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Written by MK
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Monday, 08 September 2008 21:00 |
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An important part of a Rocket Engine is the nozzle, because from overall power of an engine, 80% come from the thrust chamber and 20% from the nozzle.
Because of the converging-diverging form of the nozzle, the subsonic flow from the thrust chamber is being accelerated in the converging part and reaches sonic velocity in the throat. If you want to accelerate the flow more you need a diverging contour, to get supersonic velocity.
The most widely used forms of nozzles are:
- The simplest contour is the conical nozzle, also called Laval-nozzle ( invented by Carl Gustav Patrik de Laval ). It consists from a converging-diverging contour, with constant gradient. These nozzles are easy to manufacture, but are not used very often because of their low efficiency.
- Ideal nozzles create a uniform, parallel flow at the exit to achieve a high thrust. The ideal contour is calculated with a method of characteristics. Because of the low gradient of the contour at the end, you can shorten the nozzle to save weight. Thats what is called a ( TIC - Truncated Ideal Contour ).
- At todays Rocket engines ( Vulcain II, Space Shuttle Main Engine ) so called Thrust Optimized Contours ( TOC ) are being used. These contours are calculated with a method of characteristics and a variational calculation, to get the maximum thrust. The so calculated contour can be described with a parabola, so called parabolic nozzles.
For HyEnD a Thrust optimized parabolic nozzle has been calculated in cooperation with the German Aerospace Research Center, Institute for Space Propulsion, Lampoldshausen. The advantage of that design in comparison with a Laval-nozzle is a higher efficiency and only 80% of the length, and therefore less weight. You can see the different nozzle contours in the following diagram.
A good overview about the function and design of supersonic nozzles can also be found here:
http://www.pwrengineering.com/articles/nozzledesign.htm
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Last Updated on Tuesday, 04 August 2009 15:01 |
Nozzle