1

INVENT ―Tip-to-Tail‖

Energy/Engine/Power/Thermal

Modeling, Simulation, & Analysis (MS&A)Capabilities and Vision

Mitch Wolff, Ph.D.

Scientific Advisor for INVENT

AFRL/RZPE

Wright Patterson Air Force Base

5th Annual

Research Consortium for

Multidisciplinary System Design

Workshop

Boston, MA

29-30 June 2010

2

Introduction

Modern survivable military aircraft

• 3 to 5 times heat load of legacy aircraft

• Limited ability to reject heat to environment

• Increasing secondary power demands

– On demand peak power for flight controls

– On demand peak power for engine thrust actuation devices

• INCREASED COMPLEXITY (controls, # components, integration, power density, power transfer, …)

Cleared for Public Release , USAF AFRL/RZ, RZ09-0609, 8 Dec 09

Requires new design processes

3

Power & Thermal Management

RequirementsP

ow

er

& T

herm

al

Req

uir

em

en

ts

F-15C, D

F-15E

Active Denial

Laser Fighter

LRSII

Time Today

~~

F-16

Heat Sink: Fuel, Lube, Ram Air,

Fan Duct, Thermal Energy

Storage, Expendable?

Heat Sink: Fuel

Heat Sink: Ram Air

& Fuel

F-22

F-35 STOVL

F-35 CTOL, CV

LRSIII

kW

ELLA

MEA I

More Electric Aircraft Gen I

– Electric Engine Start

– Electric Primary Flight Control

– PTMS

Cleared for Public Release , USAF AFRL/RZ, RZ09-0609, 8 Dec 09

4

Challenges

• Modern / future aircraft are designed for optimal

subsystem mass & volume

– Limited range & endurance

– Vehicle operations impact due to thermal limitations

– Power compatibility issues for actuation & sensors

• Vehicle level system assessment and optimization

requires complex highly integrated models at a

Vehicle System level to design & verify

– Conventional ―cut & try‖ approach can add significant costs

and delays

– System-level hardware ground and flight demonstrations

are required to validate integrated modeling approaches

Cleared for Public Release , USAF AFRL/RZ, RZ09-0609, 8 Dec 09

Vehicle Design

Challenges

Analysis and

Optimization

Challenges

5

Energy Optimized Aircraft

(EOA)

• Must account for ―entire‖ energy

picture

• Multi-role military aircraft must have

flexibility to support emerging

capabilities– Trade between energy consumption and

flexibility (minimum complexity)

– Must provide provisions for growth by

establishing near-, mid-, and far-term

aircraft-level goals

Cleared for Public Release , USAF AFRL/RZ, RZ09-0609, 8 Dec 09

Definition EOA: an aircraft that is optimized for broad capabilities

while maximizing energy utilization (aircraft and ground support)

with the minimum complexity system architecture.

6

What ―Challenge‖?

Energy

Utilization

It’s all just

crazy talk…It’s

an ELEPHANT!!It’s a solid

material

problem!!

It’s a fluid

problem!!It’s a system

problem!!

There is

no heat

sink…

It’s a

thermophysics

problem??!!

Cleared for Public Release , USAF AFRL/RZ, RZ09-0609, 8 Dec 09

7

Benefits:

• Improved Operability and Readiness

• Increased range or endurance

• 2X hot day ground operation

• 4X combat support altitude operations

• 5X electrical power and cooling

• 50% reduced weight and volume

High Performance

Electric Actuation

System (HPEAS)

Robust Electrical

Power System (REPS)

Adaptive Power & Thermal

Management System

(APTMS)

―Energy Optimized Aircraft‖ via

Integrated Vehicle Energy Technology (INVENT)

“Integrated" Advanced Hybrid Electric Vehicle Systems:

• Maximize Overall System Energy Efficiency

• Minimize Thermal Management Challenges

• Optimize ‗On-Demand‘ , Duty-Cycle Based-Systems

• Reduce Risk by Real-Time Simulation, “Fly it before we build it”

Integrated (static/dynamic)

M&S with Hardware-in-the-

Loop Demonstration

Advanced

Engine Technology

Integration

GE Rolls-RoyceFighter Engine Team

Cleared for Public Release , USAF AFRL/RZ, RZ09-0609, 8 Dec 09

8

HP

CompFan

Comb

TU

RB

INE

Comb

Pump

Hot Returned

Fuel to Feed

Tank

Aircraft Heat

Loads…

Generators

Hydraulics

ECS

Fuel Pumps

Avionics

Etc.

Aircraft

Return

Fuel Air

Cooled

Heat

Exchanger

Aircraft Fuel System Thermal Management

Fuel

from

other

tanks

Q = mcpΔT; or Tfinal= Q/mcp + Tinitial

Q is the amount of heat to be managed by fuel

m is the mass of the heated FUEL in feed tank

cp is the specific heat capacity of fuel

ΔT is the temperature difference;

Energy Balance Result is Tfinal considering

Tinitial to be 120 deg F

8

Generic Aircraft Mission ProfileTMS Limits to Mission Growth

Mission Time

TM

S F

uel Tem

pera

ture Fuel Temperature

Limit

End of

Mission

For Official Use Only

• Fuel temperature (mission) limited by fuel-cooled electronics

Ground Idle Low Altitude Cruise

Cleared for Public Release , USAF AFRL/RZ, RZ09-0609, 8 Dec 09

9

Dynamic (Segment-Level) Balance

20 20.2 20.4 20.6 20.8 21 21.2 21.4 21.6 21.8 22-1

-0.5

0

0.5

1

1.5

2

2.5

3

Time (s)

Pow

er (p

u)

EPS Power Draw

Maximum Generator Power (Transient)

Maximum Generator Power (Average)

Actuator Power (Average)

Minimum Generator Power (Transient)

Representative Transient Power Profile

• Modern MEA architectures have drastically altered the dynamics of power flow on the electrical bus

• Peak-to-average power ratios may exceed 5-to-1 across 50 – 5000 ms

• Power electronic loads may produce regenerative power equal to peak power for durations of 20 – 200 ms

• Key loads with highly dynamic power requirements include radar and actuators

J. Wells, M. Amrhein, E. Walters, S. Iden, A. Page, P. Lamm, A. Matasso, ―Electrical Accumulator Unit for the Energy Optimized Aircraft,‖ SAE International Journal of Aerospace, 1(1):

pp. 1071-1077, 2008

Cleared for Public Release , USAF AFRL/RZ, RZ09-0609, 8 Dec 09

10

Energy Optimized Aircraft

M&S Vision

The

Need:

Near Mid Far

The

Solution:

Verified and ValidatedFull System,

Thermal Model

Cockpit Simulation –

Full Mission Capability

Advanced

Components

Integrated Vehicle Energy

Technology (INVENT) System

Integration Facility

M&S is Bridge from Science to FlightCleared for Public Release , USAF AFRL/RZ, RZ09-0609, 8 Dec 09

11

―Fly‖ Any Mission

+ MRIP (Modeling

Requirements &

Implementation

Plan)

―Mission‖ = 5 points

2007—after SAB Thermal Summer Study

• Only a few pre-defined missions are specified in requirements documents; used to design vehicle and all subsystems

• ―Design Point‖ and a few ―Off-Design Points‖ describe entire mission ( time-independent analysis)

• No impact on design/development/acquisition process—No cost or timeline reduction

Conceptual Design Preliminary Design Detailed Design T&E Acquire/Sustain

2010—March Status

• ―Fly‖ arbitrary missions—ENABLES virtual or real pilot-in-loop

• Entire mission is continuous in time, time-dialing: hours/minutes/seconds/sub-second for vehicle & all subsystems

• Industry-wide Concept/Preliminary/Detailed Design process documented in ―MRIP‖

• Improved design/development process + Initial hardware-in-loop test capability

Conceptual Design Preliminary Design Detailed Design T&E Acquire/Sustain

DARKER=more capability

INVENT ―Tip-to-Tail‖ MS&A-- Air Vehicle and Subsystems --

LIGHTER=less capability)*(Shading:

*

12

• ―Zero-D‖

Point Mass

• Equilibrium

• Zero-D to 3-D for

Systems + Subsystems

+ Components

• Statics + Dynamics

+ Control

2010—March Status

• Allows selection/connection of ―quasi-static,‖ linear, & dynamical mathematical models

• Significant improvements in ―dialable‖ fidelity—Explicit space and time dependence

• Integration and coupling of plant/controller dynamics and software ―code‖ development

2007—after SAB Thermal Summer Study

• Equilibrium (steady state) mathematical models and solutions only—No dynamics (no transients)

• No spatial or temporal resolution / no "dialability"—equations not time-dependent

• Processes and Cycles only—No ability to include Controls, Software

Statics—Equilibrium Models Linear Systems—Near Equilibrium Dynamical Systems—Dialable Dynamics

Statics—Equilibrium Models Linear Systems—Near Equilibrium Dynamical Systems—Dialable Dynamics

INVENT ―Tip-to-Tail‖ MS&A-- Models and Fidelity --

13

2007—after SAB Thermal Summer Study

• Coordination not collaboration - models integrated in one place

• Design iteration takes weeks - poor computational methods & speed

• Extremely Limited Connectivity

• Travel, telecon, e-mail, database/file sharing, proprietary data ―hiding‖

• Component, subsystem suppliers and integrator react to req‘t changes

• Component and subsystem design-point-optimization

• No hardware-in-loop testing

2010—March Status

• Collaborative MS&A with 100's of compliant component/subsystem models

• Design iteration in days—advanced fast computation & simulation

• Still limited connectivity, but less data restrictions

• Integrated co-simulation using COTS and custom MS&A tools

• Component, subsystem suppliers & integrator—interactive analysis

• Multi-disciplinary optimization of integrated, controlled dynamic

subsystems/systems

• Initial hardware-in-loop

Model 1

Model 2

.

.

.

Model n

MS&A

location

Air framers

SuppliersUniversities

ASC, AFMC

AF, DoDAFRL

Collaborative MS&A

Send models to

MS&A ―integrator‖

Participate in

integrated MS&A

Mail/E-mail/Telecon Geographically-Interactive MS&A Geo-Interactive MS&A + Hardware-in-Loop Test

Materials Part/Assembly Component Subsystem System Tip-to-TailSystem-of-

Systems

Mail/E-mail/Telecon Geographically-Interactive MS&A Geo-Interactive MS&A + Hardware-in-Loop Test

Materials Part/Assembly Component Subsystem System Tip-to-TailSystem-of-

Systems

INVENT ―Tip-to-Tail‖ MS&A-- Communication and Collaboration--

14

Requires M&S Interface Control and Specifications

Document (ICD) Process

Modeling Background

Computer Aided Design (CAD)

• Physical modeling to address form

fit in design process

• Universally accepted practice High Performance

Electric Actuation

System (HPEAS)

Robust Electrical

Power System (REPS)

Adaptive Power & Thermal

Management System

(APTMS)

ADVANCED

ENGINE TECHNOLOGY

INTEGRATION

More Electric Aircraft

• Integrated subsystems

• Increased complexity

• Establishes computer-model-based

design precedence

• Dynamic interactions not addressed• Increased dynamic interactions

15

SoI

SystemIntegration

Fundamental Sciences

Fundamental Sciences &

Science of Integration (SOI)

Ther

mal

Man

agem

ent

Elec

tro

chem

istr

y

Mec

han

ical

En

ergy

Co

nve

rsio

n

Pow

er E

lect

ron

ics

Ener

gy &

Po

wer

Sys

tem

s

270VDC

MAINBUS

BATTERY

PASSIVE COOL

ACTUATORP & CE

PASSIVE COOL

ACTUATORP & CE

PASSIVE COOL

ACTUATORP & CE

EMA

ESG EHA

IAP

Regen

Regen

Regen

270VDC

MAINBUS

BATTERY

PASSIVE COOL

ACTUATORP & CE

PASSIVE COOL

ACTUATORP & CE

PASSIVE COOL

ACTUATORP & CE

EMA

ESG EHA

IAP

Regen

Regen

Regen

SoIPow

er D

istr

ibu

tio

n

SystemIntegration

16

FundamentalSciences

Components

DeviceManagement

Platform

Subsystem(s)Management

SystemIntegration

Energy Management Landscape for

Energy/Power/Thermal Division

• Physics-based M&S for energy management

• 2-φ Heat Exchanger

• TES

• Vapor cycle component

• Electronics Cooling

• Coupled elect/ thermal

• E/A FTMS

• PTMS

• On-demand ACS/VCS

ADVENT/HEETE

INVENT

• HIL and system M&S

Ca

pa

bil

ity

• Heat exchangers

• TES

• Vapor cycle components

• Passives

- LHPs

- LRE

• Electronics

- FADEC

- Laser Components

- ICC

- SiC-based

• Actuators

• Energy Optimized Aircraft

• Transient 2-φheat transfer physics

• Non-equil heat transfer

• Theoretical thermo-dynamics

• 30-50kW multi-evap, 2-φsystem

• Electric laser system TM

FLTCs

System Optimization and Energy

Management Solution Space

System characteristic attributes will define basic research opportunities

17

Model IP and Documentation:Model Requirements & Implementation Plan (MRIP)

• Framework for model development

– Mission & Segment

– Interface definitions

– Losses, heat, …

– Interactions

• Defines fidelity & data stream requirements

• V&V requirements

• Open models with limited encryptions

• Software documentation requirements

• Standard for AF/industry model documentation

AF and industry have consensus to facilitate system-level M&S

and accommodate evolving capabilities and proprietary models

18

Tabular data limits scope of possible investigations

• Steady-state information (neglects transient response between states)

• Data generated by resources not available to system integrator

• One architecture/mission/platform

• Cannot address dynamic controls interactions

Math Layer

11

s1

2

1

Need for Time-Accurate Mathematical Models

Develop time-accurate mathematical models

Improves:

• Model reusability

• Variable fidelity options

• Reconfigurable

• Multiple architectures/missions/platforms

• Address controls interactions / on-demand systems

Historically: S-S tabular-based look-up

modelsGoal: Dynamic mathematical models

Cleared for Public Release , USAF AFRL/RZ, RZ09-0609, 8 Dec 09

Move away from steady-state tabular data to time-accurate

models to improve versatility and increase fidelity

19

Why dynamic versus quasi steady-

state and equilibrium approaches?

Hardware-in-the-Loop example

0 5 10 15 20 25 30 35 40 45 50 557700

7800

7900

8000

8100

8200

8300

8400

8500

Time (s)

LP

Sp

oo

l Sp

ee

d (

RP

M)

A

B

Step FunctionAssumption

LinearAssumption

Exponential Decay Assumption

vari

able

or

syst

em p

rop

erty

Actual System Response

time

20

M&S System IntegrationChallenge

8NP39-029

• Heat Loads

• Mission Params

• Bay Temps

• Shaft Speed

• Shaft Power

Mach Altitude

1x10-6 s1x10-7 s

Simulation Time Step Domain

Thrust

Altitude

Engine Transient Response

1.0 sec0.1 s0.01 s0.001 s1x10-4 s1x10-5 s

6-DOF Simulations

Mission Profile

HPEAS Transient Response

Aircraft Maneuver

Detailed Transient Analysis

RE

PS

HPEAS

Vehicle Electrical Simulation

APTMS

FT

MS

Propulsion

Prop/Power/ Thermal Analysis

Propulsion/ThermalSimulation

ElectricalDistributed

HeterogeneousSimulation (DHS)

VehicleDistributed

HeterogeneousSimulation (DHS)

Segment Level Mission-Level

Cleared for Public Release , USAF AFRL/RZ, RZ09-0609, 8 Dec 09

Orders of magnitude differences in required simulations rates

Two different model fidelities defined (segment / mission)

21

Mission

Analysis

Mission

Analysis

Regen

Regen

Regen

Power and Thermal M&S

Complexity and IntegrationL

eve

l o

f D

eta

il

Hig

h F

ide

lity:

Te

mp

ora

l an

d

Sp

atia

l R

eso

lutio

n

Lo

w F

ide

lity:

Lu

mp

ed

Pa

ram

ete

r

an

d S

tea

dy-S

tate

Physics Component Subsystem System

Regen

Regen

Regen

Regen

Regen

Regen

Design

Refinement

Reduced Order

Models

Level of Integration

Early

Trade

Studies

Temporal &

spatial

resolution

Segment

Analysis

Modeling over the entire design process will require sufficient fidelity to capture salient system characteristics

Physics

modeling

space

Boundary

and Source

Term

Definition

22

Example of

Thermal Modeling Tool Set

Tank Environmental Interface Fuel Tank

Air Properties

Heat ExchangerHeat Load

Fluid Loop

Ram Inlet

Turbine/Compressor

Splitter

Merge

EjectorWater Separator

Aspirator

Phase Change Material Bay

Cockpit

PipeDuct

+ + 𝑑

𝑑𝑡 ∫

Thermal Toolset

RecentDevelopment

RecentDevelopment

Goal – continued expansion

of the toolset

23

Future Vision

Component Tests &

Model Development

• Conduct dynamic system

integration R&D

• Integrated suite of

system level M&S tools

• Identify integration

challenges

Develop a capability to bridge

the gap from theory to flight

HPEAS

REPS

APTMS

Cleared for Public Release , USAF AFRL/RZ, RZ09-0609, 8 Dec 09

24

Existing Air Vehicle Development Timeline

Conceptual Design

Preliminary Design

Detailed Design T&E Acquire/Sustain

Conceptual +

Preliminary Design

Detailed Design + Hardware-in-Loop Test

& EvaluationFaster to Acquire/Sustain

Rapid Design/Engineering/Maturation

• Zero-D to 3-D + time ―dialable‖ fidelity

• Concurrent plant/control/software V&V

• Virtual/virtual & virtual/real integration

‒ Component, subsystem, system,

system-of-systems, warfighter

• Before hardware & hardware integration

Vision – to enable:

• Rapid technology insertion, risk reduction

• Broad-spectrum survivability, EW/DEW

• Projection and assessment of tip-to-tail

capabilities in warfighter virtualizations

Impact to development and acquisition -

Dramatic reduction in RDT&E cost & time

DoD + Supplier + Airframer Collaboration

• Inter-connected co-simulation

from/to/with government & industry

• Tie-in existing test facilities around U.S.

• People & proprietary data can ―stay at home‖

New Process & Timeline

INVENT ―Tip-to-Tail‖ MS&A-- 2014 Vision and Goals --

Integrated System Simulation Geographically

Distributed with Pilot & Hardware-in-the-Loop

AdvancedTechnology EngineModels/Hardware

Adaptable Thermal Management System

Models/Hardware

High Performance Electric

Actuator Models/Hardware

Air Vehicle Flight/Mission Models/Hardware

Robust Electric Power System

Models/Hardware

Reduction in Development

Time

25

Modeling and Simulation

• Challenges: Thermal M&S can no longer be performed while excluding the effects

coupled system interactions

What fidelity? Physics?

o Spatialo Temporal

Well-posed, well-understood boundary conditions?o Coupled system interfaceso Environmental influenceo Heat input requirements and heat sink characteristics

What validation? Hardware-in-the-loop

o Model-to-hardware validationo Hardware-to-model corrections for real-time HIL

Well-posed experiments and/or testing Flight test data availability

Proper metrics for “energy optimization”?

26

Summary

We are entering an exciting new era for the science and integration

of energy, power, and thermal components and systems

• New areas of science and engineering will need cultivating

– The ―Science-of-Integration‖ now has a broader implication

– Power and thermal component and system development will require fundamental

research emphasis (e.g. non-equilibrium physics & theoretical and experimental

thermodynamics)

– M&S development will require fundamental research emphasis (e.g. complex

system M&S, new approaches to V&V, advances in MDO/MDA)

– A clear vision and purpose within academia, industry, and DOD with sufficient

resources