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Challenging emission reduction targets and significant growth of air transport market
motivate important research of novel propulsion systems with alternative energy sources and
lowered CO2 emissions. For short regional flights, hybrid-electric turboprop is seen as a
promising alternative to reduce fuel burn. As conventional propulsion aircraft, hy...
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Context 1
... Motion Global aircraft mission performance is evaluated by timemarching reverse simulation to analyse energy consumption from given mission ( Figure 3). Aircraft is simulated using a point-mass model in steady state ( Figure 4). Transient dynamics are not considered, hence transitions between missions phases are assumed to be instantly applied at conceptual level. ...
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[Purpose] - Parallel hybrid electric propulsion retrofit is a promising alternative to reduce fuel burn of aircraft operating on short regional flights. However, if the batteries are depleted at the end of the mission, the hybrid powertrain designs with downsized gas turbines and additional electric motors might not meet the one engine inoperative...
Citations
... Moreover, electric energy usage also depends on powertrain design, mission stage and scenarios. Quillet et al. [20,21] assessed the impact of electric assistance requirements during the OEI scenario at the end of the mission on potential fuel burn reduction during the mission if the gas turbine is downsized. The study showed that the electrical branch should be prioritized during the main mission to reduced fuel consumption while the thermal engine branch should be sized to ensure flight capability during emergency scenarios such as OEI with no electric assistance. ...
... A mission analysis framework is used to evaluate aircraft performance over various operating conditions. This conceptual-level code was developed to explore the hybrid electric propulsion design and its performance over a large range of input parameters [20]. The analysis performs time marching inverse simulations to estimate power and energy usage at drivetrain from a specified mission profile divided in phases. ...
... As pointed in [25], keeping the original GT size offers the possibility to plan mission without battery provision for alternates, to operate the aircraft without electric power, and provide better airworthiness margin for certification. Also, as stated in previous studies [20,21], maintaining the original GT eliminates the need to maintain charged batteries in the unlikely OEI emergency climb during a flight diversion to an alternate airport. As GT size is maintained as original, OEI climb gradients are not evaluated because they conform at a minimum to original aircraft performance. ...
Hybrid electric propulsion is one of the alternative solutions for reducing fuel burn and lower [Formula: see text] emissions while keeping a reasonable battery mass for regional turboprop aircraft operating on short routes. Most studies reporting fuel burn reductions evaluate the aircraft on the design mission, although regional transport aircraft rarely operate under these conditions. Therefore, considering its off-design performance is essential for providing a more complete understanding of aircraft capabilities under various operating conditions. Under these flight conditions, the multi-energy management aspect of hybrid propulsion and the fixed size of the batteries could have a significant impact on the system robustness in off-design operation. In this study, the off-design performance of an existing regional turboprop aircraft retrofitted with a parallel hybrid electric powertrain is assessed. Fuel burn benefits are evaluated on the payload–range diagram for an initial hybrid design and compared to the baseline aircraft. Then, using a novel sizing approach, considering a typical mission operation, this study shows an average improvement of [Formula: see text] percentage point on fuel burn benefits relative to the initial hybrid aircraft, creating a more robust design.
... The concept of operations for the hybrid turboprop studies considered in several references [14][15][16][17][18][19] and this paper aims at down-sizing the core, which means to improve gas turbine efficiency and/or weight in some way. One way is to apply electric boost during take-off and climb, such that all energy for cruise is supplied by on-board fuel. ...
... Quillet et al. [19] offset their original efficiency map relative to GT size expressed by its maximum takeoff power rating. Like this, lower GT size will translate into lower overall GT efficiency. ...
... where it is estimated that the Dash 8-300 burns 1,414 lb of fuel ( ℎ , ) to complete the mission at maximum payload [27]. The proposed powertrain design is tested across the 30,276 simulated combinations. ...
Electric motorization of landing gear appears to be one of the alternative solutions to reduce fuel burn, carbon dioxide emissions, and noise during the taxi phase. Because turboprop aircraft operate on short routes, the taxi phase represents an important part of both flight time and fuel consumption. An electric taxiing system (ETS) sized to meet current operational practices could reduce the fuel consumption and remain nearly transparent to the pilots. This paper first presents a statistical approach to define the taxiing requirements for regional turboprop aircraft using 200 taxi phases of 77 aircraft. Requirements of [Formula: see text] maximum acceleration until 15 kt, a 25 kt top speed, and a 13,000 ft distance (including taxi-in and taxi-out) are determined in accordance with the analysis, operational practices, and pilots’ routines. For a speed higher than 15 kt, the acceleration requirement is adjusted using the isopower to limit the mass of the ETS. Then, an ETS with sufficient performance is sized to be integrated in the main landing gear of a regional turboprop aircraft (Dash 8-300). For a standard mission of 270 nautical miles, the expected fuel economy is 3.1% for a payload loss of 2.2% or 1.3 passengers due to the system weight.
... La performance en mission est évaluée à l'aide d'un environnement d'analyse de mission développé sur MATLAB, présenté à la figure 4. 8. Cet environnement permet le dimensionnement préliminaire et la simulation temporelle itérative de l'opération de l'avion sur une mission prédéfinie découpée en phases [101]. ...
... The conceptual level framework combines overall sizing and operation effects on aircraft performance for the two hybrid design considered. The chosen modelling approach is based upon low fidelity models used to compute time marching inverse simulation with a steady state energy approach on a point mass aircraft [101] . From prescribed kinematics, the power chain is computed upstream to monitor the total energy consumption at sources. ...
... Moreover, electric energy usage also depends on powertrain design, mission stage and scenarios. Quillet et al. [101] assessed the impact of electric assistance requirements during the OEI scenario at the end of the mission on potential fuel burn reduction during the mission if the gas turbine is downsized. The study showed that the electrical branch should be prioritized during the main mission to reduced fuel consumption while the thermal engine branch 7.1. ...
D’importants efforts de recherche sont aujourd’hui déployés afin de réduire la consommation en carburant des avions en vue de minimiser l’impact environnemental du secteur aérien. L’hybridation électrique du système propulsif constitue une alternative d’intérêt qui ouvre un large spectre de configurations possibles et permet le développement incrémental et donc à plus faible risque. L’aviation régionale turbopropulsée est une application de choix pour la diffusion de cette technologie dans un horizon proche considérant les niveaux de puissance réduits par rapport aux avions de transport commercial utilisant des soufflantes. Ainsi, un concept d’avion régional à propulsion hybride électrique parallèle est
étudié pour des opérations de courte distance.
La propulsion hybride introduit des degrés de liberté additionnels et augmente la complexité du problème de conception. Les niveaux d’hybridation en puissance et en énergie sont à considérer au même titre que la stratégie de gestion de puissance qui les relie. Dans le même temps, le concept d’avion hybride doit être en mesure de respecter les requis de la réglementation relatifs aux réserves et les scénarios d’urgence. Pourtant, les travaux passés font usage d’hypothèses optimistes, ne permettant pas de saisir l’impact d’une propulsion hybride sur une application concrète. Ce travail de thèse a pour objectif d’analyser les bénéfices potentiels du concept d’avion hybride autour d’un avion existant remotorisé. L’approche utilisée intègre l’ensemble des degrés de liberté en apportant des éléments de réalité opérationnelle, tels que la panne moteur ou l’enveloppe de performance, tout en considérant des projections technologiques de batteries réalistes à 2030.
Premièrement, l’étape initiale du travail repose sur le développement d’un environnement d’analyse multimission et d’optimisation de niveau conceptuel, adapté à l’implémentation de systèmes de propulsion hybrides.
Deuxièmement, une analyse comparative des principales stratégies d’opération hybride en mission est réalisée par analyse de simulation sur l’avion et la mission de référence en appliquant une technologie de batterie de 241 Wh/kg. Des gains de carburant jusqu’à 6% sont estimés et comparés aux résultats de la littérature.
Troisièmement, l’impact des requis de certification sur les gains potentiels en carburant est évalué par optimisation de l’hybridation et de la stratégie d’opération pour minimiser la consommation en carburant. Une approche de sous-dimensionnement de la turbine à gaz et une autre qui conserve la turbine d’origine sont comparées relativement au scénario d’urgence, soit une panne moteur lors d’une montée à la fin d’un vol. La contrainte de certification réduit de 12.6% les gains possibles. Ceux-ci sont finalement identiques à l’approche conservant la turbine d’origine et estimés à 5.1%.
Finalement, les gains de carburant sont évalués sur une large plage de conditions de vol par optimisation de l’opération, permettant de visualiser l’impact de la masse constante des batteries. Une méthodologie de dimensionnement est proposée afin d’adapter la conception aux réalités opérationnelles et augmenter la robustesse de performance de l’appareil avec une augmentation moyenne de +1 point de pourcentage des gains de carburant sur toute l’enveloppe de performance.
... The conceptual level framework combines overall sizing and operation effects on aircraft performance for the two hybrid design considered. The chosen modelling approach is based upon low fidelity models used to compute time marching inverse simulation with a steady state energy approach on a point mass aircraft (Quillet et al. 2021) . From prescribed kinematics, the power chain is computed upstream to monitor the total energy consumption at sources. ...
[Purpose] - Parallel hybrid electric propulsion retrofit is a promising alternative to reduce fuel burn of aircraft operating on short regional flights. However, if the batteries are depleted at the end of the mission, the hybrid powertrain designs with downsized gas turbines and additional electric motors might not meet the one engine inoperative missed approach climb performance required by the certification. Alternatively, hybrid designs using the original full-size gas turbine can perform one engine climb without electric assistance. This paper aims to evaluate the impact of overshoot climb requirements on powertrain design and performance comparing the two design approaches.
[Design/methodology/approach] - An aircraft level parametric mission analysis model is used to evaluate aircraft performance combined with an optimization framework including multiple constraints. An indirect approach is used to optimize powertrain sizing and operation strategy using metamodels.
[Findings] - Considering OEI climb requirements, no benefits were found using a design with downsized gas turbines. Equivalent fuel burns were found for hybrid designs that keep the original size gas turbine, but do not require electric energy for the OEI overshoot at the end of mission. Then, it is recommended to size the gas turbine to maintain the emergency climb capabilities with no electric assistance to ensure power availability regardless of remaining battery energy.
[Originality/value] - This work introduces a new perspective on parallel hybrid electric sizing with consideration for the dependency of power capability at aircraft level on the electric energy availability in case of critical mission scenarios such as overshoot climb at end of mission.
... Depending on the utilization of energy sources and the connectivities between energy sources and power sources, EAP can be categorized into all-electric propulsion (EP), turbo-electric propulsion (TEP), and hybrid-electric propulsion (HEP). Preceding studies have indicated that HEP can reduce the fuel consumption for the regional aircraft with 50 to 70 seats and may provide the opportunity to revive the regional air transportation used to be operated by turboprop aircraft [4][5][6]. Meanwhile, due to the scale invariance of electric motors with respect to efficiency and power-to-weight ratio, EAP enables novel approaches to position the propulsor in a synergistic location to complement the propulsion-airframe interactions [7]. ...
View Video Presentation: https://doi.org/10.2514/6.2022-3204.vid The Parallel Electric-Gas Architecture with Synergistic Utilization Scheme (PEGASUS) is a regional aircraft concept developed by NASA’s Aeronautics Systems Analysis Branch to explore the opportunities created by the technology of electric aircraft propulsion. It features a distributed parallel hybrid-electric propulsion architecture with two wingtip-mounted hybrid-electric propulsors, two inboard electric motors, and one aft boundary layer ingestion electric motor. Although PEGASUS has been demonstrated to have advantages in fuel burn and energy consumption over conventional aircraft in preceding studies, it may encounter difficulties in complying with critical-engine-inoperative flight certification rules due to the extreme locations of the wingtip-mounted propulsors. Using a certification-driven design framework, this paper presents a vertical tail sizing and propulsive power split optimization study for the PEGASUS concept incorporating certification requirements. For comparison, a vertical tail retrofit study is also conducted on the ATR 42-500 aircraft, which serves as the conventional baseline of the PEGASUS, using the same design space, to gain insights into the different impacts of certification constraints on the design process between conventional and unconventional aircraft. In each study, a design space exploration is performed by sampling the design space using a Design of Experiments, constructing surrogate models for responses of interests including design objectives and constraints, filtering the design space based on its feasibility with respect to constraint functions, and identifying a set of Pareto optimal candidates through a Monte Carlo simulation. The feasibility test shows that the certification constraints yield a much smaller feasible design space for the PEGASUS aircraft when compared to the ATR 42. The comparison between the unconstrained and constrained optima implies that performance improvements induced by novel technologies are negatively correlated to design constraints. Despite a much smaller feasible design space, the constrained Pareto optima of the PEGASUS still exhibit lower cruise drag coefficient, fuel burn, and operational energy cost when compared to those of the ATR 42.
... The search for the best configurations remains an important issue to identify the most efficient solutions. It must be based on optimization methods with multiple objectives and dimensioning tools to assess the behaviour of the entire propulsion system during a typical mission [4][5][6]. In this case, it is necessary to take into account various physical phenomena and to make compromises on the granularity of certain models to carry out the design analyses in a reasonable time. ...
... In this work, we compare two optimization methods for the design of Halbach array PMSM for the parallel-hybrid powertrain of a regional aircraft [6]. First, an analytical sizing Halbach array PMSM model is presented and used in a Space Mapping (SM) optimization process. ...
... This section shows an example of a PMSM design problem for an aircraft application [6]. The main challenge is to maximize motor power density and efficiency. ...
Effective methods for the design of high-performance electrical machines must use optimization techniques and precise and fast physical models. Convergence, precision and speed of execution are important issues, in addition to the ability to explore the entire domain of solutions. The finite element method (FEM) presents a high accuracy in the results but with high computational costs. Analytical models, on the other hand, solve the problem quickly but compromise the accuracy of the results. This work shows a comparison between an optimization made with an analytical electromagnetic model and a direct optimization with finite element field calculation for the optimal design of a Halbach array permanent magnet synchronous motor (PMSM). In the case of the analytical model, it is necessary to use an iterative method of correcting the model to obtain a valid solution. This method is known as Space Mapping (SM) and the analytical model can be improved with a reduced number of iterations with the FEM. The results show a rapid convergence towards an optimal solution for the SM, with more than 78% reduction in computational cost compared to a Direct FEM optimization. Both solutions have only a difference of 3% on the power density, which indicates that FEM does not improve the results obtained by SM. This represents a great advantage that allows for the consideration of a large amount of designs to analyze the domain of solutions in more detail. This study also shows that SM is a powerful method to optimize the power density or torque density of electrical machines.
... 2) Hybrid climb and cruise phases throughout a mission based on the HEPOS framework [13]. ...
... Finally, the power chain is computed through the powertrain component efficiencies for each of the two powertrains to monitor the total energy consumption at sources. Based on associated study [13], the EM size is established as 160 kW for a Montreal-Toronto based mission. Section III will present the morphological matrix and the resulting architectures. ...
... 4) The aircraft is filled to MTOW with fuel or battery while meeting the fixed design payload. Table 2, the optimization was done regarding the operation of the powertrain, but most design parameters were fixed based on previous work [13]. ...
View Video Presentation: https://doi.org/10.2514/6.2021-2444.vid With increasing CO2 emissions, the parallel hybrid electric propulsion configuration is expected to be a viable solution to reduce fuel burn in the aviation sector. Coupling an electrical machine (EM) to an existing gas turbine (GT) is complex since the design is intertwined with its operation even when the thermodynamic cycle of the turbine is unaffected because the EM is connected to the existing gearbox. Previous studies considered the benefits of EMs, but not the integration challenges to use them for various operations such as propeller-driven etaxi and hybrid climb and cruise phases. Numerous design choices are investigated from a system-level perspective: the EM topology, the EM design speed, the use of a clutch and if so, its position relative to the EM. Combining those design choices resulted in 18 possible powertrain architectures. The main design criteria considered in this study were minimizing fuel burn, minimizing the powertrain mass and respecting minimum taxiing responsiveness. Based on these criteria, the optimum architecture was found to be a high speed permanent magnet synchronous motor (PMSM) without any clutch.
Recently, aircraft engine manufacturers have shown increased interest in developing hybrid powerplants, which are a combination of gas turbine engines (GTE) with electric motor-generators. The use of the hybrid powerplant makes it possible to increase the fuel efficiency of an airplane, as well as to create new configurations with improved aerodynamic and thrust characteristics. The fuel efficiency improvement is achieved as a result of optimizing the powerplant operation mode to meet the cruising flight requirements, compensating insufficient power during the takeoff and go-around procedures by activating battery-powered electric motors. The creation of new configurations with improved performance can be ensured due to the synergetic effect of the propeller-airframe interaction. Successful flight tests of the hybrid powerplant prototypes in light aircraft configurations allow us to rely on their possible application in the future regarding the projects of new propeller-driven aircraft. The potential benefits of using new powerplants on local airlines can lead to both fuel savings and carbon emission reduction. Short-term maintaining a safe flight mode is also practical in case of one engine failure when using multiple power sources. The power, generated by an electric generator connected to the running engine, can be used both for the electric motor drive of the tip propellers and for rotating the thrust producer of the failed engine. The paper presents the study results of the critical engine failure effect on the aerodynamic performance of the light transport aircraft model obtained as under available electrical transmission as under non-available one between a running and a failed engine. Experimental studies were carried out in a low-speed wind tunnel T-102 TsAGI. The simulation of the electric transmission operation was carried out by setting the operation mode of two power-plant simulators corresponding to the half value of the load factor of one engine propeller B o in the take-off mode.
