Interested in adding a turbine (minus compressor) with a switch reluctance generator to my exhuast. Not interested in pressurizing my intake only wanting to relieve my alternaotr and reduce parasite drag on the motor. The Garrett turbo-e looks like a good place to start. Know of anyone else that has attempted this modification.

 

Electricity from an alternator is NOT really free energy..
Where exhaust flow is much more free energy...
unless its designed like a Prius ...

 

I think he is talking about using the exhaust flow to spin a turbine, thus creating voltage/amperage to act as a alternator.

 

I[shadow=red,left] think he is talking about using the exhaust flow to spin a turbine, thus creating voltage/amperage to act as a alternator[/shadow]

Yes exactly....the turbine spins a generator which produces amps to assist and/or replace the alternator. There by reducing parasitic drag from alternator, water pump, cooling fan, AC and steering pump. An aux. battery is also included to operate these devices during idle conditions.

 

Wow, very interesting idea.

Now you just need to hook one of those ebay electric turbos to the exhaust driven alternator

 

thats one helluva alternator to withstand that kind rpm and heat.

maybe you could rig up some kind of transmission like reversing a centrifugal supercharger.

 

I can't see this working well.

An alternator is really very efficient and only uses a couple of HP when at full output. Underdrive pullies don't do any benifit with the alternator, only the other accessories like the pumps (AC, PS, water).

 

I have seen lots of Garrett "E-Boost" presentations over the years in my job.

The "e-boost" device is expensive to then disassemble and use for adding electricity to "help" your charging system. The output is not very good as an alternator either. Work has been done over the years to make a flywheel assembly an alternator.

In WW-II, airplanes used turbine energy to drive the crankshaft of the engine with very good results. That would free up HP to drive a high output alternator. Designing a device that drove the starter flywheel using turbine energy might be easier to rig up than many assume.

Tom Vaught

 

Am I understanding you correctly? You want to replace the alternator that mounts right up on the engine already with a bracket, wired in, and optimized with a turbine to generate current to power the vehicle?
Doesn't seem very cost worthy or efficient. Its not going to reduce the parasites in your engine either since it'll still have to work against the turbine instead of the alternator....

 

How much hp can an alt. eat up??????????? 10??

 

10 HP at 90% efficiency is 6711 watts or 560amps at 12V

2 HP would be more accurate, and that would only happen when there is a heavy electrical load.

 

An automotive alternator at high load is very poor efficiency (sometimes as low as 50%). Also there is the inertial effects of the alternator. Even if you disconnected it and it was not even excited it would consume a small amount of power from the engine just accelerating its mass. 10Hp might not be too terrible an estimate. None of this is to encourage the original idea as it is a terrible one.

 

Even at 50% efficiency, the alternator would be putting out over 55 amps with 2HP of input. Most turbo mustangs rarely draw more than 55amps (10% of operating time maybe).


Even with belt/mechanical losses, I can't see estimating more about 5HP max.

 

We shouldn't be speculating like this in the advanced section. This can easily be calculated if we have the following:
1. alternator rotor diameter
2. alternator rotor weight
3. alternator pully diameter
4. Crank pully diameter
5. Acceleration rate of engine (rpm per second)

I don't have a reasonable feel for the first two. If someone will give me some reasonable numbers I will calculate the power required to accelerate the inertia. We can add this to the power consumed from electrical load which we do have a reasonable feel for and have a good idea.

 

just wondering if it is possible to marry this idea to an engine that already has a turbo and run the shaft off of the turbo's main shaft? The turbo is already spinning so there would be no restriction. Or is the internal mass of the alternator too much for the turbo to efficiently run?
I ask only b/c if you were to put a thermal alternator on a vehicle I don't see how you would control it's speed. If it were integrated unto the turbo system the wastegate would keep it under a given RPM. Just thinkin

 

Alternators weren't designed to sipin at a 100k+ rpm.

 

An SR machine as was specified in the original post can be designed mechanically for 150k no problem. I would couple the front bearing to run in oil from the turbo and and try to get away with a sealed bearing on the non drive end. The heat as metioned earlier would not be an issue either. The problem would be the winding. I don't think a two pole machine which would be absolutely neccessary at these speeds could be practically designed with few enough turns to make it 12V. You need enough turns in the coil to make it windable. It would almost certainly need to be 42V or higher. But what do I know?

 

There's no speculation to it. 1HP=746 Watts. This means that my 105 amp CS-130 alternator outputs 1449W at 13.8V. A contemporary 3 phase synchronous motor can be up to about 65% efficient on a good day. Even going with 50%, this comes out to 2898 or 3.88hp input from the engine. The cure is probably worse than the disease, in all likelyhood you would be better off using a set of long tube headers for both efficiency ad power than to remove the alternator. If you want to do something to eliminate your alternator I have heard of the auto industry messing with thermal junctions that are similar to Peltier coolers to make power. Don't know anything about it other than that though.

 

You are forgeting about the inertial effects which I suspect are more significant than the electrical power. It is a rotating mass just like your flywheel. If you disconnect the alternator and it just spins free shaft (no electrical load) it still consumes power from the engine during acceleration. It is this I say we should calculate.

 

I understand your point Andy, but I really think the effects will be small. There isn't a lot of mass there and it's not spinning THAT quickly. I can't help but imagine an electric motor instead of the crank. With no load on the alternator, a 1 or 2HP motor will spin up that alternator up very quickly. Heck, a 110V air compressor has a 2hp RMS motor (for the large ones). That motor would spin up the alternator very quickly.

Even with the information you ask for, you would not be able to accurately estimate the load.