Potential of Ozone to Enable Low Load Operations of a Gasoline Compression Ignition (GCI) Engine.

Paper #:
  • 2017-01-0746

  • 2017-03-28
Gasoline Compression Ignition (GCI) engine based on Gasoline Partially Premixed Combustion (GPPC) showed potential for high efficiency and reduced emission of NOx and Soot. However, because of the high octane number of gasoline, misfire and unstable combustion dramatically limit low load operating conditions. In previous work, seeding the intake of the engine with ozone showed potential for increasing the fuel reactivity of gasoline. The objective of this work was to evaluate the potential of ozone to overcome the low load limitations of a GCI engine. Experiments were performed in a single-cylinder light-duty CI engine fueled with 95 RON gasoline. Engine speed was set to 1500 rpm and intake pressure was set to 1 bar in order to investigate typical low load operating conditions. In these conditions, high intake temperatures, not available during conventional engine operations, were necessary to enable gasoline autoignition. Results showed that systematically increasing the ozone concentration, allowed to progressively reduce the intake temperature requirement up to 40°C while maintaining a constant combustion phasing. During this process, combustion initiated and developed at lower temperatures, reducing the production of NOx and maintain a low level of soot. In order to take advantage of the effect of ozone, the injection strategy had to be adapted: a first injection during the intake stroke was necessary to get the promoting effect of ozone while a second injection during compression stroke was employed to induce the fuel stratification necessary for controlling the combustion phasing. In these conditions, stable operations were achieved at 2 and 3 bar IMEP at 1500 rpm with low NOx, Soot, and with low noise without the use of boosting or hot trapped residuals. Moreover, results showed that with adequate capacity of the ozone generator, low load operation can be extended to higher engine speeds and idle conditions.
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