# Keynote presentation: Towards greener aircrafts: Multidisciplinary Design Optimization of hybrid electric propulsion system

Xavier Roboam

## ► To cite this version:

Xavier Roboam. Keynote presentation: Towards greener aircrafts: Multidisciplinary Design Optimization of hybrid electric propulsion system. CISTEM, Oct 2022, Tunis, Tunisia. [hal-04946362](https://hal-04946362v1)

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# Towards greener aircrafts: Multidisciplinary Design Optimization of hybrid electric propulsion system

October 27th 2022

HASTECS

<figure><img src="image_4.png" /></figure>

<figure><img src="image_5.png" /></figure>

Laplace

Xavier
Roboam
On behalf
of:

F. Accorinti (Phd Student), V. Ayel, Y. Bertin, M. Fenot, E. Videcoq, A. Zeaiter (Phd Student)

<figure><img src="image_6.png" /></figure>

<figure><img src="image_7.png" /></figure>

INSTITUT
CARNOT
CIRIMAT

P. Simon

M. Banda (Post Doc Student), J. P. Cambronne, P. Collin (Phd Student), S. Doutour, N. Erroui (Phd Student), G. Gateau, Y. Lefevre, J.F. Llibre, D. Malec, M. Miscevic, M. Pettes-Duler (Phd Student), X. Roboam, N. Roux, B. Sareni, M. Tognan (Post Doc Student), S. Touhami (Phd Student), C. Turpin

<figure><img src="image_8.png" /></figure>

<figure><img src="image_9.png" /></figure>
# Context: towards more electric greener aircraft

Before the advent of COVID19, air traffic doubled every 20 years.

22 Milliards de passagers.km/an estimés @2050

Actually ~3% of greenhouse gas world production due to aircrafts 'Flygskam' context: "a shame to take plane"

<figure><img src="image_10.png" /></figure>

<figure><img src="image_11.png" /></figure>

## CO2 Emissions:

### Scenario 3 (Waypoint 2050 report): "aggressive technology"

<figure><img src="image_12.png" /></figure>

## Focus areas

Disruptive new technologies: Hybrid-electric & full electric (H2) architectures

Ultra-efficient aerodynamic

Use of bio fuels (SAF)
<figure><img src="image_13.png" /></figure>

# The electric aircraft revolution is on going !

## Reduced/Zero emission propulsion system:

* Less noise,

* More precision and dynamics in control,

* Less maintenance,

* Safer architectures (Distributed electric propulsion),

* Increased efficiency leading to reduced fuel consumption,

<figure><img src="image_14.png" /></figure>
<figure><img src="image_15.png" /></figure>

Context: "weight is the enemy" !

<figure><img src="image_16.png" /><figcaption>✓ Fuel saving vs embedded Weight</figcaption></figure>

<figure><img src="image_17.png" /><figcaption>Case study: regional aircraft
(short range ~ 400 nm)</figcaption></figure>

<figure><img src="image_18.png" /><figcaption>➤ Snowball effect: +6% of fuel / ton of additional embedded systems</figcaption></figure>
* ✓ Engine benefits: design and operation may be revisited with power hybridization

<figure><img src="image_19.png" /><figcaption>Gas turbine</figcaption></figure>

* ✓ Aerodynamic benefits: several concepts

<figure><img src="image_20.png" /><figcaption>Up to -2.5%* fuel burn</figcaption></figure>

<figure><img src="image_21.png" /></figure>

<figure><img src="image_22.png" /><figcaption>< -13%* ?? Fuel burn</figcaption></figure>

* ✓ Energy benefits: turboshaft efficiency

$η_{GT}$ ~ 10% for thermal descent or taxi

$η_{GT}$ ~ 90% for electric descent or taxi

<figure><img src="image_23.png" /></figure>

<figure><img src="image_24.png" /></figure>

HASTECS

<figure><img src="image_25.png" /></figure>

<figure><img src="image_26.png" /></figure>

J. Thauvin
thesis

AIRBUS
$$PHP = 1 - \frac{moy(P_{sp})}{max (P_{sp})}$$

$$PHE = \frac{P_{max}}{E_{u}(stockage)}$$

The lower the PHP, (resp. PHE)
the "more challenging" the
hybridization in terms of power
(resp. energy)

Power
Hybridization in
aeronautics not so
simple !

<table><thead><tr><th rowspan="2"></th><th colspan="2">Cars</th><th colspan="2">Railway</th><th colspan="2">Ships</th><th>Aircraft</th></tr><tr><th>Urban Transp</th><th>High way</th><th>Local service</th><th>Urban Transp</th><th>Container</th><th>Ferry</th><th>Regional (200 nm)</th></tr></thead><tbody><tr><th>PHP (%)</th><td>94</td><td>74</td><td>65</td><td>91</td><td>43</td><td>63</td><td>32</td></tr><tr><th>PHE (mHz)</th><td>66</td><td>12</td><td>3</td><td>20</td><td>n/a</td><td>n/a</td><td>0.22</td></tr></tbody></table>

✓ Aircraft Hybridization is difficult in terms of energy

* Few intermittent, no braking recovery

* An energy-related quasi static mission

* Engine Downsizing: high power gas turbines more efficient

J. Thauvin, Exploring the design space for a hybrid-electric regional aircraft with multi-disciplinary design optimisation methods

PHD Thesis of Univ Toulouse & Airbus Oct 2018

<figure><img src="image_27.png" /></figure>

AIRBUS
<figure><img src="image_28.png" /></figure>

# Several electrified architectures

<figure><img src="image_29.png" /></figure>

**Turbo-electric** : propulsion by electric motors from unique thermal source involving turboshafts
driving electric generators to produce the whole electrical power.

<figure><img src="image_30.png" /></figure>

**Hybrid-electric** propulsion (series or parallel): system supplied by two different sources: electric
(batteries or fuel cells) and thermal through gas turbines).

<figure><img src="image_31.png" /></figure>

The All-electric propulsion: aircraft propelled by batteries or fuel cells.

SH

Series Hybrid

<figure><img src="image_32.png" /></figure>

PH

Parallel Hybrid

<figure><img src="image_33.png" /></figure>

SPPH

Series/Parallel Partial Hybrid

<figure><img src="image_34.png" /></figure>

AE

All Electric

<figure><img src="image_35.png" /></figure>

TE

Turboelectric

<figure><img src="image_36.png" /></figure>

PT

Partial Turboelectric

<figure><img src="image_37.png" /></figure>
<figure><img src="image_38.png" /></figure>

# Several electrified architectures

<figure><img src="image_39.png" /></figure>
<figure><img src="image_40.png" /></figure>

# Several electrified architectures

<figure><img src="image_41.png" /></figure>

<figure><img src="image_42.png" /><figcaption>VTOL/STOL
City Airbus</figcaption></figure>

<figure><img src="image_43.png" /><figcaption>Airbus E-Fan</figcaption></figure>

<figure><img src="image_44.png" /><figcaption>Siemens Extra 330 LE</figcaption></figure>

<figure><img src="image_45.png" /><figcaption>Nasa X-57 Maxwell</figcaption></figure>

<figure><img src="image_46.png" /><figcaption>Eviation Alice</figcaption></figure>

<figure><img src="image_47.png" /></figure>

<figure><img src="image_48.png" /><figcaption>Airbus E-Fan X
Rolls Royce/Siemens</figcaption></figure>

<figure><img src="image_49.png" /><figcaption>Bell NEXUS
Safran</figcaption></figure>

<figure><img src="image_50.png" /><figcaption>ZA10
Zunum Aero</figcaption></figure>

<figure><img src="image_51.png" /></figure>

<figure><img src="image_52.png" /><figcaption>Aurora Lightning Strike</figcaption></figure>

<figure><img src="image_53.png" /><figcaption>Dragon - Onera</figcaption></figure>

<figure><img src="image_54.png" /><figcaption>STARC-ABL NASA</figcaption></figure>
HASTECS

<figure><img src="image_55.png" /></figure>

Hybrid Aircraft
Academic research on Thermal & Electrical Components and Systems

<figure><img src="image_56.png" /></figure>

AIRBUS

Series Hybrid electric
Architecture
(regional, 70 seats)

<figure><img src="image_57.png" /></figure>

LEGEND

PROPELLER + GEARBOX

<figure><img src="image_58.png" /></figure>

E-MOTOR + COOLING

<figure><img src="image_59.png" /></figure>

CABLE

<figure><img src="image_60.png" /></figure>

DC/AC CONVERTER + COOLING

<figure><img src="image_61.png" /></figure>

ELECTRICAL POWER
DISTRIBUTION CENTER

<figure><img src="image_62.png" /></figure>

BATTERY/FUEL CELL

<figure><img src="image_63.png" /></figure>

AC/DC CONVERTER

<figure><img src="image_64.png" /></figure>

E-GENERATOR

<figure><img src="image_65.png" /></figure>

TURBOSHAFT

<figure><img src="image_66.png" /></figure>

<figure><img src="image_67.png" /></figure>

<figure><img src="image_68.png" /></figure>

<figure><img src="image_69.png" /></figure>

<figure><img src="image_70.png" /></figure>

<figure><img src="image_71.png" /></figure>
<figure><img src="image_72.png" /></figure>

# Multidisciplinary Design Optimization (MDO) of the hybrid-electric aircraft powertrain

A set of coupled sizing variables :

* Geometry (propeller, emotor)

* Mechanical (gearbox)

* Electromagnetic (emotor)

* Electrical (bus voltage)

* Source sizing (fuel cell, turboshaft)

* Energy management

<figure><img src="image_73.png" /></figure>
## Design of highly integrated power electronics with its cooling

A set of coupled sizing variables :

* Geometry (propeller, emotor)

* Mechanical (gearbox)

* Electromagnetic (emotor)

* Electrical (bus voltage)

* Source sizing (fuel cell, turboshaft)

* Energy management

<figure><img src="image_74.png" /></figure>
## Design of highly integrated power electronics with its cooling

<figure><img src="image_75.png" /></figure>
## Design of highly integrated power electronics with its cooling

<figure><img src="image_76.png" /><figcaption>Evaporator HTC(W/m²/°K)</figcaption></figure>

PHD Thesis Flavio Accorinti, 2020

<figure><img src="image_77.png" /></figure>

- Stability

- Reliability

- low mass

- Controlled temp

<figure><img src="image_78.png" /></figure>

Junction temperature <150°C!

HASTECS result
4.5 kW (of losses) /kg !

<figure><img src="image_79.png" /></figure>

<figure><img src="image_80.png" /></figure>

Laplace

INSTITUT P'

<figure><img src="image_81.png" /></figure>

*CPLIP: Capillary Pumped Loop for Integrated power

<figure><img src="image_82.png" /></figure>

Laplace

LABORATOIRE PLASMA ET
CONVERSION D'ÉNERGIE
## Design of highly integrated power electronics with its cooling

<figure><img src="image_83.png" /></figure>

PHD Thesis Najoua Erroui, 2019

PHD Thesis Flavio Accorinti, 2020

<figure><img src="image_84.png" /></figure>

Laplace

<figure><img src="image_85.png" /></figure>

* MW range ; η ~99% ; > 30kW/kg
# Multidisciplinary Design Optimization (MDO) of the hybrid-electric aircraft powertrain

A set of coupled sizing variables :

* Geometry (propeller, **emotor**)

* Mechanical (gearbox)

* Electromagnetic (**emotor**)

* Electrical (bus voltage)

* Source sizing (fuel cell, turboshaft)

* Energy management

<figure><img src="image_86.png" /></figure>
<figure><img src="image_87.png" /></figure>

## Design of highly integrated eMotor with its cooling

<figure><img src="image_88.png" /></figure>

Target: >10 kW/kg

### Several drivers to increase both specific power and efficiency

**To decrease electric machine (PMSM) mass**

<figure><img src="image_89.png" /></figure>

* Increase **peripheral speed** up to 200m/s with sleeve having Strength tensile > 1600MPa

* Increase **current densities**:

$J_{rms} > 25A/mm^2$ et $K_{rms} > 100 kA/m$ for internal cooling inside slots

* Increase **flux density in air gap**:

high temperature permanent magnets (SmCo or NdFeB): $Br(\text{SmCo}) = 1.16T$ for $Bm=0.9T$

* Increase **number of pole pairs**:

Halbach, $N_p > 10$

<figure><img src="image_90.png" /></figure>

<figure><img src="image_91.png" /></figure>

<figure><img src="image_92.png" /></figure>

<figure><img src="image_93.png" /></figure>

**To decrease cooling system mass**

<figure><img src="image_94.png" /></figure>

<figure><img src="image_95.png" /></figure>

Decrease losses

<figure><img src="image_96.png" /></figure>

<figure><img src="image_97.png" /></figure>

$\eta$

* decrease **Joule losses (DC and AC)**:

Twisted Litz wires

High filling coefficient

$R_{AC}/R_{DC} \sim 1$ for 400Hz @ 5kHz

<figure><img src="image_98.png" /></figure>

* Decrease **iron losses**:

- Use thin magnetic sheets (very thin sheets 100-200µm and future 50µm)

Design of winding with partial discharge tolerant insulation

<figure><img src="image_99.png" /></figure>

**And other drivers...**

<figure><img src="image_100.png" /></figure>
<figure><img src="image_101.png" /></figure>

# Multidisciplinary Design Optimization (MDO) of the hybrid-electric aircraft powertrain

<figure><img src="image_102.png" /></figure>

## Design of highly integrated eMotor with its cooling

### External cooling for stator & internal for rotor

**Cooling system:**

* ✓ Heat exchanger = nacelle

* ✓ Liquid cooling

<figure><img src="image_103.png" /></figure>

Direct cooling
inside slots

Necessary to
reach 10kW/kg

<figure><img src="image_104.png" /></figure>

<figure><img src="image_105.png" /></figure>

## Importance of thermal transient during flight mission

<figure><img src="image_106.png" /><figcaption>STATOR TEMPERATURE PROFILE (°C)</figcaption></figure>

<figure><img src="image_107.png" /></figure>

Thermal model
~60 nodes

<figure><img src="image_108.png" /></figure>

<figure><img src="image_109.png" /></figure>
# Multidisciplinary Design Optimization (MDO) of the hybrid-electric aircraft powertrain

<figure><img src="image_110.png" /></figure>

## Design of highly integrated eMotor with its cooling

### External cooling for stator & internal for rotor

Direct cooling inside slots

<figure><img src="image_111.png" /></figure>

### Cooling system:

* ✓ Heat exchanger = nacelle

* ✓ Liquid cooling

Coolant flow from
Heat Exchanger

Wind
ed

<figure><img src="image_112.png" /></figure>

## Importance of thermal transient during flight mission

<figure><img src="image_113.png" /><figcaption>STATOR TEMPERATURE PROFILE (°C)</figcaption></figure>

$\eta = 98.5 \%$

<figure><img src="image_114.png" /></figure>

### Effect of thermal transients

$\eta = 97.5 \%$

$P_{spe} = 7.5 \text{ kW/kg}$

<figure><img src="image_115.png" /></figure>

Steady state thermal optimization

Transient state thermal optimization

<figure><img src="image_116.png" /></figure>
<figure><img src="image_117.png" /></figure>

## Optimal design of eMotor with its cooling

<figure><img src="image_118.png" /></figure>
<figure><img src="image_119.png" /></figure>

## Optimal design of eMotor with its cooling

### Design

<figure><img src="image_120.png" /></figure>

### Performance

<figure><img src="image_121.png" /></figure>

<figure><img src="image_122.png" /><figcaption>Flight cycle</figcaption></figure>

### INPUT VARIABLES (in bold blue, 10 decision variables for optimization)

<table><tr><td>R<sub>alesage</sub></td><td>[m]</td><td>Bore radius of the electric motor</td></tr><tr><td>R<sub>Drotlm</sub></td><td>[%]</td><td>Rotor diameter/rotor length ratio</td></tr><tr><td>R<sub>gral</sub></td><td>[%]</td><td>Air gap thickness/ bore radius ratio</td></tr><tr><td>R<sub>hsral</sub></td><td>[%]</td><td>Slot height/ bore radius ratio</td></tr><tr><td>R<sub>pmral</sub></td><td>[%]</td><td>Magnet thickness/ bore radius ratio</td></tr><tr><td>τ<sub>magnet</sub></td><td>[%]</td><td>Pole pitch (=100%)</td></tr><tr><td>τ<sub>slot</sub></td><td>[%]</td><td>Slot pitch (=100% full pitch winding)</td></tr><tr><td>k<sub>carbon</sub></td><td>[-]</td><td>Carbon fiber constant for sleeve equation</td></tr><tr><td>p</td><td>[-]</td><td>Number of pole pairs</td></tr><tr><td>q</td><td>[-]</td><td>Number of phases</td></tr><tr><td>nepp</td><td>[-]</td><td>Number of slots per pole and per phase</td></tr><tr><td>N<sub>ce</sub></td><td>[-]</td><td>Number of conductors per slot</td></tr><tr><td>k<sub>fill</sub></td><td>[-]</td><td>Fill factor in the slot</td></tr><tr><td>J<sub>a</sub></td><td>[T]</td><td>Permanent magnet flux density</td></tr><tr><td>B<sub>yoke</sub></td><td>[T]</td><td>Stator yoke flux density</td></tr><tr><td>B<sub>teeth</sub></td><td>[T]</td><td>Stator teeth flux density</td></tr><tr><td>B<sub>yoke rotor</sub></td><td>[T]</td><td>Rotor yoke flux density</td></tr><tr><td>V<sub>uHVDC</sub></td><td>[V]</td><td>Ultra high voltage direct current</td></tr></table>

### OUTPUT VARIABLES

<table><tr><td>M<sub>motor</sub></td><td>[kg]</td><td>Electric motor mass</td></tr><tr><td>PF(t)</td><td>[-]</td><td>Power factor mission</td></tr><tr><td>m<sub>a</sub>(t)</td><td>[-]</td><td>Modulation depth mission</td></tr><tr><td>P<sub>JDC</sub>(t)</td><td>[W]</td><td>DC Joule losses</td></tr><tr><td>P<sub>Iron</sub>(t)</td><td>[W]</td><td>Iron losses</td></tr><tr><td>P<sub>R</sub>(t)</td><td>[W]</td><td>Friction losses</td></tr><tr><td>P<sub>Aero</sub>(t)</td><td>[W]</td><td>Aerodynamic losses</td></tr></table>
<figure><img src="image_123.png" /></figure>

## Optimal design of eMotor with its cooling

Objective function : e-Motor weight

$\vec{X}$: vector of decision variables (11)

<figure><img src="image_124.png" /></figure>
<figure><img src="image_125.png" /></figure>

## Optimal design of eMotor with its cooling

Objective function : e-Motor weight

$\vec{X}$: vector of decision variables (11)

<figure><img src="image_126.png" /></figure>
## ➤ MDO of the whole powertrain at aircraft level

Multidisciplinary model based on analytical or surrogate models (regression models) for facing complexity issue.

A set of sizing variables :

➤ Geometry (propeller, emotor)

➤ Mechanical (gearbox)

➤ Electromagnetic (emotor)

➤ Electrical (bus voltage)

➤ Source sizing (fuel cell, turboshaft)

➤ Energy management

<figure><img src="image_127.png" /></figure>

PHD Thesis Matthieu Pettes, 2021
<figure><img src="image_128.png" /></figure>

# Other surrogate models integrated in MDO

<figure><img src="image_129.png" /></figure>

## ➤ Gearbox, Gas turbine, Cables, Propeller

<figure><img src="image_130.png" /><figcaption>Gas turbine</figcaption></figure>

$$ \text{Parametric Value} = (\text{hp/RPM}_{\text{out}})^{0.75*} (\text{RPM}_{\text{in}}/\text{RPM}_{\text{out}})^{0.15} $$

<figure><img src="image_131.png" /><figcaption>Gearbox</figcaption></figure>

Surface response models

<figure><img src="image_132.png" /></figure>

### INPUT VARIABLES

Cable electric power

Power Factor

Number of phases

AC/DC voltage (depending on the cable)

### Cabling Data (Cu or Al)

<table><thead><tr><th>GAUGE</th><th>1</th><th>0</th><th>00</th></tr></thead><tbody><tr><td>K<sub>c</sub> [-]</td><td>11e-4</td><td>8,4e-4</td><td>6,0e-4</td></tr><tr><td>M<sub>lin</sub> [g/m]</td><td>470</td><td>600</td><td>750</td></tr><tr><td>R<sub>lin</sub> [Ω/m]</td><td>0,5e-3</td><td>0,4e-3</td><td>0,31e-3</td></tr><tr><td>T<sub>cable max</sub> [°C]</td><td>220</td><td>220</td><td>220</td></tr></tbody></table>

<figure><img src="image_133.png" /></figure>

### OUTPUT VARIABLES

Cable efficiency

Cable warming

Voltage drop

Cable mass

<figure><img src="image_134.png" /><figcaption>Cables</figcaption></figure>

<figure><img src="image_135.png" /><figcaption>Propeller</figcaption></figure>

$$ P_{shaft} = \frac{1}{2 \cdot k_{effd}} \cdot \left( V_{A/C} \cdot T_{A/C} + \sqrt{V_{A/C}^2 \cdot T_{A/C}^2 + \frac{2 \cdot T_{A/C}^3}{\rho_{air} \cdot \frac{\pi}{4} \cdot D_{prop}^2}} \right) $$

<figure><img src="image_136.png" /></figure>

Analytical & scaling models

$$ M_{prop} = M^{ref}_{prop} \times \left( \frac{D_{prop}}{D^{ref}_{prop}} \right)^2 $$

<figure><img src="image_137.png" /></figure>

Laplace

LABORATOIRE PLASMA ET
CONVERSION D'ÉNERGIE
# Other surrogate models integrated in MDO

<figure><img src="image_138.png" /></figure>

## Road map on aux electrical sources: Batteries or Fuel Cells (FC) ?

<figure><img src="image_139.png" /><figcaption>Power profile mission</figcaption></figure>

A promising device !

<figure><img src="image_140.png" /></figure>

<figure><img src="image_141.png" /></figure>

<figure><img src="image_142.png" /></figure>

Laplace

<figure><img src="image_143.png" /><figcaption>H₂ liq storage</figcaption></figure>

<figure><img src="image_144.png" /><figcaption>FC System</figcaption></figure>

<figure><img src="image_145.png" /></figure>

<figure><img src="image_146.png" /><figcaption>Batteries</figcaption></figure>

Power oriented

Energy oriented

<table><thead><tr><th>Specific energy e<sub>m</sub></th><th></th><th>LTO / TNO<sup>1,4</sup></th><th>NMC Solid State<sup>3</sup></th><th>FC System (LH<sub>2</sub>)</th></tr></thead><tbody><tr><td rowspan="2">Perspectives (5 – 10 years)</td><td>Cell level</td><td>~ 180 – 200 Wh/kg</td><td>~ 650 Wh/kg</td><td>~ 1 kW/kg</td></tr><tr><td>System level</td><td>~ 100 Wh/kg</td><td>~ 325 Wh/kg</td><td>~ 560 Wh/kg</td></tr></tbody></table>

<figure><img src="image_147.png" /></figure>

INSTITUT
CARNOT

CIRIMAT

<figure><img src="image_148.png" /></figure>
<figure><img src="image_149.png" /><figcaption>➤ Snowball effect: higher device weights cause higher thrust needs with environment couplings => linearization thrust vs MTOW</figcaption></figure>

<figure><img src="image_150.png" /></figure>

<figure><img src="image_151.png" /></figure>
<figure><img src="image_152.png" /></figure>

<figure><img src="image_153.png" /></figure>

► Snowball effect: higher device masses cause higher thrust needs with environment couplings

<figure><img src="image_154.png" /></figure>

<figure><img src="image_155.png" /></figure>

Looped model with a reference thrust of a 20T MTOW

<figure><img src="image_156.png" /></figure>

Assumption checked

<figure><img src="image_157.png" /></figure>

AIRBUS

<figure><img src="image_158.png" /></figure>

Laplace

<figure><img src="image_159.png" /></figure>

J. Thauvin
thesis

<figure><img src="image_160.png" /></figure>

Snowball
effect!

Adimensional time

TAXI
OUT

TAKE
-OFF

CLIMB

CRUISE

DESCENT

LANDING

TAXI
IN
<figure><img src="image_161.png" /></figure>

<figure><img src="image_162.png" /></figure>

# MDO Formulations

<figure><img src="image_163.png" /></figure>

## 3 optimisation formulation:

<figure><img src="image_164.png" /></figure>

1. e-Motor mass *local*

<figure><img src="image_165.png" /></figure>

2. Powertrain mass *global*

<figure><img src="image_166.png" /></figure>

3. Fuel Burn *global*

<figure><img src="image_167.png" /></figure>
<figure><img src="image_168.png" /></figure>

MDO formulations

<figure><img src="image_169.png" /></figure>

14 decision variables

3 optimisation formulation:

<figure><img src="image_170.png" /></figure>

e-Motor mass local

<figure><img src="image_171.png" /></figure>

Powertrain mass global

<figure><img src="image_172.png" /></figure>

Fuel Burn global

<figure><img src="image_173.png" /></figure>

<figure><img src="image_174.png" /></figure>

Energy Management
System

<figure><img src="image_175.png" /></figure>

<figure><img src="image_176.png" /></figure>
<figure><img src="image_177.png" /></figure>

## MDO Formulations

14 decision variables for fuel burn optimization with "a light hybridization scenario" of EMS

<table><thead><tr><th>Decision Variables</th><th>Name of variables</th><th>Lower bound</th><th>Upper bound</th></tr></thead><tbody><tr><td>RThrust</td><td>Thrust ratio due to snowball effect</td><td>1</td><td>1.26</td></tr><tr><td>Dprop siz [m]</td><td>Propeller diameter</td><td>2</td><td>5</td></tr><tr><td>Rgbox [-]</td><td>Gearbox ratio</td><td>1</td><td>20</td></tr><tr><td>VuHVDC [V]</td><td>Ultra-high direct current voltage</td><td>540</td><td>2040</td></tr><tr><td>Ralesage [m]</td><td>Inner radius of the stator</td><td>0.05</td><td>0.25</td></tr><tr><td>Rdrot lm [%]</td><td>Ratio between rotor diameter and active length</td><td>50</td><td>125</td></tr><tr><td>Rhsral [%]</td><td>Ratio between stator slot and inner radius</td><td>10</td><td>150</td></tr><tr><td>Rgral [%]</td><td>Ratio between the air gap thickness and the inner radius of the stator</td><td>1</td><td>10</td></tr><tr><td>Rpmral [%]</td><td>Ratio between the magnet thickness and the inner radius of the stator</td><td>5</td><td>50</td></tr><tr><td>Byoke max [T]</td><td>Maximum yoke flux density</td><td>1</td><td>1.53</td></tr><tr><td>Bteeth max [T]</td><td>Maximum teeth flux density</td><td>1</td><td>1.53</td></tr><tr><td>Nce [-]</td><td>Number of conductors per slot</td><td>1</td><td>4</td></tr><tr><td>nepp [-]</td><td>Number of slots per poles and per phases</td><td>1</td><td>3</td></tr><tr><td>p [-]</td><td>Number of pole pairs</td><td>1</td><td>7</td></tr></tbody></table>

<table><tr><td>Optimizer used</td><td>CLEARING</td></tr><tr><td>Number of runs</td><td>~200</td></tr><tr><td>Duration</td><td>7 days</td></tr></table>

### 15 Constraints

*emotor constraints*

*emotor cooling constraints*

*partial discharges constraints*

$$D_{prop siz} \geq D_{prop check}$$

$$MTOW_{new} \leq MTOW_{ref} + 6T$$

<figure><img src="image_178.png" /></figure>

$$RThrust \geq \frac{MTOW_{ref}}{MTOW_{new}} \text{ Snowball effect}$$

MDO CPU time
(standard computer)
~ 7 days with clearing

<figure><img src="image_179.png" /></figure>
<figure><img src="image_180.png" /></figure>

## Some results of the 3 MDO formulations

<figure><img src="image_181.png" /></figure>

<figure><img src="image_182.png" /></figure>

<figure><img src="image_183.png" /></figure>

<figure><img src="image_184.png" /></figure>

HVDC bus, another strong coupling

<figure><img src="image_185.png" /></figure>

<figure><img src="image_186.png" /></figure>

Powertrain efficiency (%)
Propeller + gearbox + eMotor + inverter

<figure><img src="image_187.png" /></figure>

A typical and unexpected systemic coupling: propeller oversizing to increase powertrain efficiency

<figure><img src="image_188.png" /></figure>
➤ Conclusion: hybrid aircraft with heavier powertrain and potentially "greener" especially cumulating energy gains with aerodynamic benefits due to distributed electric propulsion

<figure><img src="image_189.png" /></figure>

<figure><img src="image_190.png" /></figure>
* Prospect: the actual breakthrough may be the ZeroE-H2 : with HASTECS models and using same MDO process, the MTOW of a ZeroE H2 should be +25% heavier than an optimized full thermal regional aircraft

## Rough assessment of a Full Hydrogen Aircraft with liquid H2 storage

<table><caption>Mass distribution of the powertrain (1 pod) [kg]</caption><thead><tr><th></th><th>2025 target</th><th>2035 target</th></tr></thead><tbody><tr><td colspan="3"><strong>Fuel cell – Liquid H2</strong></td></tr><tr><td>Specific power (FC + BoP*)</td><td>1 kW/kg</td><td>1,3 kW/kg</td></tr><tr><td>LH2 Compactness</td><td>20%</td><td>25%</td></tr></tbody></table>

<figure><img src="image_191.png" /></figure>

When thinking of cryogenic H2 @20°K why not mutualizing with superconductor devices ?
CISTEM

CONFÉRENCE INTERNATIONALE EN SCIENCES
ET TECHNOLOGIES ÉLÉCTRIQUES AU MAGHREB

IEEE INTERNATIONAL CONFERENCE ON ELECTRICAL SCIENCES AND TECHNOLOGIES IN MAGHREB

<figure><img src="image_192.png" /></figure>

Tunis, TUNISIA Oct 26-28, 2022

4TH

# Towards greener aircrafts: Multidisciplinary Design Optimization of hybrid electric propulsion system

## QUESTIONS ?

HASTECS

<figure><img src="image_193.png" /></figure>

Laplace

M. Banda (Post Doc Student), J. P. Cambronne, P. Collin (Phd Student), S. Dutour, N. Erroui (Phd Student), G. Gateau, Y. Lefevre, J.F. Llibre, D. Malec, M. Miscevic, M. Pettes-Duler (Phd Student), X. Roboam, N. Roux, B. Sareni, M. Tognan (Post Doc Student), S. Touhami (Phd Student), C. Turpin

Xavier
Roboam

au nom de :

<figure><img src="image_194.png" /></figure>

Université
de Toulouse

HASTECS

<figure><img src="image_195.png" /></figure>

The Book

HASTECS: Hybrid Aircraft: reSearch on Thermal and Electric Components and Systems

https://hal-univ-tlse3.archives-ouvertes.fr/hal-03407214

<figure><img src="image_196.png" /></figure>

Clean Sky2

This project has received funding from the [European Union's Horizon 2020 (cleansky 2 JTI)](https://ec.europa.eu/horizon2020) research and innovation programme, 2014-2024] under grant agreement No 715483