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최태규(Tae Gyu Choi),김태호(Tae Ho Kim) 한국트라이볼로지학회 2014 한국트라이볼로지학회지 (Tribol. Lubr.) Vol.30 No.2
This study set out to predict the load capacity and rotordynamic coefficients of tilting-pad journal bearings, taking the pivot stiffness into account. The analysis uses rocker-back (cylindrical) and ball in socket (spherical) pivot models, both of which are based on Hertzian contact stress theory. The models ascertain the non-linear elastic deformation of the pivots according to the applied load, pivot geometry, and material properties. At present, the Reynolds equation for an isothermal, isoviscous, and incompressible fluid is used to calculate the film pressure by using the finite-element method, after which the Newton?Raphson method is used to simultaneously find the journal center location, pad angles, and pivot deflections. The bearing analysis, excluding the pivot models, is validated using predictions those are readily available in the literature. As the rotor speed increases, the predicted journal eccentricity and damping coefficients decrease, but the stiffness coefficients increase, as expected. Most importantly, the implementation of the pivot models increases the journal eccentricity but significantly decreases the stiffness and damping coefficients of the tilting-pad journal bearings.
최태규 ( Tae Gyu Choi ) 한국인터넷비즈니스학회 2009 인터넷비지니스연구 Vol.10 No.1
2008년 작년 한 해에만 베이징 주재 기업의 30% 이상이 중국 사업을 정리 하거나 규모를 대폭 축소하였다. 하지만 이런 끝이 없어 보이는 불황의 시기에도 오히려 성장을 거듐해 나가고 있는 분야가 있다. 바로 "전자 상거래" 가 그것이다. 현재 중국 전자 상거래는 전 세계가 경제 위기에 부딪힌 상황에도 불구하고 상당한 발전과 성장을 이루어 냈으며, 또한 그 미래가 어느 정도는 안정된 것이 사실이다. 하지 만 은행권과의 지불 연계, 인터넷 네트워크 안정화, 온라인 도덕관념의 성숙 등 아직 중 국 전자 상거래 분야가 모든 면에서 과도기적 단계를 거치고 있기 때문에 낙관론만으로 일관할 수는 없지만 어느 나라, 어느 시대에서도 과도기적 단계는 기회이다. 지속적인 업무개선과 효율화 방안만 지속적으로 보강된다면 앞으로 FS- STATION의 발전을 계 속 될 것이다. Only in the past year of 2008, more than 30% Beijing residentiary company cleared up their business or cut back on new projects. However, in the depression like endless situation, there is a developing business that is, electronic commerce. The current Chinese electronic commerce have become pretty developed and grown up in spite of world economic crisis and it is true that its future will be stabilized. Nevertheless it is not all optimistic because Chinese electronic commerce is on the transition period, which has to be in payment connection with bank, stabilization of internet network and on-line moral manners but transition period is a opportunity in every country and every age. If continuous better business and efficienct plans were supplied, FS-STATION could develop constantly.
로커-백 피벗을 갖는 틸팅 패드 저널 베어링의 회전체동역학적 성능 예측 및 기존 결과와의 비교
김태호(Tae Ho Kim),최태규(Tae Gyu Choi),김충현(Choong Hyun Kim) 한국트라이볼로지학회 2015 한국트라이볼로지학회지 (Tribol. Lubr.) Vol.31 No.6
In this paper, we predict the rotordynamic force coefficients of tilting pad journal bearings (TPJBs) with rocker-back pivots, and we compare the predictions to recently published predictions and test data. The present TPJB model considers the rocker-back pivot stiffness calculated based on the Hertzian contact-stress theory, which is nonlinear with the application of a force . For the five-pad TPJB in load-between-pad and loadon-pad configurations, the predictions show the pressure- and film-thickness distributions, the deflection and stiffness of the individual pivots, and bearing stiffness and damping coefficients. The minimum film thickness and peak pressure occur at the bottom pad on which the applied load is directed. Because of the preload, the pressure is positive even at the upper pad in the opposite direction to the applied load. The pivot deflection and stiffness are maximum at the bottom pad that receives the heaviest pressure load. The predicted stiffness coefficients increase as the static load and rotor speed increase, while the damping coefficients decrease as the rotor speed increases, but increase as the static load increases. In general, the predicted stiffness coefficients agree well with the test data. The predicted damping coefficients overestimate the test data, particularly for large static loads. In general, the current predictive model considering the pivot stiffness improves the accuracy of the rotordynamic performance compared to previously reported models.
승도현(Dohyun Seung),최태규(Tae Gyu choi),이주혁(Joo Hyuk Lee),홍희기(Hiki Hong) 대한설비공학회 2019 대한설비공학회 학술발표대회논문집 Vol.2019 No.11
In this study, we are going to analyze the cooling capacity and COP of the solar power hybrid desiccant cooling system (HDCS), one of the heat-driven cooling systems, to conduct a demonstration of the system. The hybrid desiccant cooling system can be driven by relatively low-temperature heat sources and inserts a heat pump into the air-conditioning system, which has also succeeded in miniaturizing it through proper arrangement of evaporator and condenser. If the ambient air temperature is 32℃, the temperature of the storage top showed a cooling capacity of 12.49 ㎾ at 73℃ and COP was 5.4. Under the same outdoor conditions, cooling capacity and consumption power tended to increase as the temperature of the storage top decreased, and COP tended to decrease. In addition, if the temperature decreases, dehumidification does not occur due to the lack of regenerating of the dehumidification rotor. In such a case, the indirect evaporation cooler and the heat pump alone are used for cooling, and the cooling capacity and COPele are decreasing, but the consumption power is also significantly reduced.