What is convergent and divergent nozzle?

What is convergent and divergent nozzle?

Convergent-divergent nozzle. An arrangement in which the forward portion of the nozzle is convergent, which increases the pressure of the exhaust gases, while the aft section is divergent to increase gas velocity to the supersonic speed and avoid losses from underexpansion.

What is the difference between convergent nozzle and divergent nozzle?

Convergent nozzles accelerate subsonic fluids. If the nozzle pressure ratio is high enough, then the flow will reach sonic velocity at the narrowest point (i.e. the nozzle throat). Divergent nozzles slow fluids if the flow is subsonic, but they accelerate sonic or supersonic fluids.

Why do we use convergent-divergent nozzle?

Convergent-divergent type of nozzles are mostly used for supersonic flows because it is impossible to create supersonic flows (mach number more than one) in convergent type of nozzle and therefore it restricts us to a limited amount of mass flow through a particular nozzle.

What happens in convergent-divergent nozzle?

This nozzle configuration is called a convergent-divergent, or CD, nozzle. In a CD nozzle, the hot exhaust leaves the combustion chamber and converges down to the minimum area, or throat, of the nozzle. The exit velocity, pressure, and mass flow through the nozzle determines the amount of thrust produced by the nozzle.

Why turbine nozzles are made divergent after the throat?

At throat, velocity is equal to sonic velocity. The divergent portion acts as a super-sonic nozzle with a continuous decrease in pressure and continuous increase in velocity.

What is a divergent nozzle?

[də′vər·jənt ′näz·əl] (design engineering) A nozzle whose cross section becomes larger in the direction of flow.

Can the flow inside a nozzle be steady and uniform?

Can the flow inside a nozzle be steady and uniform? It can be a steady flow if and only if the water level is maintained at a constant level by supplying water at the same rate as it gets discharged, else the water level will keep decreasing with time leading to an unsteady flow.

What is normal shock in nozzle?

The flow in the entire divergent portion up to the exit plane is now supersonic. When the back pressure is reduced even further (v), there is no normal shock anywhere within the nozzle, and the jet pressure adjusts to PB by means of oblique shock waves outside the exit plane.

What are real life examples of nozzles?

2. Some Applications of a Nozzle:

  • Nozzles are used in steam turbines, gas turbines, water turbines and in jet engines, Jet propulsion.
  • Nozzles are used for flow measurement e.g. in venturimeter.
  • Nozzles are used to remove air from a condenser.
  • Injectors for pumping feed water to boilers.
  • Artificial fountains.

Why is the Mach number 1 at the throat?

When the nozzle isn’t choked, the flow through it is entirely subsonic and, if you lower the back pressure a little, the flow goes faster and the flow rate increases. As you lower the back pressure further the flow speed at the throat eventually reaches the speed of sound (Mach 1).

How do divergent nozzles increase velocity?

In a steady internal flow (like a nozzle) the Mach number can only reach 1 at a minimum in the cross-sectional area. The flow then decelerates through the diverging section and exhausts into the ambient as a subsonic jet. Lowering the back pressure in this state increases the flow speed everywhere in the nozzle.

Can the flow inside a nozzle be?

For a nozzle, the area gradually decreases towards it’s exit. Thus, no matter what the rate of flow is, the velocity of flow at the nozzle exit will always be greater than that at it’s entrance. Hence, it’ll always be an unsteady flow.