Experimental Investigation into HCCI Combustion Using Gasoline and Diesel Blended Fuels 2005-01-3733
Gasoline and diesel, the two fuels with very different characteristics and with wide availability for conventional engine use, were blended as a HCCI engine fuel. Gasoline, with high volatility, easy vaporization and mixture formation, is used to form the homogeneous charge. Diesel fuel which has good ignitability and fast combustion at the conditions predominating in the HCCI environment, is used to dominate the auto-ignition and restrain the knocking combustion. It is expected that these two different fuels with opposite but complementary properties can be used to reach a good compromise in HCCI combustion. Experiments, conducted with moderate compression ratios (CR) and using two modes of HCCI control, i.e. intake heating with CR 15.0 and negative valve overlap (NVO) with CR 10.4, yielded results that prove this expectation. The most significant results are that with increasing proportion of diesel fuel in the blend with gasoline the intake temperature required for knock-free HCCI operation was lowered, the lower end of IMEP range possible with the NVO and the excess air ratio range were extended and emissions of HC and NOx were greatly reduced throughout the engine load range where HCCI operation was possible.