A fan (see Fig. P5.86) has a bladed rotor of 12 -in. outside diameter and 5-in. inside diameter and runs at \(1725 \mathrm{rpm}\). The width of each rotor blade is \(1 \mathrm{in}\). from blade inlet to outlet. The volume flowrate is steady at \(230 \mathrm{ft}^{3} / \mathrm{min}\), and the absolute velocity of the air at blade inlet, \(V_{1}\), is purely radial. The blade discharge angle is \(30^{\circ}\) measured with respect to the tangential direction at the outside diameter of the rotor.

(a) What would be a reasonable blade inlet angle (measured with respect to the tangential direction at the inside diameter of the rotor)?

(b) Find the power required to run the fan.

Figure P5.86

Transcribed Image Text:

30% Q = 230 ft/min + 1725 rpm 12 in. 5 in. 1 in.-