Thread: Cascade ducting
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Old 06-14-2014, 10:54 AM   #1
quorneng
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Default Cascade ducting

The Harrier/AV8 uses cascade 'vectoring' nozzles.
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Whilst I have no intention (at this stage!) to build a VTOL plane I wondered if it would be possible to use this principle to have multiple nozzles on a single EDF but built very light (in Depron?) to keep to a 'scale' size.
First a 'test' duct to work out the best way to actually make it. For simplicity the ducting is square with a double cascade. Each cascade vane is made of 0.015" litho plate.
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Two cascade units joined together to form a twin nozzle.
The inlet side.
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The outlets.
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The complete duct unit weighs just 0.2oz (5.9g)
Coupled to my 'spare' 55mm EDF on a thrust test rig the object is find out what, if anything, actually happens.
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A run up on a 3s.
YouTube Video
ERROR: If you can see this, then YouTube is down or you don't have Flash installed.

It generate 9.1oz thrust drawing 20A
On the same rig with the complete nozzle assembly removed the fan generate 18oz thrust.
Although this result appears rather disappointing the total area of the nozzles is only 54% of the FSA so some reduction in static thrust would be expected.

The next step is to build a four nozzle test duct with a combined nozzle area equal to the FSA.


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