Combustion and Emission Characteristics of a PCI Engine Fueled with Ethanol-Diesel Blends 2009-01-1854
This study investigates the mechanisms of solubility, ignition, combustion and emission of ethanol diesel blend fuel for the prospect of using ethanol diesel blend in a Premixed Compression Ignition (PCI) engine. Ethanol diesel blend fuel of ethanol blend ratio 20vol% (E20) does not solubilize in atmospheric temperature, though will solubilize when heated to 323K. When applying ethanol diesel blend fuel to a PCI engine, combustion characteristics changes, which increases ignition delay and decreases the rate-of-pressure-rise. We speculated that the above combustion characteristics were shown as a result of the following three reasons: a leaner mixture caused by increase in ignition delay, fuel adhesion to cavity wall by ethanol and diesel fuels evaporation characteristics, and a decrease in combustion rate by adding ethanol. In order to determine each reason, experiments were carried out where combustion chamber geometry, Homogeneous Charge Compression Ignition (HCCI) and injection timing and injection quantity were varied.
As a result, adding ethanol leads to low cetane number causes the increase in ignition delay. The reason for the drop in rate-of-pressure-rise was a synergetic effect of, leaner mixture and adhesion at long ignition delay, and the effect of fuel evaporation property was dominant during short ignition delay. In addition, even though the combustion control of E20 was effective in low load, it was not effective above middle load except the change in ignition delay. For emission characteristics, adding ethanol increased THC but decreases the amount of NOx.