Antonio Dumas

A critical review of propulsion concepts for modern airships

After a few decades in which airships have been depromoted to the level of being only considered as a mere curiosity they seem now to reappear. The main reasons for this are related to the recent progress in technology of materials, aerodynamics, energy and propulsion. Airships are also presenting themselves as green friendly air vehicles, in particular if solar powered airships are considered. Their ability to remain aloft for long time periods have also expanded the range of mission profiles for which they are suited. Herein we have concentrated on a critical overview of propulsion mechanisms for airships. These include a detailed overview of past, present, and future enabling technologies for airship propulsion. Diverse concepts are revisited and the link between the airship geometry and flight mechanics is made for diverse propulsion system mechanisms.

Coanda Synthetic Jet Deflection Apparatus and Control

This paper presents the theoretic and numerical background of a recent patent about an innovative Coanda Effect application. This innovative jet is designed to enhance the controllability of the system and to encompass static deflection of the fluid jet but especially the dynamic variation of the Coanda deflection with a very low inertia. This innovative nozzle is formerly named H.O.M.E.R., acronym of “High-speed Orienting Momentum with Enhanced Reversibility”. H.O.M.E.R. constitutes an application based on a dual propeller system. It explains how a vector controllable flux can be produced, with the ability to change angular position dynamically as a function of momentum (or velocity) of the two primitive streams. CFD based simulation in a configuration is provided and main calculations are produced to define the control model. Nozzle design guidelines are provided. The proposed system can be used both for aeronautical naval propulsion and industrial applications. presented at Aerospace Technology Conference and Exposition, 18 ottobre 2011, Toulouse, France

A review of thrust-vectoring in support of a V/STOL non-moving mechanical propulsion system

The advantages associated to Vertical Short-Take-Off and Landing (V/STOL) have been demonstrated since the early days of aviation, with the initial technolology being based on airships and later on helicopters and planes. Its operational advantages are enormous, being it in the field of military, humanitarian and rescue operations, or even in general aviation. Helicopters have limits in their maximum horizontal speed and classic V/STOL airplanes have problems associated with their large weight, due to the implementation of moving elements, when based on tilting rotors or turbojet vector mechanical oriented nozzles. A new alternative is proposed within the European Union Project ACHEON (Aerial Coanda High Efficiency Orienting-jet Nozzle). The project introduces a novel scheme to orient the jet that is free of moving elements. This is based on a Coanda effect nozzle supported in two fluid streams, also incorporating boundary layer plasma actuators to achieve larger deflection angles. Herein we introduce a state-of-the-art review of the concepts that have been proposed in the framework of jet orienting propulsion systems. This review allows to demonstrate the advantages of the new concept in comparison to competing technologies in use at present day, or of competing technologies under development worldwide.

Photovoltaic stratospheric isle for conversion in hydrogen as energy vector

Abstract In a previous work it has been demonstrated that solar radiation intercepted by an unconventional airship is sufficient for all energetic needs for civil uses, namely broadcasting and telecommunications. This article analyses the energetic feasibility of an airship, named PSICHE (acronym for ‘photovoltaic stratospheric isle for conversion in hydrogen as energy vector’). It demonstrates the economic and industrial feasibility of high altitude production of electrolytic hydrogen fed by a photovoltaic plant. The most important aspects connected with high quote and hydrogen and oxygen production are discussed. The advantages of this kind of hydrogen production are presented together with the environmental benefits of the system.

Effects of Altitude on Photovoltaic Production of Hydrogen

This paper compares hydrogen production by photovoltaic powered electrolysis of water at sea level and at low stratospheric altitudes up to 21 km. All the hydrogen production process has been considered from catchable solar radiation to storage technologies. The evaluation has been performed for 1 m2 of flat horizontal plane. It has been considered the electric energy amount produced considering variations in equilibrium temperature and in solar. Hydrogen production through electrolysis has been evaluated too. Two different methods of hydrogen storage have been evaluated: high pressure compression up to 20 MPa and liquefaction process. The energetic cost of both production processes has been evaluated. The comparison is presented in terms of effective energy deliverable to final users considered in terms of HHV. This evaluation considers also, in the case of liquefaction process the energy which can be recovered by the rigasification process.Copyright

Acheon Project: A Novel Vectoring Jet Concept

This paper presents a general overview of the ACHEON Project (EU FP7 Level 0 - Transport including Aeronautic).This project presents a novel dynamically controllable Coanda jet using two fluid streams to produce the angular deflection of the jet as a function of their momentum. A control system with electrostatic plasma is used to produce an effective and more precise control of the system.This paper presents the general guidelines of the project which is going to start and presents expected results.Copyright

High Altitude Platforms for Telecommunications: Design Methodology

High Altitude Platforms (HAPs) represents an appealing solution to deliver low cost broadband access to telecommunication networks. However, this potential can be disclosed only if a proper technology is identified in the design of airships and aircrafts. This paper first presents the innovative services which can be provided by a fleet of HAPs in the field of information and communication technology (ICT), and then a novel approach to a modular the design of HAPs is presented. In particular, this study consists of a theoretical investigation and energetic design of an HAP derived from a new class of stratospheric airship for the production of energy at high quote. In practice the energy is harvested by photovoltaic panels and stored in hydrogen fuel cells. We denote this new technology with the acronym P.S.I.C.H.E. (Photovoltaic Space Island for Conversion of Hydrogen as Energy vector). In this paper authors consider the problems connected to the dimensional scalability of the system in order to verify the possibility of producing a reduced version of P.S.I.C.H.E. for telecommunication services only. This platform for telecommunication can operate over northern Italy (about 45° latitude north) at altitudes between 15-16 Km. Operative altitude and volume of lifting gas can vary as a function of winds in any other location all over the world. By these considerations authors are going to propose a novel iterative design methodology to dimension an airship characterized by a shape with a vertical rotation axis.

Design methods of Coanda effect nozzle with two streams

This paper continues recent research of the authors about the ACHEON Coanda effect two streams nozzle. This nozzle aims to produce an effective deflection of a propulsive jet with a correspondent deviation of the thrust vector in a 2D plane. On the basis of a previously published mathematical model, based on integral equations, it tries to produce an effective design guideline, which can be adopted for design activities of the nozzle for aeronautic propulsion. The presented model allows defining a governing method for this innovative two stream synthetic jet nozzle. The uncertainness level of the model are discussed and novel aircraft architectures based on it are presented. A CFD validation campaign is produced focusing on validating the model and the designs produced.

An Airship Design Methodology Based on Available Solar Energy in Low Stratosphere

The actual applicative research concerning airships and their use as HAP (High Altitude Platforms for telecommunications and military use) presents new applicative hypothesis of these systems, also concerning energetic high quote production. Authors present the energetic balance of a high quote photovoltaic platform with capability of static hovering realized by electric powered propellers. This is the first step trough the design of the P. S. I. C. H. E. (Photovoltaic Space Island for Conversion of Hydrogen as Energy vector) airship concept: a stratospheric airship which could be considered a platform for hydrogen and oxygen production by photovoltaic. It investigates the behaviour of a similar platform operating at altitudes between 10 and 20 km, positioned at 45° latitude north [1, 2]. This paper analyses the design process for a High Altitude Platform based on photovoltaic energy caption, but the process could be generalized in order to be applied to any airship project. It is considers airship shapes equipped with large PV array that covers energy request during the day. Surplus in power supplies electrolyser equipments for hydrogen and oxygen production from water, which could be captured by atmospheric humidity or brought by an auxiliary airship. Hydrogen and Oxygen are compressed and stored in gas cylinders. With insufficient solar irradiance, with severe wind conditions and during the night, a fuel cell system fed by hydrogen and oxygen tanks supplies power requirements. The Standard Atmosphere Model is used to evaluate PV performance at various operative altitudes. A propulsion system with electric motors grants airship manoeuvrability and hovering. Energy balance of PV-hydrogen energy supply system has been analyzed for three airship shapes with equal volume with concern of overabundant hydrogen and oxygen production. Total weight and payload are calculated in relation to altitude. Storage tanks dimensions and products ground transportation frequency has been estimated. Hydrogen annual production for PV square meter has been evaluated in relation to ground production at the same latitude.Copyright

Numerical modeling of coanda effect in a novel propulsive system

Coanda effect (adhesion of jet flow over curved surface) is fundamental characteristics of jet flow. In the present paper, we carried out numerical simulations to investigate Coanda flow over a curved surface and its application in a newly proposed Propulsive system “A.C.H.E.O.N” (Aerial Coanda High Efficiency Orienting jet Nozzle) which supports thrust vectoring. The ACHEON system is presently being proposed for propelling a new V/STOL airplane in European Union. This system is based on cumulative effects of three physical effects such as (1) High speed jet mixing speeds (2) Coanda effect control by electrostatic fields (3) Coanda effect adhesion of an high speed jet to a convex surface. The performance of this nozzle can be enhanced by increasing the jet deflection angle of synthetic jet over the Coanda surface. This newly proposed nozzle has wide range of applications. It can be used in industrial sector such as plasma spray gun and for direct injection in combustion chamber to enhance the efficiency of the combustion chamber. Also, we studied the effect of Dielectric barrier discharge (DBD) plasma actuators on A.C.H.E.O.N system. Dielectric barrier discharge (DBD) plasma actuators are active control devices for controlling boundary layer and to delay the flow separation over any convex surfaces. Computations were performed under subsonic condition. Two dimensional CFD calculations were carried out using Reynolds averaged Navier stokes equations (RANS). A numerical method based on finite volume formulation (FVM) was used. SST k-ω model was considered to model turbulent flow inside nozzle. DBD model was used to model the plasma. Moreover, a body force treatment was devised to model the effect of plasma and its coupling with the fluid. This preliminary result shows that, the presence of plasma near Coanda surface accelerates the flow and delays the separation and enhances the efficiency of the nozzle.