Nozzle for the projection on to an object of a fluid such as a gaseous flow containing solid particles, comprising a body through which there passes a longitudinal tubular passage, one end of which constitutes an inlet that has to be connected to the intake of a fluid supply conduit and the other end of which constitutes an outlet for the fluid that has passed through the nozzle, wherein the section of the tubular passage is variable between the inlet and the outlet (3), and said passage has three successive portions, which are:
- an inlet chamber with a constant section,
- an intermediate conduit with a variable section, the walls of which are convergent from the chamber to an oblong neck, which has a major axis and a minor axis and the area of which is equal to that of the circular section of the chamber, and
- an outlet tube with a variable oblong section, the walls of which are divergent from the neck to an outlet orifice of oblong section having a major axis and a minor axis.