The temporal and spatial distribution of fuel in cylinders is a key factor affecting the combustion characteristics and emission generation of a DI diesel engine. The airfuel mixing quality is critical for controlling ignition timing and combustion duration. Avoiding fuel-rich areas within the cylinder can significantly reduce soot formation as well as high local temperatures resulting in low NOx formation. The present investigation is focused on the effects of advanced fuel injections and air path strategies as well as the effects of piston geometry and fuel spray angle on air-fuel homogeneity, combustion process and their impacts on the performance and emission of the engine. A Ricardo Hydra single-cylinder engine in combination with AVL Fire CFD software was used in this investigation. An experimental analysis was conducted to assess the combustion characteristics and emissions formation of the engine under various injection strategies such as different injection timing, quantity, ratio, dwell angles between injections with various exhaust valve opening times and exhaust back pressures. A quan- titative factor named Homogeneity Factor (HF) was employed in the CFD code in order to quantify the air-fuel mixing and understand how the air-fuel homogeneity within the cylinder can influence the combustion and emissions of the engine. The investigation concludes that multiple injection strategies have the potential to reduce diesel emissions while maintaining meaningful fuel economy. Split injection can be used to improve the air-fuel mixture locally and control temperature generation during the start of combustion. Increased air-fuel homogeneity results in fewer fuel-rich areas within the cylinder and contributes to the reduction of soot emission. Extending the pre-mixed combustion phase has a direct effect on the reduction of soot formation while NOx generation is highly dependent on the scale of the primary fuel injection event.

In this study, the Partially Premixed Compression Ignition (PPCI) combustion strategy in the high-speed, direct-injection diesel engine was investigated numerically by KIVA-3V code coupled with detailed chemistry, aiming to find the solution to meet the increasingly stringent emission regulations. Using split-injection, the parameters including injection timing, split-proportion, spray angle and injection pressures have been studied for their effects on combustion performance and emissions. The effects of swirl ratio, EGR rate and boost pressure are evaluated for improving the mixing and combustion of PPCI. The Homogeneity Factor (HF) was proposed for evaluating the quality of mixing and for quantitatively investigating the effects of injection parameters and in-cylinder air motion on mixture formation. Relationships between the quality of mixing and combustion performance and emissions were discussed using this factor. The results showed that HF had well revealed overall quality of mixture and the effects of operating parameters explicitly. Different EGR compositions with varied fractions of CO2 or H2O were applied in PPCI combustion in order to evaluate the effects of EGR constituents on the combustion performance and emissions. Moreover, the parametric study was conducted under a sweep of the 2nd injection timing and EGR rate, for the understanding of the effects of CO2 and water vapour in EGR at different operating modes. The speed range and load range for the PPCI diesel combustion using split injection was investigated. The results showed that the high level of EGR rate limited the implementation of PPCI combustion at high engine load, while the engine speed was limited by increased CO emissions. The application of high level cooled EGR had the potential for extending operating limits. The proposed Premixed Rate (PR) has revealed the correlations between the degree of premixed combustion and ignition delay, together with overall equivalence ratio. Good responses in fuel consumption have been shown with increase PR. And the significant reduce in PR indicated low degree of premixed at high engine load.

Knowledge of the pressure inside the combustion chamber of a gasoline engine would provide very useful information regarding the quality and consistency of combustion and allow significant improvements in its control, leading to improved efficiency and refinement. While measurement using incylinder pressure transducers is common in laboratory tests, their use in production engines is very limited due to cost and durability constraints. This thesis seeks to exploit the time series prediction capabilities of recurrent neural networks in order to build an inverse model accepting crankshaft kinematics or cylinder block vibrations as inputs for the reconstruction of in-cylinder pressures. Success in this endeavour would provide information to drive a real time combustion control strategy using only sensors already commonly installed on production engines. A reference data set was acquired from a prototype Ford in-line 3 cylinder direct injected, spark ignited gasoline engine of 1.125 litre swept volume. Data acquired concentrated on low speed (1000-2000 rev/min), low load (10-30 Nm brake torque) test conditions. The experimental work undertaken is described in detail, along with the signal processing requirements to treat the data prior to presentation to a neural network. The primary problem then addressed is the reliable, efficient training of a recurrent neural network to result in an inverse model capable of predicting cylinder pressures from data not seen during the training phase, this unseen data includes examples from speed and load ranges other than those in the training case. The specific recurrent network architecture investigated is the non-linear autoregressive with exogenous inputs (NARX) structure. Teacher forced training is investigated using the reference engine data set before a state of the art recurrent training method (Robust Adaptive Gradient Descent – RAGD) is implemented and the influence of the various parameters surrounding input vectors, network structure and training algorithm are investigated. Optimum parameters for data, structure and training algorithm are identified.

The NOx health and environmental problems make necessary to reduce this gaseous emission from different sources. Furthermore, its increase in the last years and the difficulties to remove it with after-treatment systems already in the market make more urgent the development of new techniques. The purpose of this investigation is to study the low temperature catalytic oxidation of NO to NO2 and its adsorption over a renewable activated carbon (AC) from coconut shell. The present research presents the results of experimental work carried out using a laboratory scale reactor to investigate the low temperature catalytic oxidation of NO. Activated carbon was housed in the reactor and tests were carried out with different reactor sizes, different activated carbon forms and shapes, different gas mixtures at different temperatures and different levels of humidity to simulate dry and wet particulate-free diesel engine exhaust gas. The effects of addition of ozone in the gas on the NO oxidation were also explored. Gas analysis upstream and downstream of the catalytic reactor was carried out in all cases during the charge and regeneration of the AC. An extensive literature review in conjunction with measurement of some properties of the activated carbon helped to understand better its characteristics and behaviour. The results of this study indicate that in the case of dry gas, the activated carbon initially acts as an adsorber and only after operation of several hours, the NO oxidation that takes place in the reactor results in increased NO2 levels in the product gas. The NO conversion is affected by the activated carbon form and reaction conditions including temperature, humidity, oxygen, NO, CO2 content in the inlet gas, temperature, space velocity, linear gas velocity, residence time, reactor shape, AC pretreatment and lifespan. Water vapour has a detrimental effect on the conversion of NO to NO2 before the AC reaches the steady-state conditions. On the other hand, ozone is effective in converting NO to NO2 at room temperature. This research has developed some findings not studied or reported by other researches before and confirms and/or complements results reported in the literature review by other groups, which will benefit the development of a renewable after-treatment system of NOx emissions.

Low temperature combustion (LTC) is an appealing new method of combustion that promises low nitric oxides and soot emissions while maintaining or improving on engine performance. The three main points of this study were to develop and validate an engine model in GT-Power capable of implementing LTC, to study parametrically exhaust gas recirculation (EGR) and injection timing effects on performance and emissions, and to investigate methods to decrease pressure rise rates during LTC operation. The model was validated at nine different operating points, 3 speeds and 3 loads, while the parametric studies were conducted on 6 of the 9 operating points, 3 speeds and 2 loads. The model consists of sections that include: cylinders, ports, intake and exhaust manifolds, EGR system, and turbocharger. For this model, GT-Power calculates the combustion using a multi-zone, quasi-dimensional model and a knock-induced combustion model. The main difference between them is that the multi-zone model is directly injected while the knock model is port injected. A variety of sub models calculate the fluid flow and heat transfer. A parametric study varying the EGR and the injection timing to determine the optimal combination was conducted using the multi-zone model while a parametric study that just varies EGR is carried out using the knock model. The first parametric study showed that the optimal EGR and injection timing combination for the low loads occurred at high levels of EGR (60 percent) and advanced injection timings (30 to 40 crank angle degrees before top dead center). The optimal EGR and injection timing combination for the high loads occurred at low levels of EGR (30 percent to 40 percent) and retarded injection timings (7.5 to 5 crank angle degrees before top dead center). The knock model determined that the ideal EGR ratio for homogeneous charge compression ignition (HCCI) operation varied from 30 percent to 45 percent, depending on the operating condition. Three methods were investigated as possible ways to reduce pressure rise rates during LTC operation. The only feasible method was the multiple injection strategy which provided dramatically reduced pressure rise rates across all EGR levels and injection timings.

Societal concerns on combustion-based fuel consumption are ever-increasing. With respect to internal combustion engines, this translates to a need to increase brake fuel conversion efficiency (BFCE). Diesel engines are a relatively efficient internal combustion engine to consider for numerous applications, but associated actions to mitigate certain exhaust emissions have generally deteriorated engine efficiency. Conventionally, diesel engine emission control has centered on in-cylinder techniques. Although these continue to hold promise, the industry trend is presently favoring the use of after-treatment devices which create new opportunities to improve the diesel engine's brake fuel conversion efficiency. This study focuses on injection timing effects on the combustion processes, engine efficiency, and the engine system's responses. The engine in the study is a medium duty diesel engine (capable of meeting US EPA Tier III off road emission standards) equipped with common rail direct fuel injection, variable geometry turbo charging, and interfaced with a custom built engine controller. The study found that injection timing greatly affected BFCE by changing the combustion phasing. BFCE would increase up to a maximum then begin to decrease as phasing became less favorable. Combustion phasing would change from being mostly mixing controlled combustion to premixed combustion as injection timing would advance allowing more time for fuel to mix during the ignition delay. Combustion phasing, in turn, would influence many other engine parameters. As injection timing is advanced, in-cylinder temperatures and pressures amplify, and intake and exhaust manifold pressures deteriorate. Rate of heat release and rate of heat transfer increase when injection timing is advanced. Turbocharger speed falls with the advancing injection timing. Torque, however, rose to a maximum then fell off again even though engine speed and fueling rate were held constant between different injection timings. Interestingly, the coefficient of heat transfer changes from a two peak curve to a smooth one peak curve as the injection timing is advanced further. The major conclusion of the study is that injection advance both positively and negatively influences the diesel engine's response which contributes to the brake fuel conversion efficiency.

The aim of this research was to investigate the interaction of abrasion and corrosion on rings and liners from marine diesel engines using high sulphur residual fuels. Pure corrosion effects were simulated in a sealed vessel containing emulsified lubricant and acid. Graphite was found to stimulate corrosion of ferrite but phosphide eutectic and iron carbide remained unattacked. A reciprocating test was used to combine the mechanisms of abrasion and corrosion which have been identified as producing normal wear in marine engines. The severity of the mechanisms were balanced to produce surfaces similar to those often encountered over the centre of an engine stroke. Two engine tests, specified to compare the type and extent of wear using high and low sulphur fuels, showed that an increase in corrosion resulting from increased fuel sulphur was not directly responsible for a measured increase in top ring wear rate. Corrosion was thought to dissolve the ferritic phases to release hard phases into the system which intensified abrasion of the surfaces. It was also possible that phosphide eutectic was left at a sufficiently high level above the surface by corrosion of the matrix to cause direct abrasion of the ring. Throughout the experimental work particular emphasis was placed on examination and interpretation of the interaction of corrosion and abrasion in lubricated acidified environments.

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The interest to study diesel-gasoline fuel mix for CI engine combustion had been motivated by the higher thermal efficiency of CI engine compared to SI engine which gasoline normally runs in and the report of having lower NOx and PM emissions for gasoline combustion in CI engine. The experimental CI engine was unable to run on 100% gasoline but able to run on gasoline blend as high as G80 with default SOI timing setting. 100% gasoline would not run despite it contains only 20% more gasoline than G80 due to its extremely longer ignition delay caused by the exponential increase of gasoline blend’s ID. Engine brake thermal efficiencies of all gasoline blends tested up to G80 were comparable and averaged at 24.2%, 33.8% and 39.8% for engine speed-load conditions of 2000rev/min 2.5bar BMEP, 2000rev/min 5bar BMEP and 2000rev/min 8.5bar BMEP, accordingly. This finding confirmed that gasoline blend could be a new alternative fuel that offers comparable performance to the liquid fuel market for CI engine. In Europe, diesel blended with a small percentage of biodiesel or ethanol has been common to liquid fuel market. The study focused on ID that was closely correlated to NOx and soot formations in engine cylinder instead of NOx and PM emissions at tailpipe. The longer ID of 100% gasoline in relative to diesel could go up to 14CAD resulted in increased proportion of premixed combustion to mixing-controlled combustion at the rate of 40 Joule per CAD increase in ID. This incremental premixed combustion proportion was ideal for low NOx and soot formations in CI engine. ID was able to be discriminated into physical delay, a period dictated by engine speed-load conditions and controlled fuel breakup, fuel vaporisation and fuel-air mixing; and chemical delay, a period dictated by fuel chemical kinetic mechanism and controlled the amount of heat released. This finding gave valuable insight to the fact that proportion of premixed combustion and mixing-controlled combustion were controlled by chemical delay. Zero-dimensional theoretical combustion study with chemical kinetic mechanism confirmed that the exponential increased ID trend of gasoline blends was attributed to chemical delay. Hence a gasoline blend close to 100% gasoline would have very lean premixed combustion and small mixing-combustion which correlated to very low NOx and soot formations in cylinder. In order to understand the NOx and soot formations in cylinder in detail, a 73species reduced chemical kinetic mechanism that could represent gasoline blend combustion in CFD was developed. This reduced chemical kinetic mechanism could be used for future CFD work to understand effect of interactions between physical processes (fuel breakup, fuel vaporisation and fuel-air mixing) and chemical processes (activation of fuel combustion chemistry) on NOx and soot formations in cylinder. This work founded an effective semi-automatic reduction methodology with MATLAB algorithms for developing the 73species CFD-compatible reduced chemical kinetic mechanism of gasoline blends. This platform made building a surrogate fuel’s reduced chemical kinetic mechanism from multiple detailed chemical kinetic mechanisms of single component fuels fast, accessible and friendly to users of all background. DRG reduction technique had been enhanced by the multiple-stage ROP and multiple-step DRG approaches. The multiple-stage ROP and multiple-step approaches increased the species size reduction of chemical kinetic mechanisms by additional 8% and 13.5%, accordingly. The additional species size reduction capability of both approaches would be beneficial for the reduction of chemical kinetic mechanism for CFD use which is practically limited to size of 100species for feasible computational errors and speed. Apart from the limitation for the percentage of gasoline blend that could be used in the experimental CI engine, the lower compressibility of gasoline blends in relative to diesel had caused the SOI timing to be retarded up to 3CAD in this pump-triggered type of injection system. This shift of combustion phase had no significant effect on the ID and heat-release characteristics. The combustion phase shift can be easily compensated by advancing the SOI accordingly.

Orientador: Luiz Roberto Carrocci / Banca: João Andrade de Carvalho Junior / banca: Edson Luiz Zaparoli / Resumo: O Brasil é um país que segue, como padrão de referência para emissões, as normas européias que diferem das norte americanas em função dos limites e dos ciclos de teste. Com a globalização e comunização de componentes, objetiva-se desenvolver um único produto que possa ser empregado em diversas partes do mnndo e que apresente uma condição adequada e suficiente para uma aplicação que possa variar das altas atitudes e clima frio do Chile, até as altas temperaturas dos desertos da Arábia Saudita. Muitos desenvolvimentos de motores devem ser acompanhados da evolução da qualidade do combustível, o qual influencia diretamente no desempenho e durabilidade dos motores. Logo uma avaliação das emissões de um motor, o qual o princípio empregado para redução de emissões, está previsto para ínicio de comercialização no Brasil a partir de 2008, torna-se uma ferramenta importante para o desenvolvimento de veículos ecologicamente corretos. Paralelamente está previsto também uma melhora na composição do combustível; pode-se então dizer que, se as emissões com o atual combustível no Brasil forem inferiores aos limites programados para o ano de 2008, isto indicará que teremos um motor que irá emitir menos, quando considerada a qualidade do combustível otimizado. Concluindo, o presente trabalho possui grande importância tecnológica e estratégica para o desenvolvimento de motores Diesel além de sistemas e agregados para se reduzir emissões dentro do grupo mundial DaimlerChrysler. / Abstract: The Brazil is a country, which follows the same European emissions standard for thelimits and tests, however the current legislation in Europe will come to Brazil one step later. It means about 4 years later. With globalization, the industries are looking for costs reducing and one necessary way to get it is to have one product or, in this case one vehicle, that could be sold in different countries, foruse in high altitude and cold wheter like in chile and in high temperatures as in the Arabic deserts. Many engine developements should be made at the same time with fuel quality improvement, which has directly influence about performance and durability of the engine components. Because of it, the correct exhaust gas emissions evaluation of the high technology engine in Brazil is a very important factor to signalize the strategy for the next emissions legislation. The principal focus of this monograph is the analysis of the engine for 2008 in Brazil, now in 2003 and receive the information to prepare the Brazilian scenaio for the next years. The subject of this case is the testing of the current different kinds of Diesel fuel in Brazil determining the emissions values freom the engine EPA 2004 and with these values comparing them to the standard emission limits and explain about the comparability of results. To sum up, the current monograph has great technological and strategical importance to the Diesel engine development and also the development of aggregates and systems for emissions reducing into Daimler-Chrysler worldwide group. / Mestre