Analysis of Turbofan Design Options for an Advanced Single-Aisle Transport Aircraft

Abstract

The desire for higher engine efficiency has resulted in the evolution of aircraft gas turbine engines from turbojets, to low bypass ratio, first generation turbofans, to today's high bypass ratio turbofans. It is possible that future designs will continue this trend, leading to very-high or ultra-high bypass ratio (UHB) engines. Although increased bypass ratio has clear benefits in terms of propulsion system metrics such as specific fuel consumption, these benefits may not translate into aircraft system level benefits due to integration penalties. In this study, the design trade space for advanced turbofan engines applied to a single-aisle transport (737/A320 class aircraft) is explored. The benefits of increased bypass ratio and associated enabling technologies such as geared fan drive are found to depend on the primary metrics of interest. For example, bypass ratios at which fuel consumption is minimized may not require geared fan technology. However, geared fan drive does enable higher bypass ratio designs which result in lower noise. Regardless of the engine architecture chosen, the results of this study indicate the potential for the advanced aircraft to realize substantial improvements in fuel efficiency, emissions, and noise compared to the current vehicles in this size class.

Initial Assessment of Open Rotor Propulsion Applied to an Advanced Single-Aisle Aircraft

“…Fuel consumption reductions of ~30% relative to 1990s technology have been found for advanced turbofan engines on an advanced technology airframe. 17 However, the airframe and mission assumptions for study described in Ref. 17 are not the same as for this initial open rotor analysis.…”

“…17 However, the airframe and mission assumptions for study described in Ref. 17 are not the same as for this initial open rotor analysis. Additional work is needed to perform a true "apples-to-apples" comparison between advanced turbofan and open rotor configurations.…”

“…Previous NASA studies of propulsion options for 737/A320 replacement designs have used a Boeing 737-800 based airframe model and design mission. 15,17 The MD-90-30-based model described above differs from the 737-800-based model in a number of respects. Of critical importance in developing a consistent technology baseline is the level of airfoil design technology for the MD-90-30 wing.…”

Overview of the NASA Environmentally Responsible Aviation Project's Propulsion Technology Portfolio

“…'?2"55,''H1<$0' In Figure 2, the fuel burn savings potential from using advanced aircraft technologies available in 2020 (N+2) is shown for both a conventional large twin aisle vehicle with a circular fuselage and an advanced hybrid wing body advanced vehicle configuration (Refs. [3][4][5]. It is predicted that advanced engine technology will contribute between about 15.3% and 18.5% of the total savings, depending on airframe type, compared with a large twin aisle aircraft.…”

NASA Environmentally Responsible Aviation Project's Propulsion Technology Phase I Overview and Highlights of Accomplishments

“…[3][4][5]. It is predicted that advanced engine technology will contribute between about 15.3% and 18.5% of the total savings, depending on airframe type, compared with a large twin aisle aircraft.…”