Preliminary weight sizing of light pure-electric and hybrid-electric aircraft

Abstract The lack of consolidated preliminary design techniques coping with the characteristics of most recent electric and hybrid-electric power plants is often an obstacle for aircraft manufacturers and for owners and operators as well, making the design process less straightforward and hampering comparisons with respect to more traditional designs. In this paper, a technique for the preliminary weight sizing of electric aircraft in the General Aviation category is explained. This is based on existing procedures typical to conventionally-powered aircraft, integrated in a common framework to suitably tackle the issues raised by the peculiar features of electrically-powered aircraft. Then, an expansion of the design method to the case of a series hybrid propulsion system is investigated. Results in virtual environment on a realistic design are also presented

Inertial and aerodynamic tuning of passive devices for load alleviation on wind turbines

This paper describes tuning concepts for passive devices aimed at load alleviation in wind turbines. Two types of tuning are considered: inertial and aerodynamic. The first concept is illustrated with reference to a passive flap, while the second with reference to a passive tip. In both cases, the goal is to reduce loads with devices that are as simple as possible, and do not require sensors nor actuators. The main features and critical issues of each concept are highlighted and illustrated with reference to a large conceptual 10 MW wind turbine

Survey of Period Variations of Superhumps in SU UMa-Type Dwarf Novae

We systematically surveyed period variations of superhumps in SU UMa-type dwarf novae based on newly obtained data and past publications. In many systems, the evolution of superhump period are found to be composed of three distinct stages: early evolutionary stage with a longer superhump period, middle stage with systematically varying periods, final stage with a shorter, stable superhump period. During the middle stage, many systems with superhump periods less than 0.08 d show positive period derivatives. Contrary to the earlier claim, we found no clear evidence for variation of period derivatives between superoutburst of the same object. We present an interpretation that the lengthening of the superhump period is a result of outward propagation of the eccentricity wave and is limited by the radius near the tidal truncation. We interpret that late stage superhumps are rejuvenized excitation of 3:1 resonance when the superhumps in the outer disk is effectively quenched. Many of WZ Sge-type dwarf novae showed long-enduring superhumps during the post-superoutburst stage having periods longer than those during the main superoutburst. The period derivatives in WZ Sge-type dwarf novae are found to be strongly correlated with the fractional superhump excess, or consequently, mass ratio. WZ Sge-type dwarf novae with a long-lasting rebrightening or with multiple rebrightenings tend to have smaller period derivatives and are excellent candidate for the systems around or after the period minimum of evolution of cataclysmic variables (abridged).Comment: 239 pages, 225 figures, PASJ accepte

An integrated approach to the preliminary weight sizing of small electric aircraft

Electric propulsion has received attention in aviation as witnessed by studies in hybrid designs and by the production of aircraft with support electric motors to be used in limited parts of the mission with ancillary roles. Until the recent past, the main limit to a wider adoption of electric propulsion, which besides having a lower environmental impact with respect to internal combustion engines (ICE) in terms of noise and emissions, can also improve reliability and on-board comfort, was the need for mass and volume-inefficient battery packs as devices for energy storage. However, thanks to the level of technology now reached by batteries, it is becoming possible to design and build electrically propelled aircraft at least in the category of light or general aviation. Due to the relative novelty of this technology, only few examples of similar aircraft exist today, mainly modifications of more traditional concepts, and thinking of a completely new electric aircraft is made difficult by the lack of a consolidated design framework, differently from the case of traditional ICE-powered models. This paper tries to cope with some basic aspects typical to electrically propelled aircraft, to the aim of setting up a stable and reliable preliminary sizing procedure allowing designers and aircraft companies to quickly size up and compare all-electric designs. To this aim, a statistical analysis of the basic characteristics of existing aircraft is presented first, showing a good correlation level between some of them. Next a method for the preliminary sizing of weights is shown, obtained starting from a more usual step-by-step procedure typically adopted for ICE-propelled aircraft. Due to the peculiar characteristics of electrically powered aircraft, the new procedure involves an integrated use of the case-specific mission profile and sizing matrix. The validity of the proposed procedure is testified by example analyses on two realistic designs of lightweight aircraft

Integrated aero-structural optimization of wind turbines

The present work describes methods for the integrated aero-structural optimization of wind turbines. The goal of the algorithms is to identify the structural and aerodynamic design characteristics that achieve the minimum cost of energy for a given wind turbine configuration. Given the strong couplings that exist between aerodynamic and structural design choices, the methods are formulated so as to address both problems simultaneously in an integrated manner, resulting in tools that may help avoid suboptimal solutions or lengthy design loops. All methods considered herein use the same high fidelity multibody aeroservoelastic simulation environment and operate the design according to standard certification guidelines. The methods, however, differ in the way the optimization is conducted, realizing different tradeoffs amongst computational efficiency, generality, level of automation and overall robustness. The proposed formulations are exercised on the design of a conceptual 10 MW horizontal axis wind turbine, illustrating the main characteristics of the various methods

Ultimate and fatigue load mitigation by an inertial-driven passive flap, using a geometrically exact multibody formulation

The paper characterizes the performance of a passive flap concept when applied to a modern very large conceptual wind turbine. The passive flap responds automatically to blade and/or tower vibrations, inducing a change of camber that opposes dynamic loads on the wind turbine. This is obtained in a purely passive manner, without the need for actuators or sensors. The present study is based on a detailed, geometrically exact multibody formulation of the device, which is able to capture all kinematic and structural dynamic effects of this inertia-driven device. The present modeling of the passive device improves on previous studies conducted with simplified models. Results show a significant ability in the reduction of both fatigue and ultimate loads, including the case of flap-specific fault scenarios. Solutions for limiting losses in energy yield caused by non-null average flap rotations in the partial load region are also investigated. The present analysis motivates further studies aimed at reaping the benefits of load alleviation enabled by the passive flap, for example by designing a new enlarged rotor at similar key loads on the rest of the machine

Aircraft with electric batteries, in particular a hybrid aircraft

The present invention relates to an aircraft (100) comprising: a fuselage (101) comprising a plurality of panels (105) adapted to define an aerodynamic shape for a cockpit or a cargo hold of the aircraft (100);at least one wing (103) structurally connected to the fuselage (101) and adapted to allow flying of said aircraft (100), the wing (103) comprising a plurality of wing surfaces and at least a frame configured to support the wing surfaces; a propulsion system for the aircraft (100), comprising at least one electric motor, and batteries adapted to store electrical energy to supply the electric motor. The batteries comprise first structural batteries which constitute at least one surface (104a, 104b) of the wing surfaces, and further second structural batteries which constitute at least one panel (105) of the panels of the fuselage