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This paper describes the design and performance development of the new Kohler / Lombardini KDI engine range which is a family of 3 and 4 cylinder, in line, water cooled engines covering the power range 37 - 56 kW. The paper covers the following aspects: Performance and economy Exhaust emissions over legislative cycles Deterioration factor test results Effect of fuel quality on emissions

During a test programme on a modern heavy-duty engine, measurements were made at engine-out and tailpipe of particle number and particulate mass using the draft heavy-duty inter-laboratory correlation exercise guide prepared by the UN-ECE Particle Measurement Programme (PMP)1. In addition to the PMP measurements, the elemental carbon content of the particulate matter from this programme was analysed using thermogravimetric analysis of separate filters. The particle number measurement system proved to provide a reliable and repeatable measurement procedure. Test results over a variety of operational cycles showed a reduction in particle numbers of some 3 orders of magnitude. Particle number emissions were of similar magnitude regardless of the test cycle. Background-corrected particulate mass emissions results using the partial flow dilution method showed emissions levels below 5mg/kWh over all the transient cycles tested.

The performance and emissions of a medium duty, turbocharged and aftercooled diesel engine fitted with both standard pistons and experimental pistons have been compared. The experimental pistons incorporated micro-chambers equi-spaced around the periphery of the bowl, connected to the bowl by drilled passages. The tests were run using an “A-B-A” design at three engine speeds over the load range. The paper will report that the experimental pistons have a potential for significant soot reduction without an increase in NOx emissions and with similar fuel consumption. Based on an analysis of the jet flow into and out of the micro-chambers, a possible mechanism for the soot reduction is proposed. The mechanism has been investigated further using VECTIS computational fluid dynamics (CFD) analysis.