Flow Loss Reduction by Applying Wide Chord Design -Examination of Mid-Flow loss outside Boundary Layer

Abstract

Generally the boundary layer loss is recognized as the main loss in the cascade flow in actual turbomachinery. Therefore, the loss in the other area outside the boundary layer which we call a mid-flow was often neglected. However, in the present paper, the mid-flow loss evaluation is conducted again to verify if it can really be neglected with all conditions. As a result, it is surely verified that the mid-flow loss can be negligible with higher pressure conditions. However, with lower pressure conditions, it is verified that the mid-flow loss can occupy several tens of % of the total loss; therefore, it cannot be neglected and it is effective to reduce the total loss by reducing the mid-flow loss with these conditions. Moreover, it is verified that the mid-flow loss has the characteristic in which it is inversely proportional to the chord for the identical solidity cascade flow; therefore, it is verified that wide chord cascade can reduce the mid-flow loss. Hence, the wide chord cascade can reduce the total loss in actual turbomachinery.