Technical Paper
Characterization of Knock and Its Effect on Surface Temperatures
1992-02-01
920514
Knock in a spark-ignition engine was characterized in terms of its occurrence and magnitude or intensity. Cylinder pressure data from 90 consecutive individual cycles were generated from a single-cylinder engine of disc chamber design at about 72kHz sampling rate over a range of operating conditions between no knock and 100% of the cycles knocking. Mean values and distribution of following parameters were analysed: knock occurrence crank angle, knock intensity, combustion rate and the end-gas thermodynamic state. The effects of fuel octane number and inlet air temperature on these parameters were studied. The thermal imaging technique has been applied to record two-dimensional surface temperatures of cylinder head and piston simultaneously. The change in surface temperatures during knocking and non-knocking cycles was thus studied. As expected, increase in the inlet air temperature or decrease in the fuel octane number caused the knock onset to occur at less advanced spark timing.