This thesis is about modelling of the combustion and emissions of dual fuel HCCI engines for design of “engine combustion system”. For modelling the combustion first the laminar flamelet model and a hybrid Lagrangian / Eulerian method are developed and implemented to provide a framework for incorporating detailed chemical kinetics. This model can be applied to an engine for the validation of the chemical kinetic mechanism. The chemical kinetics, reaction rates and their equations lead to a certain formula for which the coefficients can be obtained from different sources, such as NASA polynomials [1]. This is followed by study of the simulation results and significant findings. Finally, for investigation of the knock phenomenon some characteristics such as compression ratio, fuel equivalence ratio, spark timing and their effects on the performance of an engine are examined and discussed. The OH radical concentration (which is the main factor for production of knock) is evaluated with regard to adjustment of the above mentioned characteristic parameters. In the second part of this work the specification of the sample engine is given and the results obtained from simulation are compared with experimental results for this sample engine, in order to validate the method applied in AVL Fire software. This method is used to investigate and optimize the effects of parameters such as inlet temperature, fuels ratio, diesel fuel injection timing, engine RPM and EGR on combustion in a dual fuel HCCI engine. For modelling the dual fuel HCCI engine AVL FIRE software is applied to simulate the combustion and study the optimization of a combustion chamber design. The findings for the dual fuel HCCI engine show that the mixture of methane and diesel fuel has a great influence on an engine's power and emissions. Inlet air temperature has also a significant role in the start of combustion so that inlet temperature is a factor in auto-ignition. With an increase of methane fuel, the burning process will be more rapid and oxidation becomes more complete. As a result, the amounts of CO and HC emissions decrease remarkably. With an increase of premixed ratio beyond a certain amount, NOX emissions decrease. With pressure increases markedly and at high RPM, knock phenomenon is observed in HCCI combustion.

Actuellement, les principaux thèmes pour le secteur de transport sont le réchauffement global et la crise énergétique, ce qui encourage les chercheurs à développer des technologies alternatives et efficaces. Le concept ‘HCCI’ (combustion d’une charge homogène, allumée par compression) est l’une des solutions pour le moteur de véhicules. Ce mode de combustion, indépendant d’une notion de propagation de flamme, permet de réduire fortement les émissions critiques de NOX et de suies dans les gaz d'échappement. Cette combustion de type HCCI du carburant diesel se caractérise par une combustion à deux étapes. Parallèlement, l’apparition de nouveaux carburants, comme le bio-alcool, est une autre voie de recherche. Les bio-alcools ont un nombre d’indice d'octane élevé qui peut se mélanger avec du carburant diesel pour optimiser la combustion de HCCI des carburants diesel. L’objectif de cette thèse est donc de caractériser les deux étapes de la combustion HCCI en étudiant l’influence de l’impact de l’ajout d’une fraction d’alcools dans diesel. La comparaison avec un mélange d’iso-octane, hydrocarbure à indice d'octane élevé de paraffine et des mélanges dilués via les gaz d’échappement est aussi analysée en tant que verrous potentiels pour améliorer la combustion de type HCCI. Dans cette thèse, le n-heptane est choisi comme composé principal représentatif du diesel, l'éthanol et 1-butanol sont choisis comme bio-alcools. L’analyse présentée ici se repose sur trois approches différentes : l’analyse expérimentale de la pression cylindre, l'analyse d'images de chimiluminescence spontanée de certaines espèces et les résultats issus de la modélisation cinétique de la combustion. / Currently, the major issues for the transportation sector are the global warming and energy crisis which encourage researchers to develop an alternative green efficient technology. The homogeneous charge compression ignition (HCCI) can be one of solutions for the automotive engine. This combustion concept is independent on the high temperature flame propagation which releases lowest critical emissions (NOX and PM) in the exhaust gas. HCCI combustion of diesel fuel presents specific characteristic of two-stage ignition that over-advances the main heat release. As the importance of bio-alcohol fuels increases, it is interesting to evaluate the potential of the fuels, to optimize the HCCI combustion of diesel fuels. This is the objective of this phD thesis. The two-stage ignition characteristic of the diesel hydrocarbon is described and the influence of alcohol fuel fraction in diesel blends is investigated in comparison with high octane paraffin hydrocarbon diesel blends and EGR addition. All potentials are concluded to the potential for HCCI combustion improvement. In this thesis, n-heptane was selected as the major diesel representative component and ethanol and 1-butanol as the considered alcohol fuels. Three approaches were used based on experimental cylinder pressure analysis, the chemiluminescence emissions image analysis and the chemical kinetic analysis results from the engine modeling. A detailed chemical kinetic scheme was specifically developed from sub-scheme of all considered fuel.

This thesis is about modelling of the combustion and emissions of dual fuel HCCI engines for design of “engine combustion system”. For modelling the combustion first the laminar flamelet model and a hybrid Lagrangian / Eulerian method are developed and implemented to provide a framework for incorporating detailed chemical kinetics. This model can be applied to an engine for the validation of the chemical kinetic mechanism. The chemical kinetics, reaction rates and their equations lead to a certain formula for which the coefficients can be obtained from different sources, such as NASA polynomials [1]. This is followed by study of the simulation results and significant findings. Finally, for investigation of the knock phenomenon some characteristics such as compression ratio, fuel equivalence ratio, spark timing and their effects on the performance of an engine are examined and discussed. The OH radical concentration (which is the main factor for production of knock) is evaluated with regard to adjustment of the above mentioned characteristic parameters. In the second part of this work the specification of the sample engine is given and the results obtained from simulation are compared with experimental results for this sample engine, in order to validate the method applied in AVL Fire software. This method is used to investigate and optimize the effects of parameters such as inlet temperature, fuels ratio, diesel fuel injection timing, engine RPM and EGR on combustion in a dual fuel HCCI engine. For modelling the dual fuel HCCI engine AVL FIRE software is applied to simulate the combustion and study the optimization of a combustion chamber design. The findings for the dual fuel HCCI engine show that the mixture of methane and diesel fuel has a great influence on an engine's power and emissions. Inlet air temperature has also a significant role in the start of combustion so that inlet temperature is a factor in auto-ignition. With an increase of methane fuel, the burning process will be more rapid and oxidation becomes more complete. As a result, the amounts of CO and HC emissions decrease remarkably. With an increase of premixed ratio beyond a certain amount, NOX emissions decrease. With pressure increases markedly and at high RPM, knock phenomenon is observed in HCCI combustion.

No description available.

Depuis plusieurs années, l’une des problématiques sociétales est de diminuer les émissions de polluants et de gaz à effet de serre dans l’atmosphère. Le secteur du transport terrestre est directement concerné par ces considérations. Le moteur Diesel semble promis à un bel avenir grâce à son rendement supérieur à celui du moteur à allumage commandé, conduisant à de plus faibles rejets de CO2. Cependant, sa combustion génère des émissions d’oxyde d’azote (NOx) et de particules dans l’atmosphère. Les normes anti-pollution étant de plus en plus sévères et les incitations à diminuer les consommations de carburant de plus en plus fortes, le moteur Diesel est confronté à une problématique NOx/particules/consommation toujours plus difficile à résoudre. Une des voies envisagées consiste à modifier le mode de combustion afin de limiter les émissions polluantes à la source tout en conservant de faibles consommations. La voie la plus prometteuse est la combustion HCCI (Homogeneous Charge Compression Ignition) obtenue par injections directes précoces. Plusieurs limitations critiques doivent cependant être revues et améliorées : le mouillage des parois par le carburant liquide et le contrôle de la combustion à forte charge. Le but de cette thèse est ainsi de mieux comprendre les phénomènes mis en jeu lors de la combustion HCCI à forte charge obtenue par des multi-injections directes précoces. Une méthodologie a été mise au point afin de détecter le mouillage des parois du cylindre, ce qui a permis de comprendre l’effet du phasage et de la pression d’injection sur cette problématique. Une stratégie optimale de multi-injections permettant d’atteindre une charge élevée sans mouiller les parois a ainsi été développée et choisie. Nous avons ensuite pu mettre en évidence le potentiel de la stratification par la dilution en tant que moyen de contrôle de la combustion en admettant le diluant dans un seul des 2 conduits d’admission. Des mesures réalisées en complémentarité sur le même moteur mais en version ‘optique’, ont permis, à partir de la technique de Fluorescence Induite par Laser, de montrer que concentrer le diluant dans les zones réactives où se situe le carburant permet un meilleur contrôle de la combustion, ce qui permet d’amener le taux de dilution a des niveaux faisables technologiquement. / For several years, reduce pollutant and greenhouse gas emissions in the atmosphere is become a leitmotiv. The automotive world is directly affected by these considerations. Diesel engine has a promising future thanks to its efficiency higher than that of S.I. engine, leading to lower CO2 emissions. However, Diesel combustion emits nitrogen oxides (NOx) and particulates in the atmosphere. Emissions regulations are more and more severe, and considerations about fuel consumption are more and more significant. Thus, Diesel engine has to face a NOx/particulates/consumption issue that is more and more difficult to answer. One of the considered ways to reduce pollutant emissions while maintaining low fuel consumptions is to change the combustion mode. The most promising way is Homogeneous Charge Compression Ignition (HCCI) combustion with early direct injections. However, two major issues have to be answered: the wall wetting and the combustion control at high load. Thus, the objective of this PhD thesis is to better understand phenomena occurring during HCCI combustion at high load with early direct injections in order to answer these issues. We have developed a new methodology to detect the cylinder wall wetting process. This allowed to understand the effects of injection phasing and injection pressure on this issue. A multiple injections strategy has been tested and improved. It reaches a high load without cylinder wall wetting. Then, we have highlighted the potential of dilutant stratification as a technique of control of combustion. This technique is based on the introduction of dilutant in one inlet pipe while air is introduced in the other. The use of Laser Induced Fluorescence imaging on the same engine but with optical accesses showed that condensing dilutant in the reactive zones where the fuel is improves combustion control and allows the use of reasonable dilution level.

The principle of controlled auto-ignition (CAI) is to mix fuel and air homogeneously before compressing the mixture to the point of auto-ignition. As ignition occurs simultaneously, CAI engines operate with lean mixtures preventing high cylinder pressures. CAI engines produce small amounts of nitrogen oxides (NOx) due to low combustion temperatures while maintaining high compression ratios and engine efficiencies. Due to simultaneous combustion and lean mixtures, CAI engines are restricted between low and mid load operations. Various strategies have been studied to improve the load limit of CAI engines. The scope of the project is to investigate the consequences of varying valve timing, as a method to control the mixture temperature within the combustion chamber and therefore, controlling the mixture auto-ignition point. This study presents computational fluid dynamics (CFD) modelling results of transient flow, inside a 0.45 litre Lotus single cylinder engine. After a validation process, a chemical kinetics model is combined with the CFD code, in order to study in-cylinder temperatures, the mixture distribution during compression and to predict the auto-ignition timing. The first part of the study focuses on validating the calculated in-cylinder velocities. A mesh sensitivity study is performed as well as a comparison of different turbulence models. A method to reduce computational time of the calculations is presented. The effects of engine speed on charge delay and charge amount inside the cylinder, the development of the in-cylinder flow field and the variation of turbulence parameters during the intake and compression stroke, are studied. The second part of the study focuses on the gasoline mixture and the variation of the valve timing, to retain different ratios of residual gases within the cylinder. After validation of the model, a final set of CFD calculations is performed, to investigate the effects of valve timing on flow and the engine parameters. The results are then compared to a fully homogeneous mixture model to study the benefits of varying valve duration. New key findings and contributions to CAI knowledge were found in this investigation. Reducing the intake and exhaust valve durations created a mixture temperature stratification and a fuel concentration distribution, prior to auto-ignition. It resulted in extending the heat release rate duration, improving combustion. However, shorter valve timing durations also showed an increase in heat transfer, pumping work and friction power, with a decrease of cylinder indicated efficiency. Valve timing, as a method to control auto-ignition, should only be used when the load limit of CAI engines, is to be improved.

Dans un contexte de recherche de nouveaux modes de combustion propres, la combustionhomogène à allumage par compression HCCI s’inscrit comme une stratégie prometteuse.Cependant, cette combustion est limitée par un niveau élevé de bruit. La recherche descarburants permettant de relaxer cette contrainte constitue l’objectif global de cette étude.Particulièrement, on s’intéresse ici à l’influence de l’Indice de Cétane, de la volatilité et de lacomposition chimique des carburants sur les Délais d’Auto-Inflammation et sur les vitesses decombustion globales évaluées par les taux maximaux d’accroissement de la pression et dudégagement d’énergie apparente. L’étude se base dans un premier temps sur l’analyse d’essaissur banc moteur dans lesquels on a testé plusieurs carburants de synthèse à l’état pur et enmélange avec un Gazole conventionnel. Dans un deuxième temps des essais ont été préparés etréalisés sur Machine à Compression Rapide avec deux configurations en injection directe et enmélange homogène. Les essais Moteur ont permis d’orienter les paramètres expérimentauxciblés sur ce dispositif. D’autre part, pour étudier les régimes de combustion, des mesures dechamps de température locale ont été réalisées en mélange inerte (N2, CO2, Ar) par FluorescenceInduite par Laser avec un traceur Toluène. L’étude montre les limites des paramètres habituelspour caractériser l’adéquation carburant combustion HCCI et propose un nouveau critère basésur la dépendance des délais d’auto-inflammation à la température et à la richesse. / Advanced combustion strategies such as Homogeneous Charge Compression Ignition (HCCI)usually enable cleaner combustion with less NOx and Particulate Matter emissions comparedto conventional Diesel combustion. However, these strategies are difficult to implement due todifficulties related to combustion timing and burn rate control. Lately various studies have beenfocusing on extending advanced combustion functioning with new technologies and withsearching fuels properties to enable such combustion modes. This study is focused on theimpact of fuel Cetane Number, volatility and chemical composition on Ignition Delay, HeatRelease Rate and Pressure Rise Rate. The study is based on three complementary experiments.First, several synthetic fuel was tested on a research engine and analysis was focused on theHeat Release Rate. Secondly, experiments on a Rapid Compression Machine were performedto study the auto-ignition phenomena at homogeneous conditions with surrogate fuels (blendsof n-Heptane and Methyl-Cyclohexane). Analysis of the combustion regimes was supported bya study of the temperature field based on a Toluene Laser Induced Fluorescence experiment ininert (N2, CO2, Ar) mixture. Finally, the RCM was adapted to allow direct injection of fuel tostudy the auto-ignition at less homogeneous conditions. Results showed the limits of theconventional fuels properties to describe an adequate fuel formulation for the HCCI combustionmode. A new criterion based on the dependency of ignition delays to temperature and air fuelratio variations is proposed.

Increasing the efficiency of the spark-ignition engine can help to reduce the environmental impact of the transportation sector. Engine knock obstructs the increased efficiency that could be gained by increasing the compression ratio in a spark-ignition (SI) engine. A fuel’s propensity to knock is measured by the research octane number (RON) and the motor octane number (MON) in a co-operative fuel research (CFR) engine. A fuel’s octane sensitivity (OS) is the difference between the RON and MON. Modern downsized and turbocharged engines operate at what is considered to be beyond-RON conditions. Studies have shown that having a fuel with higher OS improves knock resistance at beyond-RON conditions. This study aims to gain a better understanding of the role of intermediate-temperature heat release (ITHR) in defining OS and its subsequent impact on SI operation through the experimental framework. The ITHR of toluene primary reference fuels (TPRFs) fuels with matching RON and varying OS was studied at RON-like and MON-like homogeneous charge compression ignition (HCCI) conditions for two different matching criteria. The first criterion was to control the combustion phasing by matching half of the heat release (CA50) to 3 crank angle degrees after top dead center. The second criterion was to match the compression ratios. Results showed that at RON-like HCCI conditions, TPRF fuels display decreasing ITHR with increasing OS. Furthermore, it was shown that TPRF fuels with low sensitivity displayed a greater increase in ITHR from MON-like conditions to RON-like conditions. Thus, the sensitivity of ITHR to changes in operating conditions was found to be a contributing factor to OS. In the beyond-RON conditions (relevant to current modern engines), there is a potential for improved engine efficiency by using fuels with high OS to allow for higher compression ratios. The experimental results of this work show that OS is negatively correlated with ITHR. Thus, high-sensitivity fuels can be designed by choosing components and additives that reduce the amount of ITHR.

Homogeneous Charge Compression Ignition (HCCI) combustion is an alternative combustion mode in which the fuel is homogeneously mixed with air and is auto-ignited by compression. Due to charge homogeneity, this mode is characterized by low equivalence ratios and temperatures giving simultaneously low nitric oxide (NOx) and soot in diesel engines. The conventional problem of NOx-soot trade-off is avoided in this mode due to absence of diffusion combustion. This mode can be employed at part load conditions while maintaining conventional combustion at high load thus minimizing regulatory cycle emissions and reducing cost of after-treatment systems. The present study focuses on achieving this mode in a turbocharged, common rail, direct injection, four-cylinder, heavy duty diesel engine. Specifically, the work involves a combination of three-dimensional CFD simulations and experiments on this engine to assess both traditional and novel strategies related to fuel injection. The first phase of the work involved a quasi-dimensional simulation of the engine to assess potential of achieving HCCI. This was done using a zero-dimensional, single-zone HCCI combustion model with n-heptane skeletal chemistry along with a one-dimensional model of intake and exhaust systems. The feasibility of operation with realistic knock values with high EGR rate of 60% was observed. The second aspect of the work involved three-dimensional CFD simulations of the in-cylinder process with wall film prediction to evaluate injection strategies associated with Early Direct Injection (EDI). The extended Coherent Flame Model-3Zone (ECFM-3Z) was employed for combustion simulation of conventional CI and EDI, and was validated with experimental in-cylinder pressure data from the engine. A new Uniformity Index (UI) parameter was defined to assess charge homogeneity. Results showed significant in-homogeneity and presence of wall film for EDI. Simulations were conducted to assess improvement of charge homogeneity by several strategies; narrow spray cone angle, injection timing, multiple injections, intake air heating, Port Fuel Injection (PFI) as well as combination of PFI and EDI. The maximum UI achieved by EDI was 0.78. The PFI strategy could achieve UI of 0.95; however, up to 50% of fuel remained trapped in the port after valve closure. This indicated that except EDI, none of the above-mentioned strategies could help achieve the benefits of the HCCI mode. The third part of the work involved engine experimentation to assess the EDI strategy. This strategy produced lower soot than that of conventional CI combustion with very short combustion duration, but led to high knock and NOx which is attributed to pool fire burning phenomenon of the wall film, as confirmed by CFD. An Optimized EDI (OptimEDI) strategy was then developed based on results of CFD and Design of Experiments. The Optim EDI consisted of triple injections with split ratio of 41%-45%-14% and advancing the first injection. This strategy gave 20% NOx and soot reduction over the conventional CI mode. Although this strategy gave encouraging results, there was a need for more substantial reduction in emissions without sacrificing efficiency. Hence, a novel concept of utilizing air-assisted Injection (AAI) into the EGR stream was employed, as this implied injecting very small droplets of fuel into the intake which would have sufficient residence time to evaporate before reaching the cylinder, thereby enabling HCCI. The fourth and final part of the work involved engine experimentation with AAI, and combination of OptimEDI with AAI. Results with 20% EGR showed that 5 to 10% of AAI gave further reduction in NOx but not in soot. With experiments involving 48% EGR rate, there was soot reduction of 75% due to combined AAI-EDI. NOx was negligible due to the high EGR rate. Thus, the significant contribution of this work is in proving that combining AAI with EDI as a novel injection strategy leads to substantial NOx and soot reduction.

[ES] El trabajo de investigación presentado en esta tesis es el resultado de varios años dedicados al desarrollo, la implementación y la optimización de dos tecnologías combinadas: un concepto de combustión innovador y una arquitectura de motor de nuevo diseño. Esta investigacion se ha realizado en el marco de una colaboración con Renault SA, como continuación de las actividades realizadas en el proyecto europeo POWERFUL (POWERtrain for FUture Light-duty vehicles) por un lado,y en el marco del proyecto europeo REWARD (Real World Advanced technologies foR Diesel engines), devenido como continuación del proyecto POWERFUL en el marco del programa de investigación Horizonte 2020, por otro lado. Los principales objetivos de estos estudios eran evaluar el potencial del concepto de combustión parcialmente premezclada (PPC) operando con gasolina como combustible en un innovador motor de 2 tiempos de válvulas en culata, y luego diseñar una nueva geometría de motor de 2 tiempos utilizando la arquitectura Uniflujo para superar los principales problemas y limitaciones observados durante la primera etapa, que se pueden resumir principalmente en el rendimiento de barrido (especialmente trabajando en cargas elevadas). La metodología diseñada para este trabajo de investigación sigue un enfoque teórico-experimental. La evaluación del concepto de combustión PPC operando con gasolina se llevó a cabo principalmente con un enfoque experimental con el apoyo del análisis en línea directamente en el banco de ensayo, seguido de un exhaustivo tratamiento posterior de los datos y de un análisis detallado del proceso de combustión utilizando herramientas de diagnóstico. Por el contrario, el desarrollo del nuevo motor Uniflujo de 2 tiempos consistió principalmente en iteraciones sobre modelado 3D-CFD, si bien las actividades experimentales fueron fundamentales para validar las diferentes soluciones propuestas y evaluar su sensibilidad ante diferentes parámetros de interés utilizando una metodología de Diseño de Experimentos (DoE). La primera parte del trabajo se ha dedicado a la comprensión de los procesos termodinámicos involucrados en la combustión operando con el concepto PPC en un motor de 2 tiempos de válvulas en culata utilizando gasolina como combustible, y a evaluar su potencial en términos de emisiones contaminantes, consumo de combustible y ruido. Por último, se ha realizado un trabajo de exploración para ampliar en la medida de lo posible el rango de funcionamiento de este concepto de combustión en esta configuración específica del motor, investigando especialmente el rendimiento en cargas bajas en todo el rango de regímenes de giro del motor, y estableciendo también las principales limitaciones para la operación en cargas altas. La segunda parte de la tesis se ha centrado en el desarrollo y optimización teórica de un motor Uniflujo de 2 tiempos de nuevo diseño, incluyendo su fabricación y validación experimental. El objetivo principal era optimizar, utilizando principalmente simulaciones 3D-CFD, el rendimiento de barrido de esta arquitectura de 2 tiempos mediante el diseño de nuevas geometrías de puertos de admisión, permitiendo un gran control sobre el flujo de aire hacia y a través del cilindro para barrer al máximo los gases quemados y minimizar el cortocircuito de aire fresco hacia el escape. Las soluciones óptimas se evaluaron experimentalmente siguiendo la metodología DoE, antes de comparar finalmente los resultados de rendimiento de barrido con la anterior arquitectura de motor de 2 tiempos con válvulas en culata. / [CA] El treball de recerca presentat en aquesta tesi és el resultat de diversos anys dedicats al desenvolupament, la implementació i l'optimització de dues tecnologies combinades: un concepte de combustió innovador i una arquitectura de motor de nou disseny. Aquesta recerca s'ha realitzat en el marc d'una col·laboració amb Renault SA, com a continuació de les activitats del projecte europeu *POWERFUL (*POWERtrain *for *FUture Light-*duty *vehicles) d'una banda, i en el marc del projecte europeu *REWARD (Real *World *Advanced *technologies *foR Dièsel *engines), es devingut com a continuació del projecte *POWERFUL en el marc del programa d'investigació Horitzó 2020, d'altra banda. Els principals objectius d'aquests estudis eren avaluar el potencial del concepte de combustió parcialment premesclada (PPC) operant amb gasolina com a combustible en un innovador motor de 2 temps de vàlvules en culata, i després dissenyar una nova geometria de motor de 2 temps utilitzant l'arquitectura Uniflux per a superar els principals problemes i limitacions observats durant la primera etapa, que es poden resumir principalment en el rendiment d'escombratge (especialment treballant en càrregues elevades). La metodologia dissenyada per a realitzar aquests treballs de recerca segueix un enfocament tant experimental com teòric. L'avaluació del concepte de combustió PPC operant amb gasolina es va dur a terme principalment amb un enfocament experimental, però sempre amb el suport de l'anàlisi en línia directament en el banc d'assaig, seguit d'un exhaustiu tractament posterior de les dades combinat amb una anàlisi detallada del procés de combustió utilitzant eines de diagnòstic. Per contra, el desenvolupament i el disseny del nou motor Uniflux de 2 temps va consistir principalment en iteracions sobre modelatge 3D-CFD, si bé les activitats experimentals van ser fonamentals per a validar les diferents solucions proposades i avaluar la seua sensibilitat davant una sèrie de paràmetres d'interés utilitzant una metodologia de Disseny d'Experiments (DoE). La primera part del treball s'ha dedicat a la comprensió dels processos termodinàmics involucrats en la combustió operant amb el concepte de combustió PPC en un motor de 2 temps de vàlvules en culata utilitzant gasolina com a combustible, i a avaluar el seu potencial en termes d'emissions contaminants, consum de combustible i també de soroll. Finalment, s'ha fet un treball d'exploració per a ampliar en la mesura que siga possible el rang de funcionament d'aquest concepte de combustió utilitzant eixa configuració específica del motor, investigant especialment el rendiment en càrregues baixes en tot el rang de règims de gir del motor, i establint també les principals limitacions per a l'operació en càrregues altes. La segona part de la tesi s'ha centrat en el desenvolupament i optimització teòrica d'un motor Uniflux de 2 temps de nou disseny, incloent la seua fabricació i validació experimental. L'objectiu principal era optimitzar, utilitzant principalment simulacions 3D-CFD, el rendiment d'escombratge d'aquesta arquitectura de 2 temps mitjançant el disseny de noves geometries de ports d'admissió, permetent un gran control sobre el flux d'aire cap a i a través del cilindre per a escombrar al màxim els gasos cremats i minimitzar el curtcircuit d'aire fresc cap a l'escapament. Les solucions òptimes es van fabricar i van avaluar experimentalment seguint la metodologia DoE, abans de comparar finalment els resultats de rendiment d'escombratge amb l'anterior arquitectura de motor de 2 temps amb vàlvules en culata. / [EN] The research work presented in this thesis is the result of several years dedicated to the development, implementation and optimization of two combined technologies: an innovative combustion concept and a newly designed engine architecture. These investigations have been performed in the framework of a research collaboration with Renault SA following up the activities performed along the European POWERFUL project (POWERtrain for FUture Light-duty vehicles) on the one hand, and in the framework of the European REWARD project (REal World Advanced technologies foR Diesel engines), brought as a continuation of the POWERFUL project in the frame of the Horizon 2020 research program, on the other hand. The main objectives of these studies were to evaluate the potential of the Partially Premixed Combustion (PPC) concept operating with gasoline fuel in an innovative 2-Stroke poppet-valve engine, and then to design a new 2-Stroke engine geometry using the Uniflow architecture to overcome the main problems and limitations observed during the first stage, which can be mainly summarized to the scavenging performance (especially at high loads). The methodology designed for performing these investigation is based on both experimental and theoretical approaches. The evaluation of the gasoline PPC concept was carried out mainly experimentally, but always supported by online analysis directly on the test-bench and followed by a thorough post-processing of the data combined with a detailed analysis of the combustion using combustion diagnostic tools. On the contrary, the development and design of the new 2-Stroke Uniflow engine consisted mainly of 3D-CFD iterations, but experimental testing was crucial to validate the different solutions proposed and evaluate their sensitivity to a set of parameters of interest using a Design of Experiments (DoE) methodology. The first part of the work has been dedicated to the understanding of the thermodynamical processes involved in the combustion in a poppet-valve 2-Stroke engine operating with the gasoline PPC concept, and to evaluate its potential in terms of pollutant emissions, fuel consumption and also noise. Finally, a wide exploration has been performed to extend as much as possible the operating range of this combustion concept using that specific engine configuration, especially investigating the low loads performance throughout the full range of engine speeds, and also laying out the main limitations for high-to-full load operations. The second part of the thesis has been focused on the development and theoretical optimization of a newly designed 2-Stroke Uniflow engine, leading to manufacture and experimental validation. The main objective was to optimize, using mainly 3D-CFD modeling simulations, the scavenging performance of this 2-Stroke architecture by designing new intake ports geometries and to enable a great control over the air flow into and through the cylinder in order to scavenge the burnt gases as much as possible while minimizing the fresh air short-circuit to the exhaust. The optimum solutions were then manufactured and experimentally tested following a DoE methodology, before finally comparing the results of the scavenging performance to the previous 2-Stroke poppet-valve engine architecture. / Thein, KJL. (2021). Evaluation of combustion concepts and scavenging configurations in a 2-Stroke compression-ignition engine for future automotive powerplants [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/164044 / TESIS