In view of the boiler fan design technologies and solutions

Summary of fan.The fan is one of commonly used equipment factories,enterprises,especially the

application of the fan is more extensive.Boiler fan,smoke prevention and dust control,ventilation cooling fan,is inseparable from the www.Jnmwfj.net in power station,mine,chemical industry and

environmental protection engineering,fan is an important and indispensable equipment,correctly grasp the design of the fan,it is important for guaranteeing the normal economic operation of the fan.The boiler fan design scheme selection Suction fan design is usually given conditions there are

cotton,volume flow,total pressure,working medium and the density of medium temperature (or work),and sometimes the structure requirements and special requirements,etc.For boiler fan design requirements are:to meet the required flow rate and pressure point should be near the highest efficiency point;The highest efficiency value as far as possible a few bigger,flat efficiency curve.Pressure curve of stability interval width;Fan has simple structure,good manufacturability;Easy to select materials and accessories;Have enough strength,stiffness,induction motor sales work safety can be *;Stable running,low

noise;Good regulation performance,strong adaptability to work;Sizes as small as possible,light

weight;Operation and maintenance convenience,easy disassembling transportation.

However,all at the same time satisfy the above requirements,the general is impossible.In the aerodynamic performance and structure (strength,process) often also have contradiction between,usually resolved to seize the main contradiction.This would require the designer to choose reasonable design scheme,in order to solve the main contradiction.Such as:To different requirements,with the purpose of the fan is different also,such as public buildings used by the fan ventilation is generally used to make use of,generally the most important requirement is low noise,wing has the characteristics of the boiler fan;Requires the boiler fan in the heavy traffic are usually double suction type;For some high pressure boiler fan,low specific speed,the leakage loss ratio is generally larger.When the boiler fan design several important scheme:(1) leaf blade type of rational choice:common fan under a certain speed,backward t smaller pressure coefficient of the impeller,the impeller diameter is larger,and its efficiency is higher;The former,by contrast to 12 volt motorthe impeller.(2) the selection of fan drive,such as driving mode for A,D,F,the fan

rotation speed is the same as the motor speed.And B,C,E three are variable,to choose the design

flexible fan speed.General,widely used for small fan and motor to drive straight league A,,for large

fan,belt drive is unwell,sometimes by transmission way D,the F.For high temperature,dusty

conditions,consider the protection of motor,bearing transmission way and the cooling problem.(3) the

overall dimensions of choice:the snail's shell overall dimensions should be as small as

possible.Fan,the ratio of revolution can be used to shorten the volute,standard is generally selected to lower than revolution fan volute.Sometimes in order to reduce volute size,can choose speed is greater than the fan speed for the inlet volute outlet USES the outlet diffuser at this time in order

to improve its static pressure value.

(4) leaf blade outlet Angle selected:blade outlet Angle is designed first to select one of the main geometric parameters.To facilitate the application,we put the blade classified as:strong curved blade (pump),after bending arc blade,straight blade and curved wing shape after bending after blade;Radial outlet blade,radial straight blade;Before the top curved blade,curved blade (wing).Table 1 lists the boiler fan in the blade type of blade outlet Angle range of roughly.(5) leaf number choice:in the boiler fan,increase of the impeller blade number can improve impeller pressure theory,because it can reduce the influence of relative vortex (i.e.,increase the K value).However,the increase of blade number,will increase the friction loss of impeller passage,this loss will reduce the actual pressure of fan and increase energy consumption.Therefore,for each kind of impeller,there is a best leaf number.Specific to determine how many leaf number,sometimes need to according to the designer's experience.According to low rpm motors the current application situation in China,recommend the choice scope of leaf number in table 2.(6) total pressure coefficient t selected:when designing boiler fan,the actual stress is given in advance.Then need to select t total pressure coefficient,total pressure coefficient is roughly options may refer to table 3.(7) the determination of the main geometry size centrifugal impeller import and export:impeller main size is shown in figure 1.The impeller is the only element of fan is passed to the gas energy,therefore,its design has great influence for fan;Can correctly determine the impeller of the main structure,performance parameters of fan plays a key role.It contains the key technologies of the boiler fan design,the design of the blade.

And the design of blade is the most key link is how to determine the blade outlet Angle beta 2 a.The design of the key technologies of analysis When designing boiler fan,the key is to master good determination of impeller blade outlet Angle beta 2 a.According to different blade outlet Angle beta 2 a,the blade can be divided into three types namely the curved blade (beta 2 a < 90 ℃),radial outlet blade gasoline generator spare parts (beta 2 a = 90 ℃ ) and former curved blade (beta 2 a > 90 ℃).Three types of impeller blades,are applied in the design of fan.Before the characteristics of the curved blade impeller are small size weight,cheap,and then curved blade impeller can improve the efficiency,save energy,so in the modern production of the fan,especially the great power of large fan most after using curved blade.Before modern curved blade fan efficiency,than the old product has significantly improved,therefore,on the occasion of small flow high pressure or low pressure big traffic situations are still widely used.Radial outlet blade is not commonly used in our country,in some wear and corrosion resistance of the fan,the commonly used radial export straight blade.Boiler fan impeller design must also take into account the specific speed and blade type has certain relationships (table 4),so the blade outlet Angle is determined at the same time,must consider three kinds of blade type influence on stress,radial size and efficiency,after comprehensive table 1 and table 4.Correctly identified the boiler fan impeller blade outlet Angle beta 2 a will determine the other main geometry size for impeller has laid a solid foundation,thus the performance of the boiler fan plays a key role.