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[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 metodol, [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 u, [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 combus

[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 metodol, [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 u, [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 combus

Internal combustion engines have been the most used engine design when it comes to vehicle propulsion and transportation. But as the number of vehicles increase, new problems arise as well. Engine emissions such as carbon dioxide that has an effect on a global scale and other harmful emissions that affect on a local scale such as soot and nitrogen oxides are on the rise, forcing the countries to take measures on controlling and reducing them.Gasoline Partially Premixed Combustion (PPC) is an alternative combustion concept that can offer both high indicated efficiency and low exhaust emissions in terms of NOx and soot, compared to conventional diesel combustion (CDC). Previous research has shown that this concept can work well with gasoline fuels of different octane ratings and can be used both in light and heavy duty engines. Although PPC has been tested substantially in research engines, results from engine designs that are closer to production are limited.In this thesis, PPC is evaluated in a multi-cylinder light duty diesel engine. Results show that while it can perform well with both low octane RON75 and higher octane RON90 gasoline, the available load range is limited compared to similar diesel operation. Despite that, efficiency is high, with gross indicated numbers of around 48 %, while brake efficiency reaches up to 41 %. Soot emissions are improved compared to diesel while NOx emissions are in similar numbers. A reason for that is the limited use of EGR compared to previous studies. This was deemed necessary to improve the upper achievable load of the engine.As the use of EGR was a limiting factor, an evaluation of the two possible EGR routes was performed, to investigate the possible gains compared to single route operation. Results show that by combining routes possibility for a 4 % gain in efficiency could be found. Also, low load operation is limited due to the type of combustion and the fuel that is used. A minimum amount of temperature is necessary to

The global environment suffers from utilizing fossil fuels to powering internal combustion engines (ICE), due to the massive amounts of released CO2. Besides the global impact, the local environments experience high concentrations of harmful pollutants such as NOx, CO, soot and particulate matter (PM). The automotive industry is continuously striving to find new solutions to decrease fuel consumption and also to develop cleaner and more advanced combustion systems, i.e., low-temperature combustion (LTC) engines.The goal of this thesis is to employ computational fluid dynamics (CFD) simulations to investigate methanol under the partially premixed combustion (PPC) regime, which is one of the advanced LTC concepts alongside HCCI and RCCI. The benefit of PPC engines is the reduced average combustion temperature, which results in optimized emission rates of UHC/CO and NOx, maintaining high thermal efficiency. Interesting properties of methanol, such as a low stoichiometric air to fuel ratio and high latent heat of vaporization as well as non-sooting combustion, may enable further improvement of the PPC concept. Studies have been carried out by employing RANS and LES models to simulate mixing and ignition processes. It was found that methanol PPC can be achieved at relatively later injection timings (similar to those in diesel engines), in comparison to gasoline. Late injection timings can ease injection targeting into the piston bowl and utilize strong wall-spray interaction to help control the in-cylinder flow and therefore reduce the wall heat losses. The well-stirred-reactor (WSR) approach fails to predict pressure traces at highly stratified mixture compositions, such as $0.3 < \phi < 2.5$. Instead, the partially-stirred-reactor (PaSR) model, after model constant calibration, was employed to improve the prediction of combustion behavior. The ignition kernel of methanol starts in the fuel leanest mixtures, and continues as an ignition front propagation towards the fue

The concept of partially premixed combustion (PPC), applied to conventional diesel engines, has shown to yield high gross efficiencies and low emissions of oxides of nitrogen and soot. PPC emerged from the knowledge gained from homogeneous charge compression ignition (HCCI) research. To extend the load range and thus reduce cylinder pressure rise rates, the fuel is directly injected during the compression stroke, instead of in the intake port as is common with HCCI. In contrast to conventional diesel combustion, there is a separation between the fuel injection event and the start of combustion in PPC. Furthermore, the PPC concept relies on a high degree of dilution with exhaust gas recirculation (EGR) and air. This dilution and premixedness lead to a lower global temperature, which reduces NOx emissions and wall heat transfer which therefore results in a high thermodynamic efficiency. However, a high level of dilution reduces the exhaust temperature and thus leads to a lower gas exchange efficiency because the turbine needs to compensate by generating a higher exhaust back pressure. This thesis therefore focuses on expanding the system boundary of PPC, to facilitate a commercial application. This has been conducted in several studies which targeted the brake efficiency, instead of the gross. The work was conducted with a combination of engine modeling and simulations. Moreover, the in-cylinder combustion was taken from experimental measurements or predicted using a stochastic reactor model. The first part of the work investigated the influence of dilution on the gas exchange performance. The gas exchange efficiency was seen to decrease exponentially at high levels of dilution. In addition, a low inlet temperature led to an increase in both brake and gross efficiencies. Furthermore, an evaluation of turbocharger configurations revealed that, although a two-stage turbocharger only negligibly increased the brake efficiency, it enabled a substantially higher engine load

The main driver to investigate low temperature combustion concepts, such as partially premixed combustion (PPC), is the promise of low particulate matter (PM) and nitric oxide (NOx) emissions. A critical prerequisite for PPC is to temporally isolate the fuel injection and combustion events. In practice, exhaust gas recirculation (EGR) is applied in order to sufficiently extend the ignition delay to that effect. Hereby, in general, higher EGR rates are necessary for fuels with higher cetane numbers (CN). Against this background, the objective of this paper is to investigate the efficacy, with respect to PM-NOx emissions and engine efficiency, of gasoline as a potential gas-to-liquid (GTL) CN suppressant in various dosages. The performance of the resulting GTLine blend will be evaluated under PPC operating conditions in a heavy-duty direct-injected diesel engine. Setting aside for a moment any potential practical issues (e.g., flash point, vapor pressure) that fall outside the scope of this study, our data suggest that blending gasoline to otherwise high CN GTL appears to be a promising route to improve not only the efficiency, but also PM and NOx emissions, particularly when operating in PPC mode. Interestingly, this benefit is notwithstanding the high aromaticity of the gasoline compared to GTL. Given the ongoing dieselization trend and associated surplus of gasoline in many regions, notably Europe, along with the fact that the cost price of gasoline is significantly lower than that of GTL, the proposed GTLine approach promises to be a cost effective way to accommodate GTL in a world wherein low temperature combustion concepts, such as PPC, appear to be really taking off.

The main driver to investigate low temperature combustion concepts, such as partially premixed combustion (PPC), is the promise of low particulate matter (PM) and nitric oxide (NOx) emissions. A critical prerequisite for PPC is to temporally isolate the fuel injection and combustion events. In practice, exhaust gas recirculation (EGR) is applied in order to sufficiently extend the ignition delay to that effect. Hereby, in general, higher EGR rates are necessary for fuels with higher cetane numbers (CN). Against this background, the objective of this paper is to investigate the efficacy, with respect to PM-NOx emissions and engine efficiency, of gasoline as a potential gas-to-liquid (GTL) CN suppressant in various dosages. The performance of the resulting GTLine blend will be evaluated under PPC operating conditions in a heavy-duty direct-injected diesel engine. Setting aside for a moment any potential practical issues (e.g., flash point, vapor pressure) that fall outside the scope of this study, our data suggest that blending gasoline to otherwise high CN GTL appears to be a promising route to improve not only the efficiency, but also PM and NOx emissions, particularly when operating in PPC mode. Interestingly, this benefit is notwithstanding the high aromaticity of the gasoline compared to GTL. Given the ongoing dieselization trend and associated surplus of gasoline in many regions, notably Europe, along with the fact that the cost price of gasoline is significantly lower than that of GTL, the proposed GTLine approach promises to be a cost effective way to accommodate GTL in a world wherein low temperature combustion concepts, such as PPC, appear to be really taking off.

For many decades, research work on combustion has been focused on improving combustion efficiency and reducing harmful emissions. Laser diagnostics is one of the best ways to investigate the combustion process and emission formation as it is non-intrusive and it has high spatiotemporal resolution. In this thesis work, many laser diagnostics have been developed and employed for combustion research. The laser-based optical methods cover ballistic imaging (BI), multi-scaler laser introduced fluorescence (LIF) imaging, particle imaging velocimetry (PIV), laser Doppler anemometry (LDA), and high speed LIF measurement (up to 140 kHz). Two BI systems were developed and compared, together with ultrafast shadow imaging (USI) for better imaging through a high optical depth (OD) substance, e.g. a spray. In addition, multi-scaler planar laser introduced fluorescence (PLIF) measurements were developed in Lund University Piloted Jet (LUPJ) burners including simultaneous measurement of temperature, CH radicals and OH radicals distribution, and simultaneous measurement of CH2O radicals, CH radicals and OH radicals distribution. Key parameters, such as Damköhler number, Karlovitz number, and Kolmogorov time scale, were calculated and are listed in this thesis based on LDA measurements. Moreover, high speed PLIF measurements were developed in an LUPJ burner including simultaneous OH/CH2O PLIF at 50 kHz, OH PLIF at 100 kHz and CH2O PLIF at 140 kHz, with more than 100 consecutive images for the first ever time. That was achieved by using a burst-mode laser pumped optical parametric oscillator (OPO) system synchronised with high speed cameras and high speed intensifiers. The diagnostics approaches were capable of following the temporal evolution of the reacting flow down to the Kolmogorov scale for better understanding of the transient behaviour of the eddy/flame interaction in highly turbulent premixed flames.The developed laser diagnostics have also been applied in a diesel spray in a

The work presented in this thesis is motivated by the need to reliably operate a compression-ignition engine in a partially premixed combustion (PPC) mode. Partially premixed combustion is a low temperature combustion concept, where the ignition delay is prolonged to enhance fuel-air mixing in the combustion chamber before the start of combustion. A premixed combustion process, in combination with high levels of exhaust-gas recirculation (EGR), gives low combustion temperatures, which decrease NOx and soot formation. Lowered combustion temperatures also reduce heat-transfer losses which increase the thermodynamic engine efficiency. The ignition delay is, however, determined by chemical reactions rates, which are sensitive to temperature, gas-mixture composition, fuel properties and fuel-injection timing. This sensitivity makes PPC more challenging to operate compared to conventional diesel combustion. Challenges related to PPC include an increased sensitivity to operating conditions, decreased combustion-timing controllability, high pressure-rise rates, and low combustion efficiency at low engine loads. These challenges put high demands on the engine control system that needs to be able to adjust fuel-injection timings and durations to compensate for the combustion sensitivity. Therefore, this thesis investigates closed-loop combustion control for reliable PPC operation. The feedback loop from pressure-sensor measurement to fuel-injection actuation is studied in particular. A common theme for the controllers presented is the use of models in the controller design. Either to evaluate controller performance in simulation, or to optimize engine performance online. The principle of model predictive control is used for its ability to incorporate modeled system behavior in the controller design, and to control multi-variable systems with input and output constraints.The problem of tuning robust and noise insensitive combustion-timing controllers, and its dependence on fue