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... [9]. Cruise consisted of a constant altitude at h c =9,000 ft and constant velocity of V c = 228 ft /s flight, matching published data from the flight certification tests of the Tecnam P2006T [18]. A figure for cruise is not shown for the sake of brevity. Descent began with a constant altitude deceleration to the descent velocity, as shown in Fig. 4, and concluded when the aircraft reached both sea level and rotation velocity. Finally, Fig. 5 shows that landing roll concluded when the velocity of the aircraft reached zero. It was crucial that the simulation accurately represent the true performance of a Tecnam P2006T. The percent difference between published aircraft data and the ...
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The scope of the present paper is to assess the potential of distributed propulsion for a regional aircraft regarding aero-propulsive efficiency. Several sensitivities such as the effect of wingtip propellers, thrust distribution, and shape modifications are investigated based on a configuration with 12 propulsors. Furthermore, an initial assessmen...
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... Hence, a power management strategy is required, in order to effectively incorporate all the available media in the operational envelope [19]. Current attempts include constant splitting of power throughout the mission [20,21], assisting of the thermal engine during takeoff and climb with power provided by the electric component [22], as well as an assortment of rule-based approaches [23,24]. However, due to the nature of the problem at hand, optimizing the flow of power promises to maximize the potential of hybrid-electric propulsion [25,26] and allow for a fair evaluation of the new archetype [27]. ...
This study aims to illustrate a sequence that optimizes the flight-path trajectory for a hybrid-electric propulsion system at mission level, in addition to identifying the respective optimum power management strategy. An in-house framework for hybrid-electric propulsion system modeling is utilized. A hybrid-electric commuter aircraft serves as a virtual test-bench. Vectorized calculations, decision variable count and optimization algorithms are considered for reducing the computational time of the framework. Performance improvements are evaluated for the aircraft's design mission profile. Total energy consumption is set as the objective function. Emphasis lies on minimizing the average value and standard deviation of the energy consumption and timeframe metrics. The best performing application decreases computational time by two orders of magnitude, while retaining equal accuracy and consistency as the original model. It is employed for creating a dataset for training an artificial neural network against random mission patterns. The trained network is integrated into a surrogate model. The latter part of the analysis evaluates optimized mission profile characteristics with respect to energy consumption, against a benchmark flight-path. The combined optimization process decreases the multi-hour-scale timeframe by two orders of magnitude to a 3-minute sequence. Using the novel framework, a 12% average energy consumption benefit is calculated for short, medium and long regional missions, against equivalent benchmark profiles.
... Attempts at managing power flow for a hybrid-electric propulsion system consider a multitude of approaches. The simplest forms include constant power split strategies [4,5,10,11] or takeoff and climb assist by the batteries [8,9,12]. More intricate summaries classify power management strategies into categories [13][14][15]. ...
... Due to the concept being in early stages of development, smaller applications are mostly investigated. Research focuses on general aviation vehicles [6,11,[20][21][22] or commuter [12,18,23] and regional [4,5,24,25] aircraft. There are also instances of larger aircraft applications being considered [9,26]; although electrified propulsion still must overcome major barriers to be considered viable in such cases. ...
The present study deals with the optimization of performance for a hybrid-electric propulsion system. It focuses on the modeling and power management frameworks, while evaluation is done on a single flight basis. The main objective is to extract the maximum out of the novel powertrain archetype. Two hybridization factors are considered. The pair helps to describe the degree of hybridization at the power supply and power consumption levels. Their revised mathematical definition facilitates a unique method of hybrid-electric propulsion system modeling, that maximizes the conveyed amount of information. An in-house computational tool is developed. It employs a genetic algorithm optimizer in the interest of managing power usage during flight. Energy consumption is set as the objective function. The operation of a 19-seater, commuter aircraft is investigated. Turbo-electric, series-hybrid, parallel-hybrid and series-parallel variants are derived from a generic composition. An analysis on their optimized performance, with different technological readiness levels for 2020 and 2035, is aimed at identifying where each system performs best. Considering 2020 technology, it does not yield a viable hybrid-electric configuration, without suffering significant payload penalties. Architectures relying on mechanical propulsors show promise of 15% reduction to energy consumption, accounting for 2035 readiness levels. The concepts of Boundary Layer Ingestion and Distributed Propulsion display the potential to boost electrified propulsion. The series-hybrid and series-parallel configurations are the primary beneficiaries of these concepts, displaying up to 30% reduction in fuel and 20% reduction in energy consumption.
... In many cases, when the design process is analysed [18][19][20][21][22] , sometimes keeping the take-off weight constant in the hybridization process [23][24][25] , simplified assumptions are made on the powertrain system without modelling the relationship between the engine deck of the thermal power source and the power supplied by the electric power source. In other studies, generalised conceptual sizing methods for electric aircraft have been proposed without integrating the aero-propulsive interactions 19,25,26 . ...
The potential benefits of hybrid-electric or all-electric propulsion have led to a growing interest in this topic over the past decade. Preliminary design of propulsion systems and innovative configurations has been extensively discussed in literature, but steps towards higher levels of technological readiness, optimisation algorithms based on reliable weight estimation and simulation-based mission analysis are required. This paper focuses on the integration of a method for evaluating the lateral-directional controllability of an aircraft within a design chain that integrates aero-propulsive interactions, accurate modelling of the fuel system, and mid-fidelity estimation of the structural weight. Furthermore, the present work proposes a strategy for powerplant management in scenarios with an inoperative chain element. Benefits of hybrid-electric propulsion on the design of the vertical tail plane are evaluated involving the analysis of multiple failure scenarios and certification requirements. The proposed application concerns a commuter aircraft.
... Despite the large amount of ongoing research related to hybrid-electric distributed propulsion (HEDP), little information is available regarding the clean-sheet design process of such aircraft. As discussed in Ch. 2, several design studies analyze the hybridelectric powertrain in detail starting from a predefined aircraft configuration [45,66], often maintaining the take-off weight constant [113,204,205]. Other studies have formulated more generalized conceptual sizing methods for HEP aircraft [94][95][96][97][98][102][103][104], but do not integrate the aero-propulsive interaction effects in the process. ...
... The results indicate that the two HEP concepts present no benefit with respect to a conventional powertrain. This is in line with the findings of previous studies, which show that either more optimistic e bat values [45,78,79,119] or reduced ranges [66,115,204,205,213] are required for the HEP concepts to be competitive. However, the results obtained in this study are conservative for several reasons. ...
Recent developments in the field of hybrid-electric propulsion (HEP) have opened the door to a wide range of novel aircraft configurations with improved energy efficiency. These electrically-driven powertrains enable “distributed propulsion” configurations, in which the aerodynamic interaction between the propulsive devices and the airframe is exploited to enhance the aero-propulsive efficiency of the aircraft. In this context, the present research focuses specifically on over-the-wing distributed propulsion (OTWDP) for regional propeller aircraft. Over-the-wing (OTW) propellers are particularly promising because they can significantly enhance the lift-to-drag ratio of the wing, as well as reduce flyover noise due to shielding by the wing.
The objective of this research is therefore to quantify the impact of OTWDP on the energy efficiency of hybrid-electric aircraft. For this, the research is divided into three main parts. First, a sizing method for hybrid-electric distributed-propulsion (HEDP) aircraft is developed, independently of where the propellers are positioned with respect to the airframe. Second, the aerodynamic interaction effects and performance characteristics of OTWDP systems are investigated, independently of the type of powertrain used to drive the propellers. And third, the sizing method and aerodynamic performance estimates of the previous two points are combined to assess the effect of hybrid-electric OTWDP on aircraft-level performance metrics. [...]
... = slope of lift curve (two dimensions) C 1 -C 2 = empirical coefficients for internal combustion engine fuel flow rate C 3 = internal combustion engine lapse rate C 4 -C 5 = empirical coefficients for internal combustion engine lapse rate c = chord length, m D = drag, N D rod = diameter of supporting rod, m E = required energy, kWh F = Prandtl's tip loss function f e = equivalent flat plate area, m 2 H t = thruster drag force in disk plane, N I c = indicator function for battery charge I zz = moment of inertia with respect to z axis, mm 4 L = lift force, N LS = lift-sharing ratio l rod = length of supporting rod, m N b = number of blades N t = number of thrusters P = power, kW P c = battery-charging power, kW P HB = power obtained from battery, kW P HF = power obtained from hydrocarbon fuel, kW P IRP = intermediate rated power, kW P MCP = maximum continuous power, kW P total = total required power for aircraft, kW R = radius, m r = nondimensional radial span position S blown = wing area blown by propeller wake, m 2 T = thrust, N t = time, h V = velocity, m∕s V tip = velocity at thruster tip, m∕s v i = induced velocity, m∕s W = aircraft load, kg W empty = aircraft empty weight, kg _ W fuel = fuel flow rate to internal combustion engine, kg∕h α = angle of attack, rad β = velocity multiplier δ alt = ratio of atmospheric pressure at altitude to standard day sea-level pressure η = efficiency coefficient η safe = safety factor θ = collective pitch angle, rad θ alt = ratio of ambient temperature at altitude to standard day sea-level temperature θ i = incidence angle, rad λ = inflow velocity ratio λ c = climbing velocity ratio λ relax = relaxation factor ξ = percentage of engine power supplied to accessory items ρ = air density, kg∕m 3 σ = thruster solidity σ allow = allowable stress, Pa σ d = expansion ratio σ max = maximum stress, Pa σ yield = yield stress, Pa ϕ = induced angle of attack φ = power control ratio for internal combustion engine ...
... In the field of transport aircraft, research on hybrid-electric aircraft (HEA), which employ a hybrid-electric propulsion system (HEPS), has been actively conducted in recent years [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]. A HEPS is a propulsion system that combines electric and mechanical powertrains. ...
This paper proposes a conceptual methodology for designing vertical takeoff and landing aircraft with a hybrid-electric propulsion system as an alternative to facilitate intercity missions for urban air mobility. Four new modules are developed to consider the diversity of configurations, flight mechanisms, and hybrid-electric propulsion system architectures. The flight-analysis module is proposed to account for various lift- and thrust-generating devices. The hybrid-electric propulsion system sizing module is modified for the vertical takeoff and landing aircraft by additionally considering transition flight. Based on a new proposed battery charge/discharge criterion, the mission-analysis module is constructed to predict the battery capacity and fuel consumption required for a given mission. The weight-estimation module is also developed considering the weight of the mechanical and electric powertrains. The proposed methodology is demonstrated by designing an urban air mobility vehicle and comparing the results with those of other sizing tools. A systematic comparative study and design optimization are carried out to highlight the improvement in the performance of the hybrid-electric-powered vertical takeoff and landing aircraft compared to its battery-driven counterpart. The extended mission range of the designed aircraft presents the possibility of intercity urban air mobility vehicles.
... Despite the large amount of ongoing research, still, poor results are available for a simulation-based mission analysis of electric distributed propulsion airplanes. In many cases, only the design process is analyzed [1][2][3][4][5], sometimes keeping the take-off weight constant in the hybridization process [6][7][8]. In other studies, generalized conceptual sizing methods for EP aircraft, which do not integrate the aero-propulsive interaction effects, [2,8,9], have been proposed. ...
The potential benefits of hybrid-electric or full-electric propulsion have led to an increased interest in this topic over the past decade. Hence the need to develop modern and innovative methods to analyze the performance of aircraft with unconventional propulsion systems. The purpose of this paper is to describe and apply a simulation-based algorithm integrating aero-propulsive effects for the mission analysis of conventional, hybrid-electric, and full-electric aircraft. The method composes the analysis toolbox of the aforementioned software, HEAD (Hybrid-Electric Aircraft Designer), developed by the DAF Research Group. Analysis toolbox has to perform a detailed mission simulation of a generic airplane. The proposed application deals with the evaluation of the effects on performance that wingtip-mounted propellers and distributed electric propulsion on regional turboprop category. The reference aircraft is similar to an ATR-42.
... Several academic authors have conducted one-off studies on general aviation and commuter aircraft [97][98][99][100]. Others focused on small unmanned aerial system (UAS), such as the early work at the Air Force Institute of Technology by Harmon et al. [21,101,102] and one study of a UAS propulsion subsystem by Merical et al. [103]. ...
Electric aircraft propulsion is an intriguing path towards sustainable aviation, but the technological challenges are significant. Bulky and heavy electrical components such as batteries create spatial integration and aircraft performance challenges, especially for longer-range aircraft. A common thread among all aircraft with electric propulsion is the close coupling of aircraft design disciplines, such as aerodynamics, structures, propulsion, controls, and thermal management. Multidisciplinary design optimization (MDO) is a promising technique for solving design problems with many closely-coupled physical disciplines. The first half of this dissertation focuses on MDO of electric aircraft considering systems modeling. First, design of electric aircraft is reviewed in detail from the perspective of the various disciplines. Next, methods and models for electric aircraft propulsion systems are introduced. A case study involving a general aviation airplane is explored in order to validate the performance of the methods and generate some insight into the tradespace for series hybrid aircraft. The systems modeling approach is then extended to include basic thermal management systems. The prior case study is revisisted while considering thermal constraints. Impact of thermal management on aircraft performance is assessed. The thermal management analysis methods are validated using flight test data from the Pipistrel Velis Electro, finding good agreement between experiment and simulation. Finally, an MDO model of a parallel hybrid electric transport aircraft with a liquid-cooled thermal management system is constructed. Sensitivities of aircraft performance with respect to important technologies parameters are computed. This first half introduces the first publicly-available simulation tool that can handle unsteady thermal states and that offers efficient and accurate gradients. The methods are very efficient, enabling users to perform dozens or hundreds of optimization runs in a short amount of time using modest computational resources. Other novel contributions include the first empirical validation of thermal management models for MDO against real flight test data, as well as the only comprehensive look so far at the unsteady thermal management of a transport-scale parallel hybrid aircraft. The second half of the dissertation introduces novel methods for performing high-fidelity shape optimization studies subject to packaging or spatial integration constraints. A new mathematical formulation for generalized packaging constraints is introduced. The constraint formulation is demonstrated on simple aerodynamic shape optimization test cases. Next, a wing design study involving optimal battery packaging is conducted in order to demonstrate the coupling of outer mold line design and propulsion system component design via spatial integration. Finally, a more complex aerostructural optimization involving the wing of a hydrogen aircraft is constructed and solved. These test cases demonstrate the interdisciplinary coupling introduced by packaging constraints, as well as the impact of spatial integration on aircraft performance. This latter half contributes a powerful new way for MDO engineers to pose realistic spatial constraints in their shape optimization problems, thus solving an important practical barrier to the industrial adoption of MDO for certain relevant problems. This work also represents the first time an MDO problem has been posed and solved for an aircraft using hydrogen fuel in the wing. Altogether, this dissertation significantly advances the state of the art in modeling, simulation, and optimization tools for aircraft with electric propulsion architectures and introduces new insights into the design spaces for several diverse aircraft configurations.
... BHL conceptualized studies have pronounced a desirable SE in the range of 1000-1500 Wh/kg for HE applications in single-aisle segments [40,121]. The desired level varies based on the type of propulsion system configuration, airframe morphology, size of the aircraft, degree of hybridization, and the flown mission range [225]. The NAEreport made a consensus effort in defining the least desired SE in three different segments of aircrafts: 1. 250 Wh/kg in a fully electric general aviation aircraft, 2. 800 Wh/kg in a HE regional aircraft, and 3. 1800 Wh/kg for a fully electric regional aircraft [19] . ...
Electrification of the propulsion system has opened the door to a new paradigm of propulsion system configurations and novel aircraft designs, which was never envisioned before. Despite lofty promises, the concept must overcome the design and sizing challenges to make it realizable. A suitable modeling framework is desired in order to explore the design space at the conceptual level. A greater investment in enabling technologies, and infrastructural developments, is expected to facilitate its successful application in the market. In this review paper, several scholarly articles were surveyed to get an insight into the current landscape of research endeavors and the formulated derivations related to electric aircraft developments. The barriers and the needed future technological development paths are discussed. The paper also includes detailed assessments of the implications and other needs pertaining to future technology, regulation, certification, and infrastructure developments, in order to make the next generation electric aircraft operation commercially worthy.
... Despite these drawbacks, this architecture is the one that is closer to the conventional configurations due to the possibility for low values of power hybridization. Therefore, it is the one that is the easiest to implement on the near future (DEAN et al., 2018). ...
... Starting with the paper by Dean et al. (2018), the authors simulate the Series Hybrid and Parallel Hybrid networks applied on a twin engine general aviation aircraft and compare their performance with the conventional piston engine version. ...
... This study by Dean et al. (2018) is very important in showing the challenges and drawbacks of using battery as an energy source on aircraft, specially if it is used on all flight phases. Simply switching from fuel to batteries without any other consideration, such as it was proposed in the paper, is bound to drastically reduce aircraft capabilities. ...
There is an always increasing demand for more efficient aircraft due to both economic and environmental purposes. Civil Aviation is responsible for around 4% of global carbon dioxide emissions, with this number bound to go up to 10% due to the increasing demand for transportation.
Since conventional aircraft and engine technologies are already well established and are reaching an efficiency ceiling, academy and industry are turning towards different approaches by studying hybrid-electric and full-electric concepts to explore new aircraft design opportunities.
A study is made using an aircraft with a conventional propulsive system as a baseline and introducing two new concepts to it: hybrid-electric propulsion and the use of high lift propellers. The hybrid propulsion acts as an enabler to high lift propellers, which has a great potential to increase overall aircraft efficiency and reduce fuel burn, so its effects on the design and performance of the aircraft are investigated and compared to the baseline vehicle.
For that goal SUAVE, an aircraft conceptual design environment, is used to size the aircraft, estimate weights, performances, and run the mission.
Different weight estimation and steady state efficiency models are implemented on this tool to evaluate the operation and performance of the propulsive system on the various flight phases.
Furthermore, a simplified aerodynamic model to estimate the effects of high lift propellers on the wing is also implemented, making the connection between the propulsive system and lift augmentation on the sizing and performance analyses of the aircraft.
... Despite the large amount of ongoing research related to hybrid-electric propulsion, little information is available regarding the clean-sheet design process of HEDP aircraft. In many cases, design studies analyze the hybrid-electric powertrain in detail starting from a predefined aircraft configuration [12,16,17], often maintaining the take-off weight constant [18][19][20]. Other studies have formulated more generalized conceptual sizing methods for HEP aircraft [20][21][22][23][24][25][26][27][28], but do not integrate the aero-propulsive interaction effects in the process. ...
... The results indicate that the two HEP concepts present no benefit with respect to a conventional powertrain. This is in line with the findings of previous studies, which show that either more optimistic e bat values [9,12,22,44] or reduced ranges [8,[17][18][19]25] are required for the HEP concepts to be competitive. However, the results obtained in this study are conservative for several reasons. ...
The use of hybrid-electric propulsion (HEP) entails several potential benefits such as the distribution of power along the airframe, which enables synergistic configurations with improved aerodynamic and propulsive efficiency. This paper presents a comprehensive preliminary sizing method suitable for the conceptual design process of hybrid-electric aircraft, taking into account the powertrain architecture and associated propulsion–airframe integration effects. To this end, the flight-performance equations are modified to account for aeropropulsive interaction. A series of component-oriented constraint diagrams are used to provide a visual representation of the design space. A HEP-compatible mission analysis and weight estimation are then carried out to compute the wing area, powerplant size, and takeoff weight. The resulting method is applicable to a wide range of electric and hybrid-electric aircraft configurations and can be used to estimate the optimal power-control profiles. For demonstration purposes, the method is applied to a regional HEP aircraft featuring leading-edge distributed propulsion (DP). Three powertrain architectures are compared, showing how the aeropropulsive effects are included in the model. Results indicate that DP significantly increases wing loading and improves the cruise lift-to-drag ratio by 6%, although the growth in aircraft weight leads to an energy consumption increase of 3% for the considered mission.
