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LAN_403

Electroholic

Thu Jul 09 2009, 06:44PM

Registered Member #191 Joined: Fri Feb 17 2006, 02:01AM
Location: Esbjerg Denmark
Posts: 720

Maybe you need to look into the difference between gauge pressure and absolute pressure?

Chris Cristini

Fri Jul 10 2009, 02:29AM

Registered Member #1749 Joined: Fri Oct 10 2008, 02:04AM
Location: Claremont New Hampshire
Posts: 497

Gauge Pressure (in units of psig, the g refers to â€œgaugeâ€) measures the pressure above atmospheric, so a gauge pressure reading at atmospheric conditions will read zero. Boost gauges measure the manifold pressure relative to atmospheric pressure, and thus are measuring Gauge Pressure. This is important when determining P2c. For example, a reading of 12 psig on a boost gauge means that the air pressure in the manifold is 12 psi above atmospheric pressure. For a day at standard atmospheric conditions,

It is important to use units of Absolute Pressure for both P1c and P2c. Remember that Absolute Pressure at sea level is 14.7 psia (in units of psia, the a refers to â€œabsoluteâ€). This is referred to as standard atmospheric pressure at standard conditions. Right?

In any case this project is a weird one but I am going to experiment with it (may be waisting alot of time) but what the heck who knows I might find something out that can improve a real Turbo/Supercharger I am working with Semiconductors and the PCM/ECU for control. Did you guys know that if you take a motor with ferrite magnets and take one out it rotates alot faster but heats up like crazy?

I will work on a diagram for you guys to see how you like it.

I will make the lights dim when I am done.

Here it is.

[Edit: Read this:

Double posting makes moderators grumpy...]

klugesmith

Fri Jul 10 2009, 07:03PM

Registered Member #2099 Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716

Chris Cramer wrote ...

Hear is a small update I under stand that what I am trying to do is not a turbo but a supercharger and if I could some how make a motor like this

,000%2Brpm%26hl%3Den%26safe%3Doff%26sa%3DG%26um% 3D1 and this

it would come together and I understand that it would not be verry efficient and if atmospheric pressures at sea level are 14PSI it would have to produce 21PSI to get 7 pounds of boost all in all it would be a pain to build and test.

Here's another sanity check, supporting what others have said about supercharger power requirement.

You pointed us to a Dyson vacuum cleaner, with 100000 RPM switched-reluctance (or rare-earth magnet) motor & impeller, which claims a respectable 400 air watts. Probably about 60 cfm at 2 psi (28 l/s x 14 kPa). [edit] How convenient: liters/second * kilopascals = watts.

Now a modest 2 liter engine at 4200 RPM displaces 148 cfm (70 l/s). The Dyson vac, running full blast, would probably impede rather than enhance the mass flow of air.

For 7 psi of boost (48 kPa) you need about 3400 air watts. If the blower were 80% efficient, shaft power (motor output power) would need to be 4.2 kW = 5.6 HP. For example, go find yourself a 90% efficient motor at 12 V * 390 amperes.

There are commercial bolt-on electric "superchargers" like

but IMHO they are pretty lame, just one class above HHO gas generators.

Chris Cristini

Fri Jul 10 2009, 08:32PM

Registered Member #1749 Joined: Fri Oct 10 2008, 02:04AM
Location: Claremont New Hampshire
Posts: 497

But I am not using a blower I am using a Compressor and its housing from a real TD04 it is not just going to improve air flow it is going to compress it aswell and like I said it will not be verry efficient it is just an experiment that will not cost me anything besides time. Sorry if you feel I am arguing with you. It is just I have done it before with a drill motor that only rotated at about 22.000RPM and the pressure was alot better than those fans they call superchargers it did not use to much power I could even cover the output and I could feel the pressure build up it would launch full cans of soda to the ceiling one broke open. If you would like I will build it again the same way as befor and get a video of it I think it was impressive and a large improvement over those plastic looking fan things.

klugesmith

Fri Jul 10 2009, 09:24PM

Registered Member #2099 Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716

Chris Cramer wrote ...

It is just I have done it before with a drill motor that only rotated at about 22.000RPM and the pressure was alot better

Chris, here's one more point that might be relevant to your experiments.

For a given RPM, the torque required to turn impeller depends strongly on the air flow conditions.
1. Full load occurs with normal flow and back pressure (in supercharger application).
2. Load is smaller when turning at same RPM in open air (max flow, no back pressure).
3. Load is much smaller with outlet blocked (maximum pressure, flow = 0).
4. Load is a bit smaller than that, with inlet blocked (lower density of air idly spinning in circles).

3 and 4 are why you can hear vacuum cleaners speed up when inlet or outlet is blocked.

Electroholic

Fri Jul 10 2009, 11:16PM

Registered Member #191 Joined: Fri Feb 17 2006, 02:01AM
Location: Esbjerg Denmark
Posts: 720

It just seems like such a waste of time and energy from a thermal dynamic point of view.

Chris Cristini

Sat Jul 11 2009, 02:48PM

Registered Member #1749 Joined: Fri Oct 10 2008, 02:04AM
Location: Claremont New Hampshire
Posts: 497

Ok I will research more and see how fast the compressor wheel has to rotate before it produces positive boost instead of shooting for the sky. If I could just get positive boost it would actually be the first electric supercharger.

Ok I was wrong about how fast the TD04 rotates the max compressor speed of the turbo I am working with is only 118.000RPM at its highest efficiency and that is about 19 pounds of boost. I can lower the compressor speed way down to about 50 to 60.000RPM and have positive results that is alot more realistic unless I want 20 pounds of boost which is a little too much for a stock naturally aspirated engine any way I think it is recommended not to go over 7PSI for alot of engines.

Renesis

Sat Jul 11 2009, 10:38PM

Registered Member #2028 Joined: Mon Mar 16 2009, 08:13PM
Location: Norway
Posts: 319

Good luck with your project Chris. And may the laws of physics be with you.

A turbocharger with a large diameter works at lower speeds than the smaller ones. These would be easier to drive, as motors and gears designed for speeds up to 100.000rpm are hard to come by. Sadly (for you at least) turbochargers are designed to be as small as possible, and the bigger ones are ment for trucks, trains, ships and such. Needless to say, these are way to big for your project. Driving a truck turbocharger electrically would most likely need tens of kilowatts. There could also be issues with the hydraulic bearings in modern turbochargers, because they cannot withstand any radial or axial load.

So, 95% of all turbochargers are higly impractical for your project. If i were you, i would base my design on a centrifugal or impeller style supercharger instead. They usually have an internal gearbox, and are designed to be driven by a belt connected to the engines crankshaft, witch rotates at speeds ideal for electric motors.

Centrifugal supercharger:

Ok I was wrong about how fast the TD04 rotates the max compressor speed of the turbo I am working with is only 118.000RPM at its highest efficiency and that is about 19 pounds of boost. I can lower the compressor speed way down to about 50 to 60.000RPM and have positive results that is alot more realistic unless I want 20 pounds of boost which is a little too much for a stock naturally aspirated engine any way I think it is recommended not to go over 7PSI for alot of engines.

Its not this simple. How fast the turbo/super/whatevercharger must rotate to obtain the correct pressure depends highly on how much air the engine consumes, witch in turn depends on the engines speed and displacement.

You could use a pressure sensor and some circuitry that increase and reduce the motors speed based on the manifold pressure. This would effectively work as a wastegate.

Cheers

Chris Cristini

Sun Jul 12 2009, 02:24AM

Registered Member #1749 Joined: Fri Oct 10 2008, 02:04AM
Location: Claremont New Hampshire
Posts: 497

I know Renesis I am just to thick headed to just let it go.

I found some bearings here

that are the perfect size to replace the float ones they are just a little bigger.

Can you use planetary gears to increase speed?

Renesis

Sun Jul 12 2009, 09:24PM

Registered Member #2028 Joined: Mon Mar 16 2009, 08:13PM
Location: Norway
Posts: 319

Can you use planetary gears to increase speed?

Planetary gears would be ideal for your purpose, but good luck finding any

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