Hello all;
 I need a contraption, or configuration of contraptions that can
convert high flow (CFM) air into much higher pressure (albeit much
lower flow). I need to take the airflow that would be similar of that
which comes off of the blow-side of a typical shop vac, and create
about 100 psi.  The air coming off the blow side of the vac travels at
roughly 200 MPH, but is fairly low pressure. I am envisioning parhaps
a turbine that gets spun by the fast air, which in turn turns another
turbine that comnpresses air to the much higher air pressure.  I do
not wish to get something that that compresses air from some other
power source (i.e.: the air turns a generator which in turn operates a
traditional compresor..). I need it to be a simple mechanical
construction, involving no electricity. The power inherent in the fast
moving air should be the power source.  To put it another way.. I want
to take the airflow and multiply it's pressure many many times, but
reduce it's flow/speed.
Thanks!!

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Request for Question Clarification by hedgie-ga on 23 Sep 2002 15:42 PDT

Hi puravida..
                It may help if you elaborate a purpose.

 It is possible in principle, using the same method 
as voltage converters:
http://www.teamdelta.com/roboglad/vconv.htm

but unpractical for most purposes due to the low inertia of gas ..

So, is this something you really would want to build?

Hedgie

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Clarification of Question by puravida77-ga on 23 Sep 2002 16:18 PDT

Thanks for responding Hedgie; 
Yes, this is something I want to build (or buy). I want to take the
air flowing off of a shop vac (big roll-around wet/dry 10 gallon home
depot-style shop vac) and convert the super high flow outflow (about a
3"  diameter tube), and convert it into high pressure air (suitable
for charging up a high pressure tank, or very low flow air tool). I am
assuming somehow you can take (and I am making these numbers up, but
you get the point) 2,000 CFM of 5 psi air and convert it into 50 cfm
air at 200 psi (of course I am also assuming this is idea-- there
would be a loss of some kind.. So maybe 50 cfm air at 100 psi (50%
loss)

Hi puravida77,

You are seeking a device that is driven by a high airflow at low
pressure, and produces a low airflow at higher pressure.

Such devices are made by Sprague, where they are known as "gas
boosters" and "air amplifiers". Sprague is a division of
Curtiss-Wright Flow Control Corporation.

   Sprague Products
   10195 Brecksville Rd
   Brecksville, Ohio 44141
   http://www.cwfc.com/sprague/sprague.html
   Phone 800-327-1610

The devices are described here:

Curtiss-Wright Flow Control - Products
http://www.cwfc.com/sprague/s_gas.htm

Sprague Air Amplifiers
http://www.cwfc.com/sprague/air.html

Technical data is available here (requires PDF reader):

Sprague Advanced Air Driven Gas Boosters And Amplifiers
http://www.cwfc.com/sprague/pdf/Psaa.pdf

From the Sprague literature:

"Supercharge shop air or bottled gas with Sprague Products gas booster
... Being air-driven and having no electrical connections, Sprague
Products pneumatic boosters are non-sparking ... A variety of Sprague
Products boosters have been developed to convert precharge low gas
pressures to higher gas pressures."

"The Sprague Products booster, like Sprague Product air-driven
hydraulic pumps, employ the piston differential areas principle - a
large area air piston, driven at low air pressure to drive a small
area compression piston which converts input gas to higher pressure,
lower volume output gas."

"The PowerStar air amplifier design offers greater efficiency and is
modular for increased versatility. It provides higher output pressure
without expensive modifications to existing compressed air systems.
The PowerStar air amplifier supplies up to 500 psi (35 bar) and flows
to eight SCFM (226 liters N/min). The PowerStar is easy to install,
without need of electrical or mechanical drive. Non-lubricated with no
external muffler, it requires minimal maintenance."

The standard range of Sprague products can work from an input pressure
of 25psi. That's 1.7 times normal air pressure. I don't know the specs
of your blower, but you would need to check that it can generate that
pressure (when its air outlet is connected to a load) and that the
back pressure will not overload your blower motor.

Additional Links:

Hydratron air operated gas booster pumps
http://www.hydratron.co.uk/media/html/gas_pumps.htm

SMC Pneumatics Air Booster Regulators
http://www.flo-products.com/floprod/boosterp.html

SC Hydraulic Engineering Corp - Air Boosters
http://www.schydraulic.com/airboosters.htm

SC Hydraulic Engineering Corp - Gas Boosters
http://www.schydraulic.com/gasboosters.htm


Google search strategy:

"high volume low pressure" "low volume high pressure"
://www.google.com/search?q=%22high+volume+low+pressure%22+%22low+volume+high+pressure%22

ram "high pressure" air flow
://www.google.com/search?q=ram+%22high+pressure%22+air+flow

"air ram" OR "ram air"
://www.google.com/search?q=%22air%20ram%22%20OR%20%22ram%20air%22

"pneumatic ram" "high pressure" "low pressure"
://www.google.com/search?q=%22pneumatic+ram%22+%22high+pressure%22+%22low+pressure%22

turbo "low pressure" "high pressure" air volume
://www.google.com/search?q=turbo+%22low+pressure%22+%22high+pressure%22+air+volume

converts "high pressure" "low pressure" volume OR flow air
://www.google.com/search?q=converts+%22high+pressure%22+%22low+pressure%22+volume+OR+flow+air

"gas booster" OR "air pump" convert
://www.google.com/search?q=%22gas+booster%22+OR+%22air+pump%22+convert

"air operated booster"
://www.google.com/search?q=%22air+operated+booster%22


Regards,
eiffel-ga

good job!

I am not an expert in this area of Physics but don't you just have to
change the cross-sectional area of the "pipe" that the air is flowing
in. Just like squeezing the end of a water hose enables you to change
the pressure/flow characteristics of the water jet? Am I
misunderstanding the question?

I think your assertion is corect about increasing pressure that way.
However, I don't think that that technique could be used to raise the
pressure that dramatically  (say from 2 to 100 psi).  If it can-- I am
not sure how efficeint it would be. For example if it can-- perhaps
another method would be more efficient ( as in able to get the higher
pressure and a decent flow/cfm to boot).

Yeah - changing the diameter of the pipe works for non-comressible
flow; like water.  Air has this nasty problem of compressing before it
gets to the level you want, which would cause the vaccuum motor to
work overtime.  Eventually, the motor would not be able to pump more
air into the pipe.

For all the time and expense and hassle of building a multi-stage
turbine / gear driven device to run a mechanical pump, just buy a $20
air pump from a discount house.  :-)