Academic literature on the topic 'Pre-chamber ignition'

Pre-chamber jet ignition is a promising way to improve fuel consumption of gasoline engine. A small volume passive pre-chamber was tested at a 1.5L turbocharged GDI engine. Combustion and emission characteristics of passive pre-chamber at low-speed WOT and part load were studied. Besides, the combustion stability of the passive pre-chamber at idle operation has also been studied. The results show that at 1500 r/min WOT, compared with the traditional spark ignition, the combustion phase of pre-chamber is advanced by 7.1°CA, the effective fuel consumption is reduced by 24 g/kW h, and the maximum pressure rise rate is increased by 0.09 MPa/°CA. The knock tendency can be relieved by pre-chamber ignition. At part load of 2000 r/min, pre-chamber ignition can enhance the combustion process and improve the combustion stability. The fuel consumption of pre-chamber ignition increases slightly at low load, but decreases significantly at high load. Compared with the traditional spark ignition, the NOx emissions of pre-chamber increase significantly, with a maximum increase of about 15%; the HC emissions decrease, and the highest decrease is about 36%. But there is no significant difference in CO emissions between pre-chamber ignition and spark plug ignition. The intake valve opening timing has a significant influence on the pre-chamber combustion stability at idle operation. With the delay of the pre-chamber intake valve opening timing, the CoV is reduced and can be kept within the CoV limit.

A ceramic heat-insulated natural gas engine has been developed which incorporates a pre-chamber and a throat valve to the main chamber. Low-pressure natural gas is supplied into the pre-chamber to form fuel-rich mixtures in the pre-chamber during the intake stroke while the throat valve is closed, while natural gas and exhaust gas recirculation (EGR) gas are charged in the intake port to form a homogeneous mixture in the main chamber. Experiments showed that spontaneous ignition took place near top dead centre (TDC) in the pre-chamber immediately after the throat valve was opened, followed by homogeneous charge compression ignition (HCCI) combustion in the main chamber, featuring very fast combustion and extremely low NOX emission. Effects of engine parameters including compression ratio, throat valve opening timing, the fuel fraction injected into the pre-chamber and the EGR ratio were investigated. It was found from the experiment that 85 per cent of the fuel supplied could be successfully burned in HCCI combustion in the main chamber being triggered by the spontaneous ignition in the pre-chamber, and the HCCI combustion could be controlled if the engine parameters mentioned above could be well optimized.

Turbulent jet ignition is a pre-chamber ignition system for an otherwise standard gasoline spark ignition engine. Turbulent jet ignition works by injecting chemical active turbulent jets to initiate combustion in a premixed fuel/air mixture. The main advantage of turbulent jet ignition is its ability to ignite and burn completely very lean fuel/air mixtures in the main chamber charge. This occurs with a very fast burn rate due to the widely distributed ignition sites that consume the main charge rapidly. Rapid combustion of lean mixtures leads to lower exhaust emissions due to more complete combustion at lower combustion temperature. The purpose of the paper is to study the combustion characteristics of gasoline, ethanol, and wet ethanol when operated with the pre-chamber combustion system and the ability of the pre-chamber ignition to extend the lean-burn limits of such fuels. The combustion and heat release process was analyzed and exhaust emissions measured. Results show that the effect of turbulent jet ignition system on the lean-burn limit and exhaust emissions varied with fuels. The lean limit was extended by using fueled pre-chamber furthest, to λ = 1.71 with gasoline, followed by λ = 1.77 with wet ethanol and λ = 1.9 with ethanol. NOx emissions were significantly reduced with increased lambda for each fuel under stable combustion conditions. For ethanol, at maximum lean limit lambda 1.9, the NOx emissions were almost negligible due to lower combustion temperature.

The working process of a lean burn natural gas spark ignition engine was simulated with a 3-D CFD software package AVL-FIRE. Such simulations were made to analyze and understand the flow field, fuel/air mixture distribution, ignition and flame propagation. The simulations provide basis for the optimization of the combustion system of the engine. Two injection strategies for the pre-chamber enrichment were established and compared. The results indicate that with enrichment injection in the pre-chamber, the fuel/air equivalence ratio is precisely controlled in the range of 1.0 to 1.1, stable ignition in the pre-chamber is ensured, and fast initial flame propagation in main combustion chamber is realized.

Abstract The paper presents the study of combustion process of a homogenous lean propane-air mixture in the cylindrical combustion chamber ignited by a hot gas jet from the pre-ignition chamber. A rich propane-air mixture in the pre-chamber is ignited by the spark plug and the exhaust gasses flow from the chamber trough the holes in the wall. The mathematical model of gas exchange and energy balance in chambers with a laminar finite-rate model taking into account the two-step Arrhenius chemical kinetics is presented. The work presents results of thermodynamic parameters of the charge obtained in CFD simulations in Fluent and Kiva3v for three configurations: with one hole in the wall of the ignition chamber, with three holes and without an ignition chamber. Modelling and simulation have shown faster burning of the mixture for jet ignition with three holes of the pre-chamber. The results of simulations were verified by experimental studies in the combustion chamber of the same geometry by the Schlieren method. The work presents flame front propagation, pressure traces and pressure increment speed for two mixtures with a different equivalence fuel-air ratio. Experimental results proved the simulation observation of faster flame propagation in the main chamber with three holes

This article presents a study of the mechanism that the lubricant oil droplet initiates low-speed pre-ignition in highly boosted downsized gasoline engines. Low-speed pre-ignition is a phenomenon that the fuel–air mixture ignites before the spark timing, leading to flame propagation that results in a heavy knock. The ignition of lubricant oil droplets is thought to be one possible mechanism for low-speed pre-ignition. However, the oil droplet ignition conditions are not yet well understood. First, the conditions under which a single oil droplet initiates the combustion of a fuel–air mixture were investigated using a rapid compression and expansion machine. When an initial droplet temperature was above 250 °C, the vaporized oil ignited before the gasoline–air mixture, in which case the combustion of the gasoline–air mixture around the droplet was initiated. The numerical results showed that the oil droplet temperature increases above 250 °C if the droplet is heated by burned gas remaining in the combustion chamber from the previous cycle. A direct-injection single-cylinder research engine was operated under the condition that no residual gas exists in the combustion chamber. In this case, no low-speed pre-ignition occurred even if gross indicated that mean effective pressure was 2.5 MPa. These results indicate that an oil droplet does not cause low-speed pre-ignition if any droplet flies into the combustion chamber unless it remains in the chamber over the exhaust stroke.

To investigate the ignition characteristics of an axial-flow injection burner for a Stirling engine, a combustion chamber was designed. Diesel was used as fuel and oxygen as oxidant. The experiments of ignition characteristics were carried out with an electric plug igniter. The ignition characteristics under different combustion chamber pressure, pre-oxygen supply time, oxygen supply flow and ignition position were studied. The experimental results show that, with the increase of the pressure, the ignition time of the burner increases gradually, and the ignition success rate decreases gradually. The oxygen flow rate is related to ignition time in a certain range, while the pre-oxygen supply time has little effect. With the ignition position moving downward, the ignition time decreases gradually.

Turbulent jet ignition technology can significantly improve lean combustion stability and suppress engine knocking. However, the narrow jet channel between the pre-chamber and the main chamber leads to some difficulties in heat exchange, which significantly affects combustion performance and mechanical component lifetime. To clarify the effect of temperature conditions on combustion evolutions of turbulent jet ignition, direct numerical simulations with detailed chemical kinetics were employed under engine-relevant conditions. The flame propagation in the pre-chamber and the early-stage turbulent jet ignition in the main chamber were investigated. The results show that depending on temperature conditions, two types of flame configuration can be identified in the main chamber, i.e., the normal turbulent jet flame propagation and the spherical flame propagation, and the latter is closely associated with pressure wave disturbance. Under low-temperature conditions, the cold jet stoichiometric mixtures and the vortexes induced by the jet flow determine the early-stage flame development in the main chamber. Under intermediate temperature conditions, pre-flame heat release and leading pressure waves are induced in the jet channel, which can be regarded as a transition of different combustion modes. Whereas under high-temperature conditions, irregular auto-ignition events start to occur, and spherical flame fronts are induced in the main chamber, behaving faster flame propagation.

Pre-chamber ignition systems are currently one of the most attractive developments for SI engines. The objective of this thesis is to present the technology at it's current state, focusing on passenger vehicles application, to analyse what issues need to be addressed for it to widely come to the market and what the potential of this techology is for the SI engine future. Replacing the spark plug with a new system capable of igniting a much leaner mixture, to reduce the likelyhood of knock, was the initial goal of the pre-chamber ignition system. What the system achieves is also a much faster combustion speed, which can deliver greater effciency, power, and reduce knock occurrence even with stoichiometric AFR. The implementation of the system presents signifcant challenges, which led many researchers to propose and patent a multitude of solutions which spawned from the original idea. Although for long time the diffculties with respect to a common spark plug ignition system have far outweighted the pros of the pre-chamber ignition, with time and the advancements in electronic controls, injectors and other systems, the research on this system gains a renewed interest.

[EN] In the current work, the characterization of the combustion process inside a stratified pre-chamber spark ignition (PCSI) system is performed. An extensive bibliographical review about the pre-chamber systems developed from the second half of the 20th century until modern times is presented. The review shows that the latest generation systems have the potential to accomplish the emissions limits while providing high performance and low fuel consumption. Nevertheless, many efforts of the scientific community are still needed to allow the large-scale application of the technology. Indeed, based on the outstanding challenges observed, the investigation plan is developed including both experimental and numerical parts. All experiments were performed by means of the rapid compressionexpansion machine (RCEM) in the CMT-Motores Térmicos laboratory. The original cylinder head layout was modified to allow the housing of the prechamber itself, fuel injectors, spark plug, pressure transducers in both chamber, and a thermocouple. The test methodology involved the acquisition of the pressure evolution in both main chamber and pre-chamber, the piston position (used to compute the instantaneous cylinder volume), the duration of the auxiliary injection, and the spark ignition point. These are used as input for the zero-dimensional thermodynamic model which simulates the fundamental parameters aims to characterize the PCSI system working cycle. Therefore, a deeper knowledge of the mass interchanged process, induced turbulence field, heat release rate, combustion speed, and flame regime is generated. Subsequently, to calibrate the zero-dimensional model coefficients under motoring conditions, several 3D CFD simulations were carried out by means of Converge software. Hence, the results of the simulations in terms of interchanged mass and pre-chamber turbulent kinetic energy have been used to calibrate the nozzle discharge coefficient and the turbulence sub-model coefficients for all the pre-chamber geometries. Furthermore, the 3D CFD simulations outputs are analysed to fully understand the flow field structure and the local effect induced by the different nozzles at the spark activation time. The turbulent kinetic energy in terms of intensity and orientation is investigated over several relevant pre-chamber sections. The results reveal a clear relationship between the turbulence developed within the pre-chamber and the orifices structure. Straight orifices or perpendicular jets impact, promote more intense local turbulence due to direct collision while tilted orifices guarantee more homogeneity due to the swirling motion. Additionally, increase the orifice numbers shows benefits on the fluid dynamic homogeneity. Thus, preceding the experimental campaign several fundamental aspects of the system are evaluated. The cycle-to-cycle dispersion is explored by means of the statistical assessment showing low pressure peak deviation. The auxiliary injection pressure and timing are optimized for avoiding wall wetting phenomena while ensuring proper air/fuel mixing. Finally, the spark activation point is chosen as a function of the theoretically maximum turbulent flame speed. Thereby, the experimental campaign is carried out according to tests matrix, in order to evaluate the effect of the equivalence ratio of both chambers, and how the orifices diameter, number, and distribution affect the combustion process. Moreover, chemiluminescence visualization tests, performed by means of the available optical access of the RCEM, are combined with zerodimensional and 3D CFD results to shed light on the work cycle. Conclusions suggest a slightly rich mixture inside the pre-chamber combined with the highest number of tilted orifices as the better configuration for improving combustion efficiency under lean and ultra-lean main chamber mixture conditions. Nevertheless, axial orifices should be considered for further investigations. Finally, the author proposes a series of developments considered interesting in both the experimental and numerical fields.<br>[ES] En el presente trabajo se realiza la caracterización del proceso de combustión dentro de un sistema de encendido por pre-cámara bajo carga estratificada. Por lo tanto, se presenta una extensa revisión bibliográfica sobre los sistemas de pre-cámara desarrollados desde la segunda mitad del siglo XX hasta los tiempos modernos. El resumen muestra que los sistemas de última generación tienen el potencial de cumplir con los límites de las emisiones, al tiempo que proporcionan un alto rendimiento y un bajo consumo de combustible. No obstante, todavía se necesitan muchos esfuerzos de la comunidad científica para permitir la difusión a gran escala de la tecnología. De hecho, sobre la base de los desafíos abiertos observados, se desarrolla el plan de investigación incluyendo tanto una parte experimental como numérica. Todos los experimentos se realizan mediante la máquina de compresión-expansión rápida (RCEM) de que dispone el laboratorio CMT-Motores Térmicos . La disposición original de la culata se modificó para permitir el alojamiento de la propia pre-cámara, los inyectores , la bujía, los sensores de presión y un termopar. La metodología de ensayo implica la adquisición de la evolución de la presión tanto en cámara principal como en pre-cámara, el volumen del cilindro, la duración de la inyección auxiliar y el punto de ignición de la bujía. Estos se utilizan como parámetros de entrada para el modelo termodinámico cero-dimensional que devuelve los parámetros fundamentales que caracterizan ciclo de trabajo del sistema PCSI. Por lo tanto, se genera un conocimiento más profundo del proceso de intercambio de masas, del campo de turbulencias inducidas, de la tasa de liberación de calor, de la velocidad de combustión y del régimen de la llama. Posteriormente, para calibrar los coeficientes del modelo cero-dimensional bajo condiciones de arrastre, se llevaron a cabo varias simulaciones CFD en 3D mediante el software Converge. Por lo tanto, los resultados de las simulaciones en términos de masa intercambiada y energía cinética turbulenta de la precámara se han utilizado para calibrar el coeficiente de descarga de la tobera y los coeficientes del sub-modelo de turbulencia para todas las geometrías de la pre-cámara. Además, se analizan los resultados de las simulaciones CFD para comprender plenamente la estructura del campo de flujo y el efecto local inducido por las diferentes geometriás en el tiempo de activación de la chispa. La energía cinética turbulenta en términos de intensidad y orientación se investiga en varias secciones relevantes de la pre-cámara. Los resultados revelan una clara relación entre la turbulencia desarrollada dentro de la pre-cámara y la estructura de los orificios. Los orificios rectos o los chorros perpendiculares, promueven una turbulencia local más intensa debido a la colisión directa mientras que los orificios inclinados del campo fluido y del dosado. Precedentemente al desarrollo de la campaña experimental se evalúan varios aspectos fundamentales del sistema. La dispersión ciclo a ciclo se explora por medio de la evaluación estadística que muestra una baja desviación de los picos de presión. La presión y el punto de inyección auxiliar se optimizan para evitar los fenómenos de mojado de las paredes, asegurando al mismo tiempo una mezcla adecuada de aire/combustible. Finalmente, el punto de activación de la chispa se elige en función de la velocidad máxima teórica de la llama turbulenta. De este modo, la campaña experimental se lleva a cabo de acuerdo con la matriz de pruebas, con el fin de evaluar el efecto del dosado equivalente de ambas cámaras, y cómo el diámetro, el número y la distribución de los orificios afectan al proceso de combustión. Además, las pruebas de visualización de quimioluminiscencia, realizadas mediante el acceso óptico disponible de la RCEM, se combinan con resultados de CFD y resultados del modelo cerodimen para arrojar luz sobre el ciclo de trabajo. Las conclusiones sugieren que una mezcla ligeramente rica dentro de la pre-cámaracombinadaconelmayornúmerodeorificiosdesfasadoseslamejor configuración para garantizar un elevada eficiencia de la combustión en condiciones de mezcla pobre y ultra-pobre de la cámara principal. No obstante, los orificios axiales deben ser considerados para investigaciones futuras. Por último, el autor propone una serie de desarrollos considerados interesantes tanto en el campo experimental como en el numérico.<br>[CA] En el present treball es realitza la caracterització del procés de combustió dins d'un sistema d'encesa de pre-cambra soto càrrega estratifi-cada. Per tant, es presenta una extensa revisió bibliogràfica sobre els sistemes de precambra desenvolupats des de la segona meitat del segle XX fins als temps moderns. El resum mostra que els sistemes d'última generació tenen el potencial de complir amb els límits de les emissions, al mateix temps que proporcionen un alt rendiment i un baix consum de combustible. No obstant això, encara es necessiten molts esforços de la comunitat científica per a permetre la difusió a gran escala de la tecnologia. De fet, sobre la base dels desafiaments oberts observats, es desenvolupa el pla d'investigació incloent tant una part experimental com numèrica. Tots els experiments es realitzen mitjançant la màquina de compressió-expansió ràpida (RCEM) de què disposa el laboratori CMT-Motors Tèrmics. La disposició original de la culata es va modificar per a permetre l'allotjament de la pròpia pre-cambra, els injectors , la bugia, els sensors de pressió i un termoparell. La metodologia d'assaig implica l'adquisició de l'evolució de la pressió tant en cambra principal com en pre-cambra, el volum del cilindre, la duració de la injecció auxiliar i el punt d'ignició de l'espurna. Aquests s'utilitzen com a paràmetres d'entrada per al model termodinàic zero-dimensional que retorna els paràmetres fonamen-tals que caracteritzen cicle de treball del sistema PCSI. Per tant, es genera un coneixement més profund del procés d'intercanvi de masses, del camp de turbulències induïdes, de la taxa d'alliberament de calor, de la velocitat de combustió i del règim de la flama. Posteriorment, per a calibrar els coefi-cients del model zerodimensional sota condicions d'arrossegament, es van dur a terme diverses simulacions CFD en 3D mitjançant el programari Converge. Per tant, els resultats de les simulacions en termes de massa intercanviada i energia cinètica turbulenta de la pre-cambra s'han utilitzat per a calibrar el coeficient de descàrrega de la tovera i els coeficients del sub-model de turbulència per a totes les geometries de la pre-cambra. A més, s'analitzen els resultats de les simulacions CFD per a comprendre plenament l'estructura del camp de flux i l'efecte local induït per les diferents geometries en el temps d'activació de l'espurna. L'energia cinètica turbulenta en termes d'intensitat i orientació s'investiga en diverses seccions rellevants de la pre-cambra. Els resultats revelen una clara relació entre la turbulència desenvolupada dins de la pre-cambra i l'estructura dels orificis. Els orificis rectes o els dolls perpendiculars, promouen una turbulència local més intensa a causa de la col·lisió directa mentre que els orificis inclinats garanteixen una major homogeneïtat a causa de la generació d'un macro-remolì. A més, l'augment del nombre d'orificis mostra beneficis en l'homogeneïtat fluid-dinàmica. Llavors, abans de la campanya experimental s'avaluen diversos aspectes fonamentals del sistema. La dispersió cicle a cicle s'explora per mitjà de l'avaluació estadística que mostra una baixa desviació dels pics de pressió. La pressió i el punt d'injecció auxiliar s'optimitzen per a evitar els fenòmens de mullat de les parets, assegurant al mateix temps una mescla adequada d'aire/combustible. Finalment, el punt d'activació de l'espurna es tria en funció de la velocitat màxima teòrica de la flama turbulenta. D'aquesta manera, la campanya experimental es duu a terme d'acord amb la matriu de proves, amb la finalitat d'avaluar l'efecte del dosatge equivalent de totes dues cambres, i com el diàmetre, el numero i la distribució dels orificis afecten el procés de combustió. A més, les proves de visualització de quimioluminescència, realitzades mitjançant l’accés òptic disponible de la RCEM, es combinen amb resultats de CFD i resultats del model zero-dimensional per a llançar llum sobre el cicle de treball. Les conclusions suggereixen que una mescla lleugerament rica dins de la pre-cambra combinada amb el major nombre d’orificis desfasats és la millor configuració per a garantir un elevada eficiència de la combustió en condicions de mescla pobra i ultra-pobre de la cambra principal. No obstant això, els orificis axials han de ser considerats per a investigacions futures. Finalment, l’autor proposa una sèrie de desenvolupaments considerats interessants tant en el camp experimental com en el numèric.<br>Pagano, V. (2020). Analysis of a stratified pre-chamber spark ignition system under lean mixture conditions [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/152486<br>TESIS

Дисертація на здобуття наукового ступеня кандидата технічних наук за спеціальністю 05.05.03 – двигуни та енергетичні установки. – Національний технічний університет "Харківський політехнічний інститут". – Харків, 2016. Дисертаційна робота присвячена дослідженню особливостей використання низькокалорійних газових палив в двигунах з форкамерно-факельним запалюванням паливо-повітряної суміші та якісним регулюванням потужності, моделюванню внутрішньоциліндрових процесів двигуна та пошуку його раціональних параметрів. Розроблений, реалізований і набув практичного застосування комплекс математичних моделей, що описують внутрішньоциліндрові процеси двигуна з форкамерно-факельним запалюванням. Проведені розрахункові дослідження дозволили визначити вплив властивостей НГП на показники газового двигуна типу ГД100. Запропоновано методику визначення оптимальних параметрів форкамери на основі комплексу критеріїв ефективності – мінімальної енергії запалювання суміші, енергії форкамерного факелу і коефіцієнта продувки форкамери. В результаті виконаного оптимізаційного дослідження запропоновані раціональні параметри форкамери за яких забезпечується якісне запалювання та згоряння паливо-повітряної суміші в циліндрі. Проаналізовано можливості конструктивного забезпечення номінальної потужності двигуна при використанні в якості палива різних низькока-лорійних газів. Отримані конструктивні та регулювальні параметри двигуна ГД100, що дозволять забезпечити високі техніко-економічні показники при його роботі на НГП.<br>The thesis on competition of a scientific degree of candidate of technical sciences in specialty 05.05.03 – engines and power plants. National Technical University "Kharkiv Polytechnic Institute", Kharkiv, 2016. The thesis is devoted to the investigation of the use of low-calorie gas fuels (LCG) in engines with pre-chamber ignition of fuel-air mixture and quality regulation power, cylinder engine processes internally modelling and search his rational parameters. Designed program has been implemented and received practical application of complex mathematical models that describe the internal cylinder engine processes with precham-ber ignition. Carried out calculations have allowed to determine the effect of the properties of the LCG on the performance of gas engine GD100 type. The technique of deter-mination of optimal parameters of the latter on the basis of a set of performance criteria: minimum ignition energy mix, energy pre-chamber torch and purge coefficient pre-chamber. As a result of the optimization performed studies offered rational parameters of the pre-chamber where quality is provided by ignition and combustion of fuel-air mixture in the cylinder. Analyzed the possibility of constructive ensure the rated power of the engine when used as a fuel by various low-calorie gases. Received constructive and adjusting parameters of engine GD100 to ensure high technical-economic indicators in the LCG.

Дисертація на здобуття наукового ступеня кандидата технічних наук за спеціальністю 05.05.03 – двигуни та енергетичні установки. – Національний технічний університет "Харківський політехнічний інститут". – Харків, 2016. Дисертаційна робота присвячена дослідженню особливостей використання низькокалорійних газових палив в двигунах з форкамерно-факельним запалюванням паливо-повітряної суміші та якісним регулюванням потужності, моделюванню внутрішньоциліндрових процесів двигуна та пошуку його раціональних параметрів. Розроблений, реалізований і набув практичного застосування комплекс математичних моделей, що описують внутрішньоциліндрові процеси двигуна з форкамерно-факельним запалюванням. Проведені розрахункові дослідження дозволили визначити вплив властивостей НГП на показники газового двигуна типу ГД100. Запропоновано методику визначення оптимальних параметрів форкамери на основі комплексу критеріїв ефективності – мінімальної енергії запалювання суміші, енергії форкамерного факелу і коефіцієнта продувки форкамери. В результаті виконаного оптимізаційного дослідження запропоновані раціональні параметри форкамери за яких забезпечується якісне запалювання та згоряння паливо-повітряної суміші в циліндрі. Проаналізовано можливості конструктивного забезпечення номінальної потужності двигуна при використанні в якості палива різних низькока-лорійних газів. Отримані конструктивні та регулювальні параметри двигуна ГД100, що дозволять забезпечити високі техніко-економічні показники при його роботі на НГП.<br>The thesis on competition of a scientific degree of candidate of technical sciences in specialty 05.05.03 – engines and power plants. National Technical University "Kharkiv Polytechnic Institute", Kharkiv, 2016. The thesis is devoted to the investigation of the use of low-calorie gas fuels (LCG) in engines with pre-chamber ignition of fuel-air mixture and quality regulation power, cylinder engine processes internally modelling and search his rational parameters. Designed program has been implemented and received practical application of complex mathematical models that describe the internal cylinder engine processes with precham-ber ignition. Carried out calculations have allowed to determine the effect of the properties of the LCG on the performance of gas engine GD100 type. The technique of deter-mination of optimal parameters of the latter on the basis of a set of performance criteria: minimum ignition energy mix, energy pre-chamber torch and purge coefficient pre-chamber. As a result of the optimization performed studies offered rational parameters of the pre-chamber where quality is provided by ignition and combustion of fuel-air mixture in the cylinder. Analyzed the possibility of constructive ensure the rated power of the engine when used as a fuel by various low-calorie gases. Received constructive and adjusting parameters of engine GD100 to ensure high technical-economic indicators in the LCG.

The aim of pollutant emissions legislation is to bring environmental benefit by helping reduce, for what road transport is responsible, the concentration of pollutants where levels are too high and endanger human health. Europe is considering several changes in “post Euro 6d” regulation from 2025. Several measures have been proposed for Euro 7, most of which introduce new challenges in the development of high-performance turbocharged gasoline engine such as the extension of lambda 1 in the whole engine map. In this Master Thesis, possible technologies to expand the engine operating range with lambda 1 in the entire engine map, without widely reducing the engine performances are analyzed. In particular the focus is on the Pre-Chamber Spark Ignition (PCSI), the Exhaust Gas Recirculation (EGR), the Miller Cylce, the Water Injection and the Ultra High Pressure Injection. Subsequently, the modeling and validation in Simulink/Matlab of thermal models to analyze and monitor the exhaust gas temperature in the entire exhaust system is presented and explained. The aim of the modeling is integrating the modules into the Model-in-the-Loop environment and co-simulating with GT-Power/Simulink for a virtual pre-calibration of exhaust gas temperature control. Finally, homologation cycles are run to obtain a first analysis feedback regarding the pre-calibration and to understand which are the cycle zones where the fuel enrichement will be necessary to reach the desired temperature.

<div>Pressure-gain combustion in wave rotors offer the opportunity for substantial improvement in gas turbine efficiency and power, while controlling emissions with fuel flexibility, if provided rapid and reliable ignition of lean mixtures. In addition, tightening emission regulations and increasing availability of gas fuels for internal-combustion engines require more reliable ignition for ultra-lean operation to avoid high peak combustion temperature. Turbulent jet ignition (TJI) is able to address the ignition challenges of lean premixed combustion. Especially, the turbulent hot jet results in faster ignition penetration for wave rotor pressure-gain combustors that have high-frequency operation and fast-burn requirements. Controllability of TJI needs better understanding of the chemistry and fluid mechanics in the jet mixing region, particularly the estimation of ignition delay time and identifying the location of the ignition onset. </div><div>In the present work, numerical and analytical methods are employed to develop models capable of estimating the ignition characteristics that the turbulent hot jet exhibits as it is issued to a cold stoichiometric CH4-H2-Air mixture with varied fuel reactivity blends. Numerical models of the starting turbulent jet are developed by Reynolds-averaged and large-eddy simulation of Navier-Stokes and scalar transport equations in a high-resolution computational domain, with major focus on ignition of high-reactivity fuel blends in the jet near-field due to computational resource limitations. The chemical reactions are modeled using detailed chemistry by well-stirred and partially stirred reactor approaches. Numerical models describe the temporal evolution of jet mixture fraction, scalar dissipation rate, flow strain rate, and thermochemical quantities of the flow.</div><div>For faster estimation of ignition characteristics, analytical methods are developed to explicitly solve governing equations for the transient evolution of the near field and the leading vortex of the starting hot jet. First, the transient radial evolution of the turbulent shear-layer of a round transient jet is analytically investigated in the near-field of the nozzle, where the momentum potential core exists. The methods approximate the mixing and chemical processes in the jet shear and mixing layer. The momentum equation is integrated analytically, with a mixing-length turbulence model to represent the variation of effective viscosity due to the velocity gradients. The analytic predictions of the velocity field and mass entrainment rate of the jet are compared with numerical predictions and experimental findings. In addition, the transport equation of conserved scalars in the jet near-field is solved analytically for the history of the jet mixture fraction. This analytic solution for temperature and species is used, together with available models for instantaneous chemical induction time, to create an analytic ignition model that provides the time and radial location of the ignition onset.</div><div>Lastly, the ignition mechanism within the vortex ring, which leads the starting turbulent jet, is modeled using prior understanding about the mixing characteristics of the vortex. This mechanism is more relevant to low-reactivity fuel blends. Due to the presence of strong mixing at the large-scale, the vortex ring is treated as a homogeneous batch-reactor, which contains certain levels of the jet mixture fraction. This assumption provides the initial composition and temperature of the reactor in which ignition ensues. </div><div>This article-dissertation is developed as a collection of 4 articles published in peer-reviewed journals, one submitted article, and additional unpublished work. The study is laid out in 6 chapters with the following contributions:</div><div>Chapter 1: This chapter numerically investigates the three-dimensional behavior of a transient hot jet as modeled using the Reynolds-averaged turbulence flow. The study aims at providing an insight towards the role of mixing in the ignition progress and how the operating conditions such as fuel mixture and pre-chamber pressure ratio can influence the ignition success. An ignition prediction criterion is developed in this chapter, which helps to predict the ignition success under a broad range of operating conditions.</div><div>Chapter 2: In this chapter, the large-eddy simulation (LES) of hot jet ignition is reported in conjunction with detailed kinetics mechanism and adaptive-mesh refinement. The correlation between local values of mixture fraction gradient and ignition is discussed. Furthermore, the role of methane-hydrogen ratio on the heat release pattern is studied for two specific mixtures.</div><div>Chapter 3: The LES of CH4-H2-Air ignition is extended in this chapter to account for multivariable evaluation of ignition. Joint probability assessment of ignition explains the role of important scalars on the formation and growth of ignition. Also, the effect of CH4-H2 ratio on the spatial distribution of ignition is assessed and discussed.</div><div>Chapter 4: In this chapter, the rate of mass entrainment into the jet in the near-field region is studied. Characterization of the mass entrainment illuminates the understanding of mixing behavior of the starting turbulent jets. Through an exact solution of the momentum equation, this chapter includes a model of the diffusive transport in a round transient jet at high Reynolds numbers.</div><div>Chapter 5: This chapter proposes a method to evaluate the mass/heat exchange between a transient-turbulent jet and a quiescent environment. To analyze the transport phenomena in the jet near-field, the transient diffusion equation in cylindrical coordinates is explicitly solved and its solution is compared with the empirical findings. The transport solution then enables an ignition model to describe the spatiotemporal characteristics of ignition in the near-field.</div><div>Chapter 6: The development of ignition within the vortex ring of the transient jet is investigated in this chapter. The initiation, growth, and departure of the vortex ring are studied using the available empirical correlations and the LES. Using a perfectly-stirred, zero-dimensional representation of the vortex, chemical kinetic calculations provide estimates of ignition delay for various fuel mixtures.</div><div><br></div>

Abstract Knock is a major challenge for high load operation of spark ignited gasoline engines with higher compression ratios, since the end-gas undergoes higher temperature and pressure trajectories during combustion. Pre-chamber combustion creates long-reach ignition jets that have the potential to mitigate knock due to their rapid consumption of end-gas. However, conventional pressure oscillation-based knock metrics may not accurately capture the end-gas autoignition severity in pre-chamber systems due to differences in ignition and combustion behavior. This work investigates the knock behavior of both traditional spark ignition and pre-chamber combustion (including different nozzle designs) in a high compression ratio engine fueled with regular octane certification gasoline. The data was analyzed using statistical methods to show the random nature of knock events. Detailed analysis was used to explain the pressure oscillations of both knocking and non-knocking cycles of pre-chamber jet combustion and show that conventional pressure oscillation-based knock metrics may not adequately quantify end-gas autoignition severity. A novel knock metric is introduced to avoid consideration of the non-knock related pressure oscillation and better quantify the end-gas autoignition severity. The new metric was used to explain the knock mitigation mechanism for pre-chamber jet combustion and demonstrate an additional pre-chamber jet ignition benefit of reduced combustion variability during engine operation with cooled exhaust gas circulation within its dilution limit.