Nozzle

A nozzle in which combustion of gaseous fuel is to take place, said nozzle comprising a truncated hollow pyramidal shroud part and an interiorly coaxially mounted restrictor part, the shroud at its smaller end adapted to be coupled to a supply of pressurized gaseous fuel, said restrictor being generally pyramidal in shape with the apex of the pyramid directed toward the smaller end of said shroud and the base of the pyramid directed toward the other end of the shroud, the shape of the base of the pyramid and the internal cross-sectional shape of the shroud being similar with a gap between the perimeter of the pyramid base and the adjacent interior surface of the shroud through which a generally tubular stream of gaseous fuel passes, the linear value of gap D being based on the use of fixed design criteria for the nozzle and calculated by the formula

• D = ALF/V.sub.o
• where A is the area of gap of linear width D, L is the length of travel of the gaseous fuel in the nozzle from the point of ignition of the innermost layer of gaseous fuel in the stream to the point where the outermost layer of gaseous fuel ignites, F is the speed of flame propagation and V.sub.o is the volume of gaseous fuel per unit time passing through A.