MITEYC01202000-1

Manipulating Pattern Factor Using Synthetic Jet Actuators

Y. Chen D. Scarborough and J. Jagoda

School of Aerospace EngineeringGeorgia Institute of Technology

Atlanta, GA 30332-0150

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Outline

• Experiment Setup • Quick Review of Data Analysis• Current Results• Conclusions • Future Work

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3"

Experimental Facility

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orifice plate20mm D 5 mm

bottom chamber wall

2.38mm D4 holes, 4mm apart

flow

Z

X

slot 1.6 mm x11.2 mm

Synthetic Jets: Configurations Tested

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Configuration of Bleed Ring

unit: inch

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Diagnostics

• Temperature Distribution Measured by Thermocouple Rake

• Velocities Measured by Pitot Probe and Hot Film Anemometer

• Flow Field Visualized Using High Speed Shadowgraph

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Synthetic Jet Velocity

0.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

0 0.2 0.4 0.6 0.8 1

t (s)

jet v

eloc

ity (m

/s)

4-hole geometry, 2mm above orifice, hot film data

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Actuator Calibration0 open: y = 1.1157x + 1.56721 open: y = 0.9437x + 1.27282 open: y = 0.8191x + 1.25473 open: y = 0.7081x + 1.28794 open: y = 0.6399x + 1.14235 open: y = 0.5642x + 1.1122

8 open: y = 0.4614x + 1.06667 open: y = 0.4909x + 1.21396 open: y = 0.5122x + 1.1764

0

5

10

15

20

25

30

35

40

0 5 10 15 20 25 30 35freqency (Hz)

peak

jets

vel

ocity

(m/s

)

0 open

1 open

2 open

3 open

4 open

5 open

6 open

7 open

8 open

Linear(0open)Linear(1open)Linear(2open)Linear(3open)Linear(4open)Linear(5open)Linear(8open)Linear(7open)Linear(6open)

4-hole geometry

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=0, no actuation

Uj, av / Uc

=1.2

=3.6

Example Results

• Pitot (avg. velocity) measurements 3mm above orifice plate

• Weak orientation effect at high velocity ratio

slot (crosswise) slot (streamwise)

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Quantifying Degree of Unmixedness

• Many possible methods (max.-min, rms, …)• Entropy approach:

– as the temperature profile becomes more uniform the entropy increases

TdTcds p

– reference every state to an “ideal” fully mixed state reached by complete adiabatic mixing and identified with a uniform temperature

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0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

0 1 2 3 4 5 6Uj/Uc

norm

aliz

ed e

ntro

py

slot(streamwise)

slot(crosswise)

Mixing Enhancement: Velocity and Orientation Dependence

0

0

sss

Avg Velocity Ratio Uj, av / Uc

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Effect of Synthetic Jet Frequency

Peak velocity ratioUj,p/Uc

4-hole cross geometry0

102030405060708090

100

0 50 100 150

actuator frequency (Hz)

frac

tiona

l im

prov

emen

t in

mix

ing

(%)

1.852.554.75repeat-4.757.1711.1

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0

10

20

30

40

50

60

70

80

90

100

0 2 4 6 8 10 12

peak velocity ratio (Uj,p/Uc)

frac

tiona

l im

prov

emen

t in

mix

ing

(%)

Effect of Synthetic Jet Strength

4-hole cross geometry

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Estimate Energy Applied to the Main Flowsynthetic jets main flow notes

velocity (m/s) 26.5 (peak) 2.65 (cold) Up,j /Uc =10

kinetic energy(w)

1/2airUp,j2Aorifice

=7.5210-31/2mcUc

=4.8610-310-3

energyreleased fromcombustion(w)

mmethane(heat

release perunit mass)=1.33103

103

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Flow Visualization - Shadowgraphy

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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)

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Future Work

Compare Momentum/Velocity Effect and Momentum Flux Effect

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

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Flow Visualization

• Cold Stateacetone and fluorescence

• Combustion StateRayleigh scattering