autogyro wrote:Can you explain to this poor ancient engineer how you measure the 'swept' volume of the Mazda rotary and come up with 3.9 liters.
The rotary IS used in current road cars, it is just that most cars still use 19th century ic technology.
How is a two stroke engine even slightly close to a rotary in minimal moving part? It still wastes power doing a silly dance called reciprocation!
The rotary only uses to much fuel because it burns rich to keep the combustion temperatures down for tip seal reasons, it can burn low octane fuel better because of the spread out flame path. To meet the fueling needs, fit a turbo generator with air fuel injection into the exhaust prior to the turbine. This burns the unburnt fuel and other exhaust gasses at a high enough temperature for fuel efficiency and also recovers energy from the generator.
Oh and before you dimiss rotary valves completely, take a look at the Bristol sleeve valve engine in the sea fury we used to fly. 2800hp, the Napier was also very useful. WW2 vintage of course.
The displacement of an engine is the volume of air an engine displaces during one complete engine cycle. For the rotary to complete one cycle, it must do one revolution of the rotor (three shaft revolutions). One revolution of the rotor equals three combustions per rotor, and since Mazda rate their engines by the displacement of one chamber per rotor, the correct displacement will be three times the displacement rated by the method Mazda uses. So the real advantage of the rotary is a big displacement in a small package.
No, the rotary doesn't use "much fuel because it burns rich to keep the combustion temperatures down". It simply suffers from a poor combustion chamber geometry. This results in high heat losses, high HC emissions and a slow heat release rate. Yes, the high surface to volume ratio that cause the high heat losses and the lack of hot exhaust valves offer some advantage in terms of charge quenching which could have some positive effect on octane requirement, but in overall, it doesn't offer any advantages over a piston engine. Which is why all car manufacturers, except Mazda due to non technical reasons in some special models, have decided to stay with the piston engine. The wankel engine was simply the answer to a question never asked; innovation for innovations sake rather than for a real technical reason!
There are also no losses in an engine because of reciprocating motion, and the motion of a rotary engine is partially reciprocating too, that's why they often have counterweights.
Two stroke engines have very few moving parts; piston, piston rings (two or three usually), piston pin, connecting rod and crankshaft. The rotary have the rotor with internal gear, three two or three piece apex seals with apex seal springs, six trunnion blocks, six trunnion washer springs, side seals (six or twelve per rotor), oil seals (two per rotor) and the eccentric shaft. I don't know how you get that to fewer parts, but I sure don't.
The Bristol is a sleeve valve engine, not a rotary valve engine, there's a big difference.
Carlos wrote:There was a rotary valve engine project, the Bishop Rotary Valve, that almost reached F1 in conjunction with Ilmor, a3 L F1 V10 was actually designed and manufactured, unfortunately the F1 rules changed, Article 1.15 in 2004 I think it was - only allowing poppet valve engines:
http://home.people.net.au/~mrbdesign/PD ... echBRV.pdf
There's also a thread on rotary valve engines:
viewtopic.php?f=4&t=3045&hilit=rotary+sleeve+engine
Both well worth reading, if only for reference and F1 historical perspective.
Let me help with the constant comparison between 2 stoke and rotary engines - it's based on the the similarities of both engines using intake exhaust ports rather than poppet valves.
Single cylinder prototype engines were built, there have been several of that kind, but the step from a prototype to a working racing engine is quite long.
