Jet-Surface Interaction – High Aspect Ratio Nozzle Test ...
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Jet-Surface Interaction – High Aspect Ratio Nozzle Test Nozzle Design and Preliminary Data
Cliff Brown * Vance Dippold **
NASA Glenn Research Center
October 20, 2015
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Jet-Surface Interaction (JSI) Noise Sources and Effects
• Measured far-field noise includes: – Jet-surface interaction noise sources – Jet mixing noise (isolated) – Shielding/Reflecting effect
• Types of JSI noise sources – Surface loading (“scrubbing”) noise – Trailing edge (“scattering”) noise – Surface vibration noise
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StDj
1/12
Oct
ave
PSD
(dB
)
10-2 10-1 100 101
ShieldReflectIsolated
633273986859
5 dB
Shielding Effect
Jet / SurfaceInteraction Noise
Reflected Noise
JSI Source
Reflecting Effect
Shielding Effect
StDj
Jet Mixing Noise 1/
12 O
ctav
e PS
D (d
B)
Ground Observer
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Jet-Surface Interaction Noise Test Programs
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JSI1044 (2015)
JSI-HAR (2015)
(TBD) (TBD)
Multi-Stream
Asp
ect R
atio
JSIT (2011-2013)
ERN(2013) /JSIT(2013)
JSI1044 (2015)
JSI1044 (2015)
* Covered by AATT and CST Projects
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Jet-Surface Interaction Noise Test Programs
4
JSI1044 (2015)
JSI-HAR (2015)
(TBD) (TBD)
Multi-Stream
Asp
ect R
atio
JSIT (2011-2013)
ERN(2013) /JSIT(2013)
JSI1044 (2015)
JSI1044 (2015)
* Covered by AATT and CST Projects
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Turbo-electric Distributed Propulsion Concept
• 32:1 aspect ratio slot • Divided into 2:1 at exit • Electric fan has low pressure ratio, low temperature ratio
– Test conditions 1.2 ≤ NPR ≤ 1.86, TTR = 1
• Aft deck extends (estimated) 1-4 slot heights downstream
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Superconducting Turbogenerators
Asymmetric Flow Path
* Kim et. al., AIAA 2015-3805
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Nozzle Design for JSI-HAR Testing • Problem specific to model scale testing
– TeDP has other issues but each fan is round to approximately 2:1 aspect ratio • Limited by flow rate and scale factor to 16:1 aspect ratio • Must transition from round to rectangular
– Low noise - minimize internal flow separations and exit shocks – Uniform flow profile at exit – Minimize nozzle length and weight
• Allow parametric variations of septa/internal flow – Rapid prototyped plastic inserts (not load bearing)
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First Efforts Using SUPIN • SUPIN* is a parametric inlet design tool
– Assume “backward” inlet is a nozzle • Observations:
– Lines not always smooth near inflow. – Thick boundary layers and separation
along side walls as major axis spread. – Normal shock along centerline
• Greater control to parameterize nozzle designs required (SUPIN is not for nozzles!)
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Weak normal shock at exit
Vortex pair at exit plane
Thick BL
24.26 in
* AIAA Paper 2012-0016
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CFD for Design Evaluation
• Wind-US v4 used for all simulations presented here. – General purpose, compressible Reynolds-Averaged Navier-Stokes solver – SST turbulence model used – Steady flow simulations, i.e. constant CFL number
• Flow conditions: – Quiescent Freestream: p∞=14.3 psi; M∞=0.01 – NPR=1.861 → Mjet=0.98 (Ma=0.9) – Unheated Jet: T0=529.64°R (TTR=1)
• Grid: – 9 – 24.5 million cells
• Simulations performed on NAS: – 5 Ivy Bridge nodes (20 cores/node) – Converged solution < 60 hours
total wall time.
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Extruded grid along wall
Vane lines
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Next Approach: Parameterized Nozzle Design • Idea: Transition flow in segments rather than all
at once to gain greater control over design – Created new code to generate flow lines
• Example: Four segments 1. Transition from circular to order 10 superellipse; grow
major axis to nozzle exit width via cubic polynomial; maximum divergence angle<33°; constant area
2. Transition from order 10 superellipse to order 100 via exponential function; constant area
3. Contract area to nozzle exit area using cubic polynomial for minor axis
4. Constant area and shape to nozzle exit to accommodate septa inserts
• Include capability to add turning vanes – Minimize BL growth and flow separation by distributing
flow out to side walls as major axis grows. – Modeled vanes with inviscid boundary condition
(infinitely thin, slip surface) for ease of gridding and improved run time during design evaluation stage
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24.22 in
1 2 3 4
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Final Design: A16-10 • Three segments:
1. Transition from circular to order 10 superellipse; grow major axis to nozzle exit width via cubic polynomial; maximum divergence angle<33°; linear area contraction through segment 2 (80% of total)
2. Transition from order 10 superellipse to order 100 via exponential function; continues linear area contraction from segment 1 (80% or total); constant major axis length
3. Linear area contraction (20% of total) with constant major axis length and constant superellipse order; longer segment length (5.5 inches) to accommodate septa inserts
• No turning vanes – CFD showed turning vanes did not do much once
outer flow lines were refined – CFD showed significant wakes from turning vanes – Center vane retained for structural support
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24 inches
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A16-10: Design Evaluation
• Significant vorticity near corners • Attached flow along outboard edge of major
axis (BL thickness still significant) • No normal shocks at nozzle exit • Continuous area contraction helps • Significant wake from center vane (added
for structural support)
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Axial Velocity
Vorticity
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Septa Inserts
• Inserts are rapid prototyped using solid ABS plastic
• Inserts sit in small recess • Septa are airfoil shaped
– NACA0003, chord = 6” – R=1 mm leading edge fillet,
R=0.5 mm trailing edge fillet – 2 mm fillet at root and stem
• Half airfoil at center vane around sheet metal
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2:1 / 7 Septa
1:1 / 15 Septa
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Flow Profile at Nozzle Exit (1)
• 2:1 / 7 septa insert installed for JSI-HAR but not in WIND-US
• Total pressure measured 0.25” downstream of nozzle exit
• No indication of vortex in JSI-HAR data
– 1 Hz averaged pressure data would not likely pick this up even if present
• Flat profile between septa • Losses slightly higher in JSI-HAR
data
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P 0 (l
bf/in
2 )
Position (in)
Septa wake (no septa in CFD)
WIND-US JSI-HAR
Ma=0.9, Unheated
2:1 / 7 Septa
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Flow Profile at Nozzle Exit (2)
• 1:1 / 15 septa insert in both • Total pressure measured 0.25”
downstream of nozzle exit • More losses at nozzle edge in
JSI-HAR than predicted • Deeper wake deficits in
SolidWorks result – JSI-HAR probe may not be directly
behind septa
• Reasonable comparison for approximately 2 hours invested in SolidWorks simulation
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Z
p0[lb
f/in2
]
0 5 10 1512
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P 0 (l
bf/in
2 )
Position (in)
SolidWorks JSI-HAR
Ma=0.9, Unheated
* Thanks to Dennis Eck, AAPL Facility Engineer, for SolidWorks result
1:1 / 15 Septa
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Far-Field Noise – 1:1 / 15 Septa
• Spectra: 1-ft lossless at Θ=90º • No surface • Increased broadband noise on
minor axis • High frequency tonal content
– Strouhal shedding from septa
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Ma=0.7, Unheated
* Bridges, AIAA 2015-3119
1/12
Oct
ave
PSD
(dB)
Frequency (Hz)
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Far-Field Noise – 1:1 / 15 Septa
• Spectra: 1-ft lossless at Θ=90º • 8:1 smaller scale but similar
septa width* • Trends follow from 8:1 to 16:1
– Increased broadband noise on minor axis
– Stourhal shedding from septa gives high frequency tonal content
• Planning additional septa for 16:1 to separate aspect ratio from septa effects
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Ma=0.7, Unheated
* Bridges, AIAA 2015-3119
1/12
Oct
ave
PSD
(dB)
Frequency (Hz)
16:1
8:1
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Ma=0.7, Unheated
Far-Field Noise – 1:1 / 15 Septa with Surface
• Spectra: 1-ft lossless at Θ=90º • JSI noise source increasing with
longer surfaces – Follows previously observed trends
• Shielding only at the higher frequencies – Approximate scale factor 25:1
based on slot height (h) – JSI noise very low frequency at
full-scale (acoustic loading) – Shielding could benefit EPNL
when taken to full-scale 1/12
Oct
ave
PSD
(dB)
Frequency (Hz)
xE/h=0.8 xE/h=2 xE/h=4 Isolated
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Summary
• A round-to-rectangular convergent nozzle with aspect ratio 16:1 was designed for acoustic measurements – Minimized potential noise sources from: (1) internal flow separation and
(2) shock cells • 16:1 aspect ratio nozzle fabricated for testing
– Inserts to simulate TeDP concept details (septa) rapid prototyped • Pressure traverse at nozzle exit shows expected flow profile • Preliminary analysis of noise data consistent with previous experiments
– JSI noise source prominent at low frequencies – Shielding at only the highest frequencies
• Test on-going through October – Baseline (no septa), 2:1 / 7 Septa inserts planned
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