This thesis describes an experimental investigation into ignition systems, their effects on the combustion process, and how the discharge is affected by the prevailing pressure, temperature and flow. The work is divided into four main areas, a comprehensive literature review, engine testing for ignition system suitability, non-flow rig testing (including erosion) and flow rig testing. The literature review concluded that the most practical ignition system for lean burn gas engines will continue to be based on the spark plug, but in the medium to long term, laser ignition may become viable. The measurement of the HT voltage and current is not straightforward, and appropriate methods have been identified. Capacitive and inductive ignition system types were compared in lean and diluted conditions on a single cylinder research engine of modern design at different engine loads and speeds. It was found that the most beneficial ignition system was an inductive ignition system, although that for some conditions, capacitive systems induced better engine performance with a fraction of the stored energy of the inductive alternative. Non flow tests showed that the early part of the spark discharge is sensitive to pressure and temperature effects, and as a consequence, the latter stages of the discharge are also affected. A correlation has been developed, for use with conventional nickel electrode spark plugs, to predict breakdown voltage as a function of pressure, temperature and gap. Experiments were carried out at elevated pressures in a stream of flowing air with capacitive and inductive ignition systems. Different electrode designs and orientations were also compared. It was shown that when exposed to a flow field, the discharge can be stretched which results in a shortened spark duration; in some cases the electrode can shield the discharge from flow field effects. This work showed that flow through the spark gap is a hindrance to the spark process, especially for longer duration systems. However for flame kernel growth, the literature review identified that flow is beneficial, serving to convect the kernel away from the electrodes, reducing the heat transfer from the flame. Analysis of the glow voltage history in the pressurised flow rig has been used to develop a correlation relating the voltage, current, flow velocity, pressure and time. This correlation was used to analyse the velocity records from the spark plug in a firing engine. The predicted velocities and turbulence intensity were in agreement with independent measurements.

Depuis plusieurs années déjà, nombre d’applications industrielles impliquant des nanomatériaux ont vu le jour mais les connaissances relatives aux dangers de ces nouveaux matériaux sont actuellement assez restreintes. Le développement de ces nouveaux produits ne pouvant se poursuivre sans une évaluation approfondie des risques pour l’environnement et au poste de travail, les dangers relatifs aux nanoparticules doivent être évalués. La toxicité potentielle de ces nouveaux matériaux est souvent mise en avant. Néanmoins, les risques d’incendie et d’explosion ne doivent pas être négligés. Centrées essentiellement sur les poudres de taille micrométrique, les données de la littérature ne permettent pas, en effet, à l’heure actuelle, d’évaluer la probabilité et la gravité d’une explosion de nanopoudres. Dans ce contexte, la sensibilité à l’inflammation et la sévérité d’explosion de nanomatériaux pulvérulents typiques ont été évaluées ainsi que la validité des appareillages et procédures standards, habituellement utilisés lors d’une telle démarche. Enfin, la méthodologie adoptée afin d’évaluer les risques d’inflammation et d’explosion d’une installation de production de nanopoudres et de sécuriser au mieux la santé des travailleurs exposés aux nanoparticules est illustrée aux travers de deux exemples. Cette démarche pourra servir de base à de futures analyses de risques concernant les produits nanostructurés, exercice qui va devenir indispensable et de plus en plus fréquent au vu du contexte économique et réglementaire / In the industrial and research fields, nanomaterials provides a growing interest and many industrial applications have already been developed in the last years. However, knowledge about the hazards related to these new materials is currently limited. As safe nanomaterial production cannot be permitted without a deeper evaluation of environmental and occupational hazards, hazards related to nanoparticles have to be evaluated. One often thinks about the potential toxicity of nanoparticles. However, dust fire and explosion should not be neglected when the dusts are combustible, which may often be the case. So far, literature studies concerning the evaluation of explosion and flammability risks of powders were essentially carried out on micron-sized materials and do not enable in fact to evaluate fire and explosion risk probabilities and gravities of nanopowders. The main goal of this work is to study explosion and ignition risks related to nanopowders. In particular, the evaluation of the explosion sensitivity and severity of typical nanomaterials has been studied as well as the validity of the existing analytical and methodological tools designed to evaluate dust ignition and explosion hazards. This work also deals with the methodology applied to a plant and to a laboratory in order to define the best safety barriers which were positioned to ensure the best occupational safety level to all workers and evaluate in a good way the ignition and explosion risks related to the use and production of fluffy nanomaterials. This work will certainly help risk engineers concerned about the handling and the production of combustible nanopowders.

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.

Student Number : 9707408V - MSc(Eng) research report - School of Mechanical, Industrial and Aeronautical Engineering - Faculty of Engineering and the Built Environment / This research is an investigation into the performance and combustion characteristics of a two-cylinder, four-stroke compression ignition engine fuelled on diesel and then on dimethyl ether (DME). Baseline tests were performed using diesel. The tests were then repeated for dimethyl ether fuelling. All DME tests were performed at an injection opening pressure of 210 bar, as recommended for diesel fuelling. The tests were all carried out at constant torque with incremental increases in speed and an improved method of measuring the DME flow rate was devised. It was found that the engine’s performance characteristics were very similar, regardless of whether the engine was fuelled on diesel or DME. Brake power, indicated power and cylinder pressure, during the highest loading condition of 55 Nm, were virtually identical for diesel and DME fuelling, with the most significant finding being that the engine was more efficient when fuelled on DME than when fuelled with diesel. Another interesting finding was that the energy release of diesel decreases with increasing load, whilst the energy release of DME increases with increasing load. At the highest loading condition of 55 Nm, the energy release of DME was approximately 210 joules higher than that of diesel. This investigation concluded that DME may definitely be a suitable substitute fuel for diesel.

Determinação do desempenho de um motor à combustão interna com ignição por centelha, sem modificação em sua taxa de compressão volumétrica, usando álcool etílico vaporizado como combustível. Para facilidade de obtenção de dados usou-se um sistema de aquecimento elétrico para a geração do vapor do álcool etílico. Mediu-se as descargas de ar e combustível, a potência no eixo e a temperatura dos gases de escape para vários ângulos de avanço de centelha e rotações do eixo do motor. Os resultados obtidos foram comparados com o desempenho do mesmo motor funcionando com gasolina e álcool, pelo sistema de mistura usando carburador. O processo de vaporização pode ser aplicado a motores do tipo ciclo Otto , que poderão funcionar com álcool etílico ou gasolina, com poucas alterações em seu desempenho. / Performance determination of a spark-ignition combustion-engine, without modification in compression ratio, fueled with etanol vapours. The data acquisition was simplified by the use of an electric heater to generate the etanol vapours. The data acquired are flow of air and fuel, net power and escape gases temperature to various spark advance angles and engine speed. The performance was compared with those obtained with the carburator system motor, gasoline and etanol as fuel. The vaporization process will be applied in Otto cycle engines that may work with etanol or gasoline as fuels, with few performance alterations.

<p>Conventional rocket propellants such as monomethyl hydrazine (MMH) and hydrazine have been used for decades due to their high specific impulse and performance. However, interest in greener alternatives, including HAN or HAN-based propellants, has grown due to high levels of toxicity and difficulties in the handling and storage of conventional fuels. Included among potential propellants are monopropellants nitromethane (NM) and isopropyl nitrate (IPN) and their blends. Though large-scale investigations on the ignition and combustion of these fuels have been done, the ignition and combustion processes of these monopropellant fuels are still not well understood. Droplet studies have been traditionally and extensively employed to decipher the influence of ambient conditions and fuel properties on ignition and combustion of different fuels. These fundamental studies allow for the isolation of different factors such as ambient temperature and initial droplet size among others, to provide a deeper understanding of their effects in overall spray combustion.</p> <p> </p> <p>The research described here seeks to add to the knowledge on the ignition and combustion processes of NM and IPN through single droplet ignition and combustion studies. To this end, the first effort has been to establish a suitable method of studying the ignition and combustion of droplets in conditions similar to those in practical systems. Droplet ignition delay measurements for NM and IPN droplets have also been conducted, and the influence of ambient temperature and droplet size has been studied. The double flame structures of NM and IPN, representative of hybrid combustion, have also been observed. In addition, the applicability of the hybrid combustion model, developed to predict mass burning rates for hypergolic fuels exhibiting hybrid burning including MMH, UDMH and hydrazine, has been assessed. Lastly, the ability of the quasi-steady droplet ignition model to predict ignition delays of IPN and NM monopropellant droplets is also discussed.</p>

Aluminum based reactive nanomaterials have extensive applications in many fields including solid propellants, pyrotechnics, and catalytic reactions. One recent example is the novel concept of using nanostructured energetic particles for energy storage where the controlled exothermic reaction is the key to control the energy release process. It is of primary interest to understand the thermodynamics, kinetics, morphological and structural properties of these particles during the exothermic reaction. While the physiochemical properties of the monometallic powders are determined only by their size, the properties of bimetallic nanoalloys can be also engineered by their constituent compositions. This thesis conducts a systematic experimental investigation of the oxidation, ignition, and combustion of nano aluminum particles (nAl) and nanoalloys such as nanoscale aluminium-copper (n-AlCu) and aluminium-zinc (n-AlZn). The oxidation experiments are conducted by a TGA/DSC system with detailed characterisation of particles before and after the experiments by scanning electron microscopy (SEM), transmission electron microscopy (TEM), the Nanosizer, Brunauer–Emmett–Teller (BET), energy dispersive X-ray spectroscopy (EDS) and powder X-ray diffractionmetry (XRD). In the TGA/DSC analysis, nanomaterials are oxidized either at constant temperature or under different heating rates in the controlled atmosphere of air or nitrogen. A unique early ignition reaction is observed at the high heating rates for nAl and n-AlCu, which is associated with the effect of polymorphic phase transformation of the alumina shell and the early melting of the aluminum core. Different to the conventional shrink-core concept, hollow structures, i.e. nanoholes, in the central regions of nAl are observed and a phenomenal model is proposed. The comparison of the thermal-chemical characteristics of different nanomaterials reveals some unique 5 features related to nano-alloys such as increased reactivity. A preliminary combustion experiment on feeding nanoparticles in a methane stream is performed with a Bunsen burner setup, where the burning characteristics of different nanoparticles are analysed.

An accumulated combustible dust layer on some hot process equipment such as dryers or hot bearings can be ignited and result in fires when the hot surface temperature is sufficiently high. The ASTM E 2021 test procedure is often used to determine the Hot Surface Minimum Ignition Temperature for a half inch deep layer of a particular dust material. This test procedure was used in this thesis to study possible effects of combustible liquid (such as lubricating oil) and powder additives in the dust layer as well as air flow effects. The following combustible dusts were used: paper dust from a printing press, Arabic gum powder, Pittsburgh seam coal, and brass powder. To develop an improved understanding of the heat transfer, and oxygen mass transfer phenomena occurring in the dust layer, additional instrumentation such as a second thermocouple in the dust layer, an oxygen analyzer and gas sampling line, and an air velocity probe were used in at least some tests. Hot Surface Minimum Ignition temperatures were 220oC for Pittsburgh seam coal, 360oC for paper dust, 270¡Ãƒâ€° for Arabic gum powder, and > 400oC for brass powder. The addition of 5-10 weight percent stearic acid powder resulted in significantly lower ignition temperature of brass powder. When combustible liquids were added to the dust layer, the ignition temperatures did not decrease regardless of the liquids¡¯ ignitibility because the liquids seemed to act as heat absorbents. Although air velocity on the order of 1 cm/s did not affect test results, much larger air velocities did affect the results. With 33 cm/s downward airflow at the elevation of the surface of the layer, Pittsburgh seam coal was not ignited at 230¡Ãƒâ€° which was 10¡Ãƒâ€° higher than the 220¡Ãƒâ€° hot surface ignition temperature without airflow. Based on the results and data from the additional instrumentations, modifications of the ASTM E2021 test procedure are recommended.

Cette étude porte sur l’étude et la caractérisation d’un plasma induit par laser produit par une configuration en impulsion unique et en double impulsion. Une étude bibliographique a en effet permis d’identifier que cette seconde configuration avait donné des résultats encourageants - augmentation de la probabilité d’allumage - dans le cadre d’un allumage d’un spray de kérosène à froid. Des mesures par imagerie intensifiée, strioscopie et spectroscopie ont permis de caractériser l’évolution spatiotemporelle des dimensions du plasma et l’onde de choc induite, ainsi que de mesurer l’évolution temporelle de la température et de la densité électronique dans les deux configurations d’impulsions laser considérées. Ce travail expérimental nous a permis d’identifier le délai interimpulsions comme l’un des paramètres essentiels déterminant l’efficacité du procédé en doubleimpulsion. Les observations ont également montré une physionomie du dépôt particulière, le claquage s’effectuant aux extrémités du plasma préexistant. Les observations et données obtenues lors de cette campagne expérimentale serviront de base de comparaison en vue de test d’allumages. Une étude préliminaire sur le claquage dans un spray de dodécane non-réactif a également été effectuée. / This study focuses on the characterization of laser-induced plasma with a configuration using one or two laser pulses. Indeed, a bibliographic review reported encouraging results - increase in ignition probability - for the ignition of a cold kerosene spray. Measurements were carried out, including emission imaging, schlieren imaging and emission spectroscopy, for a temporal and spatial characterization of the plasma and the shockwave. The emission spectra were used for the measurement of the temporal evolution of the temperature and electron density of the plasma, for both configuration of laser pulses. This experimental work highlighted the importance of the inter-pulses delay which is one of the key parameter for the efficiency of the dual pulse breakdown process. Observations also showed that a peculiar energy deposition process takes place when two pulses are used, the second breakdown occuring on both ends of the existing plasma. All data collected with this experimental campaign will be used for comparison in future ignition tests. A preliminary study of the breakdown process occuring in a dodecane spray has also been undertaken.

Nitrous oxide (N2O) is an inexpensive and readily available non-toxic rocket motor oxidizer. It is the most commonly used oxidizer for hybrid bipropellant rocket systems, and several bipropellant liquid rocket designs have also used nitrous oxide. In liquid form, N2O is highly stable, but in vapor form it has the potential to decompose exothermically, releasing up to 1865 Joules per gram of vapor as it dissociates into nitrogen and oxygen. Consequently, it has long been considered as a potential "green" replacement for existing highly toxic and dangerous monopropellants. This project investigates the feasibility of using the nitrous oxide decomposition reaction as a monopropellant energy source for igniting liquid bipropellant and hybrid rockets that already use nitrous oxide as the primary oxidizer. Because nitrous oxide is such a stable propellant, the energy barrier to dissociation is quite high; normal thermal decomposition of the vapor phase does not occur until temperatures are above 800 C. The use of a ruthenium catalyst decreases the activation energy for this reaction to allow rapid decomposition below 400 C. This research investigates the design for a prototype device that channels the energy of dissociation to ignite a laboratory scale hybrid rocket motor.