Simplification of ignition kernel propagation with low-temperature oxidation and investigation on new regime of flame propagation

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Ignition kernel propagation in the system with a temperature gradient at high pressures was recorded by a high-speed camera for n-heptane and iso-octane, which are primary reference fuels of gasoline. In the iso-octane case, as a flame propagated to the upstream (low-temperature region), the propagation speed monotonically decreased. In the n-heptane case, on the other hand, on the way of the ignition kernel propagation, the propagation speed showed rapid increase and decrease. In the numerical simulation, small heat release in the upstream of the ignition kernel due to the low-temperature oxidation was observed. Therefore, the rapid variation of the propagation speed in the n-heptane case would be due to re-ignition by the low-temperature oxidation.