Question

a twelve-bladed axial flow fan has a hydraulic efficiency of 0.92, mean radius of 0.93m and rotates at 450rpm. air enters the blades axially at a speed of 40m/s and the head developed across the blades is 35m of air. if the cord length at the mean radius is 0.33m, find the blade angles at inlet and outlet if the blades may be considered to act as isolated aero foils. if the blades are aero foils with the following characteristics, find also the angle of incidence of the blades and the blade stagger angle. all calculations are to be carried out at the mean radius

angle of incidence degrees	-4	-2	0	4	8	12
lift coefficient	-0.18	-0.02	-0.13	0.46	0.77	1.025

   

Answer 1

hydraulic efficiency of axial flow = 0.92

Mean radius of axial flow = 0.93

2. Nousーリーテて u43.83 ms lH H-35m 0-92 J 0:92X 43-83

hx243-83-8-51 π χ 1.86 2 Wm2 드 402 tr(35.32 ±43:83)121 2 H U 3512 x g: SL 5 ms 万6-26 446

845.3 о. 4 Btom -42:38 L (40/4. '云 -3.8土45-3. B2 48:55