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The gas flow rate is constant (i.e., steady) during the period of the propellant burn. The gas flow is non-turbulent and axisymmetric from gas inlet to exhaust gas exit (i.e., along the nozzle's axis of symmetry). The flow is compressible as the fluid is a gas. As the combustion gas enters the rocket nozzle, it is traveling at subsonic velocities.
Grossly overexpanded nozzles have improved efficiency, but the exhaust jet is unstable. Conventional nozzles become progressively more underexpanded as they gain altitude. [1] The basic concept of any engine bell is to efficiently direct the flow of exhaust gases from the rocket engine into one direction.
This is referred as overexpanded flow because in this case the pressure at the nozzle exit is lower than that in the ambient (the back pressure)- i.e. the flow has been expanded by the nozzle too much. [13] A further lowering of the back pressure changes and weakens the wave pattern in the jet.
A supersonic flow that is turned while there is an increase in flow area is also isentropic. Since there is an increase in area, therefore we call this an isentropic expansion. If a supersonic flow is turned abruptly and the flow area decreases, the flow is irreversible due to the generation of shock waves.
The gas flow is constant (i.e., in steady state) during the period of the propellant burn. The gas flow is along a straight line from gas inlet to exhaust gas exit (i.e., along the nozzle's axis of symmetry) The gas flow behaviour is compressible since the flow is at very high velocities (Mach number > 0.3).
Fluid dynamics is a subdiscipline of fluid mechanics that deals with fluid flow—the science of liquids and gases in motion. [4] Fluid dynamics offers a systematic structure—which underlies these practical disciplines —that embraces empirical and semi-empirical laws derived from flow measurement and used to solve practical problems.
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In a properly designed engine, the flow will reach Mach 1 at the throat of the nozzle. At which point the speed of the flow increases. Beyond the throat of the nozzle, a bell shaped expansion part of the engine allows the gases that are expanding to push against that part of the rocket engine. Thus, the bell part of the nozzle gives additional ...