In one arrangement described, three nozzles are arranged in different planes. The nozzles project through the walls of the cylinder at a distance of 120 Degrees from each other, and are not directed radially but inclined to the radius forming chords, so that by their combined action a spiral movement is imparted to the fuel and air.
Another arrangement has one nozzle which injects the fuel from the centre of the cylinder radially outwards in two different planes.