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분위기 온도에 따른 충돌 분무의 거동에 대한 실험 및 수치적 연구
심영삼,최경민,김덕줄,Shim, Young-Sam,Choi, Gyung-Min,Kim, Duck-Jool 한국자동차공학회 2007 한국 자동차공학회논문집 Vol.15 No.4
The numerical study on behavior of impinging spray from high-pressure swirl injector under various ambient temperatures was performed by using spray vaporization model and spray-wall impingement model implemented in modified KIVA code, and these spray models were estimated by comparison with experimental results. To compute the spray-wall impingement process, the Gosman model, which is based on the droplet behavior after impingement determined by experimental correlations, was used. The modified Abramzon and Sirignano model, that includes the effects of variable thermodynamic properties and non-unitary Lewis number in the gas film, was adapted for spray vaporization process. The exciplex fluorescence measurements were also conducted for comparison. The experimental and numerical analysis were carried out at the ambient pressures of 0.1 MPa and at the ambient temperature of 293 K and 473 K, and the spray characteristics, such as spray-wall impingement process, gas velocity field, SMD and vapor concentration, were acquired. It was found that the impinging spray develops active and SMD is small at vaporization conditions.
심영삼 연세대학교 통일연구원 2002 통일연구 Vol.6 No.1
Since Kim Jung-il's regime set out in 1994, international academic community on North Korea has debated the regime instability of North Korea. But in contrast to the consistent pessimistic evaluation, North Korea has consolidated its regime with relative stability, despite its severe famine and downward economic growth. Given the relationship between Kim's regime stability and North Korea's military build-up, this paper analyzes the source of North Korea's regime stability. One of the most conspicuous changes in North Korea since the mid-1990s is its renewed emphasis on the military build-up. Although it has consistently been inflicted by the economic decline, the North has invested a large sum of money as much as 20% of its GDP in military. This means that North Korea has been depended its regime consolidation on the military build-up and that its ideological basis of foreign relations has also been buttressed by the military. As we've witnesses during the 1999 naval clash between the North and the South in the Yellow Sea, the North's military equipment and weapons are not in the status as qualified as worth threatening Korea. But the South's superiority in military equipment and weapons does hardly defend itself from the North's suspected military threat. Because the North's most advantages in terms of military operation are simplified decision-making structure and unified policy implementation. Generally, North Korean decision making structure is solely dominated by Kim Jung-il Himself, which relieves itself from public opinion. Thus, the North has a potential capability to outweigh the South in case of regional military conflict, which is highly possible with effective military build-up. Another function of the North's military build-up comprises making up the gaps in national power between the South and the North. Since the introduction of "e Four Principles of Military Development"n 1962, North Korea has improved its military capability in systemic fashion. Emphasizing the nationalistic quality of sense, the North's leadership has trained and maintained its military in line with Juche ideology. Reviewing "ur Principles of Military Development," the modernization of armament, the fortification of entire territory, the officer-ization of entire forces, and the arming of entire populace, I found that the priority among each category has been shifted in accordance with time and situation. Since it perceives that the major causus belli would be the maintenance of Kim's regime, the North leadership put the modernization of armament as a top priority. Thus that Kim himself seems to focus on military build-up makes very much sens from North Korean perspective. This paper intends to analyze the implicit role of North Korean military build-up by ways of reviewing materials published both in domestic and international settings between 1962 and 2002. It also refers the direct interviews with North Korean refugees who had served in North Korean military while they were in the North. For supporting my argument, I thoroughly analyzed the military equipment and armament in North Korean army, navy, and air forces as well as its military capability in terms of numbers. It proves that the North's strategists attempt to upgrade its armament for sustaining its military superiority over the South and helping its negotiation with the US to its favor.
GDI 엔진용 고압 스월 인젝터의 초기 및 주 분무에 대한 수치적 연구
심영삼(Youngsam Shim),최경민(Gyungmin Choi),김덕줄(Duckjool Kim) 한국자동차공학회 2005 한국자동차공학회 춘 추계 학술대회 논문집 Vol.2005 No.11_1
The objective of this study is to analyze the pre spray and the main pray ofa high pressure swirl injector for GDI injector by using a hybrid breakup model. The hybrid breakup model is composed of Linearized Instability Sheet Atomization (LISA) model and Aerodynamically Progressed Taylor Analogy Breakup (APTAB) model. The LISA model was used for primary breakup process and the APTAB model was used for secondary breakup process. The spray model was incorporated in three-dimensional computational fluid dynamic code (KIVA code). The exciplex fluorescence method was used for comparing the calculated results with the experimental ones. The experiment and the calculation were performed at the ambient pressures of 0.1 ㎫ and 0.5 ㎫ and the ambient temperature of 293K.
벽면 캐비티 각에 따른 GDI 분무의 벽 충돌 과정에 대한 수치적 연구
심영삼(Young-Sam Shim),최경민(Gyung-Min Choi),김덕줄(Duck-Jool Kim) 대한기계학회 2007 大韓機械學會論文集B Vol.31 No.12
A spray-wall impingement process of a hollow-cone fuel spray from the high-pressure swirl injector in the Gasoline Direct Injection (GDI) engine were experimented and calculated at various wall geometries. The Linearized Instability Sheet Atomization (LISA) & the Aerodynamically Progressed Taylor Analogy Breakup (APTAB) model and the Gosman model were applied to model the breakup and the wall impingement process of the hollow-cone fuel spray. The numerical modelings were implemented in the modified KIVA code. The calculation results of spray characteristics, such as a spray development process and a radial distance after wall impingement, compared with the experimental results by the Laser Induced Exciplex Fluorescence (LIEF) technique. The droplet size distribution and the ambient gas velocity field, which are generally difficult to obtain by the experimental methods, were also calculated and discussed. It was found that the radial distance after wall impingement and Sauter Mean Diameter (SMD) decreased with increasing a cavity angle.
GDI 분무의 벽 충돌 과정에 대한 실험 및 수치적 연구
심영삼(Youngsam Shim),최경민(Gyungmin Choi),김덕줄(Duckjool Kim) 한국자동차공학회 2006 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
Experimental and numerical analysis about atomization and wall impingement process of hollow-cone fuel spray is performed by hybrid model and wall impingement model. The atomization process is modeled by using hybrid breakup model that is composed of Linearized Instability Sheet Atomization (LISA) model and Aerodynamically Progressed Taylor Analogy Breakup (APTAB) model. The Gosman model, which is based on the droplet behaviors after impingement determined by experimental correlations, is used for spray-wall impingement process. The LIEF technique was used to compare the results with those of experiment. The calculations and experiments are carried out at the ambient pressures of 0.1㎫ and 0.5㎫ and the ambient temperature of 293K.