OT: Interesting new idea, the six-stroke engine Options

[lapuwali]

Crower (of Crower Cams) has just patented a new "six stroke" engine design. The crank turns 3 times for each single cam revolution. The extra two piston strokes are after the normal exhaust stroke, and involve water direct injection into a closed cylinder. This flashes into steam, and produces a second power stroke. The exhaust then opens to vent the steam. Enough heat is drawn off by this steam production that no actual cooling system is required.

It's claimed this can improve fuel economy by as much as 40%.

He's got a single-cylinder spark-ignition prototype working, and is now working on a compression-ignition version.

[lapuwali]

I don't know where to look up the expansion time for water into steam, or the "flash" time, but there's a fair amount of time to play with here. If we just pick a number out of the air, say, 3000rpm, that means each full crank revolution takes 20 milliseconds, so each stroke takes 10ms. Figure you'd actually use more than one stroke for the expansion time, as you'd likely inject the water while the piston was still rising on the exhaust stroke. Let's say 150% of one stroke, or 15ms. That's a pretty long time, really. Plenty of reactions are measured in picoseconds. Sammy, I'd love to see some actual numbers on this, since I have no idea what the actual times are.

We're not going to be talking a large volume of water here, either. Since water expands to 1600 times its volume as steam, a volume of water that's about 1% of the cylinder volume would generate considerable pressure as steam. That's 5cc for a 2.0 four, which would expand to 8000cc of steam, or 16bar of pressure in the cylinder with the piston at BDC. If the water were injected with the piston near TDC, you'd be looking at a number 8-10x that.