Ultra High Bypass Ratio Engine Sizing and Cycle Selection Study for a Subsonic Commercial Aircraft in the N+2 Timeframe

Abstract

This paper presents an engine sizing and cycle selection study of ultra high bypass ratio engines applied to a subsonic commercial aircraft in the N+2 (2020) timeframe. NASA has created the Environmentally Responsible Aviation (ERA) project to serve as a technology transition bridge between fundamental research (TRL 1–4) and potential users (TRL 7). Specifically, ERA is focused on subsonic transport technologies that could reach TRL 6 by 2020 and are capable of integration into an advanced vehicle concept that simultaneously meets the ERA project metrics for noise, emissions, and fuel burn. An important variable in exploring the trade space is the selection of the optimal engine cycle for use on the advanced aircraft. In this paper, two specific ultra high bypass engine cycle options will be explored: advanced direct drive and geared turbofan. The advanced direct drive turbofan is an improved version of conventional turbofans. In terms of both bypass ratio and overall pressure ratio, the advanced direct turbofan benefits from improvements in aerodynamic design of its components, as well as material stress and temperature properties. By putting a gear between the fan and the low pressure turbine, a geared turbo fan allows both components to operate at optimal speeds, thus further improving overall cycle efficiency relative to a conventional turbofan. In this study, sensitivity of cycle design with level of technology will be explored, in terms of both cycle parameters (such as specific thrust consumption (TSFC) and bypass ratio) and aircraft mission parameters (such as fuel burn and noise). To demonstrate this sensitivity, engines will be sized for optimal performance on a 300 passenger class aircraft for a 2010 level technology tube and wing airframe, a N+2 level technology tube and wing air-frame, and finally on a N+2 level technology blended wing body airframe with and without boundary layer ingestion (BLI) engines.

On the Optimization of a Geared Fan Intercooled Core Engine Design

“…Since the study considers engine weight, the results on optimal specific thrust and jet velocity ratio are specific to the geared arrangement. Although existing geared fan engines have not yet reached 70,000 Ibf thrust, the authors would expect them to continue to show a weight benefit relative to direct drive fan engines up to considerably higher thrust levels; this expectation is also supported by recent research on large geared turbofans [39][40][41], Paul Adams, senior vice president of engineering at Pratt and Whitney, was quoted in 2010 [42] as say ing that "the overall concept of the geared turbofan is scalable up to pretty much any size." Eventually, the geared solution may stop saving weight, but perhaps only in a much bigger engine.…”

Geometry-Based Shape Optimization to Improve Dynamical Behaivior of Planetary Gear Boxes in Aero Engines

“…At each point % a support line of length % is created perpendicular to the inner contour. The endpoints of the support lines represent the defining points of the outer contour B-spline through (3). The length % is determined through a third, formative curve (5), shown in figure 7(B), which describes the thickness distribution along the component.…”

“…The aerospace environment requires the gearbox to be applicable for high speeds and high torque while being light weight, raising many design challenges. [1] [2] [3] Challenges like these necessitate sophisticated design processes. Optimizing designs in the early development stages become increasingly important to minimize the number of necessary design iterations, resulting in time and cost savings.…”

Improved Pareto Optimal Engine Cycle Designs Through the Use of a New Pareto Quality Indicator

“…3 EDS consists of an integrated suite of modules, design rules/logic, and user defined design parameters. The modules include compressor map generation through CMPGEN, 4,5 thermodynamic cycle analysis through NPSS, 6,7 engine flow path analysis and weight estimation using WATE, 8,9 aircraft sizing and synthesis through FLOPS, 10 the P3-T3 method 11 for emissions based correlation derivations, and ANOPP 12,13 for calculating vehicle noise.…”