• Journal of the KSME
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• v.34 no.4
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• pp.225-238
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• 1994

엔진의 연소에 중요한 영향을 미치는 가스 유동장의 해석을 위하여 현재 주로 사용되고있는 광 응용 계측기술에 대하여 소개하였다. 소개한 예에서 알 수 있는 바와 같이 점계측을 기초로 하는 정량계측만으로는 유동장전체를 파악하기엔 부족한 감이 있으며, 정성적일 뿐만 아니라 또한 정량적인 해석까지도 가능하게 하는 가시화수법을 추구하게 되는 일련의 움직임이 보여지고 있다. 여기서 소개한 예 이외에도 엔진 내의 유동장해석에는 많은 다른 방법들이 적용되고 있 으며, 지금 이 순간에도 보다 더 차원성이 높고 시간과 공간분해능이 우수한 새로운 광응용 계 측기술들이 개발 중에 있다고 하겠다. 이와 같은 광응용 계측기술의 진보야말로 차세대 엔진개 발을 위한 중요한 역할을 담당하게 되리라는 확신과 기대를 가져도 좋으리라 여겨진다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1998.10a
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• pp.13-13
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• 1998

램가속기의 발진 과정에서 유동장 내에는 수백 기압 이상의 고압 영역이 존재하며 이러한 영역에서는 이상기체 가정이 더 이상 유효하지 않게 된다. 따라서 램가속기 작동조건에 적용 가능한 적절한 형태의 실제 기체 상태 방정식이 요구된다 또한 기존의 온도에 종속적인 Arrhenius 형태의 기초 반응들로 이루어진 축소 화학 반응 모델은 상압 조건하에서 적용 가능하므로 고압 화경에서 적용하기 위해서는 온도뿐 아니라 압력에 종속적인 형태의 반응율 상수가 도입되어야 한다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.3
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• pp.507-514
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• 2009

Large eddy simulation code was developed to predict the turbulent flows over backward-facing steps including a recirculating flow phenomena. Localized dynamic ksgs-equation model was employed as a LES subgrid model and the LES solver was implemented on parallel computer consisting of 16 processors to reduce computational costs. The results of laminar flow showed qualitative and quantitative agreements between current simulations and experimental results availablein literatures. The simulation of the turbulent flows also yielded reasonable results. From these results, it can be expected that developed LES code will be very useful to analyze the combustion in stabilities and noise of a practical combustor in the future.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.47 no.10
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• pp.720-727
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• 2019

Resonating thermal lags of solid fuel with heat transfer oscillations generated by boundary layer oscillation is the primary mechanism of the occurrence of the LFI (Low Frequency Combustion Instability) in hybrid rocket combustion. This study was experimentally attempted to confirm that how the boundary layer was perturbed and led to the LFI. Special attention was also made on oxidizer swirl injection to investigate the contribution to combustion stabilization. Also the overall behavior of fluctuating boundary layer flow and the occurrence of the LFI was monitored as swirl intensity increased. Fluctuating boundary layer was successfully monitored by the captured image and POD (Proper Orthogonal Decomposition) analysis. In the results, oscillating boundary layer became stabilized as the swirl intensity increases. And the coupling strength between high frequency p', q' diminished and periodical amplification of RI (Rayleigh Index) with similar frequency band of thermal lag was also decreased. Thus, results confirmed that oscillating axial boundary layer triggered by periodic coupling of high frequency p', q' is the primary mechanism to excite thermal resonance with thermal lag characteristics of solid fuel.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.48 no.8
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• pp.589-595
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• 2020

Large eddy simulation (LES) of a partially premixed gas turbine combustor is conducted. Four different hydrogen compositions are considered to investigate the fuel composition effects on the flow field inside the combustor. The comparison with the experimental flame structure and velocity profile is conducted to verify the LES results, revealing that the partially premixed flame structure is altered when hydrogen composition is changed. The flame structure becomes shorter and thicker as the hydrogen composition is increased, and therefore, the flame effect in the rigid wall is minimized. The change in the recirculation zone at the combustor wall with hydrogen addition is further investigated. Overall, the LES with combustion model is quite promising for accurately predicting the reactive flow characteristics in connection with the fuel composition.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.1
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• pp.97-103
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• 2003

Numerical research has been done for the transverse jet behind a rearward-facings step in turbulent supersonic flow without chemical reaction. Purpose of transverse jet is to enhance mixing of the fuel in the combustor. Two-dimensional unsteady flowfields generated by slot injection into supersonic flow are numerically simulated with the Navier-Stokes equations with two-equation k-$\varepsilon$ turbulence model. Numerical method is used high-order upwind TVD scheme. Eight cases are computed for different slot momentum flux ratios and slot position at downstream of the step. The flow is very similar to the cavity flow, because the jet acts as an obstacle. The numerical results thus show the periodic phenomenon.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1997.11a
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• pp.17-17
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• 1997

극초음속 여객기와 군사용 항공기에 대한 수요가 증가함에 따라서 새로운 개념의 다양한 추진기관이 연구가 진행되고 개발되어 왔다. 초음속 항공기의 속도 영역은 마하 10-20 정도가 되는데 이 속도 한계를 극복하기 위하여 초음속 연소 램제트 엔진(SCRamjet; Supersonic Combustion Ramjet)이 제안되었다. 스크램 제트를 개발하기 위해서는 연료와 산화제의 혼합 효율 문제, 화염의 안정화 문제, 벽면의 냉각에 관한 문제 등 몇 가지 기본적인 문제들을 해결해야 한다. Univ of Michigan에서 실험한 연소기를 모델로 본 연구에서는 연료와 공기의 혼합에 관한 수치 연구를 수행하였다. 다원 혼합기체에 관한 축대칭 Navier-Stokes 방정식을 지배 방정식을 이용하였고 비평형 화학반응식을 고려하였다. 공간 차분에는 유한 체적법을 이용하였다. 대류 플럭스 항은 Roe의 Upwind FDS 기법을 사용하여 차분하였고 점성항에는 중심 차분법을 이용하였다. 시간 적분법으로는 근사 자코비안과 LU분할 기법을 이용한 완전 내재적 방법이 쓰였다. 난류 모델로는 Mentor에 의해 제안된 2 방정식 k-$\varepsilon$/k-$\omega$ 혼합모델을 사용하였다. 유동장이 실험에서의 찍은 사진과 유사한 모습의 충격파 간섭을 수치 모사하였고 수소가 확산되는 모습과 함께 노즐 lip 주위의 재순환 영역에 대해서 살펴볼 수 있었다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.1
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• pp.95-104
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• 2002

A two color PIV technique has been developed for visualization of complex and high speed flow in a ramjet combustor. Two color PIV has the advantages that velocity distribytions in high speed flowfields can be measured simply by varying the time interval between two different laser beams and a directional ambiguity problem can be solved by color separation, and then a singnal-to-noise ratio can be increased through nearly perfect cross-correlation. As a basic research of the ramjet engine, a 2-D shaped combustor with two symmetric air intakes has been manufactured and an experimental study has been conducted using a two color PIV technique. The flow characteristics such as recirculation zones and two intake air mixing have been investigated varying inlet angles and dome heights. It is found that the size and air mass ratio of reciculation zones are affected mainly by an inlet angle, but not much by a dome height.

• 한국연소학회:학술대회논문집
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• 2012.04a
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• pp.263-266
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• 2012

The characteristics of mild combustion and pollutant emission were investigated computationally with supplied air stream temperature and dilution rate in jet flame. The air was diluted with main combustion products. As dilution rate increased at fixed air temperature, the temperature distribution of burner inside was uniformed and the maximum mole fraction of CO and NO was decreased. In addition, emission indices for NO, CO, and $CO_2$ were compared with air temperature and dilution rate.

• 한국연소학회:학술대회논문집
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• 2015.12a
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• pp.301-304
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• 2015

With the experiment observation of single particle combustion, this model is built for the numerical analysis of the process. It's about the single coal particle combustion process under different conditions with reasonable assumptions. The model can express the mass, radius, density, temperature changing with different particle sizes, oxygen concentration and gas temperature. It also includes the flame sizes change in different condition and the diffusion of each species. The result shows the characters of the combustion.