E2Flight Presentation: Concept Electric Flight Energy ...
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E2Flight Presentation: Concept Electric Flight Energy Efficient Hybrid Propulsion Concept for Twin Turboprop Aircraft
Georgi Atanasov DLR Institute of System Architectures in Aeronautics Hamburg
DLR.de • Chart 1 > Symposium E2Flight Presentation > Georgi Atanasov > 28.03.19
Introduction
DLR.de • Chart 2
The main goal of the presentation is to provide an overview on the possibilities to improve the performance of regional twin engine turboprop aircraft by using hybrid propulsion.
The initial discussion covers the basic hybrid concepts: • Parallel Hybrid Architecture • Series Hybrid Architecture
The general benefits and drawbacks of each are discussed and an estimate of the potential aircraft-level effect on fuel efficiency is given.
Further follows a discussion on a merged hybrid concept: • Combined Hybrid Architecture
which incorporates the philosophy of the two basic hybrid concepts to push the limit of the achievable fuel efficiency potential even further.
> Symposium E2Flight Presentation > Georgi Atanasov > 28.03.19
Propulsion Architectures for a Twin Turboprop
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Parallel hybrid propulsion:
• Propeller driven by gas turbine and e-motor + battery.
eMotor/Generator
Gas Turbine
Propeller
Battery
PC&D E-Power Control and Distribution
Gearbox
Mechanical Shaft
Electric Power Line
Conventional twin turboprop: • Propeller driven by gas turbine. • No power cross-feed.
Series hybrid propulsion:
• Propeller driven by e-motor • Gas turbine generates
E-power • Battery for power boost
Legend:
Improved propulsion off-design performance
Operation & Integration Flexibility
Weight & complexity increase
Weight & complexity increase
PC&D
PC&D
> Symposium E2Flight Presentation > Georgi Atanasov > 28.03.19
Off-Design Efficiency Improvement with Hybrid Propulsion
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Off-design electric power benefits: • -10% block fuel potential for <500nm missions (due to taxi & descent). • Less noise and emissions near airports. • Relaxed engine takeoff rating.
Regional Aircraft Mission Profile: 500nm
> Symposium E2Flight Presentation > Georgi Atanasov > 28.03.19
Pow
er O
utpu
t
Time
Fuel
(Ene
rgy)
Flo
w
Time
takeoff
climb
cruise
descent
approach & landing
taxi taxi
Electric Takeoff Boost
Electric Idle Segments
Hybrid A/C
Turboprop
Energy Saving Potential ~10%
Series Chain Operation Flexibility
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Decoupled RPM optimization for improved performance & more flexible energy management
Decoupled Power & Thrust
Mitigated One Engine Inoperative Case.
Half power but no prop loss Half thrust & prop windmilling but full power available
Optimal RPM Optimal RPM
Operational flexibility due to mechanical decoupling
PC&D
PC&D PC&D
> Symposium E2Flight Presentation > Georgi Atanasov > 28.03.19
Integration & Configuration Flexibility
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One main gas turbine for cruise: • Improved thermal efficiency
due to scaling effects
Solution supporting gas turbine • In case the main fails • for takeoff/climb boost
PC&D PC&D PC&D
Design specifics: • Main Gas Turbine
designed for efficiency • Supporting Gas Turbine
designed for min. weight / cycle cost
Challenge: • A bigger battery needed
due to diversion in case the gas turbine fails.
• Not a viable tradeoff
> Symposium E2Flight Presentation > Georgi Atanasov > 28.03.19
One Main Gas Turbine vs Two Gas Turbines
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Configuration Tradeoff
Benefit: ~10% eff. improvement
Penalty: Added mass of the supporting gas turbine
PC&D PC&D
A trend for gas turbines in the regional aircraft class and below observed in previous studies:
Gas
Tur
bine
l Eff
icie
ncy
Gas Turbine Power
~10% relative efficiency steps for each 2x power
P2 = 2 x P1
P1
P3 = 2 x P2
P4 = 2 x P3
> Symposium E2Flight Presentation > Georgi Atanasov > 28.03.19
Performance Comparison Estimate
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Reference: Twin Turboprop
Power Units (GT + Gearbox) ~5% from MTOM
Reference A/C
+12% Block Fuel Mass of Hybrid
Series
+7% Block Fuel Electric Losses
PC&D
Hybrid-Series
PC&D
Hybrid-Series 1 Main Gas Turbine
-10% Block Fuel Efficiency of 1 big gas turbine
+3% Block Fuel Mass of
Supporting Gas Turbine
-10% Block Fuel Hybrid Off-Design
Optimization
PC&D
Hybrid-Parallel
+3% Block Fuel Mass of Hybrid
Parallel
-7% BF
-4% Block Fuel Operation Flexibility • Component Sizing • RPM Optimization
Hybrid-Parallel and Hybrid-Series generally struggle to achieve double-digit block fuel improvement.
-2% BF
> Symposium E2Flight Presentation > Georgi Atanasov > 28.03.19
The shown estimates are based on knowledge from
internal projects.
+5% BF
Hybrid Combined Architecture Concept
DLR.de • Chart 9
Generator
E-Motor
One gas turbine in cruise driving two
propellers
50% power transferred in
parallel
50% power transferred in
series
Direct AC-Line:
• No power convertors
• Propeller RPM synchronized
E-Motor & Generator sized for 50% PCRUISE
~25% of PTAKEOFF
Supporting gas turbine: • takeoff/climb power • In case the main fails
Clutch. Coupled for: • Takeoff / Climb • Main gas turbine failure
PC&D Battery for idle power segments.
Clutch Only decoupled for: • Idle • Main turbine failure
> Symposium E2Flight Presentation > Georgi Atanasov > 28.03.19
Hybrid-Split Architecture Operation
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Design Point (Cruise) Takeoff / Climb Idle – Taxi / Descent
PC&D
• Main gas turbine drives both propellers.
• Supporting gas turbine turned off & decoupled by clutch.
• Battery turned off.
• Main gas provides power to both propellers.
• Supporting gas turbine provides power to one propeller (in parallel).
• Battery turned off.
• Both gas turbines turned off & decoupled.
• Battery powers both propellers.
PC&D PC&D PC&D
Worst Case Failure
• Gearbox is jammed – both propeller and main gas turbine cannot be used.
• Supporting gas turbine powers operating propeller mechanically (as in conventional turboprop).
• Battery turned off.
> Symposium E2Flight Presentation > Georgi Atanasov > 28.03.19
Hybrid-Split Architecture Performance
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Reference: Twin Turboprop
-10% Block Fuel Hybrid Off-Design
Optimisation
+5% Block Fuel Mass of Hybrid
Combined -10% Block Fuel
Efficiency of 1 big gas turbine
+2% Block Fuel Electric losses
due to 50% series power in cruise.
-12% BF PC&D
Hybrid Combined
+1% Block Fuel Drag from bigger
nacelles
Integrated Hybrid Combined
Reference A/C
Over 10% block fuel saving possible with hybrid combined architecture.
Power Units ~ 5% MTOM
> Symposium E2Flight Presentation > Georgi Atanasov > 28.03.19
The shown estimates are based on knowledge from
internal projects.
Conclusions
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It was shown that by making use of the advantages of both parallel and series hybrid concepts, the combined hybrid architecture is potentially able to achieve a double-digit block fuel benefit.
Main technological bricks of the hybrid combined concept:
• Off-design operation optimization.
• One main gas turbine instead of two in cruise.
Constraints of the hybrid combined concept:
• Regional and commuter class aircraft.
• Twin engine operation.
• Increased benefits on shorter missions. -20%
-15%
-10%
-5%
0%
5%
10%
Bloc
k Fu
el v
s Tw
in T
urbo
prop
Pot
entia
l
Hybrid Parallel
Hybrid Series
Hybrid Series 1 Main Gas
Turbine
Hybrid Combined
> Symposium E2Flight Presentation > Georgi Atanasov > 28.03.19
DLR.de • Chart 13
Thank you for your attention!
> Symposium E2Flight Presentation > Georgi Atanasov > 28.03.19