I
by the year 2000 the FAA will likely
require further reductions in aircraft
noise more than a decade of research and
development by the Aeronautics industry
has focused on compliance after two
years of wind tunnel tests a model
designed to meet that proposed FAA
standard it's crated and shipped for
further testing designed by pratt &
whitney a division of united
technologies the model was tested in two
of the six wind tunnels at NASA Lewis
Research Center in Cleveland Ohio the
joint effort between NASA and this
leading manufacturer of aircraft engines
explored the acoustics aerodynamic
performance and the operability of the
advanced ducted propeller known as the
ADP initial indications are that from
this new design a quieter better
performing engine will emerge
the model scaled to one-sixth of the
actual design was tested here in this
tunnel commonly called the 9 by 15 which
are the dimensions of the wind chamber
itself
this tunnel is nested in the return leg
of the eight by six tunnel while the
eight by six has supersonic capabilities
only the subsonic speeds were used to
test the ADP for the arrow propulsion
facilities and experiments division this
project began over three years ago at
that time Lewis engineers started
working closely with Pratt & Whitney to
define the test parameters for the model
this preparation ensured that the wind
tunnels and the model were ready for
each other the tunnel control room is
the hub of adp research state-of-the-art
equipment allows researchers to collect
valuable data and monitor testing at the
close of this last day an engineer
reviews one of the nine test phases
green light successful testing of any
model requires the skills and talents of
a number of people test day brings
together those abilities in preparation
for each experiment
two green lights
blowing air
and so begins the test the tunnel
operators control tunnel systems to
obtain desired air speeds the ADP was
tested over a Mach number range from
zero 2.85 the model operator controls
rpms by regulating the compressed air to
the models drive turbo rpms for the ADP
ranged from windmill to 12300 during
testing the models safety is ensured by
continuous monitoring of vibration and
temperatures the engineer who monitors
stress ensures that the predetermined
stress limits on blades stator veins and
instrumentation are not exceeded the
primary researcher has lead
responsibility for all aspects of ADP
testing ongoing communications about the
tunnel and model aid the Lewis
researcher in making decisions about
each test condition the primary
researcher is supported by a counterpart
who helps monitor online test data all
these people depend on the electronics
engineer who has complete responsibility
for the electronics in the model the
hardware the instrumentation and the
computer system the ADP is a gear-driven
fan with variable pitch much like a
turboprop however a duct encircles the
fan to suppress noise generated by the
airfoil
researchers discuss a primary focus of
this ADP testing acoustics
various Inlet and spinner configurations
were tested in the eighth by six to help
determine aircraft noise affecting
communities cabin noise affecting
passengers is also a consideration
twelve microphones for these tests were
mounted on a one-inch thick aluminum
plate and suspended above the model they
are calibrated daily to ensure accuracy
Pratt & Whitney is kept informed during
each phase of testing pratt & whitney's
interest is supervised by company vice
president william webb the testing here
at lewis is possible because of the wind
tunnel facilities here at lewis are
capable of doing both performance
testing and noise testing with one set
up not many tunnels in the United States
are capable of doing that lewis is
developed what we call a rotating
microphone that lets us measure noise
and separate the things within the
engine that create those noise such that
if we have one component that's creating
an offensive signal we can then work on
that one component and not have to waste
our time struggling through all of the
engine that same focused approach
characterized all of the acoustic
testing which included blade angles
inlets and spinners stator veins and
angles of attack the other primary focus
of a DP testing was aerodynamic
performance
during the past two years testing
focused on four inlet spinner
configurations and numerous blade angle
settings mechanics were called on to
make changes for each configuration
hundreds of performance tests including
investigation of thrust and drag
resulted in thousands of test points a
sheet laser flow test provides an image
of reverse thrust necessary during
landing the laser doppler velocimeter or
LDV is a non intrusive measurement of
velocity with light beams it was used to
map the reverse thrust velocity profile
to determine the operability of the ADP
the model was tested at various angles
of attack simulating takeoff and landing
configurations
when modifications were necessary for a
specific investigation model changes
instrumentation and repairs were
performed on site by Lewis experts
minimizing any delays in the test
program NASA researchers are responsible
for accurate gathering of the real time
data on the escort d+ computer system
the laborious process of analyzing and
interpreting the information will
continue for several months researchers
map a trend within the test data and
determine engine noise and performance
this helps to validate analytical codes
ultimately leading to improved
technology and design codes for future
industry use our technology readiness
development program is scheduled to run
through 1995 we anticipate that it we
could be ready to start the development
of a commercial product in the 1994 to
1995 time period if the market is there
that would support the cost of
developing a new product that would let
us put an engine in service that is
carrying revenue-generating passengers
around the year 2000 NASA louis's
leading role in long-range aeronautics
research consistently places the center
at the forefront of technology
development
as flying on the ground for the model
ends the future for advanced ducted
propulsion begins
you