Aeropropulsive Interactions Research Articles

Analysis, optimization, and testing of a tilt-body aircraft

This paper proposes a new multidisciplinary design optimization framework for tilt-bodies to obtain the optimal combination of geometry and powertrain, achieving both long endurance and low transition power consumption at a 5 kg takeoff weight. A low-fidelity vortex lattice method is used to derive the aerodynamic coefficients. The tandem wings are trimmed using an optimization-based method, considering the effect of distributed propulsion on the trim solution through aero-propulsive interaction at low flight speed. Detailed powertrain parameters are fitted with fewer design variables to calculate power consumption. By analyzing the unique constraints of tilt-bodies, the optimization problem is established as a simultaneous analysis and design architecture, and solved with different numbers of rotors. The impact of the relative geometric relationship between the front and rear wings on aerodynamic performance and constraints is analyzed. Results demonstrate the full angle-of-attack flight capability of tilt-bodies. The optimal design can save nearly 1000 W in transition, with a pure cruise endurance of over 1 hour, which is competitive among other configurations. With an empty weight of only 2 kg, a portion of the battery can be allocated to a heavier payload. High-fidelity computational fluid dynamics corrects the errors of the vortex lattice method on non-lifting components, including the fuselage, nacelles, and landing gear. Finally, the feasibility of the optimal design and the accuracy of the framework are validated by wind tunnel tests and in-flight drag measurements on a test platform.

Aero-Propulsive Interactions between UAV Wing and Distributed Propellers Due to Their Relative Position

The purpose of this paper is the evaluation of the aero-propulsive effects on a UAV wing model with distributed propulsion. An array of three propellers is placed ahead of the leading edge of a rectangular wing with flap. The investigation was performed with high-fidelity numerical analyses to provide insights into the phenomenology and to screen the interesting positions to be validated in the wind tunnel. The propellers’ array is moved into twelve different positions, allowing longitudinal and vertical translations. The wing has an untwisted and constant section profile, with a single slot trailing-edge flap that is deflected into three positions. The flap span is entirely covered by the propellers’ blowing. Results show an increment of lift, drag, and pitching moment coefficients with distributed propellers enabled. For a given thrust level, the magnitude of such increments depends on the propellers’ positions, the flap configuration, and the angle of attack. The lift enhancement sought in distributed propulsion applications comes at the expense of a significant increase in drag and pitching moment magnitude. In some combinations, the wing’s contribution to the aircraft longitudinal stability is severely affected. Conversely, the propellers’ inflow is altered such that thrust is increased in all the investigated configurations, with a small reduction of propulsive efficiency.

Design of hybrid-electric aircraft with fault-tolerance considerations

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.

Conceptual Design of Boundary-Layer-Ingesting Aircraft Capturing Aeropropulsive Coupling

The impacts of boundary-layer ingestion on aircraft performance can be modeled using either a decoupled or a coupled approach. Several studies in literature have adopted the former, whereas some have shown differences between the two approaches for the performance analysis and design refinement of a sized aircraft. This study quantifies the consequences of ignoring aeropropulsive coupling at the aircraft sizing stage of conceptual design. To do so, a parametric and coupled aeropropulsive design methodology is used that leverages surrogate modeling to minimize the expense of computational fluid dynamics in generating estimates of the boundary-layer ingestion performance impacts. The method is applied to the design and analysis of two aircraft in the 150 passenger class, with different engine locations. Discrepancies in block fuel burn estimates, as large as 2.15%, were found to occur by ignoring aeropropulsive interactions.

Aero-propulsive interaction model for conceptual distributed propulsion aircraft design

PurposeThis research aims to present an aero-propulsive interaction model applied to conceptual aircraft design with distributed electric propulsion (DeP). The developed model includes a series of electric ducted fans integrated into the wing upper trailing edge, taking into account the effect of boundary layer ingestion (BLI). The developed model aims to estimate the aerodynamic performance of the wing with DeP using an accurate low-order computational model, which can be easily used in the overall aircraft design's optimization process.Design/methodology/approachFirst, the ducted fan aerodynamic performance is investigated using a low-order computational model over a range of angle of attack required for conventional flight based on ducted fan design code program and analytical models. Subsequently, the aero-propulsive coupling with the wing is introduced. The DeP location chordwise is placed at the wing's trailing edge to have the full benefits of the BLI. After that, the propulsion integration process is introduced. The nacelle design's primary function is to minimize the losses due to distortion. Finally, the aerodynamic forces of the overall configuration are estimated based on Athena Vortex Lattice program and the developed ducted fan model.FindingsThe ducted fan model is validated with experimental measurements from the literature. Subsequently, the overall model, the wing with DeP, is validated with experimental measurements and computational fluid dynamics, both from the literature. The results reveal that the currently developed model successfully estimates the aerodynamic performance of DeP located at the wing trailing edge.Originality/valueThe developed model's value is to capture the aero-propulsive coupling accurately and fast enough to execute multiple times in the overall aircraft design's optimization loop without increasing runtime substantially.

Design of near-zero emission aircraft based on refined aerodynamic model and structural analysis

During recent years, aircraft manufacturers focused their attention on environmentally friendly and aerodynamically efficient aircraft concepts that could allow a radical reduction of emissions. The use of hybrid-electric powertrain is one of the most effective ways to design near-zero emission aircraft. These aircraft are highly performing and sophisticated. Hence, the design process must be extremely accurate and should make use of multidisciplinary design optimization. It is indeed crucial to establish both aerodynamic and structural models to simulate the aircraft performance and design required according to top level aircraft requirements. Despite the largely discussed literature about preliminary design of such an unconventional aircraft, there is still a lack of reliable weight estimation approaches, simulation-based mission analysis and optimization tools. In order to step towards higher technological readiness levels, the purpose of this paper is to describe and apply a design platform for conventional, turboelectric, hybrid-electric and full-electric aircraft, integrating aero-propulsive interactions, accurate power system modelling and medium-fidelity structural weight estimation. In particular, the comprehensive structural analysis of the aircraft wing opportunely designed according to certification specification and equipped with different powertrain architectures shows that it is worth looking into structural dynamics from preliminary design to estimate aircraft weight properly. Meanwhile, the mission analysis reveals performance benefits by implementing distributed engines all over the wingspan.

Benchmark of different aerodynamic solvers on wing aero-propulsive interactions

Distributed electric propulsion is a fertile research topic aiming to increase the wing aerodynamic efficiency by distributing the thrust over the wing span. The blowing due to distributed propulsors shall increase the wing lift coefficient for a given planform area and flight speed. This should bring several advantages as wing area, drag, and structural weight reduction, which in turn reduce fuel consumption, allowing airplanes to fly more efficiently. However, there are no consolidated preliminary design methods to size a distributed propulsion system. Numerical analysis is then performed at early stage, where many design variables have not been fixed yet. Therefore, the design space is vast and exploring all the possible combinations is unfeasible. For instance, low-fidelity methods (VLM, panel codes) have a low computational time, but usually they do not account for flow separation and hence they are unable to predict the wing maximum lift. Conversely, high-fidelity codes (CFD) provide more realistic results, but a single drag polar sweep can last days. This work provides a benchmark of different aerodynamic solvers for a typical regional turboprop wing with flaps and distributed propulsion, to better understand the limits of each software in the prediction of aero-propulsive effects.

Preliminary Design to Fulfil Future Market Demand of Electric Aircraft

The work introduces a preliminary design chain valid for hybrid-electric, full-electric, and thermal powered aircraft. From early stages of the design process, the integration of aero-propulsive interaction between propeller (or fan) slipstream and airframe is an important step to obtain trends and compare different aircraft. The present work integrates in the design chain both the distributed propulsion and tip-mounted propeller interactions, deriving for the latter effect a simple model suitable for point performance estimation. The research activity is oriented by market and political demands. Derived from these requirements, two different applications of the design process are proposed on FAR/CS-25 and FAR/CS-23 certified aircraft. Trends about the possible applications, benefits, and drawbacks show that, with the current technology state of the art, a full-electric aircraft is still unfeasible, unless a design range of 100 nmi is acceptable.

Comparative Assessment of Parallel-Hybrid-Electric Propulsion Systems for Four Different Aircraft

Until electric energy storage systems are ready to allow fully electric aircraft, the combination of combustion engine and electric motor as a hybrid-electric propulsion system seems to be a promising intermediate solution. Consequently, the design space for future aircraft is expanded considerably, as serial hybrid-electric, parallel hybrid-electric, fully electric, and conventional propulsion systems must all be considered. While the best propulsion system depends on a multitude of requirements and considerations, trends can be observed for certain types of aircraft and certain types of missions. This Paper provides insight into some factors that drive a new design toward either conventional or hybrid propulsion systems. General aviation aircraft, regional transport aircraft vertical takeoff and landing air taxis, and unmanned aerial vehicles are chosen as case studies. Typical missions for each class are considered, and the aircraft are analyzed regarding their takeoff mass and primary energy consumption. For these case studies, a high-level approach is chosen, using an initial sizing methodology. Only parallel-hybrid-electric powertrains are taken into account. Aeropropulsive interaction effects are neglected. Results indicate that hybrid-electric propulsion systems should be considered if the propulsion system is sized by short-duration power constraints. However, if the propulsion system is sized by a continuous power requirement, hybrid-electric systems offer hardly any benefit.

Preliminary Sizing Method for Hybrid-Electric Distributed-Propulsion Aircraft

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.