Transactions of the Korean Society of Mechanical Engineers B (대한기계학회논문집B)

The Korean Society of Mechanical Engineers (대한기계학회)
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Flow Characteristics of the Boundary Layer Developing over a Turbine Blade Suction Surface

터빈 동익 흡입면에서 발달하는 경계층의 유동특성

  • Chang, Sung Il (Department of Mechanical Engineering, Kumoh National Institute of Technology) ;
  • Lee, Sang Woo (Department of Mechanical Engineering, Kumoh National Institute of Technology)
  • 장성일 (금오공과대학교 기계공학과) ;
  • 이상우 (금오공과대학교 기계공학과)
  • Received : 2015.04.08
  • Accepted : 2015.08.21
  • Published : 2015.10.01
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Abstract

The boundary layer developing over the suction surface of a first-stage turbine blade for power generation has been investigated in this study. For three locations selected in the region where local thermal load changes dramatically, mean velocity, turbulence intensity, and one-dimensional energy spectrum are measured with a hot-wire anemometer. The results show that the suction-surface boundary layer suffers a transition from a laminar flow to a turbulent one. This transition is confirmed to be a "separated-flow transition", which usually occurs in the shear layer over a separation bubble. The local minimum thermal load on the suction surface is found at the initiation point of the transition, whereas the local maximum thermal load is observed at the location of very high near-wall turbulence intensity after the transition process. Frequency characteristics of turbulent kinetic energy before and after the transition are understood clearly from the energy spectrum data.

본 연구에서는 발전용 터빈 제 1 단 동익 흡입면에서 발달하는 경계층유동에 대하여 체계적으로 연구하였다. 이를 위해 흡입면에서 열부하가 급격하게 변화하는 대표적인 영역에 대하여, 경계층의 평균 유속, 난류강도, 에너지스펙트럼 등을 측정하였다. 그 결과 흡입면 경계층유동이 층류에서 난류 경계층으로 천이됨을 확인할 수 있었고, 이 천이경로는 박리버블의 전단층에서 주로 발생하는 박리유동 천이로 확인되었다. 흡입면에서 열부하의 최소값이 존재하는 곳은 흡입면 경계층유동의 천이가 시작되는 위치에 해당하며, 열부하가 최대인 곳은 박리유동 천이가 모두 마무리되어 벽근처에 강력한 난류유동이 존재하는 곳과 일치하였다. 에너지스펙트럼의 측정을 통하여, 흡입면 경계층의 박리유동 천이 전후에 나타나는 난류운동에너지의 주파수 특성을 자세히 파악할 수 있었다.

Keywords

References

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