the most as claimed in claim 1, its feature It is: impeller outlet diameter D₂Determined by following formula formula:

$D_2=\left\{\begin{array}{cc}50.1\left(1.3Z^{0.04}-1.1\right)\left(0.0002H+0.88\right)n^{-0.83}{Q}^{-0.1}{H}^{0.375}& \left(H\&le;50,Q\&le;3600\right)\\ 50.1\left(0.016Z+0.934\right)\left(0.06932InH+0.72\right)n^{-0.83}{Q}^{-0.1}{H}^{0.375}& \left(H>50,Q\&le;3600\right)\\ 49.9\left(0.042Z+0.82\right)\left(0.007Q^2+0.03Q+0.92\right)n^{-0.83}{Q}^{0.083}{H}^{0.375}& \left(H>50,Q>3600\right)\\ 49.9\left(0.7Z^{-0.1}+1.02\right)\left(0.0015Q+0.83\right)n^{-0.83}{Q}^{0.083}{H}^{0.375}& \left(H\&le;50,Q>3600\right)\end{array}\right.$

In formula:

D₂Impeller outlet diameter, m；

The Z number of blade, piece；

N rotating speed, rev/min；

Q flow, m³/s；

H lift, m.

The method for designing of a kind of middle higher specific speed centrifugal pump impeller both-end edge folding blades structure the most as claimed in claim 1, its feature It is: angle beta is laid in impeller blade import₁Determined by below equation:

A angle beta is laid in the flanging blade import of () impeller₁₁Determined by below equation:

${\mathrm{\&beta;}}_{11}=\left\{\begin{array}{cc}\arctan \left(\right(0.07Z+0.7\left)\frac{8.1}{{\mathrm{nD}}_0^2{b}_{11}}\right)& (Q\&le;3600)\\ \arctan \left(\right(1.21Z^{0.02}+0.02\left)\frac{6.9}{{\mathrm{nD}}_0^2{b}_{11}}\right)& (Q>3600)\end{array}\right.$

B angle beta is laid in the flanging lower blade import of () impeller₁₂Determined by below equation:

${\mathrm{\&beta;}}_{12}=\left\{\begin{array}{cc}\arctan \left(\right(0.07Z+0.7\left)\frac{8.1}{{\mathrm{nD}}_0^2{b}_{12}}\right)& (Q\&le;3600)\\ \arctan \left(\right(1.21Z^{0.02}+0.02\left)\frac{6.9}{{\mathrm{nD}}_0^2{b}_{12}}\right)& (Q>3600)\end{array}\right.$

In formula:

β₁₁Blade import laying angle, °；

β₁₂Lower blade import laying angle, °；

D₀Impeller inlet equivalent diameter, m；

b₁₁Upper impeller inlet width, m；

b₁₂Lower impeller entrance width, m；

Q flow, m³/s；

The Z number of blade, piece.

The method for designing of a kind of middle higher specific speed centrifugal pump impeller both-end edge folding blades structure the most as claimed in claim 1, its feature It is: angle beta is laid in impeller blade outlet₂Determined by below equation:

A angle beta is laid in the outlet of () impeller flanging blade₂₁Determined by below equation:

${\mathrm{\&beta;}}_{21}=H(0.71+3.9\frac{Z}{H}+0.0049H-0.16Z+0.0003)$

B angle beta is laid in the outlet of () impeller flanging lower blade₂₂Determined by below equation:

${\mathrm{\&beta;}}_{22}=H(0.0003H+0.87)(0.87+3.9\frac{Z}{H}+0.0059H-0.14Z)$

In formula:

β₂₁Blade outlet laying angle, °；

β₂₂Lower blade outlet laying angle, °；

The Z number of blade, piece；

H lift, m.

The method for designing of a kind of middle higher specific speed centrifugal pump impeller both-end edge folding blades structure the most as claimed in claim 1, its feature It is: impeller blade exit width b₂Determined by below equation:

(a) impeller flanging blade exit width b₂₁Determined by below equation:

$b_{21}=0.0057(-0.005D_2^2+0.03D_2+0.987)n^{0.5}{Q}^{0.5}{H}^{-0.5}$

(b) impeller flanging lower blade exit width b₂₂Determined by below equation:

$b_{22}=0.0133(-0.006D_2^2+0.031D_2+0.99)n^{0.5}{Q}^{0.5}{H}^{-0.5}$

In formula:

b₂₁Blade exit width, m；

b₂₂Lower blade exit width, m；

D₂Impeller outlet diameter, m；

N rotating speed, rev/min；

Q flow, m³/s；

H lift, m.

The method for designing of a kind of middle higher specific speed centrifugal pump impeller both-end edge folding blades structure the most as claimed in claim 1, its feature It is: impeller blade corneriteDetermined by below equation:

(a) impeller flanging blade corneriteDetermined by below equation:

(b) impeller flanging lower blade corneriteDetermined by below equation:

In formula:

Blade cornerite, °；

Lower blade cornerite, °；

D₀Impeller inlet equivalent diameter, m；

D₂Impeller outlet diameter, m；

β₂Blade exit laying angle, °；

b₂Impeller outlet width, m.

The method for designing of a kind of middle higher specific speed centrifugal pump impeller both-end edge folding blades structure the most as claimed in claim 1, its feature It is: the arc length size that between the upper and lower blade of impeller flanging, import and export is corresponding is determined by below equation:

A arc length l that between the upper and lower blade of () impeller flanging, import department is corresponding₁Size is determined by below equation:

B arc length l that between the upper and lower blade of () impeller flanging, exit is corresponding₂Size is determined by below equation:

In formula:

l₁The arc length that between the upper and lower blade of impeller flanging, import department is corresponding, m；

l₂The arc length that between the upper and lower blade of impeller flanging, exit is corresponding, m；

D₀Impeller inlet equivalent equivalent diameter, m；

D₂Impeller outlet diameter, m；

Blade cornerite, °；

Lower blade cornerite, °.

The method for designing of a kind of middle higher specific speed centrifugal pump impeller both-end edge folding blades structure the most as claimed in claim 1, it is special Levy and be: the import and export thickness S of impeller blade is determined by below equation:

(a) impeller flanging blade import department thickness S₁Determined by below equation:

$\left\{\begin{array}{c}{S}_{11}=0.0042D_0+0.0002\\ S_{12}=0.004D_0+0.0001\end{array}\right.$

(b) impeller flanging lower blade exit thickness S₂Determined by below equation:

$\left\{\begin{array}{c}{S}_{21}=0.002D_2+0.0004\\ S_{22}=0.002D_2+0.0003\end{array}\right.$

In formula:

S₁₁Thickness at impeller flanging blade import mouth, m；

S₁₂Impeller flanging lower blade import department thickness, m；

S₂₁Impeller flanging blade exit thickness, m；

S₂₂Impeller flanging lower blade exit thickness, m；

D₂Impeller outlet diameter, m；

D₀Impeller inlet equivalent diameter, m.