1,721,013 research outputs found
Genetic algorithms for the evaluation of the mistune effects on turbomachine bladed disks
No full textIn this paper a new approach to the mistune effects evaluation on turbomachine is presented that cannot be classified neither deterministic neither statistical: it is based on the employment of genetic algorithms. A genetic algorithm has been developed to find the structural mistuned configuration that leads to the maximum value of blade vibration amplitude for an assigned domain of variations. A test case has been fixed and subjected to an assigned forcing field: the target was to perform a smart search of the worst mistuned configuration. The test case was a twenty blades disc on which one thousand forced frequency response analyses have been performed. The investigation has demonstrated the applicability of the genetic algorithms to the study of structural behaviour of mistuned rotors
CAPECON (Civil UAV Applications & Economic Effectivity of Potential Configurations Solutions) finanziato dall'Unione Europea nell'ambito del 5° Programma Quadro. Inizio: 1° Maggio 2002; Fine: 30 Aprile 2005
No full textNell’ambito del Programma di Ricerca finanziato dall’Unione Europea e denominato CAPECON (Civil UAV Applications & Economic Effectivity of Potential Configurations Solutions) il Dott. Gennaro Scarselli, con la supervisione del Prof. Leonardo Lecce, ed in collaborazione con i Gruppi di Costruzioni Aeronautiche, guidato dal Prof. Accardo, e Meccanica del Volo, guidato dal Prof. Coiro, ha coordinato le attività tecniche finalizzate alla progettazione completa di un MALE (Medium Altitude Long Endurance) UAV e consistenti: nella preliminare progettazione aerodinamica del velivolo in accordo al profilo di missione specificato ed ai requisiti imposti; nella conseguente progettazione strutturale del velivolo; nell’analisi di Affidabilità e Sicurezza eseguita a partire dai dati tecnici riguardanti i singoli sottosistemi. In particolare il Dott. Gennaro Scarselli ha seguito la progettazione strutturale che è stata svolta con il seguente approccio: sono state individuate due possibili soluzioni, una in composito e l’altra in alluminio, che sono state calcolate agli elementi finiti in modo da garantire una fissata resistenza ai carichi esterni. Queste due soluzioni sono state confrontate al fine di individuare la migliore in termini di peso e, quindi, di prestazioni. Dal confronto è emersa una maggiore efficienza dell’impiego di materiali compositi dal punto di vista prestazionale. Nell’ambito dello stesso Programma di Ricerca, CAPECON, il DPA della "Federico II" di Napoli aveva il compito di analizzare dal punto di vista strutturale le prestazioni di un HALE (High Altitude Long Endurance) UAV, denominato OBW, il cui concetto è stato sviluppato dal Centro di Ricerca francese Onera: a tale scopo il Dott. Gennaro Scarselli, in collaborazione con il gruppo di Costruzioni Aeronautiche del Prof. Accardo, ha eseguito l’analisi statica e dinamica (analisi di modi propri e frequenze naturali) della semiala di un blended wing body, tipologia di velivolo consistente in unico corpo ala – fusoliera mosso da due Pratt&Whitney 535. Inoltre il DPA ha eseguito l’analisi di Affidabilità e Sicurezza valutando i parametri MTBCF (Mean Time Before Critical Failure), MTBL (Mean Time Before Loss), MTBUCL (Mean Time Before UnControlled Landing) relativi al velivolo OBW. L’analisi eseguita in base ai principi della Teoria dell’Affidabilità, utilizzando la schematizzazione del sistema velivolo come unione di sottosistemi (Airframe, Propulsore, Sistema di Produzione di Energia Elettrica, Sistema di Produzione di Energia Idraulica, Sistema Carrelli di Atterraggio, Sistema Controllo di Volo, Sistema per la Navigazione, Sistema di comunicazione e trasmissione dati), ha mostrato la piena compatibilità delle prestazioni del velivolo con i requisiti imposti
Preliminary Optimization of the Sonic Boom Properties for Civil Supersonic Aircraft
No full textIn this work a simple model has been used that relates sonic boom
effects to the main geometric and operative parameters of the civil
supersonic aircraft. In particular, a relation between the maximum
overpressure and the aircraft shape factor is employed to define an
optimal preliminary design point for the supersonic civil aircraft.
Carlson’s method has been widely adopted for preliminary numerical
investigations of sonic boom signatures associated with different
categories of supersonic aircrafts. Correlations of these numerical
predictions with flight-test data have shown a reasonable agreement
and confirmed the validity of the method in spite of its ease of use.
Modern supersonic aircrafts are conceived to have minimum effects
on people and structures through properly designed sonic boom
signatures (“sine wave”- like signature is one option) and adjusting their geometry through sophisticated Computational Fluid Dynamics
methods. The N-wave approach is based on simplified assumptions
that do not take into account the rise time, which is one of the major
factors influencing the human ear response to sonic boom and cannot
be used for estimating advanced sound metrics like the perceived
loudness decibel. Nevertheless, the N-wave model can be used in an
early stage of the design, because it generally provides conservative
estimations (upper limits) of the overpressures due to an assigned
supersonic aircraft geometry, giving a rough figure of its effect on the
community. Different geometries can be, therefore, easily optimized
through this approach to better fix starting points for minimizing the
effects of boom signatures, which are shaped subsequently through
higher-order methods
Employment of an acoustic camera for noise characterisation of a laboratory equipment
No full textExposure to noise constitutes a health risk. The present paper is related to activities performed to test emerging technologies aimed to characterise noise sources. In particular, acoustic acquisitions have been achieved on a complex laboratory equipment composed by different machines including a rotor serving as blower. Advanced noise measurement techniques based on acoustic
holography and beamforming have been employed to realise a deep characterisation of the noise sources. This analysis could fix, in effective way, the possible mitigation strategies and, if extended
to the other noise sources, a comprehensive management of the workplace noise exposure
Preliminary evaluation and optimization of civil aircraft sonic-boom properties through Carlson's method
Full text linkIn this paper a simple approach based on the Carlson's method will be presented to define a supersonic conguration optimized in terms of sonic boom properties. The Carlson's method provides a simplified procedure for the calculation of sonic boom characteristics for supersonic airplane congurations and spacecrafts. The information required for the signature predictions
are: aircraft shape factor KS, aircraft operating conditions and atmospheric data. Unfortunately, there is not an analytic expression of the shape factor. Nevertheless, a graphic representing the relationship between KS and parameters related to the aircraft geometry, can be used. In this paper KS have been approximated through a linear and a quadratic interpolation as a function of other parameters and its minimization problem has been formulated. Computational results show the optimal values to be assigned to the aircraft geometry parameters in order to obtain the minimal value of the shape factor and in consequence of the sonic boom overpressure
Sonic Boom Minimization Through a Simplified Approach for the Preliminary Design of Civil Supersonic Aircraft
No full textIn this paper a simple approach aimed to the definition of a supersonic configuration optimized in terms of sonic boom signature will be presented. This approach is based on the application of Carlson’s method that is a simplified method for the calculation of sonic-boom characteristics for a wide variety of supersonic airplane configurations and spacecraft. Sonic-boom overpressures and signature duration may be predicted for the entire affected ground area for vehicles in level flight or in moderate climbing or descending flight paths. This prediction technique is based on simplification of the purely theoretical methods, which are able to provide quite acceptable estimates of sonic-boom phenomena for a wide range of flight conditions for conventional airplane configurations. Experimental measurements have shown that this approach describes properly sonic-boom properties for extremely blunt bodies at high supersonic speeds, providing reliable numerical information at distances large relative to body dimensions. The effects of flight-path curvature and aircraft acceleration, however, are not considered, and the method is further restricted to a standard atmosphere without winds. Furthermore, it is assumed that the pressure signal generated by the aircraft is of the far-field type, the classical N-wave. The information required, for the calculations and the pressure-signature predictions provided by the simplified method, are: aircraft shape-factor; aircraft operating conditions; atmospheric data. The signature data provided by the method include: N-wave bow-shock overpressure; the signature duration; the location of the ground impact point relative to the aircraft position at the time the boom was generated. This approach has been adopted to evaluate the sonic boom properties of a supersonic reference configuration comparing the numerical results with a more refined CFD approach. Then an optimization procedure has been applied to minimize the maximum value of overpressure: the geometry of the reference configuration has been modified iteratively following the criteria suggested by the Carlson’s method and keeping in mind several operational constraints: this iterative method has permitted the definition, in a preliminary stage of design, of an optimized supersonic configuration
Co-curing bonding of carbon fibre/epoxy composite joints with excellent structure integrity using carbon fibre/PEEK tapes
No full textA novel co-curing process was proposed for the bonding of carbon fibre/epoxy composites by replacing traditional epoxy adhesives with carbon fibre/PEEK (CF/PEEK) tapes, with an attempt to improve the structure integrity. The lap-shear strengths, fatigue resistance and mode-I and mode-II fracture behaviour of the co-cured joints at 22 °C and 130 °C were investigated, and the failure mechanisms were also studied. The experimental results demonstrated that, by replacing an aerospace structural adhesive with surface-treated CF/PEEK tapes for the co-curing bonding of composite joints, the lap-shear strength of the joints had been increased by 47% and 68% at 22 °C and 130 °C, respectively; the fatigue life had been extended by 3.39 times; the mode-I fracture energy had been increased by 70% and 182% at 22 °C and 130 °C, respectively; and the mode-II fracture energy had been increased by 59% and 54% at 22 °C and 130 °C, respectively. An analysis on the failure surfaces of the tested specimens proved significant plastic deformation and breakage of the PEEK resin and extensive carbon fibre delamination being the main failure mechanisms of the CF/PEEK bonded joints. Overall, this study demonstrated a huge potential of replacing traditional film adhesives with CF/PEEK tapes for the co-curing bonding of aerospace composite joints with significantly enhanced structure integrity and thermal stability.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Structural Integrity & Composite
Mistuning effects evaluation on turbomachine dynamic behaviour using genetic algorithms
Full text linkThis paper presents a new approach to evaluating the mistuning effects on turbomachinery blades that is classified
as neither deterministic nor statistical — it is based on the employment of genetic algorithms. A genetic algorithm
has been exploited to find the structurally mistuned configuration that leads to the maximum value of blade
vibration amplitude for an assigned domain of variations. A test case has been fixed and subjected to an assigned
forcing field; the target of the test case was to perform a smart search of the worst mistuned configuration. The test
case was a twenty-blade disc on which one thousand forced frequency response analyses have been performed. A
comparison with the results, based on the Monte Carlo methods, proved the suitability and the relevance of the
proposed approach. The investigation has demonstrated the applicability of this new possible engineering approach
to the study of systems with uncertain properties
Impiego di algoritmi genetici per la valutazione degli effetti del mistuning sulla risposta dinamica di dischi palettati
No full textNella presente memoria viene presentato un nuovo approccio per la valutazione degli effetti del mistuning sul comportamento dinamico delle turbomacchine che non appartiene né alla categoria degli approcci deterministici né alla categoria degli approcci statistici: esso è basato sull’applicazione degli algoritmi genetici. Un algoritmo genetico è stato sviluppato in Matlab per individuare, in condizioni mistuned, la configurazione strutturale del disco oggetto della presente indagine caratterizzata dal valore massimo dell’ampiezza di vibrazione delle palette: a tale scopo, è stato individuato un test case significativo che è stato sottoposto ad un assegnato campo di forze. Il test case è rappresentato da un disco di venti palette sul quale sono state compiute mille analisi di risposta forzata in frequenza ciascuna delle quali corrispondente ad una perturbazione della simmetria ciclica della struttura. L’obiettivo della presente indagine era progettare l'Algoritmo Genetico, variando opportunamente i singoli parametri operativi. Il lavoro ha mostrato l’applicabilità di questo approccio allo studio degli effetti del mistuning sul comportamento strutturale dei rotori
Performance evaluation of a full composite Ultra-LightAircraft and guidelines for their improvement
Full text linkThe present job is focused on a full composite ultra-light aircraft, and has the main goal of evaluating the existing margins for the
improvement of the vehicle performance through a dedicated optimization of the aerodynamic and structural properties. For
what concerns the aerodynamic properties of the entire aircraft, at first the attention has been focused on the airfoil chosen for the wings. Then the analysis of the complete wing and aircraft has been carried out. The preliminary investigation on the structural properties of the aircraft has been concerning an accurate
evaluation of the operational external loads in order to obtain a confident estimation of the structural solicitation parameters and the identification of the most stressed aircraft structural parts
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