Transactions of the Korean Society of Mechanical Engineers A (대한기계학회논문집A)

The Korean Society of Mechanical Engineers (대한기계학회)
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Identification of Frequency-Dependent Dynamic Characteristics of a Bump Structure for Gas-Foil Bearings via 1-DOF Shaker Tests Under Air Pressurization

가스 포일 베어링 범프 구조의 1 자유도 가진/가압 실험을 통한 주파수 의존 동특성 규명

  • Sim, Kyuho (Dept. of Mechanical System Design Engineering, Seoul Nat'l Univ. of Sci. & Tech.) ;
  • Park, Jisu (Dept. of Mechanical System Design Engineering, Seoul Nat'l Univ. of Sci. & Tech.) ;
  • Lee, Sanghun (Dept. of Mechanical System Design Engineering, Seoul Nat'l Univ. of Sci. & Tech.)
  • 심규호 (서울과학기술대학교 기계시스템디자인공학과) ;
  • 박지수 (서울과학기술대학교 기계시스템디자인공학과) ;
  • 이상훈 (서울과학기술대학교 기계시스템디자인공학과)
  • Received : 2015.06.11
  • Accepted : 2015.07.12
  • Published : 2015.10.01
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Abstract

Recently, the importance of rotordynamic stability has been increased because of the tendency to employ ultra-high speeds in rotating machinery. In particular, the dynamic characteristics of gas bearings for high-speed rotating machinery need to be identified at various excitation frequencies to predict the rotor's behavior. In this study, we perform dynamic loading tests for gas-foil bearings (GFBs) to determine the bump foil structure and an air-film combined bump-foil structure for varying excitation frequencies. We calculate the dynamic characteristics from the measured force and displacement data. The air film is generated by a pressurized air supply. Based on the results, the stiffness coefficients of the bump structure and the air-film combined bump structure increased, while the damping coefficients decreased at increasing excitation frequencies. Further, the stiffness and damping coefficients of the air-film combined structure show lower values than those of the bump structure. Consequently, we identify the frequency-dependent dynamic characteristics of the bump structure and the effect of gas film on the dynamic characteristics of GFBs. Furthermore, to reveal the effectiveness of the proposed method, we perform experiments and discuss two methods of extracting the dynamic characteristics from the measured data.

최근 회전 시스템의 고속화 경향에 따라 회전체 동역학적 안정성의 중요성이 부각되었다. 고속회전 시스템에 적용되는 가스베어링의 동특성을 규명하는 것은 회전체의 거동을 예측하는데 상당히 중요하다. 본 연구에서는 대표적인 가스베어링인 가스포일베어링의 범프 구조에 대하여 가진실험을 수행하고 가진 주파수에 따른 동특성을 측정하였다. 실험 결과, 범프 구조의 강성은 주파수에 따라 증가하였고 감쇠는 감소하였다. 또한, 가압 조건에서의 동특성은 범프 구조의 동특성 보다 낮은 값을 가졌다. 본 실험을 통해 범프 구조의 주파수 의존 동특성의 경향을 파악하였으며 가스포일베어링의 동특성에 윤활막이 미치는 영향에 대해 확인하였다. 또한 두 가지 동특성 계산 방법을 제시하여 실험결과를 통해 효과 적인 동특성 계산 방법에 대해 비교 고찰하고 범프 구조와 윤활막의 동특성을 비교 하였다.

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References

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