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Diagnostics for Hypersonic Engine Isolator Study
Complex Fluid Dynamics
•Presently, no comprehensive
under-standing of the details of
the fluid behavior in isolators of
hypersonic engines (in particular,
transient behavior).
•Transient CFD approaches not
yet mature enough for predictive
capability.
•DNS currently limited to Reynolds
numbers well-below those of
isolator operation.
Need for Measurements
•Measurements of thermodynamic
variables during isolator transients
needed for:
input to (CFD) modeling
efforts
input to reduced order control
models
•Currently only a few data sets of
transient phenomena in
hypersonic isolators with fueled
combustors exist.
Tandem Measurement Strategy
•Simultaneously implement optical
diagnostics for in-stream
measurements and “surfacemounted” diagnostics.
MAIN ACHIEVEMENTS:
•Optical measurements have been executed in the
boundary layer of supersonic flows upstream of: a
laser spark, a pulse combustion device and a
scramjet
combustor
transient.
(Belowshadowgraph of pulse detonation event and
corresponding transient optical signal (graph))
M 2 flow
Planned Approach
Perform simultaneous optical and nonoptical diagnostic measurements in
isolators of varying design under varying
flow conditions; in particular, transient
conditions (along with their corresponding
tare conditions).
Perform
measurements
at
data
acquisition rates of 1 kHz and higher.
Analyze acquired data to search for
variables or correlations thereof that
indicate
impending
fluid
behavior
changes
such
as
shock-induced
boundary-layer separation
Research Goals
END-OF-PHASE GOAL
CURRENT APPROACH
Implementation of Diagnostics in Isolators of Fueled Engines
MEASUREMENT STRATEGY
STATUS QUO
Michael S. Brown / Jeffrey M. Donbar (FA8650-08-D)
AFRL/Aerospace Propulsion Division
Identification of measureable variable(s)
whose time-dependent behavior predicts
the onset of gross changes in isolator
fluid dynamic behavior
Collection of data sets of transient
isolator phenomena suitable for CFD
study
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Highlight Slide Template
Boundary Layer Dynamics Reveal Downstream
Behavior
Your
Pic
Shock associated with cavity flameholder disturbs upstream boundary
layer
Diode laser beams
M 2 flow
expansion fan
isolator
M 2 flow
combustor
oblique shock
shear layer
Density fluctuations in
boundary layer are sensitive
to the downstream behavior
of supersonic flow
Unlit combustor exhibits
simple expansion fan at step
Dr. Michael
Brown
Lit combustor leads to shear
layer and shock wave that
JANNAF
influences the upstream
Combustion
boundary layer
Laser beam in boundary
layer gets “steered” by
fluctuations
isolator
Impacts scramjet engine
control
Subcommittee for
Diagnostics
(organizer)
• Associate Fellow,
AIAA
2
Transmitted Light Amplitude
Keep this space blank, too, same deal as last slide
combustion
no combustion
Time(s)
Boundary layer dynamics lead
to diffraction of laser beams
causing amplitude fluctuations
of transmitted light
These dynamics change ahead
of full combustion as evidenced by
the frequency-weighted power
spectrum of the transition period
(middle spectrum below)
Brown & Donbar, AFRL
3