Effects of Jet Reynolds Number on the Performance of Axisymmetric and Nonaxisymmetric Gas Burner Flames

1999 ◽  
Author(s):  
Azfar Kamal ◽  
S. R. Gollahalli
Keyword(s):  
Reynolds Number ◽  
Heat Release ◽  
Flame Temperature ◽  
Air Entrainment ◽  
Flame Length ◽  
Temperature Profiles ◽  
Jet Flame ◽  
Burner Exit ◽  
Equivalent Area ◽  
Emission Index

Abstract An investigation of the effects of burner exit Reynolds number (9,400–19,000) on the relative effects of burner geometry (circular and elliptic with an aspect ratio 2–4) in a propane jet flame is presented. Circular and elliptic burners of the equivalent area of a circular burner of diameter 5.02 mm were studied. Air entrainment into the nonreacting jets, emission indices of NO, NO2, and CO, visible flame length, flame temperature profiles, radiative fraction of heat release, and soot concentration were measured. Results show that an increase in Re decreases the benefits of higher air entrainment into the flame due to elliptic burner geometry. Similarly, the effects of changes in NO and CO emission indices level off at higher burner Re. The measurements of visible flame length, radiative fraction flame heat release, temperature profiles, and soot concentrations corroborate and offer the explanations for the observed emission index results.

Effects of Jet Reynolds Number on the Performance of Axisymmetric and Nonaxisymmetric Gas Burner Flames

2000 ◽  
Vol 123 (2) ◽  
pp. 167-172 ◽  
Author(s):  
Azfar Kamal ◽  
S. R. Gollahalli
Keyword(s):  
Reynolds Number ◽  
Heat Release ◽  
Flame Temperature ◽  
Air Entrainment ◽  
Flame Length ◽  
Temperature Profiles ◽  
Jet Flame ◽  
Burner Exit ◽  
Equivalent Area ◽  
Emission Index

An investigation of the effects of burner exit Reynolds number on the relative effects of burner geometry (circular and elliptic with an aspect ratio 2:4) in a propane jet flame is presented. Circular and elliptic burners of the equivalent area of a circular burner of diameter 5.2 mm were studied. Air entrainment into the nonreacting jets, emission indices of NO, NO2, and CO, visible flame length, flame temperature profiles, radiative fraction of heat release, and soot concentration were measured. Results show that an increase in Re decreases the benefits of higher air entrainment into the flame due to elliptic burner geometry. Similarly, the effects of changes in NO and CO emission indices level off at higher burner Re. The measurements of visible flame length, radiative fraction of heat release, temperature profiles, and soot concentrations corroborate the observed emission index results.

Trajectory and Characteristics of Buoyancy and Momentum Dominated Horizontal Jet Flames From Circular and Elliptic Burners

2005 ◽  
Vol 128 (4) ◽  
pp. 300-310 ◽  
Author(s):  
Tracy Smith ◽  
Chendhil Periasamy ◽  
Benjamin Baird ◽  
S. R. Gollahalli
Keyword(s):  
Nitric Oxide ◽  
Reynolds Number ◽  
Flame Temperature ◽  
Major Axis ◽  
Equivalent Diameter ◽  
Flame Stability ◽  
Temperature Profiles ◽  
Burner Exit ◽  
Wide Range ◽  
Nitric Oxide Emissions

Relative effects of buoyancy and momentum on the characteristics of horizontally oriented circular (Circ) and elliptic (E) burner flames in a quiescent environment over a wide range of jet exit velocities are presented. The major axis of the elliptic burner was oriented horizontally and vertically (referred to as Emaj and Emin flames, respectively). Propane was used as fuel and a small amount of hydrogen was piloted to attach flames to the burner. Global flame characteristics such as flame dimensions, centerline trajectory, emission indices (EI) and radiative fraction, and in-flame transverse concentration and temperature profiles were measured. At a jet exit Reynolds number (Rej) of 2000, based on the area-equivalent diameter of the burner, the flame characteristics were affected by the burner geometry and its orientation. Also, the vertical dimension of the burner exit dictated buoyancy effects. At Rej=12,500, the influence of burner geometry or its orientation was negligible. Elliptic burner flames exhibited lower liftoff and blowout velocities than circular burner flames. Furthermore, the flame stability and nitric oxide emissions were not much affected by the orientation of elliptic burner. Although the elliptic burners produced higher EINO at lower jet exit velocities, the variation in EINO among three burners (Circ, Emaj, and Emin) was insignificant at higher velocities. Some effects of buoyancy on EICO were observed at lower jet exit velocities and the EICO was the lowest for the burners with largest buoyancy flux. Elliptic burner flames produced greater peak flame temperature than the corresponding circular burner flames under most conditions.

Flame Patterns and Combustion Intensity Behind Rifled Bluff-Body Frustums

2013 ◽  
Vol 135 (12) ◽  
Author(s):  
Kuo C. San ◽  
Yu Z. Huang ◽  
Shun C. Yen
Keyword(s):  
Bluff Body ◽  
Flow Behavior ◽  
Turbulent Flame ◽  
Flame Temperature ◽  
Flame Length ◽  
Turbulent Flames ◽  
Temperature Profiles ◽  
Lifted Flames ◽  
Direct Color ◽  
Jet Nozzle

Rifled fillisters were milled on cannular frustums to modulate flow behavior and to increase the turbulence intensity (TI). The TI and combustion intensity were compared in four configurations of frustums—unrifled, inner-rifled, outer-rifled, and two-faced rifled. The flame patterns and flame lengths were observed and measured by direct-color photography. The temperature profiles and (total) combustion intensity were detected and calculated with an R-type thermocouple. Three flame patterns (jet, flickering, and lifted flames) were defined behind the pure-jet nozzle. Four flame patterns (jet, flickering, bubble, and turbulent flames) were observed behind the unrifled frustum. The bluff-body frustum changes the lifted flame to turbulent flame due to a high T.I at high central-fuel velocity (uc). The experimental data showed that the grooved rifles improved the air-propane mixing, which then improved the combustion intensity. The rifled mechanism intensified the swirling effect and then the flame-temperature profiles were more uniform than those behind the pure-jet nozzle. The increased TI also resulted in the shortest flame length behind the two-faced rifled frustum and increased the total combustion intensity.

Orifice Diameter Effects on Diesel Fuel Jet Flame Structure

2005 ◽  
Vol 127 (1) ◽  
pp. 187-196 ◽  
Author(s):  
Lyle M. Pickett ◽  
Dennis L. Siebers
Keyword(s):  
Diesel Fuel ◽  
Direct Injection ◽  
Flame Structure ◽  
Air Entrainment ◽  
Flame Length ◽  
Turbulent Flames ◽  
Orifice Diameter ◽  
Jet Flame ◽  
Fuel Jet ◽  
Lift Off

The effects of orifice diameter on several aspects of diesel fuel jet flame structure were investigated in a constant-volume combustion vessel under heavy-duty direct-injection (DI) diesel engine conditions using Phillips research grade #2 diesel fuel and orifice diameters ranging from 45 μm to 180 μm. The overall flame structure was visualized with time-averaged OH chemiluminescence and soot luminosity images acquired during the quasi-steady portion of the diesel combustion event that occurs after the transient premixed burn is completed and the flame length is established. The lift-off length, defined as the farthest upstream location of high-temperature combustion, and the flame length were determined from the OH chemiluminescence images. In addition, relative changes in the amount of soot formed for various conditions were determined from the soot incandescence images. Combined with previous investigations of liquid-phase fuel penetration and spray development, the results show that air entrainment upstream of the lift-off length (relative to the amount of fuel injected) is very sensitive to orifice diameter. As orifice diameter decreases, the relative air entrainment upstream of the lift-off length increases significantly. The increased relative air entrainment results in a reduced overall average equivalence ratio in the fuel jet at the lift-off length and reduced soot luminosity downstream of the lift-off length. The reduced soot luminosity indicates that the amount of soot formed relative to the amount of fuel injected decreases with orifice diameter. The flame lengths determined from the images agree well with gas jet theory for momentum-driven nonpremixed turbulent flames.

Experimental study of welding region effects on upward flame spread over textile membranes

2018 ◽  
Vol 89 (10) ◽  
pp. 2041-2053 ◽  
Author(s):  
Yunji Gao ◽  
Guoqing Zhu ◽  
Mengwei Yu ◽  
Feng Guo ◽  
Yu Xia ◽  
...  
Keyword(s):  
Flame Spread ◽  
Ignition Time ◽  
Flame Temperature ◽  
Air Entrainment ◽  
Flame Length ◽  
Flame Height ◽  
Spread Rate ◽  
Pyrolysis Gas ◽  
Upward Flame Spread ◽  
Pyrolysis Spread Rate

Textile membranes are used widely as a main architectural material in membrane structure buildings. However, very few studies have been conducted to investigate the flame spread characteristics of textile membranes, especially in the case of upward flame spread. In this paper, the effects of welding region on upward flame spread were investigated experimentally using sample sheets of textile membranes 60 cm tall and 6 cm wide with and without welding region. The corresponding observations are as follows: the width of flame with welding region is narrower than that without welding region; flame height, pyrolysis height, preheating length, flame length, and pyrolysis spread rate decrease significantly in the presence of a welding region, while ignition time increases; flame temperature decreases in the presence of a welding region, and temperature along the welding region is higher than that near the edge. The welding region effects are as follows: in presence of a welding region, the thickness of welding region increases and, accordingly, ignition time shows an increase, leading to relatively low pyrolysis gas generated per unit time and relatively less heat released; in addition, a relatively larger pyrolysis gas concentration gradient over the width for welding membranes results in a relatively stronger air entrainment occurring at the sample sides, taking away part of the heat flux and narrowing the flame width. Thus, the presence of a welding region has negative effects of increasing ignition time and reducing preheating length on upward flame spread over textile membranes, eventually decreasing the pyrolysis spread rate.

Combustion Characteristics of Spray Flames of Canola Methyl Ester/Diesel Blends in a Furnace

2013 ◽  
Author(s):  
Cory D. Morton ◽  
Victor H. Tran ◽  
Ramkumar N. Parthasarathy ◽  
Subramanyam R. Gollahalli
Keyword(s):  
Methyl Ester ◽  
Heat Release ◽  
Volume Fraction ◽  
Flame Temperature ◽  
Soot Volume Fraction ◽  
Combustion Characteristics ◽  
Spray Flame ◽  
Spray Flames ◽  
Refractory Bricks ◽  
Emission Index

The combustion characteristics of spray flames of canola methyl ester (CME) and blends with diesel fuel within a re-radiating environment were studied. The combustion chamber was lined with refractory bricks that were preheated to about 725 K (1305 °R). The flow rates of the fuels provided a constant heat release rate of about 7.33 kW (25,000 BTU/hr) at atmospheric pressure. Measurements of flame temperature, in-flame concentrations, global emissions, flame radiation and soot volume fraction were taken. The global CO emission index was significantly lower in the biofuel blend spray flames compared to that of the diesel spray flame. The global NO emission index was comparable for all spray flames, which agreed with peak flame temperature and in-flame NO concentration measurements. The radiative fraction of heat release was also comparable for all spray flames.

Orifice Diameter Effects on Diesel Fuel Jet Flame Structure

2001 ◽  
Author(s):  
Lyle M. Pickett ◽  
Dennis L. Siebers
Keyword(s):  
Diesel Fuel ◽  
Direct Injection ◽  
Flame Structure ◽  
Air Entrainment ◽  
Flame Length ◽  
Turbulent Flames ◽  
Orifice Diameter ◽  
Jet Flame ◽  
Fuel Jet ◽  
Lift Off

Abstract The effects of orifice diameter on several aspects of diesel fuel jet flame structure were investigated in a constant-volume combustion vessel under heavy-duty, direct-injection (DI) diesel engine conditions using Phillips research grade #2 diesel fuel and orifice diameters ranging from 45 μm to 180 μm. The overall flame structure was visualized with time-averaged OH chemiluminescence and soot luminosity images acquired during the quasi-steady portion of the diesel combustion event that occurs after the transient premixed burn is completed and the flame length is established. The lift-off length, defined as the farthest upstream location of high-temperature combustion, and the flame length were determined from the OH chemiluminescence images. In addition, relative changes in the amount of soot formed for various conditions were determined from the soot incandescence images. Combined with previous investigations of liquid-phase fuel penetration and spray development, the results show that air entrainment upstream of the lift-off length (relative to the amount of fuel injected) is very sensitive to orifice diameter. As orifice diameter decreases, the relative air entrainment upstream of the lift-off length increases significantly. The increased relative air entrainment results in a reduced overall average equivalence ratio in the fuel jet at the lift-off length and reduced soot luminosity downstream of the lift-off length. The reduced soot luminosity indicates that the amount of soot formed relative to the amount of fuel injected decreases with orifice diameter. The flame lengths determined from the images agree well with gas jet theory for momentum-driven, non-premixed turbulent flames.

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 Effects of Turbulence on the Combustion Properties of Partially Premixed Flames of Canola Methyl Ester and Diesel Blends

2011 ◽  
Vol 2011 ◽  
pp. 1-13 ◽  
Author(s):  
N. Dhamale ◽  
R. N. Parthasarathy ◽  
S. R. Gollahalli
Keyword(s):  
Reynolds Number ◽  
Methyl Ester ◽  
Alternative Energy ◽  
Volume Fraction ◽  
Energy Resource ◽  
Soot Volume Fraction ◽  
Air Entrainment ◽  
Combustion Properties ◽  
Partially Premixed ◽  
Emission Index

Canola methyl ester (CME) is a biofuel that is a renewable alternative energy resource and is produced by the transesterification of canola oil. The objective of this study was to document the effects of turbulence on the combustion characteristics of blends of CME and No 2 diesel fuel in a partially-premixed flame environment. The experiments were conducted with mixtures of pre-vaporized fuel and air at an initial equivalence ratio of 7 and three burner exit Reynolds numbers, 2700, 3600, and 4500. Three blends with 25, 50, and 75% volume concentration of CME were studied. The soot volume fraction was highest for the pure diesel flames and did not change significantly with Reynolds number due to the mutually compensating effects of increased carbon input rate and increased air entrainment as the Reynolds number was increased. The global NOx emission index was highest and the CO emission index was the lowest for the pure CME flame, and varied non-monotonically with biofuel content in the blend The mean temperature and the NOx concentration at three-quarter flame height were generally correlated, indicating that the thermal mechanism of NOx formation was dominant in the turbulent biofuel flames also.

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