Co
mpu
tational Sciences
C
enter of Excellenc
e
URANS CFD Simulations of Scramjet Flow Path Transients
CCAS Review – May 2015
Logan Riley and Datta V. Gaitonde
AFRL Contacts: Dr. Jeff Donbar and Dr. Mark Hagenmaier
Co
mpu
tational Sciences
C
enter of Excellenc
e
Bio • Education
– B.S. Mechanical Engineering from U. Akron [Spring 2012] – Aerospace PhD Program [Fall 2013-Fall 2017 (expected)]
• DAGSI Fellowship [Fall 2014-Present] – AFRL sponsor: Dr. Jeff Donbar – AFRL intership: Summer 2015
• Research interests: – Hypersonic air-breathing propulsion – Roughness-induced transition
2015.05.19 2
Co
mpu
tational Sciences
C
enter of Excellenc
e
Background: Mode Transition • Unsteady RANS (URANS) used to explore mode transition in the
HIFiRE-2 scramjet (Yentsch et al. 2013, 2015)
3
Image reproduced from Jackson et al., 2011 http://www.nasa.gov/topics/aeronautics/ features/hifire.html
Co
mpu
tational Sciences
C
enter of Excellenc
e
Background • Unsteady RANS (URANS) used to explore mode transition in the
HIFiRE-2 scramjet (Yentsch et al. 2013, 2015)
4
Image reproduced from Jackson et al., 2011 http://www.nasa.gov/topics/aeronautics/ features/hifire.html
Mode-Transition
Wikipedia
Reproduced from Yentsch 2013
Co
mpu
tational Sciences
C
enter of Excellenc
e
Background • Unsteady RANS (URANS) simulations used to explore mode
transition in the HC-fueled HIFiRE-2 scramjet flowpath (Yentsch et al. 2013, 2015)
2014.05.21 5
Image reproduced from Jackson et al., 2011 http://www.nasa.gov/topics/aeronautics/ features/hifire.html
HDCR mode-transition characterized by loss of flame-holding in inboard primary-injectors (PI)
Dual-Mode Scramjet-Mode
Reproduced from Yentsch 2013
Flight mode-transition preserves flame-holding in inboard PI because of inlet distortion
Ground Test Flowpath (HDCR), Primary Injectors
Co
mpu
tational Sciences
C
enter of Excellenc
e
Objectives • Extend (URANS) capabilities to understand evolution of unstart
events in a hydrocarbon-fueled, dual-mode scramjet • Want to capture large scale transients
– Identify precursors to unstart – Quantify SBLI sensitivity to variations in fuel input (variable fuel flow rates)
6
Can unstart be anticipated by measuring away from the wall?
Can quantities other than pressure be used to predict unstart?
Co
mpu
tational Sciences
C
enter of Excellenc
e
AFRL Flowpath • CFD work based on experiments of Donbar et al. 2010 • Ethylene-fueled combustor • 1kHz wall pressure measurements • Different fuel-staging conditions
7
Reproduced from Donbar et al. 2010
Isolator Pressure Measurements
Experimental Flowpath
Data-rich experiments selected to ground simulations
Co
mpu
tational Sciences
C
enter of Excellenc
e
AFRL Flowpath • CFD work based on experiments of Donbar et al. 2010 • 1kHz wall pressure measurements • Ethylene-fueled combustor • Different fuel-staging conditions
2014.05.21 8
Reproduced from Donbar et al. 2010
Experimental Flowpath: Injector Detail
Hybrid mesh necessary to resolve detailed flowpath geometry
Co
mpu
tational Sciences
C
enter of Excellenc
e
Operating Conditions Constant mass flow rate
• Two operating points – Fixed equivalence ratio – For validation of numerical
approach
Variable mass flow rate
• Ramp from baseline to unstart fueling conditions to study unstart process
9
Injector Set Baseline Unstart
B2 (body-side) 0.20 0.40
B6 (body-side) 0.33 0.24
C3 (cowl-side) 0.37 0.26
Fuel-staging selected to highlight primary phenomena within parameter space
Equivalence Ratio
Co
mpu
tational Sciences
C
enter of Excellenc
eNumerical Approach
10
Metacomp, Inc.’s CFD++ • Unified grid architecture • Coupled multi-physics • Min-mod TVD limiter • HLLC Riemann Solver
Turbulence Closure • Cubic k-epsilon
Chemistry • Finite-rate kinetics • Taitech-Princeton (TP2)
Ethylene mechanism Mesh Development • Hybrid structured/unstructured • Half symmetry • O(5M) Cells
Models successfully employed in previous mode-transition studies
Co
mpu
tational Sciences
C
enter of Excellenc
e
Validation • Mean isolator pressure distributions used to validate numerical
approach – Fueled (tare) – Unfueled
• Calibrate modeling parameters – Grid convergence study, O(2-7)M cells – Turbulent Schmidt number calibration (fueled conditions), 𝑆𝑐↓𝑡 ∈0.5−0.9 – Wall heat-transfer:
› Adiabatic › 1-D resistance model
11
Co
mpu
tational Sciences
C
enter of Excellenc
e
Tare mode operation, cowl-side pressure distribution
Validation: Tare Operation
12
Mesh resolution sufficient to resolve shock train
Co
mpu
tational Sciences
C
enter of Excellenc
e
Fueled operation: Isosurface of M=1 colored by height, with fuel injection streamlines
Validation: Fueled Operation (Baseline) • Isolator pressure
distribution: – Over-predicted in initial
simulations › Sensitive to 𝑆𝑐↓𝑡 › Wall treatment
• Bias of supersonic fluid: – Result of inlet
distortion/side wall flow-separation
– Similar to work of: › Gaitonde, et al. 2003 › Yentsch et al. 2013
13
H is the height at the start of the isolator
Examining 3-D flowfield helps identify discrepancies between fueled validation simulation and experiment
Co
mpu
tational Sciences
C
enter of Excellenc
e
H is the height at the start of the isolator
𝐼𝑠𝑜𝑠𝑢𝑟𝑓𝑎𝑐𝑒 𝑜𝑓 𝑀=1 𝑐𝑜𝑛𝑑𝑖𝑡𝑖𝑜𝑛 𝑐𝑜𝑙𝑜𝑟𝑒𝑑 𝑏𝑦 ℎ𝑒𝑖𝑔ℎ𝑡, 𝑤𝑖𝑡ℎ 𝑠𝑢𝑟𝑓𝑎𝑐𝑒 𝑜𝑖𝑙 𝑓𝑙𝑜𝑤𝑠
Preliminary Transient Results
14
𝐽↓𝑚 : mass flux 𝐽↓𝑚,𝑚𝑎𝑥 : baseline
Initial results indicate sensitivity of unstart to boundary layer thickness
Co
mpu
tational Sciences
C
enter of Excellenc
e
Looking Ahead • Explore upstream effect of combustor in dual-mode operation • Connect measured pressure variations to flow structures • Understand influence of inlet distortion on different flow paths (e.g. HIFiRE 2) • Leverage analysis tools (e.g. POD, DMD) to identify fluid structures of interest • Explore application of hybrid LES/RANS methods
15
Co
mpu
tational Sciences
C
enter of Excellenc
e
Q&A
16
Co
mpu
tational Sciences
C
enter of Excellenc
e
HIFiRE-2 Experiments Ground (HDCR) Configuration Flight Configuration
17
Reproduced from Jackson et al., 2008 Reproduced from Gruber et al., 2008
Difference in inlet geometry significantly affects flow field
Co
mpu
tational Sciences
C
enter of Excellenc
e
HIFiRE-2 Experiments Ground (HDCR) Configuration Flight Configuration
2014.05.21 18
Reproduced from Jackson et al., 2008 Reproduced from Gruber et al., 2008
Primary (x8)
Secondary (x8)
Outboard
Inboard
Outboard
144 static pressure ports 19 surface thermocouples
4 heat flux gauges
Ground test pressure data used for validation
Co
mpu
tational Sciences
C
enter of Excellenc
e
Inlet Distortion Effects (HIFiRE 2)
19
Low energy region near centerline preserves inboard PI flame-holding in flight
Reproduced from Yentsch et al. 2013
Co
mpu
tational Sciences
C
enter of Excellenc
e
Inlet Distortion Effects (Double Fin)
20
Reproduced from Gaitonde et al., 2003
Co
mpu
tational Sciences
C
enter of Excellenc
e
Fueled operation: Isosurface of M=1 colored by height, with fuel injection streamlines
Combustion Operation (Baseline) • Isolator pressure distribution:
– Sensitive to grid refinement near injectors
– Sensitive to 𝑆𝑐↓𝑡 • Bias of supersonic fluid
– Result of inlet distortion/side wall flow separation
– Similar to work of: › Gaitonde, et al. 2003 › Yentsch et al. 2013
– Influence on fuel penetration
21
Co
mpu
tational Sciences
C
enter of Excellenc
e
Combustion Operation (Baseline)
22
M>1 Flow suppresses injector penetration
Top Related