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김홍집,손채훈,정석호,Kim, Hong Jip,Sohn, Chae Hoon,Chung, Suk Ho 대한기계학회 1999 大韓機械學會論文集B Vol.23 No.1
Reignition as special cases of acoustic pressure responses of flame are numerically studied by employing methanol droplet flame as a laminar flamelet. Quasi-steady flame responses occur in the range of small amplitude, low frequency oscillation. Reignition phenomena can occur when, by increasing the frequency of large amplitude acoustic pressure, the magnitude of characteristic acoustic time is the same order of that of characteristic reaction time of flames. And more increasing of amplitude of acoustic pressure induces the direct extinction of flame. Flame can sustain its own intensity even under the steady extinction temperature in case of high frequency acoustic oscillation, and this tendency is remarkable with increasing frequency. Reignition regime with respect to amplitude and frequency of acoustic pressure doesn't exist in low frequency($10^2$ Hz, in this study), but broadens with frequency of acoustic pressure.
수소/공기 대향류 확산화염의 비선형 음향파 응답특성에 관한 연구
김홍집,정석호,손채훈,Kim, Hong-Jip,Chung, Suk-Ho,Sohn, Chae-Hoon 대한기계학회 2003 大韓機械學會論文集B Vol.27 No.8
Steady-state structure and acoustic-pressure responses of $H_2$/Air counterflow diffusion flames are studied numerically with a detailed chemistry in view of acoustic instability. The Rayleigh criterion is adopted to judge acoustic amplification or attenuation from flame responses. Steady-state flame structures are first investigated and flame responses to various acoustic-pressure oscillations are numerically calculated in near-equilibrium and near-extinction regimes. The acoustic responses of $H_2$/Air flame show that the responses in near-extinction regime always contribute to acoustic amplification regardless of acoustic-oscillation frequency Flames near extinction condition are sensitive to pressure perturbation and thereby peculiar nonlinear responses occur, which could be a possible mechanism in generating the threshold phenomena observed in combustion chamber of propulsion systems.
우군 건강관리를 위한 체중측정, 체형 크래프, 산유량 분포도, 대사프로필 검색의 활용
김홍집 ( Hong Jip Kim ),은길수 ( Gil Soo Eun ),강병선 ( Byung Sun Kang ),이재규 ( Jae Kue Lee ),김정환 ( Jung Han Kim ),송희종 ( Hee Jong Song ) 한국가축위생학회 2001 韓國家畜衛生學會誌 Vol.24 No.3
The change of the body condition score(BCS) and milk production graph as days in milk by lactation number show that the productivity of cow is on the increase as increase the lactation number, but the health condition is much worse because of the inappropriate nutrition intake. Metabolic profiles test(MPT) results indicate that the early-lactation for directly after the parturition to the peak production of milk during the total lactation period is the time of the more likely to be exposed to lack of energy, protein, minerals. To solve this problem, the early-lactation cows should be sufficiently supplied the required nutrients and should maximum intake the supplied nutrients not to be suddenly decline body weight and BCS from post parturition to the peak production of milk. To maximize the dry matter intake of a cow, there is Have got to improve the management of body weight for heifer`s skeletal development and in the dry period which is carelessly deal by mostly farms. This study presents that the use of measurement of body weight, graph of body condition score, distribution of milk production, metabolic profiles test in the monitoring for dairy herd health management is very valuable.
채널의 분기 및 병합이 있는 액체로켓 연소기 재생냉각 유로에서의 수력학적 특성
김홍집(Hong Jip Kim),김성구(Seong-Ku Kim),최환석(Hwan Seok Choi) 한국항공우주학회 2008 韓國航空宇宙學會誌 Vol.36 No.11
고성능 로켓엔진용 연소기에서 열적 건전성을 확보하기 위해 적용되는 재생냉각 채널은 채널의 분기/병합, 방향 전환과 같이 복잡한 유동구조를 포함한다. 냉각유로에서 발생하는 압력 손실을 마찰과 국소유통저항으로 나눠, 각각의 유통조건에 따라 경험적으로 제시된 문헌상의 계수를 적용함으로써, 재생냉각유로 설계에 효과적으로 적용할 수 있도록 수력학적 자료를 구하였다. 해석의 타당성을 검증하기 위하여 실물형 연소기의 냉각유로 설계안에 적용하였다. 먼저, 물을 사용하였을 때 모사시제를 사용한 수류시험 결과와 비교하였다. 정량적으로 타당한 결과를 얻은 것으로 확인되어, 실유체인 케로신을 사용한 수력해석을 수행하여 CFD 결과와 비교하여 수력해석 방법의 타당성을 확인할 수 있었다. Regenerative cooling passage to guarantee the thermal survivability in high performance rocket engine combustors could have complex configurations of the branching/merging of channels and flow turning, etc. By applying the classical hydraulic coefficients which can be found in the literature according to the flow conditions, hydraulic characteristics in regenerative cooling passages can be obtained effectively through dividing the pressure loss into friction loss and local resistance loss. Satisfactory agreement has been obtained by comparing the present results with experimental measurement of water flow test. In addition, the present results were in good agreement with CPD results when the actual coolant, kerosene was used. Therefore, the application of the present method is expected to be useful to design regeneratively cooled combustors.
김홍집(Hong Jip Kim),이광진(Kwang Jin Lee),서성현(Seonghyeon Seo),김승한(Seung Han Kim),한영민(Yeoung Min Han),설우석(Woo Seok Seol) 한국항공우주학회 2005 韓國航空宇宙學會誌 Vol.33 No.1
KSR-Ⅲ 개발과정에서 배플을 장착하여 연소 불안정 현상을 해결한 바 있으나, 추력 및 냉각과 관련된 축방향 길이에 대한 최적화 과정을 거치지는 않았다. 이에 수동제어기구로서 사용되는 배플의 축방향 길이의 최적화 및 한계를 평가하기 위하여, 축방향 길이를 작동인자로 하여 연소 안정성 여분을 평가하였다. 외부 교란 발생 장치로서 2번의 기폭이 가능한 펄스건을 사용하였다. 외부 교란에 대한 연소실에서의 응답 특성을, 감쇠 시간과 진폭비와 같은 인자를 도입하여 정량화하였다. 설계점과 탈설계점에서 시험을 수행하였으며, 분사기의 충돌점으로 생각할 수 있는 화염 영역을 감싸지 못하는 경우에는 배플의 충분한 감쇠 능력을 보장할 수 없음을 확인하였다. 따라서 연소 안정성의 여분의 경계는 KSR-Ⅲ에서의 작동조건 하에서 50 ㎜ 정도의 배플인 것으로 판단되었다. To optimize and limit the axial length of the baffle of the KSR-Ⅲ engine, stability rating tests using pulse gun as one of artificial disturbance devices have been done. Generally a rocket engine can be considered to be dynamically stable if a certain imposed external perturbation or pressure oscillation in rocket combustion chamber could be suppressed within a short time period. Decay time and other parameters for the evaluation of stabilization ability of an engine to external perturbation have been analyzed to quantify stabilization capacity of engine, in other words, dynamic stability margin. Baffle not covering flame zone enough which can be considered as collision region of injector wasn't be able to suppress external perturbation sufficiently. The limit of combustion stability margin of engine is assumed to be 50 ㎜ length baffle of the KSR-Ⅲ engine.