• 한국연소학회:학술대회논문집
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• 한국연소학회 2005년도 제31회 KOSCO SYMPOSIUM 논문집
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• pp.28-31
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• 2005

The numerical simulation is conducted for analysis flame structure of superdetonative ram accelerator experiment by ISL(French-German Research Institute in Saint Louis). Fully coupled chemically non-equilibrium Navier-Stokes equation is used. Shockwave structure of superdetonative ram accelerator and behavior of detonation wave is studied. Maintaining of detonation wave is very important to accelerate projectile, Because detonation wave make high pressure gases and this high pressure accelerate projectile.

• 한국연소학회지
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• 제12권4호
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• pp.31-38
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• 2007

An numerical study was conducted on superdetonative mode ram accelerator with length extended combustor. The computation condition was based on ISL's RAMAC30 II S225 experiment. For 50% length increased combustor, flame is not sustained. For the case of 60% and 70% increase, flame is successfully sustaind. But detonation wave is oscillating and acceleration is fluctuating. Extention of combustor is helpful for sustaing detonation wave but it may cause unstart.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2007년도 제34회 KOSCO SYMPOSIUM 논문집
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• pp.126-129
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• 2007

An numerical study was conducted on superdetonative mode ram accelerator with extended combustor. The computation case was based on ISL's RAMAC30 II experiment. For 50% length increased combustor, flame is not sustained. For the case of 60% and 70% increase, flame is successfully sustaind. But detonation wave is oscillating and acceleration is fluctuating. Increasing of combustor length is helpful for sustaing detonation wave but it may cause unstart.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2013년도 제46회 KOSCO SYMPOSIUM 초록집
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• pp.77-80
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• 2013

An analytical study on performance of superdetonative mode ram accelerator was conducted for understanding the S225 experimental result of ISL. It would be noticeable that ISL S225 experimental result could be analytically simulated with the assumptions of inlet shockwave, equilibrium combustion chemistry, temperature dependent specific heat, and C-J oblique detonation in superdetonative operation mode. As result, the S225 experiment could be affected by heat of aluminum. Also, this study showed that the improper assumption, like isentropic assumption on shockwave, or constant specific heat on combustion, might cause misunderstanding about experimental result.

• 한국연소학회지
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• 제19권1호
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• pp.1-10
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• 2014

An analytical study on performance evaluation of superdetonative mode ram accelerator was conducted for understanding the experimental result. The quasi-one dimensional continuum, momentum, energy equations were solved under the assumption of inviscid flow. It would be noticeable that experimental result could be analytically simulated with the assumptions of inlet shockwave, temperature dependent specific heat, and additional aluminum combustion due to ablation of aluminum projectile in superdetonative operation mode. The acceleration of ram accelerator was comparable to experimental result with the consideration of the additional aluminum combustion energy by ablation of projectile. As result, the experimental result with the aluminum projectile could be affected by heat of aluminum.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 1999년도 추계 학술대회논문집
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• pp.77-84
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• 1999

Numerical design optimization techniques are implemented for the improvement of the ram accelerator performance. The design object is to find the minimum ram tube length required to accelerate projectile from initial velocity $V_0$ to target velocity $V_e$. The premixture is composed of $H_2,\;O_2,\;N_2$ and the mole numbers of these species are selected as design variables. The objective function and the constraints are linearized during the optimization process and gradient-based Simplex method and SLP(Sequential Linear Programming) have been employed. With the assumption of two dimensional inviscid flow for internal flow field, the analyses of the nonequilibrium chemical reactions for 8 steps 7 species lave been performed. To determined the tube length, ram tube internal flow field is assumed to be in a quasi-steady state and the flow velocity is divided into several subregions with equal interval. Hence the thrust coefficients and accelerations for corresponding subregions are obtained and integrated for the whole velocity region. With the proposed design optimization techniques, the total ram tube length had been reduced $19\%$ within 7 design iterations. This optimization procedure can be directly applied to the multi-stage, multi-premixture ram accelerator design optimization problems.

• 한국추진공학회지
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• 제3권2호
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• pp.82-91
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• 1999

초폭굉 램 가속기의 탄체 형상은 탄체 주위에 형성되는 충격파의 구조 및 데토네이션파의 생성, 그리고 탄체의 가속 특성에 커다란 영향을 주게 된다. 본 연구에서는 초폭굉 모드의 기본 탄체 형상인 원추-원퉁-원추의 전.후면 반 꼭지각의 변화와 이중 원추, 그리고 Power-Law 형상 등의 탄체 전면 형상의 변화가 탄체 주위의 유동장, 데토네이션파의 형성 과정, 그리고 탄체 가속 특성에 미치는 영향을 수치적으로 해석하였으며, 이중 원추면의 높이와 각도를 변화시킴으로써 전.후면 반 꼭지각이 $10^{\cire}$인 ISL의 기본 형상에 비하여 약 31.0%의 향상된 가속 성능을 갖는 램 가속기 탄체 형상을 도출하였다. 이러한 탄체 가속 특성 연구 결과는 향후 램 가속기에 대한 설계 최적화 연구에 유용한 자료로 이용 될 것이다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년도 제30회 춘계학술대회논문집
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• pp.244-247
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• 2008

ISL의 초폭굉 모드 램 가속기 실험을 바탕으로 하여 혼합기 강도를 조정하여 수치해석을 수행하였다 ($3.0CO_2$ 희석과 $2.5CO_2$ 희석). 계산결과 $3.0CO_2$ 희석의 경우는 초기 점화가 이루어지지 않아 탄체가 가속되지 않은 반면 $2.5CO_2$ 희석을 한 경우에는 점화가 이루어지고 높은 가속을 보임을 알 수 있었다. 이것은 탄체의 가속성능이 혼합기의 강도에 단순히 비례하지 않으며 점화가 가능한 최소한의 혼합기 강도 이상에서만 초폭굉 모드 램 가속기가 정상적으로 작동함을 알 수 있었다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년 영문 학술대회
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• pp.519-524
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• 2008

A numerical study is conducted to investigate propulsion performance enhancement based on S225 experiment case of ISL(French-German Research Institute of Saint-Louis)'s superdetonative ram accelerator. For govern equation, multi-species Navier-Stokes equation coupled with Baldwin-Lomax turbulence modeling is used. Govern equation is discretized by Roe's FDS and integrated by LU-SGS time integration. Detailed chemical reaction about $H_2/O_2/CO_2$ for high pressure is considered. $2H_2+O_2+2.5CO_2$ mixture was used for propellant gas. For the same over-driven factor, the launching speed of computation was faster than one of S225. Another configuration and condition of S225 was applied. A flame structure is very different from S225. For strong mixture case, it shows ignition by viscous effect. Acceleration and speed increment is higher than S225 computation and experiment. By using more strong mixture, propulsion performance was enhanced.

• 한국전산유체공학회지
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• 제5권2호
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• pp.55-63
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• 2000

In this paper, the numerical study has been done for the improvement of the superdetonative ram accelerator performance and for the design optimization of the system. The objective function to optimize the premixture composition is the ram tube length, required to accelerate projectile from initial velocity V/sub 0/ to target velocity V/sub e/. The premixture is composed of H₂, O₂, N₂ and the mole numbers of these species are selected as design variables. RSM(Response Surface Methodology) which is widely used for the complex optimization problems is selected as the optimization technique. In particular, to improve the non-linearity of the response and to consider the accuracy and the efficiency of the solution, design space stretching technique has been applied. Separate sub-optimization routine is introduced to determine the stretching position and clustering parameters which construct the optimum regression model. Two step optimization technique has been applied to obtain the optimal system. With the application of stretching technique, we can perform system optimization with a small number of experimental points, and construct precise regression model for highly non-linear domain. The error compared with analysis result is only 0.01% and it is demonstrated that present method can be applied to more practical design optimization problems with many design variables.