A gasoline direct injection engine was set-up to operate with a dynamometer in a test cell. Test cycle and emissions measurement procedures were developed for evaluating the regulated and non-regulated gaseous emissions. Equipment and techniques for particulate matter measurements were adapted for use with the gasoline direct injection engine. The particulate matter emissions produced by the engine were compared between two different fuels; gasoline and E10 (10% ethanol and 90% gasoline). The gaseous emissions generated by the engine when it was run on gasoline and E30 (30% ethanol and 70% gasoline) were also compared. Particle number decreased with E10 for hot start conditions, while the opposite was observed for cold start conditions. Particulate matter emissions were found to track with acetylene and ethylene emissions.

A gasoline direct injection engine was set-up to operate with a dynamometer in a test cell. Test cycle and emissions measurement procedures were developed for evaluating the regulated and non-regulated gaseous emissions. Equipment and techniques for particulate matter measurements were adapted for use with the gasoline direct injection engine. The particulate matter emissions produced by the engine were compared between two different fuels; gasoline and E10 (10% ethanol and 90% gasoline). The gaseous emissions generated by the engine when it was run on gasoline and E30 (30% ethanol and 70% gasoline) were also compared. Particle number decreased with E10 for hot start conditions, while the opposite was observed for cold start conditions. Particulate matter emissions were found to track with acetylene and ethylene emissions.

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Direct fuel injection technology is increasingly being applied to the spark ignition internal combustion engine as one of the many actions required to reduce the CO2 emissions from road transport. Whilst the potential for CO2 reductions is compelling, the technology is not without disadvantages. Early examples typically emitted over an order of magnitude more Particulate Matter (PM) than vehicles with conventional spark ignition engines. Consequently, future revisions to European and North American exhaust emissions legislation are likely to regulate the particulate emissions from vehicles with direct injection gasoline engines. This thesis undertakes to investigate a) instrumentation capable of simultaneously resolving the number concentration and size distribution of particles in the 5-1000 nm size range and b) the factors affecting the PM emissions from spark ignition engines with direct fuel injection. The first objective is achieved by evaluation and comparison of a differential mobility spectrometer; photo-acoustic soot sensor; condensation particle counter and electrical low pressure impactor. To address the second question, a differential mobility spectrometer is applied to quantify the PM emissions from a number of direct injection gasoline engines, together with investigation of their dependence on various calibratable parameters, operating temperature and fuel composition. The differential mobility spectrometer showed good agreement with the other more established instruments tested. Moreover, it exhibited a faster time response and finer resolution in particle size. The number weighted size distribution of the PM emitted was typically lognormal with either one or two modes located between 20 and 100 nm. Chemical analysis of PM samples showed the presence of elemental carbon, volatile organic material and sulphates. Transient PM measurements enabled short time-scale events such as mode switching between homogeneous and stratified mixture preparation to be identified. PM number concentrations in stratified mode exceeded those in homogeneous mode by a factor of 10-100. Dynamometer based experiments showed that PM emissions increase for rich air fuel ratios, retarded fuel injection and advanced ignition events. They also demonstrated a strong dependence on fuel composition: the highest PM emissions were measured with an aromatic fuel, whereas blending alcohols such as methanol or ethanol tended to suppress PM emissions, particularly in the accumulation mode size range. These measurements are amongst the first of their kind and demonstrate the applicability of the differential mobility spectrometer to the measurement of ultra-fine particulate emissions from engines with direct fuel injection systems. Numerous explanations are put forward to describe the data obtained, together with suggestions for future work on PM control and abatement.

Um motor ciclo Otto funcionando com injeção direta de gás natural, durante o curso de admissão, foi submetido a ensaios de plena carga em um dinamômetro corrente de Foucaut. Os resultados obtidos revelam um aumento de eficiência volumétrica do motor com injeção direta de GNC em relação à injeção indireta de GNC realizada no coletor de admissão, a montante da borboleta do acelerador. Na adaptação para operação com injeção direta de gás natural, as características técnicas do motor não foram alteradas. Um conjunto de injeção direta de gás natural, com gerenciamento eletrônico, foi inserido no cabeçote do motor de testes. Mantendo-se a pressão da linha de alimentação de gás natural constante, através de uma válvula redutora, a quantidade de combustível injetada no cilindro foi ajustada variando-se o tempo de abertura da válvula elétrica injetora de combustível. Dados de desempenho do motor são comparados, destacando-se os fatores que contribuem para este aumento relativo de eficiência volumétrica. Discute-se ainda, modificações a serem implementadas no motor visando maximizar sua potência com injeção direta de gás natural / Otto cycle engine direct injection natural gas, during the inlet stroke, submitted to runs with full power in a Foucaut dynamometer. The results obtained show a increase in the volumetric efficiency of the engine with natural gas direct injection when compared which natural gas injection apllied in the inlet manifold, upstream of the throttle butterfly. ln the conversion to natural gas direct injection, the technical characteristics of the were not changed. A kit for natural gas direct injection, with eletronic managment, was located on the cylinder head of the test engine. Maintaining the pressure constant in the natural gas fuel line, using a reduction valve. The mass of fuel injected into the cylinder was regulated, varying the opening time of the solenoid valve fuel injector. Engine performance data is compared, emphasizing the factors that contribute to this increase in relative volumetric efficiency. Modifications to be made to maximize the power of the engine with natural gas direct injection

Understanding the physics governing primary atomization of high pressure fuel sprays is of paramount importance to accurately model combustion in direct injection engines. The small length and time scales of features that characterize this process falls below the resolution power of typical grids in CFD simulations, which necessitates the inclusion of physical models (sub-models) to account for unresolved physics. Unfortunately current physical models for fuel spray atomization used in engine CFD simulations are based on significant empirical scaling because there is a lack of experimental data to understand the governing physics. The most widely employed atomization sub-model used in current CFD simulations assumes the spray atomization process to be dominated by aerodynamically-driven surface instabilities, but there has been no quantitative experimental validation of this theory to date. The lack of experimental validation is due to the high spatial and temporal resolutions required to simultaneously to image these instabilities, which is difficult to achieve. The present work entails the development of a diagnostic technique to obtain high spatial and temporal resolution images of jet breakup and atomization in the near nozzle region of Gasoline Direct Injection (GDI) sprays. It focuses on the optical setup required to achieve maximum illumination, image contrast, sharp feature detection, and temporal tracking of interface instabilities for long-range microscopic imaging with a high-speed camera. The resolution and performance of the imaging system is characterized by evaluating its modulation transfer function (MTF). The setup enabled imaging of GDI sprays for the entire duration of an injection event (several milliseconds) at significantly improved spatial and temporal resolutions compared to historical spray atomization imaging data. The images show that low to moderate injection pressure sprays can be visualized with a high level of detail and also enable the tracking of features across frames within the field of view (FOV)

This thesis considers the effect of compression ratio on the performance of a direct injection diesel engine. One aspect of engine performance is considered in great detail, namely the combustion performance at increased clearance volume. This aspect was of particular interest because variable compression ratio (VCR) systems normally operate by varying the clearance volume. The investigation relied upon results obtained both from experimental and computer simulating models. The experimental tests were carried out using a single-cylinder direct-injection diesel engine, under simulated turbocharged conditions at a reduced compression ratio. A number of one-dimensional computer models were developed; these simulate the induction and compression strokes, and the fuel spray trajectories in the presence of air swirl. The major objectives of the investigation were: to assess the benefits of VCR in terms of improvements in output power and fuel economy; to assess the effects on combustion of increased clearance volume, and investigate methods for ameliorating resulting problems; develop computational models which could aid understanding of the combustion process under varying clearance volume conditions. It was concluded that at the reduced compression ratio of 12.9:1 (compared to the standard value of 17.4:1 for the naturally-aspirated engine), brake mean effective pressure (BMEP) could be increased by more than 50%, and the brake specific fuel consumption (BSFC) could be reduced by more than 20%. These improvements were achieved without the maximum cylinder pressure or engine temperatures exceeding the highest values for the standard engine. Combustion performance deteriorated markedly, but certain modifications to the injection system proved successful in ameliorating the problems. These included: increase in the number of injector nozzle holes from 3 to 4, increase in injection rate by about 28%, advancing injection timing by about 6°CA. In addition, operation with weaker air fuel ratio, in the range of 30 to 40:1 reduced smoke emissions and improved BSFC. Use of intercooling under VCR conditions provided only modest gains in performance. The NO emission was found to be insensitive to engine operating conditions (fixed compression ratio of 12.9:1), as long as the peak cylinder pressure was maintained constant. Engine test results were used in order to assess the accuracy of four published correlations for predicting ignition delay. The best prediction of ignition delay with these correlations deviated by up to 50% from the measured values. The computer simulation models provided useful insights into the fuel distribution within the engine cylinder. It also became possible to quantify the interaction between the swirling air and the fuel sprays, using two parameters: the crosswind and impingement velocities of the fuel spray when it impinges on the piston-bowl walls. Tentative trends were identified which showed that high crosswind velocity coincided with lower smoke emissions and lower BSFC.

With increasing concerns about the harmful effects of conventional liquid fossil fuel emissions, natural gas has become a very attractive alternative fuel to power prime movers and stationary energy conversion devices. This research studies the injection and ignition numerically for natural gas (mainly methane) as a fuel applied to diesel engine. Natural gas injector and glow plug ignition enhancement are two of the most technical difficulties for direct injection natural gas engine design. This thesis models the natural gas injector, and studies the characteristics of the internal flow in the injector and natural gas jet in the combustion chamber during the injection process. The poppet valve model and pintle valve model are the first reported models to simulate the natural gas injector to improve the traditional velocity and pressure boundary conditions. This thesis also successfully models the glow plug assisted natural gas ignition and combustion processes by developing a glow plug discretized model and a novel virtual gas sub-layer model. Glow plug discretized model can describe the transient heat transfer, and adequately represents the thin layers of heat penetration and the local temperature difference due to the cold gas jet impingement. The virtual gas sub-layer model considers complicated physical processes, such as chemical reaction, heat conduction, and mass diffusion within the virtual sub-layers without significantly increasing computational time and load. KIVA-3V CFD code was chosen to simulate the fluid flow. Since the KIVA-3V is designed specifically for engine research application with conventional liquid fuels, many modifications have been implemented to facilitate this research.

With increasing concerns about the harmful effects of conventional liquid fossil fuel emissions, natural gas has become a very attractive alternative fuel to power prime movers and stationary energy conversion devices. This research studies the injection and ignition numerically for natural gas (mainly methane) as a fuel applied to diesel engine. Natural gas injector and glow plug ignition enhancement are two of the most technical difficulties for direct injection natural gas engine design. This thesis models the natural gas injector, and studies the characteristics of the internal flow in the injector and natural gas jet in the combustion chamber during the injection process. The poppet valve model and pintle valve model are the first reported models to simulate the natural gas injector to improve the traditional velocity and pressure boundary conditions. This thesis also successfully models the glow plug assisted natural gas ignition and combustion processes by developing a glow plug discretized model and a novel virtual gas sub-layer model. Glow plug discretized model can describe the transient heat transfer, and adequately represents the thin layers of heat penetration and the local temperature difference due to the cold gas jet impingement. The virtual gas sub-layer model considers complicated physical processes, such as chemical reaction, heat conduction, and mass diffusion within the virtual sub-layers without significantly increasing computational time and load. KIVA-3V CFD code was chosen to simulate the fluid flow. Since the KIVA-3V is designed specifically for engine research application with conventional liquid fuels, many modifications have been implemented to facilitate this research.

The diesel fuel is used widely in the country and the world. Moreover, growing environmental awareness leads to a larger demand for renewable energy resources. The pioneering in the use of ethanol makes Brazil also bears some conditions to move quickly to consolidate the use of the biodiesel in larger scales, in the replacement or as a blend with mineral diesel in diesel engines. Thus, this work evaluated by tests on a dynamometer bench, the performance of an agricultural tractor equipped with direct injection engine using different blends of soybeans methyl biodiesel. Also, it was analyzed the influence of additives to improve the performance, and it was used two positions of injection timing, one of them original and the other advanced. The best results were obtained using the B10 fuel for all performance parameters measured (torque, power and specific fuel consumption). For the variable torque this proportion presented values 0.4% higher than the values presented by the B5 proportion, being that, for the variable power, the values of B10 fuel were higher 0.2% compared to B5, making the differences between the fuels virtually inexpressive. Already the B100 fuel presented the lowest performance in torque, power and specific fuel consumption. For the specific fuel consumption, this proportion presented the highest values, 10% higher than the values for B10 fuel. Regarding the use of additives and the variation of the initial injection timing it was not identified significance in the results. For these test conditions, where tests were realized in a tractor model 1986, equipped with an engine with 3000 hours of work, it is possible to observe that there is the possibility of use higher concentrations of biodiesel added to mineral diesel without the necessity of engine modifications. However, it is perfectly normal that happened a performance fall under the use of higher levels of soybeans methyl biodiesel. Thus, should be consider the use of higher proportions of biodiesel added to diesel commercial, doing an analysis of the economic viability inherent of biofuels use. / O óleo diesel combustível é utilizado em grande escala no país e no mundo. Por outro lado, a crescente conscientização ambiental acarreta em uma maior demanda por recursos energéticos renováveis. O pioneirismo no uso do etanol faz com que o Brasil também ostente condições de avançar rapidamente na consolidação do uso do biodiesel em maiores escalas, na substituição ou em mistura ao diesel de origem mineral em motores de Ciclo Diesel. Assim, o presente trabalho avaliou, por meio de ensaios em bancada dinamométrica, o desempenho de um trator agrícola equipado com motor de injeção direta sob a utilização de diferentes misturas de biodiesel metílico de soja. Também foi avaliada a influência da adição de aditivos para a melhoria de desempenho, bem como foram utilizados dois pontos de avanço de injeção, sendo um deles original e o outro adiantado. Os melhores resultados foram obtidos sob a utilização do combustível B10, para todos os parâmetros de desempenho avaliados (torque, potência e consumo específico de combustível). Para a variável torque essa proporção apresentou valores apenas 0,4% maiores que os apresentados pela proporção B5, sendo que, para a variável potência, os valores do combustível B10 foram superiores em apenas 0,2% em relação ao B5, tornando praticamente inexpressivas as diferenças entre tais combustíveis. Já o combustível B100 apresentou o menor desempenho em torque, potência e consumo específico. Em relação ao consumo específico, essa proporção apresentou os maiores valores, 10% superiores aos valores apresentados pelo combustível B10. Quanto ao uso de aditivos e o avanço no ponto inicial de injeção não foi identificada maior significância nos resultados obtidos. Para estas condições de ensaio, onde foram realizados testes em um trator modelo 1986, dotado de um motor com 3000 horas de uso, percebe-se que há a possibilidade de utilização de maiores teores de biodiesel adicionado ao diesel de origem mineral sem a necessidade de maiores modificações no motor. Todavia, é perfeitamente normal que ocorra relativa queda de desempenho sob o uso de maiores teores de biodiesel metílico de soja. Assim, deve-se considerar a possibilidade de utilização de maiores proporções de biodiesel adicionado ao diesel comercial, realizando-se uma análise da viabilidade econômica inerente ao uso desses biocombustíveis.