• 대한기계학회논문집B
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• 제27권3호
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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.

• 한국추진공학회지
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• 제12권2호
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• pp.24-32
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• 2008

마하 1.92 초음속 유동 내에서 평판, 작은 공동, 큰 공동을 사용하여 운동량비(J)에 따른 연료 혼합 실험을 수행하였다. 공동 후면 경사부는 연료의 침투거리를 급격히 증가시키며, 경사부에서 형성되는 이차원 충격파는 후류부의 충격파 구조와 혼합층에 주요한 영향을 미친다. 운동량비가 증가함에 따라(J = 0.9, 1.7, 3.4) 연료의 침투거리가 증가하지만, 후류부에서는 운동량비가 증가하더라도 연료 침투거리는 특정 지점 이상 증가하지 않았다. 큰 공동의 경우 다른 모델에 비해 좋은 혼합 효율을 보이지만 압력 손실 또한 증가하는 경향을 보인다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집B
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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.