• Title/Summary/Keyword: 화염모델

Search Result 286, Processing Time 0.025 seconds

Effects of Underexpanded Plume in Transonic Region on Longitudinal Stability (천음속 영역에서 과소 팽창 화염이 종안정성에 미치는 영향에 관한 연구)

  • Jung, Suk-Young;Yoon, Sung-Joon
    • Journal of the Korean Society for Aeronautical & Space Sciences
    • /
    • v.32 no.8
    • /
    • pp.118-128
    • /
    • 2004
  • Exhaust plume effects on longitudinal aerodynamics of missile were investigated by wind tunnel tests using a solid plume simulator and CFD analyses with both the solid plume and air jet plumes. Approximate plume boundary prediction technique was used to produce the outer shape of the solid plumer and chamber conditions and nozzle shapes of the air jet plumes were determined through plume modeling technique to compensate the difference in thermodynamic properties between air and real plume. From comparisons among turbulence models in case of external flow interaction with the air jet plume, Spalart-Allmaras model turned out to give accurate result and to be less grid-dependent. Effects induced by the plume were evaluated through the computations with Spalart-Allmaras turbulence model and the air jet plume to account for various ratios of chamber and ambient pressure and Reynolds number under the flight test condition.

Investigation of the Prediction Performance of Turbulence and Combustion Models for the Turbulent Partially-premixed Jet Flame (난류 부분예혼합 제트화염에 대한 난류 및 연소모델의 예측성능 검토)

  • Kim, Yu Jeong;Oh, Chang Bo
    • Fire Science and Engineering
    • /
    • v.28 no.4
    • /
    • pp.35-43
    • /
    • 2014
  • The prediction performance of 9 model sets, which combine 3 turbulent models and 3 combustion models, was investigated numerically for turbulent partially-premixed jet flame. The standard ${\kappa}-{\varepsilon}$ (SKE), Realizable ${\kappa}-{\varepsilon}$ (RKE) and Reynolds stress model (RSM) were used as a turbulence model, and the eddy dissipation concept (EDC), steady laminar flamelet (SLF) and unsteady laminar flamelet model (ULF) were also adopted as a combustion model. The prediction performance of those 9 model sets was evaluated quantitatively and qualitatively for Sandia D flame of which flame structure was measured precisely. The flame length was predicted as, from longest to shortest, RSM > SKE > RKE, and the RKE predicted the flame length of the jet flame much shorter than experiment. The flame temperature was over predicted by the combination of RSM + SLF or RSM + ULF while the flame length obtained by RSM + SLF and RSM + ULF was well agreed with the experiment. The combination of SKE + SLF and SKE + ULF predicts well the flame length as well as the temperature distribution. The SKE turbulence model was most superior to the other turbulent models, and SKE + ULF showed the best prediction performance for the structure of turbulent partially-premixed jet flame.

Soot Formation and Combustion in Turbulent Flames (난류 화염 내에서의 매연 입자의 생성및 재연소)

  • 정종수;신현동;이춘식
    • Transactions of the Korean Society of Mechanical Engineers
    • /
    • v.13 no.5
    • /
    • pp.962-978
    • /
    • 1989
  • A new model of the combustion rates of soot particle in turbulent flames has been suggested. This model applies the combustion rate of soot particles in laminar flames and uses local time-averaged quantities in order to consider the effect of the chemical reaction on the soot combustion in turbulent flames. The proposed rate equation has been tested for two propane-air turbulent round-jet diffusion flames and gives better predictions for the soot concentration field of two flames than the model previously used, especially in low temperature regions. A modified Monte carlo Method for analyzing radiative heat transfer of a flame also has been suggested and tested, which reveals good results.

The Flame Color Analysis of Color Models for Fire Detection (화재검출을 위한 컬러모델의 화염색상 분석)

  • Lee, Hyun-Sul;Kim, Won-Ho
    • Journal of Satellite, Information and Communications
    • /
    • v.8 no.3
    • /
    • pp.52-57
    • /
    • 2013
  • This paper describes the color comparison analysis of flame in each standard color model in order to propose the optimal color model for image processing based flame detection algorithm. Histogram intersection values were used to analyze the separation characteristics between color of flame and color of non-flame in each standard color model which are RGB, YCbCr, CIE Lab, HSV. Histogram intersection value in each color model and components is evaluated for objective comparison. The analyzed result shows that YCbCr color model is the most suitable for flame detection by average HI value of 0.0575. Among the 12 components of standard color models, each Cb, R, Cr component has respectively HI value of 0.0433, 0.0526, 0.0567 and they have shown the best flame separation characteristics.

Improved Thermoacoustic Model Considering Heat Release Distribution (열분포를 고려한 열음향 모델의 개선)

  • Kim, Daesik;Kim, Kyu Tae
    • Transactions of the Korean Society of Mechanical Engineers B
    • /
    • v.38 no.6
    • /
    • pp.443-449
    • /
    • 2014
  • Thermoacoustic (TA) models have been widely used to predict combustion instability characteristics in a gas turbine lean premixed combustor. However, these techniques have shown some limitations in improving the model accuracy related to an over-simplification of the combustion system and flame geometry. Efforts were made in the current study to improve the limitations of the TA models. One strategy was to modify the actual flame location in the model, and another was to consider the heat release distribution through the flames. The modified TA model results show better accuracy in predicting the growth rate of instabilities compared with the previous results.

The Interaction of Gaseous Diffusion Flames (기체확산 화염간의 상호작용)

  • 김호영;전철균
    • Transactions of the Korean Society of Mechanical Engineers
    • /
    • v.15 no.1
    • /
    • pp.355-365
    • /
    • 1991
  • New definition for the interaction of flames is introduced and interacting turbulent diffusion flames issuing from two rectangular nozzles are investigated on the basis of the definition. Theoretical study through numerical model is carried out and experiment for validation is conducted. The characteristics of interaction due to the variation of major parameters such as nozzle spacing, Reynolds number and nozzle aspect ratio are studied. Results show that strong interaction occurs for small nozzle spacing, small Reynolds number and large aspect ratio. In order of their magnitude, the intensity of interactions on the individual transport mechanism is momentum, heat and mass. It is also found that interaction makes flames longer, tilted and finally merged. Increase of velocities and temperature, decrease of oxygen concentration and depression of turbulence are occurred in the region between flames.

A Study of the Effect of Flame Stretch of Flame Speed (화염 스트레치가 화염전파속도에 미치는 영향에 관한 연구)

  • 정석호
    • Transactions of the Korean Society of Mechanical Engineers
    • /
    • v.9 no.2
    • /
    • pp.250-258
    • /
    • 1985
  • 비균열 접선속도장에 기인한 화염스트레치 인자와 확산선호도가 예혼합화염의 전파속도에 미치는 영향을 연소가스와 예혼합기의 대향류 유동장을 모델로 하여 접합 전개 방법을 이용하여 일반 인 Lewis수 및 기체팽창을 고려하여 해석하였다. 이 결과 스트레치가 작은 경우에는 확산선호 도에 따라 화염특성이 급격히 변화하는데 이는 곡률을 가진 자유전파화염의 특성과 동일하며 스트레치가 큰 경우에는 확산선호도에 관계없이 화염전파속도는 감소하는 특성을 보여주었다. 또한, 화염스트레치의 실험적 측정 및 이론적 해석에 있어서의 정의 및 화염스트레치의 영향에 관한 현상적 설명에 대하여 재검토하였다.

An Evaluation of Numerical Schemes in a RANS-based Simulation for Gaseous Hydrogen/Liquid Oxygen Flames at Supercritical Pressure (초임계 압력하의 기체수소-액체산소 화염에 대한 난류모델을 이용한 해석에서 수치기법 평가)

  • Kim, Won Hyun;Park, Tae Seon
    • Journal of the Korean Society of Propulsion Engineers
    • /
    • v.17 no.3
    • /
    • pp.21-29
    • /
    • 2013
  • Turbulent flow and thermal fields of gaseous hydrogen/liquid oxygen flames at supercritical pressure are investigated by turbulence models. The modified Soave-Redlich-Kwong (SRK) EOS is implemented into the flamelet model to realize real-fluid combustions. For supercritical fluid flows, the modified pressure-velocity-density coupling are introduced. Based on the algorithm, the relative performance of six convection schemes and the predictions of four turbulence models are compared. The selected turbulence models are needed to be modified to consider various characteristics of real-fluid combustions.

Estimation of Chemical Flame Height based on Fuel Consumption in a Fire Field Model (필드모델에서 연료소모에 기초한 화학적 화염높이 산정)

  • Kim, Sung-Chan
    • Fire Science and Engineering
    • /
    • v.30 no.2
    • /
    • pp.92-97
    • /
    • 2016
  • The present study has been conducted to estimate the chemical flame height based on fuel consumption in fire field model. The calculation algorithms based on cumulative fraction of HRRPUL and fuel concentration along the z axis were applied to the results predicted by Fire Dynamics Simulator (FDS) version 6.3.2 and the mean chemical flame height was obtained by time averaging of instantaneous flame height with the algorithms. The mean flame height calculated by fuel concentration was quite well matched with that of cumulative value of HRRPUL within 10% over-prediction. This study contribute to a more detailed understanding of fire behavior and quantitative evaluation of flame height in the computational fire model.

Phenomenological Derivation of the Effects of Flame Stretch and Preferential Diffusion on Premixed Flame (화염스트레치와 확산선호도가 예혼합화염에 미치는 영향에 관한 현상적 고찰)

  • 정석호
    • Transactions of the Korean Society of Mechanical Engineers
    • /
    • v.9 no.5
    • /
    • pp.655-662
    • /
    • 1985
  • 화염스트레치와 확산선호도가 예혼합화염에 미치는 영향을 몇가지 모델에 대해 현상적으로 고 찰하였다. 즉, 정상상태의 구형화염, 구형으로 전파되는 화염, 균일유동장내의 곡면화염, 일차원 평면화염, 그리고 확대유동장내에서 스트레치된 평면화염등을 고찰하였으며, 이 해석의 결과는 화염면의 면적 변화율로 정의된 화염스트레치의 제인자들 즉, 비균일 접선속도장과 전파화염의 곡률에 의한 영향들이 공통적 특성을 나타냄을 보여주고 있다. 화염스트레치와 확산선호도가 화염전파속도에 미치는 복합효과는 세가지로 나타나는데 이는 화염온도의 변화에 따른 화학반 응강도의 변동, 열 및 물질확산의 강도차이, 그리고 대류 및 확산전달의 방향의 상이함에 기인 한다.