Abstract
The effect of a disturbance on a piston compression ignition of a stoichiometric n-butane/oxygen/argon mixture was observed using a rapid compression machine with a stepped piston crown in a wide temperature range. When a stepped or a dished piston crown was used for the mixture compression, the polytropic index was smaller than usual. The cool-flame onset retarded and the blue-flame delay was not changed in the cool-flame dominant temperature regime. In the blue-flame dominant temperature regime, the total ignition delay was elongated. The onset position of the hot-flame in the high temperature side of "negative-temperature-coefficient regime" was fixed near the stepped piston head. These have suggested that the stepped piston generates a disturbance have the capability of promoting a compression ignition.
