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Possible substitutes for conventional turbo / superchargers

I know there have been electrically powered pseudo-superchargers for cars before that did not work, but then they were essentially cheaply constructed devices, not made to work at truly high pressure. There is a device called a turbo-molecular air pump. These devices are about 4" wide and 8 inches long. They spin a 3" impeller at around

70,000 rpm. They cost around $5000 but can be had used for about $500. They are used in the mass-spectrometer and highvac industry. They do not require water cooling or constant lubrication. I'm wondering if they could produce enough pressure to act as a mild "turbo" or supercharger? They are designed to produce a vaccuum, but their exhaust is where the air pressure would come from. Power consumption is low, a few watts. They rate them as to the vaccuum they produce and not the air output velocity so I'm not sure how they compare to a conventional automotive charger. Some kind of intercooler might be needed however as these things generate a lot of heat due to the compression of the air.
Reply to
Richard
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and they run on 12v ?

or is a "Generac " in the trunk the plan... :)

Reply to
chief_wiggum

Richard opined

Your physics doesnt add up.

No way they could do enough work to generate any amount of "heat" if they only consume a few watts. And the heat of compression is exactly the same as that of a turbo or SC at the same pressure/flow... doesnt matter WHAT compresses it, it's that it's compressed. The converse is true too... how can it compress at all if it only consumes a few watts.

BUT I think you'll find the answer by playing with your tank type shop vac.

Cover the hose inlet with your hand. What happens?

Now borrow an AC current meter and check the current when you're covering it.

You'll see that the current goes down... because the motor isnt moving air, thus doing less work.

And the equivalent is using a high-vacuum pump as an air compressor. It will compress air but not efficiently or as practically.

Reply to
Backyard Mechanic

I am not a physics major, nor do I remember ever even taking a physics class. However, these are things that come to mind. This isn't a shot... people that think outside the box are the reason we have all of the neat toys that we have today.

  1. While the turbine spins at 70,000 RPM under no-load output conditions, simply drawing air in and placing it into the open air, I'd imagine that it would have a hard time keeping up if it was forced to compress the air. The turbine speed would most likely slow down greatly and cause the motor driving the unit to overheat.

  1. Are you sure the heat is caused by the air compression and not just because of the motor turning? If it's creating a vacuum... there is no real air compression. If anything, it's expanding on the input side. Again, I'm assuming that the output is vented into the open air.

  2. Compressing the air is harder to do than exhausting it. It only uses a few watts exhasting the air and creating a vacuum, it would likely use more trying to push air into an engine. Use an empty plastic Coke bottle and try to suck all of the air out of it with your mouth. Pretty easy. Now take that same bottle, blow it back up to its original shape, and then try to put twice as much air in that bottle with your mouth. Much harder to do.

  1. It costs power to drive a supercharger on a car, but that power is more than made up for by the additional air and fuel the engine takes in. A centrifugal blower takes, lets say 50hp to drive. That 50hp has to come from somewhere. Maybe it can be made more efficient, but let's say at 100% efficiency, it was 35hp. You'd have to be pulling that power, in electrical energy, out of the alternator to get the same output out of your electrical blower, or at least close to it. I don't remember what the HP->W conversion is, but I bet it's more than a couple to drive 9psi.

Before dropping $500, even on a used one, I'd try to contact the manufacturer and see what the output rating is and what pressure it could sustain if needed to be used as an air compressor of sorts. Unless you have lots of money and want to try to do it and see how it works.

JS

Reply to
JS

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