A propelling nozzle is a nozzle that converts the internal energy of a working gas into propulsive force; it is the nozzle, which forms a jet, that separates a gas turbine, being gas generator, from a jet engine.
Propelling nozzles accelerate the available gas to subsonic, transonic, or supersonic velocities depending on the power setting of the engine, their internal shape and the pressures at entry to, and exit from, the nozzle.
Testing a variable nozzle, to check function.Still some screws missing, but ordered!Its made of stainless steel, 12 springs, 24 rod ends and about 100 screws, washers and nuts. Calculated THRUST: 600 N at 70 000 Rpm.Diameter: 200 mm.Length: 450 mm.Weight: 11 Kg.
Nozzles for supersonic flight speeds, at which high nozzle pressure ratios are generated, also have variable area divergent sections. Turbofan engines may have an additional and separate propelling nozzle which further accelerates the bypass air.Propelling nozzles also act as downstream restrictors, the consequences of which constitute an important aspect of engine design.