1,721,156 research outputs found
PALLADIUM-BASED CATALYSTS AND RELATED MATERIALS FOR ENVIRONMENTALLY SUSTAINABLE APPLICATIONS
Full text linkThe PhD project has concerned the study and the applications of Pd-based catalysts in the fields of energy production and fine chemicals synthesis in eco-compatible conditionsIl lavoro svolto nel periodo di dottorato ha riguardato lo studio e le applicazioni di catalizzatori a base di Pd nel campo della produzione di energia e della sintesi di prodotti di chimica fine in condizioni eco-compatibil
FEM/BEM Numerical Modeling of Diesel Engine Acoustic Emission
No full textThe present work deals with the numerical prediction of the combustion noise of a newly
developing aeronautical diesel engine. The study has been performed on a three dimensional
basis by the integration of FEM and BEM codes integration, in order to correlate the radiated
noise with the combustion pressure distribution inside the cylinders. The last purpose of such a
procedure is the characterization of the engine in terms of acoustic power to be determine
according to normative ISO 3746.
The set of actions that have been performed may be summarized as follows:
1. Starting from the CAD model, a 3-D finite element model of the engine has been
realized;
2. The model has been characterized in terms of eigen-frequencies and modes
3. The surface vibration velocity has been measured under the in-cylinder combustion
pressure load (at the investigated engine speeds);
4. Direct BEM approach has been than that used to evaluate the radiated noise field in
terms of sound pressure at 1 meter of distance and in terms of sound power according
to the ISO 3746.
These results have been used as driving parameters for successive engine structural design
and will be later on experimentally verifie
On functional successive minima
Full text linkIn the classical Geometry of Numbers, the calculation of successive minima may be quite difficult, even in
using the norm coming from a distance function associated to a set. In the literature, there seem to be hardly any analogues when
is replaced by the algebraic closure of a function field in one variable and one uses a norm arising from the absolute height. Here, we calculate a one-parameter family of examples that naturally arose in our recent paper on bounded heights. We also comment on whether the minima are attained
Effectiveness of Wing Twist Morphing in Roll Control
No full textThis paper is focused on numerical investigations that analyze the advantages obtained from high-aspect-ratio wings with unconventional roll control strategies based on wing twist morphing. A sailplane, the G103-B, produced by the GROB Werke company, was chosen as the reference aircraft for the analyses. For confidentiality reasons, the data disclosed by the builder covered only general properties such as the main dimensions, the lifting surface airfoils and attitudes, the characteristic speeds and a rough mass budget. As a consequence of this, “reverse-engineering” was considered necessary to define a reasonable wing structural layout that enabled the analysis of the elastic-aircraft roll dynamics. A preliminary sizing of the wing structure was addressed using CS-22 airworthiness requirements and by adopting fast, elementary approaches that are well known in the literature. The estimated structural arrangement, which was verified using a finite element analysis, was then used to generate the aircraft dynamic model. The elastic-aircraft roll dynamics were first investigated with regard to conventional aileron-based control. Extra modes simulating controlled twist distributions along the wing span were added into the aircraft modal base and their effects on the aircraft roll dynamics were analyzed. The conventional (aileron-based) and the unconventional (wing twist morphing) roll control strategies were compared from the aerodynamic and the aeroelastic standpoints, and the benefits achieved with the unconventional strategy are summarized
A novel multi-body architecture for wing flap camber morphing
No full textThe increase of lift force required by an aircraft during take-off and landing phases is conventionally obtained through wing flap deflection. Such devices are usually driven by control systems made of robust actuators and control lines that significantly contribute to the weight of the whole wing structure and, whereas proper external fairings are needed, also to wing friction drag and aerodynamic noise. Moreover, the shape change locally induced by flaps to wing airfoils is clearly limited to the allowable flaps excursion; it follows that, in operative conditions, only a discrete set of few airfoil shapes can be achieved, each shape being related to a precise flap deflection angle within the allowable range. The naturally foreseen advantages of an adaptive high lift device able to smoothly change its shape according to flight conditions as well as the intent of reducing friction drag and emitted aerodynamic noise in take-off and landing, all represented valid motivations for the assessment of a novel flap technology. In the framework of the Low Noise Configuration domain of the Clean Sky – GRA ITD, the authors proved the feasibility of a morphing architecture enabling the controlled camber variation of a flap segment in compliance with top-level requirements pertinent to the next generation Green Regional Aircraft. The architecture is characterized by an Al-alloy multi-body morphing structure based on articulated ribs driven by electro-mechanical actuators. By referring to specific aerodynamic requirements in terms of target shapes and external loads expected in service, the structural layout of the device was preliminarily defined. Advanced FE analyses were then carried out in order to properly size the load-carrying components of the structure and the actuation system. Design performances were finally validated by experimental tests carried out on a true-scale prototype. The experimental campaign covered functionality, static and dynamic tests; obtained results showed high correlation levels with respect to numerical expectations thus proving the compliance of the device with design requirements as well as the goodness of modelling approaches implemented during the design phase
Aeroelastic analysis of an adaptive trailing edge with a smart elastic skin
No full textNowadays, the design choices of the new generation aircraft are moving towards the research and development of innovative technologies, aimed at improving performance as well as to minimize the environmental impact. In the current “greening” context, the morphing structures represent a very attractive answer to such requirements: both aerodynamic and structural advantages are ensured in several flight conditions, safeguarding the fuel consumption at the same time. An aeronautical intelligent system is therefore the outcome of combining complex smart materials and structures, assuring the best functionality level in the flight envelope. The Adaptive Trailing Edge Device (ATED) is a sub-project inside SARISTU (Smart Intelligent Aircraft Structures), an L2 level project of the 7th EU Framework programme coordinated by Airbus, aimed at developing technologies for realizing a morphing wing extremity addressed to improve the general aircraft performance and to reduce the fuel burning up to 5%. This specific study, divided into design, manufacturing and testing phases, involved universities, research centers and leading industries of the European consortium. The paper deals with the aeroelastic impact assessment of a full-scale morphing wing trailing edge on a Large Aeroplanes category aircraft. The FE (Finite Element) model of the technology demonstrator, located in the aileron region and manufactured within the project, was referenced to for the extrapolation of the structural properties of the whole adaptive trailing edge device placed in its actual location in the outer wing. The input FE models were processed within MSC-Nastran® environment to estimate stiffness and inertial distributions suitable to construct the aeroelastic stick-beam mock-up of the reference structure. Afterwards, a flutter analysis in simulated operative condition, have been carried out by means of Sandy®, an in-house code, according to meet the safety requirements imposed by the applicable aviation regulations (paragraph 25.629, parts (a) and (b)-(1))
A Long term monitoring system for vibration control of civil structures
No full textThe paper deals with the design and implementation of an innovative system for
long term monitoring of civil structures. With reference to a multi point test site, with long term
monitoring requests, two different systems have been developed and tested. The first one, based
upon the use of analog sensors and a wired analog net, used a standard processing environment
that was specifically programmed and configured for the items of the study. The system, as developed,
gives the opportunity to monitor the different parameters of the phenomena, but presents
some drawbacks, as those typical of these configuration. The second system has been designed
on a “pure” digital basis. A specific sensor has been designed around an integrated triaxial
microchip accelerometers, with different capabilities in terms of local processing, data
storage and data transfer. In particular the actual version uses a can bus for data exchange between
the sensor’s net and the acquisition unit. Wireless connection is anyway implemented and
available under requests. The central unit, built around an ARM 7 μcontroller, govern the data
interchange, the relative storage and communication with the collecting data center. During the
first part of the work, a PC was used as a large mass storage unit, but remote control and storage
has been implemented and tested, to be used during the second part of the work. Inside the paper,
the description of the systems and the most interesting results will be presented and discusse
An original device for train bogie energy harvesting: a real application scenario
No full textToday, as railways increase their capacity and speeds, it is more important than ever to be completely aware of the state of vehicles fleet's condition to ensure the highest quality and safety standards, as well as being able to maintain the costs as low as possible. Operation of a modern, dynamic and efficient railway demands a real time, accurate and reliable evaluation of the infrastructure assets, including signal networks and diagnostic systems able to acquire functional parameters. In the conventional system, measurement data are reliably collected using coaxial wires for communication between sensors and the repository. As sensors grow in size, the cost of the monitoring system can grow. Recently, auto-powered wireless sensor has been considered as an alternative tool for economical and accurate realization of structural health monitoring system, being provided by the following essential features: on-board micro-processor, sensing capability, wireless communication, auto-powered battery, and low cost. In this work, an original harvester device is designed to supply wireless sensor system battery using train bogie energy. Piezoelectric materials have in here considered due to their established ability to directly convert applied strain energy into usable electric energy and their relatively simple modelling into an integrated system. The mechanical and electrical properties of the system are studied according to the project specifications. The numerical formulation is implemented with in-house code using commercial software tool and then experimentally validated through a proof of concept setup using an excitation signal by a real application scenario
Multi-parametric flutter analysis of a morphing wing trailing edge
No full textThe development of adaptive morphing wings has been individuated as one of the crucial topics in the greening of the next generation air transport. Researches programs are currently running worldwide to exploit the potentiality of morphing concepts in the optimization of aircraft efficiency and in the consequent reduction of fuel burn. Among these, SARISTU represents the largest European funded research project which ambitiously addresses the challenges posed by the physical integration of smart concepts in real aircraft structures; for the first time ever, SARISTU will experimentally demonstrate the structural feasibility of individual morphing concepts concerning the leading edge, the trailing edge and the winglet on a full-size outer wing belonging to a CS-25 category aircraft. In such framework, the authors intensively worked on the definition of aeroelastically stable configurations for a morphing wing trailing edge driven by conventional electromechanical actuators. Trade off aeroelastic analyses were performed in compliance with CS-25 airworthiness requirements in order to define safety ranges for trailing edge inertial and stiffness distributions as well as for its control harmonics. Rational approaches were implemented in order to simulate the effects induced by variations of trailing edge actuators’ stiffness on the aeroelastic behaviour of the wing also in correspondence of different dynamic properties of the trailing edge component. Reliable aeroelastic models and advanced computational strategies were properly implemented to enable fast flutter analyses covering several configuration cases in terms of structural system parameters. Obtained results were finally arranged in stability carpet plots efficiently conceived to provide guidelines for the preliminary design of the morphing trailing edge structure and therein embedded actuators
Experimental validation of novel friction damper for anti-seismic control of civil structures
No full textThis work presents a new semi-active friction damper device, based on piezoelectric technology, for the anti-seismic
control of civil structures. A civil structure, representative of a two storey steel framed building, and a reference
seismic excitation signal were used to size the semi-active friction damper. Matlab-Simulink based software (EarthSim) was
implemented to simulate the response of the steel frame to the seismic excitation, applied at the base of the structure. The dynamic response was evaluated both in the case of the active device (controlled response) as well as the non-active device. Different configurations (in terms of the device’s overall performance and control algorithm parameters) were simulated for the active control system. In so doing, a reference configuration for the structural control system was determined by identifying optimal values for control logic parameters, as well as for the dampers preload and maximum force.
Focus then turned to the structural design phase. 3D CAD was used to generate a digital mock-up of the device and structural
analyses were conducted using the finite element method.
The proposed device presents an original conceptual layout, characterised by a compact and easy allocation of the piezo-actuator which is installed inside the piston of the damper. A highly efficient transmission chain allows for the transfer of the compression force generated by the piezo-actuator, to four pads of friction material,preventing the motion of the piston along its chamber. Theoretical performances were validated by means of experimental tests carried out on a physical prototype, loaded through a hydraulic test machine
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