Rising fuel prices have led GE Aviation and NASA to revisit open-rotor engine systems. The two are coming together for a wind-tunnel test program to evaluate counterrotating fan-blade systems for open-rotor jet engine designs, which could sharply reduce fuel consumption.
In the 1980s, GE successfully ground-tested and flew an open-rotor jet engine that demonstrated fuel savings of more than 30% compared to similar-sized, jet engines with conventional, ducted front fan systems. Since then, GE has advanced its data acquisition systems and computational tools to better understand and improve open-rotor systems.
"GE and NASA journeyed down this path 25 years ago with great technical success," said David Joyce, President of GE Aviation. "Today's fuel crisis greatly influences future jet engine concepts. GE and NASA will evaluate open-rotor concepts in the wind tunnel with far greater technology capability."
For the tests, GE will run two rows of counterrotating fan blades at 1/5 subscale in several configurations, tested in simulated flight conditions created in Glenn Research Center's 9 x 15-ft low-speed and 8 x 6-ft high-speed wind tunnels. The testing is expected to begin in early 2009 and continue into midyear.
GE and the Fundamental Aeronautics Program of NASA's Aeronautics Research Mission Directorate in Washington, D.C., are jointly funding the program. Snecma of France, GE's 50:50 partner in CFM International, will participate with fan blade designs.
Open-rotor jet engine designs are among the longer term technologies being evaluated for LEAP-X, CFM International's technology program focusing on future advances for next-generation CFM56 engines.
NASA's testing rig equipment, which is being refurbished for the activities, was used in the 1980s when NASA and GE jointly tested scale-model, counterrotating fan systems that led to the development of the GE36 jet engine. The NASA test hardware is also capable of simulating aircraft installation systems with the open-rotor fan systems.
The GE36, which flew on Boeing 727 and MD-80 aircraft, featured an aft-mounted, open-rotor fan system with two rows of counterrotating composite fan blades. The efficiency from bypass air created by this fan system drove the GE36's dramatic fuel savings. As fuel prices fell in the late 1980s and early 1990s, the GE36 was never launched commercially; however, it was recognized worldwide as a technology breakthrough.
The upcoming rig tests will focus mostly on the acoustic characteristics of various fan configurations, as well as performance and efficiency characteristics. Engine noise is a challenge when operating open-rotor engine systems in a commercial aviation environment.
GE is designing and fabricating the scale-model blades at its Cincinnati facility using technical input provided by the GE Corporate Research Center in New York.