I am wondering if combining a centrifugal blower impeller with an Archimedes screw impeller would create a hybrid impeller that would create enough thrust to lift up a VTOL aircraft.

Please reference the drawing below.

The drawing is showing a cross-sectional view of a centrifugal blower impeller located at the top with an Archimedes screw impeller inside of the pipe which extends down from the centrifugal blower impeller. The blades of the Archimedes screw impeller would be welded to the pipe so there will be no gap between the blades and the pipe.

This hybrid impeller would rotate so that the Archimedes screw blades would be trying to push air downward towards the opening of the pipe, yet air will not flow in this direction because the centrifugal blower impeller is pulling air upwards towards itself. I believe that the air friction and pressure against the blades from the fast moving air flowing upwards should create enough lift to lift up a VTOL aircraft. I think carbon fiber would be the ideal material to use to build this hybrid impeller.

Would this hybrid impeller design create enough thrust for a VTOL aircraft?



Perhaps replacing the Archimedes screw impeller with an axial multi-wing type impeller would be a better design? Less weight and more thrust/lift?

Its rotation direction would be the same as with the Archimedes screw impeller, in which its blades are trying to push air downwards while air is flowing upwards due to the suction of the centrifugal blower impeller.

enter image description here

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    $\begingroup$ Your 'blades' are generating a force against an airflow that the device is itself generating. I don't see where the net thrust required for take-off is coming from. That said, if this device works at all then almost anything will fly if you give it enough power. That may be your real problem. $\endgroup$ Feb 13 '19 at 4:02

This is a terrible idea. You've got a centrifugal blower pulling air up, and at the same time a second impeller or fan pushing that same air down.

This creates a low-pressure area between the two impellers, and little airflow at either end.

A VTOL aircraft has to push the air down with as little disturbance (friction losses etc) as possible. This is usually done with a large fan (helicopter blades, the F-35 VTOL fan), or an entire jet engine (by aiming its thrust downwards).

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    $\begingroup$ Air flowing UP does not generate lift and is the opposite of what you want. $\endgroup$
    – Hobbes
    Feb 16 '19 at 15:45
  • $\begingroup$ in case you are wondering I just deleted the last post. I agree with you on the main points you just made, so I think this can be put to rest. $\endgroup$
    – user36220
    Feb 16 '19 at 15:47

Right idea, wrong design. What you have here is an extruder, which works very well for making spaghetti. Would work for liquids too. But note small radius of impeller. This is for power, not speed.

Open it up a bit, moving through boat propeller, up to fan, actually found in VTOL aircraft. That is what you want for air.

  • $\begingroup$ @ Robert DiGiovanni, can you tell me the name/model of one or two VTOL aircrafts that use an impeller like this one? I would like to study those designs. $\endgroup$
    – user36220
    Feb 13 '19 at 12:33
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    $\begingroup$ Well, for VTOL we have helicopter, Harrier, and F35. You may start to get a handle on what is needed to generate velocity and volume of air to make thrust. Also look at the Nene jet, which did use a centrifugal compressor. $\endgroup$ Feb 13 '19 at 15:47
  • $\begingroup$ @ Robert DiGiovanni, thanks, I will take a look at those. $\endgroup$
    – user36220
    Feb 13 '19 at 23:19
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    $\begingroup$ My first thought opun googling the Nene was "that looks an awful lot like a Goblin". Sure enough: en.wikipedia.org/wiki/De_Havilland_Goblin Those early brit designs were all along the same line of thought. $\endgroup$ Feb 16 '19 at 14:00
  • $\begingroup$ Nice. This from Pasta plant engineer and boat guy with a USAF background. The very first marine propellers looked like the screw pictured. Then one day 2/3 broke off and the boat started to go faster. So they kept cutting off pieces until it didn't go any faster and that's where the boat propeller came from. $\endgroup$
    – Phil Sweet
    Aug 4 '19 at 17:24

The impeller itself provides thrust at the outside rim, provided it can draw up enough air through its centre. So the two major factors would be:

  • Channel the output air in the right direction.
  • Provide an inflow channel with as little inflow obstructions as possible.

As @Hobbes states, it makes no sense to try to deflect air from the impeller inlet.


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