Design Trade Studies for Turbo- electric Propulsive ... · savings at the vehicular level. The theoretical benefit of wake filling has been derived in numerous analytical and numerical

ISABE-2019-24141 1

ISABE 2019

Design Trade Studies for Turbo-electric Propulsive Fuselage Integration

Florian Troeltsch, Julian Bijewitz and Arne Seitz

[email protected]

Bauhaus Luftfahrt e.V. Visionary Aircraft Concepts Taufkirchen, Germany

ABSTRACT

The present paper discusses intermediate results from activities performed within a

European Commission funded collaborative research project CENTRELINE (“ConcEpt

validatioN sTudy foR fusElage wakefilLIng propulsioN intEgration”). This project

focuses on demonstrating the proof-of-concept for a ground-breaking approach to

synergistic propulsion-airframe integration, the so-called Propulsive Fuselage Concept.

Key feature of the investigated configuration is a turbo-electrically powered propulsor

encircling the aft-fuselage, dedicated to the purpose of fuselage wake-filling. Apart from

discussing the approach towards processing and integration of specialized, high-fidelity

data in the overall system sizing framework, a series of aircraft-integrated parametric

trade studies and sensitivity analyses are presented suitable for the derivation of important

trends and characteristics. The optimisation of main power plant cooling air dependant

on the fuselage fan operating strategy and improvement of the fuselage fan propulsor

shaping show the potential for large efficiency gains.

Keywords: Boundary Layer Ingestion, Wake Filling, Propulsion System Integration,

Propulsive Fuselage

2 ISABE-2019-24141

NOMENCLATURE

APD Aircraft Preliminary Design

BHL Bauhaus Luftfahrt e.V.

BLI Boundary Layer Ingestion

CAD Computer-aided design

CAS Calibrated Air Speed

CENTRELINE ConcEpt validatioN sTudy foR

fusElage wake-filLIng propulsioN

integration

CFD

DES

Computational Fluid Dynamics

Design

EC European Commission

FF Fuselage Fan

FPR Fan Pressure Ratio of Fuselage Fan

FUS Fuselage

GEN Generator

GTF Geared Turbo Fan

HPT High Pressure Turbine

HTP Horizontal Tail Plane

ISA International Standard Atmosphere

LHS Latin Hypercube Sampling

LPT Low Pressure Turbine

LTT Low-Turbulence Tunnel

MainPPS Main Power Plant

MTOW Maximum Takeoff Weight

MTU MTU Aero Engines AG

NPF Net Propulsive Force

NMI Nautical Miles

OEW Operating Empty Weight

OJF Open Jet Facility

PAX Passengers

PFC Propulsive Fuselage Concept

PPS Propulsion System

PT Power Turbine

RANS Reynolds-Averaged Navier-Stokes

REQ required

SAR Specific Air Range

SLS Sea Level Static

TLAR Top Level Aircraft Requirement

TU Delft Technical University Delft

UCAM University of Cambridge

VTP Vertical Tail Plane

WUT Warsaw University of Technology

Symbols

𝐴𝑙𝑡 Altitude

𝐷𝑃𝐹𝐶,𝑏𝑎𝑟𝑒 Drag of bare PFC configuration

𝑑𝑇𝐼𝑆𝐴 ISA deviation

𝐹 Force

𝐹𝑁 Net thrust

ℎ Height

𝐿 Length

𝑀𝑎 Mach Number

𝑁 Rotation speed

𝑝2 𝑝0⁄ Intake freestream total pressure

recovery ratio

𝑃 Power

TROELTSCH ET AL. ISABE-2019-24141 3

𝑤2 Engine inlet mass flow

𝑤25 HPC inlet mass flow

𝑤𝑐 HPT cooling air mass flow

𝑤𝐹𝑢𝑒𝑙 Fuel mass flow

1.0 INTRODUCTION

Reducing the environmental impact of air travel is key in ensuring long-term

sustainability of aviation. A series of challenging emission reduction targets have been

declared by the European Commission (EC) through Flightpath 2050 [1] and the ACARE

Strategic Research and Innovation Agenda [2], as well as by NASA with the N+ goals

[3]. As generally acknowledged, reaching these ambitious target settings is not feasible

by means of evolutionary improvement of the existing systems. The exploration of

breakthrough technological advancements is necessary. In the field of propulsion and

power, great potentials in terms of overall vehicular propulsive efficiency improvement

may be expected from airframe wake-filling through the synergistic integration of

Boundary Layer Ingesting (BLI) propulsor technology. Different from the thrust

generation intrinsic to today’s propulsion systems installed in free stream air, the wake

filling principle allows for reduced excess velocities in the propulsive jet, thereby yielding

reduced kinetic energy losses in the aircraft wake, ultimately leading to propulsive power

savings at the vehicular level.

The theoretical benefit of wake filling has been derived in numerous analytical and

numerical studies using various levels of model fidelity, cf. e.g. [5], [6], [7] and [8]. Initial

efforts to experimentally confirm these beneficial effects of wake ingestion have been

conducted by means of low-speed wind tunnel test campaigns of generic bodies e.g. by

ONERA [9], by TU Delft [10], and, by MIT for the D8 configuration (cf. [11] and [12]).

The EC-funded Horizon 2020 collaborative project CENTRELINE (“ConcEpt validatioN

sTudy foR fusElage wake-filLIng propulsioN intEgration”) aims at demonstrating the

proof of concept and performing an initial experimental validation for a particularly

promising concept for airframe wake-filling, the so-called Propulsive Fuselage Concept

(PFC) [4]. The concept features a turbo-electrically driven propulsive device integrated

in the very aft-section of the fuselage (see Figure 1), dedicated to the purpose of fuselage

wake-filling, i.e. the localized ingestion and re-energization of the viscosity-induced low-

momentum wake flow of the wetted body via BLI.

Figure 1: Layout of Propulsive Fuselage Concept studied in CENTRELINE

featuring turbo-electric drive train [4]

An initial multidisciplinary investigation of the PFC focusing primarily on a purely gas

turbine based drive train was conducted as part of the EC-funded FP7 research project

“Distributed Propulsion and Ultra-high By-Pass Rotor Study at Aircraft Level”

(DisPURSAL). Focusing on a medium-to-long range, wide-body application with 4800

nm design range, a nominal 9% fuel burn reduction was predicted relative to an equally

advanced twin-engine reference aircraft [13]. Beyond a mechanically driven Fuselage

Fan (FF) alternative options based on electrified drive train elements have been proposed

[14-21] that ease on-board power transmission and help alleviating the aero-structural

complexity associated with a mechanical fuselage propulsor drive.

Generator off-takes from advanced GTF power plants

Electrically drivenfuselage propulsor

Electric power transmission

4 ISABE-2019-24141

Constituted by the partners Airbus, ARTTIC, Bauhaus Luftfahrt e.V. (BHL)

(Coordinator), Chalmers Tekniska Hoegskola, MTU Aero Engines, Warsaw University

of Technology (WUT), Siemens, Delft University of Technology (TU Delft) and the

University of Cambridge (UCAM), the CENTRELINE consortium tackles the main

challenges associated with efficient PFC aircraft design [4], i.e.:

the obtaining of a thorough understanding of the aerodynamic effects of

fuselage wake-filling propulsion integration;

a synergistic aerostructural design integration of the BLI propulsor;

a best and balanced architecture and design for the fuselage fan turbo-electric

drive train; and,

the multi-disciplinary systems design integration and optimisation at aircraft

level.

Based on intermediate results from the ongoing design and analysis activities in the

project, this paper presents and discusses the results of trade studies at the propulsion

system and aircraft level that are necessary in order to identify a best and balanced PFC

aircraft design.

2.0 MULTI-DISCIPLINARY DESIGN INTEGRATION

The foundation of the system-level design and performance studies presented in this paper

is formed by the multi-disciplinary, multi-partner collaborative research conducted within

the CENTRELINE project. This section of the present paper provides an overview of the

roles, interfacing and data handling process between the project partners. Subsequently,

the strategy implemented for the propagation of the multi-level, multi-disciplinary design

and performance information to the level aircraft sizing and operational assessment is

introduced.

2.1 Partner interfacing and information flow In order to appropriately tackle the multi-disciplinary challenges of PFC aircraft design

the scope of research in CENTRELINE includes activities at different levels of detail [4],

i.e.

system-level design definition and optimisation studies;

high-end and high-fidelity numerical analyses of key aspects of the disciplinary

design, including aerodynamics, structural design [22] as well as the architecture

and main components of the turbo-electric propulsion and power system [23];

and,

aerodynamic testing of the overall configuration in the Open Jet Facility (OJF)

and Low-Turbulence Tunnel (LTT) facilities at TU Delft [24] as well as BLI

propulsor testing on the low-speed fan rig at UCAM [25].

For a consistent handling of multi-level and multi-disciplinary sets of design and

operational parameters, ranging from the level of aircraft conceptual design definition to

the level of component detailed design specification, efficient infrastructural measures,

conventions and processes were established [26] including the versioning and exchange

of information via a secure Git repository. Unified system definition and performance

book-keeping standards were defined [27], that follow the requirements stated by the

MIDAP Study Group [28], and thus, allow a rigorous benchmarking of the PFC against

conventional aircraft without BLI propulsion. The roles of the individual partners within

the collaborative, multi-disciplinary PFC pre-design exercise are discussed in the

following. Therefore, key tasks and the basic flow of design information are visualised in

Figure 2.


Figure 2: Overview of interfacing between disciplines and project partners including basic

information flow

The multi-partner, multi-disciplinary workflow was initiated based on an initial target

design for the PFC aircraft through which basic requirements and performance target

settings for key aircraft components and subsystems had been defined in the very early

phase of the project [4]. As can be seen in Figure 2, together with the aero-validation

testing, the PFC aerodynamic analysis effort is shared by TU Delft and UCAM, with TU

Delft in charge of the overall aircraft simulation and testing [29], and, UCAM performing

the fuselage fan aerodynamic design, simulation and testing [30]. While the overall

configuration aerodynamic simulation approximates the BLI propulsor using an actuator

disk model, the 3D rotor and stator designs are fully taken into account within the fuselage

fan aerodynamic analysis. The overall configuration aerodynamic simulation provides the

fuselage fan inflow conditions and distortion patterns for the fan aerodynamics. The

resultant fan aerodynamic design characteristics are fed back to the overall configuration

aerodynamic simulation in order to refine and tailor the actuator disc model. BHL

performs the fuselage fan propulsion system multidisciplinary conceptualisation. The

aero-structural design and analysis of key parts of the PFC airframe is conducted by WUT

[31]. Siemens in cooperation with BHL defined the turbo electric architecture, for which

Siemens performs the pre-design of the turbo-electric power train components. Chalmers

is in charge of the conceptual design and performance analysis of the main power plants

[32] and MTU is responsible for the integration of the turbo-electric power generators

into the main engines [33]. The multi-disciplinary design and analysis information is

hosted on the central Git repository with a continuous knowledge integration from the

detailed disciplinary investigations at the overall design level being performed by BHL.

PFC aircraft noise is assessed by Chalmers, with aerodynamic input for the fuselage fan

provided by from UCAM. The CAD modelling task of the aircraft is performed by WUT

in cooperation with Airbus.

2.2 System-level knowledge integration The knowledge on PFC aircraft design is incrementally refined during the CENTRELINE

project involving multiple levels of modelling fidelity. Incremental results from the

various detailed design and analysis tasks need to be evaluated at aircraft-level in a

continuous manner in order to provide adequate design guidance from an overall system

optimality perspective. Therefore, a rapid-responding aircraft-level sizing and

optimisation setup is required featuring

robust parametric sensitivity for key design parameters from all relevant system

components and disciplines;

flexibility and extensibility in the parametric interfacing between the various

design aspects; and,

the capability of zooming by a quick inter-changeability of disciplinary models.

GIT SERVER

Performance characteristics of main

engines: Chalmers

Fuselage fan design and performance

characteristics: BHL

Characteristics of turbo electric power train components:

Siemens

Fan 3D aerodynamic design: UCAM

Overall configuration aerodynamics: TU Delft

Aero-structural design incl. weight estimation:

WUT

Fa

n p

erfo

rma

nce

ma

p,

de

taile

d fa

n g

eo

me

try

Flo

wp

ath

ge

om

etry

, pe

rf. cha

racte

ristics

Inflow properties, flow field

Design and performance data

Design and performance data

Tabulated aerodynamic data / surrogate models

Parametric mass information

CAD modelling: Airbus/WUT

Aircraft-integrated sizing: BHL

Generator integration: MTU

Aero-shape data Fuselage/nacelle aero-shaping: BHL/TU Delft

Noise evaluation: Chalmers

turbo electric architecture definition: BHL/Siemens

Fan aero

dyn

amic

characteristics

Design and performance decks

6 ISABE-2019-24141

Given the nature of the design problem at hand, a fully-coupled multi-disciplinary, multi-

partner design optimisation process featuring the direct execution of the specialized

disciplinary models seems widely impractical. Instead, decomposition of the overall

system design and optimisation problem was performed. The individual disciplinary and

component design optimisation subtasks were decoupled from the aircraft level, by

imposing local objectives and constraints directly derived from the aircraft level design

and optimisation task. This approach, commonly known as the “Bi-Level Integrated

System Synthesis (BLISS) technique [34, 35], allows the handling of complex design

optimisation problems based on a relatively small number of top-level variables

effectively shared by the various subtasks. The optimum design solution at system level

is guided by the derivatives of subtask responses and local design settings with regard to

the shared global parameters.

For the interfacing between the system-level design optimisation and the local design

optimisation activities, in the present context, surrogate modelling techniques – i.e. the

approximation of complex system models through mathematical surrogates – were

identified particularly attractive. Surrogate modelling techniques are best-suited for early

design phases, when the ranges of parametric variation are large while the number of

design variables is relatively small compared to more detailed design phases [34]. Due to

their extremely fast response times, surrogate models enable rapid design space

exploration and a quick gain of system behavioural knowledge. Surrogate model

application intrinsically enforces quality assurance measures such as expert checks prior

to the system level integration of subsystem analysis result data. The effectiveness of

surrogate model application, however, is limited by the off-line computational effort

required for surrogate model regression and validation which strongly increases with

rising nonlinearity of system behaviour and the number of free variables to be fitted [36].

Hence, in order to ensure a best and balanced synthesis of surrogate model accuracy and

sampling effort at the local level, for the present work, problem-oriented surrogate

modelling approaches are employed. The design and performance characteristics of the

main power plants systems as well as the BLI fuselage fan power plant are integrated

using Feedforward Neural Networks (FNN), trained and validated by Latin Hypercube

Sampled (LHS) [37] data as described in [36]. PFC aerodynamic performance properties,

structural design characteristics as well as the design and efficiency properties of the

turbo-electric power train components are integrated based on custom-developed non-

linear regression models. In the following, the surrogate-based model integration strategy

is discussed for the example of the bare PFC aerodynamic performance properties.

The aerodynamic mapping at the present preliminary stage in the project is based on 2D

axisymmetric RANS CFD simulations of the bare PFC configuration, i.e. the fuselage

body including FF propulsive device (cf. [4]). Key result properties from the CFD

computations include the flow field and corresponding freestream total pressure recovery

ratio at the FF front face, 𝑝2/𝑝0, the ideal power absorbed by the FF actuator disc, 𝑃𝐹𝐹,𝑑𝑖𝑠𝑐,

and, the Net Propulsive Force (NPF) of the bare PFC, being defined as

𝑁𝑃𝐹 = 𝐹𝐹𝐹,𝐷𝑖𝑠𝑐 − 𝐷𝑃𝐹𝐶,𝑏𝑎𝑟𝑒 ( 1 )

where 𝐹𝐹𝐹,𝐷𝑖𝑠𝑐 is the force produced by the FF disc and 𝐷𝑃𝐹𝐶,𝑏𝑎𝑟𝑒 is the drag produced by

all other components of the bare PFC geometry. In order to efficiently integrate the bare

PFC operational characteristics, a performance map was derived from CFD simulations

of a representative PFC aero-shaping as performed by TU Delft. As illustrated in Figure

3, the off-design performance map is dependent on the actual FPR and flight conditions,

which are explicitly the temperature deviation from norm atmosphere, 𝑑𝑇𝐼𝑆𝐴, the altitude,

𝐴𝑙𝑡, and the Mach number, 𝑀𝑎. This off design performance deck is matched to

parametric changes of the PFC design, such as FF blade height, ℎ𝐵𝑙𝑎𝑑𝑒 , or design pressure

ratio, 𝐹𝑃𝑅𝐷𝑒𝑠, as well as fuselage length, 𝐿𝐹𝑢𝑠, and the design flight conditions through

appropriate scaling, in the first instance. Whenever an updated aero-shaping is produced,

the validity of the operational performance map is gauged and adaptation is applied if

necessary.


Figure 3: PFC design and off design coupling

The bare PFC off-design map was produced for the above listed key performance

properties using a non-linear regression based surrogate model with sensitivity for

operational Mach number, altitude and effective fuselage Fan Pressure Ratio (FPR). As

an example, the response of the regression model for the NPF parameter within a typical

flight envelope at constant fuselage FPR=1.4 is shown in Figure 4. The coloured contours

indicate the operational NPF within the flight envelope relative to the sea level static NPF.

The red markers indicate the CFD simulation based regression samples.

Figure 4: Surrogate model fitting of bare PFC operational NPF at fuselage FPR = 1.40

The mapping quality of the NPF parameter for different operational fuselage FPRs is

shown in Figure 5 for two calibrated air speeds (CAS) in the relevant range for transversal

flight phases, namely CAS=137 m/s (≈ 266 knots) and CAS=144 m/s (≈ 280 knots). The

arithmetic mean deviation of the operational NPF surrogate model is 0.51% with a

maximum absolute deviation from the CFD data of 0.18kN.

Off-Design Bare PFC-Model

𝑁𝑃𝐹,𝑝2

𝑝0, 𝐹𝐷𝑖𝑠𝑐 =

𝐴𝑙𝑡, 𝑑𝑇𝐼𝑆𝐴 , 𝑀𝑎,𝐹𝑃𝑅

Analytical fuselage flow field scaling

calibrated to CFD data

Surrogate Model created for CFD-predicted

performance of representative FF-Design

During parametric studies of similar PFC designs, the

FF design disc force 𝐹𝐷𝑖𝑠𝑐,𝐷𝑒𝑠 is used as the scaling

parameter for the PFC off-design characteristics

Design Bare PFC-Model

𝑁𝑃𝐹𝐷𝑒𝑠 ,𝑝2

𝑝0 𝐷𝑒𝑠

, 𝐹𝐷𝑖𝑠𝑐,𝐷𝑒𝑠 , 𝑃𝐷𝑖𝑠𝑐 ,𝐷𝑒𝑠 =

𝐴𝑙𝑡𝐷𝑒𝑠 , 𝑑𝑇𝐼𝑆𝐴,𝐷𝑒𝑠 , 𝑀𝑎𝐷𝑒𝑠 , 𝑡 ℎ𝐵𝑙𝑎𝑑𝑒 , 𝐿𝐹𝑢𝑠 , 𝐹𝑃𝑅𝐷𝑒𝑠 ,

PFC Design:

Aerodynamic Design Point: M0.82, ISA+10K,FL350

FF Design FPR: 1.4

FF Blade Height: 0.58 m

Simulation Settings:

FF Off-design FPR: 1.4 constant

Angle of Attack: 0 constant

CFD modelling: axisymmetric 2D RANS

CFD Results

Aerodynamic

Design Point

Cruise Region

NP

F/N

PF

SLS

[-]

8 ISABE-2019-24141

Figure 5: Fitting quality of operational NPF surrogate model against FPR and altitude

3.0 SYSTEM SIZING APPROACH

As a result of uncommon systems specific to the PFC layout and distinct boundary

conditions – as the consideration of an aircraft family concept – this section will present

interesting dependencies for system and aircraft sizing.

3.1 Aircraft sizing The overall aircraft sizing process is implemented in the commercial modelling

environment Pacelab Suite [38] using the Pacelab Aircraft Preliminary Design (APD)

framework [38] as a baseline. APD offers a set of handbook methods for aircraft

conceptual design mostly based on Torenbeek [39]. As a starting point for the present

activities, a customised version of the framework featuring comprehensively

supplemented methodology based on BHL in-house developed semi-empirical and

analytical methods was employed (cf. [40], [36], [41] and [42]). During the

CENTRELINE project, these baseline methods are systematically replaced by surrogate

models created from the in-depth analyses of the PFC-specific design and performance

aspects performed by the CENTRELINE partners.

Key top-level parameters for the steering and direction of the overall PFC aircraft design,

include the design fan pressure ratios and diameters, the thrust split ratio between the

under-wing podded main and aft-fuselage BLI power plants, the FF relative axial position

along the fuselage, the fuselage slenderness ratio and aft-body upsweep angle, maximum

wing loading, and, the fuselage fan operational power scheduling. For the aircraft sizing

and performance evaluation in this paper, a step cruise profile is adopted targeting

maximum Specific Air Range (SAR) in each cruise point. International reserves are

applied including 200nm diversion distance, 30 minutes hold and 5% final reserves.

Figure 6 shows the implemented logic for PFC aircraft propulsion point performance

evaluation. With the actual thrust demand, 𝐹𝑁𝑟𝑒𝑞 , the altitude, 𝐴𝑙𝑡, temperature deviation

from ISA, 𝑑𝑇𝐼𝑆𝐴, and the Mach number, 𝑀𝑎, specified as inputs from the aircraft design

loop, the PFC propulsion system point performance evaluation logic is triggered.

Depending on the input parameter settings, the FPR schedule provides an FPR to the bare

PFC aerodynamics. The NPF of the bare PFC as well as the fuselage fan inflow conditions

and ideal disc power absorption, 𝑃𝐷𝑖𝑠𝑐 , are predicted by the bare PFC aerodynamics

surrogate model. The FF performance model derives the actual power consumption,

𝑃𝑆ℎ𝑎𝑓𝑡 , of the FF. With this shaft power and the shaft speed, 𝑁𝑆ℎ𝑎𝑓𝑡, the electrical system

model calculates the requested generator power offtakes from the main power

PFC Design:

Aerodynamic Design Point: M0.82, ISA+10K,FL350

FF Design FPR: 1.4



Angle of Attack: 0 constant

CFD modelling: axisymmetric 2D RANS


plants, 𝑃𝐺𝑒𝑛. The main power plant model predicts the fuel flow 𝑤𝑓𝑢𝑒𝑙 dependant on this

power offtake and thrust, 𝐹𝑁𝑀𝑎𝑖𝑛𝑃𝑃𝑆. The implemented point performance evaluation

scheme allows for the optimisation of FPR scheduling for optimum fuel flow.

Figure 6: Implemented logic for PFC aircraft propulsion point performance evaluation

3.2 Special implications of aircraft family sizing Reflecting contemporary product development practice, the PFC aircraft is part of a

family concept existing of a baseline (340 PAX), a stretch (391 PAX) and a shrink (296

PAX) family member, where the shrink and stretch variants are derived from the baseline

through addition or removal of fuselage sections. This strategy increases operational

flexibility to serve various market segments with a platform featuring a high degree of

commonality in structures and systems. In the devised aircraft family concept, all three

members have the following common assemblies:

Undercarriage

Wing

Pylons and main power plants

Empennage

Turbo electric powertrain including FF power plant

Aircraft subsystems

The stretch family member sizes the wing, main engines, pylon and undercarriage while

the shrink family member defines the empennage size. As a result of varying wing

loadings, all three family members have a different optimum top-of-climb altitude.

Therefore, all three aircraft cruise at different altitudes with the same Mach number and

have a different fuselage length equipped with the same fuselage fan. The implications of

this sizing strategy have to be carefully taken into account with respect to the sizing of

the FF and turboelectric powertrain.

3.3 Propulsion system sizing In order to provide the flexibility of the main engines model to enable a sizing procedure,

the design space of the main engines was described by multiple variables, including e.g.

design net thrust, design specific thrust, relative HPT cooling air demand (𝑤𝑐/𝑤25) and

design power of the power turbine (PT). For simulation of the engine operational

behaviour, this set of variables was supplemented by a series of typical off-design

variables including e.g. flight Mach number, altitude, relative fan corrected speed and the

PT offtake relative to the respective design power offtake. Utilising an experimental plan

based on Latin Hypercube Sampling (LHS) provided by BHL comprising in total 16

design and off-design variables, power plant characteristics were computed by Chalmers.

A description of the engine sizing process can be found in [32].

The net thrust of the main engines is sized to meet the stretch variant’s critical top level

aircraft requirement (TLAR) performance targets. In this case, the climb time of 25

Bare PFC-Aero

,𝑝2

𝑝0

= 𝐴𝑙𝑡 , 𝑑𝑇𝐼𝑆𝐴 ,𝑀𝑎, 𝐹𝑃𝑅

Mission Point Calculation Inputs for

Propulsion System

𝐹𝑁𝑟𝑒𝑞 , 𝐴𝑙𝑡, 𝑑𝑇𝐼𝑆𝐴 ,𝑀𝑎]

FF Performance

𝑃𝑆ℎ𝑎𝑓𝑡 ,𝑁𝑆ℎ𝑎𝑓𝑡 = 𝐴𝑙𝑡 , 𝑑𝑇𝐼𝑆𝐴 ,𝑀𝑎, 𝐹𝑃𝑅,𝑝2

𝑝0

Electrical System

𝑃𝐺𝑒𝑛 , = 𝑃𝑆ℎ𝑎𝑓𝑡 , 𝑁𝑆ℎ𝑎𝑓𝑡 , 𝑁𝐺𝑒𝑛 = 𝑡

Main Powerplant

𝐹𝑢𝑒𝑙 = 𝐴𝑙𝑡, 𝑑𝑇𝐼𝑆𝐴 , 𝑀𝑎, 𝑃𝐺𝑒𝑛 , 𝐹𝑁𝑀𝑎𝑖𝑛𝑃𝑃𝑆 )

𝐹𝑢𝑒𝑙

FPR Schedule

𝐹𝑁𝑟𝑒𝑞 , 𝐴𝑙𝑡, 𝑑𝑇𝐼𝑆𝐴 ,𝑀𝑎

Optimization

𝐹𝑁𝑀𝑎𝑖𝑛𝑃𝑃𝑆 = 𝐹𝑁𝑟𝑒𝑞 − 𝑁𝑃𝐹

10 ISABE-2019-24141

minutes is the most critical TLAR defining engine sizing. As outlined in Section 2, the

aero-propulsive optimization of the PFC fuselage including the fuselage propulsor was

an iterative process carried out in collaboration of TUD and BHL. In this study, the bare

PFC aero-propulsive characteristics pertaining to the aero-shaping of a recent design

iteration is integrated in the overall aircraft model and sensitivities regarding key

characteristics of the FF are investigated in more depth. The FF shaft power demand is

tracked during the whole mission. The FF electric drive motor is sized to the critical

torque and critical speed values which most likely do not occur at the same time . This

results in an oversizing of the motor but ensures that the motor is always operated outside

the field weakening area. The power management and distribution system is sized for the

maximum power demand during the mission, usually during take-off. [4] Hereby, the

resulting turbo electric drive train is able to safely withstand possible failure loads during

malfunctions.

A high torque requirement at take-off entails a largely oversized electrical system during

cruise. In order to minimize oversizing of the electrical system, an FPR schedule for the

FF is defined. During take-off, the FPR should be as small as possible to prevent

oversizing of electric components. During cruise, the optimum FPR should be reached.

For initial calculations and trade studies a linear FPR schedule characterized by a

proportionality between operating FPR and altitude was chosen due to the strong impact

of air density on FF power. As the project advances, an optimization of the operating FPR

for every mission point has to be performed to minimize fuel flow.

For mapping the characteristics of the FF power plant – in particular shaft power demand

and rotational speed – at aircraft level and thus enabling to investigate several FF

operating strategies, a corresponding design and performance model was set up in the

BHL in-house developed propulsion system simulation framework APSS [43,44]. The

fuselage propulsor is characterized by a single-rotating ducted fan layout. Typical

heuristics for design and off-design system description and corresponding iteration

schemes were implemented. The geometric parameterisation was adapted to allow for the

prescription of fan inlet hub diameter as a free variable, which was matched with the local

fuselage radial contour coordinate. Due to the expected detrimental impact of the

distorted inflow field on the efficiency of the FF propulsor, the polytropic design

efficiency of this component was assumed to be degraded by nominally 1.0% relative to

the podded power plants operated in free stream conditions. Operational fan performance

was modelled based on the GasTurb [45] standard fan map, in the first instance. Details

on the power plant modelling strategy can be found in [46]. As the project progresses, fan

performance maps specifically derived by UCAM for the considered application will be

incorporated.

4.0 DESCRIPTION OF BASELINE PFC AIRCRAFT

In order to facilitate critical assessment and benchmarking of the turbo-electric PFC

technology in the CENTRELINE project, a realistic application scenario including

advanced reference aircraft and propulsion systems for an aspired EIS year 2035 – dubbed

“R2035” – was defined. Based on the analysis of forecast data, a wide-body long-range

transport task featuring a 6500 nmi design range and a cabin capacity of 340 passengers

was identified as particularly promising for a possible future PFC aircraft product family

[4]. Equipped with advanced aerodynamic features, structural and systems technologies

as well as Ultra High Bypass Ratio (UHBR) Geared Turbo Fan (GTF) engines, the R2035

reference aircraft is predicted to deliver a 27% design mission block fuel reduction versus

a typical year 2000 aircraft serving the same transport task [4].

At the early stage of the project, an initial target design for the PFC aircraft was defined

using simplified semi-empirical methodology, featuring an 11% block fuel reduction

relative to the R2035 aircraft [4]. As part of this key requirements and challenging design

targets for the PFC aero-shaping, the airframe structural concept as well as the design and

performance characteristics of the main power plants and the fuselage fan including its

turbo-electric power train were specified. The baseline PFC aircraft design presented in


this section represents the first iteration of the integrated overall systems design based on

higher fidelity modelling.

4.1 Basic aircraft properties This section presents dimensions and key characteristics of the PFC baseline aircraft.

Figure 7 shows the 3-view of the PFC aircraft and a table with key specifications. The

design Range is 6500 nmi and design payload is 34000 kg. The design cruise Mach

number is 0.82.

Figure 7: 3-View of baseline PFC aircraft and key properties

Table 1 shows the mass breakdown for the turbo electric PFC baseline aircraft. Compared

to conventional aircraft the fuselage fan and the electric system were added to the mass

break down. These additional propulsion systems result in a relatively high total

propulsion system weight fraction of 9.4% of MTOW. Due to increased length compared

to the R2035 and the symmetrical position of the FF, the undercarriage is heavier for

achieving the same tail strike angle.

Table 1: PFC Baseline Mass Breakdown

MTOW fraction [%]

Wing 14.3

Surface Controls 1.02

Fuselage 10.7

Horizontal Tailplane (HTP) 0.74

Vertical Tailplane (VTP) 0.72

Undercarriage 4.69

Pylons 2.12

Structure Total 34.2

Fuselage Fan Propulsion System* 0.80

Turbo - Electric Power Train 1.63

Main Power Plants* 6.72

Propulsion Total 9.39

Systems 12.2

OEW 55.6

Design Payload 14.9

Design Reserve Fuel 3.18

Design Trip Fuel 26.3

Design TOW 100 *Including nacelles, excluding turbo electric generator/motor

Wing

Reference Area, Airbus m² 346

Aspect Ratio - 12.0

Span m 64.6

Fuselage Length m 70.5

Fuselage Diameter m 6.09

FF Blade Height m 0.58

Tailstrike Angle ° 10.0

FF Design FPR - 1.40

Design Payload PAX 340

Design Range nmi 6500

Turbo-electric Power Train

Power/Weight kW/kg 2.30

Cruise Efficiency - 0.90

ΔFF Efficiency vs. Podded Fans - -0.01

MTOW t 228

OEW t 127

MZFW t 175

MLW t 188

W/S kg/m² 671

Cruise Altitude FL 350-410

Cruise Mach Number mach 0.82

Cruise ISA temperature deviation K +10K

12 ISABE-2019-24141

4.2 Operational characteristics As mentioned in Section 3.2, the family sizing has design implications on the turbo

electric system. Figure 8 shows the flight profile during cruise along with the FF power

consumption of the different family members. The different step cruise characteristics

due to different wing loading can be seen very well. In the simulation of the aircraft, step

climb is performed in order to optimize SAR

Figure 8: Cruise altitude and fuselage fan power profile for different PFC family members

(M0.82, ISA+10 K)

Counterintuitively the motor sizing of the turbo electric drive train is not primarily defined

by a certain family member. As can be seen from Figure 8 the FF power consumption of

the different family members at the same altitude differ marginally. If resolved further

during the mission, maximum torque and maximum RPM of the motor during the mission

deviates less than 2% in-between the family members. This compares very well to the

findings from Figure 8.

Figure 9 presents key characteristics of the PFC baseline aircraft during climb and cruise

flight. In addition to the flight altitude, the shown parameters include NPF, FPR, FF shaft

power and the fuel flow of the main power plants. The three steps during cruise are visible

in the trend of each parameter. As a result of the applied FPR schedule, the FPR is directly

proportional to altitude. Therefore, each altitude step results in a change in fuselage fan

power consumption. Interestingly, this is associated with a reduction of the absorbed shaft

power reflecting the strong effect of the reduction in air density. The gain in NPF of the

bare PFC is connected to the FPR characteristic. The behavior of fuel flow results from

the superposition of the individual effects and the visible peaks occur due to the en route

climb maneuvers.

Figure 9: Characteristics during design mission (climb and cruise phases)


Transport Task Shrink,Baseline, Stretch:

296, 340, 391PAX @ 6500nmi

Step Cruise: M0.82, ISA+10K,FL350-410

Turbo-electric Power Train:

Power/Weight ~ 2.3kW/kg

Cruise Ef f iciency ~ 90%

ΔFF Ef f iciency vs. Podded Fans: -1%

PFC Design:

FF Design FPR: 1.4


Tailstrike Angle: 10


Transport Task:

340PAX @ 6500nmi

Step Cruise: M0.82, ISA+10K,

FL350-410



Cruise Efficiency ~ 90%

ΔFF Efficiency vs. Podded Fans: -1%

PFC Design:

FF Design FPR: 1.4



Characteristics of PFC Baseline AC

during design mission (climb and cruise)


5.0 TRADE STUDY RESULTS

In order to provide guidance to the further design refinement activities and gauge the

potential for further optimization of the actual design and to assess the plausibility of the

present study, several sensitivity studies have to be performed. For the PFC concept

especially trade studies regarding important parameters of the propulsion system and

component weights are conducted. This will be trade studies regarding the following

parameters:

NPF

FF blade height

FF design FPR

Main power plants cooling air

FF efficiency compared to freestream flow conditions

Turbo – electric power train efficiency

Turbo – electric power train weight

Main power plants specific thrust

Main power plants design thrust

VTP volume coefficient

HTP volume coefficient

Fuselage weight

FF weight

Empennage weight

Wing weight

Landing gear weight

A change in design NPF maintaining constant design FF power is a measurement for the

aero-propulsive design optimality. The improvement of that value is one of the most

important tasks as the CENTRELINE project advances. Furthermore, FF blade height and

FF design FPR are regarded as they are main design parameters influencing PFC

performance characteristics. Afterwards the main power plant cooling air trade study is

presented as it has a relatively big lever arm on block fuel and is dependent on FF

operation strategy. The trade study regarding polytropic efficiency of the FF compared to

operation in free stream condition follows. This efficiency deviation will subject to of

further detailed research. Afterwards trade studies regarding the turbo – electric power

train efficiency as well as turbo electric – power train power density are presented.

Subsequently the effect of a change of the empennage volume coefficients is investigated,

as the current design does not incorporate any potentially stabilizing effect of the FF.

Following are trade studies scrutinizing various component weights of the PFC aircraft.

Especially the fuselage weight sensitivity is interesting, as the fuselage structural weight

prediction will be refined when the project continues to move forward, as detailed

structural strategies on how to implement the FF will be examined in depth.

All figures feature a red cross indicating the abscissa value corresponding to the baseline

PFC aircraft, while the ordinate represents neutrality in all response values. In all studies,

the sensitivities of OEW, MTOW and design mission block fuel on the varied parameter

is assessed. Calculated points are marked with a square. The plotted lines represent a third

degree polynomial fitting of the calculated points. The abscissa values are different for

all trade studies as they represent a reasonable interval for each study.

5.1 Propulsion system parameters This section aims at investigating the impact of important PFC propulsion system

parameters on the overall system level. In addition, the sensitivity of key technology

parameters are investigated to gain further knowledge on the reliability of the overall

system results and to prioritize the criticality of certain system models regarding fidelity.

Figure 10 illustrates the substantial impact of NPF (see equation 1) on overall aircraft

characteristics. As a theoretical scenario, this parameter was increased by up to +6 kN

assuming constant FF power consumption. A higher NPF at constant power is the direct

14 ISABE-2019-24141

result of further progress in the aero-propulsive optimization of the aft-fuselage and

nacelle shaping.

Figure 10: Aircraft design trade study of change in design NPF maintaining constant FF design

power

Figure 11 shows the results of varying FF blade height. A greater blade height than chosen

for the actual PFC design seems beneficial. As can be seen, OEW is rising with increasing

duct height because FF weight as well as fuselage weight increases. A larger duct also

leads to a longer and heavier undercarriage and higher power offtakes at the main engines.

The efficiency gain of the BLI effect seem to overcome these penalties until a duct height

of approximately 0.8 meters. This must be further assessed in the future and could lead

to a larger FF device as the project proceeds.

Figure 11: Aircraft design trade study FF blade height

Figure 12 investigates the design FPR of the FF. The design FPR seems to be chosen

close to its best value for the current aircraft since it is close to the block fuel minimum.

Figure 12: Aircraft design trade study of design fuselage FPR






Transport Task

340PAX @ 6500nmi



FF Design FPR: 1.4

PFC Reference Design

Delta NPF [N]

cascade effects

included in A/C resizing

Transport Task

340PAX @ 6500nmi



FF Design FPR: 1.4






FF Blade Height [m]

cascade effects







Transport Task

340PAX @ 6500nmi




Design FPR Fuselage Fan [-]

cascade effects



Figure 13 describes the impact of relative HPT cooling air demand, 𝑤𝑐/𝑤25. The value

of 26% was chosen conservatively compared to 24% in the reference aircraft “R2035”. It

can be seen that the relative amount of cooling air has a strong impact on the design

mission fuel burn emanating from the significant impact on both TSFC and flow path

dimensions. Further investigations related to a fuselage FPR schedule allowing for

reduced main engine temperature levels and thus cooling air demand is advised. As

mentioned in Section 2.0 the bare PFC aerodynamic data in the actual iteration of the PFC

aircraft is derived from 2-D analysis. This analysis does not account for three dimensional

effects during take-off rotation. As the project advances these effects will be assessed.

Once incorporated, a further optimization taking into account cooling air dependency for

varying design settings in combination with an optimized FPR schedule is advised.

Figure 13: Aircraft design trade study of main power plant relative cooling air

Figure 14 shows the dependency of a variation of the fuselage fan design polytropic

efficiency compared to a fan operating in freestream conditions. The assumption of a 1%

degradation of FF design polytropic efficiency is based on computational and

experimental results for BLI fans reported in the literature, cf. e.g. [47, 48]. As the

CENTRELINE project advances this value will be substantiated through numerically

computed results for the considered PFC configuration.

Figure 14: Aircraft design trade study varying fuselage fan design polytropic efficiency compared

to a fan operating in freestream conditions

Figure 15 and Figure 16 can be used as direct indicators for improved turbo-electric power

train efficiency and weight properties. It can be seen that an improvement in turbo-electric

power train efficiency by 1% yields approximately the same block fuel benefit as 12%

weight reduction in the turbo-electric power train.






Transport Task

340PAX @ 6500nmi



FF Design FPR: 1.4


Rel. HPT Cooling Air (𝑤 /𝑤 ) [-]

cascade effects







Transport Task

340PAX @ 6500nmi


ΔFF Efficiency vs. Podded Fans Design Point: -1%

FF Design FPR: 1.4


Fuselage Fan Efficiency deviation compared to free stream flow [%]

cascade effects


16 ISABE-2019-24141

Figure 15: Aircraft design trade study varying electrical system weight

Figure 16: Aircraft design tradestudy varying the total transmission efficiency of the turbo electric

drivetrain

In Figure 17, the effect of varying design specific thrust levels (𝐹𝑁/𝑤2) of the main engines

is visualised. Reducing values of FN/w2 translate into growing fan diameters, thus yielding

increasing values of OEW including cascading effects. Additionally, the study illustrates

a direct trade-off with turbine cooling air requirements, which is kept constant in the

present sensitivity study, but would need to be adjusted for varying power plant

temperature levels at take-off as a result of design specific thrust implications on take-off

performance.

Figure 17: Aircraft design trade study of design specific thrust of main power plants

As the engines are sized to meet the stretch variant’s climb time requirement, Figure 18

analyses the possible savings due to a smaller net thrust sizing. A downsizing of the

engine may be possible if a correspondingly adapted FPR schedule is used for the stretch

and the baseline family member.




Power/Weight Design Point ~ 2.3kW/kg


Transport Task

340PAX @ 6500nmi



FF Design FPR: 1.4


Electrical System Weight Change [%]

cascade effects


Transport Task

340PAX @ 6500nmi



FF Design FPR: 1.4






Cruise Efficiency Design Point ~ 90%

Relative efficiency change of electrical system [%]

cascade effects







Transport Task

340PAX @ 6500nmi



FF Design FPR: 1.4


Specific Thrust Main Engines [m/s]

cascade effects



Figure 18: Aircraft design trade study of design net thrust

5.2 Empennage sizing Figure 19 and Figure 20 examine the sensitivity of changing volume coefficients of the

empennage. In the aircraft design process the potentially stabilizing effect of the FF

nacelle has not yet been taken into account. This means a reduction of the volume

coefficient of the HTP and VTP might be possible.

Figure 19: HTP volume coefficient aircraft design trade study

Figure 20: VTP volume coefficient aircraft design trade study

Figure 21 assesses the empennage weight change. Since the VTP strongly contributes to

the structural stability of the fuselage propulsor nacelle, the empennage weight may be

subject to changes in further design iterations, which will incorporate high-fidelity aero-

structural computation results. The gradient of the results show trends which would also

be expected for conventional aircraft.






Transport Task

340PAX @ 6500nmi



FF Design FPR: 1.4


Design Thrust Change Podded Engines [%]

cascade effects







Transport Task

340PAX @ 6500nmi



FF Design FPR: 1.4


HTP Volume Coefficient Change [%]

cascade effects







Transport Task

340PAX @ 6500nmi



FF Design FPR: 1.4


VTP Volume Coefficient Change [%]

cascade effects


18 ISABE-2019-24141

Figure 21: Aircraft design trade study of empennage weight

5.3 General component weight sensitivities The fuselage weight impact is analysed in Figure 22. The structural integration of the

fuselage fan has an impact on fuselage weight. As structural requirements also feed back

into the fuselage fan design the fuselage weight and structural strategies will be

numerically analysed by WUT in more depth as the CENTRELINE project moves

forward.

Figure 22: Aircraft design trade study varying fuselage weight

Figure 23 assesses the sensitivity of the results for a change of the fuselage fan weight

technology factor. The resulting trends are almost linear.

Figure 23: Aircraft design trade study varying fuselage fan weight

In Figure 24 a variation of wing weight technology factor is conducted. The trend for

OEW, block fuel and MTOW is also almost linear.






Transport Task

340PAX @ 6500nmi



FF Design FPR: 1.4


Empennage Weight Change [%]

cascade effects







Transport Task

340PAX @ 6500nmi



FF Design FPR: 1.4


Fuselage Weight Change [%]

cascade effects







Transport Task

340PAX @ 6500nmi



FF Design FPR: 1.4


Fuselage Fan Weight Change [%]

cascade effects



Figure 24: Aircraft design trade study of wing weight

Figure 25 shows a variation of the landing gear weight technology factor. The sizing for

the landing gear is conducted in the stretch version to meet the take-off rotation

requirement. In this respect, the critical sizing case is constituted by the ground strike of

the nacelle of the FF. As can be seen in the mass break down of the PFC aircraft the

landing gear seems to have a slightly higher MTOW fraction than comparable standard

aircraft. This means that a variation of the landing gear weight has a higher impact on

MTOW, OEW and block fuel as would be expected for conventional aircraft.

Figure 25: Aircraft design trade study of landing gear weight

Apart from the landing gear, the conventional component trade studies in this section

behave as expected for conventional aircraft configurations. Due to the FF, the design

space for a family design is larger than for conventional aircraft, which could allow for a

reduction of some penalties derived for standard aircraft family designs.

6.0 CONCLUSION

This paper presented a multidisciplinary assessment approach along with interim findings

and integrated design results for tube and wing aircraft configuration employing fuselage

wake-filling propulsion integration, the so-called Propulsive Fuselage Concept (PFC).

The configuration investigated as part of the EC-funded Horizon 2020 collaborative

project CENTRELINE is characterized by a turbo electrically driven, aft-fuselage

installed ducted, boundary layer ingesting propulsor, while the main share of the aircraft’s

net thrust is provided by underwing podded Geared Turbofan power plants.

The paper commenced with the discussion of the approach used for the integration of

specialized data corresponding to the different disciplines. Thereafter, the integrated

sizing process including an aircraft design process is described and the used methods are

discussed. Based on this methodological framework, several trade studies investigating

the impact of considerations for product family implications in the integrated sizing

process were presented. Furthermore, the influence of important propulsion system sizing

Transport Task

340PAX @ 6500nmi



FF Design FPR: 1.4







Wing Weight Change [%]

cascade effects


Transport Task

340PAX @ 6500nmi



FF Design FPR: 1.4







Landing Gear Weight Change [%]

cascade effects


20 ISABE-2019-24141

parameters was elaborated. As a major result, it was established that the system level

sensitivities for conventional components, sized as part of the family sizing process,

behave similar to those expected for conventional aircraft family design. In contrast to

conventional aircraft family sizing, the fuselage fan could offer the freedom to decrease

family sizing penalties through application of different fuselage fan operating strategies

in the different family members. Regarding propulsion system sizing parameters, the

turbine cooling air demand was found to have a strong impact on fuel burn. As part of

further studies in CENTRELINE, the cooling air demand will be evaluated

parametrically, taking into account the temperature levels at the relevant power plant

operating conditions. Together with optimized operating schedules of the fuselage

propulsor, this will allow for the investigation of the impact of fuselage fan sizing and

performance parameters on the required net thrust and hence temperature levels

demanded of the PFC main engines. The optimization of the aero shaping of the fuselage

fan propulsor is one of the main tasks as the sensitivity study showed a large potential to

further decrease fuel burn with a better design. Additionally, further investigation of a

variable blade pitch fuselage fan device as well as variable nozzle area could widen the

FF operating range and improve FF efficiency. Also, it is advised to analyse the structure

of fuselage and fuselage fan in more detail. To further improve model accuracy, 3D CFD

calculations especially during take-off rotation are needed. Smaller empennage sizing

could be possible after investigating the stabilizing effect of the FF nacelle. To find the

most beneficial application for BLI, a variation of payload and range as well as cruise

Mach number is recommended.

ACKNOWLEDGMENTS

The CENTRELINE project has received funding from the European Union’s Horizon

2020 research and innovation programme under grant agreement No. 723242.

The authors would like to convey their gratitude to the partners (TU Delft, Siemens and

Chalmers University of Technology) and BHL team members for providing the results

from their detailed design and analysis activities as inputs to the overall aircraft design

integration.

REFERENCES

[1] European Commission, “Flightpath 2050: Europe’s Vision for Aviation”, Report of

the High Level Group on Aviation Research, Publications Office of the European Union,

Luxembourg, 2011

[2] Advisory Council for Aviation Research and Innovation in Europe, “Strategic

Research and Innovation Agenda”, Brussels, 2012

[3] National Aeronautics and Space Administration (NASA), “Advanced Concept Studies

for Subsonic and Supersonic Commercial Transports Entering Service in the 2030-35

Period”, 2007

[4] Seitz, A., Peter, F., Bijewitz, J., Habermann, A., Goraj, Z., Kowalski, M., Castillo, A.,

Meller, F., Merkler, R., Samuelsson, S., Petit, O., van Sluis, M., Della Corte, B.,

Wortmann, G., Dietz, M., “Concept Validation Study for Fuselage Wake-Filling

Propulsion Integration”, 31st Congress of the International Council of the Aeronautical

Sciences, Belo Horizonte, Brazil, September 09-14, 2018

[5] Smith, L. H. Jr., “Wake ingestion propulsion benefit”, Journal of Propulsion and

Power, Vol. 9, No. 1, 1993, pp 74-82, DOI 10.2514/3.11487

[6] Plas, A. P., Sargeant, M. A., Madani, V., Crichton, D., Greitzer, E. M., Hynes, T. P.,

Hall, C. A., “Performance of a Boundary Layer Ingesting (BLI) Propulsion System“,

AIAA 2007-450, 45th AIAA Aerospace Sciences Meeting and Exhibit, Reno, NV, 2007

[7] Drela, M., “Power Balance in Aerodynamic Flows”, AIAA 2009-3762, 27th AIAA

Applied Aerodynamics Conference, San Antonio, TX, 2009


[8] Arntz, A., “Civil Aircraft Aero-thermo-propulsive Performance Assessment by an

Exergy Analysis of High-fidelity CFD-RANS Flow Solutions” Dissertation, Universite

de Lille, 2014

[9] Atinault, O., Carrier, G., Grenon, R., Verbecke, C., Viscat, P., “Numerical and

Experimental Aerodynamic Investigations of Boundary Layer Ingestion for Improving

Propulsion Efficiency of Future Air Transport”, AIAA 2013-2406, 31st AIAA Applied

Aerodynamics Conference, Fluid Dynamics and Co-located Conferences, San Diego,

CA, 2013

[10] Lv, P., Ragni, D., Hartuc, T., Veldhuis, L., Rao, A. G., “Experimental Investigation

of the Flow Mechanisms Associated with a Wake-Ingesting Propulsor”, AIAA Journal,

Vol. 55, No. 4, April 2017

[11] Uranga, A., Drela, M., Greitzer, E. M., Titchener, N. A., Lieu, M. K., Siu, N. M.,

Huang, A. C., Gatlin, G. M., Hannon, J. A., “Preliminary Experimental Assessment of

the Boundary Layer Ingestion Benefit for the D8 Aircraft”, AIAA 2014-0906, 52nd

Aerospace Sciences Meeting, National Harbor, MD, 2014

[12] Uranga, A., Drela, M., Greizer, E. M., Hall, D. K., Titchener, N. A., Lieu, M. K.,

Siu, N. M., Casses, C., Huang, A. C., Gatlin, G. M., Hannon, J. A., “Boundary Layer

Ingestion Benefit of the D8 Transport Aircraft”, AIAA Journal, Vol. 55, No. 11,

November 2017

[13] Isikveren, A.T., Seitz, A., Bijewitz, J., Mirzoyan, A., Isyanov, A., Grenon, R.,

Atinault, O., Godard, J. L., Stückl, S., “Distributed Propulsion and Ultra-high By-Pass

Rotor Study at Aircraft Level”, The Aeronautical Journal, Vol. 119, No. 1221, 2015, pp.

1327-1376

[14] Steiner, H.-J., Seitz, A., Wieczorek, K., Plötner, K., Isikveren, A.T., Hornung, M.,

“Multi-Disciplinary Design and Feasibility Study of Distributed Propulsion Systems”,

28th International Congress of the Aeronautical Sciences, Brisbane, Australia, September

23-28, 2012

[15] Bradley, M., Droney, C., “Subsonic Ultra Green Aircraft Research Phase II: N+4

Advanced Concept Development”, NASA CR-2012-217556, 2012

[16] Stückl, S., van Toor, J., Lobentanzer, H., “Voltair – The All Electric Propulsion

Concept Platform – A Vision for Atmospheric Friendly Flight”, 28th International

Congress of the Aeronautical Sciences, Brisbane, Australia, September 23-28, 2012

[17] Rolt, A., Whurr, J., “Optimizing Propulsive Efficiency in Aircraft with Boundary

Layer Ingesting Distributed Propulsion”, ISABE-2015-20201, 22nd ISABE Conference,

Phoenix, AZ, 2015

[18] Seitz, A., “Power Train Options for a Propulsive Fuselage Aircraft Layout”, More

Electric Aircraft USA Conference, Seattle, WA, 29-30 August 2016

[19] Welstead, J., Felder, J., “Conceptual Design of a Single-Aisle Turboelectric

Commercial Transport with Fuselage Boundary Layer Ingestion”, AIAA 2016-1027, 54th

AIAA Aerospace Sciences Meeting, San Diego, CA, 2016

[20] Antcliff, K., Capristan, F., “Conceptual Design of the Parallel Electric-Gas

Architecture with Synergistic Utilization Scheme (PEGASUS) Concept”, AIAA

AVIATION Forum, 5-9 June 2017, Denver, CO, 2017

[21] Harish, A., Gladin, J., Mavris, D., “Architecture Evaluation of a Single-aisle Turbo-

electric Aircraft with Single Engine-out Constraint”, AIAA AVIATION Forum, 25-29

June 2018, Atlanta, GA, 2018

[22] Goraj, Z., Goliszek, B.,Kowalski, M., Seitz,A. , Peter, F., Meller, F., “Strategy and

Implementation of a Parametric CAD Model for R2035 Aircraft Structure and External

Configuration”, 31st Congress of the International Council of the Aeronautical Sciences,

Belo Horizonte, Brazil, September 09-14, 2018

22 ISABE-2019-24141

[23] Wortmann, G., “Electric Machinery Preliminary Design Report”, CENTRLINE

Project Public Deliverable D4.04, 22.10.2018

[24] Della Corte, B., van Sluis, M., “Specification of Wind Tunnel Model Design and

Test Campaign Plan”, CENTRLINE Project Public Deliverable D3.01, 21.11.2018

[25] Castillo Pardo, A., “Specification of Fan Design and Rig Test Campaign Plan”,

CENTRLINE Project Public Deliverable D3.04, 07.11.2018

[26] Shamiyeh, M., “Definition of multidisciplinary interfacing strategy”, CENTRLINE

Project Public Deliverable D2.01, 23.04.2018

[27] Habermann, A., Bijewitz, J., Seitz, A., Hornung, M., „Performance Bookkeeping for

Aircraft Configurations with Fuselage Wake-Filling Propulsion System Integration“,

Deutscher Luft- und Raumfahrtkongress 2018, Friedrichshafen, Germany, 2018

[28] MIDAP Study Group: Guide to in-flight thrust measurement of turbojets and fan

engines. AGARDograph No. 237 (1979).

[29] Della Corte, B., van Sluis, M., Rao, A.G., Veldhuis, L.L.M., “Fundamental

Investigation of Boundary Layer Ingestion on an Axisymmetric Body of Revolution”,

ISABE Conference 2019, Canberra, Australia, 2019

[30] Castilla Pardo, A., Hall, C. A., “Aerodynamics of Boundary Layer Ingesting

Fuselage Fans”, ISABE Conference 2019, Canberra, Australia, 2019

[31] Goraj, Z., Kowalski, M., Goliszek, B., “Optimisation of the Loading Structure for

Propulsive Fuselage Concept”, ISABE Conference 2019, Canberra, Australia, 2019

[32] Samuelsson, S., Petit, O., Merkler, R., Wortmann, G., “Adaptation of a Turbofan

Engine for High Power Offtakes for a Turboelectric Propulsive Fuselage Concept “,


[33] Merkler, R., Samuelsson, S., Wortmann, G., “Integration Aspects for Large

Generators into Turbofan Engines for a Turbo-Electric Propulsive Fuselage Concept“,


[34] Sobieszczanski-Sobieski, J., Agte, J., Sandusky Jr., R., “Bi-level integrated system

synthesis (BLISS)”, NASA Technical Memorandum, Langley Research Center,

Hampton, Virginia, August 1998. NASA-TM-1998-208715.

[35] Sobieszczanski-Sobieski, J., Emiley, M., Agte, J., Sandusky Jr., R., “Advancement

of bi-level integrated system synthesis (BLISS)”, NASA Technical Memorandum,

Langley Research Center, Hampton, Virginia, December 2000. NASA/TM-2000-

210305.

[36] Seitz, A., “Advanced Methods for Propulsion System Integration in Aircraft

Conceptual Design”, Ph.D. Dissertation, Institut für Luft- und Raumfahrt, Technische

Universität München, 2012

[37] McKay, M., Beckman, R., and Conover, W., “A comparison of three methods for

selecting values of input variables in the analysis of output from a computer code”,

Technometrics, 21(2):239–245, May 1979.

[38] Pacelab GmbH, 2012, “Pacelab Engineering Workbench 5.1.1”, Berlin

[39] Torenbeek, E., “Synthesis of Subsonic Airplane Design”. Kluver Academic

Publishers, Dordrecht, Boston, London, 1982

[40] Gologan, C., “A Method for the Comparison of Transport Aircraft with Blown

Flaps”, PhD Thesis, Technische Universität München, 2010

[41] Pornet, C., “Conceptual Design Methods for Sizing and Performance of Hybrid-

Electric Transport Aircraft”, PhD Thesis, Technische Universität München, 2018


[42] Vratny, P., “Conceptual Design Methods of Electric Power Architectures for Hybrid

Energy Aircraft”, PhD Thesis, Technische Universität München, 2018.

[43] Kaiser, S., “Introduction to Aircraft Propulsion System Simulation (APSS)”, Internal

Report 16/003, Bauhaus Luftfahrt e.V., 2016

[44] Kaiser, S., Donnerhack, S., Lundbladh, A., Seitz, A., “Composite Cycle Engine

Concept with Hectopressure Ratio,” Journal of Propulsion and Power, Vol. 32, No. 6, pp.

1413-1421, 2016. doi: 10.2514/1.B35976

[45] Kurzke, J., “GasTurb 12 – Design and Off-Design Performance of Gas Turbines”,

2013

[46] Bijewitz, J., Seitz, A., Hornung, M., “Power Plant Pre-Design Exploration for a

Turbo-Electric Propulsive Fuselage Concept”, AIAA 2018-4402, AIAA Propulsion and

Energy Forum, Cincinnati, OH, 2018

[47] Hall, C., Gunn, E., Perovic, D., “Fan systems for Boundary Layer Ingestion”,

IMechE Special Conference on Distributed Propulsion, London, UK, 18 November 2014.

[48] Razvan V. Florea, Claude Matalanis, Larry W. Hardin, Mark Stucky, and Aamir

Shabbir, “Parametric Analysis and Design for Embedded Engine Inlets”, Journal of

Propulsion and Power, Vol. 31, No. 3, pp. 843-850, 2015, DOI: 10.2514/1.B34804.

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