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The electrification of powertrains provides a critical opportunity to change the way that engines are designed and developed, allowing their efficiency to be increased and their cost reduced. This paper draws on ongoing Ricardo projects in the field of dedicated hybrid engines (DHEs). The Magma xEV combustion concept employs very high compression ratio, long stroke architecture, and advanced ignition and knock mitigation technologies, for DHEs requiring the highest efficiency. In the latest research project a pre-chamber combustion system (with both active and passive operation) has been applied to the Magma xEV engine, in order to enable the highest levels of charge dilution and further increase brake thermal efficiency. The research focussed on benefits of pre-chamber ignition as compared to conventional spark ignition and corona discharge ignition. The comparison of charge dilution using excess air (lean operation) and exhaust gas recirculation are presented.

Compared to conventional homogeneous direct injection or port-fuel injected engines, the second generation, spray guided, direct injection engine (SGDI) has the potential for significantly improved fuel economy during part load stratified charge operation. Multiple fuel injection strategies can be utilised to increase the unthrottled operating range, leading to further improvements in fuel economy. However, careful optimisation of these strategies is essential to ensure that benefits are maintained whilst further minimising emissions within combustion stability limits and consumer driveability demands. The effects of multiple injection strategies upon fuel consumption, emissions and combustion stability were investigated in a single cylinder Ricardo Hydra engine with a spray guided combustion system. An outwardly opening piezoelectric actuated injector was employed. The fuel injection strategy utilised up to five injections per engine cycle.

The 2/4SIGHT engine concept is based on a novel design of combustion system, which makes use of an electric-hydraulic valvetrain and advanced control technologies, enabling automatically controlled dynamic switching of the engine between two- and four-stroke operations. This concept has the potential to improve fuel consumption by up to 30% compared to a conventional gasoline engine. A 3 cylinder GDI engine with two stage boosting system and electro-hydraulic valvetrain is the main application for this project, with 6 cylinder application being studied in simulation. The design of a Control System poses several challenges due to the simultaneous introduction of several innovations such as advanced boost system, electro-hydraulic valvetrain system and two/four stroke operating mode. In order to develop and optimise the design of the control system, an integrated simulation environment has been developed.

A single cylinder research engine has been used to study a range of gasoline combustion chamber designs which have been divided into three categories open, compact and four valve. Measurements of fuel consumption and exhaust emissions are presented at full load and part load conditions, and a comparison is made of the best chamber from each category. At full load the performances of the three chambers were very similar at low speeds but at high speeds the superiority of the four-valve was clearly shown. At part load there were significant differences in the burn rate when operating at lean mixtures with the compact design showing the highest level and hence the most extended lean limit. The relationship between part load fuel consumption and full load octane requirement is presented as a method of comparing the relative performance of a range of combustion chamber designs.