thoughts on Crower 6-stroke?

[rmay635703]

This concept is very old and was used rather sucessfully in the early 20th century on large boats.

They were 1 cycle diesels, top end was diesel, bottom side of cylinder was water.

Unfortunately this design required a lot of maintenance as the water, oil and diesel were always going places they didn't belong.

I thought about this concept years ago and figured, why not use a low temperature boiling liquid, a heat transfer system like a radiator on the hot side and simply have a closed circuit steam engine similar to modern AC so the chemical stays enclosed and recirculated. Use the steam to run an alternator or generator for a semi hybrid. You could also remove the radiator if the engine was redesigned with ceramics to increase the amount of heat available to drive the steam and if we use a liquid that boils at a lower temp than water you would have almost instant on.

Remember folks there were some very advanced enclosed steam engines that were actually more efficient than diesel in the late 40's. Sadly most of that engineering genius and skill was lost with the steam era. I think steam opens many possibilities beyond fossil fuels and the capillary boilers of the 40's with their instant power system would blend well with a renueable. heck corn, leaves, wood chips, anything might make a viable fuel in a steam engine!

[SuperTrooper]

It appears there is being work done on the steam from exhaust front:

http://ecomodder.com/forum/showthrea...html#post59291

[Big Dave]

The term is called compounding. It has been around for a long time. The gasoline aircraft engines of the mid-40s were sometimes compounded. The R-3360 engines used on B-29s were tubocompounded and were very efficient. Without the efficiency of the turbocompounded engines, missions from Saipan to Tokyo would have been impossible. The Napier Sabre emgine was used in British Shackleton patrol planes after the war was maybe the most fuel efficient internal combustion engine of all time.

Both th R-3360 and the Sabre were maintenance nightmares.

Using compounding works OK for aircraft and ship powerplants because those engines see very flat duty cycles. An airplane takes of at full power then throttles back to a cruise speed to get close then throttles back to nearly a glide for approach. Cars don't get used that way. They rip up and down through their operating range and rarely operate at rated power. Thus the Rankine or Brayton cycle compounding engine never gets a chance to stabilize and make meaningful power.

Another factor is that IC engines, when operated at constant speed is more efficient than you think. This is especially true of diesels. Big marine diesels are so efficient that there is not enough heat left in the exhaust gas to do much of anything. The owner would have to spend a lot of money for very little return.

Far and away the most successful compounding scheme has been the turbocharger. A Brayton cycle spins the supercharger for an IC engine.

The mostI'd expect of a steam compounding scheme for a car would be enough electricity to run the alternator and maybe the power steering. Its been tried with air conditioning and found wanting.

Stirlings are efficient and run on low delta-T but they are huge and expensive for the power they produce. A 20 HP Stirling would be as big as an office desk and weigh 1500 lb.

These ideas have been around a long time. The Stirling was invented just a little later than the steam engine, but the steam engine (although clearly less efficient) became dominant for a century and the Stirling was a curiosity. Then the IC engines came along and within seventy years relegated steam engines to a niche role.

Don't you ever bother to wonder why? Do you think that hundreds of thousands of engineers over the years were complete blockheads? Or that some deep, dark conspiracies kept thee ideas inthe shade?

[jamesqf]

Originally Posted by Big Dave

Both th R-3360 and the Sabre were maintenance nightmares.

If you read up on the history of turbo-compounding, though, you find that the reason it's no longer used is that it was more efficient - both thermodynamically, and from a mechanical/maintenance perspective - to get rid of the IC engine half, and just run the turbine. And thus the turbo-prop was born :-)

Don't you ever bother to wonder why? Do you think that hundreds of thousands of engineers over the years were complete blockheads?

Sure, I wonder why. And I don't think the engineers were blockheads (especially as you can find records of plenty of engineering prototypes that worked quite well). I do think the management left a lot to be desired.

Or that some deep, dark conspiracies kept thee ideas inthe shade?

When I look at the currrent automotive scene, the conspiracy theory seems pretty plausible. Is there a better reason why it's so hard to find even halfway decent cars? Quite aside from all these alternative powerplant ideas, the obvious way to build a fuel-efficient car (and one that's fun to drive, too) is to make it small and light. There have been a few of those over the years, but they're the MGs and Lotuses out on the margins, while the mainstream automakers spend large sums of money persuading people that big & heavy is where it's at.

I doubt the deep & dark, and I suppose the conspiracy part depends on your definition of the word. It seems more like a bunch of short-sighted idiots blundering through life than an actual conspiracy, but it'd be a piss-poor excuse for an engineer who couldn't do better than anything has comes out of Detroit since the end of WWII.

[Big Dave]

Brayton cycle engines' thermal and mechanical efficiencies do not surpass those of internal combustion engines until you get to Frame 8 utility sized (400 MW(e) and up). Turboprops are indeed reliable (the Pratt PT6 is legendary - their MTBF is two pilots' careers) and very powerful for their weight, but are unmitigated fuel hogs at most altitudes. The LM2500 engines commonly used on warships are very reliable and easy to mantain but are nowhere near as efficient as big marine diesels.

In general, what drives engine design is available materials.

[MazdaMatt]

Originally Posted by SuperTrooper

Matt, at lunch I ran this thread by my facility's steam/HVAC expert. He came up with several thoughts:

Thanks for the insight

[rmay635703]

Yes but... If we were to place a constant output motor that runs at a very high efficiency but throttles up/down slowly couldn't one use it to run a generator with a small bank of capacitors or batteries to make up the power differential during acceleration?

The batteries/capacitors would have to be sized just big enough to allow for the accelleration periods, then the motor would take over driving the car directly once the car was steady state, similar to a hybrid but with more reliance on the electrical system.

Originally Posted by Big Dave

Don't you ever bother to wonder why? Do you think that hundreds of thousands of engineers over the years were complete blockheads? Or that some deep, dark conspiracies kept thee ideas inthe shade?

Actually we are generally lazy when we can be and follow the KISS principle, don't change that which is not broken until you must, then worry about the alternatives and their specific issues. Follow the reducing returns and hope the infastructure is better later if you have to impliment it (AKA hope someone else fixes the bugs in the meantime).

Rarely in my job do I have to venture into areas that aren't fully explored, just make solutions that follow ideas that are already understood. In design also, follow it by the book until you can't. (then mod it to follow the book if at all possible should that strange situation arise)

Originally Posted by Big Dave

The term is called compounding. It has been around for a long time. The gasoline aircraft engines of the mid-40s were sometimes compounded. The R-3360 engines used on B-29s were tubocompounded and were very efficient. Without the efficiency of the turbocompounded engines, missions from Saipan to Tokyo would have been impossible. The Napier Sabre engine was used in British Shackleton patrol planes after the war was maybe the most fuel efficient internal combustion engine of all time.

Both th R-3360 and the Sabre were maintenance nightmares.

Using compounding works OK for aircraft and ship powerplants because those engines see very flat duty cycles. An airplane takes of at full power then throttles back to a cruise speed to get close then throttles back to nearly a glide for approach. Cars don't get used that way. They rip up and down through their operating range and rarely operate at rated power. Thus the Rankine or Brayton cycle compounding engine never gets a chance to stabilize and make meaningful power.

Another factor is that IC engines, when operated at constant speed is more efficient than you think. This is especially true of diesels. Big marine diesels are so efficient that there is not enough heat left in the exhaust gas to do much of anything. The owner would have to spend a lot of money for very little return.

Far and away the most successful compounding scheme has been the turbocharger. A Brayton cycle spins the supercharger for an IC engine.

The mostI'd expect of a steam compounding scheme for a car would be enough electricity to run the alternator and maybe the power steering. Its been tried with air conditioning and found wanting.

Stirlings are efficient and run on low delta-T but they are huge and expensive for the power they produce. A 20 HP Stirling would be as big as an office desk and weigh 1500 lb.

These ideas have been around a long time. The Stirling was invented just a little later than the steam engine, but the steam engine (although clearly less efficient) became dominant for a century and the Stirling was a curiosity. Then the IC engines came along and within seventy years relegated steam engines to a niche role.

Don't you ever bother to wonder why? Do you think that hundreds of thousands of engineers over the years were complete blockheads? Or that some deep, dark conspiracies kept thee ideas inthe shade?

[FX Flyboy]

Originally Posted by rmay635703

Yes but... If we were to place a constant output motor that runs at a very high efficiency but throttles up/down slowly couldn't one use it to run a generator with a small bank of capacitors or batteries to make up the power differential during acceleration?

The batteries/capacitors would have to be sized just big enough to allow for the accelleration periods, then the motor would take over driving the car directly once the car was steady state, similar to a hybrid but with more reliance on the electrical system.

Thank you!

I've been waiting for someone to suggest such an option. This at least could give us highway efficiency in all conditions, even in heavy traffic. The problem is weight, but the whole set up should weigh less than the good portion of battery stack a usual EV conversion seems to carry around. Half that for some grid capasity, and put in a 20 HP generator for the rest seems a viable solution for extending an EV range.

Another more complicated solution is trying to obtain higher efficiency from the set up, by getting some power back from from the exhaust and cooling heat. Here the six cycle engine could be an advantage. Imagine having a 30HP engine, that uses the same amount of fuel as a 20HP one. (dreaming...)

I can see the major issue to be overcome in form of water condensation in oil and causing lubrication problems. Since it would be going straight into the sump in most car applications, isn't there a some sort of filter element in place, like a brass (is it brass?) water repellant screen before it goes into the pump? I know this is used in motorcycle fuel tanks, but this obviously is a different set of conditons.

I've also heard of full-seal piston rings, would they help solving it at all?

I know this is just a set of ramblings, but they seem logical to me.

[FX Flyboy]

And one more thing. Lot of folks mention that since the six cycle engine needs water, than you'd need to carry lots around. Well, yes and no. If you get 40% in fuel savings, then you need only 60% of the original amount of fuel on board for the same range. You also don't need the whole cooling set up, therefore, practically, you maybe adding 15 - 20 kilo for and average car, which you can control anyway, like you control the amount of fuel already.

Just my two cents.

PS. In terms of lubrication pure gasoline is not very good, therefore it contains additives that go onto the surface of the cylinder. This might be obviously not within the scope of a backyard mechanic, but perhaps a backyard chemistry fanatic would know a good water additive that could work the same way. Ideas anyone?

[wumpus]

Originally Posted by rmay635703

Actually we are generally lazy when we can be and follow the KISS principle, don't change that which is not broken until you must, then worry about the alternatives and their specific issues. Follow the reducing returns and hope the infastructure is better later if you have to impliment it (AKA hope someone else fixes the bugs in the meantime).

Rarely in my job do I have to venture into areas that aren't fully explored, just make solutions that follow ideas that are already understood. In design also, follow it by the book until you can't. (then mod it to follow the book if at all possible should that strange situation arise)

It should be noted that when something goes wrong, management will always blame the least safe design first. You have to have absolute iron-clad proof it wasn't you, then they check the next most risky design. You can't expect to make a career of coming up with unique solutions. You can't really expect to do it very often. Last I hear, Detriot was looking to axe plenty of white collar jobs...