A
de Laval nozzle (or
convergent-divergent nozzle,
CD nozzle or
con-di nozzle) is a tube that is pinched in the middle, making a carefully balanced, asymmetric
hourglass shape. It is used to accelerate a hot, pressurized
gas passing through it to a higher speed in the axial (thrust) direction, by converting the heat energy of the flow into
kinetic energy. Because of this, the
nozzle is widely used in some types of
steam turbines and
rocket engine nozzles. It also sees use in supersonic
jet engines.