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손민,김도헌,구자예,장홍빈,강문중,Son, Min,Kim, Dohun,Koo, Jaye,Chang, Hongbeen,Kang, Moonjung 항공우주시스템공학회 2014 항공우주시스템공학회지 Vol.8 No.3
An inner flow of a porous cylinder with partial slots was visualized to study fluidic phenomena in a solid rocket motor. A high-pressure chamber and an air supply system for high flow rate were used. In order to visualize the inner flow, the smoke generator with a cam-driven pump and heaters and high speed camera were adopted. The results of the cylinder type and the partial slot type were compared. As a result, the injected smoke flow in the partial slot type had circumferential fluctuations unlike the cylinder type. It was found that the circumferential flow induced from the partial slots could be the cause of combustion instability and roll torque.
횡단 공기유동장으로 분사되는 저온 에탄올 제트의 침투거리
이종권 ( Jongkwon Lee ),구자예 ( Jaye Koo ) 한국분무공학회지 2020 한국액체미립화학회지 Vol.25 No.2
The jet in crossflow is a spray method used in the various air-breathing engine. In order to understand the spray characteristics in various environments, many prior studies have been conducted. However, there is a lack of understanding of the low-temperature liquid spray characteristics below 273 K. With this in mind, we tried to enhance the knowledge of the lowtemperature liquid spray characteristics by identifying the penetration height of low-temperature ethanol. The experiment was conducted under phase pressure, and 273 K of air and 293, 263, and 233 K of ethanol was used. Shadowgraphy was employed to measure the liquid penetration, and Otsu’s method was used to analyze the penetration height. The heights tend to decrease as the temperature of the liquid jet decreases. A correlation for the penetration height in the experimental conditions was derived and presented.
이건웅,송우석,황주현,황용석,구자예,Lee, Keonwoong,Song, Wooseok,Hwang, Joohyun,Hwang, Yongseok,Koo, Jaye 한국분무공학회 2019 한국액체미립화학회지 Vol.24 No.2
Shear coaxial injectors were commonly used in rocket engine combustor. They showed good combustion performance. However it is not easy to control the thrust. Pintle injectors were not as popular as the coaxial injectors so far, they have a great advantage over the coaxial injectors. That is, it is relatively easy to control the thrust. Spray characteristics of gel type propellant from movable sleeve pintle injector were investigated. Water with 0.05% of Carbopol 940 was used as gel simulant instead of kerosene gel combined with Thixarol ST for academic purpose. Experiments were performed in various temperature, pressure and pintle opening condition. The results were compared with neat liquid spray. It is also verified that the capabilites of the injector by adjusting the pintle opening.
축소형 연소기에서 임계 조건에 따른 화염구조 가시화 시험
송우석(Wooseok Song),구자예(Jaye Koo) 한국추진공학회 2019 한국추진공학회 학술대회논문집 Vol.2019 No.5
고성능 액체로켓엔진 개발을 위해서는 고온, 고압의 연소가 필수적이다. 본 논문에서는 축소형 연소기에서 임계 조건에 따른 화염구조를 가시화하는 것이 목표이다. 전단 동축 분사기를 이용하여 산화제는 기체산소를 사용하였고 연료는 액체 케로신을 사용하였다. 화염구조를 촬영하기 위해 탄화수소계 연료 연소에서 생성되는 CH* 화학발광 성분을 밴드패스필터 및 고속카메라를 이용하여 가시화하였다. 연소불안정 정도를 계산하여 아임계/초임계 연소조건에서 안정된 화염을 확인하였다. 안정된 연소조건에서 화염두께는 아임계 연소조건보다 초임계 연소조건에서 작게 측정되었다.. The high temperature and pressure in the combustion chamber is essential to develop the liquid rocket engine for a high performance. The objective of this study is to visualize the flame structure under subcritical and supercritical conditions using a subsclae combustor. The gaseous oxygen and liquid kerosene were used for propellants with the shear coaxial injector. In order to detect the flame structure, CH* chemiluminescience images, which is one of representative species during the combustion process, was recorded using band-pass filter and high-speed camera. A stable flame was confirmed by calculating the combustion instability intensity under subcritical and supercritical conditions. The flame thickness in the case of supercritical condition was thiner than in the case of subcritical condition.
SiO<sub>2</sub> 계열 젤화제에 따른 케로신 젤 연료의 유변학적 특성 연구
김재우,전두성,강태곤,장석필,구자예,문희장,Kim, Jaewoo,Jun, Doosung,Kang, Teagon,Jang, Seok Pil,Koo, Jaye,Moon, Heejang 한국추진공학회 2012 한국추진공학회지 Vol.16 No.6
본 연구에서는 $SiO_2$ 계열 젤화제로 알려진 Aerosil(R) R972, Silica 230, Silica 530을 사용하여 케로신 기반 젤 연료를 제작하였다. 케로신 계열 연료로는 Jet A-1을 사용하였으며 젤화(gelification) 여부를 확인하기 위한 전단박화(shear thinning) 현상은 멱법칙(power-law) 모델을 이용하여 검증하였고 제작된 모든 젤 연료는 전단박화 효과와 함께 $SiO_2$ 젤화제의 함유량이 증가할수록 젤의 점도가 높게 형성됨을 확인하였다. 본 연구에서 사용된 젤화제 중 Aerosil(R) R972를 첨가한 젤 연료의 점성계수가 전단률 전 영역에 걸쳐 멱법칙 모델을 따르는 것이 확인되었으며 상대적으로 Silica 230과 Silica 530을 첨가한 젤 연료는 전단률 150 [1/s] 근방 이하에서 멱법칙이 유효하지 않음을 알 수 있었다. 또한, 젤화제 함유량이 증가할수록 vortex 혼합법과 수동 혼합법 간의 유변학적 특성이 크게 차이 나는 것이 관찰되었다. Present work deals three families of $SiO_2$ gelling agents which have been used to produce gel fuel based on Kerosene. Jet A-1 is chosen as fuel where power-law rheological model is used to confirm whether or not the gelification is achieved depending on the %wt of gellant. It was confirmed that the produced jelly-like substance have shear-thinning effect, and that its apparent viscosity increases as $SiO_2$ concentration increases. Compared to other gellants, gel with Aerosil(R) R972 fits most to the power-law model, while gels with Silica 230 and Silica 530 deviate from the power-law model. The rheological characteristics behaved differently depending on the mixing method(vortex mixing and manual mixing) when gellant concentration is increased.