APPLYING NASA SHUTTLE ENGINE TEST FINDINGS MAY SAVE AIRLINES MILLIONS IN FUEL COSTS
Jim Cast, June Malone
Results from tests aimed at improving the performance of
NASAs Space Shuttle engines are expected to save airlines
millions of dollars in fuel costs each year.
The tests, performed at NASA’s Marshall Space Flight
Center in Huntsville, AL, have led to improvements in the
design of a new, more fuel-efficient jet engine for the
Boeing 777.
A full half-percent was gained in energy efficiency —
meaning a savings of hundreds of gallons of fuel per flight
and annual savings of millions of dollars for the airline
industry.
Tests performed at Marshalls turbine airflow test
facility in 1992 were a joint project by NASA and Pratt &
Whitney, a leader in commercial and military aircraft engine
design and manufacturing.
Analyzing the test results, engineers noticed that the
information showed the effects of small fluttering “wakes” of
gases — the unsteadiness of gases flowing through the
turbine airfoils — on turbine efficiency. A turbine is a
mechanical device used to provide power or thrust in rockets
or jet engines. The turbine is similar in concept to a
household fan: The fan rotates with blades on a shaft, just
as a turbine rotates on a shaft with layers of blades, called
airfoils.
Engineers explored the existence of an “optimum
position” for the turbine airfoils, which could mean less
energy to drive the turbines, resulting in lower engine
temperatures, longer-lasting hardware, less maintenance time
and lower operational costs.
Marshall and Pratt & Whitney engineers then repeated the
initial tests, this time for the engine of the wide-bodied
Boeing 777 aircraft, which was to be put into commercial
service in 1995.
Stephen Gaddis, project engineer in Marshall’s
Structures and Dynamics Laboratory where the tests were
conducted, explained, “Wakes flowed through the turbine
airfoils, coming out high in some places, low in others. We
knew if we could align the airfoils or wakes, we could also
get the peaks and valleys to align — all for better turbine
efficiency.”
The principle is much like one used by competitors in
bicycle races: A cyclist will move in behind another racer
to benefit from “drafting” created by the front cyclist. The
biker in front serves to break the winds’ force, so the
cyclist in the rear does not have to pedal as hard as the
leader. Pratt & Whitney took these findings and modified
their PW-4084 engine for the Boeing 777.
“We had been looking for ways to achieve efficiency
improvement,” said Frank W. Huber, manager of turbine
aerodynamics for Pratt & Whitneys Government Engine Division
in West Palm Beach, FL. “The clocking concept — the
aligning of the airfoils — was not new, but there were not
sufficient data to validate this technique.”
“The tests at Marshall demonstrated that the concept
worked — clearly showing the benefit of aligning the turbine
airfoils,” said Huber. “We ultimately found that we could
achieve significant improvement in engine performance.”
Technology developed by NASA has given Pratt & Whitney
and the Boeing Company a competitive edge in world markets,
with an aircraft engine that can realize substantial fuel
savings.
Today, both government and private industry researchers
are using the Marshall test results to fine-tune the large,
electricity-generating turbines used by America’s electric
companies, in an effort to save fuel.
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