Exhaust Heat Recovery - Steam Power

[mpgx2]

Originally Posted by Daox

Peltiers have been talked about in other threads. The conclusion is they are not efficient and you'd need tons in order to get a usable amount of power.

Hi Doax,

Actually, it's not about how to power an electric air pump. That can be
done just with the normal electrical system if necessary.I only mention it
because my car dumps way too much heat being twin-turbo and all.

Volkswagon, on their new cars, use a lot of supercharging and turbocharging
to make them more fuel efficient.

Here's some DIY system for forced induction links:

- DIY supercharger with leaf blower... - AnandTech Forums

- Leaf Blower supercharger + NOS! You gotta see this!!! - Automotive Message Forums

Since electric leaf blowers are for sale on ebay here for about $5
it seems like an interesting option.

[Daox]

We've also talked about turbocharging and how it effects mileage. The general consensus is you need to reduce engine size to gain efficiency otherwise all you are doing is adding to the engine's power output. So, at constant cruise you don't gain any efficiency. Also, a normal turbocharger would be much more efficient since you aren't converting to electricity and back.

[ConnClark]

Originally Posted by Daox

We've also talked about turbocharging and how it effects mileage. The general consensus is you need to reduce engine size to gain efficiency otherwise all you are doing is adding to the engine's power output. So, at constant cruise you don't gain any efficiency.

Not entirely true with a diesel. With some Mercedes the same diesel engine turbocharged gave better mileage.

[MARTINSR]

Originally Posted by ConnClark

Not entirely true with a diesel. With some Mercedes the same diesel engine turbocharged gave better mileage.

However, BECAUSE the car had a turbo on it, doesn't mean the turbo was responsible for the better mileage. It could have been many other factors that happen to have gone along with the turbo on this particular car.

Brian

[Dr. Jerryrigger]

Originally Posted by MARTINSR

However, BECAUSE the car had a turbo on it, doesn't mean the turbo was responsible for the better mileage. It could have been many other factors that happen to have gone along with the turbo on this particular car.

Brian

A turbo make an engine act like one with a larger displacement when under high load. It also can improve the eff of a diesel, or FE by allowing the use of a undersized engine.
But this has nothing to do with heat recovery, so lets get back to the topic.
Steam injection has been shown to improve FE for some people, so as a very minimal way to use some heat is a very small, crude, low pressure, boiler. It's debatable if this helps FE, but it's a way to use the heat for something. The steam could also be used to cook some spinach as you drive, at least it's getting used.
As far as redirecting the energy of the heat back to the drive train, or accessories; that will take a considerably more complicated system. And we have discussed many of the ways in which this could be done. If a boiler is to be used (and i think it's the best option) it is seeming to me that a condensing system will be necessary, as it would reduce the needed amount of boiler fluid (water, or other). It keeps seeming like a A/C system could be scraped for a large amount of the needed parts for this project.

[mpgx2]

Yes, we must get back to the original thread.

When you inject water into a motor with forced injection, you
get steam. Quite easily.

The problem with most turbo systems (ie mine) is they only
boost under acceleration. I wish i knew how to drive the gate
with an the arduino to have it on low-boost all the time like a
turbo-diesel.

The 'best-hack' i can think of is to force-feed water mist in
via a leaf-blower or two and use that. or on the turbo car
just drive the turbo at a small setting all the time.

[Skulldragger]

Another way to convert steam to mechanical force is a simple piston. take a look at the Air Hammer shown here: Simple Air Hammer this is a system using a simple piston and air pressure to move a large weight up and down at a high rate of speed. You could simply attach the piston to a crank and gear it to the speed needed. The size of your piston is determined by the amount (CFM) of steam you can generate.

The Airdrill / die grinder CFM problem is that the CFM rating is what is required to turn that tool at the rated RPM. The PSI determines the amount of torque it will have at that rpm. If you double the psi and half the cfm you will just slow the tool down because it will now be "Starved" for air. Basically you have an internal cavity within the tool that must be filled. PSI is the amount of pressure you are filling it with but with out enough volume the cavity cannot fill fast enough because the tool is using that air as it comes in. As air enters the tool the tool begins to rotate and air leaves the tool, if the tool does not have enough volume it can not fill the cavity fast enough and therefor can not efficiently harness the pressure of the air to apply it to the rotational load before the tool rotates the air out.

In a simple piston setup like the air hammer uses if you have a lower volume it will simply move slower as the valve to switch to the opposite direction is activated by the position of the piston. Here the PSI will determine the power the piston pushes with but the volume determines the speed it moves at. These hammers regularly swing a 25-250# hammer at 250 beats per min which would give you a 250 rpm crankshaft. If you increased the hose and connector size you could increase the speed but these types of systems are meant to run slow and produce a tremendous amount of torque.

A hydraulic piston will work but you will want to include some type of lubricating fluid and will want to keep an eye on the seals of the piston as the heat may break them down. You can find steam pistons on the web but you can find hydraulic pistons at your local farm supply store.

Gearing can be done using pulleys and belts or bicycle chains and sprockets, but if you want it to last for a while I would look into something along the lines of a go-kart drive train with jack-shaft and pulleys.

The turbine you are drawing looks fun to play with but the pressure / volume required to run it would be FAR more than that required to run a piston or air tool setup.

If your Die Grinder could not generate enough torque to run it, try wrapping a short belt around it and the alternator. The die Grinder should rotate at about 10k rpm so cutting that down to even 10:1 (the socket on the die grinder diameter=1/10 the pulley diameter) would still give you 1000 rpm on the alternator and you will have a increase in torque of ~*10.

As for ease of build, I think I would not give up on the air tool side of it just yet. Perhaps instead of using a belt, use a drum sander adapter for the grinder. This could be placed against the pulley directly rotating it, start off slow so you don't just burn the adapter up but it would work about the same as a Tire Hammer which is an alternative to the air hammer can you tell I like hammers?

[C3H8]

i hate to be a doubter, however you would be better off pointing some little steam nozzle out the back of the car and using it for its tiny thrust output. that way the energy could be used to do something directly instead of using it to spin a shaft, which has air drag, and bearing drag, and converting mechanical energy to electrical via a 3 phase alternator, which then converts 3 phase a/c into dc, etc etc.

how many mpg would it increase as a thrust motor? whatever that small number ends up being, its got to be more then making electricity with the same power.


besides, i dont think the thrust of a 5hp 3000psi pressure cleaner would spin an alternator and get any sort of decent numbers, much less some water boiling in the exhaust. and steam is never going to get close to 3000psi or a few gallons per minute of flow.

the final problem is, most ecomodders do not open the throttle on their engines to very much load and rpm's. the exhaust just doesnt get very hot unless you burn lots of fuel which is the opposite goal of an ecomodder. by "hot" i do not mean the temp. i mean, the for lack of better words, the "sustainable heat energy". my 30watt radioshack soldering iron can boil water, and rather quickly too. but it doesnt have enough heat energy to power a turbine driven alternator. i also do not think the exhaust of a typical ecomodder car does, either.

the only way it would have a change of working is if you scrapped the car alternator idea and instead used a tiny motor like that out of a r/c car or a desktop fan. maybe just maybe you might get enough wasted energy out of an ecomodders exhaust to spin something that small.

[Dr. Jerryrigger]

Well there is a lot of energy there.
At 60mph I use about 2 gal in one hour. That's 240,000BTU's
My engine only uses about 20% of that, maybe less under that light load, so that's a extra 192,000BTU's. That's about 56Kwatt hours of energy.
But how much of that can really be gathered? That's the hard part, as the engine was designed to get rid of that heat in many ways. But if 5% of that could be gathered and run through a 50% eff turbine, there would be more energy available than my 75Amp alternator could use

[C3H8]

that brings up a good point. assuming one was actually able to get all this to work properly. lets say for arguments sake you could spin an alternator at 40amps, or 70amps. the number doesn't matter. what i am now asking is, how would you prevent the alternator from over revving and blowing its self up under high heat and low electrical load conditions. example would be cruising down the highway at 70mph during a cool summer day with no a/c on, no headlights or running lights, no real load on the alternator. (worse would be climbing a mountain pass ). the turbine alternator would need some form of mechanical slow down apparatus.

the first thing i would think of would be a waste gate like a turbo has. but turbo waste gate doesn't prevent the turbo from over-revving. it only prevents the motor from seeing excessive boost. proper sizing of a turbo is what generally prevents it from over revving.

you would need some sort of governor or braking system for the alternator to keep it from spinning too fast. i would post a link however i don't have 10 posts under my belt yet.
daviddarling.info/encyclopedia/W/AE_wind_turbine_braking.html
that is a "link" to a website that explains how wind turbines avoid over revving. they either make the blades inefficient during high wind conditions to slow it down, or dump excess power to a bank of resistors.

sense this steam powered alternator in a very basic sense, works along the same principle as a wind turbine, i would think that those 2 ways would also work for the alternator. and i would suggest throwing out the resistor idea. that puts undue load and stress on the alternator not to mention wearing out the brushes quicker then normal. best bet i can see would be some sort of dynamic braking via an adjustable turbine. when things get going too quickly, maybe a spring loaded centrifugal flap could extend and slow things down by creating wind resistance.

although i am still skeptical about this working on an ecomodder's exhaust, i would like to see this succeed. if it ever does i'll be the first one to purchase a unit and install it on my car.

another idea i had was to purchase a small gt series ball bearing turbo and remove the compressor housing and compressor blade. if one were to then install a small pulley on the turbo shaft where the compressor use to be, one could drive a small alternator or generator via a belt off this pulley and shaft. i have a few smaller turbo'd sitting in my garage. none of which, are ball bearing though. :/
i would ot recommend a turbo that uses bushings. they are not designed for radial loads like that which would be experienced with a belt and pulley. they are designed for small axial loads only.