Air Entrainment in a Jet Flame Stabilizer in Supersonic Flow.

1976 ◽  
Author(s):  
R. A. Cookson
Keyword(s):  
Supersonic Flow ◽  
Air Entrainment ◽  
Jet Flame

Computation of Nitric Oxide and Soot Emissions From Turbulent Diffusion Flames

1985 ◽  
Vol 107 (1) ◽  
pp. 48-53 ◽  
Author(s):  
T. Ahmad ◽  
S. L. Plee ◽  
J. P. Myers
Keyword(s):  
Diffusion Flames ◽  
Soot Oxidation ◽  
Air Entrainment ◽  
Reaction Rates ◽  
Gas Jet ◽  
Maximum Temperature ◽  
Injection Velocity ◽  
Soot Emission ◽  
No Emission ◽  
Jet Flame

An existing steady-state, locally homogeneous flow model of turbulent spray combustion was modified to predict NO emission from a spray flame and soot emission from a gas-jet flame. The effect of turbulent fluctuations on the reaction rates was accounted for. The predicted NO emission from an n-pentane spray with a changing injection velocity could be correlated with the convective time scale of the flow. Calculation of soot emission from a burning turbulent gas jet indicated that the centerline soot concentration reaches a peak upstream of the maximum temperature location and then decreases due to soot oxidation and dilution by air entrainment.

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.

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.

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.

Measurement of residence time, air entrainment rate, and base pressure in the near wake of a cylindrical body in supersonic flow

AIAA Journal ◽  
1989 ◽  
Vol 27 (11) ◽  
pp. 1524-1529 ◽  
Author(s):  
D. W. Roberds ◽  
W. K. McGregor ◽  
B. W. Hartsfield ◽  
R. J. Schulz ◽  
R. P. Rhodes
Keyword(s):  
Supersonic Flow ◽  
Residence Time ◽  
Cylindrical Body ◽  
Air Entrainment ◽  
Base Pressure ◽  
Entrainment Rate ◽  
Near Wake ◽  
Air Entrainment Rate

Effects of Solid Shield and Shroud on Plasma Jet Flame in APS Process

2014 ◽  
Author(s):  
Ting Liu ◽  
Lili Zheng ◽  
Guanzhong Zhang ◽  
Hui Zhang
Keyword(s):  
Plasma Jet ◽  
Air Entrainment ◽  
Atmospheric Plasma ◽  
Inert Gas ◽  
Jet Flows ◽  
Gas Velocity ◽  
Negative Effects ◽  
Injection Angle ◽  
Jet Flame ◽  
Gas Shroud

Gas entrainment occurs in atmospheric plasma spray (APS) after plasma jet flows into the cold surroundings, resulting in rapid decaying of speed and unwanted oxidation. Installing a solid shield or inserting a gas shroud at the end of the nozzle may be helpful to reduce air entrainment. Effects of solid shield and inert gas shroud on plasma jet are investigated numerically. It is found that solid shield and gas shroud will expand high temperature field of plasma jet in both axial and radial direction, consequently, enabling a thorough reaction of oxygen content for virtually oxygen free plasma jet. The mass fraction of the O2 gas in the plasma flow outside the shield decreases with the increase of the inert gas velocity, which maintains nearly zero in the solid shield. Inert gas velocity and its injection angle turn out to be important factors to offset the negative effects of solid shield on the main flow. It is demonstrated that the flow field is less affected when the inert gas is axially injected with the inlet velocity of 150m/s. Ar is more appropriate than N2 as an inert gas, which is mainly attributed to its physical properties.

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