thoughts on Crower 6-stroke?

[Sunwapta]

I think the use of steam to capture energy from waste engine heat is absolutely fascinating.

For the fun of it, Google "steam engines", "stanley steamer", or whatever just to see the torque figures of the old time steam engines.

Makes one wonder why every heavy duty truck and train engine mfr hasn't been researching the heck out of ways to incorporate steam into their systems for the incredible pulling power they could attain.

Maybe a tribrid engine Diesel-Electric-Steam or say a Westport Natural Gas(diesel)-Electric-Steam would be an unbeatable combination for power and efficiency.

[jonr]

I'm always amazed at the number of people who are stuck on torque being such an important engine parameter. It's HP that gets the job done (ie, moves or accelerates a vehicle) and RPM can be traded for torque (with gears).

I agree that a engine that generates a good amount of HP over a wide RPM range (vs a peak at a single RPM) can be important. But give me the HP and RPM specs and torque doesn't matter.

[dcb]

Actually, from an efficiency standpoint, an engine with higher torque and lower rpms can be a good thing (if not done in the usual excesses). This was the mechanical approach used by Matsu Matsuzawa in his 470mpg run. He stroked a one cylinder 125 up to 185cc and probably put a tiny sprocket on the back (plus aeromods, etc)

1985 Matsu talks

[SuperTrooper]

Hp can generate high SPEEDS, but if you need to move something, it's torque that does the job. Why do you think trucks use big, slow turning engines? They often make more torque than HP. (See "diesels")

[dcb]

Well, to jonrs point, an M1 tank uses a turbine that produces very little torque for its power rating (like 262 FTLbs), but creates 1500 hp @ 30000 RPM. The torque to move the tank is obtained through reduction. But an M1 is not a model of fuel efficiency either.

[MazdaMatt]

Back on the engine waste heat being used for steam generation concept... what if the vehicle's downpipes went through a drum containing water (supplied by a water tank elsewhere). The engine heats up, the exhaust is quite hot and starts heating the drum of water. The drum of water could then to used to power a couple extra pistons that were previously just spinning with open valves. Once it is up to temp, the steam starts driving the piston and the valves operate accordingly...

Now this may be silly... the exhaust could bubble through the water for maximum heat transfer and reduction in airborne contaminants (like smoke through a bong)

[SuperTrooper]

First of all, if the exhaust went through the water there would be no way to collect the resulting pressure from the steam. It would go out with the exhaust.

Second, unless you could keep the steam circuit closed (with a condenser) you'd have to carry a significant amount of water to make this work. Water is heavier than gasoline.

[MazdaMatt]

Yes, i realized your first point immediately after posting

I would expect that the downpipes would travel through a small vessel containing a small amount of water so it isn't heating a huge amount at a time. Another tank of water would have to be in the car, yes. I think we've established that weight has a relatively small effect on FE and if we could get SOME return on the efficiency by capturing heat and changing it into power, it may work out fine. The engine could still run without water, too, just with less power and less efficiency.

[SuperTrooper]

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

1. Just running a pipe through the water wouldn't transfer enough heat. You would need a heat exchanger because you need to create HIGH PRESSURE steam to drive a piston. Then, if you were able to tranfer enough heat to make steam there might not be enough heat left to fire off the catalytic converter. Add in the restriction in the exhaust you'd be creating and it would be very tricky.

2. You'd have to carefully control the steam flow to balance engine speed. Meaning, if you are using too much steam to drive that part of the engine the IC side will use less fuel, which will make less heat = less steam.

3. High pressure steam is dangerous! A piping leak or vessel rupture can burn or kill. People are certified to run steam boilers and other similar systems for a reason.

4. The crankcase for the steam portion of the engine would need to be isolated from the IC crankcase, otherwise the steam/water that WILL get past the piston rings will condense and ruin the oil.

He was intrigued enough by the idea to agree that a parallel hybrid design using exhaust powered steam to drive a separate steam engine could occassionally add power for hills and acceleration, but the wieght of such a system would be a genuine concern.

[Gregte]

It would seem that a more useable approach would be to use the waste heat of an IC engine to power a sterling engine. A sterling engine can be designed to run on a very wide range of temperature differentials.