In gas stirred steelmaking ladles, entrainment of slag into metal and vice versa takes place. The slag entrainment has been shown to abruptly increase the mass transfer rates of refining reactions through high temperature and water modeling studies of the past. However such an effect has not been correlated with the degree of entrainment, since the latter has not been quantified in terms of operating parameters like gas injection rate and fluid properties. Much of the past works are limited to finding the critical conditions for onset of entrainment. The difficulty lies in measuring the degree of entrainment in industrial ladles or even in a water model. Mathematical modeling is also challenging due to the complexity of the multiphase phenomena. So in this thesis, a modular mathematical modeling approach is presented wherein the phenomena of slag entrainment into metal is resolved into four aspects, models developed for each and finally integrated to study its role. The individual models are (1) multiphase large eddy simulations to simulate slag entrainment in a narrow domain that receives its boundary conditions from (2) single phase RANS simulation of a full ladle, (3) a Lagrangian particle tracking method to compute the residence times of slag droplets in metal phase and (4) a kinetic model that integrates the above three models to compute mass transfer rate as a function of degree of entrainment. Mass transfer rate predictions comparable to a literature correlation were obtained. This supports the modeling approach and also the assessment of role of various system parameters on entrainment characteristics. In essence, the present work shows a systematic approach to model and study the complex multiphase phenomena. / Thesis / Doctor of Philosophy (PhD) / The entrainment of liquid slag into liquid steel in gas stirred-steelmaking ladles is known to increase the rate of refining drastically. However, there is lack of correlation between degree of entrainment and ladle operating conditions, which this thesis addresses through mathematical modeling.

The work presented in this dissertation is the first numerical investigation conducted to study leading edge film cooling with Large Eddy Simulation (LES). A cylindrical leading edge with a flat after-body represents the leading edge, where coolant is injected with a 30Ë compound angle. Three blowing ratios of 0.4, 0.8, and 1.2 are studied. Free-stream Reynolds number is 100,000 and coolant-to-mainstream density ratio is unity. At blowing ratio of 0.4, the effect of coolant inlet condition is investigated. Results show that the fully-turbulent coolant jet increases mixing with the mainstream in the outer shear layer but does not influence the flow dynamics in the turbulent boundary layer at the surface. As a result, the turbulent jet decreases adiabatic effectiveness but does not have a substantial effect on the heat transfer coefficient. At B.R.=0.4, three types of coherent structures are identified which consist of a primary entrainment vortex at the leeward aft-side of the coolant hole, vortex tubes at the windward side of the coolant hole, and hairpin vortices typical of turbulent boundary layers produced by the turbulent interaction of the coolant and mainstream downstream of injection. At B.R. = 0.8 and 1.2, coherent vortex tubes are no longer discernable, whereas the primary vortex structure gains in strength. In all cases, the bulk of the mixing occurs by entrainment which takes place at the leeward aft-side of the coolant jet. This region is characterized by a low pressure core and the primary entrainment vortex. Turbulent shear interaction between coolant jet and mainstream increases substantially with blowing ratio and contributes to the dilution of the coolant jet. As a result of the increased mixing in the shear layer and primary structure, adiabatic effectiveness decreases and heat transfer coefficient increases with increase in blowing ratio. The dissertation also investigates the deposition and erosion of Syngas ash particles in the film cooled leading edge region. Three ash particle sizes of 1, 5, and 10 microns are investigated at all blowing ratios using Lagrangian dynamics. The 1 micron particles with momentum Stokes number St = 0.03 (based on approach velocity and cylinder diameter), show negligible deposition/erosion. The 10 micron particles, on the other hand with a high momentum Stokes number, St = 3, directly impinge and deposit on the surface, with blowing ratio having a minimal effect. The 5 micron particles with St=0.8, show the largest receptivity to coolant flow and blowing ratio. On a mass basis, 90% of deposited mass is from 10 micron particles, with 5 micron particles contributing the other 10%. Overall there is a slight decrease in deposited mass with increase in blowing ratio. About 0.03% of the total incoming particle energy can potentially be transferred as erosive energy to the surface and coolant hole, with contribution coming from only 5 micron particles at B.R.=0.4 and 0.8, and both 5 and 10 micron particles at B.R.=1.2. / Ph. D.

The collisions frequency of dispersed phases (particles, droplets, bubbles) in a turbulent carrier phase is a fundamental quantity that is needed for modeling multiphase flows with applications to chemical processes, minerals flotation, food science, and many other industries. In this dissertation, numerical simulations are performed to determine collisions frequency of bi-dispersed particles (solid particles and bubbles) in homogeneous isotropic turbulence. Both direct numerical simulations (DNS) and Large Eddy simulations (LES) are conducted to determine velocity fluctuations of the carrier phase. The DNS results are used to validate existing theoretical models as well as the LES results. The dissertation also presents a CFD-based flotation model for predicting the pulp recovery rate in froth flotation machines. In the direct numerical simulations work, particles and bubbles suspended in homogeneous isotropic turbulence are tracked and their collisions frequency is determined as a function of particle Stokes number. The effects of the dispersed phases on the carrier phase are neglected. Particles and bubbles of sizes on the order of Kolmogorov length scale are treated as point masses. Equations of motion of dispersed phases are integrated simultaneously with the equations of the carrier phase using the same time stepping scheme. In addition to Stokes drag, the pressure gradient in the carrier phase and added-mass forces are also included. The collision model used here allows overlap of particles and bubbles. Collisions kernel, radial relative velocity, and radial distribution function found by DNS are compared to theoretical models over a range of particle Stokes number. In general, good agreement between DNS and recent theoretical models is obtained for radial relative velocity for both particle-particle and particle-bubble collisions. The DNS results show that around Stokes number of unity particles of the same group undergo expected preferential concentration while particles and bubbles are segregated. The segregation behavior of particles and bubbles leads to a radial distribution function that is less than one. Existing theoretical models do not account for effects of this segregation behavior of particles and bubbles on the radial distribution function. In the large-eddy simulations efforts, the dissertation addresses the importance of the subgrid fluctuations on the collisions frequency and investigates techniques for predicting those fluctuations. The cases studied are of particles-particles and particles-bubbles collisions at Reynolds number Re_λ = 96. A study is conducted first by neglecting the effects of subgrid velocity fluctuations on particles and bubbles motions. It is found that around Stokes number of unity solid particles of the same group undergo the well known preferential concentration as observed in the DNS. Effects of pressure gradient on the particles are negligible due to their small sizes. Bubbles as a low inertia particles are very sensitive to subgrid velocity and acceleration fields where the effects of pressure gradient in the carrier phase are dominant. However, particle-bubble radial distribution functions from LES are not as low as that from DNS. To account for the effects of subgrid field on the dispersion of particles and bubbles, a new multifractal methodology has been developed to construct a subgrid vorticity field from the resolved vorticity field in frame work of LES. A Poisson's solver is used to obtain the subgrid velocity field from the subgrid vorticity field. Accounting for the subgrid velocity fluctuations (but neglecting pressure gradient) produced minor changes in the radial distribution function for particle-particle and particle-bubble collisions. We conclude from this study that for accurate particle tracking in LES the subgrid velocity fluctuations must be dynamically realizable field (temporally and spatially correlated with the large scale motion). Adding random SGS velocity fluctuations is not enough to capture the correct radial distribution functions of dispersed phases especially for bubbles-particles collisions where the pressure gradient term ( or acceleration Du_f′/Dt) is responsible for particle-bubble segregation around particle Stokes number near one. A CFD-based model for minerals flotation machines has been developed in this dissertation. The objective of flotation models is to predict the recovery rate of minerals from a flotation cell. The developed model advances the state-of-the-art of pulp recovery rate prediction by incorporating validated theoretical collisions frequency models and detailed hydrodynamics from two-phase flow simulations. Spatial distributions of dissipation rate and air volume fraction are determined by the two-phase hydrodynamic simulations. Knowing these parameters throughout the machine is essential in understanding the effectiveness of different components of flotation machine (rotor, stator or disperser, jets) on the flotation efficiency. The developed model not only predicts the average pulp recovery rate but also it indicates regions of high/low recovery rates. The CFD-based flotation model presented here can be used to determine the dependence of recovery rate constant at any locality within the pulp based on particle diameter, particle specfic gravity, contact angle, and surface tension. / Ph. D.

Coal gasification and combustion can introduce contaminants in the solid or molten state depending on the gas clean up procedures used, coal composition and operating conditions. These byproducts when combined with high temperatures and high gas stream velocities can cause Deposition, Erosion, and Corrosion (DEC) of turbine components downstream of the combustor section. The objective of this dissertation is to use computational techniques to investigate the dynamics of ash deposition in a leading edge vane geometry with film cooling. Large Eddy Simulations (LES) is used to model the flow field of the coolant jet-mainstream interaction and the deposition of syngas ash in the leading edge region of a turbine vane is modeled using a Lagrangian framework. The three row leading edge vane geometry is modeled as a symmetric semi-cylinder with a flat afterbody. One row of coolant holes is located along the stagnation line and the other two rows of coolant holes are located at ±21.3° from the stagnation line. The coolant is injected at 45° to the vane surface with 90° compound angle injection. The coolant to mainstream density ratio is set to unity and the freestream Reynolds number based on leading edge diameter is 32000. Coolant to mainstream blowing ratios (B.R.) of 0.5, 1.0, 1.5, and 2.0 are investigated. It is found that the stagnation cooling jets penetrate much further into the mainstream, both in the normal and lateral directions, than the off-stagnation jets for all blowing ratios. Jet dilution is characterized by turbulent diffusion and entrainment. The strength of both mechanisms increases with blowing ratio. The adiabatic effectiveness in the stagnation region initially increases with blowing ratio but then generally decreases as the blowing ratio increases further. Immediately downstream of off-stagnation injection, the adiabatic effectiveness is highest at B.R.=0.5. However, in spite of the larger jet penetration and dilution at higher blowing ratios, the larger mass of coolant injected increases the effectiveness with blowing ratio further downstream of injection location. A novel deposition model which integrates different sources of published experimental data to form a holistic numerical model is developed to predict ash deposition. The deposition model computes the ash sticking probabilities as a function of particle temperature and ash composition. This deposition model is validated with available experimental results on a flat plate inclined at 45°. Subsequently, this model was then used to study ash deposition in a leading edge vane geometry with film cooling for coolant to mainstream blowing ratios of 0.5, 1.0, 1.5 and 2.0. Ash particle sizes of 5, 7, 10μm are considered. Under the conditions of the current simulations, ash particles have Stokes numbers less than unity of O(1) and hence are strongly affected by the flow and thermal fields generated by the coolant interaction with the main-stream. Because of this, the stagnation coolant jets are successful in pushing and/or cooling the particles away from the surface and minimizing deposition and erosion in the stagnation region. Capture efficiency for eight different ash compositions are investigated. Among all the ash samples, ND ash sample shows the highest capture efficiency due to its low softening temperature. A trend that is common to all particle sizes is that the percentage capture efficiency is least for blowing ratio of 1.5 as the coolant is successful in pushing the particles away from the surface. However, further increasing the blowing ratio to 2.0, the percentage capture efficiency increases as more number of particles are transported to the surface by strong mainstream entrainment by the coolant jets. / Ph. D.

This thesis describes several approaches for stabilizing POD-ROMs (that is, reduced order models based on basis functions derived from the proper orthogonal decomposition) for both the CDR (convection-diffusion-reaction) equation and the NSEs (Navier-Stokes equations). Stabilization is necessary because standard POD-ROMs of convection-dominated problems usually display numerical instabilities. The first stabilized ROM investigated is a streamline-upwind Petrov-Galerkin ROM (SUPG-ROM). I prove error estimates for the SUPG-ROM and derive optimal scalings for the stabilization parameter. I test the SUPG-ROM with the optimal parameter in the numerical simulation of a convection-dominated CDR problem. The SUPG-ROM yields more accurate results than the standard Galerkin ROM (G-ROM) by eliminating the inherent numerical artifacts (noise) in the data and dampening spurious oscillations. I next propose two regularized ROMs (Reg-ROMs) based on ideas from large eddy simulation and turbulence theory: the Leray ROM (L-ROM) and the evolve-then-filter ROM (EF-ROM). Both Reg-ROMs use explicit POD spatial filtering to regularize (smooth) some of the terms in the standard G-ROM. I propose two different POD spatial filters: one based on the POD projection and a novel POD differential filter. These two new Reg-ROMs and the two spatial filters are investigated in the numerical simulation of the three-dimensional flow past a circular cylinder problem at Re = 100. The numerical results show that EF-ROM-DF is the most accurate Reg-ROM and filter combination and the differential filter generally yields better results than the projection filter. The Reg-ROMs perform significantly better than the standard G-ROM and decrease the CPU time (compared against the direct numerical simulation) by orders of magnitude (from about four days to four minutes). / Ph. D.

Jet engines often operate under dirty conditions where large amounts of particulate matter can be ingested, especially, sand, ash and dirt. Particulate matter in different engine components can lead to degradation in performance. The objective of this dissertation is to investigate sand transport and deposition in the internal cooling passages of turbine blades. A simplified rectangular geometry is simulated to mimic the flow field, heat transfer and particle transport in a two pass internal cooling geometry. Two major challenges are identified while trying to simulate particle deposition. First, no reliable particle-wall collision model is available to calculate energy losses during a particle wall interaction. Second, available deposition models for particle deposition do not take into consideration all the impact parameters like impact velocity, impact angle, and particle temperature. These challenges led to the development of particle wall collision and deposition models in the current study. First a preliminary simulation is carried out to investigate sand transport and impingement patterns in the two pass geometry by using an idealized elastic collision model with the walls of the duct without any deposition. Wall Modeled Large Eddy Simulations (WMLES) are carried to calculate the flow field and a Lagrangian approach is used for particle transport. The outcome of these simulations was to get a qualitative comparison with experimental visualizations of the impingement patterns in the two pass geometry. The results showed good agreement with experimental distributions and identified surfaces most prone to deposition in the two pass geometry. The initial study is followed by the development of a particle-wall collision model based on elastic-plastic deformation and adhesion forces by building on available theories of deformation and adhesion for a spherical contact with a flat surface. The model calculates deformation losses and adhesion losses from particle-wall material properties and impact parameters and is broadly applicable to spherical particles undergoing oblique impact with a rigid wall. The model is shown to successfully predict the general trends observed in experiments. To address the issue of predicting deposition, an improved physical model based on the critical viscosity approach and energy losses during particle-wall collisions is developed to predict the sand deposition at high temperatures in gas turbine components. The model calculates a sticking or deposition probability based on the energy lost during particle collision and the proximity of the particle temperature to the softening temperature. For validation purposes, the deposition of sand particles is computed for particle laden jet impingement on a coupon and compared with experiments conducted at Virginia Tech. Large Eddy Simulations are used to calculate the flow field and heat transfer and particle dynamics is modeled using a Lagrangian approach. The results showed good agreement with the experiments for the range of jet temperatures investigated. Finally the two pass geometry is revisited with the developed particle-wall collision and deposition model. Sand transport and deposition is investigated in a two pass internal cooling geometry at realistic engine conditions. LES calculations are carried out for bulk Reynolds number of 25,000 to calculate flow and temperature field. Three different wall temperature boundary conditions of 950 oC, 1000 oC and 1050 oC are considered. Particle sizes in the range 5-25 microns are considered, with a mean particle diameter of 6 microns. Calculated impingement and deposition patterns are discussed for different exposed surfaces in the two pass geometry. It is evident from this study that at high temperatures, heavy deposition occurs in the bend region and in the region immediately downstream of the bend. The models and tools developed in this study have a wide range of applicability in assessing erosion and deposition in gas turbine components. / Ph. D.

The main objective of this PhD thesis is the study of Diesel sprays under evaporative conditions by means of Large Eddy Simulations (LES) techniques. This study has been performed implementing a precise, low-demanding LES model in the free, full-purpose Computational Fluid Dynamics (CFD) code OpenFOAM. The starting point was a careful and exhaustive review of the physical processes involved in sprays. An emphasis in CFD methodology, particularly for LES methods, was essential for the thesis, as we were able to find the possible problems and limitations of our approximation. Moreover, as the most widely used techniques for the industrial simulation of sprays are based on the Reynolds-Averaged Navier-Stokes models, we have highlighted the many advantages of LES modeling. As the latter are, by definition, more computationally expensive than RANS, we made an optimal configuration that, while it is able to recover accurately the experimental results, its characteristic time is in the same order of magnitude that RANS ones. As applicability is a must in this thesis, we use the surname ¿Engineering¿ LES. One of the key points of the thesis has been the correct configuration of the flow turbulent conditions on the inlet. In order to get accurate results, the turbulent structures coming from this inlet need to be time- and spacecoherent. An adequate calibration of this conditions is needed to perform any spray simulation. Last but not least, all the simulations performed where validated against experiments, obtaining a very good agreement even close to the nozzle / Mompó Laborda, JM. (2014). Engineering Large Eddy Simulation of Diesel Sprays [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/37345

[ES] En los últimos años, el interés por el desarrollo de motores de aviación limpios y eficientes se ha incrementado debido al impacto perjudicial sobre la salud y el medio ambiente ocasionado por los sistemas de combustión convencionales. En este contexto, la comunidad científica ha ido centrando cada vez más sus esfuerzos en el estudio de la combustión turbulenta y la generación de emisiones contaminantes como las partículas de hollín. Con los recientes avances en lo que respecta a potencia de cálculo, las simulaciones de alta fidelidad emergen como una valiosa alternativa para reproducir y analizar estos fenómenos. En concreto, las simulaciones basadas en el modelado de la turbulencia LES son consideradas como una de las herramientas numéricas más prometedoras a la hora de profundizar en la comprensión sobre los complejos procesos dinámicos que caracterizan el flujo reactivo turbulento y predecir emisiones de hollín en aplicaciones aeronáuticas. En el presente trabajo, se estudia y analiza la combustión turbulenta y producción de hollín en aplicaciones de turbina de gas mediante LES de alta fidelidad. El modelado de la combustión se aborda a través de un método flexible de química tabulada basado en el concepto flamelet, el cual es capaz de representar fenómenos químicos complejos con un coste computacional asequible. Además, se emplea una aproximación Euleriana-Lagrangiana para la descripción de la fase gaseosa y las gotas, de forma que se represente correctamente el flujo reactivo multifásico. Para la predicción de hollín en simulaciones computacionalmente eficientes, se emplea un novedoso enfoque de modelado basada en el método seccional y acoplada al modelo de combustión de química tabulada. Esta estrategia de modelado numérica es utilizada en este trabajo para analizar el proceso de combustión y evaluar sus capacidades para predecir hollín y las características de la llama en quemadores de turbina de gas representativos. En primer lugar, se estudia la combustión de flujo bifásico en una llama atmosférica sin torbellinador con inyección líquida de combustible. Este quemador presenta una estructura doble del frente reactivo y las simulaciones numéricas son capaces de capturar adecuadamente los fenómenos de extinción local que tienen lugar en la zona interna de la llama debido a la interacción de las gotas y la turbulencia con el frente reactivo. Posteriormente, se investiga la combustión y producción de hollín en un quemador presurizado con torbellinador que incluye aire secundario de dilución en el interior de la cámara de combustión. La validación del flujo reactivo y hollín se lleva a cabo tanto en la configuración del quemador con aire secundario como sin el mismo, mostrando unas excelentes capacidades predictivas en ambos casos. La presente estrategia de modelado reproduce de forma precisa el complejo patrón de flujo, la estructura de la llama y la dinámica de generación de hollín, además de que es capaz de proporcionar diferentes distribuciones de tamaño de partícula dependiendo de las variaciones en los procesos de formación y oxidación del hollín. En resumen, los diferentes casos prácticos estudiados permiten consolidar y validar la metodología computacional seguida en la presente tesis. La estrategia de modelado basada en química tabulada propuesta demuestra ser lo suficientemente válida y adecuada para reproducir los complejos fenómenos de la combustión y la formación de hollín, en vista de la consistencia del análisis, las precisas predicciones y la concordancia satisfactoria con las medidas experimentales. / [CA] En els últims anys, l'interés pel desenvolupament de motors d'aviació nets i eficients s'ha incrementat a causa de l'impacte perjudicial sobre la salut i el medi ambient ocasionat pels sistemes de combustió convencionals. En aquest context, la comunitat científica ha anat centrant cada vegada més els seus esforços en l'estudi de la combustió turbulenta i la generació d'emissions contaminants com les partícules de sutge. Amb els recents avanços pel que fa a potència de càlcul, les simulacions d'alta fidelitat emergeixen com una valuosa alternativa per a reproduir i analitzar aquests fenòmens. En concret, les simulacions basades en el modelatge de la turbulència LES són considerades com una de les eines numèriques més prometedores a l'hora d'aprofundir en la comprensió sobre els complexos processos dinàmics que caracteritzen el flux reactiu turbulent i predir emissions de sutge en aplicacions aeronàutiques. En el present treball, s'estudia i analitza la combustió turbulenta i la producció de sutge en aplicacions de turbina de gas mitjançant LES d'alta fidelitat. El modelatge de la combustió s'aborda a través d'un mètode flexible de química tabulada basat en el concepte flamelet, el qual és capaç de representar fenòmens químics complexos amb un cost computacional assequible. A més, s'empra una aproximació Euleriana-Lagrangiana per a la descripció de la fase gasosa i les gotes, de manera que es represente correctament el flux reactiu multifàsic. Per a la predicció de sutge en simulacions computacionalment eficients, s'empra un nou plantejament de modelatge basat en el mètode seccional i acoblat al model de combustió de química tabulada. Aquesta estratègia de modelatge numèrica és utilitzada en aquest treball per a analitzar el procés de combustió en cremadors de turbina de gas representatius, i avaluar les seues capacitats per a predir sutge i les característiques de la flama. En primer lloc, s'estudia la combustió de flux bifàsic en una flama atmosfèrica sense remolinador amb injecció líquida de combustible. Aquest cremador presenta una estructura doble del front reactiu i les simulacions numèriques són capaces de capturar adequadament els fenòmens d'extinció local que tenen lloc en la zona interna de la flama a causa de la interacció de les gotes i la turbulència amb el front reactiu. Posteriorment, s'investiga la combustió i producció de sutge en un cremador pressuritzat amb remolinador que inclou aire secundari de dilució a l'interior de la cambra de combustió. La validació del flux reactiu i sutge es duu a terme tant en la configuració del cremador amb aire secundari com sense aquest, mostrant unes estupendes capacitats predictives en tots dos casos. La present estratègia de modelatge reprodueix de manera precisa el complex patró de flux, l'estructura de la flama i la dinàmica de generació de sutge, a més de que és capaç de proporcionar diferents distribucions de grandària de partícula depenent de les variacions en els processos de formació i oxidació del sutge. En resum, els diferents casos pràctics estudiats permeten consolidar i validar la metodologia computacional seguida en la present tesi. L'estratègia de modelatge basada en química tabulada proposada demostra ser prou vàlida i adequada per a reproduir els complexos fenòmens de la combustió i la formació de sutge, en vista de la consistència de l'anàlisi, les precises prediccions i la concordança satisfactòria amb les mesures experimentals. / [EN] In recent years, interest in the development of efficient and clean aviation powerplants has increased due to the detrimental impact on health and the environment caused by conventional combustion systems. In this context, the research community has increasingly focused its efforts on the study of turbulent combustion and the generation of pollutant emissions such as soot particulates. With recent advances in computational power, high-fidelity simulations emerge as a valuable alternative to reproduce and analyze these phenomena. Specifically, Large Eddy Simulations (LES) are considered as one of the most promising numerical tools to provide further insight into the complex dynamic processes that characterize reactive turbulent flows and predict soot emissions in aeronautical applications. In the present work, turbulent combustion and soot production is studied and analyzed in gas turbine engine applications by means of high-fidelity LES. Combustion modelling is addressed by a flexible tabulated chemistry method based on the flamelet concept, which is able to represent complex chemical phenomena with an affordable computational cost. In addition, an Eulerian- Lagrangian description is employed for the gas phase and droplets in order to correctly represent the multiphase flow in spray flames. A recently developed approach based on the sectional method and coupled to the tabulated chemistry framework is considered for soot prediction in computationally efficient simulations. This numerical modelling framework is used in this work to analyze the combustion process and evaluate its capabilities to predict soot and flame characteristics in representative gas turbine burners. First, an atmospheric non-swirled spray flame is studied in terms of two-phase flow combustion. This burner shows a double reaction front structure and local extinction occurs in the inner layer due to both droplet-flame and turbulence-flame interactions, which is properly characterized by LES. Subsequently, combustion and soot production is investigated in a pressurized swirled model combustor which includes secondary dilution jets inside the combustion chamber. The assessment of the reacting flow field and soot is addressed for burner configurations with and without secondary air, showing excellent predictive capabilities in both cases. The present modelling approach accurately reproduce the complex swirled flow field, flame structure and soot dynamics and is able to provide different particle size distributions depending on the variations of the soot formation and oxidation processes. In summary, the different practical cases studied allow to consolidate and validate the computational methodology followed in the present thesis. The proposed tabulated modelling strategy is sufficiently valid and suitable for reproducing complex combustion and soot formation phenomena, in view of the consistency of the analysis, the accurate predictions and the satisfactory agreement with the experimental measurements. / El desarrollo de la presente tesis ha sido posible gracias a una ayuda para la Formación de Profesorado Universitario (FPU 18/03065) perteneciente al Subprograma Estatal de Formación del Ministerio de Ciencia, Innovación y Universidades de España. Además, el trabajo desarrollado está enmarcado en el proyecto ESTiMatE (Emissions SooT ModEl), que ha sido financiado por el consorcio Clean Sky 2 bajo el programa de investigación e innovación Horizonte 2020 de la Unión Europea (acuerdo No. 821418). Las actividades de simulación numérica han sido posibles gracias a la Red Española de Supercomputación y al Centro de Supercomputación de Barcelona por los recursos computacionales proporcionados en MareNostrum, además del grupo PRACE por conceder el acceso a HAWK (GCS, HLRS, Alemania) a través del proyecto SootAero. / Olmeda Ramiro, I. (2023). Assessment of Detailed Combustion and Soot Models for High-Fidelity Aero-Engine Simulations [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/202284

No description available.

Efficient temporal resolution and spatial grids are important in simulation of the inflow turbulence for wind turbine loads analyses. There have not been many published studies that address optimal space-time resolution of generated inflow velocity fields in order to estimate accurate load statistics. This study investigates turbine extreme and fatigue load statistics for a utility-scale 5MW wind turbine with a hub-height of 90 m and a rotor diameter of 126 m. Load statistics, spectra, and time-frequency analysis representations are compared for various alternative space and time resolutions employed in inflow turbulence field simulation. Conclusions are drawn regarding adequate resolution in space of the inflow turbulence simulated on the rotor plane prior to extracting turbine load statistics. Similarly, conclusions are drawn with regard to what constitutes adequate temporal filtering to preserve turbine load statistics. This first study employs conventional Fourier-based spectral methods for stochastic simulation of velocity fields for a neutral atmospheric boundary layer. In the second part of this study, large-eddy simulation (LES) is employed with similar resolutions in space and time as in the earlier Fourier-based simulations to again establish turbine load statistics. A comparison of extreme and fatigue load statistics is presented for the two approaches used for inflow field generation. The use of LES-generated flows (enhanced in deficient high-frequency energy by the use of fractal interpolation) to establish turbine load statistics in this manner is computationally very expensive but the study is justified in order to evaluate the ability of LES to be used as an alternative to more common approaches. LES with fractal interpolation is shown to lead to accurate load statistics when compared with stochastic simulation. A more compelling reason for using LES in turbine load studies is the following: for stable boundary layers, it is not possible to generate realistic inflow velocity fields using stochastic simulation. The present study presents a demonstration that, despite the computational costs involved, LES-generated inflows can be used for loads analyses for utility-scale turbines. The study sets the stage for future computations in the stable boundary layer where low-level jets, large speed and direction shears across the rotor, etc. can possibly cause large turbine loads; then, LES will likely be the inflow turbulence generator of choice. / text