Volume 5, Number 1     January/February 1997

  Advanced Technologies

Better Jet Engine From Shuttle Tests

ESIGN IMPROVEMENTS FOR A NEW, MORE fuel-efficient Boeing 777 jet engine resulted from tests to improve NASA Space Shuttle engine performance.

The new design gained a full half-percent in energy efficiency—meaning a savings of hundreds of gallons of fuel per flight, an annual savings of millions of dollars for the airline industry and a competitive edge in world markets. Researchers also are using the test results to fine-tune the large, electricity-generating turbines used by U.S. electric companies to save fuel.

NASA and Pratt & Whitney, a commercial and military aircraft engine design and manufacturing leader, conducted the tests at Marshall Space Flight Center in 1992.

Engineers analyzing the test results noticed they showed the effects of small fluttering "wakes" of gases—the unsteadiness of gases flowing through the turbine airfoils—on turbine efficiency.

Engineers explored existence of an "optimum position" for turbine airfoils. This position could mean less energy to drive the turbines, resulting in lower engine temperatures, longer-lasting hardware, less maintenance time and lower operational costs.

MSFC and Pratt & Whitney engineers repeated the initial tests for the engine of a Boeing 777 to be put into commercial service in 1995.

"Wakes flowed the turbine airfoils, coming out high in some places, low in others. We knew if we could align the airfoil or wakes, we could also get the peaks and valleys to align-all for better turbine efficiency," said Stephen Gaddis, project engineer in MSFC's Structures and Dynamics Laboratory where the tests were conducted.

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 its PW-4084 engine for the Boeing 777.

	Space Shuttle technology helps Pratt & Whitney improve turbine rotor designs for PW-4084.

"We had been looking for ways to achieve efficiency improvement," said Frank W. Huber, manager of turbine aerodynamics for Pratt & Whitney's 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."

For more information about the product, contact Stephen Gaddis at MSFC.
Call 205/544-1612, FAX: 205/544-9358.
Please mention that you read about it in Innovation.