Manipulating Pattern Factor
Using Synthetic Jet Actuators
Y. Chen
D. Scarborough and J. Jagoda
School of Aerospace Engineering
Georgia Institute of Technology
Atlanta, GA 30332-0150
YC01202000-1
MITE
Outline
•
•
•
•
•
Experiment Setup
Quick Review of Data Analysis
Current Results
Conclusions
Future Work
YC01202000-2
MITE
Experimental Facility
3"
YC01202000-3
MITE
Synthetic Jets: Configurations Tested
slot 1.6 mm x11.2 mm
2.38mm D
4 holes, 4mm apart
orifice plate
20mm D  5 mm
flow
Z
X
bottom chamber wall
YC01202000-4
MITE
Configuration of Bleed Ring
unit: inch
YC01202000-5
MITE
Diagnostics
• Temperature Distribution Measured by
Thermocouple Rake
• Velocities Measured by Pitot Probe and Hot
Film Anemometer
• Flow Field Visualized Using High Speed
Shadowgraph
YC01202000-6
MITE
Synthetic Jet Velocity
14.00
jet velocity (m/s)
12.00
10.00
8.00
6.00
4.00
2.00
0.00
0
0.2
0.4
0.6
0.8
1
t (s)
4-hole geometry, 2mm above orifice, hot film data
YC01202000-7
MITE
Actuator Calibration
40
peak jets velocity (m/s)
35
0 open: y = 1.1157x + 1.5672
0 open
1 open: y = 0.9437x + 1.2728
2 open: y = 0.8191x + 1.2547
1 open
3 open: y = 0.7081x + 1.2879
30
4 open: y = 0.6399x + 1.1423
5 open: y = 0.5642x + 1.1122
6 open: y = 0.5122x + 1.1764
25
2 open
3 open
7 open: y = 0.4909x + 1.2139
4 open
8 open: y = 0.4614x + 1.0666
20
5 open
15
6 open
10
7 open
8 open
5
0
0
5
10
15
20
freqency (Hz)
25
30
35
Linear
(0
open)
Linear
(1
open)
Linear
(2
open)
Linear
(3
open)
Linear
(4
open)
4-hole geometry
YC01202000-8
MITE
Example Results
Uj, av / Uc
=0, no actuation
• Pitot (avg. velocity)
measurements
3mm above orifice
plate
=1.2
• Weak orientation
effect at high
velocity ratio
=3.6
slot (crosswise)
YC01202000-9
slot (streamwise)
MITE
Quantifying Degree of Unmixedness
• Many possible methods (max.-min, rms, …)
• Entropy approach:
– as the temperature profile becomes more uniform the
entropy increases
dT
ds  c p
T
– reference every state to an “ideal” fully mixed state
reached by complete adiabatic mixing and identified
with a uniform temperature
YC01202000-10
MITE
Mixing Enhancement:
Velocity and Orientation Dependence
1.0
0.9

normalized entropy
0.8
0.7
0.6
0.5
0.4

0.3
0.2
slot
(streamwise)
s0  s
s0
slot
(crosswise)
0.1
0.0
0
1
2
3
4
5
6
Avg VelocityUj/Uc
Ratio Uj, av / Uc
YC01202000-11
MITE
fractional improvement in mixing
(%)
Effect of Synthetic Jet Frequency
100
Peak velocity ratio
Uj,p/Uc
90
80
1.85
2.55
4.75
repeat-4.75
7.17
11.1
70
60
50
40
30
20
10
4-hole cross geometry
0
0
50
100
150
actuator frequency (Hz)
YC01202000-12
MITE
fractional improvement in mixing (%)
Effect of Synthetic Jet Strength
100
4-hole cross geometry
90
80
70
60
50
40
30
20
10
0
0
2
4
6
8
10
12
peak velocity ratio (Uj,p/Uc)
YC01202000-13
MITE
Estimate Energy Applied to the Main Flow
synthetic jets
velocity (m/s) 26.5 (peak)
main flow
notes
2.65 (cold)
Up,j /Uc =10
kinetic energy 1/2airUp,j2Aorifice 1/2mcUc
(w)
=4.8610-3
=7.5210-3
energy
released from
combustion
(w)
YC01202000-14
10-3
mmethane(heat 103
release per
unit mass)
=1.33103
MITE
Flow Visualization - Shadowgraphy
YC01202000-15
MITE
Conclusions
 Significant improvement in removing temperature extremes
even for low actuator velocities
 Significant increase in mixing effectiveness with increasing
jet strength
 Above Uj,p/Uc=7 effect levels off
 Small effect due to orifice plate geometry (slots/holes) and
orientation
 Minimal dependence on actuator frequency (at least for low
frequencies)
YC01202000-16
MITE
Future Work
 Compare
Momentum/Velocity
Momentum Flux Effect
Effect
and
 Extend Study of the Effects of Actuator
Configurations and Orientations on Mixing
 Continue Mixing Mechanism Study through
 Enhanced Flow Visualization
 Local Mixing Measurement
 Local Velocity Measurement
YC01202000-17
MITE
Flow Visualization
• Cold State
acetone and fluorescence
• Combustion State
Rayleigh scattering
YC01202000-18
MITE