• Tribology and Lubricants
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• v.34 no.3
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• pp.75-83
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• 2018

Microturbomachinery (< 250 kW) using gas foil bearings can function without oil lubricants, simplify rotor-bearing systems, and demonstrate excellent rotordynamic stability at high speeds. State-of-the-art technologies generally use bump foil bearings or leaf foil bearings due to the specific advantages of each of the two types. Although these two types of bearings have been studied extensively, there are very few studies on leaf-bump foil bearings, which are a combination of the two aforementioned bearings. In this work, we illustrate a simple mathematical model of the leaf-bump foil bearing with leaf foils supported on bumps, and predict its static and dynamic performances. The analysis uses the simple elastic model for bumps that was previously developed and verified using experimental data, adds a leaf foil model, and solves the Reynolds equation for isothermal, isoviscous, and ideal gas fluid flow. The model predicts that the drag torques of the leaf-bump foil bearings are not affected significantly by static load and bearing clearance. Due to the preload effect of the leaf foils, rotor spinning, even under null static load, generates significant hydrodynamic pressure with its peak near the trailing edge of each leaf foil. A parametric study reveals that, while the journal eccentricity and minimum film thickness decrease, the drag torque, direct stiffness, and direct damping increase with increasing bump stiffness. The journal attitude angle and cross-coupled stiffness remain nearly constant with increasing bump stiffness. Interestingly, they are significantly smaller compared to the corresponding values obtained for bump foil bearings, thus, implying favorable rotor stability performance.

• Tribology and Lubricants
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• v.17 no.4
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• pp.290-296
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• 2001

Lift-off means that the rotating journal surface separates from the leaf surface in an air-lubricated multi-leaf foil journal bearing. Lift-off builds up minimum film thickness which will provide load capacity between leaves and journal. In this paper an analysis of air-lubricated multi-leaf foil journal bearing was performed with effects of multi-leaf foil deflection and compressible lubrication equation simultaneously. Minimum film thickness built up versus journal speed predicts the lift off characteristics and these results will be useful in designing and selecting the proper speed of the air-lubricated multi-leaf foil journal bearing.

• Tribology and Lubricants
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• v.17 no.2
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• pp.97-108
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• 2001

This paper describes the development of performance analysis technique for a leaf-type gas lubricated fail bearing. Stiffness coefficient and frictional damping due to the slip between all contacts of leaves are evaluated for various leaf structures. The fluid film thickness and pressure distribution are computed but it is not considered the elastic deformation by film pressure. The analysis results include the effects that the curvature radius and the length of leaf and the friction coefficient have on the static and dynamic characteristics of the foil bearings.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2000.11a
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• pp.177-185
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• 2000

The characteristics of multi-leaf feil bearing are investigated. The Foil bearing is preloaded and has several leaf foils modeled by curved beams. An analysis of the air foil bearing was performed, considering effects of foil deflection and compressible lubrication equation simultaneously. A parametric study shows that the number of foils significantly affect the static characteristics of air foil bearings and describes what the minimum film thickness means. The results include pressure profile, load capacity, dimensionless torque and minimum film thickness in the foil bearing.

• 유체기계공업학회:학술대회논문집
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• 2001.11a
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• pp.482-487
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• 2001

Leaf type foil bearings have been used successfully in many aerospace applications such as air cycle machines, turbocompressors and turboexpander. These applications are characterized by light loads, constant speeds and low to moderate temperatures. But, as system on start-up or shutdown, sliding contact between the shaft and foil surfaces cause wear. So, in present study, to understand pressure-flow characteristics and deformation of foil bearing, flow/structure interaction analysis was used. and using this method, 2D and 3D calculation was peformed for shape of foil bearing to know circumferential direction flow and leakage flow characteristics of axial direction.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.05a
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• pp.936-941
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• 2001

This paper deals with the design of oil-tree motor-driven two-stage centrifugal compressor supported by air-lubricated multi-leaf foil bearings. The design of this compressor is performed, based upon prediction of critical speeds, load capacity, and stability. It is demonstrated in this paper that multi-leaf foil bearings can be adopted to satisfactorily support this centrifugal compressor.

• Journal of Conservation Science
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• v.37 no.1
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• pp.43-54
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• 2021

In this study, a scientific analysis of the gold leaf layers and internal structure of the Clay Seated Vairocana Buddha Triad in Seonunsa Temple, Gochang (Treasure No. 1752) was conducted. The surface of the Buddha statues is a gold foil, and the gold leaf layer consists of four layers. The gold leaf layer first composed on the molding clay was produced in the order of lacquer-fabrics-lacquer-gold foil. Subsequently, it was confirmed that the work was performed three times in the same way. The composition of the Buddha statues was divided into the head, body or upper body, lower body, and pedestal. The body was made in a cylindrical form by connecting vertically oriented wooden materials, and the head and lower body were also connected to the body in an empty form. Thus, the head, body, and lower body are grafted structures that are connected to a single Bokjang-gong. It was confirmed that the Clay Seated Vairocana Buddha Triad in Seonunsa Temple was made using wood materials for the basic form, after which the detailed form was created with molding clay, and the surface was finished with a process of layering gold foil and substances presumed to be lacquer.

• Fashion & Textile Research Journal
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• v.24 no.1
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• pp.95-107
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• 2022

In reality, the distinction between the Korean traditional culture and the cultures of other countries is at a delicate boundary. Additionally in the wake of the recent socio-cultural confrontation between Korea and China, it has become necessary to establish the foundation and area of Korean traditional culture and to actively utilize the importance of improving awareness of Korean traditional culture. To reorganize the reckless use of the gold foil pattern shown in the rental hanbok, data on the museum's collection of gold leaf patterns were collected and analyzed. Based on the gold foil, Gilsang characters such as Phoenix pattern, Crane pattern, Bat pattern, Flower pattern, Fruit pattern and recovery advice were extracted through references. The traditional gold foil pattern was reconstructed and relocated to design the gold leaf patch. Based on the collection and analysis of the museum's relics, the Wonsam & Daedae, Dangeui, Sranchima, Sagyusam, Jeonbok, Bokgun, and Daenggi were produced. Therefore, we present the possibility of producing gold foil and modern methods for producing gold foil using laser cutting techniques that can express refinement and complexity well, and gold foil thermal transfer paper with retouchable effects. Additionally, we would like to reflect upon the practicality and the convenience to modern people by considering the complexity and hassle of the traditional gold foil production process, and the disadvantages of processes that require relatively longer time. It intends to help revitalize the market of Korean traditional clothing and fashion products.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11a
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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.

• Transactions of the Korean Society of Mechanical Engineers
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• v.10 no.3
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• pp.399-407
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• 1986

본 연구에서는 공기역학 탄성베어링의 설계에 필요한 기본이론에 대하여 고찰 하고 그의 신빙성을 그러한 베어링에 지지된 고속회전축의 진등측정을 통하여 검토하 고저 한다. 탄성베어링의 한 예로써 여러 개의 탄성박판이 겹쳐 저어널을 지지하는 겹판베어링(