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삼화 원탄과 무회분탄의 촉매(K₂CO₃) 가스화 반응성 비교 연구
공용진(Yongjin Kong),임정환(Junghwan Lim),임영준(Youngjoon Rhim),전동혁(Donghyuk Chun),이시훈(Sihyun Lee),유지호(Jiho Yoo),이영우(Young-Woo Rhee) 한국청정기술학회 2014 청정기술 Vol.20 No.3
석탄의 가스화는 촉매 도입 시 온순 조건에서 가능하나, 석탄 내 회분에 의한 비활성화에 의해 반복적인 촉매 활용이 힘들다. 이에 본 연구에서는 삼화 원탄에서 회분을 제거하여 삼화 무회분탄(ash-free coal, AFC)을 제조한 후 가스화 반응성을 원탄과 비교하여 알아보았다. 우선 원탄을 대상으로 고정층 반응기에서 수증기 공급량, 공간 속도(space velocity), 온도 및 촉매를 변수로서 가스화 조건을 결정하였다. 고체상 혼합법으로 다양한 촉매 도입 시, 유동성을 갖는 K₂CO₃가 가장 높은 활성을 보였다. 무회분탄은 원탄보다 낮은 반응성을 보였으며, 이는 용매(1-methylnaphthalene, 1-MN)를 이용한 고온 추출 및 건조 공정 중에 소모된 산소 기능기 함량과 증가된 탄화도(carbonization)에 기인한다. K₂CO₃ 가 혼합된 무회분탄의 반응성은 급격히 증가하여 낮은 온도 (700 ℃)에서도 높은 전환율을 보였다. 이때 H₂/CO와 CO₂/CO 비율도 증가하는데, 이는 촉매에 의해 수성가스전환(water-gas shift) 반응이 활성화됨에 기인한다. 본 연구에서는 무회분탄의 저온 촉매 가스화 반응을 통해 석탄 가스화 공정의 경제성이 개선될 수 있음을 확인하였다. Catalytic gasification of raw coals at mild condition is not realized yet mainly due to deactivation of catalysts via their irreversible interaction with mineral matters in coal. In this work, the gasification behavior of ash-free coal (AFC) was compared with that of the parent raw coal. In order to modify the gasification conditions, the raw coal gasified with fixed variables (water supply, space velocity, temperature, catalysts) in a fixed bed reactor. When catalysts are added by physical mixing method with coal, K₂CO₃ was the most effective additives for steam gasification of coal. However, the activity of ash-free coal (AFC) was much less reactive than raw coal due to high temperature extraction in a 1-methylnaphthalene under 30bar at 370 ℃ for 1 h, almost removed oxygen functional groups, and increased carbonization. The addition of K₂CO₃ in AFC achieved higher conversion rate at low temperature (700 ℃). At that time, the molar ratio of gases (H₂/CO and CO₂/CO) was increased because of water-gas shift reaction (WGSR) by addition of catalysts. This shows that catalytic steam gasification of AFCs is achievable for economic improvement of gasification process at mild temperature.
문일동(Ildong Moon),김기태(Gitae Kim),임정환(Junghwan Lim),현상학(Sanghak Hyun),오재윤(Chaeyoun Oh) 한국자동차공학회 2008 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
The steering feel is one of the major handling performance of the vehicle. This paper develops a computational model for objective steering feel assessment of a commercial vehicle. In order to validate the reliability of the developed computation model, tests with a real vehicle are performed. Simulation results performed with the developed computational model shows a good correlation with test results performed with a real vehicle. The developed model is used for analyzing the influence of the characteristic of a steering system and tire on steering feel. That is, a study is performed to analyze the influence of the major parameters which significantly affect on the characteristic of the steering system and tire on steering feel with the developed model.
유연체 판스프링 모델을 이용한 서스펜션 지오메트리 연구
김기태(Gitae Kim),문일동(Ildong Moon),임정환(Junghwan Lim) 한국자동차공학회 2006 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
This paper proposes a modeling technique which is able to not only reliably and easily represent the wheel rate but also analyze the suspension characteristics. The flexible body model of the leaf spring is developed by interfacing the finite element model and computation model of the leaf spring. The SPMD test of the vehicle is conducted for the validation of the reliability of the flexible body model of the leaf spring developed in this paper. The SPMD test is started at an constraint state of frame using the jig with the excitation amplitude of 1-2㎜/sec. The simulation is conducted with the same condition as the SPMD test. Then, the simulations are conducted with bump mode and roll mode. The diagram of wheel rate and wheel alignment from the SPMD test is compared with the ones from the simulation for the validation of the reliability of the model. The flexible body of the leaf spring is compared with the rigid body of the leaf spring. The sensitivity analysis of the front suspension and steering system is also conducted with the developed flexible body model under a bump mode of K&C analysis.
김용일(Yongil Kim),김기태(Gitae Kim),임정환(Junghwan Lim) 한국자동차공학회 2006 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
The requirements of truck customers have been increased to transport their precious and fragile freights safely with rising industry volume of high-price and fragile goods. Air suspension trucks are liable to decrease the amplitude of vibrations by using its own characteristics of air spring. These air spring characteristics also have a benefit of keeping low natural frequency under load variations. Moreover. air suspension trucks are capable of having relatively constant vehicle height by controlling the air pressure under kerb and G.V.W load conditions. In this paper, the influences of an air suspension system on freight protection have been studied. To analyze those effects, vertical acceleration at the frame of the air suspension vehicle and the leaf suspension vehicle have been measured and compared.
대형버스의 루프 진동에 영향을 미치는 인자에 관한 연구
국종영(Jongyoung Kuk),박종찬(Jongchan Park),임정환(Junghwan Lim) 한국자동차공학회 2006 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
If the vibration is occurred at large-sized bus roof, it makes people annoying and complaining the quality of vehicle. In design stage, it must be considered. To assess vibration at roof which is equipped with air conditioner in design stage, FE-model is constructed. Computer simulation analysis and test is performed. The dynamic characteristics of bus are found by using eigenvalue method. It is related with dynamic behavior. The running conditions of bus are velocity and road condition which followed test condition. And the frequency response of vehicle is well correlated with analysis result. Modal participation method is used for finding major modes at each peak. Front and rear suspension spring, engine mounting stiffness are selected for modal contribution. To reduce vibration level of front and rear suspension spring, engine mounting stiffness are properly combined. From this study, the vibration level is lowered at roof.
유연 다물체 동역학 모델을 이용한 판스프링의 이력현상 및 동응력해석
문일동(Ildong Moon),김기태(Gitae Kim),임정환(Junghwan Lim),오재윤(Chaeyoun Oh) 한국자동차공학회 2006 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
This paper proposes a modeling technique which is able to not only reliably and easily represent the hysteretic characteristic but also analyze the dynamic stress of a taper leaf spring. The flexible multi-body dynamic model of the taper leaf spring is developed by interfacing the finite element model and computation model of the taper leaf spring. Rigid dummy parts are attached at the places where a finite element leaf model is in contact with an adjacent one in order to apply contact model. Friction is defined in the contact model to represent the hysteretic phenomenon of the taper leaf spring. The test of the taper leaf spring is conducted for the validation of the reliability of the flexible multi-body dynamic model of the taper leaf spring developed in this paper. The test is started at an unloaded state with the excitation amplitude of 1-2㎜/sec and frequency of 132㎜. First, the simulation is conducted with the same condition as the test. Then, the simulations are conducted with various amplitudes in a loaded state. The hysteretic diagram from the test is compared with the ones from the simulation for the validation of the reliability of the model. The dynamic stress analysis of the taper leaf spring is also conducted with the developed flexible multi-body dynamic model under a dynamic loading condition.