• Title/Summary/Keyword: end bearing

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Effect on Seal Tooth Clearance on Power Loss and Temperature of Tilting Pad Journal Bearing (씰 투스 간극이 틸팅 패드 저어널 베어링 손실과 온도에 미치는 영향)

  • Bang, Kyungbo;Choi, Yonghoon;Cho, Yongju
    • Tribology and Lubricants
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    • v.34 no.5
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    • pp.183-190
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    • 2018
  • Tilting pad journal bearing is widely used for steam turbines because of its excellent dynamic stability. As the turbine capacity increases, power loss in the bearings becomes a matter of concern. Power loss in tilting pad journal bearings can be reduced by increasing the bearing clearance and reducing the pad arc length. In this study, the tilting pad journal bearing is tested by changing the seal tooth clearance to verify the static characteristics of the bearing. Bearing power loss and bearing metal temperature are evaluated to compare the bearing's performance and reliability for several test cases. The test bearing is a tilting pad journal bearing with 300.62mm inner diameter and 120.00mm active length. The bearing power loss, its metal temperature, and oil film thickness are measured and evaluated based on the rotor's rotational speed, oil flow rate, and bearing load. Test results show that a tilting pad journal bearing with large seal tooth clearance has 40% lower power loss compared with a bearing with a small seal tooth clearance. As the seal tooth clearance is increased, the power loss of the tilting pad journal bearing decreases. However, with respect to the bearing metal temperatures, a detuning point is observed that makes the minimum bearing metal temperature. Moreover, as the seal tooth clearance is increased, the oil film thickness increases due to high viscosity.

Corrosion Resistance of Cr-Bearing Rebar to Macrocell Corrosion Environment Induced by Localized Carbonation

  • Tae, Sung-Ho
    • International Journal of Concrete Structures and Materials
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    • v.18 no.1E
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    • pp.17-22
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    • 2006
  • Artificial cracks were made in the cover concrete of specimens embedding ten types of steel rebars of different Cr contents. The research aims for developing Cr-bearing steel rebars resistant to macrocell corrosion environments induced by cracking in cover concrete. The cracks were subjected to intensive penetration of carbon dioxide (carbonation specimens) to form macrocells. The carbonation specimens were then treated with accelerated corrosion curing, during which current macrocell corrosion density was measured. The corrosion area and loss from corrosion were also measured at the end of 105 cycles of this accelerated curing. The results of the study showed that Cr-bearing steel with Cr content of 5% or more suppressed corrosion in a macrocell corrosion environment induced by the differences in the pH values due to carbonation of cracked parts. Cr-bearing steels with Cr content of 7% or more are proven to possess excellent corrosion resistance.

Dynamic Characteristics Analysis of the Carriage Structure Supported by Air Bearing (공기베어링으로 지지된 캐리지 구조물의 동특성 해석)

  • 정순철;김덕수;유충준;장승환
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.14 no.11
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    • pp.1059-1065
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    • 2004
  • In this paper, the dynamic characteristic analysis of carriage structure supported by air bearings were performed. Toward this end, the characteristics of air bearing were numerically analyzed to estimate the stiffness of the air bearing and the clearance between air bearing and guide surface. The modal analysis of the carriage structure was performed by using finite element method, and the experimental modal analysis was also performed to validate the finite element model, where rigid body modes were compared to validate the stiffness of the air bearings. From the results, the air spring stiffness can be estimated within the range of acceptable accuracy under any pressure and clearance condition.

Dynamic Characteristics Analysis of the Carriage Structure Supported by Air Bearing (에어베어링으로 지지된 캐리지 구조물의 동특성 해석)

  • 정순철;김덕수;유충준;장승환;이재응
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2003.05a
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    • pp.1107-1114
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    • 2003
  • In this thesis, the dynamic characteristic analysis of carriage structure supported by air bearings were peformed. Toward this end, the characteristics of air bearing were numerically analyzed to estimate the stiffness of the air bearing and the clearance between air bearing and guide surface. The modal analysis of the carriage structure was peformed by using finite element method, and the experimental modal analysis was also performed to validate the finite element model, where rigid body modes were compared to validate the stiffness of the air bearings. From the results, the air spring stiffness can be estimated within the range of acceptable accuracy under any pressure and clearance condition.

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The Measurement of the Bearing Stiffness (베어링 강성 측정)

  • Kim, Sang-Uk;Kim, Jin-Hwan;Kim, Yong-Geun;Kim, Bo-Youl;Kim, Young-Bong
    • Proceedings of the KIEE Conference
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    • 2006.10b
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    • pp.216-220
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    • 2006
  • This paper is presented for the measurement of the bearing stiffness for the spindle motors. BLDC Spindle Motors for the Hard Disk Drive are used by several kinds of the bearings, such as ball bearing, fluid dynamic bearing, and aero dynamic bearing. The spindle motors are attached the platters to read and write the data. Because the platter rotates at high end speed with the load and can be shocked from a suddenly moving, the bearing needs the rated stiffness with the pressure. By the way, it has not been realized to measure the real stiffness for each bearing types. In this paper, we proposed the method of measuring the stiffness for the bearings by using the magnet force. Experimental results show the performance to measure the bearing stiffness of the BLDC spindle motors for an HDD.

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Vibration Characteristics of Impeller Shaft for Mixing Machine According to the Positions of a Bearing Support (교반기용 임펠러가 달린 축의 베어링 지지점에 따른 진동특성)

  • Hong, Do-Kwan;Ahn, Chan-Woo;Baek, Hwang-Soon;Choi, Seok-Chang;Park, Il-Soo
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.8 no.3
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    • pp.68-73
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    • 2009
  • This paper deals with the dynamic characteristics of the impeller shaft model which is the most important part in developing the resin mixing machine. The can is rotating by air motor in mixing machine. Then the end of shaft is fixed. The bearing support is to increase the fundamental natural frequency. The natural frequency analysis using finite element analysis software are performed on the imported commercial impeller shaft model. This paper presents calculated bearing stiffness of Soda, Harris and modified Harris formula considering contact angle according to bearing supported position. The most important fundamental natural frequency of the impeller shaft except bearing support is around 13.932 Hz. This paper presents one bearing and two bearings support position to maximize the 1st natural frequency. The maximized fundamental natural frequency is around 48.843 Hz in one bearing support and 55.52 Hz in two bearings support.

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Evaluation on Shear Behavior of Double-tee Dap-ends with the Least Depth from Optimization Proces (최적이론에 의하여 설계된 최소 깊이 더블티 댑단부 전단거동 평가)

  • 유승룡;김대훈
    • Journal of the Korea Concrete Institute
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    • v.11 no.4
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    • pp.43-54
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    • 1999
  • Shear tests are performed on four full-scale 12.5 m proto-type models, "least depth double tee," which are resulted from the optimization process. Domestic superimposed live load regulation, domestic material properties which is available to product. Korean building code requirements, construction environments and economy are considered as the main factors to establish the process. All of the specimens tested fully comply with the shear strength requirements as specified by ACI 318-95. The research has shown following results. 1) The development length requirement of ACI 318-95 does not seem a good predictor for the estimation of bond failure in a beam with the strands below the supports. 2) The load required for the first initial coner cracking in the dap end and first web shear cracking does not seem to have any relation with the dimension and shear strength of the section in the test beams. 3) The strand slip has a direct relationship with the web shear cracking. However, the coner cracking in the dap end does not give any help for the slip in anchorage. 4) Use of whole area for bearing steel at the bottom of dap end is desired for safe bearing pressure design in the precast prestressed double tee beams. 5) The deflection of beam influences directly on the amount of strand slip at the anchorage after initiation of it, and relationship between them are very linear.