Variable spread fluid dispersal systems

In a modification of the fluid dispersal system claimed in Specification No. 995,244 in which a first fluid and another fluid meet at a common boundary in a conduit immersed in a flow of a second fluid, means are provided to increase the ratio of the perimeter of the confined path within the conduit to the cross-sectional area of the confined path at points along the length of the conduit between the fluid entries so as to reduce the risk of the first and the other fluid mixing at the common boundary. The entry 4 of conduit 1 mounted in a duct wall 2, such as the casing of a ram jet or gas turbine jet propulsion engine reheat chamber, is supplied with liquid fuel through a metering device 15 comprising a movable obturator 18 and diaphragms 16, 19 with orifices 17, 20 respectively. A second entry 6 faces in the upstream direction and is subjected to the dynamic pressure of the air, combustion gases, or other fluid 3 flowing through duct 2. Alternatively, entry 6 may be connected to an engine compressor or other source of fluid. A ball 8 of plastic material at the interface between the fluids within conduit 1