CN113704897A - Hydraulic design method of self-air-entraining submersible aerator - Google Patents

Abstract

The invention discloses a hydraulic design method of a self-air-entraining submersible aerator, which comprises the following steps: step 1, according to the output power P of the motor_ShaftRated speed n, submerging depth h and air inflow Q_{Qi (Qi)}Calculating parameters of the impeller; step 2, calculating size parameters of guide vanes; and 3, calculating the size parameter of the aeration disc. The design calculation formula of the geometric dimensions of the impeller, the guide vane and the aeration disc is given, and the gas-water mixing proportion, the gas compression and the jet stability are consideredAnd 4 parameters of power, rotating speed, design submerging depth and air inflow of the submersible motor are selected and matched, and the geometric dimensions of the impeller, the guide vane and the aeration disc are designed and calculated.

Description

Hydraulic design method of self-air-entraining submersible aerator

Technical Field

The invention belongs to the technical field of aerators, and particularly relates to a hydraulic design method of a self-air-entraining submersible aerator.

Background

Aeration is one of the important process flows for treating sewage by an activated sludge method. The self-air-entraining submersible aerator utilizes a submersible motor to drive an impeller to rotate, so that nearby water flow enters the impeller. At the same time, the centrifugal force of the impeller creates a vacuum at the inlet, drawing air in through the bleed duct. The air and the water are fully mixed in the guide vane and are ejected out through the jet pipe on the aeration disc, and effective convection circulation is formed. The air is divided into a large number of fine bubbles, and the fine bubbles are fully mixed with the activated sludge and the sewage, so that the growth of aerobic microorganisms is promoted, organic pollutants in the water body are degraded, and the sewage is purified.

The core of the self-air-entraining submersible aerator for realizing the aeration function is a hydraulic component which consists of an impeller, a guide vane and an aeration disc. The geometrical size of the hydraulic component determines the performance of the aerator, so a hydraulic method is needed to improve the aeration performance of the aerator.

Disclosure of Invention

Therefore, the technical problem to be solved by the invention is that the existing hydraulic design method is complex and tedious, and the performance of the obtained aerator cannot meet the requirement of air input under the submerging depth.

Therefore, the technical scheme is that the hydraulic design method of the self-air-entraining type submersible aerator comprises the following steps:

step 1, according to the output power P of the motor_ShaftRated speed n, submerging depth h and air inflow Q_{Qi (Qi)}The parameters of the impeller are calculated,

step 2, calculating size parameters of guide vanes;

and 3, calculating the size parameter of the aeration disc.

Preferably, the step 1 comprises:

the parameters of the impeller include:

dimension D of air entraining pipe_{Qi (Qi)}

Wind speed V_{Qi (Qi)}Taking 7-12m/s, and taking the standard pipeline size similar to the calculated value;

impeller air inlet diameter D₀

D₀＝k_D0×D_{Qi (Qi)}

k_D0Taking 0.6-0.8;

diameter D of blade air inlet₁

D₁＝k_D1×D₀

k_D1Taking 1.05-1.3;

gas flow (after compression) Q at the impeller exit_{Gas 2}

In the formula P₀Is the local atmospheric pressure (Pa), ρ_{Water (W)}Is the density of water (kg/m)³) G acceleration of gravity (m/s)²) (ii) a Water flow Q in aerator_{Water (W)}

V is the proportion of water in the gas-water mixture, and is 40% -60% of the water;

density ρ of gas-liquid mixture at impeller exit_{Mixing of}

Where rho_{Qi (Qi)}Is the air density (kg/m) at local atmospheric pressure³)；

Hydraulic efficiency eta of aerator_h

Total efficiency eta of aerator

η＝k_η×η_h

In the formula k_ηTaking 0.6-0.8;

lift H of aerator

Theoretical lift H of aerator_t

Width b of impeller outlet₂

In the formula k_b2Taking 0.6-0.8;

sltotra slip coefficient sigma

In the formula, z is the number of leaves, and 4-7 leaves are selected; beta is a₂Setting an angle for the outlet of the blade, wherein the angle is 60-90 degrees;

the assumed value of the outer diameter of the impeller is D_{2 false}

Axial surface flow velocity V at impeller outlet_m2

Peripheral speed U at the impeller outlet₂

The calculated value of the impeller outer diameter is D₂

D₂And D_{2 false}Comparing, and if the two are the same, taking the value of the outer diameter of the impeller; if the two are greatly different, re-assuming D_{2 false}Re-calculating according to the steps until D₂And D_{2 false}Identical or similar;

the intersection point of the cover plate and the blade does not exceed the front 1/3 of the length of the blade, and the diameter of the intersection point is recorded as a blade water inlet D_{1 Water}

Suppose the diameter D of the impeller water inlet_{0 water}

Measurement D_{0 water}The total area between the inner impeller cover plates, i.e. the water inlet area of the impeller, is denoted S_{0 water}；

Velocity of inflow V_{Water (W)}

Inlet flow velocity V_{Water (W)}Is 3m/s, if V_{Water (W)}If the calculated value has a large deviation, re-assuming D_{0 water}Up to V_{Water (W)}Meets the requirements.

Preferably, the step 2 comprises:

the dimensional parameters of the guide vane include:

diameter D of inlet of guide vane₃

D₃＝k_D3×D₃

In the formula k_D3Taking 1.01-1.02.

Diameter D of guide vane outlet₄

D₄＝k_D4×D₃

In the formula k_D4Taking 1.4-1.6.

Preferably, the step 3 comprises:

the size parameters of the aeration disc comprise:

the inner diameter of the aeration disc is equal to the diameter D of the guide vane outlet₄

The aeration disc consists of a plurality of jet pipes, the number of the jet pipes is the same as that of the guide vanes, and the installation angle is tangent to the working surface of the guide vane flow channel; the shape of the jet flow pipe adopts a rectangular pipe, and the rectangular section is larger than the size of a flow passage of the guide vane outlet;

equivalent hydraulic diameter D of jet pipe_{Equivalent weight}

In the formula, a is the length of the overflowing section of the rectangular pipe, and b is the width of the overflowing section of the rectangular pipe;

selecting the outer diameter D of the aeration disc₅And measuring the length L of the jet pipe, wherein the length of the jet pipe is 3-4 times of the equivalent hydraulic diameter in order to keep the water flow stable and prevent the bubbles from being expanded excessively.

The technical scheme of the invention has the following advantages: the hydraulic design method of the self-air-entraining submersible aerator can simply and conveniently design the hydraulic component of the aerator by considering factors such as air-water mixing ratio, gas compression, jet stability and the like, and meets the requirement of designing the air inflow under the submerging depth through a prototype test.

Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and drawings.

The technical solution of the present invention is further described in detail by the accompanying drawings and embodiments.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention. In the drawings:

FIG. 1 is a flow chart of the present invention.

FIG. 2 is a plan view of a hydraulic component of one embodiment of the present invention.

Fig. 3 is a plan view of an impeller according to an embodiment of the present invention.

FIG. 4 is a plan view of a blade of one embodiment of the present invention

FIG. 5 is a plan view of a guide vane of an embodiment of the present invention.

Fig. 6 is a plan view of an aeration panel according to an embodiment of the present invention.

Fig. 7 is a schematic structural view of an aerator according to the present invention.

Wherein, 1, impeller, 2 guide vanes, 3 aeration discs, 4 impeller air inlet D ₀5. blade water inlet D _{1 Water}6. impeller external diameter D₂7. diameter of blade inlet D ₁8, diameter D of impeller water inlet _{0 water}9. blade outlet setting angle beta ₂10 impeller water inlet area, 11 guide vane inlet diameter D ₃12 guide vane outlet diameter/aeration disc inner diameter D ₄13, outer diameter D of aeration disc ₅14, the length L of the jet pipe, 15, the length a of the flow section of the rectangular pipe, 16, the width b of the flow section of the rectangular pipe, 17, and the jet pipe.

Detailed Description

The preferred embodiments of the present invention will be described in conjunction with the accompanying drawings, and it will be understood that they are described herein for the purpose of illustration and explanation and not limitation.

The invention provides a hydraulic design method of a self-air-entraining submersible aerator, which is shown in figures 1-7 and adopts design input

Output power P of motor_Shaft＝3.3kW；

Rated speed n 1380 rpm;

designing the submerging depth h to be 4 m;

design air input Q_{Qi (Qi)}＝55m³/h；

Design step

Design of impeller

Dimension D of air entraining pipe_{Qi (Qi)}

Wind speed V in the bleed air duct_{Qi (Qi)}Taking 7-12m/s, taking the standard pipeline size close to the calculated value, and taking the air guide pipe size D_{Qi (Qi)}＝0.05m。

Impeller air inlet diameter D₀

D₀＝k_D0×D_{Qi (Qi)}＝0.76×0.05＝0.038m

k_D0Taking 0.6-0.8.

Dimension D of blade inlet₁

D₁＝k_D1×D₀＝1.105×0.038＝0.042m

k_D1Taking 1.05-1.3.

Gas flow (after compression) Q at the impeller exit_{Gas 2}

In the formula P₀Is the local atmospheric pressure (Pa), ρ_{Water (W)}Is the density of water (kg/m)³) G acceleration of gravity (m/s)²)。

Water flow Q in aerator_{Water (W)}

In the formula, V is the proportion of water in the gas-water mixture, and is generally 40% -60%.

Density ρ of gas-liquid mixture at impeller exit_{Mixing of}

Where rho_{Qi (Qi)}Is the air density (kg/m) at local atmospheric pressure³)。

Aeration machineHydraulic efficiency eta_h

Total efficiency eta of aerator

η＝k_η×η_h＝0.64×61％＝38.7％

In the formula k_ηTaking 0.6-0.8.

Lift H of aerator

Theoretical lift H of aerator_t

Width b of impeller outlet₂

In the formula k_b2Taking 0.7-0.9.

Sltotra slip coefficient sigma

Wherein z is the number of leaves, and is usually 4-7; beta is a₂The angle for the blade exit is typically 60 to 90.

The assumed value of the outer diameter of the impeller is D_{2 false}＝0.268m

Axial surface flow velocity V at impeller outlet_m2

Peripheral speed U at the impeller outlet₂

The calculated value of the impeller outer diameter is D₂

D₂And D_{2 false}Comparing, and if the two are the same, taking the value of the outer diameter of the impeller; if the two are greatly different, re-assuming D_{2 false}Re-calculating according to the steps until D₂And D_{2 false}Identical or similar.

The intersection point of the cover plate and the blade does not exceed the front 1/3 of the length of the blade, and the diameter of the point is recorded as D_{1 Water}

The length of the blade is 120mm, the front end of the blade length is 40mm from the intersection point of the cover plate and the blade, and D is measured_{1 Water}＝0.111m

Suppose the diameter D of the impeller water inlet_{0 water}＝0.161m

Measurement D_{0 water}The total area between the inner impeller cover plates, i.e. the water inlet area of the impeller, is denoted S_{0 water}＝0.004975m²Velocity of inflow V_{Water (W)}

Inlet flow velocity V_{Water (W)}Generally about 3m/s, if V_{Water (W)}If the calculated value has a large deviation, re-assuming D_{0 water}Up to V_{Water (W)}Meets the requirements.

Design of guide vane

Diameter D of inlet of guide vane₃

D₃＝k_D3×D₂＝1.015×0.268＝0.272m

In the formula k_D3Take 1.01-1.02。

Diameter D of guide vane outlet₄

D₄＝k_D4×D₃＝1.4×0.272＝0.38m

In the formula k_D4Taking 1.4-1.6.

The design of the guide vane blade refers to a design method of a radial positive guide vane of a centrifugal pump.

Design of aeration disc

The inner diameter of the aeration disc is equal to the diameter D of the guide vane outlet₄＝0.38m

The aeration disc is composed of a plurality of jet pipes, and the installation angle of the jet pipes is tangent to the working surface of the guide vane flow channel. The shape of the jet pipe adopts a standard rectangular pipe, 50 multiplied by 40 multiplied by 3, and the rectangular section is slightly larger than the size of a flow passage of the guide vane outlet.

Equivalent hydraulic diameter D of jet pipe_{Equivalent weight}

In the formula, a is the length of the flow section of the rectangular pipe, and b is the width of the flow section of the rectangular pipe.

Selecting the outer diameter D of the aeration disc₅The length L of the jet pipe was 143mm, which was 0.6 m.

The length of the jet pipe is 3.73 times of the equivalent hydraulic diameter, and the jet pipe meets the requirement.

Up to this point, the geometry of the hydraulic components (impeller, guide vanes, aeration disc) of the self-bleed submersible aerator has been calculated.

It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.

Claims (4)

1. A hydraulic design method of a self-air-entraining submersible aerator is characterized by comprising the following steps:

step 1, outputting power according to a motor_ShaftRated speed n, submerging depth h and air inflow Q_{Qi (Qi)}Calculating parameters of the impeller;

step 2, calculating size parameters of guide vanes;

and 3, calculating the size parameter of the aeration disc.

2. The hydraulic design method of a self-air-entraining submersible aerator as claimed in claim 1 wherein step 1 comprises:

the parameters of the impeller include:

dimension D of air entraining pipe_{Qi (Qi)}

Wind speed V_{Qi (Qi)}Taking 7-12m/s, and taking the standard pipeline size similar to the calculated value;

impeller air inlet diameter D₀

D₀＝k_D0×D_{Qi (Qi)}

k_D0Taking 0.6-0.8;

diameter D of blade air inlet₁

D₁＝k_D1×D₀

k_D1Taking 1.05-1.3;

gas flow (after compression) Q at the impeller exit_{Gas 2}

In the formula P₀Is the local atmospheric pressure (Pa), ρ_{Water (W)}Is the density of water (kg/m)³) G acceleration of gravity (m/s)²)；

Water flow Q in aerator_{Water (W)}

V is the proportion of water in the gas-water mixture, and is 40% -60% of the water;

density ρ of gas-liquid mixture at impeller exit_{Mixing of}

Where rho_{Qi (Qi)}Is the air density (kg/m) at local atmospheric pressure³)；

Hydraulic efficiency eta of aerator_h

Total efficiency eta of aerator

η＝k_η×η_h

In the formula k_ηTaking 0.6-0.8;

lift H of aerator

Theoretical lift H of aerator_t

Width b of impeller outlet₂

In the formula k_b2Taking 0.6-0.8;

sltotra slip coefficient sigma

Wherein z is the number of leaves, and 4-7 leaves are selected; beta is a₂Setting an angle for the outlet of the blade, wherein the angle is 60-90 degrees;

the assumed value of the outer diameter of the impeller is D_{2 false}

Axial surface flow velocity V at impeller outlet_m2

Peripheral speed U at the impeller outlet₂

The calculated value of the impeller outer diameter is D₂

D₂And D_{2 false}Comparing, and if the two are the same, taking the value of the outer diameter of the impeller; if the two are greatly different, re-assuming D_{2 false}Re-calculating according to the steps until D₂And D_{2 false}Identical or similar;

the intersection point of the cover plate and the blade does not exceed the front 1/3 of the length of the blade, and the diameter of the intersection point is recorded as a blade water inlet D_{1 Water}

Suppose the diameter D of the impeller water inlet_{0 water}

Measurement D_{0 water}The total area between the inner impeller cover plates, i.e. the water inlet area of the impeller, is denoted S_{0 water}；

Velocity of inflow V_{Water (W)}

Inlet flow velocity V_{Water (W)}Is 3m/s, if V_{Water (W)}If the calculated value has a large deviation, re-assuming D_{0 water}Up to V_{Water (W)}Meets the requirements.

3. The hydraulic design method of a self-air-entraining submersible aerator as claimed in claim 2 wherein step 2 comprises:

the dimensional parameters of the guide vane include:

diameter D of inlet of guide vane₃

D₃＝k_D3×D₂

In the formula k_D3Taking 1.01-1.02.

Diameter D of guide vane outlet₄

D₄＝k_D4×D₃

In the formula k_D4Taking 1.4-1.6.

4. A method of hydraulic design of a self-entraining air submersible aerator as claimed in claim 3 wherein step 3 includes:

the size parameters of the aeration disc comprise:

the inner diameter of the aeration disc is equal to the diameter D of the guide vane outlet₄

The aeration disc consists of a plurality of jet pipes, the number of the jet pipes is the same as that of the guide vanes, and the installation angle is tangent to the working surface of the guide vane flow channel; the shape of the jet flow pipe adopts a rectangular pipe, and the rectangular section is larger than the size of a flow passage of the guide vane outlet;

equivalent hydraulic diameter D of jet pipe_{Equivalent weight}

In the formula, a is the length of the overflowing section of the rectangular pipe, and b is the width of the overflowing section of the rectangular pipe;

selecting the outer diameter D of the aeration disc₅And measuring the length L of the jet pipe, wherein the length of the jet pipe is 3-4 times of the equivalent hydraulic diameter in order to keep the water flow stable and prevent the bubbles from being expanded excessively.

Images