Experimental analysis of knock in single-cylinder HCCI engine fuelled premixed PRFs

HCCI combustion is auto-ignition of dilute and homogenous fuel-air mixture, which is controlled by the chemical kinetics. When rich fuel-air mixture is compressed and ignited simultaneously, the combustion rate is much rapidly and knock is occurred. This work is to develop the method for quantifying knock intensity and evaluating criterion for determining the knock. The spectral of the cylinder pressure on the PRFs (primary reference fuels) with different octane number at the distinctive operating points is investigated. The result shows that, different PRFs give similar major frequency band for HCCI knock combustion and the major frequency bank of knock of HCCI is between 4 kHz and 12 kHz. Pbps which is the amplitude of pressure by band pass filter between 4 kHz and 12 kHz is used to quantify knock intensity. When Pbps is over 0.15 MPa, knock is presented in HCCI combustion. Hence, the safe operation region of the PRFs with the different octane number should be controlled under this value.