Re: Six Stroke Engine

Harry K wrote:
Stu wrote:

From http://www.damninteresting.com/?p=467

<snip mechanics of an internal combustion engine (ICE) >

The clever new six-stroke design was developed by 75-year-old mechanic
and tinkerer Bruce Crower, a veteran of the racing industry and a the
owner of a company which produces high-performance cams and other engine
parts. He had long been trying to devise a way to harness the waste heat
energy of combustion engines, and one day in 2004 he awoke with an idea
which he immediately set to work designing and machining. He modified a
single-cylinder engine on his workbench to use the new design, and after
fabricating the parts and assembling the powerplant, he poured in some
gas and yanked the starter rope. His prototype worked.

His addition to the ICE design is simple in principle, yet a stroke of
genius. After the exhaust cycles out of the chamber, rather than
squirting more fuel and air into the chamber, his design injects
ordinary water. Inside the extremely hot chamber, the water immediately
turns to steam- expanding to 1600 times its volume- which forces the
piston down for a second power stroke. Another exhaust cycle pushes the
steam out of the chamber, and then the six-stroke cycle begins again.

Besides providing power, this water injection cycle cools the engine
from within, making an engine's heavy radiator, coolant, and fans
obsolete. Despite its lack of a conventional liquid cooling system, his
bench engine is only warm to the touch while it is running.

From the Autoweek article:

"Especially an 18-wheeler, they've got that massive radiator that weighs
800, 1000 pounds. Not necessary," he asserts. "In those big trucks, they
look at payload as their bread and butter. If you get 1000 lb. or more
off the truck..."

Offsetting that, of course, would be the need to carry large quantities
of water, and water is heavier than gasoline or diesel oil. Preliminary
estimates suggest a Crower cycle engine will use roughly as many gallons
of water as fuel.

Bruce Crower holds a patent on the new design- which he is still
developing and tweaking- but he estimates that eventually his six-stroke
engine could improve a typical engine's fuel consumption by as much as
forty percent.


Interesting and tricky. Must be an interesting valve train to get the
extra two cycles in.

Somehow I suspect it is not practical. The thought of spraying cold
water on red-hot parts doesn't sound good.

Harry K

If you have red-hot metal inside your combustion chamber and aren't in the process of running an 8-second quarter mile or a dozen flat-out laps around the dirt track, find the nearest repair shop - you're in trouble. Diesels inject cold liquid into a hot chamber by design - Crower's prototype is a diesel that injects water instead.

From the Autoweek article: "Recently he’s been trying variations of the double-lobe exhaust cams to delay and even eliminate the opening of the exhaust valve after the first power stroke, to “recompress” the combustion gasses and thus increase the force of the steam-stroke."

That's where the real payoff should be, injecting water into a chamber full of hot exhaust gas that's been heated further by compression. Not that much water either, at a 1600:1 expansion rate.

Built with quality materials, using small tolerances and an exhaust system that stays above 212 degrees fahrenheit during operation, I don't see a single problem with the concept. What I question is the claimed 40% fuel efficiency improvement in spite of the amount of effort required to re-commpress the exhaust gas from the combustion stroke....hmmm.


CC
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