Detection of Transient Species in Ignition Process by using Sensitive and Fast Sampling Method

A crank angle resolved gas sampling method has been developed in order to detect intermediate species produced during processes of compression ignition, as well as the two-step consumption of fuel components. The direct mass-spectrometric detection through the differential pumping system enabled to observe unstable and low vapor pressure species such as hydrogen peroxide. It was found that toluene has a non-linear effect to lower the ignitability of n-heptane in terms of mixing ratio, while the iso-octane effect is linear. This difference is accounted for by the chain reaction mechanism of low temperature oxidation, in which toluene has lower rate constant with OH and lower OH reproduction index than iso-octane.