• 제목/요약/키워드: 예혼합 화염

검색결과 324건 처리시간 0.027초

난류예혼합화염이 음파의 산란에 미치는 영향에 관한 연구 (The Effect of Turbulent Premixed Flame on the Wave Scattering)

  • 조주형;백승욱
    • 한국연소학회지
    • /
    • 제12권1호
    • /
    • pp.1-10
    • /
    • 2007
  • Analytical investigation of acoustic wave scattering from turbulent premixed flames was conducted to evaluate the acoustic energy amplification/damping. Such acoustic energy change is attributed to the acoustic velocity jump due to flame's heat release. Small perturbation method up to second order and stochastic analysis were utilized to formulate net acoustic energy and the energy transfer from coherent to incoherent energy. Randomly wrinkled flame surface is responsible for the energy transfer from coherent to incoherent field. Nondimensional parameters that govern net acoustic energy were determined: rms height and correlation length of flame front, incident wave frequency, incidence angle, and temperature ratio. The dependence of net acoustic energy upon these parameters is illustrated by numerical simulations in case of Gaussian statistics of flame front. Total net energy was amplified and the major factors that affect such energy amplification are incidence angle and temperature ratio. Coherent (incoherent) energy is damped (amplified) with rms height and correlation length of flame front.

  • PDF

진동하는 층류예혼합화염의 불안정성에 관한 연구 (A study of Instability on Oscillating Laminar Premixed Flames)

  • 이원남
    • 한국연소학회지
    • /
    • 제13권4호
    • /
    • pp.8-15
    • /
    • 2008
  • When a circular cylinder is placed at the center of a slot burner nozzle, once stable Woflhard-Parker type laminar lean premixed flame is changed to an oscillating flame with self-induced noise. The wrinkled flame surface showed the same pattern and frequency of the Karman vortex street at the downstream of a circular cylinder. The interaction of flame with Karman vortex street is observed to be responsible for flame oscillation. The measured flame oscillation frequency is very similar to the estimated Karman vortex shedding frequency based on the St-Re relationship of the flow past circular cylinder, which could be considered as a strong evidence for the interaction between laminar pre-mixed flame and a Karman vortex street. As Reynolds number increases oscillation frequency decreases and the self-induced noise level increases as well as the flame front is more severly wrinkled. This result suggests that the flame/vortex interaction becomes more active at higher Re.

  • PDF

영역분할조건평균법을 이용한 난류예혼합화염내 난류운동에너지 생성에 관한 연구 (Analysis of Flame Generated Turbulence for a Turbulent Premixed Flame with Zone Conditional Averaging)

  • 임용훈;허강열
    • 한국연소학회지
    • /
    • 제8권4호
    • /
    • pp.15-23
    • /
    • 2003
  • The zone conditional two-fluid equations are derived and validated against DNS database of a premixed turbulent flame. The conditional statistics of major flow variables are investigated to understand the mechanism of flame generated turbulence. The flow field in burned zone shows substantially increased turbulent kinetic energy, which is highly anisotropic due to reaction kinematics across thin f1amelets. The transverse component may be larger than the axial component for a distributed pdf of the flamelet orientation angle, while the opposite occurs due to redistribution of turbulent kinetic energy and flamelet orientation normal to the flow at the end of a flame brush. The major source or sink terms of turbulent kinetic energy are the interfacial transfer by the mean reaction rate and the work terms by fluctuating pressure and velocity on a flame surface. Ad hoc modeling of some interfacial terms may be required for further application of the two-fluid model in turbulent combustion simulations.

  • PDF

체적팽창효과를 고려한 예혼합화염과 와동의 상호작용에 관한 연구 (The Interaction of Vortex and Premixed Flame with Consideration of Volume Expansion Effect)

  • 정의헌;권세진
    • 한국전산유체공학회:학술대회논문집
    • /
    • 한국전산유체공학회 1998년도 추계 학술대회논문집
    • /
    • pp.204-210
    • /
    • 1998
  • A method is developed to include the effect of volume expansion in the description of the flame dynamics using G-equation. Line volume-source is used to represent the effect of the exothermic process of combustion with source strength determined by the density difference between the burned and the unburned region. Volume expansion adjusts the flow field to accommodate the increased volume flow rate crossing the flame front. Test result predicted the measured velocity field qualitatively. The method was applied to study the interaction of vortex and premixed flame. Increased volume expansion did not change the initial growth rate of flame area. However, the residence time and flame surface area increased with higher expansion ratios.

  • PDF

수소 예혼합기의 정상 및 이상연소에 관한 수치해석 (A Numerical Study on Normal and Abnormal Combustion in Hydrogen Premixture)

  • 손채훈;정석호
    • 대한기계학회논문집
    • /
    • 제19권8호
    • /
    • pp.1989-1998
    • /
    • 1995
  • Characteristics of the flame propagation for normal and abnormal combustion in hydrogen premixture in a cylindrical constant-volume combustion chamber are studied numerically. A detailed hydrogen oxidation kinetic mechanism, mixture transport properties and a model describing spark ignition process are used. The calculated pressure-time history of the stable deflagration wave propagation agrees well with the experiment. The ignition of the premixture in the unburned gas, initiated by the hot spot, causes a transition from deflagration to detonation under some initial temperature and pressure. Under the initial conditions with high temperature and pressure, excessive ignition energy initiates a strong blast wave and a detonation wave that follows. The chemical reaction in the detonation wave is much more vigorous than that in the deflagration wave and the peak pressure in the detonation wave is much higher than the equilibrium value.

영역분할조건평균법에 근거한 난류예혼합화염내 난류운동에너지 생성에 관한 연구 (Analysis of Flame Generated Turbulence for a Turbulent Premixed Flame with Zone Conditional Averaging)

  • 임용훈;허강열
    • 한국연소학회:학술대회논문집
    • /
    • 대한연소학회 2003년도 제27회 KOSCO SYMPOSIUM 논문집
    • /
    • pp.49-56
    • /
    • 2003
  • Mathematical formulation of the zone conditional two-fluid model is established to consider flame-generated turbulence in premixed turbulent combustion. The conditional statistics of major flow variables are investigated to understand the mechanism of flame generated turbulence. The flow field in burned zone shows substantially increased turbulent kinetic energy, which is highly anisotropic due to reaction kinematics across thin flamelets. The transverse component of rms velocities in burned zone become larger than axial component in the core of turbulent flame brush. The major source or sink terms of turbulent kinetic energy are the interfacial transfer by the mean reaction rate and the work terms by fluctuating pressure and velocity on a flame surface.

  • PDF

이중 동축류 버너에서 부분예혼합화염의 특성에 관한 연구 (Characteristics of Partially Premixed Flames in Double Concentric Burner)

  • 권성준;차민석;정석호
    • 한국연소학회:학술대회논문집
    • /
    • 한국연소학회 1998년도 제17회 KOSCI SYMPOSIUM 논문집
    • /
    • pp.131-138
    • /
    • 1998
  • Flame characteristics in a double concentric burner has been studied experimentally. Air is supplied through a central nozzle, methane/air premixture is supplied in a inner annular part, and coflowing shield air is supplied to minimize outside disturbances. Depending on flow rate and concentration, various flame shapes can be observed. As the flow rate difference between central air jet and annular premixed jet is varied, several distinctive flames are observed. Conditions of partially premixed flames are further investigated; nozzle attached rich premixed flame, inner lifted flame, and outer lifted flame. Using the Abel transformation of digitized images of flames, cross- sectional images of flames can be obtained, from which overall structure of flames can be identified. PLIF measurement of OR radical was also conducted. OR radicals were mainly distributed in diffusion flame region. From the difference of OR distribution between nozzle attached and lifted flames, similarity of OR distribution between tribrachial flame and lifted flames in this study are observed.

  • PDF

난류 부분예혼합화염과 로테이팅 아크 플라즈마를 이용한 난연성 유증기의 연소처리 (Reduction of Lean VOC Emission by Reforming with a Rotating Arc Plasma and Combustion with a Turbulent Partially-Premixed Flame)

  • 안태국;이대훈;박선호
    • 한국연소학회지
    • /
    • 제22권1호
    • /
    • pp.23-31
    • /
    • 2017
  • Large-scale fuel tanks emit massive amount of hardly-combustible VOC mixtures which are light hydrocarbon species in dilution with nitrogen and carbon dioxide. We have developed a lab-scale burner to combust those VOC mixtures by use of a turbulent partially-premixed flame as a pilot flame. For a higher HC treatment ratio, the mixture gases were reformed by a rotating arc plasma device. The results showed that the nitrogen mole fraction and the injecting speed of the VOC mixture influence on the performance of the burner. It was also found that the size of the pilot flame and the power supplied to the plasma device determine the overall HC treatment ratio and the concentrations of CO and NOx in the exhaust gas.

유증기 연소처리를 위한 난류 부분예혼합화염의 활용 및 유동장 가시화 (Utilization and Visualization of Turbulent Partially-premixed Flame for Combustion of Inert-gas-diluted VOC)

  • 안태국;남연우;박선호
    • 한국연소학회:학술대회논문집
    • /
    • 한국연소학회 2015년도 제51회 KOSCO SYMPOSIUM 초록집
    • /
    • pp.193-196
    • /
    • 2015
  • Combustion of low concentration VOC in inert gas around the flammability limit has been experimentally studied. Streams of nitrogen and propane mixture with various compositions and flow conditions were treated by a turbulent partially-premixed pilot flame. HC and CO contents in exhaust gas measured and the flow patterns were visualized. The results suggested that there exists an optimal mixture velocity range for efficient combustion treatment for each flow condition and composition of the mixture.

  • PDF

스월-안정화 연소기에서 혼합기 공진모드가 동적 연소특성에 미치는 영향 (Effect of Mixing Section Resonance Mode on Dynamic Combustion Characteristics in a Swirl-Stabilized Combustor)

  • 한선우;이신우;황동현;안규복
    • 한국분무공학회지
    • /
    • 제27권1호
    • /
    • pp.18-25
    • /
    • 2022
  • Hot-firing tests were performed to experimentally confirm the effect of the eigenmode in the fuel-air mixing section on combustion instability by changing mixing section length, inlet mean velocity, equivalence ratio, and swirler geometry. A premixed gas composed of air and ethylene was supplied to the combustion chamber through an mixing section and an axial swirler. As the mixing section length increased, the inlet velocity perturbation decreased, but the combustion instability increased more. It was found that the resonance frequency of the first longitudinal mode in the mixing section shifted to the third longitudinal mode as the length of the mixing section increased. The results implied that the transition of the resonace frquency by changing the length of the mixing section might cause combustion instability.