I just read this great article on Jalopnik and thought I'd share with you guys. The idea is a rotary engine in a 2-stage process, with the first rotor acting as a compressor for the second (power) rotor (think supercharger).


Link to Jalopnik article

 

Looks like a great idea in concept, but the hurtles of lubricating the "compressor" rotor apex seals will be the main issue, on top of heat dissipation from the exhaust side, you would be feeding heated fuel/air mix to the intake as there would not be enough of a cycle to cool the face of the rotor. Also, if you look closely, there is no compression on the "compressor" side, making it very inefficient, I don't think the vacuum from the speed of the rotor would be efficient enough.
Maybe I'm overthinking it...

 

I wonder how difficult the lubrication would be, since there's no ignition in the compressor rotor. The lubricant might not burn away with each rotation, although maybe at the exhaust. I figure same oil injection method would apply, but maybe at a lower rate because of less burn-off.

The first rotor is filling the large chamber and then squeezing it into the chamber of the small rotor, so there is some compression going on. Looks like 3:1 volume difference by eye.

There will be some cooling during the expansion process from exhausting rotor 1 into rotor 2 (again, ~1:3 volume increase). How much resulting cooling may be negligibly small. Getting rid of the exhaust does seem inefficient in this method though, definitely. I think the long duration of the exhaust spending in the engine will definitely be bad for heat dissipation, like you said.

 

So that's their take on a compression ignition Wankel that can run on diesel.

It definitely looks difficult, as it's hard to make a Wankel with high compression ratio. Renesis already has a high compression ratio for a Wankel. I think Mazda's SkyActiv-D diesel technology needs a compression ratio of 14:1 or so, and they claim that to be the diesel engine with the lowest compression ratio in the world.