In order to maximize the improvement effect on axial compressor aerodynamic performance by the circumferential groove casing treatment (CGCT), it is necessary to clarify its influences on the flow behavior which reduces the stable operating flow range. In this study, as a first step to study the CGCT, flows in a linear compressor cascade with and without a groove installed at mid-chord were analyzed numerically. The computed results clarified the following phenomena. The groove reduces a distance between a tip leakage vortex (TLV) and a blade suction surface by a decrease of blade loading around the groove and a flowing of flow near the blade pressure surface into the groove. The groove reduces a loss due to the TLV, but a loss generation in the entire cascade passage is almost the same as that in the smooth endwall case because of an additional loss generation by the groove.

The increase of turbine blade loading by increasing turning angle is one of the effective methods to improve the aerodynamic performance of gas turbine, which makes it possible to reduce the number of blades and stages. As a consequence, the decreases of both the weights and the costs for manufacturing and for maintenance can be realized. However, the secondary losses caused by the passage and the tip leakage vortices are inevitably increased due to the increase of the pitchwise pressure gradient.

This study aims to investigate the effects of tip clearance size on the aerodynamic performance of an ultra-highly loaded turbine cascade (UHLTC) with the turning angle of 160 degrees by using a small sized wind tunnel for annular cascades. The experimental results showed that the decrease of the size of tip clearance resulted in the enhancement of the turbine efficiency due to the reduction of aerodynamic loss.

This paper discusses the effectiveness of a backward tip rake (BTR) for a marine propeller on a propeller open water efficiency, cavitation erosion and a pressure fluctuation based on the results of RANS analysis, model tests and actual ship tests.

The BTR was applied to a small blade area propeller which was expected the pressure fluctuations increase. RANS analysis and model test results showed that there was no loss in the propeller open water efficiency, and no serious risk in cavitation erosion and pressure vibrations. Then actual ship test results showed that hull vibration speed was kept within the permissible range and there was no cavitation erosion indication. In addition, when not adopting the BTR, RANS analysis results indicated that the pressure fluctuations increased comparing to that of BTR propellers. The effectiveness of BTR propellers was confirmed from these results.