NASA ULI INITIATIVEHybrid Electric Propulsion

Challenges and Opportunities

Dr. M. J. BenzakeinAeronautics and Space Engineering BoardSeptember 2019

NASA ULI PROGRAM:

Electric Propulsion: Challenges and Opportunities

Electric motor

Turbo-shaftand generator

One of the NASA strategic thrusts, as defined by NASA’s Aeronautics Implementation Plan, is the Transition to Low Carbon Propulsion

OSU NASA ULI PROGRAM plans to develop and demonstrate technologies for enabling hybrid turboelectric propulsion for commercial aircrafts.

Challenge 1 System IntegrationSuccess Criteria: Vehicle energy and CO2 >20% improvement over existing solutions

Challenge 2 Ultra-High Power Density Electric Machine and Power ElectronicsSuccess Criteria: Electric machines > 14 kW/kg, power electronics > 25 kW/kg, efficiency > 99%, bus voltage up to 2kV without partial discharge

Challenge 3 Energy StorageSuccess Criteria: Power density and reliability (desired 450 Wh/kg)

Challenge 4 Advanced Control of Onboard Electrical Power SystemsSuccess Criteria: System remains stable at 20% voltage sag and 200% step load change

Challenge 5 Research Infrastructure for More Electric AircraftsSuccess Criteria: Sub-system and component prototyping and testing at elevation – 2 kV, 1 MW, 20 kRPM drive tests

Research on thermal management system design is integrated in every aspectof the project.

OSU is leading a 5 year program of $10M

TEAM MEMBERS AND PROJECT ROLES

• The interactions and impact each system has on each other

• Total mass build up for each system and its effect on the aircraft

• Aircraft’s volume availability• Redundancy strategies for

each system architecture

System Integration

Based on regional jet (CRJ900)

Vehicle Arch.Oper. Environ.

Perf. Reqs.

Comp. Arch.Perf. Maps

Integration NeedsElectric Machine

Power Electronics

Thermal Management

Energy Storage

• Detailed design of integrated electric machine and power electronics package operating at 2 kV with power output of 1 MW

• Focus on mechanical stress, thermal management, and partial discharge

• Cell selection and pack architecture definition

• BMS and TMS design• Energy management,

reliability, cost studies

• Development of system-level thermal mgmt.. strategy – heat extraction from PT components and deposition in ram air

Pouch cells

170-260 Wh/kg

Cylindrical cells

240-270 Wh/kg

Pouch cells

300-400 Wh/kg

•Kokam (Lithium-polymer, 130 -265Wh/kg up to 50C, automotive / industrial application)

•Eagle Picher/Yardney (NMC, 125 –135Wh/kg, aerospace application)

•XALT Energy (NMC, 220Wh/kg)

•Panasonic/Sanyo/Samsung (NCR, 260Wh/kg, automotive application)

•LG (IMR, 240-260 Wh/kg, automotive application)

•Efest (IMR, 270Wh/kg)

Identify and Qualify Commercially

Available Batteries

CWRU and OSU are investigating the availability of High Energy Density Lithium ion

Cells, to understand their attributes in terms of flexibility (and shape conformability),

safety, reliability, energy density, life and thermal requirements.

Current available cells have a specific energy density ≈ 250Wh/kg at 2C with an annual

improvement of ≈8%.

Delivered and under testing

Procurement process

Objectives:

• Develop MW motor drives working with 2000 dc voltage in

low pressure and high temperature environment while

achieving a power density > 25 kW/kg

• Develop a system level control strategy for aircraft on

board power system to improve system stability.

Objectives:

Develop MW motor drives working with 2000 dc voltage in

low pressure and high temperature environment while

achieving a power density > 25 kW/kg

Develop a system level control strategy for aircraft on

board power system to improve system stability.

Power Electronics

Develop, build and test MW motors with

a specific power density > 14 kW/kg.

Electric Motors

Thermal ManagementThermal Management

Ground Demonstrator

Terrific Facility

On line since summer 2016

Incorporates altitude chamber

Ohio State faculty and students closely connected to

NASA on planning and operation

NEAT – NASA ELECTRIC AIRCRAFT

TEST BED

Distributed Hybrid Turbo Electric Architecture

Fans

Motors with integrated

Power electronics

PGDS Cables

ULI Energy and Propulsion Configuration

Gas Turbine Generator

(turboshaft)

Gas Turbine Generator (x2) – generates electrical energy via the burning of fuelBattery Pack (xN) – storage of energy provided by grid charging, during time between flightsPower Electronics (x8) – distribute power to motors from battery and generator, based on power splitMotor (x8) – directly coupled to fan blades to convert electrical energy into propulsive force

PGDS: Power Generation and Distribution System

Benefits of Future Technology

Baseline Aircraft(CRJ 900)

Next Generation Aircraft

Distributed Hybrid Turbo Electric

Fuel Burn

Reduct

ion a

t 600 n

mi

and t

ypic

al paylo

ad

8%

9%

6%*

Distributed Propulsion

Use of Hybrid Propulsion

BLI = Boundary Layers IngestionBR = Power split between Batteries and Turboshaft *Assumes 200 Wh/kg batteries used at rate of 30% of overall propulsive power during climb and 20% during cruise @ 600 nmi.

15% improvement to Next Gen (A220)

~5%

BLI / Optimized Power management

Climb Cruise LandingBR=30% BR=20% BR=0%

Going Forward

• Further optimization of aircraft energy management system

will minimize

Fuel consumption

Vehicle weight

Total capital cost

• Continued focus on power electronics, energy storage,

electric motors and thermal management need to continue

Hybrid Electric Aircraft Propulsion is becoming a reality

• Terrific program

• New technologies being developed that’s at the forefront of industry

• Gave us additional opportunities to lead a multitude of collaborative programs with industry and government

• Gave us recognition by Boeing, Airbus and propulsion companies (GE Aviation, Rolls-Royce, United Technologies Corporation), new cooperative programs.

ULI Initiative – Results and Reflections

• Great experience for faculty from different institutions to work together –impressive cooperation in using multiple resources to solve a problem. Positive work environment.

• Excellent exposure for students for multiple universities to work together as a team.

• Review process can be improved. We have eliminated long reviews with power points and made them more effective.

• More emphasis to address the outcome of this research working with industry. We are doing this.

Results and Reflections…cont.

Terrific initiative!! Should serve as a model for

future University-Government cooperation.