During the last decade, countercurrent shear has been established as an effective flow control technique for increasing turbulent mixing in a variety of flow configurations and operating regimes. Based on the robust mixing enhancement observed for jets and shear layers, the technique appears to have many potential benefits for enhancement and control for turbulent combustion flows. Countercurrent shear flow control has been applied to a planar asymmetric rearward-facing step dump combustor. A nonreacting flow study on the implementation of suction-based countercurrent shear at the dump plane provided insight into the flow control mechanisms. Control of turbulence velocity and length scales occurs through two mechanisms, the development of a countercurrent shear layer near the dump plane, and enhanced global recirculation caused by the removal of mass at the dump plane. Parametric studies on the geometry of the suction slot indicate that the enhancement of the global recirculation zone is the primary mechanism for increasing global turbulence levels within the combustor. Turbulence energy and length scales both increase in a manner such that the spatially-filtered strain rates as measured with particle image velocimetry remain nominally constant, a desirable characteristic for premixed turbulent combustion. Connections will be made to a recent study on fully-developed turbulent countercurrent shear layers showing additional attractive features of countercurrent shear including enhanced turbulent energy production, entrainment, and three dimensionality. Preliminary reacting flow results for the dump combustor operating while burning premixed/prevaporized JP-10 illustrate qualitative changes in the turbulent combustion process within the combustor. The companion paper will describe the quantitative effects of countercurrent shear on the global heat release rates within the combustor.

Volume Subject Area:
Heat Transfer
Keywords:
turbulent combustion, countercurrent shear, rearward-facing step flow, flow control
Topics:
Combustion, Combustion chambers, Flow (Dynamics), Flow control, Shear (Mechanics), Turbulence
1.
Behrens, A.A., Anderson, M.J., Strykowski, P.J., and Forliti, D.J. “Combustion Enhancement in a Dump Combustor using Countercurrent Shear. Part 2: Heat Release Enhancement and Optimization,” ASME International Mechanical Engineering Congress and Exposition. 2005. Orlando, FL.
2.
Strykowski
P. J.
,
Krothapalli
A.
, and
Jendoubi
S.
, “
Effect of counterflow on the development of compressible shear layers
,”
Journal of Fluid Mechanics
,
1996
,
308
, p.
63
–
96
.
3.
Strykowski
P. J.
and
Wilcoxon
R. K.
, “
Mixing enhancement due to global oscillations in jets with annular counterflow
,”
AIAA Journal
,
1993
,
31
(
3
), p.
564
–
570
.
4.
Strykowski
P. J.
and
Niccum
D. L.
, “
Stability of countercurrent mixing layers in circular jets
,”
Journal of Fluid Mechanics
,
1991
,
227
, p.
309
–
343
.
5.
Strykowski
P. J.
and
Niccum
D. L.
, “
The Influence of Velocity and Density Ratio on the Dynamics of Spatially Developing Mixing Layers
,”
Physics of Fluids A: Fluid Dynamics
,
1992
,
4
(
4
), pp.
770
–
781
.
6.
Huerre
P.
and
Monkewitz
P. A.
, “
Absolute and Convective Instabilities in Free Shear Layers
,”
Journal of Fluid Mechanics
,
1985
,
159
, p.
151
–
168
.
7.
Monkewitz
P. A.
and
Huerre
P.
, “
Influence of the Velocity Ratio on the Spatial Instability of Mixing Layers
,”
Physics of Fluids
,
1982
,
25
(
7
), p.
1137
–
1143
.
8.
Forliti, D.J., Tang, B.A., and Strykowski, P.J., “An experimental investigation of planar countercurrent turbulent shear layers,” Journal of Fluid Mechanics, 2005, 530.
9.
Liepmann, H.W. and Laufer, J., “Investigations of free turbulent mixing,” NACA TN-1257, 1947.
10.
Eaton
J. K.
and
Johnston
J. P.
, “
A Review of Research on Subsonic Turbulent-Flow Reattachment
,”
AIAA Journal
,
1981
,
19
(
9
), p.
1093
–
1100
.
11.
Pitz
R. W.
and
Daily
J. W.
, “
Combustion in a Turbulent Mixing Layer Formed at a Rearward-Facing Step
,”
AIAA Journal
,
1983
,
21
(
11
), p.
1565
–
1570
.
12.
Hammond
D. A.
and
Redekopp
L. G.
, “
Local and global instability properties of separation bubbles
,”
European Journal of Mechanics B-Fluids
,
1998
,
17
(
2
), p.
145
–
164
.
13.
Humphrey
J. A. C.
and
Li
S.
, “
Tilting, Stretching, Pairing and Collapse of Vortex Structures in Confined Countercurrent-Flow
,”
Journal of Fluids Engineering-Transactions of the ASME
,
1981
,
103
(
3
), p.
466
–
470
.
14.
Strykowski, P.J. and Forliti, D.J. “Flow control applications using countercurrent shear,” International Symposium on Recent Advances in Experimental Fluid Mechanics. 2000. Kanpur, India.
15.
Forliti
D. J.
and
Strykowski
P. J.
, “
Controlling turbulence in a rearward-facing step combustor using countercurrent shear
,”
Journal of Fluids Engineering-Transactions of the ASME
,
2005
,
127
(
3
), p.
438
–
448
.
16.
Forliti, D.J., “Controlling dump combustor flows using countercurrent shear,” Ph.D. Thesis, 2001, University of Minnesota: Minneapolis, MN.
17.
Adams
E. W.
and
Johnston
J. P.
, “
Effects of the Separating Shear-Layer on the Reattachment Flow Structure. 2. Reattachment Length and Wall Shear-Stress
,”
Experiments in Fluids
,
1988
,
6
(
7
), p.
493
–
499
.
18.
Browand
F. K.
and
Latigo
B. O.
, “
Growth of the 2-Dimensional Mixing Layer from a Turbulent and Non-Turbulent Boundary-Layer
,”
Physics of Fluids
,
1979
,
22
(
6
), p.
1011
–
1020
.
19.
Peters
N.
, “
The turbulent burning velocity for largescale and small-scale turbulence
,”
Journal of Fluid Mechanics
,
1999
,
384
, p.
107
–
132
.
20.
Abdel-gayed
R. G.
,
Bradley
D.
, and
Lawes
M.
, “
Turbulent Burning Velocities - a General Correlation in Terms of Straining Rates
,”
Proceedings of the Royal Society of London Series a-Mathematical Physical and Engineering Sciences
,
1987
,
414
(
1847
), p.
389
–
413
.
21.
Poinsot
T.
,
Veynante
D.
, and
Candel
S.
, “
Quenching Processes and Premixed Turbulent Combustion Diagrams
,”
Journal of Fluid Mechanics
,
1991
,
228
, p.
561
–
606
.
22.
Schadow
K. C.
and
Gutmark
E.
, “
Combustion instability related to vortex shedding in dump combustors and their passive control
,”
Progress in Energy & Combustion Science
,
1992
,
18
(
2
), p.
117
–
132
.
23.
Schadow
K. C.
,
Gutmark
E.
,
Parr
T. P.
,
Parr
D. M.
,
Wilson
K. J.
, and
Crump
J. E.
, “
Large-Scale Coherent Structures as Drivers of Combustion Instability
,”
Combustion Science and Technology
,
1989
,
64
(
4–6
), p.
167
–
186
.
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