Research

23 pages, 6123 KiB

Open AccessArticle

Conceptual Design of a Hybrid Hydrogen Fuel Cell/Battery Blended-Wing-Body Unmanned Aerial Vehicle—An Overview

by Siwat Suewatanakul, Alessandro Porcarelli, Adam Olsson, Henrik Grimler, Ariel Chiche, Raffaello Mariani and Göran Lindbergh

Aerospace 2022, 9(5), 275; https://doi.org/10.3390/aerospace9050275 - 19 May 2022

Cited by 16 | Viewed by 5409

Abstract

The manuscript presents the conceptual design phase of an unmanned aerial vehicle, with the objective of a systems approach towards the integration of a hydrogen fuel-cell system and Li-ion batteries into an aerodynamically efficient platform representative of future aircraft configurations. Using a classical [...] Read more.

The manuscript presents the conceptual design phase of an unmanned aerial vehicle, with the objective of a systems approach towards the integration of a hydrogen fuel-cell system and Li-ion batteries into an aerodynamically efficient platform representative of future aircraft configurations. Using a classical approach to aircraft design and a combination of low- and high-resolution computational simulations, a final blended wing body UAV was designed with a maximum take-off weight of 25 kg and 4 m wingspan. Preliminary aerodynamic and propulsion sizing demonstrated that the aircraft is capable of completing a 2 h long mission powered by a 650 W fuel cell, hybridized with a 100 Wh battery pack, and with a fuel quantity of 80 g of compressed hydrogen. Full article

(This article belongs to the Special Issue Advances in Aerospace Sciences and Technology II)

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28 pages, 556 KiB

Open AccessArticle

On the Extrapolation of Stability Derivatives to Combined Changes in Airspeed and Angles of Attack and Sideslip

by Luís M. B. C. Campos and Joaquim M. G. Marques

Aerospace 2022, 9(5), 249; https://doi.org/10.3390/aerospace9050249 - 03 May 2022

Viewed by 1739

Abstract

The variation in stability derivatives with airspeed and angles of attack and sideslip is determined using only the dependence of the aerodynamic forces and moments on the modulus and direction of the velocity. Analytic extrapolation factors are obtained for all 12 longitudinal plus [...] Read more.

The variation in stability derivatives with airspeed and angles of attack and sideslip is determined using only the dependence of the aerodynamic forces and moments on the modulus and direction of the velocity. Analytic extrapolation factors are obtained for all 12 longitudinal plus 12 lateral stability derivatives of linear decoupled motion. The extrapolation factors relate the stability derivatives for two flight conditions with different airspeeds, angles of attack (AoA), and angles of sideslip (AoS). The extrapolation formulas were validated by comparison with results of computational fluid dynamics (CFD) using Reynolds-averaged Navier–Stokes (RANS) equations. The comparison concerns the extrapolated full longitudinal–lateral stability matrix from one landing and one takeoff condition of a V-tailed aircraft, to 10 other landing and takeoff flight cases with different airspeeds, AoAs, and AoSs. Thus, 420 comparisons were made between extrapolated stability derivatives and CFD–RANS results demonstrating the achievable levels of accuracy. Full article

(This article belongs to the Special Issue Advances in Aerospace Sciences and Technology II)

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26 pages, 1098 KiB

Open AccessArticle

Adaptive Initial Sizing Method and Safety Assessment for Hybrid-Electric Regional Aircraft

by Nicolas Moebs, Dominik Eisenhut, Evert Windels, Jenny van der Pols and Andreas Strohmayer

Aerospace 2022, 9(3), 150; https://doi.org/10.3390/aerospace9030150 - 08 Mar 2022

Cited by 9 | Viewed by 3537

Abstract

In the wake of many climate-friendly initiatives, the aviation sector must become more sustainable. A potential path for regional airliners could be the installation of hybrid-electric powertrains. In this work, a conceptual study design of various powertrain architectures is conducted. This helps the [...] Read more.

In the wake of many climate-friendly initiatives, the aviation sector must become more sustainable. A potential path for regional airliners could be the installation of hybrid-electric powertrains. In this work, a conceptual study design of various powertrain architectures is conducted. This helps the designer to quickly generate approximate numbers on the basic characteristics of new aircraft configurations. These results can be used to advance subsystems modeling or improve the starting values in the following preliminary aircraft design. After the selection of representative architectures, reasonable technological assumptions were gathered, ranging between a conservative and an optimistic scenario. This was done for powertrain components, various energy storage concepts and structural and aerodynamic changes. The initial sizing method was developed by building two interconnected sizing iteration loops. In addition, a safety assessment was integrated due to the many unconventional components in the powertrain’s setup. The results show that the fuel consumption of a conventional aircraft is not undercut with a hybrid-electric powertrain aircraft based on conservative technological assumptions. In the optimistic scenario, however, selected powertrain architectures show a significant drop in fuel consumption when compared to the conventional one. Furthermore, the use of synergistic effects and systematic powertrain optimizations can decrease the fuel consumption even further. In conclusion, it was shown that this initial sizing method can calculate entire hybrid-electric aircraft designs on a conceptual level. The results can quickly present trends that are reasonable and helpful. In addition, the safety assessment first gives evidence about which levels of safety have to be considered for the different components in the development of hybrid-electric powertrains. Full article

(This article belongs to the Special Issue Advances in Aerospace Sciences and Technology II)

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22 pages, 3913 KiB

Open AccessArticle

Low Speed Aerodynamic Analysis of the N2A Hybrid Wing–Body

by Andrea Aprovitola, Francesco Aurisicchio, Pasquale Emanuele Di Nuzzo, Giuseppe Pezzella and Antonio Viviani

Aerospace 2022, 9(2), 89; https://doi.org/10.3390/aerospace9020089 - 10 Feb 2022

Cited by 1 | Viewed by 4726

Abstract

Reduction of atmospheric emissions is currently a mandatory requirement for aircraft manufacturers. Several studies performed on Blended Wing–Body configurations showed a promising capability of reducing fuel consumption by increasing, at the same time, passengers’ transport capabilities. Although several aerodynamic studies are available at [...] Read more.

Reduction of atmospheric emissions is currently a mandatory requirement for aircraft manufacturers. Several studies performed on Blended Wing–Body configurations showed a promising capability of reducing fuel consumption by increasing, at the same time, passengers’ transport capabilities. Although several aerodynamic studies are available at transonic speeds, low-speed evaluations of aerodynamic performances of Blended Wing Body aircrafts are less investigated. In this framework, the present paper deals with the aerodynamic performance of the N2A aircraft prototype at low-Mach number conditions. Aircraft longitudinal aerodynamics is addressed at

M_{\infty} = 0.2

with steady state three-dimensional RANS simulations carried out at two Reynolds numbers equal to

6.60 \times 10^{6}

and

1.27 \times 10^{8}

, respectively. The former refers to an experimental test campaign performed at NASA Langley 14-by-22 foot subsonic tunnel, while the latter is related to free-flight conditions close to an approach and landing phase. Flowfield simulations are performed using the Computational Fluid Dynamic code FLUENT and the SU2 open-source code, currently adopted for research applications. Numerical solutions are validated by using available experimental data with reference to lift, drag, pitching moment and drag polar estimations. Pre-stall and post-stall aerodynamic behaviour through mean flow-field visualization along with the comparison of pressure distributions at several AoAs is addressed. Furthermore, the effect of convective discretization on a numerical solution for SU2 is discussed. Results indicate a good agreement with available experimental predictions. The present study aims to bridge existing computations at a Eulerian low-Mach number, with RANS computations and constitutes a further test-case for SU2 code with respect to a full aircraft configuration. Full article

(This article belongs to the Special Issue Advances in Aerospace Sciences and Technology II)

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22 pages, 5967 KiB

Open AccessArticle

In-Situ Optical Measurements of Solid and Hybrid-Propellant Combustion Plumes

by Stephen A. Whitmore, Cara I. Frischkorn and Spencer J. Petersen

Aerospace 2022, 9(2), 57; https://doi.org/10.3390/aerospace9020057 - 23 Jan 2022

Cited by 3 | Viewed by 2313

Abstract

A method for in-situ optical measurements of solid and hybrid propellant rocket plumes is developed, and results from proof of concept tests are presented. The developed method inserts fiber-optic cables acting as radiation conduits into the solid-fuel combustion port, allowing optical signals to [...] Read more.

A method for in-situ optical measurements of solid and hybrid propellant rocket plumes is developed, and results from proof of concept tests are presented. The developed method inserts fiber-optic cables acting as radiation conduits into the solid-fuel combustion port, allowing optical signals to be transmitted from the flame zone to externally-mounted spectrometers. Multiple hot-firings using a using a lab-scale gaseous-oxygen, thermo-plastic fueled hybrid rocket system were performed to validate the sensing method. Burn durations varied from 5 to 25 s, and the inserted fiber optic sensors survived for all of the hot fire tests. The obtained optical spectra were curve-fit to Planck’s black-body radiation law, and Wien’s displacement law was used to estimate the internal flame-temperature. Optically-sensed flame-temperatures are correlated to analytical predictions, and shown to generally agree within a few degrees. Additionally, local maxima in the optical spectra are shown to correspond to emission frequencies of atomic and molecular hydrogen, water vapor, and molecular nitrogen; all species known to exist in the hybrid combustion plume. Based on these preliminary test results, it is concluded that this simple in-situ measurement system operates as designed, and it shows considerable promise for future applications to a wide swath of gas-generator systems. Full article

(This article belongs to the Special Issue Advances in Aerospace Sciences and Technology II)

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14 pages, 1557 KiB

Open AccessArticle

Assessment of the Impact of Material Selection on Aviation Sustainability, from a Circular Economy Perspective

by Dionysios N. Markatos and Spiros G. Pantelakis

Aerospace 2022, 9(2), 52; https://doi.org/10.3390/aerospace9020052 - 20 Jan 2022

Cited by 13 | Viewed by 4526

Abstract

Climate change and global warming pose great sustainability challenges to the aviation industry. Alternatives to petroleum-based fuels (hydrogen, natural gas, etc.) have emerged as promising aviation fuels for future aircraft. The present study aimed to contribute to the understanding of the impact of [...] Read more.

Climate change and global warming pose great sustainability challenges to the aviation industry. Alternatives to petroleum-based fuels (hydrogen, natural gas, etc.) have emerged as promising aviation fuels for future aircraft. The present study aimed to contribute to the understanding of the impact of material selection on aviation sustainability, accounting for the type of fuel implemented and circular economy aspects. In this context, a decision support tool was introduced to aid decision-makers and relevant stakeholders to identify and select the best-performing materials that meet their defined needs and preferences, expressed through a finite set of conflicting criteria associated with ecological, economic, and circularity aspects. The proposed tool integrates life-cycle-based metrics extending to both ecological and economical dimensions and a proposed circular economy indicator (CEI) focused on the material/component level and linked to its quality characteristics, which also accounts for the quality degradation of materials which have undergone one or more recycling loops. The tool is coupled with a multi-criteria decision analysis (MCDA) methodology in order to reduce subjectivity when determining the importance of each of the considered criteria. Full article

(This article belongs to the Special Issue Advances in Aerospace Sciences and Technology II)

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28 pages, 4801 KiB

Open AccessArticle

Conceptual Design and Feasibility Study of Winged Hybrid Airship

by Akshay Gangadhar, Murugaiah Manikandan, Dushhyanth Rajaram and Dimitri Mavris

Aerospace 2022, 9(1), 8; https://doi.org/10.3390/aerospace9010008 - 23 Dec 2021

Cited by 4 | Viewed by 5578

Abstract

In recent years, hybrid airships have been identified as promising alternatives for high altitude, long endurance missions. In this study, a design methodology to study the feasibility of a winged hybrid airship powered by solar energy is presented. The proposed methodology involves five [...] Read more.

In recent years, hybrid airships have been identified as promising alternatives for high altitude, long endurance missions. In this study, a design methodology to study the feasibility of a winged hybrid airship powered by solar energy is presented. The proposed methodology involves five disciplines of the airship, viz., geometry, aerodynamics, environment, energy and structures that have been coupled in order to develop an optimum design which incorporates the maximum advantages of the modules. A total of fourteen design variables have been finalized, which are required to carry out the sizing of the envelope, wing, and solar panel layout. The Particle Swarm Optimization (PSO) algorithm is implemented to carry out optimization of a user-defined fitness function for given user-defined operating conditions. The optimization study is subjected to general constraints of weight balance and energy balance. Optimal solutions have been obtained for two different configurations. These are—conventional airship and winged hybrid airship. The solutions have been obtained for four different days of the year, in order to analyse any potential benefits and pitfalls of the two configurations for the varying conditions over the course of one year. The results obtained are generally found to be in excellent agreement with the imposed constraints. The winged hybrid airship configuration was found to have offered no significant benefits in comparison to the conventional configuration. The analysis of the key parameters and data values readily supports this conclusion. Full article

(This article belongs to the Special Issue Advances in Aerospace Sciences and Technology II)

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36 pages, 1504 KiB

Open AccessFeature PaperArticle

On a Novel Approximate Solution to the Inhomogeneous Euler–Bernoulli Equation with an Application to Aeroelastics

by Dominique Fleischmann and László Könözsy

Aerospace 2021, 8(11), 356; https://doi.org/10.3390/aerospace8110356 - 22 Nov 2021

Cited by 2 | Viewed by 2649

Abstract

This paper focuses on the development of an explicit finite difference numerical method for approximating the solution of the inhomogeneous fourth-order Euler–Bernoulli beam bending equation with velocity-dependent damping and second moment of area, mass and elastic modulus distribution varying with distance along the [...] Read more.

This paper focuses on the development of an explicit finite difference numerical method for approximating the solution of the inhomogeneous fourth-order Euler–Bernoulli beam bending equation with velocity-dependent damping and second moment of area, mass and elastic modulus distribution varying with distance along the beam. We verify the method by comparing its predictions with an exact analytical solution of the homogeneous equation, we use the generalised Richardson extrapolation to show that the method is grid convergent and we extend the application of the Lax–Richtmyer stability criteria to higher-order schemes to ensure that it is numerically stable. Finally, we present three sets of computational experiments. The first set simulates the behaviour of the un-loaded beam and is validated against the analytic solution. The second set simulates the time-dependent dynamic behaviour of a damped beam of varying stiffness and mass distributions under arbitrary externally applied loading in an aeroelastic analysis setting by approximating the inhomogeneous equation using the finite difference method derived here. We compare the third set of simulations of the steady-state deflection with the results of static beam bending experiments conducted at Cranfield University. Overall, we developed an accurate, stable and convergent numerical framework for solving the inhomogeneous Euler–Bernoulli equation over a wide range of boundary conditions. Aircraft manufacturers are starting to consider configurations with increased wing aspect ratios and reduced structural weight which lead to more slender and flexible designs. Aeroelastic analysis now plays a central role in the design process. Efficient computational tools for the prediction of the deformation of wings under external loads are in demand and this has motivated the work carried out in this paper. Full article

(This article belongs to the Special Issue Advances in Aerospace Sciences and Technology II)

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15 pages, 7701 KiB

Open AccessArticle

Parametric Study of a Composite Skin for a Twist-Morphing Wing

by Peter L. Bishay and Christian Aguilar

Aerospace 2021, 8(9), 259; https://doi.org/10.3390/aerospace8090259 - 13 Sep 2021

Cited by 15 | Viewed by 3022

Abstract

Although the benefits of morphing wings have been proven in many studies in the last few decades, the wing skin design remains one of the challenges to advancing and implementing the morphing technology. This is due to the conflicting design requirements of high [...] Read more.

Although the benefits of morphing wings have been proven in many studies in the last few decades, the wing skin design remains one of the challenges to advancing and implementing the morphing technology. This is due to the conflicting design requirements of high out-of-plane stiffness to withstand aerodynamic loads and low in-plane stiffness to allow morphing with the available actuation forces. Advancements in the design of hybrid and flexible composites might allow for design solutions that feature this balance in stiffness required for this application. These composites offer new design parameters, such as the number of plies, the fiber-orientation angle of each ply in the skin laminate, and the spatial distribution of the plies on the skin surface. This paper presents a parametric study of a composite skin for a twist-morphing wing. The skin is made of periodic laminated composite sections, called “Twistkins”, integrated in an elastomeric outer skin. The twisting deformation is localized in the elastomeric sections between the Twistkins. The design parameters considered are the number of plies in the composite Twistkins, the fiber-orientation angle of the plies, the torsional rigidity of the elastomer, the width ratio, and the number of elastomeric sections. The computational analysis results showed that the torsional compliance can be increased by increasing the width ratio, decreasing the number of elastomeric sections, number of composite plies and the elastomer’s torsional rigidity. However, this would also lead to a decrease in the out-of-plane stiffness. The nonlinearity and rates at which these parameters affect the skin’s behavior are highlighted, including the effect of the fiber-orientation angle of the laminate plies. Hence, the study guides the design process of this twist-morphing skin. Full article

(This article belongs to the Special Issue Advances in Aerospace Sciences and Technology II)

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23 pages, 13516 KiB

Open AccessArticle

The Impact of Steady Blowing from the Leading Edge of an Open Cavity Flow

by Naser Al Haddabi, Konstantinos Kontis and Hossein Zare-Behtash

Aerospace 2021, 8(9), 255; https://doi.org/10.3390/aerospace8090255 - 09 Sep 2021

Cited by 7 | Viewed by 2611

Abstract

Cavity flows occur in a wide range of low-speed applications (Mach number

\leq 0.3

), such as aircraft wheel wells, ground transportation, and pipelines. In the current study, a steady jet is forced from a cavity leading edge at different momentum fluxes (0.11 [...] Read more.

Cavity flows occur in a wide range of low-speed applications (Mach number

\leq 0.3

), such as aircraft wheel wells, ground transportation, and pipelines. In the current study, a steady jet is forced from a cavity leading edge at different momentum fluxes (0.11 kg/ms

^{2}

, 0.44 kg/m·s

^{2}

, and 0.96 kg/m·s

^{2}

). The investigation was performed for an open cavity with length to depth ratio of 4 at the Reynolds number based on a cavity depth of approximately 50,000. Particle image velocimetry, surface oil flow visualisation, constant temperature anemometry, and pressure measurements were performed in this investigation. The aim of the jet blowing is to separate the cavity separated shear layer from the recirculation zone to reduce the cavity return flow, and hence stabilise the cavity separated shear layer. It was found that increasing the jet momentum flux causes an increase in the cavity return flow due to the increase in the thickness of the cavity separated shear layer. The study also found that the jet populates the separated shear layer with a large number of small-scale disturbances. These disturbances increase the broad band level of the pressure power spectra and Reynolds shear stress in the cavity separated shear layer. On the other hand, the jet disturbances make the shedding of the large vortical structures more intermittent. Full article

(This article belongs to the Special Issue Advances in Aerospace Sciences and Technology II)

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19 pages, 8370 KiB

Open AccessArticle

Investigation of Reynolds Number Effects on Aerodynamic Characteristics of a Transport Aircraft

by Yuanjing Wang, Dawei Liu, Xin Xu and Guoshuai Li

Aerospace 2021, 8(7), 177; https://doi.org/10.3390/aerospace8070177 - 01 Jul 2021

Cited by 4 | Viewed by 3991

Abstract

The scale difference between the real flight vehicle and the experimental model results in the Reynolds number effect, which makes it unreliable to predict the aerodynamic characteristics of flight vehicles by wind tunnel testing. To understand the mechanism of Reynolds number effects on [...] Read more.

The scale difference between the real flight vehicle and the experimental model results in the Reynolds number effect, which makes it unreliable to predict the aerodynamic characteristics of flight vehicles by wind tunnel testing. To understand the mechanism of Reynolds number effects on the aerodynamic characteristics of the supercritical wing that is commonly used in transport aircraft in more detail, surface pressure wind tunnel tests of a transport aircraft reference model with a wing-body configuration were conducted in the European Transonic Windtunnel (ETW) at different Reynolds numbers. There are 495 pressure taps in total equipped on the surface of the test model with the Mach numbers ranging from 0.6 to 0.86 and Reynolds number varying from 3.3 × 10⁶ to 35 × 10⁶. In addition, an in-house developed CFD tool that has been validated by extensive experimental data was used to correct the wing deformation effect of the test model and achieve detailed flow structures. The results show that the Reynolds number has a significant impact on the boundary layer displacement thickness, surface pressure distribution, shock wave position, and overall aerodynamic force coefficients of the transport aircraft in the presence of shock wave and the induced boundary layer separation. The wind tunnel data combined with flow fields achieved from CFD show that the essence of the Reynolds number effect on the aerodynamic characteristics of transport aircraft is the difference of boundary layer development, shock wave/boundary layer interaction, and induced flow separation at different Reynolds numbers. Full article

(This article belongs to the Special Issue Advances in Aerospace Sciences and Technology II)

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