Hi all,
interesting thread. Also interesting how all the old misconceptions of the Rotary prevail!
If you want to get smart about Rotaries in aircraft I suggest to visit the following sites and to join the newsletters.
http://www.flyrotary.com/
http://www.rotaryeng.net/
Especially on the last one you will find a wealth of data and info on and about the Rotary in general and especially if it comes to adaption to aircraft. Also the owner of the list is working on a turbo compound system for the rotary.
Nick mentioned fuelburn.
I think that's not that important. Turbines are lousy at low levels - but they are light. So is the Rotary.
Moving parts - only 3 major parts moving around, not up/stop/down/stop/up/stop/.....(reciprocating...
)
There is no catastrophic failure mode - no valves to break, rods to throw, cranks to shear, pistons to burn.
What it does is loose power, maybe can't restart, .....
Also, a comparison with any piston engine is useless.
It has aspects of 4-stroke and 2-stroke engines, but it is impossible to compare displacements. It is of course a 4-cycle engine, but it is taking the charge around the neighborhood. A piston engine has cylinders and all cycles stay within the cylinder.
At the end of the day it all comes down to how much to you feed it, what do you get out in return.
Rpm comparison is also irrelevant.
Though the excentershaft turns let's say 6000 rpm, each Rotor only does 2000 rpm at this stage (rotors turn at 1/3 excentershaft speed)
At the same shaft/crank speed a piston engine has less time to complete combustion per combustion cycle than in a Rotary.
There was a real Diesel rotary once, built I think by John Deere or Curtiss-Wright: It had a bigger Rotor that was driven as a compressor - feeding the actual power producing rotor with compressed air, so the pressure for diesel-ignition (self-ignition) could be reached - wasn't too efficient...
If you want to just burn Diesel/Jet-fuel you will have to wait a little longer until Mistral,
http://www.mistral-engines.com/
is ready to certify their Kerosine burner!!
It will be spark-ignited. Prototyps are running already.
Their first gasoline-engine is being certified as we speak, FAA to be immediately followed by JAR.
190hp NA,
next year follows the Turbo-intercooled version 230hp,
then a 3-rotor NA and turbo.
After that the K-series (Jet-A/Diesel).
The CEO went through this, because he nearly crashed because of "faulty quality-control at Lycosaurus"!
Also the more powerful the engines become the better the power/weight ratio of the rotary.
Where we are at a concise switchover point from piston to turbine around 400 hp, the Rotary has an easy potential to push this beyond 600 hp.
Of course even the Rotary will never match the power/weight ration of a turbine - but on the other hand it will also never match the $$$/SHP ration of it either!!
Don't bet on the Moller Skycar OR his Rotary any time soon.
So far (...about 30 years now) it has been mainly Vaporware for blind investors!
It is not so big a deal to build your own Rotary.
But it is if you want to make it safe and last!!
Mistral has their hardware flying (Embrey-Riddle operates a Turbo-Arrow on their behalf for R&D....). From their present state of development they project a 3000 hr TBO, at a very low overhaul-cost, compared to other aircraft engines.
Also their engine (or any Rotary for that matter) has a very high safety margin - e.g. the 360hp turbo could be brought up to 420hp easily for "emergency-power" (...for 30 min) if needed. It is recommended to inspect the engine after that, though there should be no reason for any replacements.
A last example:
Mazda won LeMans 1991 with a 4-rotor, non-turbo - outright. The win was such a threat to the rest of the club, that Rotaries where outlawed immetiately!
If you take any LeMans engine apart after the 24-hr race it is ready for a total overhaul or the junkyard.
--- Mazda hardly could find any sign of wear.
that machine developed some 720 hp...
Just read a little into the Rotary, and you will find out what a good engine design it is!
All the old-wife-tales are long solved:
High fuel-consumption - seal breakage - oil-consumption - idle problems, etc. are a thing of the long gone past...
Mistral matches or betters Lycomings fuelburn....
By the way, Citroen built a rotary powered helicopter!!
check this:
http://www.der-wankelmotor.de/Flugze...elicopter.html
And a sexy helo it was!!
Back lurking,
3top
PS:
At the present stage Turbo-Diesels loose their appeal for aircraft around 160-180hp. After this they become too heavy. See the Thielert - the 160hp one is a hit. the "360hp" is up fro mthe planned weight and down to 300 hp. At 600+lbs I prefer the 720Lycoming at 400hp.
Better wait for the Mistral....