It is often necessary to operate a number of radio communication channels from a single control room without time-sharing between the various channels. Here it is necessary to operate a number of transmitters and receivers simultaneously from the same base station or mobile unit without interference. The best method to achieve this has been found in the use of filters inserted in the transmission line between the antenna and the transmitter(s) on one hand and the receiver(s) on the other hand. The basic unit employed in the design of microwave filters is usually a cavity resonator of which the most important factors are the Q, insertion loss and resonant frequency. However, a problem which frequently arises with cavity resonators is the accurate determination of these resonant characteristics complicated by the presence of coupling port, materials and various design and geometrical deviations. Such cavities have been investigated in several cases and the results have been generalised, but this investigation has been conducted to examine thoroughly most of the problems being met in present practice. Design and development of some common resonant structures are considered. Emphasis is placed on solutions found to special problems especially regarding complicated boundary conditions. Furthermore, investigation includes methods for optimising resonant parameters such as insertion loss and Q, trading of insertion loss with coupled cavity selectivity, frequency tuning and compensation for frequency variations due to wide ranges of operating temperatures. By comparing Q values obtained in practice with theoretical values, it has been possible to establish an appropriate Q loss budget to as to facilitate accurate prediction of coupled cavity unloaded Q. A satisfactory agreement between theory and practice has been obtained. By application of the results of theoretical analysis and experiment, it is shown that microwave filters can be designed to have a desired insertion loss and off-band attenuation slope. Steps leading to designs of any number of cascaded cavities in a two-port network and, subsequently, multi-port networks are discussed in detail.

In this thesis, we demonstrate an array of photodetection theory and techniques bridging the traditional discrete and continuous variable experimental domains. In quantum optics, the creation and measurement of states of light are intertwined and we present experimental architectures considering both aspects. We describe the measurement of mean photon numbers at optical sideband frequencies using homodyne detection. We use our technique to provide a direct comparison to photon-counting measurements and observe that our technique exhibits superior speed, dynamic range and mode selectivity compared to photon counters. Our analysis also rejects a semiclassical description of the vacuum state, with our observations supporting the quantum mechanical model. We create a new means of describing the detection ???signatures??? of multi-port networks of non-photon-number discriminating detectors. Our model includes the practical effects of loss and dark counts. We use this model to analyse the performance of the loopand balanced- time-division-multiplexed detector architectures in a projective measurement role. Our analysis leads us to describe a prescriptive recipe for the optimisation of each architecture. In light of contemporary technology, we conclude the balanced TDM detector is the better architecture. Our analysis is then extended to the tomographic reconstruction of an unknown optical state using multi-port photon-counting networks. Our new approach is successfully applied to the reconstruction of the photon statistics of weak coherent states and demonstrates reduced error and sensitivity to experimental parameter variations than established techniques. We report the development of a source of quadrature squeezed vacuum at 1550 nm, and characterise the squeezing observed at the first 3 free spectral ranges of the downconversion cavity. This is then used as a source of frequency-entangled photons for a projective photon subtraction operation described by our earlier theory. We propose a new hybrid time/frequency domain approach to homodyne detection and illustrate its application in characterising the prepared state. Our output state has a statistically significant single photon contribution and permits future experimentation in frequency basis quantum information.

Les travaux de cette thèse traitent de l'élaboration d'une méthodologie efficace pour la modélisation des effets parasites dans une carte en large bande de fréquence. La réduction du «Time to Market» pour la conception des produits RF et hyperfréquences nécessite le développement d'une méthode efficace de caractérisation et de modélisation pour mieux prendre en compte les erreurs incluses dans la carte de test.Les principaux résultats concernent les contributions suivantes :- Mise au point des standards de calibrage innovateur pour caractériser et modéliser les effets parasites inhérent au modèle.- Élaboration d'une nouvelle approche basée sur une technique de calibrage TRL et une méthode d’élimination efficace de ces effets.- Application aux dispositifs différentiels lors de l'utilisation du calibrage TRL dans le cas de plusieurs ports.La nouvelle approche proposée pour le calibrage et le de-embedding est appliquée à un dispositif actif qui est actuellement utilisé dans l'industrie. Les résultats de mesure d’un dispositif inclus dans une carte de test ont été comparés à des mesures calibrées à l’aide d’une carte d’évaluation comportant des standards TRL.Cette étude a été prolongée avec le calibrage TRL multi-port pour être utilisé pour la bande large des dispositifs comme les dispositifs différentiels. / The work of this thesis deals with the developing of an efficient methodology for modeling parasitic effects within a broadband board. Reducing “Time to Market” for the design of RF and microwave products necessitates the development of an efficient characterization and modeling methodologies for better calibrating the errors embedded within the test board.Main results concern the following contributions:- Development of an innovative calibration standards to characterize and model the parasitic effects embedded within the model.- Elaboration of a new approach based on a TRL calibration technique and de-embedding method effective to de-embed these effects.- Application on differential devices upon using multi-port TRL calibration.The new proposed approach for calibration and de-embedding is applied to an active device which is being in use in industry nowadays. The measurement result of the device within a load board has been compared to a calibrated measurement using an evaluation board that include TRL standards.This study has been extended with multi-port TRL calibration to be used for large variety of devices like the differential ones.

This work is focused on exploring advanced solutions for space power management and distribution (PMAD) systems. As spacecraft power requirements continue to increase, paralleled by the pressures for reducing cost and overall system weight, power electronics engineers will continue to face major redesigns of the space power systems in order to meet such challenges. Front-end PMAD systems, used to interface the solar sources and battery backup to the distribution bus, need to be designed with increased efficiency, reliability, and power density. A new family of integrated single-stage power converter structures is introduced here. This family allows the interface and control of multiple power sources and storage devices in order to optimize utilization of available resources. Employing single-stage power topologies, these converters control power flow efficiently and cost-effectively. This is achieved by modifying the operation and control strategies of isolated soft-switched half-bridge and full-bridge converters--two of the most popular two-port converter topologies. These topologies are reconfigured and utilized to realize three power processing paths. These paths simultaneously utilize the power devices, allowing increased functionality while promising reduced losses and enhanced power densities. Each of the proposed topologies is capable of performing simultaneous control of two of its three ports. Control objectives include battery or ultra-capacitor charge regulation, solar array maximum power point tracking (MPPT), and/or bus voltage regulation. Another advantage of the proposed power structure is that current engineering design concepts can be used to optimize the new topologies in a fashion similar to the mother topologies. This includes component selection and magnetic design procedures, as well as achieving soft-switching for increased efficiency at higher switching frequencies. Galvanic isolation of the load port through high-frequency transformers provides design flexibility for high step-up/step-down conversion ratios. It further allows the converters to be used as power electronics building blocks (PEBB) with outputs connected in different series/parallel combinations to meet different load requirements. Utilizing such converters promises significant savings in size, weight, and costs of the power management system as well as the devices it manages. Chapter 1 of this dissertation provides an introduction to the requirements, challenges, and trends of space PMAD. A review of existing multi-port converter technologies and digital control techniques is given in Chapter 2. Chapter 3 discusses different PMAD system architectures. It outlines the basic concepts used for PMAD integration and discusses the potential for improvement. Chapters 4 and 5 present and discuss the operation and characteristics of three different integrated multi-port converters. Chapter 6 presents improved methods for practical digital control of switching converters, which are especially useful in complex multi-objective controllers used for PMAD. This is followed by conclusions and suggested future work.

This paper describes the results of research into multi-port converter design and control, specifically a pair of three-port topologies based on the half-bridge and full-bridge topologies. These converters are capable of simultaneous and independent regulation of two out of their three ports, while the third port provides the power balance in the system. A dynamic model was developed for each topology to aid in testing and for designing the control loops. The models were then used to design the control structures, and the results were tested in Simulink. In addition, a basic outline of a system level architecture to control multiple converters working in parallel is presented. To improve the reliability of this system, output current sharing controls were also developed. Finally, one of the topologies is analyzed in detail in order to obtain a set of design equations that can be used to improve the efficiency, weight, and cost of the converter for a specific application.

It is often necessary to operate a number of radio communication channels from a single control room without time-sharing between the various channels. Here it is necessary to operate a number of transmitters and receivers simultaneously from the same base station or mobile unit without interference. The best method to achieve this has been found in the use of filters inserted in the transmission line between the antenna and the transmitter(s) on one hand and the receiver(s) on the other hand. The basic unit employed in the design of microwave filters is usually a cavity resonator of which the most important factors are the Q, insertion loss and resonant frequency. However, a problem which frequently arises with cavity resonators is the accurate determination of these resonant characteristics complicated by the presence of coupling port, materials and various design and geometrical deviations. Such cavities have been investigated in several cases and the results have been generalised, but this investigation has been conducted to examine thoroughly most of the problems being met in present practice. Design and development of some common resonant structures are considered. Emphasis is placed on solutions found to special problems especially regarding complicated boundary conditions. Furthermore, investigation includes methods for optimising resonant parameters such as insertion loss and Q, trading of insertion loss with coupled cavity selectivity, frequency tuning and compensation for frequency variations due to wide ranges of operating temperatures. By comparing Q values obtained in practice with theoretical values, it has been possible to establish an appropriate Q loss budget to as to facilitate accurate prediction of coupled cavity unloaded Q. A satisfactory agreement between theory and practice has been obtained. By application of the results of theoretical analysis and experiment, it is shown that microwave filters can be designed to have a desired insertion loss and off-band attenuation slope. Steps leading to designs of any number of cascaded cavities in a two-port network and, subsequently, multi-port networks are discussed in detail.

With increasing complexity of microwave integrated circuits and tendency towards building integrated modules, real estate in printed circuit boards becomes more at premium. On the other hand, building MIC's on a single semiconductor substrate such as GaAs has other drawbacks as substrate requirements for different components are sometimes contradictory. This has motivated researchers to consider multi-layer and stacked designs. Multi-layer planar circuits offer advantages that cannot be equaled by traditional single layer designs. In this respect, a new class of planar structures, based upon a multi-layered stack of dual-mode stripline or microstrip patches is becoming increasingly popular. In the new stacked design coupling between planar circuits separated by a ground plane is accomplished through coupling apertures in the common ground plane. <br ><br /> This thesis is about developing a new approximate multiport network model for fast analysis of multi-layered planar structures with ground plane slots. To extend applicability of multiport network model (MNM) to the class of planar structures containing ground plane slots, a generalized network formulation for aperture problems is combined with traditional MNM to account for the presence of the slot. To this end, the slot is replaced by an unknown equivalent surface magnetic current. Slot ports are defined in terms of electric and magnetic fields over the slot in accordance with the generalized network formulation for aperture problems. While traditional MNM for planar circuits is based on generalized impedance matrices, we adopt a hybrid matrix approach for multi-layer structures. The hybrid matrix consists of four sub-matrices that relate terminal voltages and currents of edge and slot ports. The same generalized impedance matrix in the absence of the slot can be used to relate terminal voltages and currents of edge ports when the slot ports are short-circuited. Open circuit voltage at edge ports due to terminal voltages at slot ports and terminal currents at slot ports due to input currents at edge ports are represented by two transfer matrices. Both these transfer matrices can be calculated from 2D analysis which only considers <em>TM^z</em> modes. <br ><br /> Interaction among slot ports, represented by a generalized admittance matrix, however, requires considering both <em>TM^z</em> and <em>TE^z</em> modes. This generalized admittance matrix is obtained from tangential component of the magnetic field over the slot due to the equivalent surface magnetic current and relates terminal voltages and currents of slot ports. Full modal expansion consisting of both <em>TM^z</em> and <em>TE^z</em> modes is used to compute the generalized admittance matrix of a slot in a regularly shaped planar cavity. For irregularly shaped patches, modal expansion is not available. Instead, a new contour integral equation for magnetic field, derived for the first time in this thesis, is combined with complex images method for calculation of generalized admittance matrix of a slot radiating in a planar cavity of arbitrary shape. <br ><br /> Once the hybrid matrix representation of a planar circuit on a ground plane containing a slot is derived, it can be connected to the hybrid matrix of any other planar circuit on the other side of the ground plane. This can be done by enforcing network equivalent of continuity of tangential fields across the slot. This leads to a generalized impedance matrix for the multi-layer structure relating terminal voltages and currents of edge ports of both planar circuits. <br ><br /> To show the accuracy of the proposed method of analysis, several proof-of-concept structures have been analyzed by both this method and ANSOFT HFSS full-wave simulator as a reference. In most cases excellent agreement is achieved in predicting the return loss and radiation patterns of these multi-layer structures which proves the validity of the proposed approach for fast analysis and design of multi-layer planar structures.

With increasing complexity of microwave integrated circuits and tendency towards building integrated modules, real estate in printed circuit boards becomes more at premium. On the other hand, building MIC's on a single semiconductor substrate such as GaAs has other drawbacks as substrate requirements for different components are sometimes contradictory. This has motivated researchers to consider multi-layer and stacked designs. Multi-layer planar circuits offer advantages that cannot be equaled by traditional single layer designs. In this respect, a new class of planar structures, based upon a multi-layered stack of dual-mode stripline or microstrip patches is becoming increasingly popular. In the new stacked design coupling between planar circuits separated by a ground plane is accomplished through coupling apertures in the common ground plane. <br ><br /> This thesis is about developing a new approximate multiport network model for fast analysis of multi-layered planar structures with ground plane slots. To extend applicability of multiport network model (MNM) to the class of planar structures containing ground plane slots, a generalized network formulation for aperture problems is combined with traditional MNM to account for the presence of the slot. To this end, the slot is replaced by an unknown equivalent surface magnetic current. Slot ports are defined in terms of electric and magnetic fields over the slot in accordance with the generalized network formulation for aperture problems. While traditional MNM for planar circuits is based on generalized impedance matrices, we adopt a hybrid matrix approach for multi-layer structures. The hybrid matrix consists of four sub-matrices that relate terminal voltages and currents of edge and slot ports. The same generalized impedance matrix in the absence of the slot can be used to relate terminal voltages and currents of edge ports when the slot ports are short-circuited. Open circuit voltage at edge ports due to terminal voltages at slot ports and terminal currents at slot ports due to input currents at edge ports are represented by two transfer matrices. Both these transfer matrices can be calculated from 2D analysis which only considers <em>TM^z</em> modes. <br ><br /> Interaction among slot ports, represented by a generalized admittance matrix, however, requires considering both <em>TM^z</em> and <em>TE^z</em> modes. This generalized admittance matrix is obtained from tangential component of the magnetic field over the slot due to the equivalent surface magnetic current and relates terminal voltages and currents of slot ports. Full modal expansion consisting of both <em>TM^z</em> and <em>TE^z</em> modes is used to compute the generalized admittance matrix of a slot in a regularly shaped planar cavity. For irregularly shaped patches, modal expansion is not available. Instead, a new contour integral equation for magnetic field, derived for the first time in this thesis, is combined with complex images method for calculation of generalized admittance matrix of a slot radiating in a planar cavity of arbitrary shape. <br ><br /> Once the hybrid matrix representation of a planar circuit on a ground plane containing a slot is derived, it can be connected to the hybrid matrix of any other planar circuit on the other side of the ground plane. This can be done by enforcing network equivalent of continuity of tangential fields across the slot. This leads to a generalized impedance matrix for the multi-layer structure relating terminal voltages and currents of edge ports of both planar circuits. <br ><br /> To show the accuracy of the proposed method of analysis, several proof-of-concept structures have been analyzed by both this method and ANSOFT HFSS full-wave simulator as a reference. In most cases excellent agreement is achieved in predicting the return loss and radiation patterns of these multi-layer structures which proves the validity of the proposed approach for fast analysis and design of multi-layer planar structures.

In the present day, owing to the increasing number of electronic loads such as computer power supplies, Compact fluorescent lamps (CFL) and the increasing number of sources such as solar photovoltaics, fuel cells (DC sources), DC Micro-grids provide a more efficient solution compared to the AC counterpart in terms of the number of stages involved in conversion. Also, the ability to be readily buffered to storage elements is an advantage in a DC system. Apart from this, there are no issues of frequency stability, reactive power transfer and ac power losses. A DC micro-grid is effectively a multi-port dc-dc converter. The ports refer to the various sources and loads that are part of the micro-grid. Sources could be unidirectional (as in the case of PV, load) or bidirectional (as in the case of batteries). Interfacing a variety of ports and controlling power flow between these ports presents an interesting challenge. Commonly used topologies interface the various ports at the DC bus capacitor thereby making the DC bus capacitor bulky. Apart from this, the DC bus coupled topologies route power from one port to another via the central capacitor. This increases the number of stages in transferring power from one port to another. An alternative topology is to use the active bridge type converters where dynamic power flow equations are required to control inter-port power flow. But, as the number of stages increase, the computations get tedious.In this thesis, a novel topology is proposed that uses a UU type transformer core to interface all the power ports. This alleviates the problems faced in the DC bus coupled topologies. A PWM scheme to control simultaneous power flow from each of the ports is also proposed in this thesis. The PWM scheme enables the usage of simple constant frequency average current mode control to dynamically control power sharing ratio between the various ports delivering to loads. By means of the proposed PWM scheme and the control scheme, the drawbacks of the active bridge topologies are alleviated. Using the proposed topology and the PWM scheme, a prototype micro-grid system is developed for a system comprising of the utility grid, batteries, solar PVs and resistive loads. Yet another aspect of the thesis explores the concept of connecting multiple micro-grids in order to create a 'local power network'. A potential application for this could be in interconnecting residential buildings and routing power from one house to another in order to balance demand and supply among these houses. This is against the growing trend of using the utility grid to also sink power and subsequently route it to other houses connected to the grid. Unfortunately not all areas have access to the utility grid. Additionally, turning the grid bidirectional requires that a number of standards be met and policies be created. But, the standard for using a local network that only involves a unidirectional grid is fixed by the community that owns such a network. In a crude sense, this scenario can be compared to the existence of a local area network to transfer information among users of the network. In this thesis, a prototype local power network interconnecting two micro-grids has been implemented.

El modelado se ha convertido en los últimos años en una herramienta esencial en el diseño de motores de combustión interna alternativos, ya que permite reducir considerablemente el tiempo y los costes de desarrollo. Las metodologías de diseño clásicas se basan en la fabricación de prototipos y la realización de pruebas de ensayo y error. Actualmente, la mayoría de estas pruebas han sido sustituidas por cálculos numéricos, de modo que sólo las opciones de diseño más prometedoras se prueban en realidad en banco motor. Durante años, los códigos unidimensionales de dinámica de gases en el dominio del tiempo han sido suficientes para modelar tanto las prestaciones y el consumo del motor como el ruido de admisión y escape. Sin embargo, para un nivel más exigente de diseño, una representación 1D puede no ser suficiente para describir con precisión el flujo en ciertos elementos. Esto es especialmente importante en el caso de silenciadores, donde la hipótesis unidimensional sólo se puede aplicar a geometrías simples. En el caso de las uniones de conductos es la existencia de estructuras tridimensionales de flujo complejas lo que establece el límite de la aplicabilidad de una descripción simple cero-dimensional. En vista de estas limitaciones, la primera opción sería el uso de un modelo de dinámica de fluidos computacional (CFD); sin embargo, su aplicación conllevaría un tiempo de cálculo excesivo. Una posible solución de compromiso viene dada por los modelos cuasi-3D, basados en esquemas tridimensionales, pero con ciertas simplificaciones capaces de reducir significativamente el tiempo de cálculo sin afectar excesivamente a la precisión. Tales soluciones se han convertido en estándar en los códigos comerciales y se han aplicado con éxito a los silenciadores, tanto para excitaciones acústicas en el régimen lineal como en condiciones reales de motor, típicamente no lineales. Esta tesis tiene como objetivo el desarrollo de un nuevo método numérico cuasi-3D en una malla escalonada, basado en la simplificación de la ecuación de la cantidad de movimiento, para ser incluido en un código unidimensional existente. Tal método, sin embargo, no está libre de inconvenientes. En particular, se ve afectado por la aparición de oscilaciones no físicas, especialmente en gradientes de presión significativos. De la revisión bibliográfica se determina que este comportamiento es típico en esquemas de segundo orden y se puede ver acentuado por las simplificaciones adoptadas. Tras estudiar las posibles soluciones aplicables a este problema, se desarrollan tres limitadores de flujo diferentes, basados en las metodologías MDT, FCT y TVD. Una vez definido el método numérico y asegurada su estabilidad, es necesario desarrollar las condiciones de contorno adecuadas que permitan su utilización. Con este objetivo, se desarrollan las condiciones de pulso de presión de entrada y de extremo anecoico, los cuales permiten simular un banco de impulso. No hay que olvidar, sin embargo, que el objetivo final es la conexión con un código unidimensional, por lo que hay que comprobar que el método numérico cuasi-3D creado es compatible con los unidimensionales existentes, mostrando algunos resultados preliminares. Finalmente, con el método ya completamente operativo, se procede a su validación en las aplicaciones para las que ha sido diseñado principalmente, las cuales son, modelado de silenciadores y uniones de conductos. Para el caso de los silenciadores, se modelan dispositivos de complejidad creciente, pasando por geometrías de sección constante hasta sistemas con geometrías reales. Los resultados obtenidos se validan con otras herramientas tanto lineales como no lineales. En el caso de las uniones de conductos, el objetivo principal es el de establecer el potencial del nuevo método numérico frente a los tradicionales unidimensionales, por lo que los resultados de ambos se comparan con datos experiment / Engine modelling has become an essential tool in the design of internal combustion engines, allowing considerable reductions in development time and cost. Classical design methodologies are based on prototype manufacturing and trial-and-error tests, but currently, most of those tests have been replaced by numerical computations, so that only the most promising design options are actually tested on engine bench. For years, one-dimensional gas dynamics codes in the time domain have offered sufficiently good solutions for modelling both engine performance and intake and exhaust noise. However, for a more demanding level of design, a 1D representation may not be sufficient to describe accurately the flow in certain elements. This is especially important in the case of silencers. In the case of duct junctions, the existence of complex 3D flow structures is what sets the applicability limit for a simple zero-dimensional description. In view of these limitations, the first option would typically be the use of a computational fluid dynamics (CFD) model; however, the application of such a model to a complete intake or exhaust system entails an excessive computational time. A possible compromise solution is given by quasi-3D models, based on three-dimensional schemes, but with certain simplifications able to significantly reduce the calculation time without excessively affecting the accuracy. Such solutions have become standard in commercial codes and have been successfully applied to silencers with perforated tubes and absorbing material, both in the linear acoustic regime and in real engine conditions, typically non-linear. The objective of this thesis is the development a new quasi-3D numerical method in a staggered-grid, based on the simplification of the momentum equation, to be included in an existing one-dimensional code. Such method however, is not hassle free. In particular, it is affected by the appearance of non-physical oscillations, specially near significant pressure gradients. From the literature review it is determined that this behaviour is typical among second-order schemes and it can be aggravated by the simplifications adopted. After researching the possible solutions to face this problem, three different flux limiters are developed, based on the MDT, FCT and TVD methodologies. In the case of the two latter methods, its effectiveness is well established for finite differences schemes, thus defining a clear improving line for quasi-3D models. Once the numerical method is defined and its stability assured, proper boundary conditions that allow its use must be developed. With this objective, a pressure pulse inlet and an anechoic termination boundary condition are developed, which allow the simulation of an impulse test rig. It should not be forgotten, however, that the ultimate objective is the connection with a one-dimensional code, therefore the compatibility of the quasi-3D numerical method created with the existing one-dimensional methods has to be tested, showing some preliminary results. Eventually, with a fully operative method, the validation process for the applications which it has been mainly developed for, takes place, namely, mufflers and duct junctions modelling. In the case of mufflers, increasingly complex devices are modelled, from constant section geometries to real geometry systems. The results obtained are validated with both linear and non-linear tools. In the case of duct junctions, the main objective is to establish the potential of the new numerical method against the traditional one-dimensional schemes, consequently, results from both approaches are compared to experimental measures, obtaining promising results. / El modelatge s'ha convertit en els últims anys en una eina essencial en el disseny de motors de combustió interna alternatius, ja que permet reduir considerablement el temps i els costos de desenvolupament. Les metodologies de disseny clàssiques es basen en la fabricació de prototips i la realització de proves d'assaig i error. Actualment, la majoria d'aquestes proves han sigut substituïdes per càlculs numèrics, de manera que només les opcions de disseny més prometedores es proven en realitat en banc motor. Durant anys, els codis unidimensionals de dinàmica de gasos en el domini del temps han sigut suficients per a modelar tant les prestacions i el consum del motor com el soroll d'admissió i escapament. No obstant això, per a un nivell més exigent de disseny, una representació 1D pot no ser prou per a descriure amb precisió el flux en certs elements. Açò és especialment important en el cas de silenciadors, on la hipòtesi unidimensional només es pot aplicar a geometries simples. En el cas de les unions de conductes és l'existència d'estructures tridimensionals de flux complexes el que establix el límit de l'aplicabilitat d'una descripció simple zero-dimensional. En vista d'estes limitacions, la primera opció seria típicament l'ús d'un model de dinàmica de fluids computacional (CFD); no obstant això, l'aplicació comporta un temps de càlcul excessiu. Una possible solució de compromís ve donada pels models quasi-3D, basats en esquemes tridimensionals, però amb certes simplificacions capaços de reduir significativament el temps de càlcul sense afectar excessivament la precisió. Tals solucions s'han convertit en estàndard en codis comercials i s'han aplicat amb èxit als silenciadors, tant per a excitacions acústiques en el règim lineal com en condicions reals de motor, típicament no lineals. Aquesta tesi té com a objectiu el desenvolupament d'un nou mètode numèric quasi-3D en una malla escalonada, basat en la simplificació de l'equació de la quantitat de moviment, per a ser inclòs en un codi unidimensional existent. Tal mètode, però, no està lliure d'inconvenients. En particular, es veu afectat per l'aparició d'oscil·lacions no físiques, especialment en gradients de pressió significatius. De la revisió bibliogràfica es determina que aquest comportament és típic en esquemes de segon ordre i es pot veure accentuat per les simplificacions adoptades. Després d'estudiar les possibles solucions aplicables a aquest problema, es desenvolupen tres limitadors de flux diferents, basats en les metodologies MDT, FCT i TVD. En el cas dels dos últims mètodes, la seua efectivitat està ben establida per als esquemes de diferències finites, la qual cosa definix una clara via de millora per als models quasi-3D. Una vegada definit el mètode numèric i assegurada la seua estabilitat, és necessari desenvolupar les condicions de contorn adequades que permeten la seua utilització. Amb aquest objectiu, es desenvolupen les condicions de pols de pressió d'entrada i d'extrem anecoic, els quals permeten simular un banc d'impuls. No cal oblidar que l'objectiu final és la connexió amb un codi unidimensional, per la qual cosa cal comprovar que el mètode numèric cuasi-3D creat és compatible amb els unidimensionals existents, mostrant alguns resultats preliminars. Finalment, es procedix a la seua validació en les aplicacions per a les que ha sigut dissenyat principalment, les quals són, modelatge de silenciadors i unions de conductes. Per al cas dels silenciadors, es modelen dispositius de complexitat creixent, passant per geometries de secció constant fins a sistemes amb geometries reals. Els resultats obtinguts es validen amb altres eines tant lineals com no lineals. En el cas de les unions de conductes, l'objectiu principal és el d'establir el potencial del nou mètode numèric front als unidimensionals tradicionals, per la qual cosa els resultats d'ambdós es comparen amb dades experim / Hernández Marco, M. (2018). A non-linear quasi-3D model for air management modelling in engines [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/103683 / TESIS