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This work involved study of the effects of alcohol blends on combustion, fuel economy and emissions in a single cylinder research engine equipped with a mechanical fully variable valvetrain on the inlet and variable valve timing on the exhaust. A number of splash blends of gasoline, iso-octane, ethanol and butanol were examined during port fuel injected early inlet valve closing operation, both with and without variable valve timing. Under low valve overlap conditions, it was apparent that the inlet valve durations/lifts required for full unthrottled operation were remarkably similar for the wide range of blends studied. However, with high valve overlap differences in burning velocities and internal EGR tolerances warranted changes in these valve settings.

This work was concerned with evaluation of the performance and emissions of potential future biofuels during advanced spark ignition engine operation. The fuels prepared included three variants of gasoline, three gasoline-ethanol blends and a gasoline-butanol fuel altogether covering a range of oxygen mass concentrations and octane numbers to identify key influencing parameters. The combustion of the fuels was evaluated in a turbocharged multi-cylinder direct fuel injection research engine equipped with a standard three-way catalyst and an external EGR circuit that allowed use of either cooled or non-cooled EGR. The engine operating effects studied at both part and boosted high load conditions included fuel injection timing and pressure, excess air tolerance, EGR tolerance and spark retard limits. A number of blends were also mapped at suitable sites across the European drive cycle under downsized engine conditions.

The work was concerned with experimental study of the turbulent flame development process of ethanol fuels in an optically accessed spark ignition research engine. The fuels were evaluated in a single cylinder engine equipped with full-bore overhead optical access and operated at typical stoichiometric part-load conditions. High-speed natural light (or chemiluminescence) imaging and simultaneous in-cylinder pressure data measurement and analysis were used to understand the fundamental influence of both low and high ethanol content on turbulent flame propagation and subsequent mass burning. Causes for the difference in cyclic variations were evaluated in detail, with comparisons made to existing burning velocity correlations where available.

Through improving the 48V hybrid vehicle archetype, governmental emission targets could be more easily met without incurring the high costs associated with increasing levels of electrification. The braking energy recovery function of hybrid vehicles is recognised as an effective solution to reduce emissions and fuel consumption in the short to medium term. The aim of this study was to evaluate methods to maximise the braking energy recovery capability of the 48V hybrid electric vehicle over pre-selected drive cycles using appropriately sized electrified components. The strategy adopted was based upon optimising the battery chemistry type via specific power capability, so that overall brake power is equal to the maximum battery charging power in a typical medium-sized passenger car under typical driving. This will maximise the regenerative braking energy whilst providing a larger torque assistance for a lower battery capacity.

Natural Gas (NG) is currently a cost effective substitute for diesel fuel in the Heavy-Duty (HD) diesel transportation sector. Dual-Fuel engines substitute NG in place of diesel for decreased NOx and soot emissions, but suffer from high engine-out methane (CH4) emissions. Premixed Dual-Fuel Combustion (PDFC) is one method of decreasing methane emissions and simultaneously improving engine efficiency while maintaining low NOx and soot levels. PDFC utilizes an early diesel injection to adjust the flammability of the premixed charge, promoting more uniform burning of methane. Engine experiments were carried out using a NG and diesel HD single cylinder research engine. Key speeds and loads were explored in order to determine where PDFC is effective at reducing engine-out methane emissions over Conventional Dual-Fuel which uses a single diesel injection for ignition.

This experimental work was concerned with the combination of internal EGR with an early inlet valve closure strategy for improved part-load fuel economy. The experiments were performed in a new spark-ignited thermodynamic single cylinder research engine, equipped with a mechanical fully variable valvetrain on both the inlet and exhaust. During unthrottled operation at constant engine speed and load, increasing the mass of trapped residual allowed increased valve duration and lift to be used. In turn, this enabled further small improvements in gas exchange efficiency, thermal efficiency and hence indicated fuel consumption. Such effects were quantified under both port and homogeneous central direct fuel injection conditions. Shrouding of the inlet ports as a potential method to increase in-cylinder gas velocities has also been considered.

The work was concerned with the use of exhaust gas recirculation to minimise CO2 and pollutant emissions over a wide operating range in a multi-cylinder research engine. Under part-load conditions a combination of internal and external EGR was used to invoke controlled auto ignition combustion and improve fuel consumption. Outside the CAI regime, small additional fuel savings could be made by employing reduced EGR rates in spark ignition combustion mode. At boosted high load conditions a comparison of excess fuel, excess air and cooled external EGR charge dilution was made. It was apparent that cooled EGR was a more effective suppressant of knock than excess air, with combustion phasing further advanced towards the optimum and improved combustion stability achieved over a wider operating range. The full load emissions reduction potential of EGR was also demonstrated, with emissions of CO2 reduced by up to 17% and engine-out HC and CO decreased by up to 80%.

This work was concerned with increasing the attainable load during gasoline controlled auto-ignition combustion in a multi-cylinder direct fuel injection research engine. To extend the peak output under naturally aspirated conditions it proved favourable to combine internal and external exhaust gas recirculation under stoichiometric fuelled conditions. During turbocharged high load operation it was beneficial in terms of fuel economy to dilute the charge with a combination of internally re-circulated exhaust gases and excess air. Replacing a proportion of these diluents with externally re-circulated burned gases appeared to facilitate lower emissions of HC and CO. The highest load generated via boost was limited by increasing peak in-cylinder pressure and falling gas exchange efficiency. Regardless, the use of boost increased the load at which CAI could be invoked without lean NOx after-treatment.

The work was concerned with applying cooled EGR for improved high load fuel economy and reduced pollutant emissions in a turbocharged gasoline engine. While the thermodynamic benefits of EGR were clear, challenges remain to bring the technique to market. A comparison of pre and post compressor EGR supply indicated that post-compressor routing allowed higher compressor efficiencies to be maintained and hence reduced compressor work as the mass flow of EGR was increased. However, with this post-compressor routing, attaining sufficient EGR rate was not possible over the required operating map. Furthermore, at higher engine speeds where the pre-turbine exhaust pressure was greater than the intake plenum pressure, the timing of peak in-cylinder pressure was not as readily advanced towards the optimum.

An experimental study has been carried out with the end goal of minimizing engine-out methane emissions with Premixed Micro Pilot Combustion (PMPC) in a natural gas-diesel Dual-Fuel™ engine. The test engine used is a heavy-duty single cylinder engine with high pressure common rail diesel injection as well as port fuel injection of natural gas. Multiple variables were examined, including injection timings, exhaust gas recirculation (EGR) percentages, and rail pressure for diesel, conventional Dual-Fuel, and PMPC Dual-Fuel combustion modes. The responses investigated were pressure rise rate, engine-out emissions, heat release and indicated specific fuel consumption. PMPC reduces methane slip when compared to conventional Dual-Fuel and improves emissions and fuel efficiency at the expense of higher cylinder pressure.