The electrification of the commuter aircraft is instrumental in the development of novel propulsion systems. The scope of this work aims to explore the design space of a parallel hybrid-electric configuration with an entry into service date of 2030 and beyond and determine the impact of other disciplines on conceptual design, such as components positioning, aircraft stability and structural integrity. Three levels of conceptual sizing are applied and linked with a parametric aircraft geometry tool, to generate the aircraft’s geometry and position the components. Subsequently, the structural optimisation of the wing box is performed, providing the centre of gravity of the components placed inside the wing, that minimise the induced stresses. Furthermore, the stability and trim analysis follow, with the former being highly affected by the positioning of components. Results are compared to a similar aircraft with entry into service technology of 2014 and it is indicated that in terms of block fuel reduction the total electrification benefit increases with the increase of degree of hybridisation, if aircraft mass is kept constant. On the other hand, if battery specific energy is kept constant, similar block fuel reduction is possible with lower hybridisation degrees. The potential for improvement in terms of carbon dioxide emissions and block fuel reduction ranges from 15.73% to 21.44% compared to the conventional aircraft, for levels of battery specific energy of 0.92 and 1.14 kWh/kg respectively. Finally, the component positioning evaluation indicates a maximum weight limitation of 240 kg for the addition of an aft boundary layer ingestion fan to a tube and wing aircraft configuration, without compromising the aircraft static stability.

The electrification of aircraft is an on-going endeavor, currently examined intensively in the general aviation class. However, for the commuter class, the proper selection of the hybrid-electric propulsive architecture is instrumental, to fully exploit the electrification benefit. Within this work, a comparison of two 19-seater aircraft with different hybrid-electric propulsive components is made, using an in-house aircraft conceptual design tool. The first aircraft is based on a twin-turboprop parallel-hybrid configuration that cruises at low Mach number speeds and altitude. On the other hand, the second aircraft variant is based on a tri-fan series/parallel-hybrid configuration with an aft Boundary Layer Ingestion system that operates at both higher altitude and Mach numbers. A design space exploration is performed where different degrees of hybridization and batteries specific energy are considered, to define the technological requirements for each architecture. The evaluation of the propulsive architectures is based on block fuel reduction, overall mission duration, direct operating costs and total environmental impact. The results aim to quantify the benefits of each configuration and determine the one with the closest entry into service. Finally, it is observed that the overall environmental impact reduces by 26 % and 17 % for the turboprop and turbofan variants respectively.

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.

Hybrid-electric commuter aircraft segment is playing a significant role in the electrification of air transportation. Towards the achievement of efficient and robust transportation, design and optimization processes are necessary to evaluate the different aircraft components. Within this context, the current work investigates the impact of the positioning of the propulsion system and spars on the structural integrity of a hybrid-electric commuter aircraft. The proposed approach is based on an in-house aircraft sizing tool, along with geometry generation and high-fidelity structural evaluation models. These tools are tailored in an automated computational pipeline, that includes pre-processing, model evaluation and post-processing tasks, able to perform design space exploration and optimization over different loading conditions of a selected mission envelope. This work focuses on the assessment of the impact of the additional non-structural weight e.g., batteries, fuel, and propulsion components, inside the wing box, on the stress, deformation and spanwise thickness distribution of the structure. The effect of spars and propulsion system positioning on the available storage space, maximum stress and displacement is discussed, with the aft spar having the greatest impact. Finally, the structural model is optimized to minimize the mass, resulting in a 29% weight reduction, compared to the initial design.

A numerical analysis based on Computational Fluid Dynamics (CFD) is carried out to investigate the influence of the fuselage transition and axial offset, on the inlet distortion and performance of a tail mounted fan, for a short-haul commuter aircraft. For the examined configurations, it is predicted that varying the angle of the fuselage transition does not have a significant impact on the radial distortion, for a typical fan mounted at the centreline of the fuselage. The wake behind the fuselage is predicted to increase in size as the slope of the fuselage is increased, however, the positive suction from the fan is sufficient for the flow to fully recover before the fan duct inlet. Nevertheless, it is predicted that offsetting the fan from the fuselage centreline produces a more significant increase in distortion in the circumferential direction. The propulsive power of the fan is predicted to increase slightly with increasing offset mainly due to the side of the fan which is less obstructed by the fuselage. However, the wake on the opposite side is predicted to increase significantly persisting almost to the inlet of the fan duct. A vortex formed upstream of the fan increases in strength with increasing offset. This vortex helps to offset the increase in circumferential distortion by re-energizing the flow in the wake of the fuselage. This causes the circumferential distortion to remain roughly constant between offsets of 25% and 50% of the fuselage radius. It is likely though that this vortex will deteriorate the performance of the fan.