Exhaust Heat Recovery - Steam Power

[gone-ot]

...aware of the 36% weight penalty?

WATER = 8.3 lbs-per-gallon

GASOLINE = 6.1 lbs-per-gallon.

[Christ]

Hey, if a A/C pump will turn as a motor with compressed air being forced through it, what's to stop someone from just piping their exhaust to it? Granted, you'd need more than one to keep backpressure issues away, but the CFM of the exhaust flow should be more than sufficient to make up for the lack of pressure on the line, and it should make decent torque that way.

I know it's not a steam idea, but I still feel like it should be mentioned. I might even give it a shot to pipe one in line with a small engine, just for kicks.

[eco86]

I'm beginning to think that the steam solution is an overly complex solution to this problem of extracting waste heat from the exhaust. Exhaust heat is pretty close to 500F, probably more if you get to it closer to the exhaust ports. Seems that a Stirling engine made to close tolerances would work well off of just the exhaust gas flowing over the hot side heat exchanger, with the cold side of the Stirling being exposed to outside air. The larger the temperature differential the engine is exposed to, the more power it can make.
If you have to machine parts to make a boiler, heat exchanger, and whatever adapters are necessary to join a compressor or gerotor to to the system to work as a steam engine, not to mention the condensor if the system is going to be a closed loop, why not just work on adapting a kit Stirling motor to generating power? Or just machining one? Or arranging some reduction gears to reduce the rpm's of a turbocharger from 150K to 3-5K to drive an alternator?
Just seems like the thread is getting away from DIY when dealing with the necessary specifications to make steam power safe.
So anyway, here's a DIY machined Stirling engine that would produce the necessary power to run an alternator in a vehicle, using air as the working medium.

http://www.youtube.com/watch?v=TBEkd...eature=related

[Dr. Jerryrigger]

Originally Posted by eco86

I'm beginning to think that the steam solution is an overly complex solution to this problem of extracting waste heat from the exhaust. Exhaust heat is pretty close to 500F, probably more if you get to it closer to the exhaust ports. Seems that a Stirling engine made to close tolerances would work well off of just the exhaust gas flowing over the hot side heat exchanger, with the cold side of the Stirling being exposed to outside air. The larger the temperature differential the engine is exposed to, the more power it can make.
If you have to machine parts to make a boiler, heat exchanger, and whatever adapters are necessary to join a compressor or gerotor to to the system to work as a steam engine, not to mention the condensor if the system is going to be a closed loop, why not just work on adapting a kit Stirling motor to generating power? Or just machining one? Or arranging some reduction gears to reduce the rpm's of a turbocharger from 150K to 3-5K to drive an alternator?
Just seems like the thread is getting away from DIY when dealing with the necessary specifications to make steam power safe.
So anyway, here's a DIY machined Stirling engine that would produce the necessary power to run an alternator in a vehicle, using air as the working medium.

Steam is hard to integrate, but really offers the best potential for recovering a high percentage of heat. I really can't see getting much power back from a sterling, though it could be fine for a alternator and or other accessories.
Of the fuel's potential energy 70-90% is lost as heat. If 25% of that energy could be used you would have about twice the power.

[jdgFirefly]

Daox the type of pump I was thinking of is a small power steering pump or maybe a oil pump but these may have poor eff (leaky). I know the older style gear pump is not vary eff. I heard that power steering pumps are vane style. Dr jerryrigger suggested a pressure washer pump. It would be nice if a power steering pump would work because it already has the pulley so it might be easier to adapt.

old tele man your right there would be a weight penalty but it would depend on how much water your hauling. Really it would only be significant for an open system, a closed system wouldn't need to store vary much water.

Eco 86 your right about this being complex issue, But I think the main point of this thread is to discuss DIY ways that it can be done. By using already available parts it is really a matter of plumbing and fittings. The exhaust "boiler" might be the only part that needs to be fabricated, but so far in the discussion its only a matter of welding tubing together no machining. In contrast a good power producing sterling engine needs to be designed and fabricated from the ground up using lathe, milling and welding, so it also is not exactly DIY friendly.

[Daox]

What kind of pressures do power steering pumps work at?

[jdgFirefly]

I don't know what pressure they run at. However the thing about positive displacement pumps is if you have infinite power to turn them you can have infinite pressure (pending catastrophic failure). Leak by will make a difference too. A eff pump with vary little leakage would be ideal.

[jdgFirefly]

The question we should probably be asking is what flow rate do we need? And does it need to be variable flow or even intermittent? I'm thinking that if the pump is connected to the expander/motor it will automatically vary flow with rpm. If its pulley driven, the flow could be fine tuned by changing the pulleys.

[Phantom]

Back to the air tools idea, if you get a tool that has a good amount of torque but is not fast enough that can be solved. The test with the die grinder was effectively running 1:1 being directly connected to the alternator. Now if the grinder is geared say a 2" pulley on the grinder and 1" on the alternator this places it at 1:2 so if the grinder is running at 200rpm the alternator will be at 400rpm.

An easy way to test what ratio would be needed it to use the sprocket from a bike so all that would need to be done is move the chain to the next gear to change the ratio till a suitable one is found.

[mpgx2]

Originally Posted by Daox

I'm just getting back from vacation so I'm playing catch up here.

Any ideas on an inexpensive high pressure pump to use? That would probably be my main concern. Controlling that pump would be my next concern.

I'm chatting with mechanical friends who have more aptitude than me.. lol

One of my friends just got a smog-pump to supercharge a gocart
engine. As in:

Dirt Cheap Supercharger - Turbo Motorcycles, Hot Rods Bikes,Turbo Bikes,Suzuki,

The advantage of the smog pump, apart from being cheap is that they
are already automotive grade.

There are two types, mechanical and electrical. Smog pumps off old
V8's have power - and have no problem handling exhaust type heat.

I prefer electrical and as I'm thinking I could drive it from an
arduino with code like:

djlyon / mpgx2 Vapour workbench / source — bitbucket.org

ok - maybe better code - lol