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2차원 미세 포켓이 있는 무한장 Slider Bearing의 CFD 해석
박태조(Tae-Jo Park),황윤건(Yun-Geon Hwang),손자덕(Ja-Deok Sohn),정호경(Ho-Gyeong Chung) 한국트라이볼로지학회 2009 한국윤활학회지(윤활학회지) Vol.25 No.1
It is reported by many researchers that the textured bearing surfaces, where many tiny micro-pockets or enclosed recesses were incorporated, can enhance the load support and reduce friction force. Recently, the basic lubrication mechanism of micro-pocketed parallel surfaces are explained in terms of "inlet suction" using continuity equation and simply cavitation condition. However, it is required that more actual cavitation condition in the pocket region should be applied to estimate exact bearing performance. In this paper, a commercial computational fluid dynamics (CFD) code, FLUENT is used to investigate the exact lubrication characteristics of infinitely long slider bearing with micro-pockets. The results show that the pressure distributions are highly affected by pocket depths, its positions and numbers. The numerical method adopted in this paper and results can be use in optimal design of textured sliding bearings.
미세 포켓이 있는 무한장 Slider Bearing의 CFD 해석
박태조(Tae-Jo Park),황윤건(Yun-Geon Hwang),손자덕(Ja-Deok Sohn),정호경(Ho-Gyeong Chung) 한국트라이볼로지학회 2008 한국트라이볼로지학회 학술대회 Vol.2008 No.6
It is reported by many researchers that the textured bearing surfaces, where many tiny micro-pockets or enclosed recesses were incorporated, can enhance the load support and reduce friction force. Recently, the basic lubrication mechanism of micro-pocketed parallel surfaces are explained in terms of "inlet suction" using continuity equation and simply cavitation condition. However, it is required that more actual cavitation condition in the pocket region should be applied to estimate exact bearing performance. In this paper, a commercial computational fluid dynamics(CFD) code, FLUENT is used to investigate the exact lubrication characteristics of infinitely long slider bearing with micro-pocket. The results show that the pressure distributions are highly affected by pocket depths, its positions and numbers. The numerical method adopted in this paper and results can be use in design of textured sliding bearings.
미세 포켓이 있는 무한장 Slider Bearing의 THD 해석
이준오(Joon-Oh Lee),박태조(Tae-Jo Park) 대한기계학회 2012 대한기계학회 춘추학술대회 Vol.2012 No.11
Friction reduction between sliding machine components is essentially required to improve efficiency and reliability of machineries. Continuous design improvements and adoption of new operation methods have been done to this purpose. Recently it is reported that the textured bearing surfaces, where many tiny micro-pockets or enclosed recesses were incorporated, can reduce friction force highly and more over enhance the bearing load support capacity. However all the previous researches are not considered the thermal effects due to oil viscosity. In this paper, a commercial computational fluid dynamics (CFD) code, FLUENT is used to investigate the thermohydrodynamic (THD) lubrication characteristics of infinitely long slider bearing with a micro-pocket. Pressure distributions, load support capacity and friction force acting on bearing are compared with the results of isothermal analysis. Overall lubrication characteristics of a micro-pocketed slider bearing are considerably affected by viscous heating. Present numerical methods and results can be applied in optimum design of textured bearing surfaces and further researches are required.
최대호기속도 측정에서 Mini Wright Peak Flow Meter와 Microplns Pocket Spirometer의 비교
나영호,배종우,정사준 대한 소아알레르기 및 호흡기학회 1999 소아알레르기 및 호흡기학회지 Vol.9 No.2
목 적 : 최대호기속도(peak expiratory flow rate PEFR)와 같은 간단한 폐기능 측정은 기도폐쇄 정도의 평가와 천식 환자의 감시에 유용하게 사용되고 있다. 특히 기관지천식 환자에서 반복적으로 측정된 PEFR치는 환자의 경과를 관찰하는데 객관적인 지표로서 그 가치가 높다. PEFR 측정에는 mini-Wright peak flow meter가 주로 사용되고 있으나 최근에는 PEFR 이외에 FEV_1 및 FVC를 측정할 수 있는 Microplus pocket spirometer도 사용되고 있는 바, 본 연구자들은 PEFR 측정에 있어서 신뢰도가 검증된 mini-Wright peak flow meter와 Microplus pocket spirometer를 비교하고자 본 연구를 시행하였다. 방 법 : 연구 대상은 건강한 11-12세의 초등학생 80명(남아 37명, 여아43명)으로 하였으며 이들은 조사 당시에 상기도 감염이나 기도 폐쇄 소견이 없었다. PEFR은 일정한 간격을 두고 mini-Wright peak flow meter(Clemente Clark, UK)와 Microplus pocket spirometer(Micro Medical, Ltd. UK)를 임의의 순서로 사용하여 각각 3회 측정하였다. 두 기구에 의한 각각의 PEFR 측정치간의 일치성(95% limits of agreement)과 각 기구에 의한 측정치의 재현성(repeatability coefficient)을 Bland와 Altman에 의해서 고안된 통계학적 방법으로 분석하였다. 결 과: 1) 76명(95%)에서 Microplus pocket spirometer가 mini-Wright Beak flow meter보다 낮은 PEFR치를 나타냈다. 2) 두 기구의 PEFR 측정치의 95% limits of agreement는 2.7 L/min에서 144.3 L/min으로 차이범위가 넓었으며 측정치의 최대차이는 141.6 L/min 이었다. 3) mini-Wright peak flow meter와 Microplus pocket spirometer로 측정한 PEFR의 측정치의 재현성(reproducibility)을 나타내는 repeatability coefficient는 각각 27 L/min과 33.5 L/min로 Microplus pocket spirometer에서 높았다. 4) 두 기구의 사용 순서나 성별에 따른 PEFR 측정치의 유의한 차이는 없었다. 결 론 : Microplus pocket spirometer는 mini-Wright peak flow meter와 PEFR 측정치의 비교에서 유사한 재현성을 보였으나 넓은 95% limit of agreement를 나타내어 두 기구간에 낮은 일치성을 보였다. 따라서 PEFR 측정에 의한 주기적인 폐기능의 감시에는 같은 기기를 계속 사용하는 것이 보다 정확하고 객관적인 폐기능 수치를 얻을 수 있을 것으로 사료된다. Purpose : Peak expiratory flow rate(PEFR) monitoring plays an important role in the diagnosis of airway obstruction and management of patients with bronchial asthma. This study compared the PEFR taken by a Microplus pocket spirometer and mini-Wright peak flow meter by assessing the extent of agreement between the instruments and the repeatability of measurements with each instrument. Methods : Eighty healthy children(age 11-12 years, 43 females, 37 males) performed three PEFR maneuvers on the Microplus pocket spirometer and on the mini-Wright peak flow meter in a random order. Agreement and reproducibility between the two instruments were assessed by the statistical methods proposed by Bland and Altman. Results : Seventy six(95%) of the PEFR taken by the mini-Wright peak flow meter were higher than that of Microplus pocket spirometer. The 95% limits of agreements(mean difference±2SD) between each instrument were very wide(2.7 to 144.3 L/min). The repeatability coefficient for the mini-Wright peak flow meter was 27 L/min and for the Microplus pocket spirometer was 33.5 L/min. Analysis by sex and order of usage did not show any significant differences. Conclusion : The limit of agreement between the Microplus pocket spirometers and the mini-Wright peak flow meter was too wide to use interchangeably.
[기술논문] RE-EV용 엔진 발전기의 구동 부품의 마찰력 저감에 관한 연구
나완용(Wan Yong Rha) 한국자동차공학회 2014 한국 자동차공학회논문집 Vol.22 No.4
Recently, there has been an active study about friction force of moving parts for automotive. This study is development and evaluation of oil pockets for journal bearing and tappet valve for range extended electric vehicle. Specially , oil pockets are effect on friction force depend on pitch, size, depth. In this study, fine oil pocket was formed using by etched texturing on the journal bearing and tappet valve. And oil pocket analyzed by SEM and friction force test was carried out by tensile tester. Finally, in this study, it was suggested by round and plane part which journal besring and tappet valve.