• 제목/요약/키워드: flame-flame interaction

검색결과 208건 처리시간 0.024초

난류 Pilot 비예혼합 화염장의 상세구조 해석 (Numerical Investigations of Turbulent Piloted Non-Premixed Flames)

  • 이정원;전상태;김용모
    • 한국연소학회:학술대회논문집
    • /
    • 한국연소학회 2014년도 제49회 KOSCO SYMPOSIUM 초록집
    • /
    • pp.185-186
    • /
    • 2014
  • The multi-environment probability density function model has been applied to simulate the turbulent stratified premixed flames. The direct quadrature method of moments (DQMOM) has been adopted to solve the transport PDF equation due to its computational efficiency and robustness. The IEM mixing model is employed to represent the mixing process and the chemical mechanism is based on Gri 3.0 mechanism. Numerical results obtained in this study are precisely compared with experimental data in terms of unconditional and conditional means for scalar fields and velocity fields.

  • PDF

하이브리드 로켓 후연소실 전단유동과 연소반응의 상호 간섭 (Flame Interaction with Shear Layer Flow in the Post Chamber of Hybrid Rocket)

  • 문영주;이창진
    • 한국항공우주학회지
    • /
    • 제44권7호
    • /
    • pp.585-592
    • /
    • 2016
  • 하이브리드 로켓의 연소실험에서 관찰된 500 Hz 대역의 연소압력과 연소반응 변동이 안정한 연소에서 발생하는 원인과 LFI로 발전하는 과정을 분석하기 위하여 $CH^*$ 화학발광 이미지와 PMT(photomultiplier tube)에 의한 광자방출 측정으로 연소반응 변화를 가시화하였다. 안정한 연소에서는 500 Hz 대역의 연소압력과 연소반응 변동의 위상차이가 180 도 정도를 이루며 전단층 유동을 따라서 정상적인 연소가 발생하였다. 그러나 불안정 연소가 발생하면, 500 Hz 주파수의 두 변동의 위상차는 60~70 도로 양의 관계(positive coupling)를 이루며 상하 대칭의 와류 발생과 국부적 소염이 나타나는 주기적 변화를 반복한다. 또한 천이구간에서는 매우 불규칙적인 와류와 상하 대칭의 전단층 유동 형상이 번갈아 관찰되고 있다. 이것은 연소의 영향으로 와류가 발생하는 것으로 보염기 후류에서 발생한 BVK 유동불안정과 유사한 특성을 보여준다, 따라서 하이브리드 로켓 연소의 저주파수 연소불안정은 500 Hz 대역의 연소반응 변동에 의한 와류의 발생과 이로 인한 국부적인 소염이 점진적으로 발전하여 완전한 주기적 소염으로 이어졌고, 20 Hz의 연소불안정으로 발전하는 것으로 판단하였다.

난류연소 모델링을 이용한 수소-공기 비예혼합 화염의 NOx 생성 분석 (Analysis of NO Formation in Nonpremixed Hydrogen-Air Flames Considering Turbulence-Chemistry Interaction)

  • 박양호;문희장;김성룡;윤영빈;정인석
    • 한국연소학회:학술대회논문집
    • /
    • 한국연소학회 1999년도 제19회 KOSCO SYMPOSIUM 논문집
    • /
    • pp.71-79
    • /
    • 1999
  • Numerical analysis on the characteristics of nitrogen oxides (NOx) formation in turbulent nonpremixed hydrogen-air flames was carried out. Lagrange IEM model and Assumed PDF model were applied to consider turbulence-chemistry interaction known to affect the production of NOx. Partial equilibrium assumption was used to predict nonequilibrium effect to which one-half power dependence between EINOx normalized by flame residence time and global strain rate is attributed. As a result. such one-half power dependence could be reproduced only by reaction model including $HO_{2}$and $H_{2}O_{2}$, which means its dependence on Damkohler number; nonequilibrium effect. This dependence was shown better in the region of higher global strain. Besides, the improvement of turbulence model is required to predict mean flow properties quantitatively in the radial direction.

  • PDF

시간지연 모델을 이용한 충돌형 분사기의 연소응답 인자 도출 및 정량화에 관한 수치해석적 연구 (A Numerical Study on Quantification of Combustion-Response Parameters of Impinging-Jet Injectors using Time-Lag Model)

  • 손진우;김철진;손채훈
    • 한국연소학회:학술대회논문집
    • /
    • 한국연소학회 2012년도 제45회 KOSCO SYMPOSIUM 초록집
    • /
    • pp.5-7
    • /
    • 2012
  • This study presents relations between the time lag and interaction index of the impinging-jet injectors using time lag model in a model chamber. To analyze the response of the flame, 5% amplitude of oxidizer velocity is artificially perturbed at a resonance frequency. At the mixing point of fuel and oxidizer, which determines the characteristic length, the relationship between velocity perturbation and heat release rate is quantified by combustion parameters of interaction index and time lag. As the improved method to apply the time-lag, the method using the average velocity obtained from numerical results is suggested.

  • PDF

DME 및 n-Heptane 연료의 디젤엔진 조건에서 분무연소특성 해석 (Numerical Study on the Characteristics of Spray Combustion Processes in the DME and n-heptane Fueled Diesel-like Engine Conditions)

  • 유용욱;석준호;이상길;김용모
    • 한국분무공학회지
    • /
    • 제13권2호
    • /
    • pp.91-98
    • /
    • 2008
  • In the present study, in order to understand the overall spray combustion characteristics of DME fuel as well as to identify the distinctive differences of DME combustion processes against the conventional hydrocarbon liquid fuels, the sequence of the comparative analysis have been systematically made for DME and n-heptane liquid fuels. To realistically represent the physical processes involved in the spray combustion, this studyemploys the hybrid breakup model, the stochastic droplet tracking model, collision model, high-pressure evaporation model, and transient flamelet model with detailed chemistry. Based on numerical results, the detailed discussions are made in terms of the autoignition, spray combustion processes, flame structure, and turbulence-chemistry interaction in the n-heptane and DME fueled spray combustion processes.

  • PDF

수송 확률밀도함수모델을 이용한 비예혼합 난류화염장 해석 (Transported PDF Model for Turbulent Nonpremixed Flames)

  • 이정원;석준호;김용모
    • 한국연소학회지
    • /
    • 제14권2호
    • /
    • pp.32-41
    • /
    • 2009
  • The transported probability density function model combined with the consistent finite volume (FV) method has been applied to simulate the turbulent bluff-body reacting flows. To realistically account for the non-isotropic turbulence effects on the turbulent bluff-body reacting flows, the present PDF transport approach is based on the joint velocity- turbulent frequency-composition PDF formulation. The evolution of the fluctuating velocity of a particle is modeled by a simplified Langevin equation and the particle turbulence frequency is represented by the modified Jayesh - Pope model. Effects of molecular diffusion are represented by the interaction by exchange with the mean (IEM) mixing model. To validate this hybrid FV/PDF transport model, the numerical results are compared with experimental data for the turbulent bluff-body reacting flows.

  • PDF

하이브리드/이중 선회제트 연소기에서 부분예혼합-예혼합 선회화염의 상호작용 (Interaction Between Partially Premixed and Premixed Swirl Flames in a Hybrid/Dual Swirl Jet Combustor)

  • 조준익;황철홍;이기만
    • 한국연소학회:학술대회논문집
    • /
    • 한국연소학회 2012년도 제44회 KOSCO SYMPOSIUM 초록집
    • /
    • pp.7-8
    • /
    • 2012
  • The effects of interaction between partially premixed and premixed swirl flames on CO and NOx emissions were experimentally investigated using a hybrid/dual swirl jet combustor for a micro-gas turbine. Under the condition of constant angle ($45^{\circ}$) for outer swirl vane, the angle and direction of inner swirl vane installed for a partially premixed flame were varied as main parameters with a constant fuel flow rate for each nozzle. It was found that for all conditions, CO and NOx emissions were measured below 4 ppm and 15 ppm at 15% $O_2$, respectively, in a wide range of equivalence ratio (0.6~0.9). For co-swirl flows, CO emission increased dramatically as the angle of inner swirl vane increased from $15^{\circ}$ to $45^{\circ}$ near lean-flammability limit (i.e. equivalence ratio of 0.5). On the other hand, the case of swirl $angle=45^{\circ}$ provided the lowest NOx emission at higher equivalence ratios than 0.6. For counter-swirl flows, the case of swirl $angle=45^{\circ}$ extended the lean-flammability limit but higher NOx emissions were found compared to those of co-swirl flows. These results could be inferred by interaction between (inner) partially premixed and (outer) premixed swirl flames. However, these estimations were not clear yet because there was insufficient data on turbulent flow structure and fuel-air mixing in the present experimental approach.

  • PDF

충돌형 분사기의 연소응답 인자 정량화에 관한 수치해석적 연구 (A Numerical Study on Combustion-Response Parameters of Impinging-Jet Injectors for Stability Rating)

  • 손진우;김철진;손채훈
    • 한국추진공학회지
    • /
    • 제17권2호
    • /
    • pp.1-8
    • /
    • 2013
  • 모형 연소실에서 충돌형 분사기의 연소 안정성 평가를 위해 시간지연(time lag)과 간섭인자(interaction index)의 관계를 연구하였다. 산화제 분사 속도의 5%에 해당하는 섭동을 공진주파수로 인위적으로 가진하여 이에 대한 화염의 응답특성을 분석하였다. 연료와 산화제의 혼합지점인 충돌점들, 즉, 특성길이 위치에서 속도섭동과 열방출율 섭동간의 관계를 시간지연 모델을 이용하여 나타내었다. 시간지연을 정량화하는 개선된 방법으로서, 수치해석을 통해 얻은 결과로부터 분사기 출구면으로부터 충돌점까지 평균속도를 이용하는 방법을 제안하였다. 축방향의 평균속도가 증가할수록 시간지연이 짧아지는 경향성을 확인할 수 있었다.

대형기관 모사 정적연소실에서 매립지 가스의 연소특성에 대한 연구 (II) - 연소 분석 - (Combustion Characteristics of Landfill Gas in Constant Volume Combustion Chamber for Large Displacement Volume Engine (II) - Combustion Analysis -)

  • 권순태;박찬준;엄인용
    • 대한기계학회논문집B
    • /
    • 제37권8호
    • /
    • pp.743-752
    • /
    • 2013
  • 본 논문은 대형 상용기관을 모사한 정적연소실에서 매립지 가스의 연소 특성에 대한 복수의 논문 중 두 번째로, 연소압력 측정을 기반으로 연소과정을 해석하였다. 해석 결과 연소에 유리한 조건일수록 두 개의 압력 정점이 존재하며, 이는 연소에 의한 열발생과 열전달에 의한 냉각효과의 상호 작용이며 두 정점의 크기는 미연가스 분율에 따라 달라진다. 또한 연소과정 중 열발생에는 4개의 주요 변곡점이 발생하고, 이는 점화위치로부터 화염전파에 따른 전열 면적 변화과정이 주원인이며 연소에 불리한 조건일수록 변곡점은 증가하고 열발생은 복잡한 형태를 지니는데, 이는 연소기간 연장이 주원인이다. 결론적으로 점화위치와 관련된 화염전파 과정 및 전열 면적의 변화과정 그리고 대형 연소실에 의한 연소기간 연장의 효과가 상호 복잡하게 작용하면서 매우 특이한 형태의 열발생 곡선이 생성된다.

Predicting the Frequency of Combustion Instability Using the Measured Reflection Coefficient through Acoustic Excitation

  • Bae, Jinhyun;Yoon, Jisu;Joo, Seongpil;Kim, Jeoungjin;Jeong, Chanyeong;Sohn, Chae Hoon;Borovik, Igor N.;Yoon, Youngbin
    • International Journal of Aeronautical and Space Sciences
    • /
    • 제18권4호
    • /
    • pp.797-806
    • /
    • 2017
  • In this study, the reflection coefficient (RC) and the flame transfer function (FTF) were measured by applying acoustic excitation to a duct-type model combustor and were used to predict the frequency of the combustion instability (CI). The RC is a value that varies with the excitation frequency and the geometry of the combustor as well as other factors. Therefore, in this study, an experimentally measured RC was used to improve the accuracy of prediction in the cases of 25% and 75% hydrogen in a mixture of hydrogen and methane as a fuel. When the measured RCs were used, an unstable condition was correctly predicted, which had not been predicted when the RCs had been assumed to be a certain value. The reason why the CI occurred at a specific frequency was also examined by comparing the peak of the FTF with the resonance frequency, which was calculated using Helmholtz's resonator analysis and a resonance frequency equation. As the CI occurred owing to the interaction between the perturbation in the rate of heat release and that in the pressure, the CI was frequent when the peak of the FTF was close to the resonance frequency such that constructive interference could occur.