scholarly journals An Experimental and Computational Study of Swirling Hydrogen Jet Diffusion Flames

1995 ◽  
Author(s):  
M. S. Anand ◽  
F. Takahashi ◽  
M. D. Vangsness ◽  
M. D. Durbin ◽  
W. J. Schmoll
Keyword(s):  
Diffusion Flames ◽  
Computational Study ◽  
Laser Doppler Velocimeter ◽  
Reacting Flow ◽  
Jet Diffusion Flames ◽  
Burner Exit ◽  
Mean And Variance ◽  
Joint Velocity ◽  
Anti Stokes ◽  
Good Agreement

Computations using the joint velocity-scalar probability density function (pdf) method as well as benchmark quality experimental data for swirling and nonswirling hydrogen jet diffusion flames are reported. Previous studies of diffusion flames reported in literature have been limited to nonswirling flames and have had no detailed velocity data reported in the developing (near-nozzle) region of the flames. The measurements and computations reported herein include velocities (mean and higher moments up to fourth order) and temperature (mean and variance) near the burner exit and downstream locations up to 26.5 jet diameters. The velocities were measured with a three-component laser Doppler velocimeter (LDV) and the temperature was measured using coherent anti-Stokes Raman spectroscopy (CARS). The joint pdf method offers significant advantages over conventional methods for computing turbulent reacting flow, and the computed results are in good agreement with data. This study serves to present data that can be used for model validation as well as to further validate the joint pdf method.

An Experimental and Computational Study of Swirling Hydrogen Jet Diffusion Flames

1997 ◽  
Vol 119 (2) ◽  
pp. 305-314 ◽  
Author(s):  
M. S. Anand ◽  
F. Takahashi ◽  
M. D. Vangsness ◽  
M. D. Durbin ◽  
W. J. Schmoll
Keyword(s):  
Diffusion Flames ◽  
Computational Study ◽  
Laser Doppler Velocimeter ◽  
Reacting Flow ◽  
Jet Diffusion Flames ◽  
Burner Exit ◽  
Mean And Variance ◽  
Joint Velocity ◽  
Anti Stokes ◽  
Good Agreement

Computations using the joint velocity-scalar probability density function (pdf) method as well as benchmark quality experimental data for swirling and nonswirling hydrogen jet diffusion flames are reported. Previous studies of diffusion flames reported in the literature have been limited to nonswirling flames and have had no detailed velocity data reported in the developing (near-nozzle) region of the flames. The measurements and computations reported herein include velocities (mean and higher moments up to fourth order) and temperature (mean and variance) near the burner exit and downstream locations up to 26.5 jet diameters. The velocities were measured with a three-component laser-Doppler velocimeter (LDV) and the temperature was measured using coherent anti-Stokes Raman spectroscopy (CARS). The joint pdf method offers significant advantages over conventional methods for computing turbulent reacting flow, and the computed results are in good agreement with data. This study serves to present data that can be used for model validation as well as to validate further the joint pdf method.

Turbulent Jet Diffusion Flames in Environments Containing Some Premixed Fuel

1988 ◽  
Vol 110 (3) ◽  
pp. 146-150 ◽  
Author(s):  
M. G. Kibrya ◽  
G. A. Karim
Keyword(s):  
Diffusion Flame ◽  
Diffusion Flames ◽  
Turbulent Jet ◽  
Gaseous Fuels ◽  
Model Based ◽  
Jet Diffusion Flames ◽  
Experimental Values ◽  
Additional Fuel ◽  
Good Agreement

The blowout limit of a methane jet diffusion flame is extended by adding small concentrations of a fuel to the surrounding air. The improvement is predicted theoretically with a model based on the stoichiometric changes within the jet and in its vicinity due to the presence of this additional fuel. Good agreement was obtained between such a prediction and the corresponding experimental values for a range of gaseous fuels in the surrounding air.

Structure of Turbulent Hydrogen Jet Diffusion Flames With or Without Swirl

1996 ◽  
Vol 118 (4) ◽  
pp. 877-884 ◽  
Author(s):  
F. Takahashi ◽  
M. D. Vangsness ◽  
M. D. Durbin ◽  
W. J. Schmoll
Keyword(s):  
Turbulent Combustion ◽  
Laser Doppler Velocimetry ◽  
Diffusion Flames ◽  
Near Field ◽  
Turbulent Flame ◽  
Flame Zone ◽  
Jet Diffusion Flames ◽  
Air Jet ◽  
The Mean ◽  
Anti Stokes

The near-field turbulent structure of double-concentric hydrogen-air jet diffusion flames, with or without swirl, has been investigated using conditionally sampled, three-component laser-Doppler velocimetry and coherent anti-Stokes Raman spectroscopy. The turbulent flame zone became thinner and shifted inward as the mean jet velocity was increased, whereas swirl created a radial velocity even at the jet-exit plane, thereby broadening and shifting the flame zone outward. The probability-density functions of velocity components, their 21 moments (up to fourth order), mean temperature, and root-mean-square temperature fluctuation were determined in the near field. The data can be used to validate advanced turbulent combustion models.

On the Scaling of the Visible Lengths of Jet Diffusion Flames

1996 ◽  
Vol 118 (2) ◽  
pp. 128-133 ◽  
Author(s):  
X. Li
Keyword(s):  
Reynolds Number ◽  
Diffusion Flames ◽  
Flame Length ◽  
Turbulent Flames ◽  
Turbulent Regime ◽  
Buoyancy Effect ◽  
Transitional Regime ◽  
Jet Diffusion Flames ◽  
Burner Exit ◽  
Turbulent Diffusion Flames

Length of jet diffusion flames is of direct importance in many industrial processes and is analyzed by applying scaling method directly to the governing partial differential equations. It is shown that for jet-momentum-dominated diffusion flames, when the buoyancy effects are neglected, the flame length normalized by the burner exit diameter increases linearly with the Reynolds number at the burner exit in the laminar burning regime and decreases in inverse proportion to the Reynolds number in the transitional regime. For turbulent diffusion flames, the normalized flame lengths are independent of the burner exit flow conditions. It is further found that for vertical upward flames, the buoyancy effect increases the flame length in the laminar and transitional regime and reduces the length in the turbulent regime; while for vertical downward flames, the buoyancy effect decreases the flame length in the laminar and transitional regime and increases the length in the turbulent regime, provided that jet momentum is dominated, and there is no flame spreading out and then burning upward like a downward-facing pool fire. Hence, for turbulent flames the flame lengths depend on the Froude number, Fr, and increase (or decrease) slightly as Fr increases for upward (or downward) flames. By comparison, it is found that the foregoing theoretical results are in good agreement with the experimental observations reported in literature.

scholarly journals An Experimental and Computational Study of a Swirl-Stabilized Premixed Flame

2009 ◽  
Author(s):  
Ashoke De ◽  
Shengrong Zhu ◽  
Sumanta Acharya
Keyword(s):  
Flame Front ◽  
Computational Study ◽  
Tangential Velocity ◽  
Reaction Rates ◽  
Individual Species ◽  
Reacting Flow ◽  
Eddy Simulation ◽  
Precessing Vortex Core ◽  
The Individual ◽  
Good Agreement

An unconfined strongly swirled flow is investigated for different Reynolds numbers using particle image velocimetry (PIV) and Large Eddy Simulation (LES) with a Thickened Flame (TF) model. Both reacting and non-reacting flow results are presented. In the LES-TF approach, the flame front is resolved on the computational grid through artificial thickening and the individual species transport equations are directly solved with the reaction rates specified using Arrhenius chemistry. Good agreement is found when comparing predictions with the experimental data for the non-reacting cases studied. For the reacting flows, the mean axial velocity profiles are in good agreement with measurements at lower Re; at high Re, the computations show a more compact and attached flame whereas experimental observations show a slightly lifted flame. Tangential velocity predictions consistently show the peak at the flame front location while measurements show greater radial spreading of the tangential momentum. The predicted RMS fluctuations exhibit a double-peak profile with one peak in the burnt and the other in the unburnt region. The measured and predicted heat release distributions are in qualitative agreement with each other and exhibit the highest values along the inner edge of the shear layer. The precessing vortex core (PVC) is clearly observed in both the non-reacting and reacting cases. However, it appears more axially-elongated for the reacting cases.

Fuel mixing effect on the flickering of jet diffusion flames

2010 ◽  
Vol 225 (1) ◽  
pp. 155-162 ◽  
Author(s):  
J Li ◽  
Y Zhang
Keyword(s):  
High Speed ◽  
Diffusion Flames ◽  
Digital Camera ◽  
Reacting Flow ◽  
Buoyant Jet ◽  
Vortical Structures ◽  
Mixed Fuel ◽  
Jet Diffusion Flames ◽  
Key Factor ◽  
Flickering Frequency

An experimental study has been performed for a buoyant jet diffusion flame, which was observed to oscillate at different frequencies spatially. The flame dynamics and structure were visualized by a commercial digital camera and a high-speed camera. Mixed fuel of methane and propane at certain proportion was found to generate very different vortex shedding behaviours. As a result, the flickering frequency of a methane/propane 1:1 mixture can be half of that of typically observed for pure methane or propane flame. The distance between adjacent flame puffs or the size of vortical structures in the reacting flow field, which can be modified by the fuel composition, was identified to be the key factor that affects the flickering frequencies. Repeated tests confirmed that mixed fuel at certain proportions can have a significant effect on the flame flickering frequency through the modification of vortex structure and dynamics.

scholarly journals The Effect of Co-Flowing Stream Velocities on the Flow Characteristics of Jets Issuing From Elliptic Nozzles

1997 ◽  
Author(s):  
N. Papanikolaou ◽  
I. Wierzba
Keyword(s):  
Diffusion Flames ◽  
Flow Characteristics ◽  
Nozzle Geometry ◽  
Laser Doppler Velocimeter ◽  
Circular Nozzle ◽  
Jet Diffusion Flames ◽  
Aspect Ratios ◽  
Air Stream ◽  
Lifted Flames ◽  
Flowing Stream

The flow structure of cold and ignited jets issuing into a co-flowing air stream was experimentally studied using a laser Doppler velocimeter. Methane was employed as the jet fluid discharging from circular and elliptic nozzles with aspect ratios varying from 1.29 to 1.60. The diameter of the circular nozzle was 4.6 mm and the elliptic nozzles had approximately the same exit area as that of the circular nozzle. These non-circular nozzles were employed in order to increase the stability of attached jet diffusion flames. The time-averaged velocity and r.m.s. value of the velocity fluctuation in the streamwise and transverse directions were measured over the range of co-flowing stream velocities corresponding to different modes of flame blowout that are identified as either lifted or attached flames. On the basis of these measurements, attempts were made to explain the existence of an apparent optimum aspect ratio for the blowout of attached flames observed at higher values of co-flowing stream velocities. The insensitivity of the blowout limits of lifted flames to nozzle geometry observed in our previous work at low co-flowing stream velocities was also explained.

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