A Study on Factors Affecting Combustion Characteristics of GCSC Injector

Yuangang Wang(왕위엔강),Jinwoo Son(손진우),Chae Hoon Sohn(손채훈) 한국연소학회 2019 한국연소학회지 Vol.24 No.1

Factors affecting the combustion characteristics of gas-centered swirl coaxial (GCSC) injectors are investigated numerically and experimentally. The factors are fuel volume flow rate (Qf), momentum flux ratio (MFR) and oxidizer/fuel (O/F) ratio. Firstly, the flame pattern becomes asymmetric as the fuel volume flow rate increases with a fixed momentum flux ratio. Then, the suitable fuel volume flow rate is selected according to the results. Next, the momentum flux ratio is increased by increasing the oxidizer volume flow rate (Qo) with a fixed fuel volume flow rate. Results show that the spreading angle decreases as momentum flux ratio increases, which agrees with our previous results. Finally, in order to check effects of oxidizer/fuel ratio, the Qf, Qo, and MFR are kept the same but the O₂ mole fraction of oxidizer is changed. From numerical and experimental results, it is found that flame pattern depends on oxidizer/fuel ratio and spreading angle increases as the O₂ mole fraction decreases.

횡단유동내 인젝터 홀의 위치에 따른 제트의 분무 특성

최명환(Myeung Hwan. Choi),신동수(DongSoo. Shin),Kanmaniraja. Radhakrishna,손민(Min. Son),구자예(jaye. Koo) 한국추진공학회 2017 한국추진공학회 학술대회논문집 Vol.2017 No.5

공기와 물을 사용하여 인젝터의 위치와 운동량 플럭스 비가 수직유동이 횡단유동장내의 수직분사제트에 미치는 영향을 정성적으로 연구하고 도시하였다. 운동량 플럭스 비를 고정하고 인젝터 홀의 위치를 변화시키고 역으로 인젝터 홀의 위치를 고정하고 운동량 플럭스 비를 변화시켰다. 이미지 가시화는 고속카메라를 이용하여 Shadowgraph 기법을 사용하였다. 가시화된 이미지는 밀도구배강도 이미지를 통하여 분무의 차이를 비교하였다. 장치의 x/d가 증가할수록 제트의 분열 높이가 낮아지며 분무 각도 또한 감소하는 것을 관측하였다. x/d가 0일 때는 어떠한 운동량 플럭스 비에서도 분무가 바닥과 천장에 닿게 되는 결과를 보였다. Effects of injector position and momentum flux ratio on a vertical jet in a cross flow field were studied qualitatively and shown by using air and water. The experiment was carried out by fixing the momentum flux ratio and varying the position of the injector hole. Conversely, the injector hole position was fixed and the momentum flux ratio was varied. Image visualization was performed by a Shadowgraph technique using a high speed camera. The visualized images were compared for finding differences in spraying through Density Gradient Magnitude Image. It is observed that as the x/d of the apparatus increased the jet break up height decreases and the spray angle also decreases. When x/d is 0, the spray reaches the floor and ceiling at any momentum flux ratio.

기체 중심 스월 동축형 분사기가 장착된 모형연소기의 운동량비 변화에 따른 연소불안정성 분석

손채훈(Chae Hoon Sohn),김명섭(Myeong Sub Kim),Yuangang Wang,윤영빈(Youngbin Yoon) 한국추진공학회 2020 한국추진공학회지 Vol.24 No.4

A numerical study on combustion instabilities in a model combustor was conducted with various momentum flux ratios. Five ratios are calculated based on an actual operating condition of rocket engine. As momentum flux ratio increases, the spreading angle on the injector outlet decreases. And, as increase of axial momentum flux, pressure fluctuation decreases inside the combustor. By using dynamic mode decomposition method, the acoustic modes inside the combustor are identified. Combustion stabilities are analyzed by comparing the damping coefficient of the 2nd longitudinal mode.

A two-phase damping model on tube bundles subjected to two-phase cross-flow

심우건,N. W. Mureithi 대한기계학회 2014 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.28 No.2

An analytical model is developed to estimate the two-phase damping ratio for upward cross-flow through horizontal tube bundles. Thepresent model is formulated based on Feenstra’s model (2000) for void fraction and various models (homogeneous, Levy, Martinelli-Nelson and Marchaterre) for two-phase friction multiplier. The analytical results of drag coefficient on a cylinder and two-phase Eulernumber are compared with the experimental results by Sim-Mureithi (2013). The correlation factor between frictional pressure drop andthe hydraulic drag coefficient is evaluated by considering the experimental results. The two-phase damping ratios given by the analyticalmodel are compared with existing experimental results. The model based on Marchaterre’s model is suitable for air-water mixture,whereas the Martinelli-Nelson’s model is suitable for steam-water and Freon mixtures. The two-phase damping ratio is independent ofpitch mass flux for air-water mixture, but is more or less influenced by the mass flux for steam-water/Freon (134) mixtures. The twophasedamping ratios given by the present model agree well with experimental results for a wide range of pitch mass ratio, quality, andp/d ratios.

횡단유동내 인젝터 홀의 위치에 따른 제트의 분무 특성

최명환(Myeung Hwan Choi),신동수(Dong Soo Shin),Kanmaniraja Radhakrishnan,손민(Min Son),구자예(Jaye Koo) 한국추진공학회 2018 한국추진공학회지 Vol.22 No.5

Effects of injector position and momentum flux ratio on a vertical jet in a cross-flow field are qualitatively studied and displayed using air and water. The position of the injector hole and the momentum flux ratio is changed and image visualization is performed using a shadowgraph technique and a high-speed camera. The visualized images are compared to find differences in spraying using density gradient magnitude image. It is observed that, as the x/d of the apparatus increases, the jet break-up height decreases. When x/d is 0, the spray reaches the bottom and ceiling at any momentum flux ratio.

기체 유동의 음향학적 가진과 운동량 플럭스 비에 따른 기체 중심 스월 동축형 분사기의 반응 특성

박구정,이정호,윤영빈 한국항공우주학회 2015 한국항공우주학회 학술발표회 논문집 Vol.2015 No.11

본 연구에서는 기체 유동에 음향학적 가진에 따른 기체 중심 스월 동축형 분사기의 분무의 반응을 확인하였다. 동축형 분사기에서 주요 변수로 사용되는 기체-액체 운동량 플럭스 비에 따른 반응 특성을 확인하였다. 기체 유동의 섭동과 액체 액막의 섭동의 비를 게인으로 나타냈고 기체 유동의 섭동은 Hot-wire anemometer를 이용하여 액체 액막의 섭동은 액막 측정 장치를 통하여 측정하였다. 기체 유동에 가진을 주기 위하여 스피커를 이용하였다. 입력 주파수에 따라 반응 특성의 크기는 다른 값들을 가졌으며 특정 주파수에 높은 크기를 가졌다. 또한 기체-액체 운동량 플럭스 비가 증가함에 따라 반응특성의 크기는 전체적으로 증가하였다. 특정 주파수에서 반응 특성이 크게 나타는 이유는 기체 공급 라인 길이와 액체와 기체의 점성 전단 불안정성과의 공진에 의한 것으로 판단된다. In this study, the response characteristic of gas centered swirl coaxial injector with the excitation on gas flow was confirmed. The response characteristic on gas-centered swirl coaxial injectors were found by using the gas-liquid momentum flux ratio that uses the main parameter of coaxial injectors. The gain was represented as ratio of perturbation of gas flow and liquid film. The perturbation of gas flow and liquid film were measured by the hot-wire anemometer and film thickness equipment respectively. The acoustic speaker was used for excitation. The amplitude of gain changed according to input frequency and it had high value at certain frequency. Also, the amplitude of gain increased generally with the gas-liquid momentum flux ratio. It was confirmed that the high value of gain was due to the length of gas supply line and the resonance of viscous shear instability between gas and liquid.

초임계 환경으로 분사되는 극저온 제트의 분열

이건웅 ( Keon Woong Lee ),김도헌 ( Do Hun Kim ),구자예 ( Ja Ye Koo ) 한국분무공학회 2013 한국액체미립화학회지 Vol.18 No.3

Sub/supercritical spray experiments were conducted, and cryogenic nitrogen and gaseous argon were selected for simulants. Liquid nitrogen and gaseous argon were injected in subcritical case, and supercritical nitrogen and near-critical gaseous argon were injected in near-critical/supercritical cases. shadowgraph method was used to visualize spray, and analyzed about the breakup length. The breakup length was measured from numbers of Instantaneous shadowgraph Images from each case, and they were compared with momentum flux ratios and density ratios. It was observed that the relation between breakup length and momentum flux ratio was fitted into former experiment results. and the reasonable constant was suggested about the relation between breakup length and density ratio

경사 분사에 의한 초음속 유동 연료-공기 혼합에 관한 실험적 연구

이동주(Dong-Ju Lee),정은주(Eunju Jeong),김채형(Chae-Hyoung Kim),정인석(In-Seuck Jeung) 한국추진공학회 2008 한국추진공학회 학술대회논문집 Vol.2008 No.5

스크램제트 엔진의 연소기 내부 유동은 초음속이므로 유동의 잔류시간과 혼합율의 증대가 효과적인 연소를 가능하게 하는 주요 요인으로 작용한다. 본 연구에서는 연료-공기 혼합기로써 개방형 공동 모델을 사용하였고, 공동 앞에서의 경사 연료 분사 시 분사구 주위와 공동 주위의 유동특성을 살펴보기 위하여 레이저 슐리렌 기법과 압력측정을 실시하였다. 레이저 슐리렌은 10 ns의 광원 지속시간으로 공동 부근의 비정상 유동 현상을 효과적으로 관찰 할 수 있었다. 또한, 압력측정은 연료 분사 J(운동량비)를 변화시켜 가며 측정하였으며, 운동량비에 따른 연소기 내부 주요 연소발생 지점의 변화를 살펴 볼 수 있었다. The flow of combustor in scramjet engine is supersonic speed. So residence time and mixing ratio are very important factors for efficient combustion. This study used open cavity on fuel/air mixing model and laser schlieren was carried out to investigate flow characteristics around a jet orifice and a cavity. A source of illumination has 10 ns endurance time so it can observe unsteady flow characteristics efficiently. Pressure was measured by varying momentum flux ratio. And the change of critical ignition point was observed to change of momentum flux ratio.

분사조건에 따른 기체/액체 동축형 인젝터의 분무특성에 관한 연구

정원호(W. H. Jeong),김동준(D. Kim),임지혁(J. H. Im),윤영빈(Y. Yoon) 한국항공우주학회 2005 韓國航空宇宙學會誌 Vol.33 No.1

기체와 액체 추진제를 사용하는 동축형 분사기의 분무특성을 조사하기 위하여 shadow graph와 mechanical patternator, PDPA를 이용한 실험을 수행하였다. 차원해석 방법을 도입하여 운동량 플럭스 비(M)와 레이놀즈 수(Re)를 기체/액체 동축형 분무의 주요 변수로 설정하였고, 실험을 통하여 전단 및 스월 동축형 분무의 특성을 거시적 및 미시적 관점에 서 비교ㆍ분석하였는데, 기체 추진제의 영향력이 커지는 분사조건에서 전단 및 스월 동축형 분무의 거시적 특성이 유사해짐을 확인할 수 있었다. 또한, 본 연구에서는 미시적 분무 특성에 대한 분석 결과로서 분무액적 크기와 분사조건 사이의 관계식도 제시하였다. Characteristics of sprays injected by gas/liquid coaxial atomizers operated at atmospheric pressure are studied using shadowgraph, mechanical patternator and PDPA. The gas-to- liquid momentum flux ratio(M) and the liquid Reynolds number(Re) are selected as key parameters in characteristics of gas/liquid coaxial sprays from the dimensional analysis. The properties of shear coaxial sprays are compared with those of swirl coaxial sprays through the macroscopic and microscopic analysis. Macroscopic similarities between shear and swirl coaxial sprays are revealed under flow conditions of high momentum flux ratio. Also, empirical correlations between the mean drop diameters(D₃₂) and operating conditions of coaxial sprays are proposed in this paper.

미립화 및 분무장치 1 : 이상유체 분사기의 분사조건에 따른 분무 형상 연구

이영선 ( Young Sun Yi ),홍문근 ( Moon Geun Hong ),이수용 ( Soo Yong Lee ) 한국액체미립화학회 2012 한국액체미립화학회 학술강연회 논문집 Vol.2012 No.-

Gas-centered swirl coaxial injectors are widely used for staged combustion cycle engines. In recent years, the gas-centered swirl coaxial injector has attracted much attention for the high-power application in liquid rocket engines because of its efficient atomization characteristics. The understanding of the spray characteristics of the gas-centered swirl coaxial injector is indispensible for the design of more reliable and efficient injectors dedicated to liquid rocket engines. In particular, experiments were carried out to investigate the effect of momentum flux ratio on the spray pattern of the gas-centered swirl injector. The curvature radius of the spray was predicted using the spray angle measured by image process techniques. The experimental results showed that the curvature radius increases with the increment of the momentum flux ratio.