APPROXIMATE EFFECT OF LEADING-EDGE THICKNESS, INCIDENCE ANGLE, AND INLET MACH NUMBER ON INLET LOSSES FOR HIGH-SOLIDITY CASCADES OF LOW CAMBERED BLADES

摘要

An approximate, theoretical analysis was made of the inlet or in¬duction losses due to subsonic flow into a high-solidity cascade of finite thickness blades at incidence angle. The results, which are presented in a series of figures, indicate that the losses, although they make up only part of the experimental blade loss factor commonly presented from rotating tests, can became considerable for such large deviations from design incidence as may be encountered, for example, at compressor off-design operating conditions.nThe analysis indicates that for subsonic flow the induction loss portion of the blade loss factor can be reduced or eliminated through increase of blade leading-edge radius. The results for finite thick¬nesses are considered to be of very questionable accuracy for both very low incidence angles and near-sonic free-stream velocities because the assumption of zero blade leading-edge pressure utilized in the computa¬tions is violated under such conditions.nA pronounced effect of upstream flow angle on the Shape and magni¬tude of the loss factor curve is observed, and the desirability of avoiding large blade stagger angles when considerable range in incidence angle is required is indicated.nThe equations utilized constitute the usual shock equations when applied to a supersonic, zero thickness inlet at zero incidence. Some limited results are presented for supersonic flow where the subsonic computations were extended past Mach 1. Further investigation is neces¬sary to establish the relation between losses computed in this manner and those associated with the complex wave patterns postulated for super¬sonic cascades with nonzero incidence.