Plug nozzle
Encyclopedia
The plug nozzle is a type of nozzle
which includes a centerbody or plug around which the working fluid flows. Plug nozzles have applications in aircraft, rockets, and numerous other fluid flows.
s much like the aerospike
which, unlike traditional designs, maintains its efficiency at a wide range of altitudes.
The ideal contour of a plug nozzle is a long tapering 'spike' with a doughnut-shaped combustion chamber situated at the base, hence sometimes this nozzle is also called a "spike nozzle". To save weight, this design is shortened without a large drop in efficiency.
The exhaust is confined by atmospheric pressure so that at different altitudes the varying pressures will allow the exit area to change. This allows optimized atmospheric compensation. With the shortened (or truncated) nozzle, the recirculation of trapped gases at the base of the plug causes a small thrust which offsets the loss due to the non-ideal shape.
both because of the annular shape of the turbine exhaust and for their altitude compensating characteristics. For high speed aircraft, translating the plug or external cowl provides a means of area control with relatively simple actuation. Plug nozzles have been shown to provide noise reduction compared to traditional convergent-divergent nozzles. Weight and cooling are typical concerns with aircraft plug nozzles.
Nozzle
A nozzle is a device designed to control the direction or characteristics of a fluid flow as it exits an enclosed chamber or pipe via an orifice....
which includes a centerbody or plug around which the working fluid flows. Plug nozzles have applications in aircraft, rockets, and numerous other fluid flows.
In Rockets
Plug nozzles belong to a class of altitude compensating nozzleAltitude compensating nozzle
An altitude compensating nozzle is a class of rocket engine nozzles that are designed to operate efficiently across a wide range of altitudes.- Conventional designs :...
s much like the aerospike
Aerospike engine
The aerospike engine is a type of rocket engine that maintains its aerodynamic efficiency across a wide range of altitudes through the use of an aerospike nozzle. It is a member of the class of altitude compensating nozzle engines. A vehicle with an aerospike engine uses 25–30% less fuel at low...
which, unlike traditional designs, maintains its efficiency at a wide range of altitudes.
The ideal contour of a plug nozzle is a long tapering 'spike' with a doughnut-shaped combustion chamber situated at the base, hence sometimes this nozzle is also called a "spike nozzle". To save weight, this design is shortened without a large drop in efficiency.
The exhaust is confined by atmospheric pressure so that at different altitudes the varying pressures will allow the exit area to change. This allows optimized atmospheric compensation. With the shortened (or truncated) nozzle, the recirculation of trapped gases at the base of the plug causes a small thrust which offsets the loss due to the non-ideal shape.
In Aircraft
Plug nozzles are used in aircraft typically with jet enginesJet engine
A jet engine is a reaction engine that discharges a fast moving jet to generate thrust by jet propulsion and in accordance with Newton's laws of motion. This broad definition of jet engines includes turbojets, turbofans, rockets, ramjets, pulse jets...
both because of the annular shape of the turbine exhaust and for their altitude compensating characteristics. For high speed aircraft, translating the plug or external cowl provides a means of area control with relatively simple actuation. Plug nozzles have been shown to provide noise reduction compared to traditional convergent-divergent nozzles. Weight and cooling are typical concerns with aircraft plug nozzles.
Other Applications
Plug nozzles are used as water nozzles to create a broad spray. The plug can be translated to adjust the area of the passage and thereby adjust the flow rate.Further reading
- Aerospike Engine, Jeff Scott, Fall 1999. This paper gives an extensive review of the various altitude compensating nozzle designs.