Mechanical Engineering - Steam Nozzles and Turbines - Discussion

Most of the frictional loses occurs between the throat and exit because both the length as well as velocity is higher.

I not clear but during convergence and divergence the reaction b/w the fluid and nozzle is higher so they must be considered.

Because between to throat and exit in high pressure than low velocity.

How's that possible because first in convergent part friction should more and then it should less.

Because at throat and exit the shape of nozzle changes. Therefore it resists.

Friction losses occur b/w throat and exit because in this section velocity will increase.

Yeah, flow at the inlet is at very high speed so frictional losses can be neglected and also the frictional losses depend upon the Mach no.

As there is contact between steam and nozzle surface through out the length nozzle there is friction loss from inlet to outlet.

Basically, the velocity is high and the length of the divergent portion is more than (3-4 times longer) convergent side.

At the inlet i.e. the convergent portion of the nozzle, the stem velocity is very low (subsonic) as compared to the other 2 sections i.e throat (sonic) and a divergent portion (supersonic).

This continuous increase in velocity is obtained by-.

1) due to convergence of the nozzle diameter at the convergent section (inlet to throat) -subsonic to sonic.

2) due to the divergence of the nozzle diameter after the throat- the pressure tries to increase, but the pressure rise is overthrown by the friction between the walls of the nozzle and steam. Thus the velocity of the steam increases. From sonic to supersonic.

Hence the right answer will be the "throat and exit".