Advanced Waste-To-Energy Cycles

The increase in environmental and healthy concerns, combined with the possibility to exploit waste as a valuable energy resource, has led to explore alternative methods for waste final disposal. In this context, the energy conversion of Municipal Solid Waste (MSW) in Waste-To-Energy (WTE) power plant is increasing throughout Europe, both in terms of plants number and capacity, furthered by legislative directives. Due to the heterogeneous nature of waste, some differences with respect to a conventional fossil fuel power plant have to be considered in the energy conversion process. In fact, as a consequence of the well-known corrosion problems, the thermodynamic efficiency of WTE power plants typically ranging in the interval 25% ÷ 30%. The new Waste Framework Directive 2008/98/EC promotes production of energy from waste introducing an energy efficiency criteria (the so-called “R1 formula”) to evaluate plant recovery status. The aim of the Directive is to drive WTE facilities to maximize energy recovery and utilization of waste heat, in order to substitute energy produced with conventional fossil fuels fired power plants. This calls for novel approaches and possibilities to maximize the conversion of MSW into energy. In particular, the idea of an integrated configuration made up of a WTE and a Gas Turbine (GT) originates, driven by the desire to eliminate or, at least, mitigate limitations affecting the WTE conversion process bounding the thermodynamic efficiency of the cycle. The aim of this Ph.D thesis is to investigate, from a thermodynamic point of view, the integrated WTE-GT system sharing the steam cycle, sharing the flue gas paths or combining both ways. The carried out analysis investigates and defines the logic governing plants match in terms of steam production and steam turbine power output as function of the thermal powers introduced.

New mechanisms for modelling the motion of the human ankle complex

The relevance of human joint models was shown in the literature. In particular, the great importance of models for the joint passive motion simulation (i.e. motion under virtually unloaded conditions) was outlined. They clarify the role played by the principal anatomical structures of the articulation, enhancing the comprehension of surgical treatments, and in particular the design of total ankle replacement and ligament reconstruction. Equivalent rigid link mechanisms proved to be an efficient tool for an accurate simulation of the joint passive motion. This thesis focuses on the ankle complex (i.e. the anatomical structure composed of the tibiotalar and the subtalar joints), which has a considerable role in human locomotion. The lack of interpreting models of this articulation and the poor results of total ankle replacement arthroplasty have strongly suggested devising new mathematical models capable of reproducing the restraining function of each structure of the joint and of replicating the relative motion of the bones which constitute the joint itself. In this contest, novel equivalent mechanisms are proposed for modelling the ankle passive motion. Their geometry is based on the joint’s anatomical structures. In particular, the role of the main ligaments of the articulation is investigated under passive conditions by means of nine 5-5 fully parallel mechanisms. Based on this investigation, a one-DOF spatial mechanism is developed for modelling the passive motion of the lower leg. The model considers many passive structures constituting the articulation, overcoming the limitations of previous models which took into account few anatomical elements of the ankle complex. All the models have been identified from experimental data by means of optimization procedure. Then, the simulated motions have been compared to the experimental one, in order to show the efficiency of the approach and thus to deduce the role of each anatomical structure in the ankle kinematic behavior.

Studio del comportamento flesso-torsionale di un telaio in materiale composito per vettura sportiva

Lo studio svolto in merito alle tecniche di produzione di componenti strutturali in materiale composito ha permesso il raggiungimento di una precisa consapevolezza dello stato dell’arte del settore, in particolare in riferimento ai processi attualmente utilizzati per l’industrializzazione in media-grande serie. Con l’obiettivo di sintetizzare i principali vantaggi delle tecnologie suddette e permettere la realizzazione di forme più complesse, si è proceduto all’analisi di fattibilità, attraverso uno studio funzionale e una prima progettazione di una tecnologia di produzione per nastratura automatizzata di componenti strutturali in materiale composito. Si è voluto quindi dimostrare la flessibilità e la consistenza del processo disegnando un telaio nastrato in carbonio, intercambiabile al telaio FSAE 2009 in tubolare d’acciaio (stessi punti di attacco motore, punti di attacco telaietto posteriore, attacchi sospensioni anteriori) e che garantisca un sostanziale vantaggio in termini di peso, a pari rigidezza torsionale. La caratterizzazione di tale telaio è stata eseguita mediante l'utilizzo del calcolo strutturale, validato da prove sperimentali.

Produzione automatizzata per nastratura di componenti strutturali in materiale composito

Questa dissertazione tratterà l’argomento dello studio di metodi di progettazione e processi tecnologici innovativi per l’industrializzazione in medio-grande serie di componenti strutturali in materiale composito. L’interesse della ricerca verso questo ambito è suscitato dai notevoli vantaggi che l’utilizzo di materiali dall’alto rapporto prestazioni meccaniche/peso danno nella ricerca di elevate prestazioni in applicazioni sportive e diminuzione dei consumi ed emissioni inquinanti in mezzi di trasporto di grande serie. Lo studio di componenti in materiale composito è caratterizzato dalla peculiarità di non poter disgiungere la progettazione della geometria della parte da quella del materiale e del processo, ed in questo senso nella figura del progettista si vanno a riassumere sinergicamente competenze riguardanti i tre ambiti. Lo scopo di questo lavoro è la proposizione di una metodologia di progettazione e produzione di componenti strutturali che permetta l’utilizzazione ottimale della natura fibrosa del materiale composito sia dal punto di vista del trasferimento dei carichi tra diversi componenti, sia dal punto di vista del processo di laminazione che avviene per nastratura automatizzata. Lo studio è volto a mostrare in quali termini tale tecnologia sia potenzialmente in grado di superare i vincoli di forma ed i limiti di efficienza meccanica delle giunzioni tra le parti e di garantire maggiore produttività e costi inferiori rispetti ai diversi metodi di produzione che rappresentano oggi lo stato dell’arte dell’industrializzazione in medio-grande serie. Particolare attenzione verrà posta sull’utilizzo della tecnologia oggetto di studio per la produzione di telai automobilistici.

A Design Method for Flexure-Based Compliant Mechanisms on the Basis of Stiffness and Stress Characteristics

Geometric nonlinearities of flexure hinges introduced by large deflections often complicate the analysis of compliant mechanisms containing such members, and therefore, Pseudo-Rigid-Body Models (PRBMs) have been well proposed and developed by Howell [1994] to analyze the characteristics of slender beams under large deflection. These models, however, fail to approximate the characteristics for the deep beams (short beams) or the other flexure hinges. Lobontiu's work [2001] contributed to the diverse flexure hinge analysis building on the assumptions of small deflection, which also limits the application range of these flexure hinges and cannot analyze the stiffness and stress characteristics of these flexure hinges for large deflection. Therefore, the objective of this thesis is to analyze flexure hinges considering both the effects of large-deflection and shear force, which guides the design of flexure-based compliant mechanisms. The main work conducted in the thesis is outlined as follows. 1. Three popular types of flexure hinges: (circular flexure hinges, elliptical flexure hinges and corner-filleted flexure hinges) are chosen for analysis at first. 2. Commercial software (Comsol) based Finite Element Analysis (FEA) method is then used for correcting the errors produced by the equations proposed by Lobontiu when the chosen flexure hinges suffer from large deformation. 3. Three sets of generic design equations for the three types of flexure hinges are further proposed on the basis of stiffness and stress characteristics from the FEA results. 4. A flexure-based four-bar compliant mechanism is finally studied and modeled using the proposed generic design equations. The load-displacement relationships are verified by a numerical example. The results show that a maximum error about the relationship between moment and rotation deformation is less than 3.4% for a flexure hinge, and it is lower than 5% for the four-bar compliant mechanism compared with the FEA results.

Sviluppo di metodologie per la Stima in Tempo Reale delle Grandezze Indicate in Motori a Combustione Interna

Modern Internal Combustion Engines are becoming increasingly complex in terms of their control systems and strategies. The growth of the algorithms’ complexity results in a rise of the number of on-board quantities for control purposes. In order to improve combustion efficiency and, simultaneously, limit the amount of pollutant emissions, the on-board evaluation of two quantities in particular has become essential; namely indicated torque produced by the engine and the angular position where 50% of fuel mass injected over an engine cycle is burned (MFB50). The above mentioned quantities can be evaluated through the measurement of in-cylinder pressure. Nonetheless, at the time being, the installation of in-cylinder pressure sensors on vehicles is extremely uncommon mainly because of measurement reliability and costs. This work illustrates a methodological approach for the estimation of indicated torque and MFB50 that is based on the engine speed fluctuation measurement. This methodology is compatible with the typical on-board application restraints. Moreover, it requires no additional costs since speed can be measured using the system already mounted on the vehicle, which is made of a magnetic pick-up faced to a toothed wheel. The estimation algorithm consists of two main parts: first, the evaluation of indicated torque fluctuation based on speed measurement and secondly, the evaluation of the mean value of the indicated torque (over an engine cycle) and MFB50 by using the relationship with the indicated torque harmonic and other engine quantities. The procedure has been successfully applied to an L4 turbocharged Diesel engine mounted on-board a vehicle.

Studio e sperimentazione di leghe ad elevata deformazione per applicazioni nel settore della prima lavorazione di materiali lapidei

Studio del componente di supporto del cavo utensile per taglio di materiali lapidei. Analisi delle applicazioni di leghe superelastiche e delle modalità di realizzazione del cavo utensile complessivo in relazione a specifiche esigenze poste a livello industriale.

Integration of cognitive and affective processes in perception and decision-making

The relationship between emotion and cognition is a topic that raises great interest in research. Recently, a view of these two processes as interactive and mutually influencing each other has become predominant. This dissertation investigates the reciprocal influences of emotion and cognition, both at behavioral and neural level, in two specific fields, such as attention and decision-making. Experimental evidence on how emotional responses may affect perceptual and attentional processes has been reported. In addition, the impact of three factors, such as personality traits, motivational needs and social context, in modulating the influence that emotion exerts on perception and attention has been investigated. Moreover, the influence of cognition on emotional responses in decision-making has been demonstrated. The current experimental evidence showed that cognitive brain regions such as the dorsolateral prefrontal cortex are causally implicated in regulation of emotional responses and that this has an effect at both pre and post decisional stages. There are two main conclusions of this dissertation: firstly, emotion exerts a strong influence on perceptual and attentional processes but, at the same time, this influence may also be modulated by other factors internal and external to the individuals. Secondly, cognitive processes may modulate emotional prepotent responses, by serving a regulative function critical to driving and shaping human behavior in line with current goals.

Methods for Clearance Influence Analysis in Planar and Spatial Mechanisms

This doctoral dissertation presents a new method to asses the influence of clearancein the kinematic pairs on the configuration of planar and spatial mechanisms. The subject has been widely investigated in both past and present scientific literature, and is approached in different ways: a static/kinetostatic way, which looks for the clearance take-up due to the external loads on the mechanism; a probabilistic way, which expresses clearance-due displacements using probability density functions; a dynamic way, which evaluates dynamic effects like the actual forces in the pairs caused by impacts, or the consequent vibrations. This dissertation presents a new method to approach the problem of clearance. The problem is studied from a purely kinematic perspective. With reference to a given mechanism configuration, the pose (position and orientation) error of the mechanism link of interest is expressed as a vector function of the degrees of freedom introduced in each pair by clearance: the presence of clearance in a kinematic pair, in facts, causes the actual pair to have more degrees of freedom than the theoretical clearance-free one. The clearance-due degrees of freedom are bounded by the pair geometry. A proper modelling of clearance-affected pairs allows expressing such bounding through analytical functions. It is then possible to study the problem as a maximization problem, where a continuous function (the pose error of the link of interest) subject to some constraints (the analytical functions bounding clearance- due degrees of freedom) has to be maximize. Revolute, prismatic, cylindrical, and spherical clearance-affected pairs have been analytically modelled; with reference to mechanisms involving such pairs, the solution to the maximization problem has been obtained in a closed form.

Electrospun nanofibrous interleaves in composite laminate materials

The present work aims for investigate the influence of electrospun Nylon 6,6 nanofibrous mat on the behavior of composite laminates. The main idea is that nanofibrous interleaved into particular ply-to-ply interfaces of a laminate can lead to significant improvements of mechanical properties and delamination/damage resistance. Experimental campaigns were performed to investigate how nanofibers affect both the static and dynamic behavior of the laminate in which they are interleaved. Fracture mechanics tests were initially performed on virgin and 8 different configuration of nanomodified specimens. The purposes of this first step of the work are to understand which geometrical parameters of the nanointerleave influence the behavior of the laminate and, to find the optimal architecture of the nanofibrous mat in order to obtain the best reinforcement. In particular, 3 morphological parameters are investigated: nanofibers diameter, nanofibers orientation and thickness of the reinforce. Two different values for each parameter have been used, and it leads to 8 different configurations of nanoreinforce. Acoustic Emission technique is also used to monitor the tests. Once the optimum configuration has been found, attention is focused on the mechanism of reinforce played by the nanofibers during static and dynamic tests. Low velocity impacts and free decay tests are performed to attest the effect of nanointerlayers and the reinforce mechanism during the dynamic loads. Bump tests are performed before and after the impact on virgin and two different nanomodified laminates configurations. The authors focused their attention on: vibrational behavior, low velocity impact response and post-impact vibration behavior of the nano-interleaved laminates with respect to the response of non-nanomodified ones. Experiments attest that nanofibers significantly strength the delamination resistance of the laminates and increase some mechanical properties. It is demonstrated that the nanofibers are capable to continue to carry on the loads even when the matrix around them is broken.

Composite materials design, manufacture and evaluation

Fibre-Reinforced-Plastics are composite materials composed by thin fibres with high mechanical properties, made to work together with a cohesive plastic matrix. The huge advantages of fibre reinforced plastics over traditional materials are their high specific mechanical properties i.e. high stiffness and strength to weight ratios. This kind of composite materials is the most disruptive innovation in the structural materials field seen in recent years and the areas of potential application are still many. However, there are few aspects which limit their growth: on the one hand the information available about their properties and long term behaviour is still scarce, especially if compared with traditional materials for which there has been developed an extended database through years of use and research. On the other hand, the technologies of production are still not as developed as the ones available to form plastics, metals and other traditional materials. A third aspect is that the new properties presented by these materials e.g. their anisotropy, difficult the design of components. This thesis will provide several case-studies with advancements regarding the three limitations mentioned. In particular, the long term mechanical properties have been studied through an experimental analysis of the impact of seawater on GFRP. Regarding production methods, the pre-impregnated cured in autoclave process was considered: a rapid tooling method to produce moulds will be presented, and a study about the production of thick components. Also, two liquid composite moulding methods will be presented, with a case-study regarding a large component with sandwich structure that was produced with the Vacuum-Assisted-Resin-Infusion method, and a case-study regarding a thick con-rod beam that was produced with the Resin-Transfer-Moulding process. The final case-study will analyse the loads acting during the use of a particular sportive component, made with FRP layers and a sandwich structure, practical design rules will be provided.

Qualifica a Vibrazioni di Componenti Meccanici: Studio e Verifica di una Procedura di Test Tailoring.

I test di qualifica a vibrazioni vengono usati in fase di progettazione di un componente per verificarne la resistenza meccanica alle sollecitazioni dinamiche (di natura vibratoria) applicate durante la sua vita utile. La durata delle vibrazioni applicate al componente durante la sua vita utile (migliaia di ore) deve essere ridotta al fine di realizzare test fattibili in laboratorio, condotti in genere utilizzando uno shaker elettrodinamico. L’idea è quella di aumentare l’intensità delle vibrazioni riducendone la durata. Esistono diverse procedure di Test Tailoring che tramite un metodo di sintesi definiscono un profilo vibratorio da applicare in laboratorio a partire dalle reali vibrazioni applicate al componente: una delle metodologie più comuni si basa sull’equivalenza del danno a fatica prodotto dalle reali vibrazioni e dalle vibrazioni sintetizzate. Questo approccio è piuttosto diffuso tuttavia all’autore non risulta presente nessun riferimento in letteratura che ne certifichi la validità tramite evidenza sperimentalmente. L’obiettivo dell’attività di ricerca è stato di verificare la validità del metodo tramite una campagna sperimentale condotta su opportuni provini. Il metodo viene inizialmente usato per sintetizzare un profilo vibratorio (random stazionario) avente la stessa durata di un profilo vibratorio non stazionario acquisito in condizioni reali. Il danno a fatica prodotto dalla vibrazione sintetizzata è stato confrontato con quello della vibrazione reale in termini di tempo di rottura dei provini. I risultati mostrano che il danno prodotto dalla vibrazione sintetizzata è sovrastimato, quindi l’equivalenza non è rispettata. Sono stati individuati alcuni punti critici e sono state proposte alcune modifiche al metodo per rendere la teoria più robusta. Il metodo è stato verificato con altri test e i risultati confermano la validità del metodo a condizione che i punti critici individuati siano correttamente analizzati.

Analisi dell’influenza dei moti rigidi di una trattrice agricola sulle vibrazioni a corpo intero trasmesse all’operatore

L’esposizione degli operatori in campo agricolo alle vibrazioni trasmesse al corpo intero, produce effetti dannosi alla salute nel breve e nel lungo termine. Le vibrazioni che si generano sulle trattrici agricole hanno una elevata intensità e una bassa frequenza. Le componenti orizzontali, amplificate dalla posizione elevata della postazione di guida dall’asse di rollio, presentano maggiori criticità per quanto riguarda i sistemi di smorzamento rispetto alle componenti verticali. Queste caratteristiche rendono difficoltosa la progettazione dei sistemi dedicati alla riduzione del livello vibrazionale per questa categoria di macchine agricole. Nonostante l’installazione di diversi sistemi di smorzamento, il livello di vibrazioni a cui è sottoposto l’operatore può superare, in diverse condizioni di impiego, i livelli massimi imposti dalla legge per la salvaguardia della salute. L’obiettivo di questo lavoro è quello di valutare l’influenza dei moti rigidi di una trattrice (beccheggio, rollio e saltellamento) dotata di sospensione assale anteriore, sospensione cabina e sospensione sedile, sul livello vibrazionale trasmesso all’operatore.E’ stata pertanto strumenta una trattrice con accelerometri e inclinometri installati su telaio, cabina e sedile e utilizzata in diverse condizioni di lavoro in campo e di trasporto su strada. Dall’analisi delle prove effettuate emerge che durante il trasporto su strada è predominante l’accelerazione longitudinale, a causa dell’elevata influenza del beccheggio. La sospensione riduce notevolmente il moto rigido di beccheggio mentre l’effetto della sospensione della cabina è quello di incrementare, in ogni condizione di lavoro, il livello di accelerazione trasmesso dal telaio della macchina.

Development of control-oriented models of Dual Clutch Transmission systems

A control-oriented model of a Dual Clutch Transmission was developed for real-time Hardware In the Loop (HIL) applications, to support model-based development of the DCT controller. The model is an innovative attempt to reproduce the fast dynamics of the actuation system while maintaining a step size large enough for real-time applications. The model comprehends a detailed physical description of hydraulic circuit, clutches, synchronizers and gears, and simplified vehicle and internal combustion engine sub-models. As the oil circulating in the system has a large bulk modulus, the pressure dynamics are very fast, possibly causing instability in a real-time simulation; the same challenge involves the servo valves dynamics, due to the very small masses of the moving elements. Therefore, the hydraulic circuit model has been modified and simplified without losing physical validity, in order to adapt it to the real-time simulation requirements. The results of offline simulations have been compared to on-board measurements to verify the validity of the developed model, that was then implemented in a HIL system and connected to the TCU (Transmission Control Unit). Several tests have been performed: electrical failure tests on sensors and actuators, hydraulic and mechanical failure tests on hydraulic valves, clutches and synchronizers, and application tests comprehending all the main features of the control performed by the TCU. Being based on physical laws, in every condition the model simulates a plausible reaction of the system. The first intensive use of the HIL application led to the validation of the new safety strategies implemented inside the TCU software. A test automation procedure has been developed to permit the execution of a pattern of tests without the interaction of the user; fully repeatable tests can be performed for non-regression verification, allowing the testing of new software releases in fully automatic mode.

A numerical methodology for the multi-objective optimization of the DI Diesel engine combustion

DI Diesel engine are widely used both for industrial and automotive applications due to their durability and fuel economy. Nonetheless, increasing environmental concerns force that type of engine to comply with increasingly demanding emission limits, so that, it has become mandatory to develop a robust design methodology of the DI Diesel combustion system focused on reduction of soot and NOx simultaneously while maintaining a reasonable fuel economy. In recent years, genetic algorithms and CFD three-dimensional combustion simulations have been successfully applied to that kind of problem. However, combining GAs optimization with actual CFD three-dimensional combustion simulations can be too onerous since a large number of calculations is usually needed for the genetic algorithm to converge, resulting in a high computational cost and, thus, limiting the suitability of this method for industrial processes. In order to make the optimization process less time-consuming, CFD simulations can be more conveniently used to generate a training set for the learning process of an artificial neural network which, once correctly trained, can be used to forecast the engine outputs as a function of the design parameters during a GA optimization performing a so-called virtual optimization. In the current work, a numerical methodology for the multi-objective virtual optimization of the combustion of an automotive DI Diesel engine, which relies on artificial neural networks and genetic algorithms, was developed.