Axial Flow Fan Design Parameter Affecting the Performance

Axial flow fans are employed in heat exchangers and other engineering systems where the flow path around the fan becomes like a duct. The flow takes place along the axis of rotation of the rotor. The flow is essentially symmetrical to the axis. The design calculations are performed with presumption of flow through cascade of blade and it is the main governing factor of the design too. In this paper procedural calculation for an axial flow fan with profiled blade are presented. Calculations are tabulated for different parameter of radius and angles. On profiling, the increase of outlet angle has been shown which gives ultimate angle opening. The small corrections are therefore obtained. Different parameters used in the design are tabulated to get the calculation more accurately.


INTRODUCTION
Axial Fan designers are frequently faced with the problem of designing high-efficiency fans at a given flow rate and for a given pressure duty.Design techniques are typically based on engineering experience, and may involve much trial and error before an acceptable design is found.
An axial flow fan stage consists of a rotor made up a number of blade fitted to the hub.When it is rotated by an electric motor or any other drive, a flow is established through the rotor.The action of the rotor cause in increase in the stagnation pressure of air or gas across it.A cylinderalcasing encloses the rotor.It receives the flow through well shaped converging passage (nozzle) and discharges it through a diverging passage or diffuser.
The number of blade in rotor varies two to fifty.As in axial fan, the flow is generally in the axial direction, Guide blade to recover statics pressure from the swiral downstream of the rotor.
Fan engineers are frequently faced with the problem of designing high-efficiency fans at a given flow rate and for a given pressure duty.Design techniques are typically based on engineering experience, and may involve much trial and error before an acceptable design is found.

CONCLUSION
In the present paper design procedure for an axial flow fan applicable in heat exchangers and other engineering systems has been presented.The design calculations are performed with presumption of flow through cascade of blade and it is the main governing factor of the design too.The profiled blade theory is used for designing.
Calculations are tabulated for different parameter of radius and angles.On profiling, the increase of outlet angle has been shown which gives ultimate angle opening.The small corrections are therefore obtained.In this paper important design parameters with particular values as obtained through calculation are listed.The data of important design parameters can be used for design optimization and energy conservation in application of axial flow fans.

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Equating both value Ψ and ϕ Then Find Value σ=2.16 & δ=1.28After the value speed coefficient σ and diameter coefficient δ is calculated, specific diameter r is read from the graph given in Figure by Eck Specific speed coefficient We take a formula d 2 =795 mm ,& d 1 = 795 .28= 225 mm, η=73% The meridional speed is obtained from c m = V/(η/4) c m = 15.122m/sec u 2 = πd 2 n / 60 u 2 = 60.73 m/sec ϕ= c m / u 2 ϕ = For t/ l, the best value of which range selects the first value are being at the tip of the blade.Thus we have take number of blade Z =9.Z= (4π/ 1.5) [sin β 2 /{1-(r 1 /r 2 )}] Then find value β 2 = 50.54°≈ 50°T hen we take fig.blade pitch according to Zweifel by ECK Take according to Zwifel β 2 = 30°T hen we obtain value s/ l = 0.66 by fig.effect of Tip clearance of Weining Draw Velocity triangle c m =ω 2 sin β 2 ω 2 = 19.74m/sec Then we obtain value of ω 2 and u= ω 2 cos β 2 Then we obtain value of u =12.68 m/s General relationship angle cot β ∞ = ½ (cot