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"Once the fan encounters pressurized air backing up towards it, it loses its effectiveness and stops pumping air."
By this reasoning, you seem to imply that, if you take your old bicycle pump, plug the hose, push as hard as you can, till the piston stops, you are not making pressure, because no air is moving, just "choking" the piston.
No, I don't think you mean that.
Where, except in the rebuts to the OP, did we start to discuss axial flow fans?
I think most of the posters know ( I hope they do, anyway ) that leaf blowers and vacuums are centrifugal, therefore, radial flow.
A turbocharger is a radial flow device.
A leaf blower is a radial flow device, as is any vacuum cleaner you can name, whether it be Shop Vac or Hoover, or Orek.
Radial flow COMPRESSORS have been built for a 100+ years.
Your shop Vac may not make the pressure you desire, due to limitations of speed, design of the impellor, clearances in the compressor, itself, but that does not mean it does not compress air.
Good grief, just try to squeeze the Hoover bag, after you turn it on!!!
And, that is from the COMPRESSOR trying to compress the air into a container (the filter bag and the containment vessel, the outer bag ) that are designed to let filtered air escape, so it can continue sweeping up more dust. It would work the same, for about 2 feet of travel, if you had a hose attached to a 100 gallon drum outside the house. Except, you would have to go outside, release the pressure, dump the dust, reseal it, then go inside and clean 2 more feet of the carpet.
I wrote elsewhere, that a well designed centrifugal, radial flow, compressor ( much stricter tolerances, and much higher rotational speeds ) will double the input pressure. ie, atmospheric, after 1 stage, 30 PSI, 2 stages, 60 PSI, 3 stages, 120 PSI, up to as many stages as you need.
One company I worked at built centrifugal compressors that produced 10,000 PSI, for use in floating oil rigs, drilling deep. That will push oil up a 25,000 foot oil well casing.
Fans and centrifugal compressors, if you want to call a leaf blower or a shop vac OR a supercharger, such, DO NOT choke when the flow is restricted. They MAINTAIN the pressure. So long as the air can't escape elsewhere, the pressure is held. Lift your hand a little bit, air comes out, instantly. It IS compressed.
Curtis,
"There is almost no pressure behind that wind, but it will rip a roof off a house."
It has been scientifically proven that 60 MPH winds do not blow roofs off houses. The vacuum caused by those winds cause a house to explode, due to the difference in pressure, inside to outside. Tornados, for instance, cause a low pressure area to develop over their path. Houses blow apart. Warnings in all tornado prone areas advise you to open your windows to allow pressure to equalize. Minimal damage results.
Even axial flow fans, like your typical 4 bladed air circulator,you know, that 10 buck thing that oscillates in your den, creates pressure. Put it up against the wall and turn it on. It can't move the wall, so it tries to knock itself over from the force.
They use axial flow air turbines, read really big powerful fans, in wind tunnels. Not supersized superchargers, ie, centrifugal compressors. These babies can blow some air. They can tear the skin off an improperly designed aircraft fuselage.
If any fluid dynamics savvy people are here, they could tell you what the potential pressures these devices would be capable of are.
1 mm Mercury differential means a hell of a lot more over a couple thousand square miles than in an engine manifold. It means cubic miles of air rushing in to fill that void. The amount of work, or of havoc, is stupendous.
Hypsi,
Correct. I have had this problem with hydraulic metal working machinery. Pumps putting out plenty of flow, but no work being done.
Bad pump, still moves the oil, but so much slip, due to bad vanes, the machine wouldn't run, change the pump, all's well.
Same with air, only easier to "stall" the "pump", after all, it's air. You get to the max pressure it is capable of, it just lies there in wait, you bleed off a little air, toe the throttle, take the piece of paper off the discharge hose, it recharges to the max pressure it is capable of.
Why this is so difficult to understand, I don't know. How can anyone say "No flow, no pressure."?
You take a 3" leaf blower wand, flatten the end to a 1x3 nozzle, you have a restriction, you have pressure, you have speed.
You stick it in your intake, without the nozzle, you have more air than an NA engine.
I give up,
Gotta go to bed.
Cheers,
George
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