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.

Issue Section:
Internal Combustion Engines
Keywords:
diesel engines, jets, fuel, sprays, combustion, chemiluminescence, flames
Topics:
Chemiluminescence, Combustion, Density, Diesel, Flames, Fuels, Light emission, Soot, Temperature
1.
Dec
,
J. E.
,
1997
, “
A Conceptual Model of DI Diesel Combustion Based on Laser-Sheet Imaging
,”
Trans. SAE
,
106, Sec. 3
, pp.
1319
–
1348
(SAE Technical Paper 970873).
2.
Chomiak, J., and Karlsson, A., 1996, “Flame Liftoff in Diesel Sprays,” Twenty-Sixth Symposium (International) on Combustion, The Combustion Institute, Pittsburgh, pp. 2557–2504.
3.
Siebers, D. L., and Higgins, B., 2001, “Flame Lift-Off on Direct-Injection Diesel Sprays Under Quiescent Conditions,” SAE Technical Paper 2001-01-0530.
4.
Higgins, B. S., and Siebers, D. L., 2001, “Measurement of the Flame Lift-Off Location on DI Diesel Sprays Using OH Chemiluminescence,” SAE Technical Paper 2001-01-0918.
5.
Siebers, D. L., and Higgins, B. S., 2000, “Effects of Injector Conditions on the Flame Lift-Off Length of DI Diesel Sprays,” Conference on Thermofluidynamic Processes in Diesel Engines, Valencia, Spain, Sept. 14–15.
6.
Naber
,
J. D.
, and
Siebers
,
D. L.
,
1996
, “
Effects of Gas Density and Vaporization on Penetration and Dispersion of Diesel Sprays
,”
Trans. SAE
,
105, Sec. 3
, pp.
82
–
111
(SAE Technical Paper 960034).
7.
Siebers
,
D. L.
,
1998
, “
Liquid-Phase Fuel Penetration in Diesel Sprays
,”
Trans. SAE
,
107, Sec. 3
, pp.
1205
–
1227
(SAE Technical Paper 980809).
8.
Siebers
,
D. L.
,
1985
, “
Ignition Delay Characteristics of Alternative Diesel Fuels: Implications on Cetane Number
,”
Trans. SAE
,
94, Sec. 7
, pp.
673
–
686
(SAE Technical Paper 852102).
9.
Oren
,
D. C.
,
Wahiduzzaman
,
S.
, and
Ferguson
,
C. R.
,
1984
, “
A Diesel Combustion Bomb: Proof of Concept
,”
Trans. SAE
,
93, Sec. 5
, pp.
945
–
960
(SAE Technical Paper 841358).
10.
Durrett, R. P., Oren, D. C., and Ferguson, C. R., 1987, “A Multidimensional Data Set for Diesel Combustion Model Validation: I—Initial Conditions, Pressure History and Spray Shapes,” SAE Technical Paper 872087.
11.
Siebers, D. L., 1999, “Scaling Liquid-Phase Fuel Penetration in Diesel Sprays Based on Mixing-Limited Vaporization,” SAE Technical Paper 1999-01-0528.
12.
Naber
,
J. D.
,
Siebers
,
D. L.
,
Caton
,
J. A.
,
Westbrook
,
C. K.
, and
Di Julio
,
S. S.
,
1994
, “
Natural Gas Autoignition Under Diesel Conditions: Experiments and Chemical Kinetic Modeling
,”
Trans. SAE
,
103, Sec. 4
, pp.
1735
–
1753
(SAE Technical Paper 942034).
13.
Naber
,
J. D.
, and
Siebers
,
D. L.
,
1998
, “
Hydrogen Combustion Under Diesel Engine Conditions
,”
Int. J. Hydrogen Energy
,
23
(
5
), pp.
363
–
371
.
14.
Peters, N., 2000, Turbulent Combustion, Cambridge University Press, Cambridge, UK.
15.
Gaydon, A. G., 1974, The Spectroscopy of Flames, Chapman and Hall, London.
16.
Crosley, D. R., and Dryer, M. J., 1982, “Two-Dimensional Imaging of Laser-Induced Fluorescence in OH in a Flame,” Proceedings of the International Conference on Lasers, Dec.
17.
Kosaka
,
H.
,
Nishigaki
,
T.
,
Kamimoto
,
T.
,
Sano
,
T.
,
Matsutani
,
A.
, and
Harada
,
S.
,
1996
, “
Simultaneous 2-D Imaging of OH Radicals and Soot in a Diesel Flame by Laser Sheet Techniques
,”
Trans. SAE
,
105, Sec. 3
, pp.
1184
–
1195
(SAE Technical Paper 960834).
18.
Becker
,
H. A.
, and
Liang
,
D.
,
1978
, “
Visible Length of Vertical Free Turbulent Diffusion Flames
,”
Combust. Flame
,
32
, pp.
115
–
137
.
19.
Kalghatgi
,
G. T.
,
1984
, “
Lift-Off Heights and Visible Flame Lengths of Vertical Turbulent Jet Diffusion Flames in Still Air
,”
Combust. Flame
,
41
, pp.
17
–
19
.
20.
Heskestad
,
G.
,
1999
, “
Turbulent Jet Diffusion Flames: Consolidation of Flame Height Data
,”
Combust. Flame
,
118
, pp.
51
–
60
.
21.
Delichatsios
,
M. A.
,
1993
, “
Transition From Momentum to Buoyancy-Controlled Turbulent Jet Diffusion Flames and Flame Height Relationships
,”
Combust. Flame
,
92
, pp.
349
–
364
.
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