The effect of a hub fillet radius on a non-axisymmetric endwall contour

摘要

Current manufacturing processes of turbine blades makes a hub fillet radius a necessity; however the designer has control as to the size of the fillet. It has been found by some researchers that the fillet radius has an impact the loss generation in the blade row, with a uniform fillet of 16% axial chord increasing loss generation by 10%. Endwall contouring on the other hand has been shown to reduce losses, but very little research is available in the open literature that details how the performance of the non-axisymmetric endwall is affected by the fillet radius. A numerical investigation was thus undertaken to assess how the effectiveness of a previously investigated generic endwall contour in a rotating single stage turbine is altered by fillet radii of different sizes. Constant fillet radii of 0 mm to 3 mm (0% to 7% chord) were investigated for both an annular and a contoured rotor and compared. It was found that the annular rotor showed more variation in the rotor exit flow field than the contoured rotor. The contoured rotor exit flow field exhibited largely negligible changes. The annular rotor showed an increase in isentropic stage efficiency with increase in fillet radius, while the contoured rotor showed a decrease, such that the 3 mm fillet resulted in the annular rotor being more efficient than the contoured rotor.