• Tribology and Lubricants
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• 제18권2호
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• pp.153-159
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• 2002

This paper describes a durability characteristics of an air-lubricated bump foil journal bearing for high speed turbomachinerys at room temperature. At first, lift-off test and load capacity test were performed to understand the general characteristics of an air-lubricated bump foil Journal bearing. A 52 N weighted bump foil bearing sleeve was lilted off from a rotating Journal at about 3,000 rpm, and produced a load capacity of 500 N at an operating speed of 15,000 rpm. The next was 500 cycles lift-off test with an air-lubricated bump foil journal bearing that had a molybdenum disulfide(MoS$_2$) solid lubricant coated top foil. Data from measuring bearing torque and temperature and the observation of rubbing surfAce were included in results. Therefore the results of this work will aid in proving durability of air-lubricated bump foil journal bearings.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2001년도 제34회 추계학술대회 개최
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• pp.212-219
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• 2001

This paper describes a durability characteristics of an air-lubricated bump foil journal bearing for high speed turbomachinerys at room temperature. At first, lift-off test and load capacity test were performed to understand the general characteristics of an air-lubricated bump foil journal bearing. A 52N weighted bump foil bearing sleeve was lifted off from a rotating journal at about 3,000rpm, and produced a load capacity of 500N at an operating speed of 15,000rpm. The next was 500 cycles lift-off test with an air-lubricated bump foil journal bearing that had a molybdenum disulfide(MoS$_2$) solid lubricant coated top foil. Data from measuring bearing torque and temperature and the observation of rubbing surface were included in results. Therefore the results of this work will aid in proving durability of air-lubricated bump foil journal bearings.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2009년도 추계학술대회 논문집
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• pp.791-791
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• 2009

Hybrid air-foil magnetic bearing combines two oil free bearing technologies to take advantage of the strengths of each bearing with minimizing each other weaknesses. This paper presents bending mode vibration control of a flexible shaft supported by the hybrid air-foil magnetic bearing. An experiment set-up of a flexible shaft supported by the hybrid air-foil magnetic bearing is built. In order to verify the effectiveness of the hybrid bearing, unbalance responses of the flexible shaft supported by three different bearings: air-foil, magnetic and hybrid bearings are compared. Effect of load sharing between air-foil and magnetic bearings are investigated through changing control gain and offset displacements of magnetic bearing.

• Tribology and Lubricants
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• 제22권1호
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• pp.40-46
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• 2006

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.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2001년도 추계학술대회논문집 I
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• pp.349-353
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• 2001

An air foil bearing is developed for the high speed generator. The bearing is type of multi-leaf and is stable on 60,000RPM. The vibration level is 12um(p-p) and the highest temperature level is below 100$^{\circ}C$. The dynamic parameter of air foil bearing is acquired by experimental method using exciter. The air foil bearing is also good condition at test of real generator and load condition. The condition of foil is very good after 3,000cycle start-stop test. Therefore the air foil bearing is ideal for high speed, light weight and modem turbo-machinery.

• Tribology and Lubricants
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• 제27권2호
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• pp.57-64
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• 2011

Hybrid air-foil magnetic bearing integrates two oil free bearing technologies synergetically to adopt the strengths of two bearings with minimizing their weaknesses. This paper presents bending mode vibration control of a flexible shaft supported by the hybrid air-foil magnetic bearing. An experiment set-up of a flexible shaft supported by the hybrid air-foil magnetic bearing is built. In order to verify the effectiveness of the hybrid bearing, unbalance responses of the flexible shaft supported by three different bearings: air-foil, magnetic and hybrid bearings are compared. Effect of load sharing between air-foil and magnetic bearings are investigated through changing the control gain and the rotor center position of magnetic bearing. The experimental results shows that the hybrid bearing can control the bending mode vibration of the flexible shaft effectively and an optimal performance can be achieved with an appropriate load sharing between the air-foil and the magnetic bearings.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 추계학술대회논문집
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• pp.677-684
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• 2004

This paper describes a method for identifying the dynamic characteristics of air foil bearings for high speed turbomachinerys with the LS/IV method. In fact identifying the characteristics of air foil bearings is very difficult work, and it is tried to identify it. Experiments were conducted to determine the structural dynamic and hydrodynamic characteristics of air foil bearings. Numerical predictions compare the static and dynamic force performances. The housing of the bearing on the journal was driven by the impact hammer which were used to simulate impact force acting on air foil bearings. The characteristics of air foil bearings were extracted from the frequency response function (FRF) by LS(Least Square) method and IV(Instrumental Variable) method. The experiment was tested at 0 rpm and $10000\sim16000rpm$. And the test results were introduced about the dynamic characteristics of air foil bearings, and also compared with theoritical results.

• Tribology and Lubricants
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• 제22권5호
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• pp.252-259
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• 2006

Air foil bearing supports the rotating journal using hydrodynamic force generated at thin air film. The bearing performances, stiffness, damping coefficient and load capacity, depend on the rotating speed and the performance of the elastic foundation, bump foil. The main focus of this study is to decide the dynamic performance of corrugated bump foil, structural stiffness and Coulomb damping caused by friction between bump foil and top foil/bump foil and housing. Structural stiffness is determined by the bump shape (bump height, pitch and bump thickness), dry-friction, and interacting force filed up to fixed end. So, the change of the characteristics was considered as the parameters change. The air foil bearing specification for analysis follows the general size; diameter 38.1 mm and length 38.1 mm (L/D=1.0). The results show that the stiffness at the fixed end is more than the stiffness at the free end, Coulomb damping is more at the fixed end due to the small displacement, and two dynamic characteristics are dependent on each other.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 춘계학술대회논문집
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• pp.1135-1141
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• 2006

Air foil bearing supports the rotating journal using hydrodynamic force generated at thin air film. The bearing performance, stiffness, damping coefficient and load capacity, depends on the rotating speed and the performance of the elastic foundation, bump foil. The main focus of this study is to decide the dynamic performance of corrugated bump foil, structural stiffness and Coulomb damping caused by friction between bump foil and top foil/bump foil and housing. Structural stiffness is determined by the bump shape (bump height, pitch and bump thickness), dry-friction, and interacting force filed up to fixed end. So, the change of the characteristics was considered as the parameters change. The air foil bearing specification for analysis follows the general size; diameter 38.1 mm and length 38.1mm (L/D=1.0). The results show that the stiffness at the fixed end is more than the stiffness at the free end, Coulomb damping is more at the fixed end due to the small displacement, and two dynamic characteristics are dependent on each other.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2006년 제4회 한국유체공학학술대회 논문집
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• pp.331-334
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• 2006

Air foil bearings have been attempted for application to industrial turbo machines, since they have several advantages over oil bearings in terms of endurance, simplicity, environment-friendliness, efficiency, sound and vibration, and small turbo machines with air foil bearings are in the market as the result. Recently, researches on widening the application spectrum of air foil bearings are in progress worldwide. In this paper, a 300 HP class turbo blower using air foil bearings is introduced. The turbo blower has a high speed PMSM(Permanent Magnet Synchronous Motor) driving a compressor, and air flow rate is designed to be $180\;m^3/min$ at pressure ratio of 1.6. The maximum rotational speed is set to 17,000 RPM to maximize the total efficiency with the result that the weight of rotor assembly is 26kg, which is expected to be the largest turbo machine with air foil bearings ever developed in the world.