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The combustion process in a compression apparatus with rectangular cross section is simulated using a front tracking technique. The numerical model allows to trace the movement of the flame zone in time and space allowing the flame to change its shape and position. A two-dimensional calculation of the flow field and the flame propagation is combined with a zero dimensional calculation of thermodynamic quantities. An entrainment model is applied, crevices are taken into account. The influence of the turbulence intensity on flame propagation is modeled by the turbulent flame speed for which an expression is given. Results of numerical calculations are given for different turbulence intensities. The results of these simulations are compared with experimental data.

A single stroke compression expansion apparatus is used to investigate the flame propagation under SI engine conditions. The gas is ignited by a row of electrodes located along the center line of the cylinder head of a square cross section combustion chamber. This leads to a cylindrical flame geometry which allows spatially resolved measurements of the light emission. The quasi two dimensional flame geometry allows the determination of the origin of the light emission and the distinction between the flame zone and the regions of burnt and unburnt gas. The correlation of the light emission of the CH band at 431.5 nm with the mass burning rate is used to derive information about the mass burning rate distribution from CH band emission measurements. In the selected region of the CH band emission a considerable intensity of light emission emanating from the burnt hot gas region is also observed. From this part the emission originating from the flame zone is separated.

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.