Mechanical Engineering - Steam Nozzles and Turbines - Discussion

Convergent as name implies decrease in size mainly by cross section So, Answer is B. This shape is mainly used to decrease pressure and conversely increasing velocity.

I disagree with a @Salman statement because decrease in cross section will increases the pressure and velocity also increases.

When area increase than pressure decrease.

When area decreases pressure will decreases, then fluid velocity become increses.

When area decrease pressure will also decrease, but velocity will increase.

When exit area of nozzle decrease then velocity energy increase.

Nozzles are 3 types:

1) Convergent type.
2) Divergent type.
3) Convergent-Divergent type.

Because its cross section area of tube gradually decreases from entrance to the throat. Venturimeter is a good example of convergent nozzle.

The pressure drops in a convergent nozzle because of the Bernoulli Principle.

A nozzle is a spout on the end of a hose or pipe used to control the movement of a fluid like water or air. A convergent nozzle is a nozzle that starts big and gets smaller-a decrease in cross-sectional area. As a fluid enters the smaller cross-section, it has to speed up due to the conservation of mass. To maintain a constant amount of fluid moving through the restricted portion of the nozzle, the fluid must move faster.

The energy to make this fluid speed up has to come from somewhere. Some energy is in the random motion of molecules, which we observe as pressure. The energy in this random motion is converted into faster forward motion, known as stream flow. This change makes the pressure drop.

Pressure is inversely proportional to area, if everything else stays the same. In this case, the energy that causes pressure is converted to another type of energy, so both pressure and area decrease.

Convergence means gradually decrease area of flow line. That means answer should be B.