연소모델 변화에 따른 가스터빈 엔진 연소기의 열유동 해석

구자예,노현석 한국 항공대학교 항공산업기술연구소 1999 航空宇宙産業技術硏究所 硏究誌 Vol.9 No.-

본 연구는 실험용 가스터빈 엔진용 연소기에 대하여 다양한 연소 모델을 적용한 수치 해석적인 연구를 실시하여 실험 측정치와 해석 결과를 온도, 화학종 농도, 속도 분포에 대하여 비교 분석하였다. 계산을 위해서 상용 다용도 열유체 해석 코드인 STAR-CD를 이용하였다. 서로 다른 연소 모델의 차이를 비교하기 위하여 3단계 EBU 모델, 3단계 반응을 선택 모델, PPDF 모델을 이용하였다. 이중 3단계 반응 모델과 PPDF모델은 경향적으로 타당한 결과를 보였으며 이들간에 서로 다른 결과도 모여 주었다. Numerical analysis of the model gasturbine combustor is performed with various chemical reaction models and turbulence intensities and compared with experiment measurements of temperature, chemical species concentration and velocity. For calculation, commercial multi purpose CFD code STAR-CD is used. To study differences of solutions using different combustion models, 3-step eddy break up model, 3-step hybrid chemical reaction rate model and PPDF model are used. Among them 3-step model and PPDF model shows reasonably good agreements to experimental measurements. But each model gives slight differences.

비정상 액체제트 분열 메카니즘

구자예,정홍철 한국항공대학교 1994 論文集 Vol.32 No.-

액적의 분열기구를 재조사하고 Rayleigh-Taylor불안정과 Kelvin-Helmholtz불안정 이론을 기초한 분열모델을 비정상 액체제트기둥에 적용하였다. 본 논문에서는 비정상 분열기구에 근거한 새로운 액체제트 분열모델을 개발하는 것이다. 액체 기둥은 연속된 액적구의 사슬로 생각되어지며 이 액체기둥은 제안된 분열기구의 불안정성 조건이 만족되는지를 계속 조사되어진다. 일단 액적구가 주 액체제트기둥에서 분리되면 이 액적들은 단일 액적분열이론을 적용 받는다. Bond수가 임계 Bond수 보다 높으면 단일 액적으로 생각되는 액적들은Rayleigh-Taylor불안정이나 Kelvin-Helmholtz불안정에 의해 계속 분열된다. 제안된 비정상 액체제트 분열모델을 사용하여 계산한 분무선단도달거리, 액적크기, 및 속도들의 분무특성은 실험에서 구한 이들 분무특성들과 비교하였다. The mechanisms of breakup of liquid drop are reviewed. A breakup model based on Rayleigh-Taylor instability and Kelvin-Helmholtz instability is applied to the transient liquid jet column. The focus of this paper is the development of a new liquid jet breakup model based on the transient breakup mechanism. Liquid column is considered as a chain of balls. Liquid jet column is continuously surveyed to apply breakup mechanisms. Once liquid droplets are separated from the main liquid jet column, these droplets are subjected to the single breakup mechanism. When Bond number is greater than critical Bond number, single droplets continue to break up by Rayleigh-Taylor instability or Kelvin-Helmholtz instability. Proposed models for transient liquid jet breakup were tested by comparing the calculated spray tip penetration and droplet sizes and velocities with the measurements.

시간적으로 변동하는 연료 분무의 노즐부근에서의 미립화 특성

구자예 한국항공대학교 1993 論文集 Vol.31 No.-

시간적으로 변동하는 연료 분무를 주위 가스와 액체 연료의 밀도비를 변화시켜 가면서 분무 액적 크기와 속도를 측정하였으며 또한 동일 분무를 확대 사진으로 찍어서 노즐 근방에서의 분무 특성을 조사하였다. 노즐 근방이지만 분무 가장자리에서 액적의 크기와 속도를 동시 측정한 결과 액적 속도는 니들이 열릴 때와 닫힐 깨 속도의 피크를 나타내었고 액적 크기는 가장자리로 갈수록 작아지는 경향이 있었다. 노즐 근방에서 확대 사진을 찍은 결과 분무가 퍼지는 정도(분무각)는 분사 시작 직후 넓게 퍼졌으며 곧바로(0.5msec 이후) 좁아지기 시작하여 일정한 값을 나타내었다. 주위 조건에 관계없이 분사 초기에 분무가 넓게 퍼지는 현상이 나타났으며 특히 진공 상태에 가까운 조건에서도 분사직후 분무각은 크게 나타났기 때문에 이는 공기역학적인 상호작용(aerodynamic interactions)에 기인하는 것이 아니라 노즐 내부에 기인하는 요소라 생각된다. 그러나 일단 분무가 완전히 성립된 후에는 노즐 근방의 미립화에 있어서도 공기역학적인 상호작용이 필요하다. The behavior of a transient fuel spray in a near-nozzle region during liquid atomization process has been investigated with the simultaneous measurement of droplet sizes and velocities and microphotographs of the near-nozzle region for a range of gas-to-liquid density ratios. At the edge of the spray, droplet velocities have shown wave-like behavior. The average droplet velocity peaked during needle opening and closing. Droplet sizes tended to be small on the edge of spray. The near-nozzle spray angle taken from the magnification photographs was the greatest on the initial stage and decreased to a relatively constant value after 0.5 msec. Wider dispersion of the fuel spray at initial stage than any other time durion the injection process occured regardless of the ambient gas conditions, even in the near-vaccum condition where aerodynamic interactions between liquid fuel and ambient gas were eliminated. The wider near-nozzle spray angle in the early stage is due to the factors coming from flow characteristics inside nozzle rather than aerodynamic interactions. However, once the spray was established, aerodynamic influences are necessary for near-nozzle atomization in the middle and end of the spray.

고압 수소 기체 환경에서 액체 산소 액적의 초임계 상태의 기화 특성 수치적 연구

고정빈,구자예 한국항공대학교 항공우주산업기술연구소 2003 航空宇宙産業技術硏究所 硏究誌 Vol.13 No.-

Droplet vaporization at high ambient pressures is studied numerically by formulating one dimensional vaporization model in liquid oxygen and hydrogen. The ambient pressure is supercritical conditions. The modified Soave-Redlich-Kwong state equation is used to consider of the real gas effects in the high pressure condition. Non-ideal thermodynamic and transport property at near critical and supercritical conditions are considered. Several parametric studies are performed by changing ambient pressure and temperature. Droplet lifetime is proportional to ambient pressure and temperature. Temporal spatial distribution of properties are also investigated.

복합재료 로케트 노즐의 구조해석

정훈,구자예,이수용 한국 항공대학교 항공산업기술연구소 1995 航空宇宙産業技術硏究所 硏究誌 Vol.5 No.-

복합재료 로케트 노즐에 대한 유동해석, 열전달해석, 응력 및 파손해석을 수행하여 노즐 구조물의 특성을 파악하였다. 유동해석은 FLUENT 프로그램을 이용하여 수행되었고, 축대칭 유한요소 프로그램을 개발하여 열전달해석 그리고 응력 및 파손해석이 수행되었다. 본 연구에서는 노즐의 각 부위에 대해 재료 선택 변화에 따른 특성을 파악하고 또한 복합재료의 적층각도 혹은 회전각도 변화에 대한 해석 및 온도에 의한 강도변화를 고려하여 해석을 수행하였다. Composite rocket nozzles were analyzed for the characteristics of flow, heat transfer, stress, and failure. The flow analysis was performed using FLUENT program and an axisymmetric finite element program was developed for the analysis of heat transfer and stresses. In this paper, the characteristics of the rocket nozzle were evaluated by changing composite materials for the parts of the nozzle. The analysis was also performed for the variation of strength due to temperature as well as for the variation of fiber orientation and rotation.

An Overview of Liquid Spray Modeling Formed by High-Shear Nozzle/Swirler Assembly

Koo, Ja-Ye The Korean Society of Mechanical Engineers 2003 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.17 No.5

A multi-dimensioanl model is being increasingly used to predict the thermo-flow field in the gas turbine combustor. This article addresses an integrated survey of modeling of the liquid spray formation and fuel distribution in gas turbine with high-shear nozzle/swirler assembly. The processes of concern include breakup of a liquid jet injected through a hole type orifice into air stream, spray-wall interaction and spray-film interaction, breakup of liquid sheet into ligaments and droplet,5, and secondary droplet breakup. Atomization of liquid through hole nozzle is described using a liquid blobs model and hybrid model of Kelvin-Helmholtz wave and Rayleigh-Taylor wave. The high-speed viscous liquid sheet atomization on the pre-filmer is modeled by a linear stability analysis. Spray-wall interaction model and liquid film model over the wall surface are also considered.

Assessment of a Phase Doppler Anemometry Technique in Dense Droplet Laden Jet

Ja-Ye Koo,Jong-Hyun Kim 대한기계학회 2003 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.17 No.7

This study represents an assessment of the phase- Doppler technique to the measurements of<br/> dense droplet laden jet. High-pressure injection fuel sprays have been investigated to evaluate the use of the Phase-Doppler anemometry (PDA) technique. The critical issue is the stability of the phase-Doppler anemometry technique for dense droplet laden jet such as Diesel fuel spray in order to insure the results from the drop size and velocity measurements are repeatable, consistent, and physically realistic because the validation rate of experimental data is very low due to the thick optical density. The effect of shift frequency is minor, however, the photomultiplier tube(PMT) voltage setting is very sensitive to the data acquisition and noise in dense droplet laden jet. The optimum PMT voltage and shift frequency should be chosen so that the data such as volume flux and drop diameter do not change rapidly.

The Effects of Injector Nozzle Geometry and Operating Pressure Conditions on the Transient Fuel Spray Behavior

Koo, Ja-Ye The Korean Society of Mechanical Engineers 2003 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.17 No.4

Effects of Injector nozzle geometry and operating pressure conditions such as opening pressure, ambient pressure. and injection pressure on the transient fuel spray behavior have been examined by experiments. In order to clarify the effect of internal flow inside nozzle on the external spray, flow details Inside model nozzle and real nozzle were alto investigated both experimentally and numerically. for the effect of injection pressures, droplet sizes and velocities were obtained at maximum line pressure of 21 MPa and 105 MPa. Droplet sizes produced from the round inlet nozzle were larger than those from the sharp inlet nozzle and the spray angle of the round inlet nozzle was narrower than that from the sharp inlet nozzle. With the increase of opening pressure, spray tip penetration and spray angle were increased at both lower ambient pressure and higher ambient pressure. The velocity and size profiles maintained similarity despite of the substantial change in injection pressure, however, the increased injection pressure produced a higher percentage of droplet that are likely to breakup.

The Effects of Injector Nozzle Geometry and Operating Pressure Conditions on the Transient Fuel Spray Behavior

Ja Ye Koo 대한기계학회 2003 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.17 No.4

Effects of injector nozzle geometry and operating pressure conditions such as opening pressure, ambient pressure, and injection pressure on the transient fuel spray behavior have been examined by experiments. In order to clarify the effect of internal flow inside nozzle on the external spray, flow details inside model nozzle and real nozzle were also investigated both experimentally and numerically. For the effect of injection pressures, droplet sizes and velocities were obtained at maximum line pressure of 21 MPa and 105 MPa. Droplet sizes produced from the round inlet nozzle were larger than those from the sharp inlet nozzle and the spray angle of the round inlet nozzle was narrower than that from the sharp inlet nozzle. With the increase of opening pressure, spray tip penetration and spray angle were increased at both lower ambient pressure and higher ambient pressure. The velocity and size profiles maintained similarity despite of the substantial change in injection pressure, however, the increased injection pressure produced a higher percentage of droplet that are likely to breakup.

Assessment of a Phase Doppler Anemometry Technique in Dense Droplet Laden Jet

Koo, Ja-Ye,Kim, Jong-Hyun The Korean Society of Mechanical Engineers 2003 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.17 No.7

This study represents an assessment of the phase-Doppler technique to the measurements of dense droplet laden jet. High-pressure injection fuel sprays have been investigated to evaluate the use of the Phase-Doppler anemometry (PDA) technique. The critical issue is the stability of the phase-Doppler anemometry technique for dense droplet laden jet such as Diesel fuel spray in order to insure the results from the drop size and velocity measurements are repeatable, consistent, and physically realistic because the validation rate of experimental data is very low due to the thick optical density. The effect of shift frequency is minor, however, the photomultiplier tube (PMT) voltage setting is very sensitive to the data acquisition and noise in dense droplet laden jet. The optimum PMT voltage and shift frequency should be chosen so that the data such as volume flux and drop diameter do not change rapidly.