This article was automatically translated from the original Turkish version.
In a jet or rocket engine, this is the section where the velocity or direction of the expelled jet flow is altered. Propulsive nozzles do not add external energy to increase the fluid’s velocity; instead, they convert the fluid’s internal energy into kinetic energy. The primary purpose of propulsive nozzles is to accelerate the flow exiting the engine core, thereby increasing its momentum and thrust.
There are essentially two types:
Convergent nozzle is a type of nozzle with a decreasing cross-sectional area. As the cross-sectional area decreases along the nozzle, the fluid’s velocity increases in accordance with the principle of conservation of mass; its pressure, density, and temperature decrease. Convergent nozzles can accelerate the fluid to a maximum theoretical speed of Mach 1.
Convergent-divergent nozzle is a type of nozzle with a cross-sectional area that first decreases and then increases, used to accelerate the fluid beyond local sonic speed. When the back pressure is sufficiently reduced, the sudden increase in cross-sectional area allows the fluid to expand abruptly and become supersonic after the throat. In practice, it is preferred for the flow expelled from the engine to be supersonic to enable aircraft or rockets to achieve supersonic speeds; otherwise, significantly more fuel would be required.
