I see inefficiency written all over that design. Saying nothing about costs to build it. And why even bother? The old tried and true is a much better design.
cilinderoffset : yes that's the way to reduce side-friction during expansion and alows a bigger ( but more accepatble ) side-friction during compression.
Talking about motorbikes ( driving a Yamaha Fazer myself ), this dutch dieselbike is also free-piston.
Piston rings rely on an oil film to avoid metal-to-metal contact. If there is no oil, the piston ring will locally melt and seize to the cylinder wall. That's what happens when a normal engine is run without oil.
Also, piston rings rely on an oil film to complete the seal. The tiny oil film blocks the path for gases to escape past the piston ring.
And ... Piston rings rely on gas pressure from above to work its way in behind the piston ring and force it against the cylinder wall. The more gas pressure there is, the more pressure the piston ring pushes against the wall. The initial tension is only to roughly hold it in the right position to get this process started.
The friction due to side loading of the pistons is much lower than the friction due to the pressure needed to maintain proper piston ring seal. Many racing engines use only a single compression ring instead of two, to cut down on piston ring friction. BUT, low oil consumption and maintaining compression for good cold starting and maintaining low piston ring leak-down for lower emissions are not priorities in those applications.
AND ... Piston rings need a little bit of oil to help transfer heat. If you don't do that, something melts, and the engine goes boom.
Piston ring without oil = seized engine. If clearances are made exceptionally large and the speed is kept low in order to avoid seizure, metal-to-metal contact without lubrication = very quickly worn out.
Wankel rotary engine apex seals have a tough situation because they also have compression/combustion space on both sides of them. Look how long it took to develop Wankel engines that seal properly ... AND ... they are designed to deliberately use a small amount of oil, because the apex seals will not last long without it!
Does friction-free pistons require less ( or none ) lubrication-oil and therefor limit ( exclude )the problems that conventional 2-stroke diesels ( Detroit ) have (had )?
The rings and cylinder bore have been refined over the years to cut down on drag and wear and oil usage. Still, there is a need for oil to lubricate if you want a long operating life.
You're posting about details that you should already know if you are building this thing. Doesn't matter though since you haven't answered a very simple question. How will you ensure the piston/swingbeam and engine block don't expand at different rates causing the piston to contact the bore damaging or seizing the engine?
absolutely right about de Wankel apex seals. The space to mount a seal between the compressionchambre and expansionchambre is awful limited. Blow by, however, is not so critical, you simply loose power . Blowby in a conventional is worse, it's towards the crankshaft.
The biggest problem in a Wankel is that the rotor of a wankel is completely closed in and is continouisly building up heat that must get out through these axep seals. Ordinary pistons don't have this major problem.The intake piston is extra cooled by the incoming air, the outletpiston can be forced cooled by oil. The opposed piston Junkers and GM were done that way.
I believe oil is injected into the wankel in small quantities by an airpump . Don't know if the engine meets emissions-regulations, we don't see them a lot in Europe.
Wankelrotor can be considered as a free piston, there is no side thrust. But this rotor is continuously heating up.
Machining a trochoidehouse within tolerances is not really conventional. What about honing, lapping. ?
The Wankelhouse has an unequal thermal expansion. Its continously heated on the expansion side and cooled on the compressionsite.
"Blow by, however, is not so critical, you simply loose power."
If it happens under load, it can result in detonation in the next chamber due to the unexpectedly high VE. Detonation under load is generally disastrous, breaking the tip seals or the dowels that hold the rotor housings in place. Pragmatically, compression loss only happens under load if there were other major problems anyway.
Cooling is not that difficult, oil is used for the rotor and the water jacketing is designed so that the combustion space sees the coolant first. They've been mass-producing them continuously for 44 years, I'd say they have a handle on the major issues. The most recent spate of problems seems to be a double-shot of excessive reduction of the injected oil, and improper driving habits.
In all the designs including the one posted; am I the only one, but I see lots of parasitic loss and just lots of rotating mass and parts, not much less than what is already in our in-efficient SICE's (or non S) now. Whats your estimated efficiency rating of this? is it multi fuel? What's it's O2 or Nox output? has any of that been tested?
yes you right izzmus, blow by in the exhaust chamber is not so crital, blow by in the compression is.
Cooling is not difficult but very, very omportant.
Further : It seems that Ford also is playing around with a free opposed piston engine. They also lubricate their pistonrings with a injected oilmist according to their dec,2005 patent :
Why is there suddenly so much interest again in the old opposed piston engine ? We have Bill putting millions of dollars in it and also carcompanies studying the item ?
I also noticed the name Peter Hoffbauer again ( from ecomotors and formal master of the first VW-Golf diesel) on this patent.
Are the Russians going toroidal ?
Billonaire Mikhail Prokhorov has made an investment that involves a total outlay of 150 million euros.
It seems to be a hybryd toroidal , similar like the omega-engine from Bradshow.
I personally like the design of toroidal piston engines. However, I find it pretty complicated compared to the standard engines, which means that it might be more expensive to make.
The problem is that all the current knowledge(acquired during many years) is based on manufacturing parts for standard piston engines, which, even if it may not be the best solution, will make it cheaper to make, and make it harder for other technologies to be as competitive regarding the manufacturing costs.
Concerning the Russian car with the toroidal piston engine, I don't find the performances and fuel saving very interesting. 130km/h and 3.5l/100km in a small car is something that has already been done in the past with no technology at all (check out the Citroen AX with the 1.4l diesel engine).
Another pretty animation. Do you have any links to examples of running toroidal engines? "Running" animations and running physical engines are two very different things.
