Wind-tunnel testing of multiple configurations of sub-scale blades for GE's Open Rotor engine is being conducted to identify the optimum blade design for the engine's two counterrotating stages of blades.

Minimal noise output and minimal specific fuel consumption (with the associated lower emissions output) are primary benefits derived from the optimum blade configuration.

Testing began in October 2009 at NASA's Glenn Research Center, in Cleveland, Ohio, employing the GE-NASA test rig used in testing the 1980s-era GE36 unducted fan (UDF) engine.

To determine that today's test data was consistent with the 1980s test data, initial testing was conducted on one-fifth-scale versions of F31/A31 blades identical to those on the GE36.

Subsequent acoustic testing-still ongoing-has involved more complex blade configurations that reflect the technological advances of the past 20 years in areas such as inter-blade spacing, blade sweep angle and chord length, and in other features derived through 3-dimensional aerodynamic (3-D aero) design.

Scheduled to begin later this year at the Glenn Research Center, performance testing of the blade designs at a wide range of engine speeds will enable the development of a comprehensive record of blade design data for current and future applications.