Emissions from gasoline engines remain an important issue worldwide as they are both harmful to health and contribute to green house effects especially under cold start conditions. A major challenge of the automotive industry is to reduce harmful emissions as much as possible whilst continuing to reduce CO2 emissions. Three-way-catalytic converters have been used very successfully to convert the harmful gases before release to the environment but these devices have to reach their light-off temperature in order to activate the chemical reactions. Therefore, the conversion time is delayed and during the pre light-off period, high levels of emissions are released. An investigation into methods capable of increasing catalyst temperature under cold start conditions has been carried out. The most beneficial technique used in this research was the secondary air method. The method introduced extra air into the exhaust manifold which allowed the engine to run rich and then the residual unburned fuel to be oxidised in the exhaust before approaching the converter. An experiment following a Box- Behnken design was used to study the effect of engine speed, spark angle, load, relative air/fuel ratio (lambda) and secondary air flow on pre-catalyst temperature. The study suggested the best result for the engine studied was to achieve fast catalytic light-off time was to run engine at 1225 rpm, spark angle of 0 degree BTDC, lambda of 0.82 and load of 0.5 bar BMEP. These settings allowed the remaining fuel to be burned with 5.87 kg/hr of secondary air in the exhaust manifold to achieve a pre-catalytic temperature of 631.1 QC and achieve light-off for all emissions within 17.2 seconds. The results were also used to build a temperature prediction model using the Matlab MBC toolbox and the best available model gave an R2 of 0.9997 by using radial base functions (RBF). However, the optimum conditions still produced cyclic variation in the combustion, giving an average COVimep of 14.8% during the pre-catalytic heating period which caused problems concerning engine smoothness. To derive a greater insight into the mechanisms governing the cyclic variability observed a simulation study was undertaken. The study used a simulation using Ricardo WAVE and Matlab Simulink to allow a detailed representation of some of the principle mechanisms giving rise to cyclic variability under cold start conditions. The study included combustion under rich and lean mixtures and considered the effect of variations of air/fuel ratios and residual gas fraction. As a result, the simulation showed a similar characteristic variability of heat release to that observed experimentally. The validation of the model for heat release showed that the predictions were under estimated by 0.49 % while under lean combustion, there was an under estimation of 2.07%. Both predictions had normally distributed residuals. The model suggested that the residual gas fractions were higher than the limit of 8.8% (under rich fuelling) or 8.0% (under lean fuelling) that was predicted to cause ignition delay to increase significantly and therefore contribute to high cyclic variability. ' An optimisation was carried out by varying camshaft angle in the simulation. The results suggest that retarding the exhaust camshaft position by 4 degrees (EVC 12 degrees BTDC) could reduce COVimep by 63.2% under rich combustion. In contrast, advancing the intake camshaft position suggested that the COVmep can be reduced but more experimental data is required to validate the results because variation of intake camshaft positions had a larger impact on pumping work than varying exhaust camshaft positions. These additional pumping losses result in higher air and fuel flow requirements. In summary, this thesis describes a detailed investigation into the effects of engine calibration on catalyst heating performance. One of the limiting factors in achieving rapid light-off is combustion variability. Extensions have been introduced to an industry standard ID engine simulation to allow realistic cyclic variability to represented and developed. These tools could allow cyclic variability to be considered more rigorously during a calibration exercise.

A four-cylinder, four-stroke, gasoline engine with direct injection fuel was commissioned and used to achieve CAI combustion. CAI combustion was achieved by employing short-duration, low-lift camshafts and early exhaust valve closure. Trapping sufficient volumes of exhaust residual provided the necessary thermal energy needed to initiate auto-ignition. The effects of valve opening durations on the CAI operation range were investigated at different air/fuel ratios, valve timings and injection timings. Furthermore the effect on engine performance, exhaust emissions, fuel consumption and combustion characteristics were also investigated. Methods which could be used for CAI combustion region enlargement were also studied. These included spark-assisted CAI at different EVC timings and valve durations, CAI operation at 2000 rpm and CAI combustion at late fuel injection timings

The primary driver for this research was the continuing high failure rate of investments in IS/IT which has stayed at around 70-80% for over 30 years. The aim of this research was to explore the extent to which organisations have adopted benefits driven practices when undertaking investments in IS/IT. An initial phase of the research was primarily based on detailed documentation on 25 projects taken from the knowledge management database of an IS/IT consultancy. A second phase comprised in-depth case studies at three organisations. This phase explored the practices adopted on three or four projects at each organisation and importantly the wider organisational context in which the projects took place. An important contribution from this research has been the development of a framework of competences and practices for the realisation of benefits from investments in IS/IT. The empirical elements of the study then go well beyond recent survey-based research, by providing in-depth insights into the practice of benefits realisation, across a variety of organisations. The empirical study showed that benefits-related practices are very rarely adopted. The research has also provided evidence of the value of the practices 'lens', which is shown to provide a valuable way to operationalise competences, as it fits very well with how people think and work. The thesis provides some concrete suggestions as to how the practice of benefits realisation might best be improved.

Future requirements for lower automotive emissions have lead to the development of new internal combustion (IC) engine technologies. Gasoline Direct Injection (GDI), for example, is one of these promising new IC engine concepts. It offers the opportunity of increased efficiency through unthrottled operation. However, the realisation of this concept is critically dependent on the in-cylinder mixture formation, especially in the late injection/lean operation mode. Ideally, this would require a precise stratification of the in-cylinder fuel-air mixture in 3 distinct zones: an ignitable pocket located at the spark plug, surrounded by a stoichiometric mixture of fuel and air, encompassed by air. To enable this stratification, the GDI concept utilises advanced injector technology. Phase Doppler Anemometry (PDA), Planar Laser-Induced Fluorescence (PLIF) and the combination of PLIF and Mie scattering in the Laser-Sheet Dropsizing (LSD) technique, have been applied to sprays in the past to obtain dropsize information and study the mixture formation process. These new GDI sprays are denser, their droplet sizes are smaller and they evaporate faster, and as such, place us at the limit of the validity of these measurements techniques. The diagnostics were applied to a GDI spray in a pressure vessel for realistic in-cylinder conditions, ranging from supercooled to superheated environments. Tracer evaporation issues in the PLIF technique were resolved by using a dual tracer system. The study showed that the LSD technique provided good quantitative data in low evaporation regimes. In highly evaporating regimes, the technique still gave reliable dropsize data for the early stages of the injection, but was limited afterwards by vapour-phase contribution to the fluorescence signal. Variations between PDA data and LSD results also suggested a deviation of the Mie scattering signal from the assumed d2 dependence. This was further investigated and was found to be true for small droplets (d/?. <0.2). This source of error might be improved by using a different observation angle. High density seriously compromises the accuracy of PDA, whilst its effect through multiple scattering is of second order for the LSD technique. In low evaporating regimes, LSD has the overall advantage of being a 2-D measurement technique, and will yield data with a maximum error of 30% in dense parts of the spray where PDA data is totally unreliable. If the spray evaporates quickly, PLIF by itself is an appropriate tool for following the air-fuel mixture, because short droplet lifetimes limit the 2-phase flow behaviour of the spray. Particle Image Velocimetry (PIV), the LSD technique and equivalence ratio LIF measurements were applied to a BMW single cylinder optical GDI engine. The early injection operation showed no particular issues. However, the results obtained in the late injection highlighted the poor mixing and inappropriate stratification.

The purpose of the research reported in this thesis was to investigate the viability and quantify the potential gains of improving fuel economy of the gasoline engine through strategic application of additives. An increased awareness of the link between greenhouse gas emissions and global warming means that there is a desire to reduce carbon dioxide emissions from transportation. There is therefore a growing emphasis on improving the fuel economy performance of vehicles. The addition of friction modifier additives to the fuel is one way to achieve this. Using bespoke in-cylinder sampling techniques, an understanding of the operation of the piston assembly, a system responsible for much of the power loss in the internal combustion engine, is developed. Validation is given to the hypothesis that fuel economy gains can be achieved through the application of friction modifier administered to the engine via the gasoline. Results show gasoline administered friction modifier additive can accumulate in the piston assembly lubricant at levels 77 times greater than the initial fuel treatment level. The performance of a large number of friction modifier additives were uniquely screened in a novel bench-top test which simulated the arduous in-cylinder conditions found in a firing gasoline engine. The test generated vast amounts of information which led to high performance formulations capable of reducing the friction coefficient in both the boundary and mixed lubrication regimes by around 50% when compared with the result for the base oil alone. Surface analysis techniques were also employed 0!l engineering surfaces coated with friction modifier additives and add to the knowledge of their mechanism of action. Finally a series of engine tests were conducted which prove the effectiveness of friction modifier administered to the engine via the gasoline. A fuel economy improvement of approximately 2% was seen where friction modifier gasoline was employed. Application of successful technology such as this is shown to correspond to the projected saving of around 502 million litres of gasoline and 388,000 tonnes of carbon (C02) per year in the UK alone.

Engine developers and lubricant formulators are constantly improving the performance of internal combustions engines by reducing the power losses and emissions. The majority of the mechanical frictional losses generated in an engine can be attributed to the main tribological components of an engine, the valve train, piston assembly and engine bearings. However no single method has been developed to measure the friction loss contribution of each component simultaneously in a firing engine. Such results would be invaluable to the automotive/lubricant industries, research institutions and for validating predictive mathematical models for engine friction. The main focus of the research reported in this thesis was to validate an engine friction mathematical model called FLAME, developed in a separate study at Leeds. The validation was achieved by experimentally characterising the frictional losses generated from the major tribological components of a single cylinder gasoline engine. A novel experimental system was developed to evaluate experimentally, frictional losses in all the three main tribological components of an engine under fired conditions. A specially designed pulley torque transducer was used to measure valve train friction whereas improved IMEP method was adopted to measure piston assembly friction. For the very first time bearing friction was determined experimentally in a fired engine indirectly by measuring total engine friction. The FLAME engine friction model predicted valve train friction of the same order as the experimental data at engine speeds of 1500rpm and above. However, there was a much-reduced sensitivity to engine speed and temperature in the predictions. The piston assembly predicted results correlated very well with the measured data especially at lubricant inlet temperature of 80°C whereas for the bearing friction, the predicted results obtained with the short bearing approximation for the 1t film case were very close to the measured values. Overall the predicted total engine power loss results showed a good correlation with the experimental data especially at high lubricant inlet temperatures and engine speeds. It was concluded that the predicted results were in good agreement with the experimental results and the comparison validated the FLAME engine friction model.

A single piston Rapid Compression Machine (RCM) has been used to investigate the autoignition of hydrocarbons under conditions of temperature and pressure similar to those which occur in the end-gas of a spark-ignition engine under knocking conditions. Extents of reactant consumption have been measured during the course of autoignition following rapid compression of hydrocarbon-air mixtures. Evidence for the occurrence of low temperature oxidation during the compression stroke has been found and its effect on the overall ignition delay has been determined by numerical methods. The influence of diethylamine on this reactivity during compression and on the overall ignition delay has been investigated experimentally. The amine was shown to exert an inhibiting influence on the low temperature oxidation of n-heptane and n-pentane. Measurements of autoignition delays have been made over a range of compressed gas temperatures for different hydrocarbons (C4-C8). The results illustrate the relationship between autoignition delay and octane rating and the effect of molecular structure on the reactivity of hydrocarbons in an RCM. In general, as the Research Octane Number (RON) increases the duration of the ignition delay following compression to 900 K increases, however, a quantitative correlation of the two could not be made. Spatial imaging techniques (schlieren imaging, image intensified Charge Coupled Device (CCD)), used in the investigation of the spatial development of autoignition in the RCM, confirm the existence of spatial temperature inhomogeneities within the combustion chamber during the post-compression period. These imaging techniques have also been used in the study of spark-ignition and “knock” in the RCM. The ignition of methane in the RCM has been studied. The experimental results suggest that the presence of higher alkanes (ethane, propane and n-butane) or carbonaceous particles enhances the initiation of ignition of methane-oxygen mixtures. The effects of pressure and temperature on this behaviour have been explored experimentally.

Reported in this thesis is a study of combustion in a disc-shaped combustion chamber spark ignition engine, and in-cylinder flow and combustion in an idealised pent-roof spark ignition engine. Both engines were skip fired, to remove residuals and ensure a welldefined in-cylinder fuel-air mixture. Other important parameters were also controlled, e.g. inlet temperature, inlet pressure, air mass flow, mixture strength, engine speed and spark timing. With the disc-shaped spark ignition engine, a shadowgraph technique was used to study early flame development. Simultaneous natural light and shadowgraph imaging techniques were adopted to validate the later use of the former method for monitoring flame propagation in the pent-roof engine. The disc-shaped engine flame images were processed to yield mean flame radius, flame centroid and to describe flame 'circularity'. Good agreement was obtained between flame radii obtained from natural light and shadowgraph images. No correlation was found between early flame development, centroid displacement, flame 'shape' and the rate of combustion as defined by the crank angle at which peak pressure was attained. The pent-roof engine was 'mapped' to determine optimum conditions, prior to flow and flame studies on the same engine. Flow was analysed using laser doppler and particle tracking velocimetry techniques. Mean and rms velocities were obtained. Observed flow patterns at the two engine speeds tested (750 and 1500 rpm) differed and were not as expected for the simplified geometry. Similar trends in rms velocity were observed at all locations tested, with similar magnitudes at all points and in all directions tested during the critical combustion period. Simultaneous top and side natural light flame images were generated using two high-speed digital cameras; in-cylinder pressure was also recorded. The top and side images were analysed in terms of top and side successive flame positions and top and side mean flame radius. Centroid displacements, from side flame views, were also determined. No correlation was found between initial flame developments and later flame development viewed from the side.

No description available.

A spark ignition (SI) engine operating with a lean burn has the potential for higher thermal efficiency, and lower nitrogen oxide emissions than that of stoichiometric operation. However, a lean or highly diluted mixture leads to poor combustion stability impacting detrimentally upon engine performance. An experimental investigation was carried out, on a 4-valve single cylinder gasoline engine with a split intake tract and two identical production port-fuel injectors installed, allowing independent fuel delivery to each intake valve. The main objective of the study was to extend the limit of lean combustion through the introduction of charge stratification. Novel port fuel injection strategies such as, dual split injection, multiple injections and phased injection, were developed to achieve this goal. In parallel, a model of the engine was developed in the Ricardo WAVE software. The model was used to calculate parameters such as in-cylinder residual gas, for different test points. Combustion stability was improved for the engine conditions tested. At 1000 rpm and 1.0 bar gross indicated mean effective pressure (GIMEP), the lean combustion limit was extended from a 14:1 air-to-fuel ratio (AFR) to 17.5:1. At 1500 rpm and 1.5 bar GIMEP the lean combustion limit was extended from 17.5:1 to approximately 21:1 AFR. Finally for 1800 rpm and 1.8 bar GIMEP, lean combustion was improved from 21: 1 AFR to 22: 1 An experimental spark plug, with an infrared detector, was used to measure the variation in fuel distribution at the spark plug gap. It showed that the different fuel injection strategies generated different levels of fuel concentration. It was identified that injections in a single port created fuel stratification in the spark plug area but were more prone to cycle to cycle variations in fuel concentration. These variations did not correlate with combustion stability or flame speed propagation at the speeds and loads tested. The most important parameter to influence the flame propagation speed was found to be the variation in local lambda with crank angle just after the ignition timing. It was shown that the fastest flame propagation speeds did not necessarily result in the lowest CoV in GIMEP. Finally the fuel injection strategies were investigated for highly dilute conditions, achieved by means of internal residual gas trapping, with the aim of promoting (spark-assisted) compression ignition combustion conditions.