• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.3
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• pp.389-397
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• 2003

Effect of tip leakage flow on through flow and performance of a centrifugal compressor impeller was numerically studied using CFX-TASC flow. Seven different tip clearances were used to consider the influence of tip clearance on performance. Secondary flow and loss factor were evaluated to understand the loss mechanism inside the impeller due to tip leakage flow. The calculated results were circumferentially averaged along the passage and at the impeller exit for quantitative discussion. Tip clearance effect on Performance could be decomposed into inviscid and viscous components using one dimensional equation. The inviscid component is related with the specific work reduction and the viscous component is related with the additional entropy generation. Two components affected Performance equally. while efficiency drop was mainly influenced by viscous loss. Performance and efficiency drop due to tip clearance were proportional to the ratio of tip clearance to exit blade height. A simple model suggested in the present study predict performance and efficiency drop quite successfully.

• Journal of the Korean Society of Propulsion Engineers
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• v.12 no.2
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• pp.24-32
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• 2008

A non-reacting experimental study on a normal injection into a Mach 1.92 crossflow which flows over various geometries(flat plate, small cavity, large cavity) was carried out to investigate the effect of the momentum flux ratio(J). The aft ramp of the cavity advances the increase of the penetration height and the strong two-dimensional shock from recompression region mainly affects the shock structure and mixing layer at the downstream flow. As flow runs downward, the transverse penetration height increases with increasing J(J = 0.9, 1.7, 3.4). However, above some critical ratio, jet penetration height growth with increasing J is not appeared in flow-field. Large scale cavity has a good mixing efficiency but it increases the drag loss in the combustor.

• Proceedings of the KSME Conference
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• 2000.04b
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• pp.853-858
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• 2000

The working fluid from the combustor to the turbine stage of a gas turbine makes various boundary layer thickness. Since the inlet boundary layer thickness is one of the important factors that affect the turbine efficiency. It is necessary to investigate secondary flow and loss with various boundary layer thickness conditions. In the present study, the effect of various inlet boundary layer thickness on secondary flow and loss and the proper height of the boundary layer fences for various boundary layer thickness were investigated. Measurements of secondary flow velocity and total pressure loss within and downstream of the passage were taken under 5 boundary layer thickness conditions, 16, 36, 52, 69, 110mm. It was found that total pressure loss and secondary flow areas were increased with increase of thickness but they were maintained almost at the same position. At the fellowing research about the boundary layer fences, 1/6, 1/3, 1/2 of each inlet boundary layer thickness and 12mm were used as the fence heights. As a result, it was observed that the proper height of the fences was generally constant since the passage vortex remained almost at the same position. Therefore once the geometry of a cascade is decided, the location of the Passage vortex and the proper fence height are appeared to be determined at the same time. When the inlet boundary layer thickness is relatively small, the loss caused by the proper fence becomes bigger than endwall loss so that it dominates secondary loss. In these cases the proper fence hight is decided not by the cascade geometry but by the inlet boundary layer thickness as previous investigations.