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The flame front propagation in normal and abnormal combustion was investigated. Cycle-resolved flame emission imaging was applied in the combustion chamber of a port fuel injection boosted spark ignition engine. The engine was fuelled with a mixture of 90% iso-octane and 10% n-heptane by volume (PRF90). The effect of fuel injection phasing was studied. The combustion process was followed from the flame kernel formation until the opening of the exhaust valves. Different phenomena correlated to the abnormal combustion were analysed. Detailed information on ignition surfaces, end-gas auto-ignitions and knock were obtained. The appearance of autoignition centres in the end gas was evaluated in terms of timing, location and frequency of occurrence.

The capabilities of the spectral extinction and scattering technique to follow the time history of the particulate concentration in the exhaust of a Diesel engine were evaluated. Simultaneous measurements of extinction and scattering coefficients from UV to visible were performed at 1.5 m downstream the exhaust valve. The measurements were triggered with the exhaust valve lift. The exhaust stroke was divided in three time windows of 1 ms in which the optical signals of 100 consecutive cycles were detected. The mean diameter, the concentration and the properties of soot particles were evaluated. The cyclic variation of measurements was also estimated.