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Results are presented for basic combustion optimisation work with an EUI system on a single-cylinder pressure-charged diesel engine with a near quiescent combustion system. A substantial improvement in the particulate/NOx trade-off was achieved by reduction of spray hole diameter, increase of injection pressure and a longer injection period. Analysis of the injection and heat release diagrams shows how the reduction of soot particulate was achieved by an increase of injection pressure with reduction of spray hole diameter. The tendency for NOx to increase was minimised by the longer injection period. The lowest air swirl gave the best results and further reductions in emissions were achieved by improvements to the nozzle and the EUI system. Steady-state simulation-cycle emission results show that with an injection pressure of 1800 bar, a low soot particulate of 0.024 g/bhp h is achieved and the total calculated particulate and NOx is within the US 94 limits for heavy-duty trucks.

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.