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Power-User

Join Date: Jun 2005
Posts: 104

Searching for power dense 4-stroke small generator for race-EV application

07/17/2009 11:55 AM

I'm looking to find a power-dense 4-stroke engine that operates at around 10kw/13hp (100cc or so) hopefully operating at near 10,000rpm or so for weight considerations.

The application is a generator set for a series hybrid for the formula hybrid competition (formula-hybrid.org)

I've searched around and all I can find are motorcycle engines that have the added mass of a gear case.

Does anyone know where I can find a high-speed small generator of this kind?

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Guru

Join Date: Jun 2009
Location: South of Minot North Dakota
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#1

Re: Searching for power dense 4-stroke small generator for race-EV application

07/17/2009 12:49 PM

What output voltage do you need?

Just use a ultra lite engine or another type of small air craft engine. There are 4 stroke snowmobile engines now too. They can easily be re-jetted or reprogrammed on the fuel injected ones for normal summer time operation. I have seen them used on ultra lite and gyro copter designs once at an air show and read about them many times.

They have the small size and high horse power you need.

As far as a high output generator that works at high RPM a big truck or heavy machinery alternator can be modified to put out higher voltages than stock and be rewound for higher than stock amperages too. I have read about some aftermarket kits that can take a 24 volt 200 amp stock alternator and put out over 450 amps while maintaining 28.8 volts so that would be about 12960 watts!

Direct drive the alternator with the snowmobile engine and your set. Just expect to spend some money though. Small high powered custom stuff gets exspensive real fast!

Just something to think about.

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Guru

Join Date: Dec 2005
Location: Queensland Coalfields Australia.
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#4
In reply to #1

Re: Searching for power dense 4-stroke small generator for race-EV application

07/21/2009 12:48 AM

Good thinking.

Automotive alternators really scream around anyway when you look at the pulley ratios. Hopping them up for greater output can be a bit dodgy unless done by someone who really knows his stuff. Core saturation and voltage gain are two probable issues that come to mind. Permanent magnets could help a lot as would improved bearings and balancing.

For really high specific power, Orbital Engine Company of Perth Western Australia have the technology, but I doubt if they will build for you or sell you one. They largely abandoned the actual Orbital engine when they couldn't get it mass produced (more complicated than pistons).

Fuel consumption will probably blow a Wankel out of the water, 10,000 RPM would be slow for one of those.

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Guru

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#2

Re: Searching for power dense 4-stroke small generator for race-EV application

07/18/2009 12:17 AM

10,000rpm? Wow.

Yes, there are quite a few sources of engines for this duty, as previously stated, incl jetski, motorcycle, etc, but perhaps not as low in capacity as you'd like.

The problem lies in the generator. There is a limit to the working rpm of a rotor assembly, due purely to mechanical forces. Rare ones will do the service but be expensive. Most everyday auto type units will not stand these sustained forces.

Here we go again--I've assumed that you're looking to 'low Voltage', ie 12, 24, 36?

Working life will be relatively short at these speeds.

Get back,

Cheers

Stu.

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Guru
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#3

Re: Searching for power dense 4-stroke small generator for race-EV application

07/18/2009 12:06 PM

Honda makes a line of inverter based gensets that are actually DC generators feeding an electronic inverter. Perhaps one of those might fit the bill.

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