Technical Challenges to Reducing
Thrust Specific Energy Consumption
AIAA Aerospace Sciences Meeting
January 9-12, 2012
Michael D. Hathaway
Technical Lead – Efficient Propulsion and Power (EPP)
Subsonic Fixed Wing Project
[email protected]
Subsonic Fixed Wing Project
Fundamental Aeronautics Program
216-433-6250
1
Outline of Presentation
• High Level Overview Subsonic Fixed Wing Project (Emphasis on N+3)
• Challenges to Reduce thrust specific energy consumption
• N+3 advanced concept technologies for reducing TSEC
– focus, goal, technical content
– sample highlights
• Summary of technical challenges to reducing TSEC
Subsonic Fixed Wing Project
Fundamental Aeronautics Program
2
SFW Strategic Thrusts & Technical Challenges
Energy Efficiency Thrust (with emphasis on N+3)
Develop economically practical approaches to improve aircraft efficiency
Environmental Compatibility Thrust (with emphasis on N+3)
Develop economically practical approaches to minimize environmental impact
Energy & Environment
Cross-Cutting Challenge (pervasive across generations)
TC1 - Reduce aircraft drag with minimal impact on weight (aerodynamic
efficiency)
Drag
TC2 - Reduce aircraft operating empty weight with minimal impact on
drag (structural efficiency)
Weight
TC3 - Reduce thrust-specific energy consumption while minimizing
cross-disciplinary impacts (propulsion efficiency)
TSEC
TC4 - Reduce harmful emissions attributable to aircraft energy
consumption
Reduce
TSEC
Reduce
Noise
Maintain
Safety
Reduce
OWE
Reduce
Drag
Reduce
Emissions
Clean
TC5 - Reduce perceived community noise attributable to aircraft with
minimal impact on weight and performance
Noise
TC6 - Revolutionary tools and methods enabling practical design,
analysis, optimization, & validation of technology solutions for vehicle
system energy efficiency & environmental compatibility
Subsonic Fixed Wing Project
Fundamental Aeronautics Program
Economically
Viable
Enable Advanced Operations
Revolutionary Tools and Methods
Tools
3
NASA Subsonic Transport System Level Metrics
…. technology for dramatically improving noise, emissions, & performance
Subsonic Fixed Wing Project
Fundamental Aeronautics Program
FAA/CLEEN
NASA/ERA
NASA SFW
4
SFW N+3 Opportunities from Goal-Driven Advanced Concepts
broadly applicable . . . .
N+3 Subsystem Concepts Goal-Driven Advanced Concepts
1. Tailored Fuselage
2.
High AR Elastic Wing
3.
Quiet, Simplified High-Lift
TSEC 4.
High Efficiency Small Gas Generator
TSEC 5.
Hybrid Electric Propulsion
TSEC 6.
Propulsion Airframe Integration
Near Term/Cross-cutting
Tools
7.
Alternative Fuels
8.
Tool Box (MDAO, Systems Modeling, Physics-Based)
Subsonic Fixed Wing Project
Fundamental Aeronautics Program
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Efficiency Challenge:
Reduce Thrust-Specific Energy Consumption
Hot Section Materials
• Hybrid disk concepts
• High temp non-contacting seals
• CMC development under Supersonics
Project
• Corrosion coatings
SX/PX
Rim
1500F
•
•
•
•
•
Propulsion Components
Efficiency potential of small cores
Tip and endwall loss mitigation
Highly loaded HPT technology
Advanced/novel cooling concepts
Reduce aero performance impact of film
cooling
• Axial-centrifugal compressors
• Variable area nozzles
Economical and practical approaches for
improving aircraft efficiency by reducing
thrust-specific energy consumption with
negligible cross-disciplinary impact
2002
Innovative Propulsion and
Power Architectures
PM
Bore
1300F
Propulsion Sensors and Controls
• Distributed engine controls
• High-temperature sensors and
electronics components
• Model-based engine control
• Active flow, compressor stall, and tip
clearance control
Benefits of Successful Completion
Novel Turbine Cooling Concepts
• Electric and hybrid-electric, distributed
propulsion
• BLI, embedded, and other integrated
inlet/fan architectures
• Pressure gain combustion
• Innovative engine cycles (variable,
adaptive, inter-cooling, inter-turbine
burning, reheating)
Efficient Electric Systems
Tools and Fundamental Research
• CFD modeling (LES model for
propulsion, aeroelasticity, materials)
• Experimental techniques
• Flow control validation database
Subsonic Fixed Wing Project
Fundamental Aeronautics Program
• Low AC loss superconductors
• High performance cryo coolers,
conductors, and power converters
• BNNT based supercapacitor
• Modeling electric components
• High specific energy batteries
• High power density fuel cells
SFW Funded
Superconducting generator
Cryogenic
Power Inverter
Partner Funded
Future Work
6
Efficiency Challenge:
Reduce Thrust-Specific Energy Consumption
What are we trying to do?
• Discover, explore, and develop technology concepts to improve propulsion
efficiency for overall system-level benefit to energy efficiency and environment
Why?
• Meet energy efficiency challenge by reducing thrust-specific energy consumption
How is it done today, and what are the limits of current practice?
• Conventional turbofan engines pod-mounted on tube-and-wing airframes
• Bypass ratios limited to ~12 and overall pressure ratios to ~40, thus limiting
achievable propulsive and thermal efficiency
What is new in our approach?
• New technologies to increase component efficiencies of conventional engines
enabling small core for increased BPR (~20) and higher OPR capability (50+).
• Revolutionary and new enabling technologies for embedded, distributed
propulsion, and hybrid/electric
• Techniques to understand, analyze, and predict performance of unconventional
and revolutionary designs
What are the payoffs if successful?
• Economical and practical approaches to improving aircraft efficiency by reducing
thrust-specific energy consumption, also emissions, noise, and operating costs
Subsonic Fixed Wing Project
Fundamental Aeronautics Program
7
Efficiency Trends with Core and Propulsor Improvements
 Propulsion system improvements require advances in both propulsor and core technologies
Core Thermal Efficiency (ηth)
0.8
0.1
0.2
Overall Efficiency (ηth x ηp)
0.3
0.8 0.7
0.6
0.4
0.5
0.5
0.4
0.7
0.6
Core
Improvements
0.5
0.6
0.3 TSFC
Ultra-high
BPR
B-777
B-747
Low BPR
High BPR
Propfan
Turbojets
0.4
Propulsor
Improvements
0.3
Whittle
0.2
Subsonic Fixed Wing Project
Fundamental Aeronautics Program
0.3
0.4
0.5
0.6
Propulsive x Transmission Efficiency (ηp)
0.7
0.8
8
Thermal Efficiency Trend with Compressor Pressure Ratio
 Current technology level is OPR ~40
 N+3 goal is OPR ~60
Thermal Efficiency
0.7
0.6
Current
Technology
0.5
0.4
0.3
0.2
0.1
0
0
Subsonic Fixed Wing Project
Fundamental Aeronautics Program
10
20
30
Compressor Pressure Ratio
40
50
9
Variation in Core Power with Turbine Inlet Temperature
Hydrocarbon
Stoichiometric
Limit
Specific Core Power (hp/lb/sec)
1000
800
600
400
200
0
1200
Von Ohain (1939)
Ideal Brayton
Cycle Performance
Whittle (1937)
JT8D
J47
J57
J42
1600
J52
J79
J58
2000
N+3Goal
Goal
N+3
PW2037
F100
PW4000
TF30
2400
Current
Current
Technology
Technology
2800
3200
3600
4000
4400
Turbine Rotor Inlet Temperature (Deg F)
Subsonic Fixed Wing Project
Fundamental Aeronautics Program
10
High Efficiency Small Gas Generator
Focus: Develop technologies to enable high pressure ratio cores and mitigate the performance loss of small core
high pressure ratio turbomachinery.
Goal: Enable higher bypass ratio fans (~20) and higher OPR engines (50+). Reduce efficiency decrement of small
core stages with large (~4%) tip clearance to span.
Technical Content:
1500F Hybrid Disk: Develop a Hybrid disk approach, in which a powder metallurgy disk alloy is bonded to a creepresistant alloy rim with 1500 F temperature capability. Develop techniques for bonding rim alloy to disk alloy.
Understand and develop coatings to mitigate environmental degradation (oxidation and hot corrosion) issues.
High temperature seals: Develop advanced, validated design tool for calculating leakage rates, power loss, lift-off,
and dynamic response of advanced seal concepts, conducting CFD and structural modeling of concepts to guide
seal designs, testing seals at relevant operating conditions to measure performance and validate design tools.
Tip clearance/endwall loss mitigation: Detailed experimental measurements and computational investigations for
enhanced physics insight and concepts for mitigating tip leakage and end wall losses in small cores with large
clearance to span (NASA NRAs).
Model Based/Distributed Engine Control: Developing engine control technologies for reduced fuel burn via optimal
based control of engines throughout the life of the engine, and developing foundation technologies and basic
infrastructure to transition engine control implementation from central to distributed.
Subsonic Fixed Wing Project
Fundamental Aeronautics Program
11
Optimal Microstructures for Bore and Rim Areas of
Hybrid Disk Identified
• Problem: Higher temperature disk materials
needed to meet N+3 Goals.
SX/PX
Rim
• Objective: Quantify maximum temperature
capability of 3rd generation PM disk alloy and
selected cast blade alloys to enable development of
hybrid disk concepts which allow 100-200 F
increase in temperature.
• Approach: Develop processing technology for
varied grain sizes in powder (AFRL 1400 F) and cast
(NASA 1500 F) alloys. Creep, tensile, stress
relaxation, notch fatigue tests at 1300 F and 1500 F.
• Results: Test results show alloy rankings change
as temperature increases.
• Significance: Test results clearly show potential of
hybrid disk concept, as optimal alloy/microstructure
changes from bore to rim temperatures. Preferred
rim concept with superior benefits identified.
Subsonic Fixed Wing Project
Fundamental Aeronautics Program
1500°F
1300°F
PM
Bore
PM Bore
Grain Size
SX/PX Rim
Grain Size
Research Team: Tim Gabb/RXA (lead), Chantal Sudbrack/RXA, Rebecca MacKay/RX, and Michael Nathal/RXA
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NRA Topic 2.5 - Understanding & Mitigating
Tip Leakage & End Wall Losses in High Pressure Ratio Cores
Organization(s)
PI
Purdue U., Rolls-Royce
Prof. Key
An Experimental Investigation of the Flow Physics Associated with
End Wall Losses and Large Rotor Tip Clearances as
Found in the Rear Stages of High Pressure Compressor
John Hopkins U.
Prof. Katz
High Resolution Measurements of the Effects of Tip Geometry on
Flow Structure and Turbulence in the Tip Region of a Rotor Blade
Honeywell, U. Notre Dame
Dr. Malak
High Pressure Turbine Tip Clearance Data and High Fidelity Analyses
P&W, Penn State
Dr. Praisner
Understanding and Mitigating Tip Leakage and Endwall Losses in
High Pressure Ratio Cores
Naval Academy, CSU
Prof. Volino
Experimental and Computational Investigation of Unsteady
Endwall and Tip Gap Flows in Gas Turbine Passages
Subsonic Fixed Wing Project
Fundamental Aeronautics Program
13
MIT Phase II NRA – Small Core Subtask
• Define limits to performance of high PR axial compressors
(mcorr ~ 1.0 lbm/s, CFM 56 ~ 7 lbm/s)
- Identify mechanisms setting performance limits
- Address mechanisms on fundamental level
- Focus on multistage environment
• Quantitatively assess the potential for mitigating performance limits
- This encompasses innovative engine architectures
(layouts distinct from current engine)
• Define specific experiments for assessments of mechanisms
Subsonic Fixed Wing Project
Fundamental Aeronautics Program
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Hybrid Electric Propulsion
Focus: Developing technologies in support of hybrid electric engine concepts, with specific focus on the NASA turboelectric distributed propulsion vehicle concept; developing capability for more accurate analysis of electric components
and of the complete distributed propulsion system, development and modeling of superconducting motors, cryoinverters, cryo-coolers, and development of higher temperature capable superconducting materials.
Goal: Improve modeling of electric components.
Technical Content:
Turboelectric distributed propulsion (TeDP) analysis: Developing capability for more accurate modeling of electric
components and of the total electric propulsion system.
High specific power superconducting motor: Developing and demonstrating configurations and materials for high
power density superconducting machines.
Superconducting materials: Developing low AC loss superconducting materials for high specific power motors.
Boron nitride nanotube supercapacitors: Developing boron nitride nanotube based supercapacitor and integration with
structure.
Lightweight cryo inverter: Development of a cryogenic power inverter with high specific power capability.
Total electrical system for TeDP: Development and demonstration of the TurboElectric Distributed Propulsion power
train from sub-scale to full-scale.
Subsonic Fixed Wing Project
Fundamental Aeronautics Program
15
Light, Efficient Components for TeDP Must Be
Cryogenic or Superconducting
TeDP Technical challenges are
soluble and being pursued:
Superconducting transmission lines
between generators and motors
Utilities & Air Force are working this
Cryogenic Inverter for
variable speed fans
Weight ½ SOA & ~1/10th SOA loss
Phase 2 SBIR @ MTECH Labs
In-House Cryo-inverter Tests
Turbine engine driven
superconducting generator/motors
1/10th SOA weight &
low AC losses
NRA Advanced Magnet Lab
Subsonic Fixed Wing Project
Fundamental Aeronautics Program
Superconducting motors
drive propulsive fan array
Cryocooler(s) for
cryogenic components
1/5th SOA weight
Phase 1 SBIR @ Creare, Inc.
Total electric system
Distribute ~50 MW in a stable
& responsive grid
RTAPS Contract @ Liberty Works
In-House Subscale System Model
16
Boeing/GE SUGAR “Volt”
“hFan” Gas Turbine-Electric Hybrid Engine Overview
Subsonic Fixed Wing Project
Fundamental Aeronautics Program
17
Electrical Capability: Where Are We?
•
•
Present capabilities for batteries do not meet required levels for large commercial applications …
similarly for fuel cells
Present electrically powered aircraft providing technology maturation/test bed for proof of concept
Subsonic Fixed Wing Project
Fundamental Aeronautics Program
Dr. Dale Carlson, GE Aviation (EAA Electric Flight Symposium, July 2011)
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Propulsion Airframe Integration
Focus: Support development of high efficiency, robust design of boundary layer ingesting/embedded fan for
propulsor concepts closely integrated with inlet/airframe.
Goal: Design distortion tolerant fan with <2% efficiency decrement.
Technical Content:
Distortion tolerant fan design: Monitoring NRA with United Technologies Research Center supporting the
aerodynamic and mechanical design of a boundary layer ingesting, distortion tolerant fan with non-axisymmetric
vanes.
Aeroelastic analysis capability: Support development of aeroelastic analysis capability and analysis of coupled
inlet/distortion tolerant fan aeroelasiticity, including in-house support of the aero mechanical analysis and
concurrence fan is aeromechanically sound for testing
Subsonic Fixed Wing Project
Fundamental Aeronautics Program
19
Fully Coupled BLI Propulsor CFD Analysis Completed
• Problem: Enable Efficient Propulsion and Power Through a Collective 50%
Reduction in the Amount of Fuel Burned by Commercial Aircraft.
• Objective: Achieve Increased Aircraft Propulsive Efficiency and Reduced
Weight and Drag by Ingesting Large Amounts of Available Fuselage
Boundary Layer Air Flow and Embedded Propulsion Within the Airframe.
• Approach: UTCFD, Sculptor, I-Sight, DYNTECC and Other Computational
Tools Used to Design Integrated a BLI Inlet / Distortion-Tolerant Fan
Propulsor to Achieve Propulsion System Study Identified Aircraft Benefits (i.e.
Locally < 2% Reduced Fan Efficiency, Stability Margin).
• Significance: UTRC’s Results Support the Potential of Embedded BLI
Propulsors and Demonstrate New Tools for Designing Better (Optimized)
Propulsion Systems.
Subsonic Fixed Wing Project
Fundamental Aeronautics Program
Simultaneous Efficiency, Distortion Improvements
Fan Efficiency, η (%)
• Results: A First Ever Fully Coupled Unsteady (i.e. ~80M Grid Point, LargelyOptimized, Full Wheel) CFD Analysis Has Been Completed, Indicating That
the Local Propulsion System Aero Design Goals are Achievable.
NASA Inlet A Distortion
UTRC Parametric Inlets
UTRC Parametric Inlets (DYNTECC Model)
Circumferential Distortion, ∆PC/P (%)
Research team: Greg Tillman (PI), Aamir Shabbir, UTRC, Dave Arend, NASA COTR
20
Turbomachinery Aeroelastic Analysis
• Background: Future Hybrid Wing Body aircraft will use an Embedded Propulsion
System with Boundary Layer Ingestion to improve Fuel Burn. An embedded
propulsion system will lead to a persistent and severe inlet distortion reaching the
fan at all operating conditions, resulting in high dynamic stresses due to
aeroelastic forced response and the possibility of flutter.
• Approach: A new high-fidelity full-rotor aeroelastic analysis is being developed to
enable the computational modeling of a fan subjected to a distorted inlet flow. This
new capability allows an arbitrary inlet distortion to be specified with both
circumferential and radial variations of flow properties, together with prescribed
blade vibrations.
• Results: Substantial work has been done in the formulation and implementation
of an arbitrary inlet distortion in the Aeroelastic Analysis code TURBO-AE. A
representative fan configuration has been selected and a computational mesh of
sufficient resolution has been generated. An inlet distortion pattern representing a
boundary layer ingesting inlet has been prescribed. Simulations have been
performed with rigid- and vibrating-blade geometries subjected to clean and
distorted inlets.
• Significance: New aeroelastic analysis capability will ensure operability of fan in
embedded propulsion system of Hybrid Wing Body aircraft.
Subsonic Fixed Wing Project
Fundamental Aeronautics Program
Researcher: Dr. Gregory Herrick (RXS)
http://silentaircraft.org/
Contact: Milind Bakhle, [email protected], 216-433-6037
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Conceptual Integrated Inlet/Fan
Wind Tunnel Experiment
Test Section Porosity
Universal Propulsion
Simulator Drive Rig
Boundary Layer Ingesting Inlet
Raised Test
Section Floor
Boundary Layer
Bleed
Fast-Acting Variable
Area Nozzle
Distortion-Tolerant Fan Stage
• Rotating AIP Rake Array
• Distortion-Tolerant Fan Stage
• Rotating Fan Exit Rake Array
Subsonic Fixed Wing Project
Fundamental Aeronautics Program
Environmentally Responsive Aircraft Project
Integrated Systems Research Program
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Analysis Methods & Tools
Focus: Develop fundamental, high fidelity tools and methods for materials and computational fluid dynamics
modeling and advanced testing.
Goal: Enable reduction in TSEC through improved analysis and understanding of uncertainties.
Technical Content:
LES model for turbomachinery: Incorporate and validate LES turbulence model in turbomachinery flow solver
for more accurately predicting shear layer dominated turbomachinery flows - film cooling jets and unsteady flow
control devices.
Validation dataset: Conduct fundamental experiments to generate validation datasets of various flow control
concepts (e.g., vortex generators).
Luminescence based diagnostic: Develop and demonstrate a luminescence-based mapping of temperature &
damage fields for integrity/delamination failure of thermal and environmental barrier coatings.
Subsonic Fixed Wing Project
Fundamental Aeronautics Program
23
SFW-Sponsored SAA with AFRL Achieves Luminescence-Based Surface Temperature
Measurements During Exposure to Combustor Burner Flame at Williams International
• Problem: Accurately measure turbine component temperature
• Objective: Demonstrate that reliable thermographic phosphor
based temperature measurements to 1300ºC could be obtained for
TBC-coated specimens in aggressive combustion flame
environment.
TBC = thermal barrier coating
• Approach: Obtain luminescence-decay based temperature
measurements for specimens during exposure to highly radiant,
high gas velocity flame from Combustor Burner Rig Facility at
Williams International. Multi-institutional test team of NASA GRC,
ORNL, Metrolaser, and Williams International.
Combustor burner at Williams International.
Coating survives
substrate melting!
Luminescence emission spot entering hot zone,
observed through 456nm bandpass filter.
• Results: TBC surface temperatures reliably measured from 1100º
• Significance: Surmounted challenge of making measurements through
combustion flame and showed thermographic phosphor survived postcombustion environment. Results indicate high potential for successful
transfer to future engine testing.
Subsonic Fixed Wing Project
Fundamental Aeronautics Program
Test team: Jeffrey
No flame
Low Flame
High flame
0.01
PMT Signal (V)
to 1400ºC using YAG:Dy phosphor layer. Filtering out background
flame radiation successful. Probe geometries and phosphors
chosen for future engine tests.
0.1
RT
1161ºC
0.001
1347ºC
0.0001
1E-05
0
500
1000
1500
2000
2500
3000
3500
4000
Time (µs)
Luminescence decays faster as
temperature increases.
Eldridge (RHI) , Steve Allison (ORNL), & Tom Jenkins (Metrolaser)
24
Summary of Technical Challenges to
Reduce Thrust Specific Energy Consumption
1.
High Efficiency Small Gas Generator
• 1500 F hybrid disk
• High temperature seals
• Tip clearance/endwall loss mitigation
• Model based/distributed engine controls
2.
Hybrid Electric Propulsion
• Generators & motors:
• Cryo inverters:
• Cryocoolers:
• Total electric system:
• Batteries:
3.
Propulsion Airframe Integration
• Distortion tolerant fan design:
• Aeroelastic analysis capability:
4.
Analysis Methods & Tools
• Validation datasets
• Improved predictive and measurement capability
Subsonic Fixed Wing Project
Fundamental Aeronautics Program
Machines with 1/10th SOA weight & low AC loss
Weight of ½ SOA and ~1/10th SOA loss
Turbo-Brayton cooler at 1/5th SOA weight
Distribute ~50 MW in a stable, responsive grid
>~0.6 kW*h/kg at TRL9
<2% fan efficiency decrement
coupled inlet/fan stage w/ distortion
25