| The secondary flows have been investigated in a low speed linear cascade for a family of three low-pressure turbine airfoils designed for the same inlet and outlet flow angles. The baseline airfoil of the family is representative of the midspan section of a vane in a Pratt & Whitney Aircraft (PWA) engine currently in operation. The other two airfoils, one front- and the other aft-loaded, have 25% higher loading than the baseline. All three airfoils were designed by PWA.; Measurements were made using a seven-hole pressure probe at a constant Reynolds number of 80,000 (based on the axial chord and the inlet velocity) for three values of incidence. -5°, 0° (design incidence) and +5°. The effect of freestream turbulence intensity was also investigated. Two values of turbulence intensity (1.5% and 4.0%) were examined at the design and positive incidence. An increase in the freestream turbulence levels resulted in the reduced strength of the secondary flows, and thus the losses.; For all cases examined, the front-loaded airfoil exhibited the highest secondary losses. This was expected based on previous research. The two other airfoils, the baseline and the more aft-loaded one, generated comparable losses. It was suggested that the separation bubbles present on the airfoil surfaces and their interaction with the secondary flows may have been responsible for this unexpected finding. Compared to the empirical loss predictions, a higher sensitivity to the changes in incidence was observed for the airfoils in the present measurements. |
