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공기포일베어링에 지지된 마이크로가스터빈의 회전체동역학적 설계
김영철(Young-Cheol Kim),한정완(Jung-Wan Han),김경웅(Kyung-Woong Kim),김수용(Soo-Yong Kim) 한국유체기계학회 2003 유체기계 연구개발 발표회 논문집 Vol.- No.-
This paper presents a performance analysis of the 1st generation bump foil journal bearings. for the micro gas turbine TG75. Static performances such as load capacity and attitude angle are estimated by using soft elasto-hydrodynamic analysis technique, and dynamic performances such as stiffness and damping coefficients are estimated by perturbation method. Rotordynamic analysis for TG75 is performed by using the bearing analysis results. TG75 rotor has 2 horizontal and vertical directional natural modes due to the bearing stiffness characteristics. TG75 rotor will be stably operated between the 1st bending mode at 33000cpm and the 2nd bending mode at 85500cpm. Unbalance response analysis results satisfy the API vibration criteria.
김영철(Young-Cheol Kim),이동현(Dong-Hyun Lee),김경웅(Kyung-Cheol Kim) 한국유체기계학회 2005 유체기계 연구개발 발표회 논문집 Vol.- No.-
This paper presents the theoretical model to investigate the effect of Coulomb damping in the sub-structure of a foil bearing. Foil deflection is restricted by friction of bumps. Equivalent viscous damping of the bump foils is derived from the Coulomb friction. Dynamic equation of the bumps is constituted by stiffness and damping terms. This point give the difference from Heshmat's frictionless and simple compliance bump model. The fluid is modeled with the compressible Reynolds equation. A perturbation approach is used to determine the static and dynamic performance of the bearing from the coupled fluid-structural model. The analysis result shows that the static and dynamic performance is enhanced by bump friction. This analysis technique would be extended to development of a high performance bearing.
김영철(Young-Cheol Kim),이안성(An-Sung Lee),김병옥(Byung-Ok Kim),안국영(Kook-Young Ahn),이영덕(Young-Duk Lee),김경웅(Kyung-Woong Kim) 한국유체기계학회 2006 유체기계 연구개발 발표회 논문집 Vol.- No.-
This paper shows the rotordynamic characteristics of a turbo blower which is one of BOP(Balance Of Plant) for of a 1㎾ class fuel cell system for domestic use. The rotor-bearing system consists of magnetic shaft, compressor impeller, 2 oil free air foil journal bearings, and thrust bearings. Preliminary design such as critical speed map is considered. Static and dynamic characteristics of the journal and thrust AFB(Air Foil Bearing)s are estimated by the soft elasto-hydrodynamic analysis technique and the perturbation method. Also the natural frequencies, mode shapes, and unbalance response of the rotor-bearing system are analyzed.
김영철(Young-Cheol Kim),이동현(Dong-Hyun Lee),김경웅(Kyung-Woong Kim) 한국트라이볼로지학회 2007 한국트라이볼로지학회 학술대회 Vol.2007 No.11
This paper presents a experimental results for the performance evaluation of a double-bumped air foil bearing. The test results of a double-bumped AFB is compared with a single-bumped AFB at a heavily-loaded condition. The diameter of the test bearing is 50㎜, and the axial length is 50㎜. Nominal clearance of the single-bumped AFB is evaluated as 105㎛, and that of the double-bumped AFB is as 95㎛. The test of the AFBs are demonstrated at 3 test mode; the load variation mode, the speed variation mode, and start-stop mode. The single-bumped AFB demonstrated a upward load-carrying capacity of 95N and a downward load-carrying capacity of l30N at 20,000rpm. The double-bumped AFB demonstrated a upward load-carrying capacity of l70N and a downward load-carrying capacity of l70N at 20,000rpm. The single-bumped AFB demonstrated a downward lift-off speed of l6,300rpm at 105N. The double-bumped AFB demonstrated a downward lift-off speed of 15,400rpm at 105N. The start-stop test of the AFBs assure 5,000 cycle endurance life.
김영철,이동현,김경웅,Kim, Young-Cheol,Lee, Dong-Hyun,Kim, Kyung-Woong 한국트라이볼로지학회 2007 한국윤활학회지(윤활학회지) Vol.23 No.3
This paper presents a theoretical model for the analysis of double-bumped AFBs. The stiffness and damping coefficients of the double bump vary depending on the external load and its friction coefficient. In the case of a lightly loaded condition where only the upper bump contributes to deformation, the double bump is in the single active region. In the case of a heavily loaded condition where both the upper and lower bumps contribute to deformation, the double bump is in the double active region. So the double bump can be either in the single or double active region depending on vertical deflection. The equivalent stiffness and damping coefficients of the bump system are derived from the vertical and horizontal deflection of the bump, including the friction effect. A static and dynamic performance analysis is carried out by using the finite difference method and the perturbation technique. The results of the performance analysis for a double-bumped AFB are compared with those obtained for a single-bumped AFB. This paper successfully proves that a double bumped AFB has higher load capacity, stiffness, and damping than a single-bumped AFB in a heavily loaded condition.
김영철(Young-Cheol Kim),이동현(Dong-Hyun Lee),김경웅(Kyung-Woong Kim) 한국트라이볼로지학회 2009 한국윤활학회지(윤활학회지) Vol.25 No.2
This paper presents a experimental results for the performance evaluation of a double-bumped air foil bearing. The test results of a double-bumped AFB is compared with a single-bumped AFB at a heavily-loaded condition. The diameter of the test bearing is 50 ㎜, and the axial length is 50 ㎜. Nominal clearance of the single-bumped AFB is evaluated as 105 ㎛, and that of the double-bumped AFB is as 95 ㎛. The test of the AFBs are demonstrated at 3 test mode; the load variation mode, the speed variation mode, and start-stop mode. The single-bumped AFB demonstrated a upward load-carrying capacity of 95 N and a downward load-carrying capacity of 130 N at 20,000 rpm. The double-bumped AFB demonstrated a upward load-carrying capacity of 170 N and a downward load-carrying capacity of 170 N at 20,000 rpm. The single-bumped AFB demonstrated a downward lift-off speed of 16,300 rpm at 105 N. The double-bumped AFB demonstrated a downward lift-off speed of 15,400 rpm at 105 N. The start-stop test of the AFBs assure 5,000 cycle endurance life. The test results are compared with the theoretical calculation results. The test and theorectical results show thata double-bump air foil bearing provides a higher load-carrying capacity, stiffness and damping than a single-bump air foil bearing in a heavily-loaded condition.
김영철(Young-Cheol Kim),이동현(Dong-Hyun Lee),김경웅(Kyung-Woong Kim) 한국트라이볼로지학회 2006 한국윤활학회지(윤활학회지) Vol.22 No.1
This paper presents the influence coefficient method to predict the deflection of bump foil precisely in the sub-structure of AFB(air foil bearing), Heshmat has introduced the simple compliance model to calculate the deflection of bump foil. But this approach can not consider the deflection of bump foil at the edge of AFB, so elasto-hydrodynamic model is insufficient to analyze in case that the eccentricity ratio is greater than 1. Peng has used the average pressure and film thickness, but this approach is not also a realistic model. Influence coefficients of a bump is calculated by finite element method, and introduced in bump deflection equations of the performance analysis of air foil bearing. The effects of the influence coefficient on the bearing performance is discussed in detail for appropriate foil design.
김영철(Young-Cheol Kim),이동현(Dong-Hyun Lee),김경웅(Kyung-Woong Kim) 한국트라이볼로지학회 2005 한국트라이볼로지학회 학술대회 Vol.2005 No.11
This paper presents the theoretical model and analysis results to investigate the effect of Coulomb damping in the sub-structure of a foil bearing. Vertical and horizontal deflection of a bunpis restricted by friction of bumps. Equivalent viscous damping of the bump foils is derived from the Coulomb friction. Dynamic equation of the bumps is constituted by stiffness and damping terms. 'The air film is modeled by the compressible Reynolds equation. A perturbation approach and finite difference numerical method is used to determine the static and dynamic performance of the bearing from the coupled fluid-structural model. 'The analysis result shows that the static and dynamic per Iornancr- is enhanced by bump friction.
김영철(Young-Cheol Kim),이동현(Dong-Hyun Lee),김경웅(Kyung-Woong Kim) 한국트라이볼로지학회 2007 한국트라이볼로지학회 학술대회 Vol.2007 No.6
This paper deals with friction effects on the performance of double-bumped AFBs. The stiffness and damping coefficients of the double bump vary depending on the external load and its friction coefficient. The double bump can be either in the single or double active region depending on vertical deflection. The equivalent stiffness and damping coefficients of the bump system are derived from the vertical and horizontal deflection of the bump, including the friction effect. A static and dynamic performance analysis is carried out by using the finite difference method and the perturbation technique. The results of the performance analysis for a double-bumped AFB are compared with those obtained for a single-bumped AFB. This paper successfully proves that a double bumped AFB has higher load capacity, stiffness, and damping than a single-bumped AFB in a heavily loaded condition.