Progress in open rotor propulsors: The FAA/GE/NASA open rotor test campaign

Abstract

Model scale tests of modern 'open rotor' propulsor concepts that have potential for significant fuel burn reduction for aircraft applications were completed at NASA Glenn Research Center. The recent test campaign was a collaboration between NASA, FAA, and General Electric (GE). GE was the primary industrial partner, but other organisations were involved such as Boeing and Airbus who provided additional hardware for fuselage simulations. The open rotor is a modern version of the UnDucted Fan (UDF ® ) that was flight tested in the late 1980s through a partnership between NASA and GE. The UDF ® was memorable for its scimitar shaped propeller blades and its unique noise signature. Design methods of the time were not able to optimise for both high aerodynamic efficiency and low noise simultaneously. Contemporary CFD/CAA based design methods can produce open rotor blade designs that maintain efficiency with acceptable acoustic signatures. Tests of two generations of new open rotor designs were conducted in the 9' × 15' Low Speed Wind Tunnel and the 8' × 6' Supersonic Wind Tunnel starting in late 2009 and completed in early 2012. Aerodynamic performance and acoustic data were obtained for take-off, approach and cruise conditions in isolated and semi-installed configurations. Additional detailed flow diagnostic measurements and acoustic

Effect of Aft Rotor on the Inter-Rotor Flow of an Open Rotor Propulsion System

“…Additionally, some CAA methodologies, such as discussed in Ref. [2], rely on isolated blade row calculations to provide the flow field perturbations. In that methodology, the forward rotor wake/tip vortex must be extracted from the CFD simulation at an axial location that is outside any significant influence of the aft rotor potential field.…”

“…The majority of the fuel efficiency benefit comes from the high propulsive efficiency of these systems, typically at or above 0.95 relative to adiabatic efficiency. The open rotor propulsion systems also typically carry fan pressure ratios less than 1.3 and usually under 1.1 which gives significant efficiency benefits not only at cruise but also at lower flight speeds [2].…”

“…A photo of the ORPR in the wind tunnel at GRC is shown in Figure 1. An overview of the ORPR wind tunnel test campaign and how it fits in the larger picture of progress on open rotor propulsion systems can be found in [2]. The flow field of the contra rotating open rotor (CROR) has been studied by numerous researchers in recent years.…”

Improved Separation of Tone and Broadband Noise Components from Open Rotor Acoustic Data

“…The one-fifth scale F31/A31 blade set serves as a non-proprietary baseline design for comparison with the advanced open rotor blade designs tested during a recent wind tunnel campaign [14]. Far-field sideline acoustic (unsteady pressure) measurements of this model at simulated approach and nominal takeoff conditions were performed in the NASA GRC 9' × 15' low-speed wind tunnel (LSWT) using a traversing microphone probe on a track parallel to and 1.524 m (5 ft) away from the model longitudinal axis.…”

Effect of Aft Rotor on the Inter-Rotor Flow of an Open Rotor Propulsion System

“…A photo of the ORPR in the wind tunnel at GRC is shown in Figure 1. An overview of the ORPR wind tunnel test campaign and how it fits in the larger picture of progress on open rotor propulsion systems can be found in [2].…”