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Partially Premixed Combustion (PPC) is a combustion concept by which it is possible to get low smoke and NOx emissions simultaneously. PPC requires high EGR levels and injection timings sufficiently early or late to extend the ignition delay so that air and fuel mix extensively prior to combustion. This paper investigates the operating region of single injection diesel PPC in a multi cylinder heavy duty engine resembling a standard build production engine. Limits in emissions and fuel consumption are defined and the highest load that fulfills these requirements is determined. Experiments are carried out at different engine speeds and a comparison of open and closed loop combustion control are made as well as evaluation of an extended EGR-cooling system designed to reduce the EGR temperature. In this study the PPC operating range proved to be limited.

In order to meet new worldwide emission regulations for heavy-duty diesel engines and to provide high specific power output without fuel consumption penalties there is a requirement for the fuel injection system to have a flexible choice of injection characteristics. Such a fuel injection system has to provide multiple injections, modulated injection pressures and rates for every injection, and possibly variable spray cone angle to accommodate early injection without wall wetting whilst maintaining conventional injection for rated power. The aim of this paper is to present the advanced hybrid electronic unit injector system (EUI). This system incorporates an accumulator rail, which enables high pressure multiple injection events at different injection pressures for a very wide range of injection timings that would not normally be achievable using a conventional EUI system and single lobe EUI camshaft.