Exhaust Heat Recovery - Steam Power

[Daox]

Well, tonight I tried the die grinder again using the flywheel method using the alternator itself as the flywheel. I spun it up and then connected the alternator field wire. It very quickly reduced in rpm and choked the grinder. It probably produced usable voltage for 1.5 seconds. So, you'd need a fairly hefty flywheel I'd imagine.

[Dr. Jerryrigger]

So we're still talking about at least three different plans here (which is okay by me, they are all good ones, just a little hard to follow).
So pumps: the pump would be quite different dipending on what we are doing with the steam. I'm a fan of very high pressure, but there are a lot of draw backs to this. With a pump you need it's rating to exceed the pressure made by the steam and a flow rate that can match or exceed what you want for red lining with WOT (which I suppose could be the same as what you want at 3k RPM's). Also we must consider the flow rate to water supply. It would be best if one only had to fill the water tank once per gas tank (long term, not necessary for proto-type, just should think about it). Recovering condensed water seems like a good idea, and could result in less energy loss.

As far as a controller the pulley is a nice simple way of making the flow proportional to RPM, but is that really good? I downshift for DFCO, which could result in over cooling the boiler and blasting water into the turbine. I think to integrate this into a modern engine we would need some temp and pressure sensors hooked up to a simple possessor that would control a PWM run 12V pump.

[mpgx2]

Yes, there are a few options.

One thing we also need to keep in mind is that steam
naturally expands and will drive itself. It shouldn't need
any pumping. Quite the reverse, it requires regulation.

All that should be required is a reservoir with water
and a ball-type high-pressure valve, copper-pipe and
a place to feed the inlet.

Me and friends have discussed this more than done it.

A case of too many idea's i think.

One place to put the water-tanks is inside the spare
wheel. Another place, is to put tanks under the front
wings-gaurd-panels. They won't be seen.

I myself have had to learn basic electronics recently
otherwise I would be a lot further along. It's nice
chatting with the like-minded in any case.

[jdgFirefly]

Watch your head theirs Ideas flying all over this thread

The pump I'm talking about is for a closed loop system for pumping the low pressure condensate back into the higher pressure boiler. If you make a open system you don't need a pump, but either your boiler will need to store all the water for one trip or you will need a high pressure storage tank.

Daox it sounds like the die grinder just isn't powerful enough. Adding a flywheel can smooth out power delivery via inertia, but I don't think that's the problem. Just need more power. I'm amazed that just the field windings take so much power that a die grinder can keep up.

When I was talking about the pump being belt driven I was talking about it being driven by the steam expander or turbine, so when X amount of steam goes through the expander Y amount of water is always pumped back in. I was thinking we would need to get roughly the right size pump then fine tune the flow rate by changing the pulleys. I like the bicycle chain and sprocket idea, rig a couple rear cassettes to replace the pulley and you now have many ratios to choose from.

[Dr. Jerryrigger]

okay so let's say we're running a system that puts out steam at 600F, that would limit the pressure to about 1000PSI (water boils at 547F at this pressure). So in the boiler we have 1000PSI, how do you get more water in to the boiler with out pushing water/steam out the wrong end of the boiler without a high pressure pump? Maybe I'm missing something with the physics of a boiler...???

[Dr. Jerryrigger]

Daox,
good work with the grinder. Those grinders are generally have high RPM low torque out put. Do you have any other pneumatic tools to try with?

jdgFirefly,
I missed the turbine driven belt pulley idea, that is interesting, and may work well, though turbines generally spin in the 15K+ rpm range...
I'm a little unsure of the way it would react to normal driving. There are sudden changes from lots of heat to none in the exhaust. I feel a system like this would have to much of a delay to react to this effectively. But a turbo charger acts in a similar way, before an acceleration you might warm up your boiler...

[jdgFirefly]

Originally Posted by Dr. Jerryrigger

Daox,
good work with the grinder. Those grinders are generally have high RPM low torque out put. Do you have any other pneumatic tools to try with?

jdgFirefly,
I missed the turbine driven belt pulley idea, that is interesting, and may work well, though turbines generally spin in the 15K+ rpm range...
I'm a little unsure of the way it would react to normal driving. There are sudden changes from lots of heat to none in the exhaust. I feel a system like this would have to much of a delay to react to this effectively. But a turbo charger acts in a similar way, before an acceleration you might warm up your boiler...

the pump could be driven by a turbine or expander, whatever is used, and by expander i mean positive displacement motor. A PD motor could be low rpm high torque.

Regarding the delay in system response, I don't think it will be a problem if its just driving the alternator.

About the pressure, I'm only thinking of a lower pressure system like 300psi and under or even below atmospheric pressure. the reason I'm thinking lower pressure is because it is safer and easier to build but also at lower pressures we will be able to remove more of the heat from the exhaust. I'm even thinking if its bellow atmospheric pressure then the engine coolant could even boil the water and maybe the exhaust could super heat the steam.

Of course a low pressure system would be bulkier, maybe to the point of impracticality.

[Christ]

Originally Posted by 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.

I have a pulley that I can change diameters on just by threading the outer flange further onto the hub flange. It goes from something like 2" to 4" or so.

[LeakyIdeas]

Why worry about a boiler? i can see two options without one.

if you drip a small amount of water into a tube at 500F it expands to about 1600times it's volume,
effectively giving you a plusejet if the tube if small. requiring just a one way value and either a piston + conrod attached to a ratchet and flywheel, after the 'charge' is spent there is very little presure so the next drop can be added. but that requires a bit of metal work...and off the shelf microbore copper pipe.

another option,

if you heat small rc motor to 500-600F and small amount of water is injected a few degrees ATDC, it will expand 1600 times and force piston down....hey presto you have a tiny steam engine. you don't need much pressure to inject the water depending on the porting of the 2 stroke motor, as high compression is not required, and you don't have to worry about storing steam...just condensing the exhaust assuming you want to recycle the water.
small solenoids are easy to buy and time with a magnet and reed switch means nothing clever (pics etc) should be required.

I'm looking on ebay at the moment for something i can use...best should be a broken 2 stroke RC motor, 'diesel' should be good as it already has a threaded hole to the head in the form of a compression adjustment screw.

[Dr. Jerryrigger]

Originally Posted by LeakyIdeas

Why worry about a boiler? i can see two options without one.

if you drip a small amount of water into a tube at 500F it expands to about 1600times it's volume,
effectively giving you a plusejet if the tube if small. requiring just a one way value and either a piston + conrod attached to a ratchet and flywheel, after the 'charge' is spent there is very little presure so the next drop can be added. but that requires a bit of metal work...and off the shelf microbore copper pipe.

another option,

if you heat small rc motor to 500-600F and small amount of water is injected a few degrees ATDC, it will expand 1600 times and force piston down....hey presto you have a tiny steam engine. you don't need much pressure to inject the water depending on the porting of the 2 stroke motor, as high compression is not required, and you don't have to worry about storing steam...just condensing the exhaust assuming you want to recycle the water.
small solenoids are easy to buy and time with a magnet and reed switch means nothing clever (pics etc) should be required.

I'm looking on ebay at the moment for something i can use...best should be a broken 2 stroke RC motor, 'diesel' should be good as it already has a threaded hole to the head in the form of a compression adjustment screw.

I seem to recall water to steam expiation is 1:1075, but that is likely not factoring in a large temp change. Anyway, that doesn't really matter at all...

If we are just trying to drive the alternator, then this drip boiler seems like it would really be quite sufficient. I feel like it would need a rather beefy fly wheel, which might have some trouble getting started, but popping the hood and giving it a spin start is not big deal.
Dose anyone have access to CNC machines? I'm willing to draw up a turbine/fly wheel. It seems like it would be best to just make the turbine directly connect to the alternator shaft, and be really heavy, though a easy to alter weight may be good....