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LNG 펌프용 깊은 홈 구름 베어링 시험장치: 동역학적 안정성 평가
이영도,곽원일,하윤석,이전국,이용복 한국유체기계학회 2023 한국유체기계학회 논문집 Vol.26 No.6
The ball bearings used to support the shaft of LNG pumps are nonstandard bearings. The bearings operate in the cryogenic environment(-162°C) and they are a type of self-lubricated ball bearing using solid lubricant and have larger internal clearance grade than general standard bearings. The defect in ball bearings is the most common failure cause of LNG pumps. In order to ensure the stable operation of LNG pumps, it is important to optimize the design of bearings with the performance evaluation test and reliability test that ensure fatigue life is also needed. In this paper, the tribo-test apparatus was developed for the performance test and reliability test. This test apparatus is designed to evaluate the performance by measuring friction torque and cage orbit of test bearings. Prior to the perform the ball bearing test, the verification test of the test apparatus was done by operating for about 4 hours with the LN2(-189°C) submerged chamber. The stability of the rotor system(motor to shaft) was monitored with the motor input current. The relation between motor input current and torque was confirmed by the test. After the verification of the test apparatus, the performance test of a ball bearing was performed. As we verified, the rotor system was stable and friction torque and cage whirling orbit was measured properly. From these results, we can expect that this apparatus would be helpful in developing the process of ball bearings used in LNG pumps.
고분말도 시멘트와 플라이애시를 사용한 콘크리트의 물리적 특성
이영도,하정수,김한식 한국건축시공학회 2019 한국건축시공학회지 Vol.19 No.4
The cement industry is considered a major industry for reducing greenhouse gases, increasing the amount of binding materials that can replace cement in concrete is known as the most effective method for reducing carbon dioxide. Therefore, research is being carried out to utilize large quantities of by-products that can be used as alternatives to cement. However, there are problems with reduced strength at early age and retarded setting for major reasons that do not increase the amount of mixture of binders used to replace cement. Thus, in this study, normal cement and high-fineness cement were used and physical properties were reviewed by placing differences in fly ash usage depending on the type of cement. As a result, the characteristics of strength were similar, and the hydration temperature was the same level. Also, the durability test showed that the length change, carbonation resistance were better than those of normal cement. Therefore, it is confirmed that the use of high-fineness cement is effective to reduce the amount of cement used and using more by-products. 시멘트 산업은 온실가스 감축을 위한 주요 산업분야로 고려되고 있으며, 콘크리트에 시멘트를 대체할 수 있는 재료의 사용량을 증가시키는 것은 이산화탄소 감축을 위해 효과적인 방법으로 알려져 있다. 따라서 시멘트의 일부를 대체하여 사용할 수 있는 산업부산물을 다량으로 활용하기 위한 연구가 진행되고 있다. 그러나 산업부산물의 혼합량을 증가시키지 못하는 큰 이유로 초기강도 저하와 응결지연에 대한 문제점이 있다. 따라서 이 연구에서는 보통 시멘트를 사용한 경우와 고분말도 시멘트를 사용한 경우에 대해 플라이애시의 사용량에 차이를 두고 물리적 특성을 검토하여, 시멘트의 사용량을 줄이고 산업부산물을 다량으로 사용하기 위한 방안으로서, 고분말도 시멘트를 활용한 결과에 대한 기초 자료를 제시하였다.