로커-백 피벗을 갖는 틸팅 패드 저널 베어링의 회전체동역학적 성능 예측 및 기존 결과와의 비교
Rotordynamic Performance Predictions of Tilting Pad Journal Bearing with Rocker-Back Pivots and Comparison with Published Test Results
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In this paper, we predict the rotordynamic force coefficients of tilting pad journal bearings (TPJBs) with rocker-back pivots, and we compare the predictions to recently published predictions and test data. The present TPJB model considers the rocker-back pivot stiffness calculated based on the Hertzian contact-stress theory, which is nonlinear with the application of a force . For the five-pad TPJB in load-between-pad and loadon- pad configurations, the predictions show the pressure- and film-thickness distributions, the deflection and stiffness of the individual pivots, and bearing stiffness and damping coefficients. The minimum film thickness and peak pressure occur at the bottom pad on which the applied load is directed. Because of the preload, the pressure is positive even at the upper pad in the opposite direction to the applied load. The pivot deflection and stiffness are maximum at the bottom pad that receives the heaviest pressure load. The predicted stiffness coefficients increase as the static load and rotor speed increase, while the damping coefficients decrease as the rotor speed increases, but increase as the static load increases. In general, the predicted stiffness coefficients agree well with the test data. The predicted damping coefficients overestimate the test data, particularly for large static loads. In general, the current predictive model considering the pivot stiffness improves the accuracy of the rotordynamic performance compared to previously reported models.
Abstract
In this paper, we predict the rotordynamic force coefficients of tilting pad journal bearings (TPJBs) with rocker-back pivots, and we compare the predictions to recently published predictions and test data. The present TPJB model considers the rocker-back pivot stiffness calculated based on the Hertzian contact-stress theory, which is nonlinear with the application of a force . For the five-pad TPJB in load-between-pad and loadon- pad configurations, the predictions show the pressure- and film-thickness distributions, the deflection and stiffness of the individual pivots, and bearing stiffness and damping coefficients. The minimum film thickness and peak pressure occur at the bottom pad on which the applied load is directed. Because of the preload, the pressure is positive even at the upper pad in the opposite direction to the applied load. The pivot deflection and stiffness are maximum at the bottom pad that receives the heaviest pressure load. The predicted stiffness coefficients increase as the static load and rotor speed increase, while the damping coefficients decrease as the rotor speed increases, but increase as the static load increases. In general, the predicted stiffness coefficients agree well with the test data. The predicted damping coefficients overestimate the test data, particularly for large static loads. In general, the current predictive model considering the pivot stiffness improves the accuracy of the rotordynamic performance compared to previously reported models.
참고문헌 (10)
- 최태규, "피봇 강성을 고려한 틸팅 패드 저널 베어링의 해석", 한국윤활학회지, 30(2), pp.77~85 (2014), 한국윤활학회[DOI]
- Kirk, R. G., "Evaluation of Pivot Stiffness for Typical Tilting-Pad Journal Bearing Designs", ASME J. Vib. Acoust, Stress and Reliab, 110(2), pp.165~171 (1988)
- Nicholas, J. C., "Tilting Pad Journal Bearing Pivot Design for High Load Applications", Proc. 24th Turbomachinery Symposium, pp.33~47 (1995), Turbomachinery Laboratory, Texas A&M University
- Young, W. C., "Roark’s Formulas for Stress and Strain" (2001), McGraw-Hill
- Kim, T. H., "Performance Predictions of Tilting Pad Journal Bearing with Ball-Socket Pivots and Comparison to Published Test data", The KSFM Journal of Fluid Machinery
- Childs, D., "Static Performance Characteristics and Rotordynamics Coefficients for a Four-Pad Ball-in-Socket Tilting Pad Journal Bearing", J. Eng. Gas Turbines Power, 131(6), pp.062502~ (2009)
- Carter, C. R., "Measurements Versus Predictions for the Rotordynamic Characteristics of a Five-Pad Rocker-Pivot Tilting-Pad Bearing in Load-Between-Pad Configuration", J. Eng. Gas Turbines Power, 131(1), pp.012507~ (2009)
- Childs, D. W., "Rotordynamic Characteristics of a Five Pad, Rocker-Pivot, Tilting Pad Bearing in a Load-on-Pad Configuration; Comparisons to Predictions and Load-Between-Pad Results", J. Eng. Gas Turbines Power, 133(8), pp.082503~ (2011)
- 이태원, "유한 요소 해석을 통해 계산된 틸팅 패드 베어링의 피봇강성과 Hertzian 접촉 모델 해석 결과 비교", 한국윤활학회지, 30(4), pp.205~211 (2014), 한국윤활학회[DOI]
- Choi, T. G., "Analysis of Tilting Pad Journal Bearings Considering Pivot Deflections", 석사, pp.2015