CN101383541A - Design method for highly efficient rear incline centrifugal type cooling external fan for high-voltage asynchronous motor - Google Patents

Abstract

A design method of an efficient back tilting centrifuging cooling external fan of a high voltage asynchronous motor belongs to the research technique of a high voltage high active motor. The method is characterized in that a backing tilting centrifuging fan with higher efficiency is improved; under the conditions of guaranteeing the mechanical strength, noise and temperature elevation, according to the anticipant depressed wear and tear loss of the fan, wind pressure and blast volume needed by the fan are satisfied; and the basic size of the fan, the shape of blades and the amount of the blades are accounted; wherein shaped lines of the blades and the angle of an inlet and an outlet are determined while the technique is considered; and the size is optimized and amended to reduce wind friction loss. The fan has low noise and high efficiency; the blades are added in the beginning end to ensure that the impact loss of the inlet of the blades is reduced; and the fan has good aero performance and is suitable for the high voltage asynchronous motor of an enclosed totally cooling external fan with IP 44 or IP 54 level of protection in YKK series.

Description

The method for designing of the highly efficient rear incline centrifugal type cooling external fan of high-voltage asynchronous motor

Technical field

The present invention relates to a kind of method for designing of highly efficient rear incline centrifugal type cooling external fan of high-voltage asynchronous motor, belong to the technical field of high efficient, high pressure asynchronous motor.

Background technology

The whole world increases day by day to the consumption of the energy at present, the energy-conservation problem that becomes various countries' attention.Electric energy especially receives publicity as important secondary energy sources.There are some researches prove that 60%～70% of world's energy output consumes by various motor (mainly being asynchronous motor).China is an energy big country, and is huge to the consumption of electric energy.In view of such situation, the efficiency level that improves asynchronous motor is the important behave of energy efficient, simultaneously to the protection of the saving of resource, environment with improve also highly beneficial.From energy-conservation and angle environmental protection, research high efficient, high pressure motor is one of development trend of present electromechanics trade.Therefore, it is great to carry out the Research Significance of efficient high-pressure threephase asynchronous.

Improve the efficient of big-and-middle-sized high-voltage asynchronous motor, will reduce the motor total losses exactly, be i.e. stator and rotor copper loss, iron loss, mechanical loss and stray loss.For the high efficient, high pressure asynchronous motor, mechanical loss accounts for about 40% of total losses, if can reduce mechanical loss, will be very optimistic to the efficient that improves big-and-middle-sized high-voltage asynchronous motor.Therefore, mostly producer by adopting more rational aeration structure pattern, change wind path, select low frictional torque bearing for use, improving technology and wait and realize.More external main motor company such as ABB, Siemens etc., mixed ventilation and the axial ventilation patterns of adopting replace radial ventilation in the past more in the medium-sized high pressure asynchronous machine.What the most of asynchronous motor of China adopted is the radial ventilation pattern, and along with the development improvement of technology, also research and development produce novel mixed ventilation and axial ventilation motor in recent years, and are applied on the middle-size and small-size motor.The research to electric motor fan abroad is subjected to the space flight and aviation Influence and Development, begins to pay close attention to the tube-axial fan of airfoil type, and is applied on the motor through a series of transformations.Domesticly also just begin to develop the axial type energy-saving fan at twentieth century, be mainly used in small size asynchronous motor, efficient improves significantly.With regard to efficient, tube-axial fan is apparently higher than centrifugal fan, but blast low be the big defective of one, in large-size machine, be difficult to be applied.Domestic big-and-middle-sized high-voltage three-phase asynchronous motor generally adopts radially centrifugal fan at present, because the restriction of the performance of fan own has big difficulty to improving the motor whole efficiency.According to the knowledge of blower fan theory, radially there is the shortcoming that efficient is low, loss is big in centrifugal fan.According to theory analysis, adopt the hypsokinesis centrifugal fan if change into, cooperate with suitable size and dimension, enough blast can be provided, can loss reduce again, electric efficiency is improved.

Current on big-and-middle-sized high-voltage three-phase asynchronous motor the application of hypsokinesis centrifugal fan uncommon because the common more complicated of the shape of its blade, technology difficulty is big.Disk-form before the hypsokinesis centrifugal fan has three kinds, flat shroud, taper shroud and arc shroud, both aeroperformances of back are for; Blade import department increases top to reducing entrance loss, and it is favourable to improve aeroperformance; Select suitable to go into, exit angle also can make fan performance reach better.Take all factors into consideration the technological level and the processing cost of factory, adopt to have disc type hypsokinesis centrifugal fan before top flat, the relative velocity direction angle alpha that go in theory, exit angle is chosen as with gas enters blade equates to be the best.Blade dimensions will satisfy required air quantity of motor and blast, and lobe numbers is obtained by ventilation blower theory and design of electrical motor experience, satisfies the requirement of mechanical strength and noise aspect simultaneously.New fan blast and air quantity reduce, and efficient improves, and make the fan loss reduce, and have improved electric efficiency, are applicable to the unidirectional operation motor.

Summary of the invention

The present invention be directed to the problem that electromagnetism optimization is difficult to make that high-voltage motor efficient further increases substantially and a kind of method that is applied in the highly efficient rear incline centrifugal type cooling external fan on the high pressure large and medium asynchronous motor that proposes.Reduce the wastage by changing the fan pattern, purpose is to reduce the fan loss to improve the efficient and the performance of high pressure large and medium asynchronous motor, helps to solve the low problem of China's high-voltage motor efficiency level.Mostly related fan is at middle and small motor on some lists of references at present, because the loss of middle and small motor own is less, wind path is simple in structure, windage is little, institute's required airflow and blast require low, needn't worry the problem that pressure head is not enough, can use the very high tube-axial fan of efficient instead, thereby loss reduction amplitude is big, and efficient improves significantly.And in big-and-middle-sized high-voltage asynchronous motor, wind path structure more complicated, windage is big, if adopt aerofoil fan, the problem of blast deficiency can occur, can't satisfy the requirement of motor cooling.Because the selection of fan pattern is restricted, the raising of efficient is so uneasy relatively.

The cooling external fan of present big-and-middle-sized high-voltage asynchronous motor adopts radially centrifugal fan of classic flat-plate, traditional empirical method of selection of dimension reference, and there is certain defective in this on new and effective motor research.The present invention is directed to the concrete condition of high efficient, high pressure asynchronous motor, reduced air quantity and blast, be replaced by the hypsokinesis centrifugal fan, and on blade shape, carried out some optimizations.Guaranteeing to reduce the fan loss to greatest extent under the prerequisite of electric machine temperature rise in limit value, to improve electric efficiency.Described method specifically contains following steps successively in computer:

Step (1). calculate according to the following steps and use required air quantity Q and the blast H of the centrifugal cooling external fan of hypsokinesis rear motor cooling instead:

Step (1.1) is used hypsokinesis centrifugal fan rear motor total losses instead and is $P_{\mathrm{loss}}^{\′}=P_{\mathrm{loss}}-\mathrm{\Δ}{P}_f,$ Wherein, P _LossTotal losses when adopting centrifugal fan radially originally, Δ P _fBe the fan loss that designing requirement descends, P _LossAnd Δ P _fBe all datum;

Step (1.2) is calculated as follows required air quantity Q and the blast H of motor cooling:

$\left\{\begin{array}{c}Q=\frac{\mathrm{\&Sigma;}{P}_{\mathrm{loss}}^{\&prime;}}{c_a{\mathrm{\&theta;}}_a}\\ H={\mathrm{<figure-callout\; id="2"\; label="ZQ"\; filenames="A200710303762E00142.png"\; state="\{\{state\}\}">ZQ</figure-callout>}}^2\end{array}\right.$

Wherein, θ _aThe temperature rise of motor air, c _aAir specific heat is set-point, and Z is the resistance of exogenous wind transportation work style;

Step (2). determine the basic size of fan by following formula and constraints: inside diameter D _F1, outer diameter D _F2, width of blade b:

Step (2.1) is determined D according to following formula _F1With D _F2Relation:

$\left\{\begin{array}{c}\stackrel{\&OverBar;}{l}=\frac{D_{f2}-{\mathrm{<figure-callout\; id="1"\; label="D\; f"\; filenames="A200710303762E00141.png,A200710303762E00142.png"\; state="\{\{state\}\}">D</figure-callout>}}_f}{2{\mathrm{<figure-callout\; id="2"\; label="D\; f"\; filenames="A200710303762E00142.png"\; state="\{\{state\}\}">D</figure-callout>}}_f}=0.15~0.20\\ {\mathrm{<figure-callout\; id="2"\; label="D\; f"\; filenames="A200710303762E00142.png"\; state="\{\{state\}\}">D</figure-callout>}}_f=(1.1~1.5){\mathrm{<figure-callout\; id="1"\; label="D\; f"\; filenames="A200710303762E00141.png,A200710303762E00142.png"\; state="\{\{state\}\}">D</figure-callout>}}_f\end{array}\right.$

Wherein, l is the fan blade relative length;

Step (2.2) is determined D according to step (2.1) and following formula _F1With D _F2:

$H=\frac{\mathrm{<figure-callout\; id="0"\; label="H\; H"\; filenames="A200710303762E00142.png"\; state="\{\{state\}\}">H</figure-callout>}}{H_{}}\&times;{\mathrm{\&eta;}}_0{\mathrm{\&rho;\&pi;}}^2{\left(\frac{n}{60}\right)}^2({\mathrm{<figure-callout\; id="2"\; label="D\; f"\; filenames="A200710303762E00142.png"\; state="\{\{state\}\}">D</figure-callout>}}_f^2-{\mathrm{<figure-callout\; id="1"\; label="D\; f"\; filenames="A200710303762E00141.png,A200710303762E00142.png"\; state="\{\{state\}\}">D</figure-callout>}}_f^1)$

Wherein, n is the motor rated speed, and ρ is an atmospheric density, η ₀Gas efficiency of movement during for the fan zero load, H/H ₀For being blast and the ratio of unloaded blast, get fan efficiency eta on the fan external characteristic curve _fThe value of maximum point place correspondence;

Step (2.3), determine fan blade width b according to following formula:

$Q=\frac{1}{2}\&CenterDot;\left({\mathrm{\&delta;}}_0\mathrm{\&pi;}{D}_{f2}n\right)\&CenterDot;\left(\mathrm{\&lambda;\&pi;}{D}_{f2}b\right)$

Wherein, δ ₀Be the air quantity correction factor, λ is given value for considering the real area coefficient of vane thickness loss;

Step (2.4) is judged D _F1Whether satisfy with b:

$\mathrm{\&pi;}{D}_{f1}b>1.5\&times;\left(\frac{1}{4}\mathrm{\&pi;}{\mathrm{<figure-callout\; id="1"\; label="D\; f"\; filenames="A200710303762E00141.png,A200710303762E00142.png"\; state="\{\{state\}\}">D</figure-callout>}}_f^1\right),$

Satisfy, carry out next step; Do not satisfy, return step (2.2);

Step (3). the size value according to step (2) obtains, recomputate air quantity and blast, make that new air quantity and blast are Q ' and H ', and judge whether to satisfy:

$\left\{\begin{array}{c}\left|\frac{Q\&prime;-Q}{Q}\right|\&le;1\%\\ \left|\frac{H\&prime;-H}{H}\right|\&le;5\%\\ H\&prime;>H\end{array}\right.,$

Satisfy, carry out next step; Do not satisfy, return the size that step (2.1) redefines fan;

Step (4). calculate fan loss P _f=Q ' H '/η _f, η _f=0.25～0.30;

Step (5). determine the fan blade shape according to following steps:

Step (5.1) is set inlet blade angle β ₁Equal outlet blade angle β ₂, β ₂=25 ⁰～45 ⁰

Step (5.2) is calculated as follows blade circular arc respective radius R _n, central angle alpha _n, α _nPairing chord length mn:

$\left\{\begin{array}{c}\tan \frac{{\mathrm{\&alpha;}}_{\mathrm{<figure-callout\; id="2"\; label="n"\; filenames="A200710303762E00142.png"\; state="\{\{state\}\}">n</figure-callout>}}}{2}=\frac{D_{f2}-D_{f1}}{{\mathrm{<figure-callout\; id="2"\; label="D\; f"\; filenames="A200710303762E00142.png"\; state="\{\{state\}\}">D</figure-callout>}}_f+D_{f1}}c\tan {\mathrm{\&beta;}}_1\\ \stackrel{\&OverBar;}{\mathrm{mn}}=\sqrt{{\left(\frac{{\mathrm{<figure-callout\; id="2"\; label="D\; f"\; filenames="A200710303762E00142.png"\; state="\{\{state\}\}">D</figure-callout>}}_f}{2}\right)}^2+{\left(\frac{{\mathrm{<figure-callout\; id="1"\; label="D\; f"\; filenames="A200710303762E00141.png,A200710303762E00142.png"\; state="\{\{state\}\}">D</figure-callout>}}_f}{2}\right)}^2-2\&CenterDot;\frac{{\mathrm{<figure-callout\; id="2"\; label="D\; f"\; filenames="A200710303762E00142.png"\; state="\{\{state\}\}">D</figure-callout>}}_f}{2}\&CenterDot;\frac{{\mathrm{<figure-callout\; id="1"\; label="D\; f"\; filenames="A200710303762E00141.png,A200710303762E00142.png"\; state="\{\{state\}\}">D</figure-callout>}}_f}{2}\cos {\mathrm{\&alpha;}}_n}\\ R_n=\frac{\stackrel{\&OverBar;}{\mathrm{mn}}}{2\sin \left(\frac{{\mathrm{\&alpha;}}_n}{2}\right)}\end{array}\right.$

Then the blade arc length is that the blade physical length is l _n=R _nα _n

Step (5.3), the internal diameter size D definite according to step (3) _F1The maximum gauge that calculates blade increase top part is D _1max, minimum diameter is D _1min, average diameter is D _1m:

$\left\{\begin{array}{c}{\mathrm{<figure-callout\; id="1"\; label="D"\; filenames="A200710303762E00141.png,A200710303762E00142.png"\; state="\{\{state\}\}">D</figure-callout>}}_{1\max }=(1.01~1.05)D_{f1}\\ {\mathrm{<figure-callout\; id="1"\; label="D"\; filenames="A200710303762E00141.png,A200710303762E00142.png"\; state="\{\{state\}\}">D</figure-callout>}}_{1\min }=(0.8~0.98)D_{f1}\\ D_{1m}=\frac{D_{1\max }+{\mathrm{<figure-callout\; id="1"\; label="D"\; filenames="A200710303762E00141.png,A200710303762E00142.png"\; state="\{\{state\}\}">D</figure-callout>}}_{1\mathrm{<figure-callout\; id="2"\; label="min"\; filenames="A200710303762E00142.png"\; state="\{\{state\}\}">min</figure-callout>}}}{2}\end{array}\right.$

Step (6). definite according to the following steps fan blade is counted N:

Step (6.1), if by hypsokinesis centrifugal fan blade computing formula, number of blades N:

$N=8.5\frac{\sin {\mathrm{\&beta;}}_2}{1-{\mathrm{<figure-callout\; id="1"\; label="D\; f"\; filenames="A200710303762E00141.png,A200710303762E00142.png"\; state="\{\{state\}\}">D</figure-callout>}}_f/{\mathrm{<figure-callout\; id="2"\; label="D\; f"\; filenames="A200710303762E00142.png"\; state="\{\{state\}\}">D</figure-callout>}}_f}$

Step (6.2), calculate number of blades N when pressing fan performance the best:

$N=\mathrm{\&tau;\&pi;}\frac{{\mathrm{<figure-callout\; id="2"\; label="D\; f"\; filenames="A200710303762E00142.png"\; state="\{\{state\}\}">D</figure-callout>}}_f+D_{f1}}{D_{f2}-{\mathrm{<figure-callout\; id="1"\; label="D\; f"\; filenames="A200710303762E00141.png,A200710303762E00142.png"\; state="\{\{state\}\}">D</figure-callout>}}_f}\sin {\mathrm{\&beta;}}_b$

Wherein, ${\mathrm{\&beta;}}_b=\frac{{\mathrm{\&beta;}}_1+{\mathrm{\&beta;}}_2}{2},$ τ is a leaf grating density, and τ=0.5+1.7sin β ₂

Step (6.3) satisfies rigidity condition, and when promptly blade height should be not less than the blade gap distance at blade centre-height place, then number of blades N was:

$(\mathrm{\&pi;}\frac{{\mathrm{<figure-callout\; id="2"\; label="D\; f"\; filenames="A200710303762E00142.png"\; state="\{\{state\}\}">D</figure-callout>}}_f+{\mathrm{<figure-callout\; id="1"\; label="D\; f"\; filenames="A200710303762E00141.png,A200710303762E00142.png"\; state="\{\{state\}\}">D</figure-callout>}}_f}{2N}-g)\&le;\frac{D_{f2}-{\mathrm{<figure-callout\; id="1"\; label="D\; f"\; filenames="A200710303762E00141.png,A200710303762E00142.png"\; state="\{\{state\}\}">D</figure-callout>}}_f}{2}$

Wherein, g is a vane thickness, g=5～10mm;

Step (6.4) according to the blade requirement of step (6.1)～(6.3), is determined the scope that number of blades is chosen.

For the high-voltage asynchronous motor fan, it is not obvious to the reduction of loss only to reduce fan dimension, and changes the fan pattern, from improving the efficient of fan itself, adds the optimization on the size and dimension, loss to reduce amplitude bigger.Though the BI fan has been considered present technological level than radial complexity on the technology during this method for designing, can not cause the significantly increase of processing difficulties and cost.

Description of drawings

Fig. 1. the inventive method flow chart.

Fig. 2. the centrifugal fan external characteristic curve: 1. blade radial, 2. blade hypsokinesis, 3 blades lean forward.

Fig. 3. centrifugal fan radially.

Fig. 4. hypsokinesis centrifugal fan blade shape.

Fig. 5. the top structure that the hypsokinesis centrifugal fan increases: 1. top.

Concrete enforcement side mode

The present invention is a starting point to reduce the fan loss, carries out new design, is used for the high pressure large and medium asynchronous motor.Owing on the basis of existing electric machine structure, only change the structure of fan part, so except that the relevant parameter of fan, other structural parameters are all constant.To consider the following aspects during design comprehensively:

1) size of fan wind supply quantity;

2) height of electric machine temperature rise;

3) size of fan loss;

4) height of ventilation noise;

5) manufacturability is bad.

This fan is that the radially centrifugal cooling external fan with former YKK series high voltage asynchronous motor changes the centrifugal cooling external fan of the higher hypsokinesis of efficient into, method flow as shown in Figure 1, embodiment is as follows:

1. motor air quantity Q and blast H were constant before and after the supposition fan changed, and total losses are P during former radially centrifugal fan _Loss, use hypsokinesis centrifugal fan rear motor total losses instead and be $P_{\mathrm{loss}}^{\&prime;}=P_{\mathrm{loss}}-\mathrm{\&Delta;}{P}_f,$ Wherein, Δ P _fFor the fan of design desires to be reduced to the fan loss value, according to

$\left\{\begin{array}{c}Q=\frac{\mathrm{\&Sigma;}{P}_{\mathrm{loss}}^{\&prime;}}{c_a{\mathrm{\&theta;}}_a}\\ H={\mathrm{ZQ}}^2\end{array}\right.---\left(1\right)$

Required air quantity Q and the blast H of the centrifugal cooling external fan of hypsokinesis rear motor cooling used in calculating instead, wherein, and θ _aThe temperature rise of motor air, c _aAir specific heat is set-point, and Z is determined by the wind path structure for the resistance of exogenous wind transportation work style;

With the air quantity that calculates, blast as the primary election value, determine the basic size of fan by following formula and constraints: inside diameter D _F1, outer diameter D _F2, width of blade b.In order to guarantee that fan has better aeroperformance, the fan blade size should satisfy

$\left\{\begin{array}{c}\stackrel{\&OverBar;}{l}=\frac{D_{f2}-{\mathrm{<figure-callout\; id="1"\; label="D\; f"\; filenames="A200710303762E00141.png,A200710303762E00142.png"\; state="\{\{state\}\}">D</figure-callout>}}_f}{2{\mathrm{<figure-callout\; id="2"\; label="D\; f"\; filenames="A200710303762E00142.png"\; state="\{\{state\}\}">D</figure-callout>}}_f}=0.15~0.20\\ {\mathrm{<figure-callout\; id="2"\; label="D\; f"\; filenames="A200710303762E00142.png"\; state="\{\{state\}\}">D</figure-callout>}}_f=(1.1~1.5){\mathrm{<figure-callout\; id="1"\; label="D\; f"\; filenames="A200710303762E00141.png,A200710303762E00142.png"\; state="\{\{state\}\}">D</figure-callout>}}_f\\ \mathrm{\&pi;}{D}_{f1}b>1.5\&times;\left(\frac{1}{4}\mathrm{\&pi;}{\mathrm{<figure-callout\; id="1"\; label="D\; f"\; filenames="A200710303762E00141.png,A200710303762E00142.png"\; state="\{\{state\}\}">D</figure-callout>}}_f^1\right)\end{array}\right.---\left(2\right)$

Know D thus _F1, D _F2And the range of choice of b, according to

$\left\{\begin{array}{c}Q=\frac{1}{2}\&CenterDot;\left({\mathrm{\&delta;}}_0\mathrm{\&pi;}{D}_{f2}n\right)\&CenterDot;\left(\mathrm{\&lambda;\&pi;}{D}_{f2}b\right)\\ H=\frac{\mathrm{<figure-callout\; id="0"\; label="H\; H"\; filenames="A200710303762E00142.png"\; state="\{\{state\}\}">H</figure-callout>}}{H_{}}\&times;{\mathrm{\&eta;}}_0{\mathrm{\&rho;\&pi;}}^2{\left(\frac{n}{60}\right)}^2({\mathrm{<figure-callout\; id="2"\; label="D\; f"\; filenames="A200710303762E00142.png"\; state="\{\{state\}\}">D</figure-callout>}}_f^2-{\mathrm{<figure-callout\; id="1"\; label="D\; f"\; filenames="A200710303762E00141.png,A200710303762E00142.png"\; state="\{\{state\}\}">D</figure-callout>}}_f^1)\end{array}\right.---\left(3\right)$

Determine D _F1, D _F2And b.Wherein, l is the fan blade relative length, and n is the motor rated speed; λ is for considering the real area coefficient of vane thickness loss, and ρ is an atmospheric density, η ₀Gas efficiency of movement during for the fan zero load, δ ₀For the air quantity correction factor, as shown in table 1, H/H ₀For the ratio of blast, get fan efficiency eta on the fan external characteristic curve with unloaded blast _fThe value of maximum point place correspondence is seen shown in Figure 2;

Table 1 fan correlation computations parameter reference value

3. according to the new fan dimension value of determining, recomputate air quantity and blast, make that new air quantity and blast are Q ' and H ', and if improve back Q '＜Q, but reduce because of fan improves the back loss, so air quantity was reduced to some extent, can not influence temperature rise yet, the windage that increases when considering the windage that neglected when wind path calculates and operation, then blast is with H '〉H is advisable, and satisfies:

$\left\{\begin{array}{c}\left|\frac{Q\&prime;-Q}{Q}\right|\&le;1\%\\ \left|\frac{H\&prime;-H}{H}\right|\&le;5\%\\ H\&prime;>H\end{array}\right.---\left(4\right)$

Otherwise need redefine the size of fan;

4. recomputate fan loss P _f=Q ' H '/η _f

5. in view of original external fan shape some shortcomings on performance,, need blade shape is done further to improve for improving its aeroperformance.Mainly comprise and determine that blade is gone into, exit angle β ₁, β ₂, vane type line, and increase blade top:

A) the going into of fan, blade outlet angle β ₁, β ₂Determine

Because air-flow enters velocity magnitude and direction and wheel speed and inequality before the fan, causes blade inlet place gas and impeller that a relative velocity direction angle alpha is arranged.And certain entrance loss when entering blade, air-flow is arranged, with β ₁Size relevant.Theoretical and fluid knowledge is worked as β according to blower fan ₁Near α, air flow inlet impacts more little, works as β more ₁During=α, air flow inlet impacts minimum, and this angle is best inlet angle.For technology and the convenience of calculating, blade outlet angle is chosen usually with inlet angle and is equated, i.e. β ₂=β ₁, general β ₂=25 ⁰～45 ⁰Be advisable;

B) molded lines of fan blade and definite its size

Straight Qu Chengdu during vane type line major decision blade installation.Molded lines commonly used has straight line, circular arc line and log spiral.Owing to select into, exit angle and equate that molded lines can not adopt orthoscopic; The log spiral more complicated, technology difficulty is big, is difficult to machine concerning producer.In order to take into account performance and technology, it is good in order to take into account performance and technology that the blade line style adopts circular arc line, and the blade line style adopts circular arc line.According to Fig. 4 fan blade shape and how much passes, be calculated as follows blade circular arc respective radius R _n, central angle alpha _n, α _nPairing chord length mn:

$\left\{\begin{array}{c}\tan \frac{{\mathrm{\&alpha;}}_{\mathrm{<figure-callout\; id="2"\; label="n"\; filenames="A200710303762E00142.png"\; state="\{\{state\}\}">n</figure-callout>}}}{2}=\frac{D_{f2}-D_{f1}}{{\mathrm{<figure-callout\; id="2"\; label="D\; f"\; filenames="A200710303762E00142.png"\; state="\{\{state\}\}">D</figure-callout>}}_f+D_{f1}}c\tan {\mathrm{\&beta;}}_1\\ \stackrel{\&OverBar;}{\mathrm{mn}}=\sqrt{{\left(\frac{{\mathrm{<figure-callout\; id="2"\; label="D\; f"\; filenames="A200710303762E00142.png"\; state="\{\{state\}\}">D</figure-callout>}}_f}{2}\right)}^2+{\left(\frac{{\mathrm{<figure-callout\; id="1"\; label="D\; f"\; filenames="A200710303762E00141.png,A200710303762E00142.png"\; state="\{\{state\}\}">D</figure-callout>}}_f}{2}\right)}^2-2\&CenterDot;\frac{{\mathrm{<figure-callout\; id="2"\; label="D\; f"\; filenames="A200710303762E00142.png"\; state="\{\{state\}\}">D</figure-callout>}}_f}{2}\&CenterDot;\frac{{\mathrm{<figure-callout\; id="1"\; label="D\; f"\; filenames="A200710303762E00141.png,A200710303762E00142.png"\; state="\{\{state\}\}">D</figure-callout>}}_f}{2}\cos {\mathrm{\&alpha;}}_n}\\ R_n=\frac{\stackrel{\&OverBar;}{\mathrm{mn}}}{2\sin \left(\frac{{\mathrm{\&alpha;}}_n}{2}\right)}\end{array}\right.---\left(5\right)$

Then the blade arc length is that the blade physical length is l _n=R _nα _n

C) blade top

When gas entered blade, the air velocity at close shroud place was obviously greater than close hub disk place.For the blade at no top, this will cause the inlet air flow angle obviously to diminish along the Width that enters blade, form bigger shock at entry, cause windage loss.Blade increases top for this reason, shown in Fig. 5 dash area, can reduce along the intensity of variation of blade inlet width flow angle, reduces the impact of blade inlet, thereby improves the fan aeroperformance.Increase blade top and improve aeroperformance.With the internal diameter size D that determines _F1Be standard, determine the size of top part.Make that top part maximum gauge is D _1max, minimum diameter is D _1min, average diameter is D _1m, then

$\left\{\begin{array}{c}{\mathrm{<figure-callout\; id="1"\; label="D"\; filenames="A200710303762E00141.png,A200710303762E00142.png"\; state="\{\{state\}\}">D</figure-callout>}}_{1\max }=(1.01~1.05)D_{f1}\\ {\mathrm{<figure-callout\; id="1"\; label="D"\; filenames="A200710303762E00141.png,A200710303762E00142.png"\; state="\{\{state\}\}">D</figure-callout>}}_{1\min }=(0.8~0.98)D_{f1}\\ D_{1m}=\frac{{\mathrm{<figure-callout\; id="1"\; label="D"\; filenames="A200710303762E00141.png,A200710303762E00142.png"\; state="\{\{state\}\}">D</figure-callout>}}_{1\max }+{\mathrm{<figure-callout\; id="1"\; label="D"\; filenames="A200710303762E00141.png,A200710303762E00142.png"\; state="\{\{state\}\}">D</figure-callout>}}_{1\min }}{2}\end{array}\right.---\left(6\right)$

6. the selected condition that will guarantee fan performance, noise and rigidity simultaneously of fan blade number N.

A) if by hypsokinesis centrifugal fan blade computing formula, number of blades should be:

$N=8.5\frac{\sin {\mathrm{\&beta;}}_2}{1-{\mathrm{<figure-callout\; id="1"\; label="D\; f"\; filenames="A200710303762E00141.png,A200710303762E00142.png"\; state="\{\{state\}\}">D</figure-callout>}}_f/D_{f2}}---\left(7\right)$

B) fan performance is best considers that the fan blade number should be if press:

$N=\mathrm{\&tau;\&pi;}\frac{{\mathrm{<figure-callout\; id="2"\; label="D\; f"\; filenames="A200710303762E00142.png"\; state="\{\{state\}\}">D</figure-callout>}}_f+D_{f1}}{D_{f2}-{\mathrm{<figure-callout\; id="1"\; label="D\; f"\; filenames="A200710303762E00141.png,A200710303762E00142.png"\; state="\{\{state\}\}">D</figure-callout>}}_f}\sin {\mathrm{\&beta;}}_b---\left(8\right)$

Wherein, ${\mathrm{\&beta;}}_b=\frac{{\mathrm{\&beta;}}_1+{\mathrm{\&beta;}}_2}{2},$ τ is a leaf grating density, and τ=0.5+1.7sin β ₂

C) if press rigidity condition, when promptly blade height should be not less than the blade gap distance at blade centre-height place, number of blades should satisfy:

$(\mathrm{\&pi;}\frac{{\mathrm{<figure-callout\; id="2"\; label="D\; f"\; filenames="A200710303762E00142.png"\; state="\{\{state\}\}">D</figure-callout>}}_f+{\mathrm{<figure-callout\; id="1"\; label="D\; f"\; filenames="A200710303762E00141.png,A200710303762E00142.png"\; state="\{\{state\}\}">D</figure-callout>}}_f}{2N}-g)\&le;\frac{D_{f2}-{\mathrm{<figure-callout\; id="1"\; label="D\; f"\; filenames="A200710303762E00141.png,A200710303762E00142.png"\; state="\{\{state\}\}">D</figure-callout>}}_f}{2}---\left(9\right)$

Wherein, g is a vane thickness, is generally g=5～10mm.

Determine the scope that number of blades is chosen according to formula (7)～(9).

There is certain adjustable range in the size that obtains according to above-mentioned requirements, in fact gets the size value that is fit to processing man-hour and gets final product adding.

Claims (1)

1, the method for designing of the highly efficient rear incline centrifugal type cooling external fan of high-voltage asynchronous motor is characterized in that in computer specifically realizing according to the following steps successively:

Step (1). calculate according to the following steps and use required air quantity Q and the blast H of the centrifugal cooling external fan of hypsokinesis rear motor cooling instead:

Step (1.1) is used hypsokinesis centrifugal fan rear motor total losses instead and is $P_{\mathrm{loss}}^{\&prime;}=P_{\mathrm{loss}}-\mathrm{\&Delta;}{P}_f,$ Wherein, P _LossTotal losses when adopting centrifugal fan radially originally, Δ P _fBe the fan loss that designing requirement descends, P _LossAnd Δ P _fBe all datum;

Step (1.2) is calculated as follows required air quantity Q and the blast H of motor cooling:

$\left\{\begin{array}{c}Q=\frac{\mathrm{\&Sigma;}{P}_{\mathrm{loss}}^{`}}{c_a{\mathrm{\&theta;}}_a}\\ H=Z{Q}^2\end{array}\right.$

Wherein, θ _aThe temperature rise of motor air, c _aAir specific heat is set-point, and Z is the resistance of exogenous wind transportation work style;

Step (2). determine the basic size of fan by following formula and constraints: inside diameter D _F1, outer diameter D _F2, width of blade b:

Step (2.1) is determined D according to following formula _F1With D _F2Relation:

$\left\{\begin{array}{c}\stackrel{\&OverBar;}{l}=\frac{D_{f2}-D_{f1}}{2D_{f2}}=0.15~0.20\\ D_{f2}=(1.1~1.5)D_{f1}\end{array}\right.$

Wherein, l is the fan blade relative length;

Step (2.2) is determined D according to step (2.1) and following formula _F1With D _F2:

$H=\frac{H}{H_0}\&times;{\mathrm{\&eta;}}_0\mathrm{\&rho;}{\mathrm{\&pi;}}^2{\left(\frac{n}{60}\right)}^2(D_{f2}^2-D_{f1}^2)$

Wherein, n is the motor rated speed, and ρ is an atmospheric density, η ₀Gas efficiency of movement during for the fan zero load, H/H ₀For being blast and the ratio of unloaded blast, get fan efficiency eta on the fan external characteristic curve _F,The value of maximum point place correspondence;

Step (2.3), determine fan blade width b according to following formula:

$Q=\frac{1}{2}\&CenterDot;\left({\mathrm{\&delta;}}_0\mathrm{\&pi;}{D}_{f2}n\right)\&CenterDot;\left(\mathrm{\&lambda;\&pi;}{D}_{f2}b\right)$

Wherein, δ ₀Be the air quantity correction factor, λ is given value for considering the real area coefficient of vane thickness loss;

Step (2.4) is judged D _F1Whether satisfy with b:

$\mathrm{\&pi;}{D}_{f1}b>1.5\&times;\left(\frac{1}{4}\mathrm{\&pi;}{D}_{f1}^2\right),$

Satisfy, carry out next step; Do not satisfy, return step (2.2);

Step (3). the size value according to step (2) obtains, recomputate air quantity and blast, make that new air quantity and blast are Q ' and H ', and judge whether to satisfy:

$\left\{\begin{array}{c}\left|\frac{Q\&prime;-Q}{Q}\right|\&le;1\%\\ \left|\frac{H\&prime;-H}{H}\right|\&le;5\%\\ H\&prime;>H\end{array}\right.,$

Satisfy, carry out next step; Do not satisfy, return the size that step (2.1) redefines fan;

Step (4). calculate fan loss P _f=Q ' H '/η _f, η _f=0.25～0.30;

Step (5). determine the fan blade shape according to following steps:

Step (5.1) is set inlet blade angle β ₁Equal outlet blade angle β ₂, β ₂=25 ⁰～45 ⁰

Step (5.2) is calculated as follows blade circular arc respective radius R _n, central angle alpha _n, α _nPairing chord length mn:

$\left\{\begin{array}{c}\tan \frac{{\mathrm{\&alpha;}}_n}{2}=\frac{D_{f2}-D_{f1}}{D_{f2}+D_{f1}}c\tan {\mathrm{\&beta;}}_1\\ \stackrel{\&OverBar;}{\mathrm{mn}}=\sqrt{{\left(\frac{D_{f2}}{2}\right)}^2+{\left(\frac{D_{f1}}{2}\right)}^2-2\&CenterDot;\frac{D_{f2}}{2}\&CenterDot;\frac{D_{f1}}{2}\cos {\mathrm{\&alpha;}}_n}\\ R_n=\frac{\stackrel{\&OverBar;}{\mathrm{mn}}}{2\sin \left(\frac{{\mathrm{\&alpha;}}_n}{2}\right)}\end{array}\right.$

Then the blade arc length is that the blade physical length is l _n=R _nα _n

Step (5.3), the internal diameter size D definite according to step (3) _F1The maximum gauge that calculates blade increase top part is D _1max, minimum diameter is D _1min, average diameter is D _1m:

$\left\{\begin{array}{c}{D}_{1\max }=(1.01~1.05)D_{f1}\\ D_{1\min }=(0.8~0.98)D_{f1}\\ D_{1m}=\frac{D_{1\max }+D_{1\min }}{2}\end{array}\right.$

Step (6). definite according to the following steps fan blade is counted N:

Step (6.1), by hypsokinesis centrifugal fan blade computing formula, number of blades N:

$N=8.5\frac{\sin {\mathrm{\&beta;}}_2}{1-D_{f1}/D_{f2}}$

Step (6.2), calculate number of blades N when pressing fan performance the best:

$N=\mathrm{\&tau;\&pi;}\frac{D_{f2}+D_{f1}}{D_{f2}-D_{f1}}\sin {\mathrm{\&beta;}}_b$

Wherein, ${\mathrm{\&beta;}}_b=\frac{{\mathrm{\&beta;}}_1+{\mathrm{\&beta;}}_2}{2},$ τ is a leaf grating density, and τ=0.5+1.7sin β ₂

Step (6.3) satisfies rigidity condition, when promptly blade height should be not less than the blade gap distance at blade centre-height place, and number of blades N then:

$(\mathrm{\&pi;}\frac{D_{f2}+D_{f1}}{2N}-g)\&le;\frac{D_{f2}-D_{f1}}{2}$

Wherein, g is a vane thickness, g=5～10mm;

Step (6.4) according to the blade requirement of step (6.1)～(6.3), is determined the scope that number of blades is chosen.

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