After the restriction of different halogenated fire suppressants by the Montreal Protocol, there is an urgent need to identify environmentally friendlier alternatives. In particular, several efforts have been conducted to find substitutes of Halon 1301 (CF_(3)Br) which was considered the best in its class, not only because of its superior extinguishing performance, but also due to its relatively low toxicity. Different options have been proposed over the last decade. However, no single compound has been found to meet all of the exigent criteria. Further progress in this research requires fundamental combustion knowledge that can help us understand the unique performance of Halon 1301, to prevent this search from becoming a tedious trial-and-error process. To this end, the present work aids in the search of fire suppressants alternatives by improving the flame inhibition mechanism understanding, starting with CF_(3)Br, which serves as a benchmark for new fire suppressants. Then, a case study of two of the most currently used fire suppressants, C_(2)HF_(5) (HFC-125) and C_(2)HF_(7) (HFC-227), is presented and compared with CF_(3)Br performance. For these analyses, a systematic analytical methodology was used to examine the effect of fire suppressants on ignition and laminar flame propagation of C_(1)-C_(3) alkanes premixed mixtures, as good representatives of flammable gas fires (Class B fires). This methodology integrates model formulations and experimental designs in order to examine both chemical kinetics and thermal effects on fire suppressants at different stoichiometric conditions. Modeling predictions were based on a detailed chemical kinetics mechanism which was assembled from a new, well-studied H_(2), C_(0)–C_(5) hydrocarbon mechanism from NUI Galway and recent CF_(3)Br and HFC fire suppressant chemistry from NIST. Experimental study involved the use of a shock tube (for ignition analysis) and a freely expanding flame speed bomb (for laminar flame speed analysis). Most of the experimental data provided in this work are the first measurements of their kind for the compounds and mixtures explored in this thesis. These measurements are extremely valuable since they can be used as a metric for model validation which represents one of the objectives of this work. Current analyses indicate that the combustion properties of halogenated compounds cannot be generalized and depends on different factors. On one hand, the presented results showed that all the tested fire suppressants can decrease the laminar flame speed of the examined C_(1)-C_(3)alkanes premixed flames; however, in some cases they can act as ignition promoters. In order to understand these behaviors, sensitivity analyses were conducted showing that halogenated species, resulting from the fire suppressants decomposition, can participate in both promoting and inhibiting reactions that compete to give a net effect. Identification of the key reaction responsible for such effects was conducted. Then, improvements on the fire suppressant chemistry can be done by modifying the corresponding Arrhenius parameters of such important reactions. This work not only provides fundamental knowledge of halogenated flame inhibition mechanisms, but also serves as the basis for more accurate chemical kinetics mechanisms that can be used for better predictions over a wide range of conditions.

Population growth and increasing standards of living have resulted in a rapid demand for energy. Our primary energy production is still dominated by fossil fuels. This extensive usage of fossil fuels has led to global warming, environmental pollution, as well as the depletion of hydrocarbon resources. The prevailing difficult situation offers not only a challenge but also an opportunity to search for alternatives to fossil fuels. Hence, there is an urgent need to explore environmentally friendly and cost-effective renewable energy sources. Oxygenates (alcohols, ethers) and ammonia are among the potential renewable alternative fuels of the future. This thesis investigates the combustion characteristics of promising alternative fuels and their blends using a combination of experimental and modelling methodologies. The studied fuels include ethanol, diethyl ether, dimethyl ether, dimethoxy methane, γ-valerolactone, cyclopentanone, and ammonia. For the results presented in this thesis, the studies may be classified into three main categories: 1. Ignition delay time measurements of ethanol and its blends by using a rapid compression machine and a shock tube. The blends studied include binary mixtures of ethanol/diethyl ether and ternary mixtures of ethanol/diethyl ether/ethyl levulinate. A chemical kinetic model has been constructed and validated over a wide range of experimental conditions. The results showed that a high-reactivity fuel, diethyl ether, may be blended with a low-reactivity fuel, ethanol, in varying concentrations to achieve the desired combustion characteristics. A ternary blend of ethanol/diethyl ether/ethyl levulinate may be formulated from a single production stream, and this blend is shown to behave similarly to a conventional gasoline. 2. Ignition delay time and flame speed measurements of ammonia blended with combustion promoters by utilizing a rapid compression machine and a constant volume spherical reactor. The extremely low reactivity of ammonia makes it unsuitable for direct use in many combustion systems. One of the potential strategies to utilize ammonia is to blend it with a combustion promoter. In this work, dimethyl ether, diethyl ether, and dimethoxy methane are explored as potential promoters of ammonia combustion. Chemical kinetic models were developed and validated in the high temperature regime by using flame speed data and in the low-to-intermediate temperature regime by using ignition delay time data. The results showed that even a small addition (~ 5 – 10%) of combustion promoters can significantly alter ammonia combustion, and diethyl ether was found to have the highest propensity to enhance ammonia ignition and flame propagation. Blends of combustion promoters with ammonia can thus be utilized in modern downsized turbo-charged engines. 3. Octane boosting and emissions minimization effects of next generation oxygenated biofuels. These studies were carried out using a cooperative fuel research engine operating in a homogenous charge compression ignition (HCCI) mode. The oxygenated fuels considered here include γ-valerolactone and cyclopentanone. The results showed that γ-valerolactone and cyclopentanone can be effective additives for octane boosting and emission reduction of conventional fuels. Overall, the results and outcomes of this thesis will be highly useful in choosing and optimizing alternative fuels for future transportation systems.

Following stringent mandates from environmental regulatory authorities worldwide, various steps are being implemented to ensure clean combustion with minimum emissions, including fuel dilution, mild combustion and additives. Due to the need to understand combustion characteristics in primary applications (engines and turbines) with minimum emissions, the laminar burning velocity of natural gas has been measured with CO2 dilution and a wide range of blends with higher hydrocarbons. And because it has improved anti-knock quality to reduce greenhouse gas emissions (GHGE), the demand for oxygenated gasoline is now worldwide, making a compelling case for determining combustion behavior of oxygenated gasoline doped with hydrogen, ozone and carbon monoxide. The first section of this dissertation discusses dilution of methane with CO2 at elevated pressures, providing insight into comparative laminar burning characteristics in a wide range of equivalence ratios, particularly significant at elevated initial pressure. Utilizing CHEMKIN, a detailed kinetic study has been performed that explains the varying dependence on dilution ratio controlled by initial pressure. The second phase of this work reports the laminar burning velocity measurement of commercial gasoline. A TPRFE surrogate was used here to investigate burning characteristics and to provide detailed kinetic analysis of gasoline doped with additives (hydrogen, carbon monoxide and ozone). A study was also made of the behavior of gasoline with these additives in practical applications like engine and turbines. For this purpose, laminar burning velocity was measured at elevated pressures and temperatures, by varying the concentrations of synthetic EGR, and followed by measuring turbulent burning velocity at two turbulent intensities.

There is a great interest to develop biomass combustion systems for industrial and utility applications. Improved biomass energy conversion systems are designed to provide better combustion efficiencies and environmental friendly conditions, as well as the fuel flexibility options in various applications. The gas derived from the gasification process of biomass is considered as one of the potential candidates to substitute traditional fuels in a combustion process. However, the gascomposition from the gasification process may have a wide range of variation depending on the methods and fuel sources. The better understanding of the combustion features for the Gasified Biomass Gas(GBG) is essential for the development of combustion devices to be operated efficiently and safely at the user-end. The objective of the current study is therefore aiming to achieve data associated with the combustion features of GBG fuel for improving the efficiency and stability of combustion process. The numerical result is achieved from the kinetic models of premixed combustion with a wide range of operating ranges and variety of gas compositions. The numerical result is compared with experimental data to provide a better understanding of the combustion process for GBG fuel. In this thesis the laminar flame speed and ignition delay time of the GBG fuel are analyzed, using 1-D premixed flame model and constant volume model respectively. The result from different kinetics are evaluated and compared with experimental data. The influences of initial temperature, pressure and equivalence ratio are considered, as well as the variation of gas compositions. While the general agreement is reached between the numerical result and experimental data for laminarflame speed prediction, deviations are discovered at fuel-rich region and increased initial temperature. For the ignition delay time, deviations are found in the low-temperature and low pressure regime. The empirical equations considering the influence of initial temperature,pressure and equivalence ratio are developed for laminar flame speed and ignition delay times. The influence of major compositions such as CO, H2 and hydrocarbons are discussed in details in the thesis. Furthermore, a simplified kinetic model is developed and optimized based on the evaluation of existing kinetics for GBG fuel combustion. The simplified kinetic model is expected to be used for simulating the complexc ombustion process of GBG fuel in future studies. / <p>QC 20150511</p>

Coal derived synthetic gas (syngas) fuel is a promising solution for today s increasing demand for clean and reliable power. Syngas fuels are primarily mixtures of H2 and CO, often with large amounts of diluents such as N2, CO2, and H2O. The specific composition depends upon the fuel source and gasification technique. This requires gas turbine designers to develop fuel flexible combustors capable of operating with high conversion efficiency while maintaining low emissions for a wide range of syngas fuel mixtures. Design tools often used in combustor development require data on various fundamental gas combustion properties. For example, laminar flame speed is often an input as it has a significant impact upon the size and static stability of the combustor. Moreover it serves as a good validation parameter for leading kinetic models used for detailed combustion simulations. Thus the primary objective of this thesis is measurement of laminar flame speeds of syngas fuel mixtures at conditions relevant to ground-power gas turbines. To accomplish this goal, two flame speed measurement approaches were developed: a Bunsen flame approach modified to use the reaction zone area in order to reduce the influence of flame curvature on the measured flame speed and a stagnation flame approach employing a rounded bluff body. The modified Bunsen flame approach was validated against stretch-corrected approaches over a range of fuels and test conditions; the agreement is very good (less than 10% difference). Using the two measurement approaches, extensive flame speed information were obtained for lean syngas mixtures at a range of conditions: 1) 5 to 100% H2 in the H2/CO fuel mixture; 2) 300-700 K preheat temperature; 3) 1 to 15 atm pressure, and 4) 0-70% dilution with CO2 or N2. The second objective of this thesis is to use the flame speed data to validate leading kinetic mechanisms for syngas combustion. Comparisons of the experimental flame speeds to those predicted using detailed numerical simulations of strained and unstrained laminar flames indicate that all the current kinetic mechanisms tend to over predict the increase in flame speed with preheat temperature for medium and high H2 content fuel mixtures. A sensitivity analysis that includes reported uncertainties in rate constants reveals that the errors in the rate constants of the reactions involving HO2 seem to be the most likely cause for the observed higher preheat temperature dependence of the flame speeds. To enhance the accuracy of the current models, a more detailed sensitivity analysis based on temperature dependent reaction rate parameters should be considered as the problem seems to be in the intermediate temperature range (~800-1200 K).

La vitesse de flamme laminaire représente une grandeur physique clé à mesurer car elle permet d'obtenir des données fondamentales sur la réactivité, la diffusivité et l'exothermicité du carburant. Elle est également un des paramètres utilisés pour le développement et la validation des mécanismes réactionnels détaillés ainsi que pour la modélisation de la combustion turbulente. Bien que cette grandeur physique ait fait l'objet de nombreuses études expérimentales depuis plusieurs décennies, sa méconnaissance sur des carburants multi-composant dans des conditions haute-pression et haute-température similaires à celles existantes dans les chambres de combustion reste un sujet d'actualité pour les industriels des secteurs automobile et aéronautique. Au cours de cette thèse, un brûleur de configuration bec Bunsen fonctionnant avec un prémélange gazeux combustible/air a été conçu pour produire une flamme laminaire à pression élevée tout en permettant la mesure par voie optique de la vitesse de flamme laminaire de carburants multi-composant (kérosène, biocarburants de seconde génération...). La mesure est basée sur la détection du contour de flamme par diverses diagnostics optiques comme la chimiluminescence OH*, la PLIF-OH et la PLIF-acétone/aromatique. En premier lieu, les mélanges de carburants purs gazeux (CH4) ou liquide (acétone) avec de l'air ont été étudiés pour valider le brûleur expérimental et la méthodologie de mesure de la vitesse de flamme laminaire par voie optique. Les évolutions de la vitesse de flamme laminaire pour des carburants de type kérosène (composants purs, surrogate LUCHE et Jet A-1) en fonction de la pression, température de préchauffage et richesse ont été ensuite étudiées et comparées avec des simulations numériques utilisant un mécanisme réactionnel détaillé. La dernière partie de la thèse est consacrée à l'étude de l'influence des composés oxygénés présents dans un biocarburant de seconde génération de type d'essence sur la vitesse de flamme laminaire. Après avoir mesuré la vitesse de flamme laminaire de différentes molécules oxygénées, les effets d'addition de ces composés oxygénés dans le carburant ont été quantifiés / Laminar flame speed is one of the key parameters for understanding reactivity, diffusivity and exothermicity of fuels. It is also useful to validate both the kinetic chemical mechanisms as well as turbulent models. Although laminar flame speeds of many types of fuels have been investigated over many decades using various combustion methodologies, accurate measurements of laminar flame speeds of multicomponent liquid fuels in high-pressure and high-temperature conditions similar to the operating conditions encountered in aircraft/automobile combustion engines are still required. In this current study, a high-pressure combustion chamber was specifically developed to measure the laminar flame speed of multicomponent liquid fuels such as kerosene and second generation of biofuels. The architecture of the burner is based on a preheated premixed Bunsen flame burner operated in elevated pressure and temperature conditions. The optical diagnostics used to measure the laminar flame speed are based on the detection of the flame contour by using OH* chemiluminescence, OH- and acetone/aromatic- Planar laser induced fluorescence (PLIF). The laminar flame speed of gaseous CH4/air and acetone/air premixed laminar flames were first measured for validating the experimental setup and the measurement methodologies. Then, the laminar flame speeds of kerosene or surrogate fuels (neat kerosene compounds, LUCHE surrogate kerosene and Jet A-1) were investigated and compared with simulation results using detailed kinetic mechanisms over a large range of conditions including pressure, temperature and equivalence ratio. The last part of the thesis was devoted to study the effect of oxygenated compounds contained in the second generation of biofuels on the laminar flame speeds. After measuring the laminar flame speeds of various oxygenated components present in partially hydro-processed lignocellulosic biomass pyrolysis oils, the effect of these oxygenates on the flame speeds of these fuels were quantitatively investigated

High-pressure experiments and chemical kinetics modeling were performed for laminar spherically expanding flames for methane/air, ethane/air, methane/ethane/air and propane/air mixtures at pressures between 1 and 10 atm and equivalence ratios ranging from 0.7 to 1.3. All experiments were performed in a new flame speed facility capable of withstanding initial pressures up to 15 atm. The facility consists of a cylindrical pressure vessel rated up to 2200 psi. Vacuums down to 30 mTorr were produced before each experiment, and mixtures were created using the partial pressure method. Ignition was obtained by an automotive coil and a constant current power supply capable of reducing the spark energy close to the minimum ignition energy. Optical cine-photography was provided via a Z-type schlieren set up and a high-speed camera (2000 fps). A full description of the facility is given including a pressure rating and a computational conjugate heat transfer analysis predicting temperature rises at the walls. Additionally, a detailed uncertainty analysis revealed total uncertainty in measured flame speed of approximately +-0.7 cm/s. This study includes first-ever measurements of methane/ethane flame speeds at elevated pressures as well as unique high pressure ethane flame speed measurements. Three chemical kinetic models were used and compared against measured flame velocities. GRI 3.0 performed remarkably well even for high-pressure ethane flames. The C5 mechanism performed acceptably at low pressure conditions and under-predicted the experimental data at elevated pressures. Measured Markstein lengths of atmospheric methane/air flames were compared against values found in the literature. In this study, Markstein lengths increased for methane/air flames from fuel lean to fuel rich. A reverse trend was observed for ethane/air mixtures with the Markstein length decreasing from fuel lean to fuel rich conditions. Flame cellularity was observed for mixtures at elevated pressures. For both methane and ethane, hydrodynamic instabilities dominated at stoichiometric conditions. Flame acceleration was clearly visible and used to determine the onset of cellular instabilities. The onset of flame acceleration for each high-pressure experiment was recorded.

This thesis investigates the laminar flame speed of C₁-C₃ alkanes and their binary mixtures at conditions of interest in natural gas based gas turbines viz. high temperature, pressure and dilution. Laminar flame speed has been found useful not only for validating chemical kinetics mechanisms but also for developing empirical scaling laws for practical combustion systems. The thesis addresses the lack of laminar flame speed data of C₁-C₃ alkanes at preheat (300-650 K), pressure (1-10 atm) and significant oxidizer dilution (15-21 vol% O₂). Over 400 measurements are reported over a wide range of conditions along with comparison to predictions from leading chemical mechanisms. Unstretched flame speed measurements were performed using a modified Bunsen flame technique based on reaction zone area from chemiluminescence imaging, whereas the strain sensitivity measurements were performed using a bluff-body stabilized stagnation flame with high resolution PIV. These measurements are used to: (i) discern the uncertainties associated with the measurements, (ii) understand the effect of fuel mixture and vitiation on flame speed, and (iii) validate the performance of the leading chemical kinetics mechanisms. Extensive testing shows the unstretched flame speed measurements from the modified Bunsen technique are reasonably accurate. Vitiation studies for methane and propane flames at high preheat show the reduction in flame speed results primarily from the thermal effect of the diluent and that the relative change in flame speed from the undiluted mixture is well correlated to the fractional change in the adiabatic flame temperature over a range of conditions. Significant difference in the measured and predicted flame speeds were observed for rich, atmospheric pressure, propane and lean, high pressure, methane/ethane mixtures with dilution. This highlights possible avenues for improvements in the chemical kinetics mechanisms. Systematic errors were also identified in the Bunsen flame measurements at certain conditions, such as for rich flames with dilution, indicating a need for better understanding of the Bunsen flame technique at these conditions. The difference in the measured and predicted flame speed does not show any clear correlation with the flame height or the strain sensitivity of the mixture. Finally previously proposed mixing rules for estimating flame speed of fuel mixtures from pure fuel components are shown to be reasonably accurate over a range of pressure, reactant temperature and dilution conditions.

No description available.

Tesis por compendio / [ES] El objetivo principal de esta tesis es establecer una metodología para predecir el consumo de combustible y las emisiones de un motor de encendido por compresión en condiciones transitorias. Además, su objetivo es explorar cómo las diferentes configuraciones del motor y los factores ambientales impactan el comportamiento del motor utilizando un enfoque de modelado 0D/1D. Además, el estudio pretende extender esta metodología a los motores duales, analizando específicamente las características de combustión de metano-diésel e hidrógeno-diésel. Para lograrlo, la herramienta de modelado 0D/1D se ajustó y validó meticulosamente utilizando un motor diésel de cuatro cilindros. Esta alineación entre la simulación y datos experimentales se centró especialmente en factores cruciales como la presión, la liberación de calor, las temperaturas en los fluidos del motor y el par. Se realizó un análisis exhaustivo del Balance Energético Global (GEB) utilizando VEMOD (Virtual Engine Model). Este análisis proporcionó información detallada sobre el consumo del motor y su reacción en diversas condiciones de funcionamiento, particularmente durante el Ciclo de ensayo mundial armonizado de vehículos ligeros (WLTC). La comparación de términos energéticos entre diferentes condiciones ambientales y de motor destacó aspectos como la fricción, la transferencia de calor y la acumulación de calor. Además, el análisis GEB permitió explorar cómo se distribuía la energía con diferentes temperaturas y altitudes ambientes. El estudio también evaluó las emisiones de NOx, revelando patrones influenciados por factores como las tasas de recirculación de gases de escape (EGR) y la temperatura de admisión. En el ámbito de los motores de combustible dual, se elaboró y validó un modelo de combustión utilizando la herramienta de simulación 0D/1D. La atención inicial se centró en la combustión de metano-Diesel, validada con datos experimentales. Posteriormente, el alcance de este modelo se amplió para simular la combustión de hidrógeno-Diesel. Esta tesis ha introducido con éxito una metodología que utiliza VEMOD para predecir el consumo y las emisiones del motor en distintos escenarios. El análisis exhaustivo arrojó luz sobre cómo funcionan los mecanismos de distribución de energía y cómo diferentes factores influyen en el comportamiento del motor. La aplicación de esta metodología a motores de encendido por compresión ha demostrado su versatilidad y capacidad de predicción, lo que la convierte en una herramienta valiosa para investigar escenarios futuros, también con combustiones duales. / [CA] L'objectiu principal d'aquesta tesi és establir una metodologia per predir el consum de combustible i les emissions d'un motor d'encesa per compressió en condicions transitòries. A més, pretén explorar com diferents configuracions de motors i factors ambientals afecten el comportament del motor mitjançant un enfocament de modelització 0D/1D. A més, l'estudi s'esforça a estendre aquesta metodologia als motors de doble combustible (duals), analitzant específicament les característiques de combustió de metà-dièsel i hidrogendièsel. Per aconseguir-ho, l'eina de modelització 0D/1D es va ajustar minuciosament i es va validar mitjançant un motor dièsel de quatre cilindres. Aquesta alineació entre dades de simulació i món real es va centrar especialment en factors crucials com la pressió, l'alliberament de calor, les temperatures dels fluids del motor i el parell. Es va realitzar una anàlisi completa del Balanç Global d'Energia (GEB) mitjançant VEMOD (Virtual Engine Model). Aquesta anàlisi va proporcionar una visió profunda sobre el consum del motor i la seua reacció en diverses condicions de funcionament, especialment durant el Cicle mundial d'assaig de vehicles lleugers harmonitzats (WLTC). La comparació de termes energètics entre diferents condicions ambientals i del motor van posar de manifest aspectes com la fricció, la transferència de calor i l'acumulació de calor. A més, l'anàlisi GEB va explorar com es va distribuir l'energia amb diferents temperatures i altituds ambientals. L'estudi també va valorar les emissions de NOx, revelant patrons influenciats per factors com la recirculació de gasos d'escapament (EGR) i la temperatura d'admissió. En l'àmbit dels motors duals, es va elaborar i validar un model de combustió mitjançant l'eina de simulació 0D/1D. El focus inicial es va centrar en la combustió metà-Diesel, validada amb dades experimentals. Posteriorment, l'abast d'aquest model es va ampliar per simular la combustió hidrogen-Diesel. Aquesta tesi ha introduït amb èxit una metodologia que utilitza VEMOD per predir el consum i les emissions del motor en diferents escenaris. L'anàlisi completa va donar llum a com funcionen els mecanismes de distribució d'energia i com diferents factors influeixen en el comportament del motor. L'aplicació d'aquesta metodologia als motors d'encesa per compressió va demostrar la seva versatilitat i capacitats de predicció, convertint-la en una valuosa eina per investigar els futurs escenaris, fins i tot amb combustions duals. / [EN] The main aim of this thesis is to establish a methodology for predicting fuel consumption and emissions of a compression ignition engine in transient conditions. Additionally, it aims to explore how different engine setups and environmental factors impact the engine's performance using a 0D/1D modelling approach. Moreover, the study strives to extend this methodology to dual fuel engines, specifically analysing methane-Diesel and hydrogen- Diesel combustion characteristics. The 0D/1D modelling tool was meticulously fine-tuned and validated using a four-cylinder Diesel engine to achieve this. This alignment between simulation and experimental data focused on crucial factors such as pressure, heat release, engine fluid temperatures and torque. A comprehensive Global Energy Balance (GEB) analysis was conducted using VEMOD (Virtual Engine Model). This analysis provided insights into the engine consumption and performance under diverse operating conditions, particularly during the Worldwide Harmonized Light Vehicles Test Cycle (WLTC). The comparison of energy terms across different engine and boundary conditions highlighted aspects such as friction, heat rejection, and heat accumulation. Additionally, the GEB analysis allowed exploration of how energy was split across varying ambient temperatures and altitudes. The study also assessed NOx emissions, revealing patterns influenced by factors such as Exhaust Gas Recirculation (EGR) rates and intake temperature. A combustion model was developed and validated using the 0D/1D simulation tool in the scope of dual fuel engines. The initial focus was on methane-Diesel combustion, validated against experimental data. Subsequently, this model scope was expanded to simulate hydrogen-Diesel combustion. This thesis has successfully introduced a methodology based on VEMOD to predict engine consumption and emissions across varying scenarios. The comprehensive analysis illuminated how energy distribution mechanisms operate and how factors influence engine performances. The application of this methodology to compression ignition engines demonstrated its versatility and prediction capabilities, making it a valuable tool for investigating future combustion scenarios, including dual fuel operation. / This research has been partially funded by the European Union’s Horizon 2020 Framework Programme for research, technological development and demonstration under grant agreement 723976 (“DiePeR”) and by the Spanish government under the grant agreement TRA2017-89894-R (”MECOEM”) and I was supported by FPI grant with reference PRE2018-084411. / Artham, S. (2023). Contribution to the simulation of new standard testing cycles by means of a 0D/1D tool [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/201238 / Compendio