An Advanced Internal Combustion Engine Concept for Low Emissions and High Efficiency from Idle to Max Load Using Gasoline Partially Premixed Combustion

A Scania 13 1 engine modified for single cylinder operations was run using nine fuels in the boiling point range of gasoline, but very different octane number, together with PRF20 and MK1-diesel. The eleven fuels were tested in a load sweep between 5 and 26 bar gross IMEP at 1250 rpm and also at idle (2.5 bar IMEP, 600 rpm). The boost level was proportional to the load while the inlet temperature was held constant at 303 K. For each fuel the load sweep was terminated if the ignitibility limit was reached. A lower load limit of 15 and 10 bar gross IMEP was found with fuels having an octane number range of 93-100 and 80-89 respectively, while fuels with an octane number below 70 were able to run through the whole load range including idle. A careful selection of boost pressure and EGR in the previously specified load range allowed achieving a gross indicated efficiency between 52 and 55% while NOx ranged between 0.1 and 0.5 g/kWh. At high load, in the worst case, the nine gasolines showed 0.5 FSN of soot while diesel showed 2.8 FSN. In the paper it is shown that chemical reasons, rather than mixing, are behind this substantial gap. With the two best fuels, the brake parameters were estimated. It was found that soot was low, and in some cases below both the EU VI and US10 regulations. NOx was always below EU VI, and in some cases was only slight above US10 regulations. At high loads the estimated brake efficiency was roughly 50% in both cases. All the results were achieved keeping the maximum pressure rise rate within acceptable levels.