Page 111 - Fluid Mechanics and Thermodynamics of Turbomachinery

92 Fluid Mechanics, Thermodynamics of Turbomachinery
(i) pressure rise;
(ii) diffuser efficiency;
(iii) drag and lift coefficients.
7 (a) A set of circular arc fan blades, camber D 8 deg, are to be tested in a cascade wind
tunnel at a space/chord ratio, s/l D 1.5, with a stagger angle D 68 deg. Using McKenzie’s
method of correlation and assuming optimum conditions at an axial velocity ratio of unity,
obtain values for the air inlet and outlet angles.
(b) Assuming the values of the derived air angles are correct and that the cascade has an
effective lift/drag ratio of 18, determine
(i) the coefficient of lift of the blades;
(ii) the efficiency of the cascade (treating it as a diffuser).