How much power is needed to spin a radial compressor?

[Hondaen]

Hi :-)

I dont have the formulas to calculate how much energi that is needed in order to spin compressors from turbocharges.

I suspect it is in the area of several 10`s of kilowatts, for a normal size car turbo compressor.

I want to now the theoretical possibilities on how to make a electrical turbocharger for four stroke otto engines.

If I need a electrical engine that need 20kW in order to spin the kompressor, the system will be way to heavy.

I`m sure there must be a reason why system like this dont exist today.

"Turbocharges" that use a axial fan infront of the engine intake is available, but just a hoax in my eyes.

Thank you :)

[larry cottrill]

Hondaen -

I don't know much about this, and certainly don't know how to figure out the power requirement, but I DO know this: It has been done, back in the 1930s, and was apparently successful! I think the Cord was one auto that had an electric supercharger, and there were some others, too, I'm sure. I think it was only effective at fairly high engine speeds (RPM) for fast highway driving.

So, I would encourage you to try it. I know it's going to take a fair amount of power - but, at least you should have a LOT better electric motor technology available today than what they had in the 30s!

Good luck!

L Cottrill

[marksteamnz]

Nope
There has never been an electrically driven supercharger in the past. Cord used direct drive centifugal. There have been electrically clutched superchargers on production cars but thats a diffent animal. The problem is under full boost a supercharger can take about 10% of the engines horsepower so even at 5hp equals 3745 watts from a 12 volt battery equals 310 amps. Yowwza!!
So those turbo fan boosters on the web using 2 computer fans are a joke.
http://www.electricchargers.com/ or http://www.electricsupercharger.com/
Scamming bastards
I have seen one electric installation and it had a major set of batteries heavy cables and a grunty electric motor. It was do more as a because we can rather than a practical intallation.
Details here http://www.turbomagazine.com/tech/0406t ... ercharger/

Hondaen -

I don't know much about this, and certainly don't know how to figure out the power requirement, but I DO know this: It has been done, back in the 1930s, and was apparently successful! I think the Cord was one auto that had an electric supercharger, and there were some others, too, I'm sure. I think it was only effective at fairly high engine speeds (RPM) for fast highway driving.

So, I would encourage you to try it. I know it's going to take a fair amount of power - but, at least you should have a LOT better electric motor technology available today than what they had in the 30s!

Good luck!

L Cottrill

[jthompso]

"A model engine's single turbine wheel, just 65mm in diameter, can drive a compressor with a power absorption of more than 20kW at full throttle." That's from Thomas Kamps' Model Jet Engines

[larry cottrill]

Nope

Well, I said I didn't know much about it. All I remembered was an old guy saying that he would get the car up to speed, then flip a switch and it gave you a real kick in the pants when it locked in. Sounds like maybe an electric clutch version, and perhaps he never really understood how it was actually set up.

As usual, it is easy to underestimate the power needed for a "simple" air mover!

So once again, I gladly stand corrected.

L Cottrill

[Jim Berquist]

Exhaust gas and gear ratio is the way, 20 muffin fans in line would not compete with the vacuum from the engine. Most likely slow the flow! Choke the whole thing!!! You want a Turbo charger?????? KW ? thats not going to happen!


Jim

[Hondaen]

Exhaust gas and gear ratio is the way, 20 muffin fans in line would not compete with the vacuum from the engine. Most likely slow the flow! Choke the whole thing!!! You want a Turbo charger?????? KW ? thats not going to happen!


Jim

?

[HattoriHanzo]

Hi :-)

I dont have the formulas to calculate how much energi that is needed in order to spin compressors from turbocharges.

Hi Hondaen

I do not have a complete useful formula for that calculation but I have ideas of how you can approach this problem.

If you know the pressure before and the pressure after the centrifugal compressor and the area of every compressor blade, you might be able to calculate the total force on every blade and then sum it. Then approximate a slip factor, loss in bearings etc. Make a conversion of force to effect.
I do not think a centrifugal compressor use a circular radius of the blade hold. This can be a problem. Try to find a similar function of the radius and make a integral for determination of area for each blade.
If you use an axial compressor you can determine the blade profile and calculate "lift" and drag of the profile exactly like an airplane wing and then sum up all the blades. Make a conversion of force to effect.

It is not very hard to calculate this but it is very time consuming and all the approximations must be good enough so the results may not be very close to reality.

[Al Belli]

Hi,

The formula for horsepower required to compress air is:

Horsepower = 0.2267 x CFM (( PSI/14.7 +1) raised to the 0.283 power -1))

An example:
A compressor moving one pound of air a second and giving 8.8 PSIG
will require 25.3 Hp.

Al Belli

[Jim Berquist]

25 kw is a lot of power! I can run my house , my neighbors house, my well there well and a few air conditioners with that amount of electrical energy!!! I want 25KW on the top edge of my altralight air craft! I could fly from Deming to Tucson in about two hours!!!


Jim

[dynajetjerry]

Hi, Guys,

I can't add anything useful to this thread but can mention an electric-powered supercharger that was offered, in kit form, to handymen about 45 years ago. The ads appeared in many magazines and I bit. I may still have some of that stuff buried somewhere.

That company sold several items, including two similar turbo-shaft engines and the above supercharger. Except for a cast steel housing for the speed-reducing gears in the "100 hp @ 4000 rpm" version, almost everything was fabricated from sheet metal and rivets. The axial compressor and turbine were designed to run at 16,000 rpm, total weight of the engine being about 50 lbs. Like Turbocraft products, none were shown to actually work.

The supercharger employed an automobile starter motor whose speed was increased by 4X through bevel gears, and drove a cast aluminum radial-vane compressor. It was appropriately attached to a built-up adapter that was secured between the carburetor and the intake manifold. I never saw or heard of one that actually was useful.

Jerry