Ozone Seeding Effect on the Ignition Event in HCCI Combustion of Gasoline-Ethanol Blends

Paper #:
  • 2017-01-0727

  • 2017-03-28
The transportation sector adds to the greenhouse gas emissions worldwide. One way to decrease this impact from transportation is by using renewable fuels. Ethanol is a readily available blend component which can be produced from bio blend-stock, today used in low concentrations in gasoline internationally. One some markets fuel containing up to 85 vol% ethanol is used. This study focuses on gasoline blended with 50vol% ethanol. The high ethanol blended gasoline was used in a direct injection light duty engine, originally designed for diesel combustion. Due to the high ignition resistance of the fuel, it required high intake temperatures of 180°C to achieve stable combustion at low load operation. To enable combustion with the lower intake temperatures more commonly used in commercial vehicles, ozone was injected with the intake air. Experiments were performed at intake air temperatures from 100°C to 170°C, at an engine speed of 1500 rpm. This experimental work was combined with chemical kinetic analysis done in Senkin, in which the effect on ignition delay from different concentrations of ethanol addition was tested. The gasoline was represented by a mechanism for iso-octane. Ozone has previously been shown to successfully decrease the intake temperature requirement when using gasoline, diesel and reference fuels of iso-octane and n-heptane. The ozone decomposes into O* radicals, which assists in the pre-reactions and therefore enable the use of lower intake temperatures than without the use of ozone. The purpose of this study was to see whether the ozone had an ignition improver effect on gasoline fuels with higher concentrations of ethanol. It was shown that stable combustion could be enabled for intake temperatures that without ozone led to misfire. Pre-reactions were studied in detail, and the effect of ozone was charted and compared with previous results for gasoline with low (5vol%) ethanol concentrations.
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