Christopher E. Hughes

Glenn Research Center, Cleveland, Ohio

NASA Collaborative Research on the Ultra High 

Bypass Engine Cycle and Potential Benefi ts for 

Noise, Performance, and Emissions

NASA/TM—2013-216345

November 2013

ISABE–2009–1274
NASA STI Program . . . in Profi le

Since its founding, NASA has been dedicated to the 

advancement of aeronautics and space science. The 

NASA Scientifi c and Technical Information (STI) 

program plays a key part in helping NASA maintain 

this important role.

The NASA STI Program operates under the auspices 

of the Agency Chief Information Offi cer. It collects, 

organizes, provides for archiving, and disseminates 

NASA’s STI. The NASA STI program provides access 

to the NASA Aeronautics and Space Database and 

its public interface, the NASA Technical Reports 

Server, thus providing one of the largest collections 

of aeronautical and space science STI in the world. 

Results are published in both non-NASA channels 

and by NASA in the NASA STI Report Series, which 

includes the following report types:

• TECHNICAL PUBLICATION. Reports of 

completed research or a major signifi cant phase 

of research that present the results of NASA 

programs and include extensive data or theoretical 

analysis. Includes compilations of signifi cant 

scientifi c and technical data and information 

deemed to be of continuing reference value. 

NASA counterpart of peer-reviewed formal 

professional papers but has less stringent 

limitations on manuscript length and extent of 

graphic presentations.

• TECHNICAL MEMORANDUM. Scientifi c 

and technical fi ndings that are preliminary or 

of specialized interest, e.g., quick release 

reports, working papers, and bibliographies that 

contain minimal annotation. Does not contain 

extensive analysis.

• CONTRACTOR REPORT. Scientifi c and 

technical fi ndings by NASA-sponsored 

contractors and grantees.

• CONFERENCE PUBLICATION. Collected 

papers from scientifi c and technical 

conferences, symposia, seminars, or other 

meetings sponsored or cosponsored by NASA.

• SPECIAL PUBLICATION. Scientifi c, 

technical, or historical information from 

NASA programs, projects, and missions, often 

concerned with subjects having substantial 

public interest.

• TECHNICAL TRANSLATION. Englishlanguage translations of foreign scientifi c and 

technical material pertinent to NASA’s mission.

Specialized services also include creating custom 

thesauri, building customized databases, organizing 

and publishing research results.

For more information about the NASA STI 

program, see the following:

• Access the NASA STI program home page at 

http://www.sti.nasa.gov

• E-mail your question to help@sti.nasa.gov

• Fax your question to the NASA STI 

Information Desk at 443–757–5803

• Phone the NASA STI Information Desk at

 443–757–5802

• Write to:

 STI Information Desk

 NASA Center for AeroSpace Information

 7115 Standard Drive

 Hanover, MD 21076–1320
Christopher E. Hughes

Glenn Research Center, Cleveland, Ohio

NASA Collaborative Research on the Ultra High 

Bypass Engine Cycle and Potential Benefi ts for 

Noise, Performance, and Emissions

NASA/TM—2013-216345

November 2013

ISABE–2009–1274

National Aeronautics and

Space Administration

Glenn Research Center

Cleveland, Ohio 44135

Prepared for the 

19th International Symposium on Air Breathing Engines (ISABE 2009)

sponsored by the International Society for Air Breathing Engines

Montreal, Quebec, Canada, September 7–11, 2009
Available from

NASA Center for Aerospace Information

7115 Standard Drive

Hanover, MD 21076–1320

National Technical Information Service

5301 Shawnee Road

Alexandria, VA 22312

Available electronically at http://www.sti.nasa.gov

Acknowledgments

The research described in this paper is a collaborative effort between corporate and government entities and so are the 

contributions of many, many people to bring the planning and results of this research to light. The author wishes to thank 

the program and personnel line managers at the NASA Glenn, NASA Langley, NASA Ames, Pratt & Whitney, and General 

Electric Aviation for their gracious support, and I especially want to thank all the tireless engineers at these places for all the 

tremendous efforts and long hours they have put into their jobs to make this science a reality for the benefi t of all.

This work was sponsored by the Fundamental Aeronautics Program 

at the NASA Glenn Research Center.

Level of Review: This material has been technically reviewed by technical management. 
Abstract

The National Aeronautics and Space Administration 

has taken an active role in collaborative research with 

the U.S. aerospace industry to investigate technologies 

to minimize the impact of aviation on the environment. 

In December 2006, a new program, called the 

Fundamental Aeronautics Program, was established to 

enhance U.S. aeronautics technology and conduct 

research on energy, efficiency and the environment. A 

project within the overall program, the Subsonic Fixed 

Wing Project, was formed to focus on research related 

to subsonic aircraft with specific goals and time based 

milestones to reduce aircraft noise, emissions and fuel 

burn. This paper will present an overview of the 

Subsonic Fixed Wing Project environmental goals and 

describe a segment of the current research within 

NASA and also were worked collaboratively with 

partners from the U.S. aerospace industry related to the 

next generation of aircraft that will have lower noise, 

emissions and fuel burn. 

Introduction

NASA has a strong and successful of history 

collaborative research partnerships with the U.S. 

Aerospace Industry, Academia, and Other U.S. 

Government Agencies. Since the early 1990s, NASA 

research on subsonic aircraft propulsion has focused on 

the Ultra High Bypass (UHB) engine cycle to 

determine its potential for reducing noise, increasing 

aerodynamic performance and decreasing emissions. 

The NASA definition of the UHB cycle refers to a 

propulsive-to-power component mass flow ratio, or 

bypass ratio, greater than 13 to 1. Under previous 

NASA technology programs, UHB propulsion research 

efforts (Refs. 1, 2) were focused mainly on reducing 

noise of the propulsor and core components 

(principally fan and jet exhaust) of the turbofan, 

or ducted fan, engine through scale model testing in 

wind tunnel and component rig environments. With 

the creation of the Fundamental Aeronautics Program 

(FAP) Subsonic Fixed Wing (SFW) Project, subsonic 

aeronautics research has been refocused to include the 

entire aircraft and technologies related to reducing its 

environmental impact (Ref. 3). The project metrics are 

focused on reducing noise, emissions and fuel burn, 

and are segmented into three time frames spanning 

three generation of aircraft (N+1, N+2 and N+3) 

beyond the current generation, N (Fig. 1). 

Noise

(cum below Stage 4)

-60% -75% better than -75%

-33%** -40%** better than -70%

-33% -50% exploit metro-plex* concepts

N+1 = 2015***

Technology Benefits Relative

To a Single Aisle Reference

Configuration

N+2 = 2020***

Technology Benefits Relative

To a Large Twin Aisle

Reference Configuration

N+3 = 2025***

Technology Benefits

LTO NOx Emissions

(below CAEP 6)

Performance:

Aircraft Fuel Burn

Performance:

Field Length

-32 dB -42 dB -71 dB

CORNERS OF THE 

TRADE SPACE

***Technology Readiness Level for key technologies = 4-6

** Additional gains may be possible through operational improvements

* Concepts that enable optimal use of runways at multiple airports within the metropolitan area 

Figure 1. “Corners of the Trade Space” table showing 

Subsonic Fixed Wing Project system level metrics. 

Goals addressed by the research described in this paper 

(N+1) are shown highlighted in the red box. 

SFW Project propulsion research has also centered on 

the Ultra High Bypass (UHB) engine cycle and 

advanced technologies applicable to it as the direction 

to pursue to reach the project performance goals. The 

nearer term project goals are aimed at aircraft entering 

the commercial market in the 2015 time period (N+1). 

This paper will provide an overview of the 

collaborative, UHB-cycle focused research that the 

SFW Project and its U.S. industry partners are working 

on together to reach the N+1 environmental goals. 

Specific research subprojects will be highlighted that 

have contributed to meeting those goals, including a 

description of the subproject research, its objectives, 

and a brief summary of the test results obtained so far. 

Potential future NASA/Industry collaborative research 

NASA Collaborative Research on the Ultra High Bypass Engine Cycle and 

Potential Benefits for Noise, Performance and Emissions 

Christopher E. Hughes

National Aeronautics and Space Administration 

Glenn Research Center 

Cleveland, Ohio 44135 

,

NASA/TM—2013-216345 1
project plans in the area of UHB propulsion technology 

will also be briefly outlined. 

 

NASA/P&W Ultra High Bypass Turbofan Research

Under the Engine Validation of Noise and Emissions 

Reduction Technologies (EVNERT) task of the NASA 

Glenn Revolutionary Aero Space Engine Research 

(RASER) contract, which was sponsored by the NASA 

Quiet Aircraft Technology program, NASA and Pratt & 

Whitney (P&W) formed a collaborative partnership to 

develop an Ultra High Bypass engine demonstrator 

(Refs. 4, 5). The goal was to verify the potential 

advantages in reducing fuel burn, noise and emissions 

that could be achieved with an engine cycle having a 

fan to core flow bypass ratio of 13 and a fan pressure 

ratio of 1.3. P&W designed their engine, which they 

labeled the Geared Turbofan (GTF), with a geared Low 

Pressure Core fan allowing the core and fan to operate 

at different speeds, thus optimizing the performance 

and reducing the complexity of the core. Figure 2 

shows the projected noise and fuel burn reduction 

potential P&W predicted for the GTF compared with 

current technology turbofans. 

-50

-45

-40

-35

-30

-25

-20

-15

-10

-5

0

-50 -45 -40 -35 -30 -25 -20 -15 -10 -5 0

BASE % FUEL BURN

N+1

Goal

N+2

Goal

Counter-Rotation Propfan

“N+2”

BPR ~ 40-80

Current

BPR = 5

Geared Turbofan

“N+1”

BPR ~ 9-12

EIS ~ 2013

Geared Turbofan

“N+2”

BPR ~ 15-20

EIS~2018-2020

Figure 2. Pratt & Whitney chart of potential noise and 

fuel burn benefits of the Geared Turbofan compared 

with current generation UHB turbofans. Also shown is 

the potential fuel burn benefit of the P&W counter 

rotation propeller propulsion concept, as well as the 

progress required to achieve NASA N+1 performance 

goals. 

The N+1 noise goal is also shown in the figure for 

comparison, as well as the estimated fuel burn for a 

potential P&W counter rotation propeller propulsion 

concept. Figure 3 is a cutaway illustration of the GTF 

engine and identifies the areas of research that were 

successfully impacted by the NASA and P&W 

collaboration. In order to mitigate the risk of this 

advanced engine design, NASA and P&W 

collaboratively conducted two scale model wind tunnel 

tests to validate the design. 

Fan Drive Gear System

5 Planets

Gear Ratio ~ 3

Low PR Fan

Low Tip Speed

BPR ~ 9 - 12

High-Speed Low Spool

Compact LPC, LPT

Low-Emissions Combustor

Figure 3. The P&W Geared Turbofan and 

collaborative component technologies studied by the 

NASA/P&W research partnership under the NASA 

Quiet Aircraft Technology Program (QAT). 

The first was a 22” scale model test of the GTF bypass 

section, including the bypass fan, outlet stators, core 

inlet and nacelle simulation, conducted in the NASA 

Glenn anechoic 9- by 15-Foot Low Speed Wind Tunnel 

(9’x15’ LSWT) in 2006 (Left side in Fig. 4). 

NASA/P&W GTF 22” scale model test in the 

Glenn anechoic 9’x15’ LSWT

NASA/P&W GTF 12% semi-span scale model 

test in the Ames 11’ wind tunnel

Figure 4. Highlights of NASA/P&W collaborative, 

scale model tests of the Geared Turbofan. 

The test measured the aerodynamic performance, 

acoustic signature, and aeromechanical properties of 

the advanced bypass fan design. The model was run 

using the Glenn Ultra High Bypass Drive Rig 

propulsion simulator used to power turbofan models 

during testing in the wind tunnel. The test successfully 

met several key technology objectives: the high fan 

efficiency and low noise potential of the advanced, low 

pressure ratio, low tip speed UHB cycle were 

demonstrated; the design risk was successfully 

mitigated by identifying the aeromechanical properties, 

flutter or stall boundaries, of the advanced fan design. 

The data results from the 22” rig test were also used by 

NASA/TM—2013-216345 2
P&W to define the aerodynamic and acoustic design of 

the full scale GTF Engine Demonstrator. The second 

collaborative test to mitigate risk was an airframe 

integration test conducted in the Ames 11’ wind tunnel 

in 2008. The test objectives were to validate the 

predicted impact of the UHB nacelle on the aircraft 

wing in both high lift and cruise configurations, and to 

optimize its location to minimize the impact (Right side 

in Fig. 4). A 12% half-span scale model was designed 

by P&W and incorporated a powered, bypass ratio 9, 

engine simulator in a potential GTF nacelle 

configuration. Force balance measurements of the 

half-span model under power were obtained to measure 

the change in wing lift and moment coefficients at 

several fan speeds and various nacelle mounting 

locations relative to the wing. Flow diagnostic data in 

the form of Pressure Sensitive Paint and static pressure 

measurement on the wing, nacelle and engine pylon 

were also obtained to quantify the local flow physics. 

The results from the test successfully showed that no 

adverse impact on wing lift was produced for the range 

of nacelle configurations investigated (Ref. 6). In 

addition, this test paved the way for future 

collaboration between NASA and P&W by providing a 

baseline for investigating more advanced UHB 

installation studies. Additional scale model fan testing 

is also planned in the Glenn 9’x15’ wind tunnel for a 

NASA/P&W collaborative investigation of a second 

generation GTF, tentatively scheduled for late FY11. 

In 2008, the collaborative design effort for the GTF led 

to the first full scale engine demonstration at P&W 

facilities (Ref. 7). The engine demonstrator 

successfully validated the noise, fuel burn and LTO 

NOx emissions reductions possible with the UHB 

engine cycle (Fig. 5). 

NOISE -20 EPNdB

(cum margin to Ch 4)

LTO NOX -60%

(below CAEP 6)

FUEL BURN -15%

(relative to 737/CFM56)

Projected Based on 

Demonstrated Technology

Figure 5. Performance goals demonstrated during the 

collaborative NASA/P&W Geared Turbofan Engine 

Demonstrator Test in 2008. 

Engine component efficiencies met or exceeded P&W 

predictions, while the unique fan drive gear system 

demonstrated expected operational characteristics. As 

part of the GTF Demonstrator Engine test, NASA 

sponsored the first successful demonstration of an 

alternative fuel and its impact on performance and 

emissions (Ref. 8). Figure 6 shows the engine on the 

test stand and the engine exhaust gas sampling 

configuration, including photographs of the sampling 

probes used. 

GTF / Alternative Fuels test

Exhaust Gas Sampling Probes

Figure 6. Geared Turbofan Demonstrator Engine 

shown on P&W engine test stand during Alternative 

Fuels test. Inset in the center shows the exhaust gas 

sampling configuration. Inset on the right side of the 

picture is a close-up view of exhaust sampling probes 

used during testing. 

The fuel was a 50/50 blend of a Fischer-Tropsch (F-T) 

synthetic fuel and JP-8 aviation fuel. The fuel blend 

properties met all specifications for aviation fuel. 

Comparative tests using the alternative fuel and 

standard JP-8 were conducted with the GTF to 

determine performance and emissions impacts. The 

results showed positive trends in emission performance 

with no significant difference in gas emissions and 

reduced particle emissions with the alternative fuel. 

The most significant impact occurred at idle conditions, 

where both emissions were greatly reduced. 

Aerodynamic performance results provided by P&W 

from the test showed a negligible impact on engine 

TSFC. 

NASA UHB Fan Noise Reduction Research

To help meet the aggressive N+1 noise reduction goal 

of 32 dB cumulative below the Stage 4 noise 

regulation, the SFW Project supported a high fidelity 

wind tunnel experiment of a scale model UHB turbofan 

simulator to investigate the potential of two advanced 

noise reduction technologies, called Over-the-Rotor 

(OTR) metal foam acoustic treatment and Soft Vanes 

(SV) acoustically treated stator vanes, for the UHB 

engine cycle (Fig. 7). The technologies were 

developed in a partnership between the NASA Glenn 

Research Center and the NASA Langley Research 

Center. The testing was conducted in the NASA Glenn 

9’x15’ LSWT using the Glenn UHB Drive Rig 

propulsion simulator at test section velocities 

NASA/TM—2013-216345 3
simulating aircraft takeoff, approach and landing 

speeds. The goal of these two technologies was to 

reduce the noise generated by the fan rotor, and that 

generated by the interaction of the rotor wakes with the 

stator vanes with a minimum impact on the 

aerodynamic performance of the fan (Ref. 9). 

‘Over-the-Rotor’ fan case with

metal foam acoustic treatment

‘Soft Vanes’ acoustically

treated stator vanes

Figure 7. Illustration of the UHB Fan Model 

identifying the locations of two noise reduction 

technologies used during the NASA Ultra High Bypass 

Fan Noise Reduction Test, which were Over-the-Rotor 

acoustic treatment and Soft Stator Vanes. 

Both technologies were designed to modify the local 

unsteady pressure response to the flow perturbations 

and reduce the strength of the local noise sources by 

mitigating and absorbing the acoustic energy (Refs. 10, 

11). 

The Over-the-Rotor acoustic treatment was designed to 

replace the traditional hardwall fan case and rubstrip 

over the fan tip. The new design consisted of a 0.10” 

thick perforated hard plastic polymer flow surface with 

a 1.5” thick porous metal foam material behind it and 

contained within a steel shell which interfaced with the 

rest of the model hardware (Fig. 8). The hard plastic 

flow surface had 0.035” holes drilled into it resulting in 

a 20% open area and allowing the acoustic pressure 

disturbances to pass through into the metal foam liner 

behind it. The size and number of holes was designed 

to minimize impact on the fan aerodynamic 

performance. The metal foam had a density of 6% to 

8% (or 94% to 92% open area) with extremely small 

holes of approximately 100 pores per cubic inch of 

material. The metal foam presented a random and 

tortuous path to the incoming acoustic waves, forcing 

dissipation of the wave energy internally in the foam. 

The Soft Vanes were acoustically treated stator vanes 

designed as replacements for the cut-on set of 25 hard 

wall stator vanes that were used as the hardware 

baseline. The SV design consisted of a hollowed out 

metal shell in the aerodynamic shape of the existing 

vane. Internally, the hollow cavity was divided into 

four chambers of varying volumes, separated by thin 

metal membranes (Fig. 9). Each chamber was sized to 

dissipate the acoustic energy in a specific frequency, 

with the size of the chamber dependent on the target 

frequency. On the suction side of the vanes, from 

about 10% to 40% of the airfoil chord, the solid flow 

surface was perforated with 0.035” holes providing 

10% to 15% open area in the material. A fine metal 

mesh was placed over the surface holes to form a 

smooth aerodynamic flow surface. 

Figure 8. Photographs showing the porous Over-theRotor metal foam acoustic treatment used to replace the 

traditional fan case and rubstrip. Insets show close-ups 

of the porous flow surface of the replacement rubstrip 

and the foam metal treatment enclosed behind the 

porous rubstrip and metal fan case. 

Figure 9. Photographs of the Soft Stator Vanes model 

assembly. Insets show an individual Soft Stator Vane 

as well as the internal cavities and the porous, suction 

surface open area near the vane leading edge, which 

NASA/TM—2013-216345 4
allows acoustic pressure disturbances to penetrate into 

the cavities. 

The design allows the local acoustic waves on the vane 

suction surface to penetrate into the vane’s four internal 

chambers, where the acoustic energy would dissipate. 

There were a total of three metal foam designs 

investigated. The acoustic results obtained in this 

experiment showed that these first generation OTR and 

SV noise reduction technologies were successful in 

reducing the fan noise sources. Two of the three OTR 

acoustic treatments did reduce the fan noise in terms of 

Overall Sound Pressure Level produced by the fan tip 

flow interaction with the fan case up to 2 dB at fan 

speeds from 62% to 92% of the fan design speed. In 

terms of the corresponding fan aerodynamic 

performance, challenges remain to decrease the OTR 

impact at the blade tip. Fan adiabatic efficiency for the 

two promising OTR treatments decreased between 0.5 

and 4 percent across the fan operating speed range 

(Ref. 9). The SV acoustically treated stator vanes also 

showed up to 1 dB reduction in rotor-stator interaction 

noise achieved at most fan speeds. With the hardwall 

fan case installed with SV, there was negligible change 

in fan efficiency or thrust, and less than 0.5% loss in 

stage thrust (the combined fan and stator thrust). 

However, in both cases fan blade hardware problems 

prevented a full assessment of their potential acoustic 

benefits. The acoustic tests and results are described in 

Reference 12. Under the new NASA Environmentally 

Responsible Aviation (ERA) Project, second generation 

OTR and SV technologies are currently being 

considered for further investigation into their potential 

acoustic benefits. The anticipated scale model 

demonstration test of these second generation designs 

in the 9’x15’ LSWT is tentatively planned for late 

FY11. 

NASA/GE Open Rotor Research

With high oil and fuel prices in 2007 and 2008, the 

SFW Project embarked on new research campaign, in 

collaboration with General Electric Aviation (GE), to 

investigate open rotor propulsion for the next 

generation of commercial passenger aircraft. This type 

of propulsion had been previously investigated via 

another NASA/GE partnership in the late 1980s and 

early 1990s under the NASA Advanced Turboprop 

Project and GE’s GE36 Unducted Fan Program. A 

counter rotation propeller test rig developed for and last 

used during those programs was brought out of storage, 

the mechanical components revitalized, and the data 

systems and controls technology modernized by 

NASA. 

Scheduled to start in September 2009, a new test 

campaign will begin using this test rig, now known as 

the Open Rotor Propulsion Rig (ORPR), to investigate 

a series of advanced propeller fan blade designs to 

determine the potential fuel burn reduction that can be 

achieved today with open rotor propulsion (Fig. 10). 

Current estimates by GE are that modern open rotor 

propulsion will save 10% in fuel burn (with a 

commensurate reduction in CO2) immediately 

compared to current generation turbofan engine 

technology, and ultimately up to 25% with advanced 

open rotor designs (Fig. 11). 

Figure 10. Illustration of the NASA Glenn Open Rotor 

Propulsion Rig in a 12x10 propeller fan blade 

configuration in the Glenn anechoic 9’x15’ Low Speed 

Wind Tunnel. Also shown in the illustration is the 

generic engine pylon simulator and support sting 

installed in front of the rotors to determine installation 

effects on the rotor system performance. 

NASA/TM—2013-216345 5
% Improved Fuel Burn

EPNdB – Margin to Stage 4

Today’s

Standard

Open Rotor

BPR > 30

CFM

Advanced Turbofan

BPR ~ 9

Figure 11. Noise reduction and improved fuel burn 

potential of GE open rotor propulsion compared with 

current and advanced GE/CFM turbofan engine 

technology. 

During the test campaign, the acoustic noise levels 

produced by the new open rotor designs will be 

measured and characterized. Previous open rotor 

research during the 1980s had shown that while 

tremendous fuel savings were possible, the open rotor 

designs produced strong noise signatures that would 

need to be overcome before they could be incorporated 

into new aircraft designs. Based on previous 

experience and using today’s more advanced design, 

analysis, and performance prediction tools, the 

propeller fan blade designs can take advantage of 

modern materials and manufacturing techniques to 

produce three dimensional geometries to increase 

performance and reduce noise. Once the low speed 

flight regime has been investigated, promising fan 

blade candidates as well as the baseline design will 

undergo further high speed tests in the Glenn 8’x6’ 

High Speed Wind Tunnel. The aerodynamic 

performance of the fan blade designs at the simulated 

aircraft max climb/cruise flight regime will be 

investigated during this test campaign which is planned 

to start in mid 2010. 

The NASA ORPR has the two, independently driven 

air turbines capable of producing up to 750 shp per 

shaft to power each fan rotor. Each rotor assembly 

consists of a rotating dynamic force balance, rotating 

telemetry unit and fan blade hub (Fig. 12). 

Figure 12. Illustration of Open Rotor Propulsion Rig 

component layout, including orientation of the rotors, 

force balances and telemetry data systems. 

Aerodynamic forces produced by each rotor are 

measured with rotating dynamic force balances. Each 

rotor balance is capable of measuring up to 400 lbs of 

thrust and 450 ft-lbs of torque. The rotor telemetry unit 

has a 40 channel digital system through which fan 

blade strain gage signals and other pressure and 

temperature data acquired with each rotor are 

transmitted. The data signals are received by a nonrotating, co-located antenna, which sends the signals to 

a base ground station and then onto the facility data 

acquisition computer system. 

The current NASA/GE open rotor test campaign, 

initiated by SFW Project and now sponsored by the 

ERA Project, is a 12x10 fan blade hub configuration, 

meaning 12 blades on the forward row and 10 blades 

on the aft row (Fig. 13). In addition, NASA will 

investigate installation effects on the system 

aerodynamic and acoustic performance using a generic 

engine pylon simulator mounted in front of the first 

rotor (Fig. 13). 

Figure 13. Illustration of the complete Open Rotor 

Propulsion Rig test assembly with propeller fan blades, 

and shown in the Installed Configuration with engine 

pylon simulator. 

NASA/TM—2013-216345 6
Testing in the NASA Glenn 9’x15’ LSWT simulates 

aircraft flight conditions at takeoff, approach and 

landing, including angle of attack. The variable-pitch 

fan blades are a 1/5 scale model representation of a 

potential full scale engine design. The first blade set 

that will be tested (Fig. 14) will provide a baseline for 

comparison with other, more advanced GE designs. 

The model operating conditions investigated will 

provide data on fan blade performance across the range 

of expected aircraft operating conditions during the 

aircraft flight transition from ground idle to near 

takeoff rotation speed. Several freestream Mach 

numbers, rotor operating speeds, rotor power loading 

variations, fan blade pitch angles and model angles of 

attack will be investigated to determine their effect on 

the aerodynamic performance and acoustic noise 

signature of the system. The objective will be to 

determine the optimum conditions to maximize 

performance and minimize noise for the open rotor 

system. Test results obtained from the baseline 

propeller fan configuration will be used by NASA to 

compare and validate computer based design, analysis 

and optimization codes as well as aerodynamic and 

acoustic performance prediction codes. Six additional 

blade sets designed by GE and their industry partners 

will be tested to investigate and quantify the effect of 

blade geometry and configuration on the open rotor 

system aerodynamic efficiency, acoustic signature, and 

mechanical and aeroelastic stability. 

Forward Rotor Aft Rotor

Figure 14. Photos of the Open Rotor Baseline 

Propeller Fan Blades that will be tested in the NASA 

Glenn 9’x15’ LSWT in 2009 as part of the 

collaborative NASA/GE research test campaign into 

new Ultra High Bypass Propulsion Concepts for future 

aircraft. 

In addition to using the force balance to measure 

aerodynamic performance of each rotor, rotor disk 

loading profiles will be measured downstream of the 

aft rotor using a multi-sensor pressure/temperature rake 

and a flow angle rake. Diagnostic information such as 

flowfield turbulence in front of and behind each rotor 

will also be obtained using a traversing hot film sensor. 

Fan blade deflections under aerodynamic and 

centrifugal load will be recorded with a high speed 

video imaging system. NASA will test three new 

diagnostic testing techniques at the end of the test to 

understand the flowfield dynamics. The first 

diagnostic technique is Particle Image Velocimetry 

(PIV) (Ref. 13), which will be used to understand the 

flow field surrounding and between the rotors. PIV 

uses a sheet laser to illuminate seeding material 

dispersed throughout the flow field to visualize its 

characteristics. The images are recorded with cameras 

located near the model. The second diagnostic 

technique is Pressure Sensitive Paint (PSP) (Ref 14), 

which will be used to visualize the pressure and 

temperature distributions on the propeller fan blade 

surfaces. A special light sensitive paint is applied to 

the individual blades which are then illuminated with a 

black light during testing. The illumination changes 

color as the pressure and temperature on the fan blades 

change. The images are recorded with sensitive high 

speed cameras. The last diagnostic technique is an 

acoustic Phased Array (PA) (Ref. 15). An array of 

microphones is accurately mounted in a spiral 

arrangement on a flat plate. The system is used to 

simultaneously record acoustic information from the 

microphone array in a specific area on the model, and 

then special software algorithms are used to quantify 

the noise levels in the measurement area. This 

technique will be used to identify high level noise 

sources on the model for further investigation. 

Summary

The collaborative research on the Ultra High Bypass 

engine cycle conducted by U.S. Industry and NASA 

through the Fundamental Aeronautics Program’s 

Subsonic Fixed Wing Project has been reviewed in this 

paper. Three specific areas of research have been 

highlighted: UHB fan noise reduction technology in 

collaboration with NASA Langley; Open Rotor 

propulsion technology in collaboration with GE 

Aviation; and Geared Turbofan technology in 

collaboration with Pratt & Whitney. In all three areas, 

research was performed to address the system level 

metrics of the SFW Project to mitigate the impact 

commercial aircraft have on the environment by 

reducing aircraft noise, fuel burn and emissions. 

NASA/TM—2013-216345 7
Under Ultra High Bypass Engine Cycle research, 

NASA has teamed with P&W to develop and 

demonstrate an UHB demonstrator engine which P&W 

has labeled the Geared Turbofan. The tremendous 

performance potential of this engine cycle was 

successfully demonstrated by P&W in a full-scale 

static engine test in 2008. Prior to this test, NASA and 

P&W jointly conducted two scale model wind tunnel 

tests to understand the performance and operating 

characteristics of the fan and impact of the UHB 

installation on the aircraft. A 22” fan test was 

conducted in the Glenn 9’x15’ wind tunnel which 

successfully documented the fan blade aero design 

performance and noise characteristics. The results 

were directly used to in the full scale GTF design. The 

second test was a 12% half-span aircraft wing test in 

the Ames 11’ wind tunnel to understand and minimize 

the impact of the UHB fan/nacelle on the wing 

aerodynamics. The successful test results defined the 

optimum position of the engine on the wing. 

Under the NASA fan noise reduction technology effort, 

two technologies have been investigated to reduce the 

noise signature of fan noise sources: Over-the-Rotor 

acoustic treatment and Soft Vanes acoustically treated 

stators. Testing recently completed in late 2008 show 

first generation designs were able to reduce the noise 

signature of the fan tip flow interaction with the fan 

case by as much as 2 dB in certain flight regimes, but 

model hardware problems prevented a demonstration 

of its full potential. Fan performance losses were on 

the order of 0.5 to 4 percent in adiabatic efficiency in 

the same fan speed operating ranges. Soft Vanes were 

able to reduce the rotor-stator interaction noise source 

up to 1 dB over the fan operating speed envelope. 

Further research is being planned to enhance noise 

reduction capabilities of these technologies. 

Under Open Rotor propulsion technology, NASA and 

GE have entered into a Space Act Agreement to 

collaboratively explore open rotor technology to 

significantly reduce fuel burn and carbon footprint. 

NASA has reactivated and modernized its counter 

rotation propeller test rig previously used during the 

1980s with GE in the Unducted Fan program under the 

NASA Advanced Turboprop Project. The new rig 

named the Open Rotor Propulsion Rig will be used by 

GE in testing in the NASA Glenn anechoic 9’x15’ Low 

speed Wind Tunnel to investigate new, modern fan 

blade designs and establish the potential fuel burn 

reduction that can be achieved, as well as document the 

acoustic signature of the concept and establish noise 

levels relative to Stage 4 aircraft noise regulations. 

Testing will begin in September 2009 with a baseline 

fan blade configuration. Follow-on testing to establish 

the high speed cruise performance of the open rotor 

configurations in the Glenn 8’x6’ High Speed Wind 

Tunnel is also planned for mid 2010. 

Under the Subsonic Fixed Wing Project and the new 

Environmentally Responsible Aviation Project, NASA 

will continue its collaboration with the U.S. Industry, 

Academia and other Government Agencies to 

investigate new technologies to reach the aggressive 

goals set forth by U.S. President and Congress and 

minimize the impact of commercial aviation on our 

environment. 

References

1. Bridges, J., Envia, E., and Huff, D., “Recent 

Developments in U.S. Engine Noise Reduction 

Research,” NASA/TM-2001-211083, ISABE-2001-

1017, Sep. 2001. 

2. Envia, E., “Fan Noise Reduction: An Overview,” 

NASA/TM-2001-210699, AIAA-2001-0661, February 

2001. 

3. Collier, F., Del Rosario, R., Heidmann, J., 

“Subsonic Fixed Wing Overview,” General Electric 

Aviation/NASA Fundamental Aeronautics Program 

Technology Integration Meeting, March 2009. 

4. Hughes, C. and Schweitzer, J., “Ultra High Bypass 

Ratio Engine Research for Reducing Noise, Emissions, 

and Fuel Consumption,” NASA Fundamental 

Aeronautics Program 1nd Annual Meeting, New 

Orleans, LA, October 30 – November 1, 2007. 

5. Hughes, C., Lord, W., and Masoudi, S., “NASA / 

Pratt & Whitney Collaborative Partnership Research in 

Ultra High Bypass Cycle Propulsion Concepts,” NASA 

Fundamental Aeronautics Program 2nd Annual 

Meeting, Atlanta, GA, October 7-9, 2008. 

6. Flamm, J. D., Smith, S. C., Porter, B. J., Hughes, C., 

and Zysman, S., “Powered Propulsion Airframe 

Integration Study in the ARC 11-Ft Transonic Wind 

Tunnel,” NASA Fundamental Aeronautics Program 

2nd Annual Meeting, Atlanta, GA, October 7-9, 2008. 

7. Hughes, C.E., “An Overview of the NASA 

Fundamental Aeronautics Program Subsonic Fixed 

Wing Project and Ultra High Bypass Partnership 

Research Goals,” Oral Presentation, 15th AIAA/CEAS 

Aeroacoustics Conference, May 2009. 

NASA/TM—2013-216345 8
8. Anderson, B.E., “Alternative Fuels Emissions and 

Performance Test Program,” NASA Fundamental 

Aeronautics Program 2nd Annual Meeting, Atlanta, 

GA, October 7-9, 2008 

9. Hughes, C.E., and Gazzaniga, J.A., “Effect of Two 

Advanced Noise Reduction Technologies on the 

Aerodynamic Performance of an Ultra High Bypass 

Ratio Fan,” AIAA-2009-3139, May 2009. 

10. M. Jones, T. Parrott, D. Sutliff, and C. Hughes, 

“Assessment of Soft Vane and Metal Foam Engine 

Noise Reduction Concepts,” AIAA-2009-3142, May 

2009. 

11. B. Howerton and T. Parrott, “Validation of an 

Acoustic Impedance Prediction Model for Skewed 

Resonators,” AIAA-2009-3143, May 2009. 

12. D. Elliott, R. Woodward, and G. Podboy, “Acoustic 

Performance of Novel Fan Noise Reduction 

Technologies for a High Bypass Model Turbofan at 

Simulated Flight Conditions,” AIAA-2009-3140, May 

2009 

13. Wernet, M. P., 'Development of particle imaging 

velocimetry for use in turbomachinery', Experiments 

in Fluids, 28, 2000. 

14. Gregory, JW, Asai, K, Kameda, M, Liu, T, and 

Sullivan, JP, 2008, “A Review of Pressure-Sensitive 

Paint for High Speed and Unsteady Aerodynamics,” 

Proceedings of the Institution of Mechanical Engineers, 

Part G, Journal of Aerospace Engineering, vol. 222, no. 

2, pp. 249-290. 

15. Dougherty, R., “Phased Array Technology Applied 

to Aeroacoustics,” Keynote Address, 15th AIAA/CEAS 

Aeroacoustics Conference, May 2009. 

NASA/TM—2013-216345 9
REPORT DOCUMENTATION PAGE Form Approved 

OMB No. 0704-0188 

The public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the 

data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this 

burden, to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0188), 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302. 

Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB 

control number. 

PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. 

1. REPORT DATE (DD-MM-YYYY)

01-11-2013 

2. REPORT TYPE

Technical Memorandum 

3. DATES COVERED (From - To)

4. TITLE AND SUBTITLE

NASA Collaborative Research on the Ultra High Bypass Engine Cycle and Potential Benefits 

for Noise, Performance, and Emissions 

5a. CONTRACT NUMBER

5b. GRANT NUMBER

5c. PROGRAM ELEMENT NUMBER

6. AUTHOR(S)

Hughes, Christopher, E. 

5d. PROJECT NUMBER

5e. TASK NUMBER

5f. WORK UNIT NUMBER

WBS 561581.02.08.03.11.55 

7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)

National Aeronautics and Space Administration 

John H. Glenn Research Center at Lewis Field 

Cleveland, Ohio 44135-3191 

8. PERFORMING ORGANIZATION

 REPORT NUMBER

E-17282 

9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES)

National Aeronautics and Space Administration 

Washington, DC 20546-0001 

10. SPONSORING/MONITOR'S

 ACRONYM(S)

NASA 

11. SPONSORING/MONITORING

 REPORT NUMBER

NASA/TM-2013-216345 

12. DISTRIBUTION/AVAILABILITY STATEMENT

Unclassified-Unlimited 

Subject Category: 07 

Available electronically at http://www.sti.nasa.gov 

This publication is available from the NASA Center for AeroSpace Information, 443-757-5802

13. SUPPLEMENTARY NOTES

14. ABSTRACT

The National Aeronautics and Space Administration has taken an active role in collaborative research with the U.S. aerospace industry to 

investigate technologies to minimize the impact of aviation on the environment. In December 2006, a new program, called the Fundamental 

Aeronautics Program, was established to enhance U.S. aeronautics technology and conduct research on energy, efficiency and the 

environment. A project within the overall program, the Subsonic Fixed Wing Project, was formed to focus on research related to subsonic 

aircraft with specific goals and time based milestones to reduce aircraft noise, emissions and fuel burn. This paper will present an overview 

of the Subsonic Fixed Wing Project environmental goals and describe a segment of the current research within NASA and also were worked 

collaboratively with partners from the U.S. aerospace industry related to the next generation of aircraft that will have lower noise, emissions 

and fuel burn. 

15. SUBJECT TERMS

Propulsion; Rotors; Turbofans; Turboprop engines; Air breathing propulsion; Noise reduction; Counter rotation; Engine noise; 

Propeller fans; Wind tunnel models; Scale models 

16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF

 ABSTRACT

UU 

18. NUMBER

 OF 

 PAGES

16 

19a. NAME OF RESPONSIBLE PERSON

STI Help Desk (email:help@sti.nasa.gov) 

a. REPORT

U 

b. ABSTRACT

U 

c. THIS 

PAGE

U 

19b. TELEPHONE NUMBER (include area code)

443-757-5802 

Standard Form 298 (Rev. 8-98)

Prescribed by ANSI Std. Z39-18