Self-Ignition of Diesel-Engine Model Fuels At High Pressures

The self-ignition behaviour of diesel-engine model fuels as homogeneous mixtures with air has been investigated at pressures of 13 and 40/50 bar by using the shock-tube technique. The investigated fuels are a 70% n-decane/30% α-methylnaphthalene-mixture and dimethylether. Both, the mode of self-ignition and the ignition delay times were investigated.

The self-ignition behaviour of the n-decane/α-methylnaphthalene-mixture and of dimethylether is very similar to that of n-heptane [1] with a two-step self-ignition at lower temperatures. A very short deflagrative phase is followed by a secondary explosion. The time difference between the first pressure rise due to the cool flame process and the DDT decreases with decreasing temperature, whereas the intensity of the cool flame process increases. The ignition delay times both of the 70% n-decane/30% α-methylnaphthalene-mixture and of dimethylether show a negative temperature coefficient (NTC) in the Arrhenius plot.