thoughts on Crower 6-stroke?

[dcb]

Originally Posted by jamesqf

when a Stirling engine is thermodynamically even better

Good question though. Someone who knows something about those should start a thread on it.

[Big Dave]

When somebody like Bruce Crower talks, I listen, but I am a bit puzzled he hasn’t put this baby on a dyno yet. Normally when somebody like Crower or his type can get the engine to idle, they want to put it under load and see what she’ll do.

I suspect he’s got injection problems. Ideally, he should have two injectors – one for fuel, the other for water. That’s why he started out with a carbureted gas engine – so he could use the injector for water. But for a man of Bruce Crower’s savvy and means even a one-off special hear and camshaft drive, so he must have a severe problem somewhere. Maybe he is having problems with the injector. Water has very low viscosity and friction in the injector may be giving him fits. Maybe he is having problems getting the water to flash to steam fast enough. Maybe the water/steam is causing lubrication problems.

Presuming he can overcome his mechanical problems, this engine should be an elegant means of improving thermal efficiency and even power in a given size. Always compounding (that’s sorta what this is) has used a separate “engine” (such as a turbocharger or the turbocompounding engines used in the mid 1940s) but crower uses the same piston and crankcase.

If he can recover and use half the rejected jacket heat, he could be looking at a 10-15% improvement in thermal efficiency. That is huge. Maximum thermal efficiency has not moved in over a half-century since the Napier Sabre and R-3360.

Back in the 70s Cummins tried a different approach. They used a ceramic liner to take the heat of an uncooled jacket and recovered the power in a better turbo. My understanding is that they had lubrication problems.

BTW, the big drawback to a Stirling engine is the size and complexity of the machinery required for a given amount of power. To make the power of a chainsaw engine, a Stirling would have to be the size of a big US V-8 SUV engine. The size and cost have up til now always overwhelmed the efficiency. Other than the little toy engine kits you can buy, I doubt there are a half-dozen Stirlings on the planet.

[MazdaMatt]

Thanks for your insite, Dave. I think that the water injection would not be problem. It is very common in industry to have water sprayers and foggers that survive all sorts of extreme conditions. Any manufacturing magazine will have ads for such nozles. Your idea of lubrication issues is definately valid. I imagine that the concept of lubricating this engine would have to be a complete re-think because of different operating temperatures and such.

Do you suspect that maybe the complete lack of news aside from the intro article is due to success, and not failure? Getting an engine like this to work flawlessly is not a 6-month endeavor. Getting it to industry is more like a 5-year endeavor.

And what about the ECU side of things? There has never been study on how to efficiently do the water injection timing/duratoin because it has never been done. Bruce can't ride on the backs of a hundred years of engineers on this one. Again, not a 6-month endeavor.

I have some faith in this one... but what's the difference between a clever idea and a good idea? Good ideas sell.

[jamesqf]

Originally Posted by Big Dave

BTW, the big drawback to a Stirling engine is the size and complexity of the machinery required for a given amount of power. To make the power of a chainsaw engine, a Stirling would have to be the size of a big US V-8 SUV engine.

Not so. In fact, if you do some searching, you'll find that Ford & others had them working in cars back in the '70s. The basic problem with the Stirling engine isn't size (that's only when you have a low temperature difference between hot & cold sides), it's that it takes a while to start up, and doesn't easily change speed. Those are obvious drawbacks for a car's sole powerplant.

If instead you have a Volt-like system where the primary drive is electric, and the combustion engine only comes on to add range, then the startup time doesn't matter. The Stirling engine (or gas turbines, fuel cells, etc) become much better alternatives for this sort of system.

[MazdaMatt]

Are you just bored? Or was that a comment on his design in some obscure way?

[Vince-HX]

the six stroke idea is interesting but i'm leaning towards converting a normal ICE to a Miller cycle.

Have sent out a few emails about getting a custom cam ground for my Z1 engine but haven't had any replies yet.

[trikkonceptz]

Imagine taking that same 6 stroke concept and adding electronic valves, eliminating the need to use cams, and oiling valves, etc ... plus it would make it infinately easier to tune.

[CobraBall]

Bruce patented the 6 stroke engine in 1981.

<http://www.google.com/patents?id=gP02AAAAEBAJ&printsec=abstract&zoom=4&d q=Crower+stroke#PPA3,M1>

IF you are ADD and/or sleepy - DO NOT ATTEMPT to read this patent.

ABSTRACT
An internal combustion engine having at least one cylinder, the at least one cylinder having intake and exhaust ports, the engine comprising: a slidably and rotatably disposed camshaft; a cam and follower arrangement including cam lobes disposed on the camshaft, for controlling the intake and exhaust ports, each of the cam lobes having multiple lift surfaces which are shaped to provide at least two different periods of time during which the intake and exhaust ports are open; and, apparatus for axially displacing the camshaft during operation of the engine, whereby the different periods of time may be selected in accordance with engine or vehicle speed.

...and this is just the opening paragraph. Counting drawings it is 12 pages L O N G.

In aviation past the J-79 jet engine on the KC-135 used demineralized water injection for 120 seconds/6000 gallons on takeoff to increase thrust. Demineralized to prevent mineral deposits. IMHO the water was converted into noise.

[metromizer]

Originally Posted by Vince-HX

Have sent out a few emails about getting a custom cam ground for my Z1 engine but haven't had any replies yet.

My experience is to not send emails to performance shops... most of the so called 'performance shops' that are email savy are actually virtual manufacturers who make nothing, they are just drop ship businesses run by some guy(s) with computers out of a small office. You want someone who will take on a project for custom cam work.

The guy who grinds my race cams (Dema Elgin) doesn't have time for email. I need to take time off work and go see him in person, bring my own blank and tell him what I'm looking for... and we've done so oddball grinds and he does know his stuff.

Webcam (closer to you) also has great technical support (phone), and has ground a custom cam for me.

[jonr]

Why not just do direct injection of water instead? Would be great for high output race engines where heat/detonation is a problem.

For normal use, I'll take variable intake valves (Atkinson cycle).