Mart, 231 g/kWh makes it look even better than 235, doesn't it? That's a good figure when you compare it to car engines. No comparison with "Continencoming" :-D
I am neither a technician nor an engineer, just an interested layman, by the way :-)
You wrote that 2-stroke engines are always less efficient than 4 stroke engines. That's what I thought , too until lately. But by now I know that the most efficient piston engine of the world is a 2 stroke turbodiesel. Look here:
http://en.wikipedia.org/wiki/Wärtsilä-Sulzer_RTA96-C 163 g/kWh at best economy... just unfortunately this (ship diesel) baby would be too heavy to be built into even an A380 :-) It has valves, however. Maybe you can tell me how that works...?
But anyways, the problem with traditional 2 stroke engines is that air (and with gasoline engines: fuel) have to go through the crank case and than push out the burned gases of the cylinder - with more or less losses and a lubrication in which the oil is lost/burned. The deltahawk diesel, however, has an oil filled crank case, just like a 4 stroke engine. The fresh air is being pumped in by a supercharger (in the deltahawk case combined with a turbocharger). This overcomes the oil loss. Fuel loss isn't an issue, anyways, because a diesel injects its fuel only when the piston is up. I think this kind of engine does have some potential. Especially in aviation. Why?
1. It is simpler than a 4 stroke turbodiesel --> less error sources, cheaper to build and overhaul (important with our low numbers of engines sold in aviation, which makes us always more expensive than the road traffic folks!), possibly easier certification
2. It (should) have a better power/weight ratio than a 4 stroke. Thus you can possibly (as in the case of delta hawk) also save the reduction gearbox (with airplanes) and run the diesel engine at rpms that are more efficient for diesels, anyways
3. There are no exhaust emission standards in aviation (yet) which might be a bit tougher to fulfill with these engines
What do you think?
How about that Wilksch diesel? Do you know, how that works? I just browsed through their homepage, but I didn't really understand it. It has overhead valves like that ship diesel, doesn't it?
Anyways, 2 stroke or 4 stroke, I quite agree with you that diesel engines have good potential for aviation. They may be heavier than turbines, but then, much more efficient.
Simon