Aluminum-Copper(II) Oxide Composite의 정전기에 의한반응 특성 연구

김민준,김성호,김자영,임예슬 한국군사과학기술학회 2018 한국군사과학기술학회지 Vol.21 No.5

The reaction characteristics of aluminum-copper(II) oxide composites initiated by the electrostatic discharge were studied as changing the aluminum particle size. Three different sizes of aluminum particles with nano-size copper(II)-oxide particle were used in the study. These composites were manufactured by two methods i.e. a shock-gel method and a self-assembly method. The larger aluminum particle size was, the less sensitive and less violent these composites were based on the electrostatic test. On the analysis of high speed camera about ignition appearances and burning time, the burning speed was faster when aluminum particle size was smaller.

Experimental investigation of the effects of paraffin/aluminum blended fuels on aluminum particle size

한성주,문희장 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.6

The combustion behavior of paraffin/aluminum blended fuels was investigated to determine the effects on the size of nano- and microsized aluminum particles and assess their respective combustion performance in hybrid rocket applications. The base paraffin fuel considered in this study was Sasol 0907 microcrystalline wax. Two additional blended fuels, each with particles with average sizes of 8 µm and 100 nm were used. The thermal and rheological behavior of the paraffin/aluminum blended fuels were evaluated, and their homogeneity was verified by scanning electron microscopy. Results confirmed that the nano-sized and micro-sized particles were well distributed in space without agglomeration. The average regression rate of the paraffin added with micro-sized particles was higher than that of the case with nano-sized particles mainly because of the strong viscosity of the nanofuel. This result was justified by the augmented average chamber pressure of the micro-sized paraffin fuel. Generally, the characteristic velocity of the microfuel was greater than that of the nanofuel for the overall range of the oxidizer-to-fuel ratio considered in this study. This difference became pronounced as the oxidizer mass flux increased. The characteristic velocity efficiency of the two blended fuels (microfuel and nanofuel) merely showed a notable difference in the oxidizer-to-fuel ratio range, except for the particle-free base fuel, which showed a wide scatter of combustion efficiency probably because of its low melt layer viscosity, which leads to an undesirable high entrainment of non-combusted pure paraffin fuel.

레이저를 이용한 마이크로/나노 알루미늄 입자 생성과 점화

이경철(Kyung-Cheol Lee),여재익(Jai-ick Yoh) 한국추진공학회 2012 한국추진공학회 학술대회논문집 Vol.2012 No.5

금속 연료로 사용되는 마이크로/나노 알루미늄 입자를 산화피막에 의한 점화 지연을 최소화 하는 점화 방법을 제시 하였다. 알루미늄 입자를 생성시킴과 동시에 가열하여 입자가 생성된 직후 산소와 접촉시 격렬한 산화 반응을 유도하여 점화를 시키는 방법이다. 1064 ㎚ 파장의 Nd:YAG 펄스 레이저를 이용한 레이저 삭마(laser ablation)를 알루미늄 시편에 발생시켜 입자를 생성하였으며, 산란 기법(scattering method)을 이용하여 입자를 가시화하여 생성을 확인하였다. 10.6 ㎛ 파장의 CO₂ 연속 레이저를 사용하여 알루미늄 시편을 가열하고 생성된 입자의 점화 열원으로 사용하여 알루미늄 입자가 점화되고 연소되어 이동하는 궤적을 확인하였다. Ignition delay of micro/nano aluminum particles is caused by aluminum oxide shell. The method of minimizing this ignition delay is proposed in the study. Generating and heating of particles are processed at the same time. As soon as heated particles are produced, they immediately contact with oxygen. Chemical reaction is induced on the contact surface instead of crystallization of oxide shell. Finally particles are ignited. Aluminum particles are generated by laser ablation on an aluminum plate using Nd:YAG pulse laser. Injected particles are confirmed through visualization of particles using scattering method. CO₂ continuous laser supplies heat to aluminum plate and generated particles. Trace of burning particles is observed in the experiment.

Simplified Modeling of an Aluminum Paricle Combustion

Heesung Yang,Jihwan Lim,Jihyung Lee,Kyungmoo Kim,Woongsup Yoon 한국항공우주학회 2008 한국항공우주학회 학술발표회 논문집 Vol.- No.-

A simplified model for an isolated aluminum particle burning in air is presented. Burning process consists of two stages, ignition and quasi-steady combustion (QSC). It is assumed that an initial aluminum particle is covered with oxide film. and film thickness is calculated using phase diagram of Al-O and lever rule. Heterogeneous surface reaction (HSR) as well as heat transfer from ambient air is considered for the heat source of ignition. In quasi-steady combustion stage, gas phase reaction occurs so that diffusion flame is assumed. For simplicity, I-dimesional spherical symmetric condition and flame sheet assumption are also used Extended conserved scalar formulations and modified Shvab-Zeldovich functions are used to account for the deposition of metal oxide on the surface of the molten aluminum. Using developed model, time variation of particle temperature, masses of molten aluminum and deposited oxide are predicted. Burning rate, combustion time, flame radius and temperature are also calculated. and compared with some experimental data.

단일 알루미늄 연료 입자의 점화 및 연소 모델링

양희성(Heesung Yang),임지환(Jihwan Lim),김경무(Kyungmoo Kim),이지형(Jihyung Lee),윤웅섭(Woongsup Yoon) 한국추진공학회 2008 한국추진공학회 학술대회논문집 Vol.2008 No.5

A simplified model for an isolated aluminum particle burning in air is presented. Burning process consists of two stages, ignition and quasi-steady combustion (QSC). In ignition stage, aluminum which is inside of oxide film melts owing to the self heating called heterogeneous surface reaction (HSR) as well as the convective and radiative heat transfer from ambient air until the particle temperature reaches melting point of oxide film. In combustion stage, gas phase reaction occurs, and quasi-steady diffusion flame is assumed. For simplicity, 1-dimesional spherical symmetric condition and flame sheet assumption are also used. Extended conserved scalar formulations and modified Shvab-Zeldovich functions are used that account for the deposition of metal oxide on the surface of the molten aluminum. Using developed model, time variation of particle temperature, masses of molten aluminum and deposited oxide are predicted. Burning rate, flame radius and temperature are also calculated, and compared with some experimental data.

Eulerian-Lagrangian 기반 군집 알루미늄 연소의 격자 의존성 연구

한두희,성홍계 한국항공우주학회 2015 한국항공우주학회 학술발표회 논문집 Vol.2015 No.11

본 연구는 고 에너지 물질인 군집 알루미늄 입자 연소에 대한 수치적 모델링 및 격자 의존도 계산을 수행 하였다. Eulerian-Lagrangian 기법을 사용하여 군집 입자의 연소현상을 모사하였다. 공기-알루미늄 혼합물이 채워져 있는 사각 관내에서 화염 전파속도를 계산하여 격자 의존성을 계산하였고, 입자보간법 및 공간 차분법에 따라 격자 수렴성이 영향을 받는 것을 확인 하였다. Numerical analysis on dust combustion of cloud aluminum particles has been conducted using Eulerian-Lagrangian method. The purpose of this study is suggesting the results of grid dependency tests. The dust combustion has been simulated using the combustion of pre-mixed aluminum-air mixture in a square duct. A grid dependency with a different order of space discretization and a particle interpolation was suggested. 4th order central discretization with a particle interpolation method showed a most reduced grid dependency in a Eulerian-Lagrangian aluminum flame propagation.

변형률 구배 소성을 고려한 입자 강화 알루미늄 복합재의 크기 종속 강화 모델링

서영성(Yeong Sung Suh),박문식(Moon Shik Park),송승(Seung Song) 대한기계학회 2011 大韓機械學會論文集A Vol.35 No.7

입자강화 알루미늄 복합재의 강도를 계산하기 위하여 압밀 후 냉각할 때 일어나는 전위 펀칭을 유한요소로 모델링 하였다. 다양한 입자의 체적비에서 입자의 크기가 강도에 미치는 영향을 고려하기 위하여 강화 입자 주위에 변형률 구배 소성과 테일러 전위 모델을 적용하였다. 변형률 구배는, 구형 단위 셀이 냉각하는 동안 입자와 기지재의 열팽창계수 차이에 의한 전위 펀칭이 일어날 때 형성되는등가소성변형률로부터 구하였다. 펀칭된 영역에 걸쳐 평균적으로 변형률 구배를 고려함으로써 항복 응력이 증가하는 것을 관찰하였다. 유한요소 해석을 활용하여 다양한 입자 크기와 체적비에 대하여 SiC 강화 알루미늄 356-T6 복합재의 축대칭 단위 셀의 인장시 강도의 변화를 예측하였다. 예측된 강도는 실험 데이터와 잘 일치하며, 입자 크기 의존 효과를 분명히 보인다. This study proposes finite element modeling of dislocation punching at cooling after consolidation in order to calculate the strength of particle-reinforced aluminum composites. The Taylor dislocation model combined with strain gradient plasticity around the reinforced particle is adopted to take into account the size-dependency of different volume fractions of the particle. The strain gradients were obtained from the equivalent plastic strain calculated during the cooling of the spherical unit cell, when the dislocation punching due to CTE (Coefficient of Thermal Expansion) mismatch is activated. The enhanced yield stress was observed by including the strain gradients, in an average sense, over the punched zone. The tensile strength of the SiCp/Al 356-T6 composite was predicted through the finite element analysis of an axisymmetric unit cell for various sizes and volume fractions of the particle. The predicted strengths were found to be in good agreement with the experimental data. Further, the particle-size dependency was clearly established.

군집 알루미늄 입자의 연소 모델링 및 수치해석

한두희,성홍계 한국항공우주학회 2015 한국항공우주학회 학술발표회 논문집 Vol.2015 No.4

본 연구는 고 에너지 물질인 알루미늄 입자 연소에 대한 수치적 모델링 및 검증을 수행하였다. 해석은 Eulerian-Lagrangian 이상 유동 해석 기법을 적용하였다. 연구 목적은 알루미늄 입자를 포함한 대용량 전산해석에 적용 가능한 입자연소를 모델링하고, 계산의 단순화를 위해 실험적으로 계산된 연소시간 상관관계식을 적용하였다. 단일 알루미늄입자 연소 모델은 자유낙하 입자 연소 실험결과와 비교 검증하고, 군집 알루미늄 입자의 연소 및 수치 모델은 알루미늄-공기 분젠버너 실험과 비교 검증하였다. 군집입자의 연소 모델링의 해석 결과는 실험의 화염구조(화염 부양 높이, 화염 높이, 화염 두께 등)와 비교하여 매우 유사한 결과를 제시하였다. Numerical analysis on dust combustion of cloud aluminum particles has been conducted using Eulerian-Lagrangian method. The purpose of this study is proposing the combustion modeling scheme applicable for real scale engine combustor including dust aluminum particles. Several experimental correlations causes the dust combustion model to be computed by current computation resources. Single particle combustion, freely falling in a furnace, has been validated with experimental and analytical data. The dust combustion has been validated with the experimental flame structure of aluminum-air Bunsen burner such as lift height, length, and thickness of flame speed.

나노-마이크로 알루미늄 혼합 입자의 공기와의 연소 모델링

윤시경(Shikyung Yoon),신준수(Junsu Shin),성홍계(Honggye Sung) 한국추진공학회 2011 한국추진공학회지 Vol.15 No.6

One dimensional combustion modeling of aluminum combustion behavior is proposed. Combustion model is assumed that region consists as follows ; preheat, reaction, post reaction region. Flame speed as a function of particle size, equivalence ratio for unitary particles and fraction ratio of micro to nano particle size for binary particles were investigated for lean burn condition at 1 atm. Results were compared with experimental data. For unitary particles, flame speed increase as particle size decreases, but opposite trend with equivalence ratio. For binary particles, flame speed increases proportionally as nano particle fraction increases. For flame structure, separated or overlapping flames are observed, depending on the fraction of nano sized particles.

변형률 구배 소성을 고려한 입자 강화 복합재의 크기 종속 강화 모델링

서영성(Yeong Sung Suh),박문식(Moon-Shik Park),송승(Seung Song) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.11

A finite element modeling of dislocation punching is introduced to calculate strengthening of particle reinforced aluminum composites. Taylor dislocation model combined with strain gradient plasticity around the SiC particle is used to take account of the size dependency for different volume fractions of particle. The strain gradient is taken from the equivalent plastic strain calculated during cooling of the spherical unit cell, when the dislocation punching due to CTE mismatch is activated. Enhanced yield stress is observed by including strain gradients in an average sense over the punched region. The tensile strength of the SiC<SUB>p</SUB>/Al 356-T6 composite is predicted finite element analysis of unit cell for various sizes and volume fractions of the particle. Predicted strengths are in good agreement with the experimental data. Also, particle size dependency is clearly exhibited.