An Integrated Assessment of an Advanced Open Rotor Configuration Using the Environmental Design Space

Abstract

Government and industry have been renewing the investigation of an open rotor concept to reduce the future environmental impact of aviation. The open rotor was extensively developed in previous decades including more than one successful flight test demonstration. The concept never evolved into a mature commercial application due to a sudden drop in fuel prices in the late 1980s and because of the relatively high noise levels of the open rotor. More recent increases in fuel prices and increased government pressure in the form of carbon-dioxide taxes have made the open rotor a concept of interest once again. There has been a wealth of recent information and data generated on both the historical open rotor testing and updated design configurations. Recent advances in computational fluid dynamics and aeroacoustics have allowed designers to lower the noise levels of the open rotor without undue reduction in the large fuel burn benefit that results from the increased propulsive efficiency. The Environmental Design Space (EDS), developed at the Georgia Institute of Technology, is a conceptual level tool capable of capturing the interdependencies of fuel burn, noise, and emissions for both conventional and advanced engine and airframe architectures. Recently EDS has been updated to include an open rotor model capable of capturing the fuel burn, noise, and emissions impacts associated with an open rotor and the corresponding interdependencies between the metrics. This research capitalizes on these modeling efforts to investigate the operational space of an open rotor engine on a conventional tube and wing vehicle configuration. Trades between fuel burn and noise for a sized configuration are assessed. Benefits to noise and fuel burn are shown by changing the power management of the propeller during different phases of flight. Assessments in this research have been performed using a louder historical baseline blade set that is currently available in the public domain (F7/A7); however, the assessment will be repeated with a quieter historical baseline (F31/A31) in the future. Benefits of up to two percent fuel burn or five EPNdB cumulative noise are found through varying propfan rotational speed during different phases of operation.