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Which is the nozzle used for supersonic flow?
Divergent nozzles
Divergent nozzles are used to produce supersonic flow in missiles and launch vehicles.
Where is convergent nozzle used?
Few examples of the application of convergent divergent type of nozzles in engineering are: *Steam turbines : In power plants . *Rockets : for providing sufficient thrust to move upwards. *The supersonic gas turbine engine : for the air intake when air requirement of engine is high.
Why supersonic flow Cannot be achieved using a converging nozzle?
Expansion Ratio-The expansion ratio of the nozzle is the ratio of exit area to throat area. There is no pressure difference and thus no flow through nozzle. The flow remains subsonic through the nozzle.
Why convergent divergent nozzle is used in steam turbine?
To increase the velocity magnitude for momentum source in rotating power turbine, a compressible fluid e.g. steam could reach the supersonic flow through the convergent- divergent nozzle (CD-nozzle). A throat section, between inlet and outlet sections, controls the outlet Mach when velocity in sonic condition.
Why turbine nozzles are made divergent after the throat?
So the divergent section acts as a sub-sonic diffuser in which the pressure increases and velocity decreases. 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.
Why vacuum is maintained in condenser?
Now to ensure proper and continuous flow of steam to condensers at all times, vacuum must be maintained externally. A vacuum is maintained in the condenser so that steam can easily flow and more work can be extracted from the steam in the turbine; this is the reason why vacuum is maintained in condensers.
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.
Why is a divergent nozzle used in supersonic engines?
The flow in the throat is sonic which means the Mach number is equal to one in the throat. Downstream of the throat, the geometry diverges and the flow is isentropically expanded to a supersonic Mach number that depends on the area ratio of the exit to the throat.
What kind of nozzle is used in a ramjet?
A nozzle is a relatively simple device, just a specially shaped tube through which hot gases flow. Ramjets and rockets typically use a fixed convergent section followed by a fixed divergent section for the design of the nozzle. This nozzle configuration is called a convergent-divergent, or CD, nozzle.
Which is quieter a convergent or divergent nozzle?
The core flow exits the center nozzle while the fan flow exits the annular nozzle. Mixing of the two flows provides some thrust enhancement and these nozzles also tend to be quieter than convergent nozzles. Afterburning turbojets and turbofans require a variable geometry convergent-divergent – CD nozzle as shown on the left.
Why does a converging nozzle not produce thrust?
So if the converging section is too large and does not choke the flow in the throat, the exit velocity is very slow and doesn’t produce much thrust. On the other hand, if the converging section is small enough so that the flow chokes in the throat, then a slight increase in area causes the flow to go supersonic.