Rolls-Royce is understood for lots of issues, however daring technological weirdness usually isn’t certainly one of them. That’s why it’s so stunning that they made an engine that, when described, looks as if a string of probably the most unlikely adjectives you’ll be able to hyperlink collectively: a Wankel with two separate rotors (however not a twin-rotor) Diesel made by Rolls-Royce.
I didn’t even understand Rolls-Royce experimented with rotary engines, not to mention Diesel rotary engines, however that’s precisely what they have been doing within the late 1960s and early 1970s. The objective for these engines wasn’t the wildly-expensive luxurious vehicles we usually affiliate the Rolls-Royce identify with, however really have been for his or her army automobiles division.
An article within the December 1970 version of Autocar describes the engine intimately, and it’s fascinating. It’s a Wankel rotary with two rotors, however the two rotors should not co-axial as in a conventional twin-rotor engine. As a substitute, it’s mainly like two siamesed rotary engines, one atop the opposite, with the decrease rotor and combustion chamber considerably bigger.
It’s because the engine is a two-stage engine, with the decrease, bigger rotary engine performing as a compressor for the higher engine, which is the one that really produces energy.
The Wankel engine can work instead of a traditional supercharger or turbocharger to compress the air-fuel combination as a result of a rotary engine is inherently a positive-displacement machine—basically, which means the consumption chamber has a bigger quantity than the exhaust/discharge chamber, so the combination inside is compressed.
Within the case of the Rolls-Royce Wankel Diesel, the fuel-air combination is first compressed by the decrease rotary, and the output of that engine (which might be just like the exhaust valve of a traditional rotary) sends the compressed diesel/air combination to the consumption of the smaller higher rotary engine, the place it’s compressed to ignite like an everyday diesel engine.
Rolls-Royce appears to have spent loads of vitality and assets on determining how you can clear up apex seals points and different technical hurdles, and ended up producing at the least 4 check engines, not counting the modified NSU Wankel they used as a testbed:
The primary Rolls—Royce growth engine was the R1 which was conceived purely as a analysis instrument. With a compressor stage of 1,126 c.c., and a combustion stage of 500 c.c., it produced over 50 bhp and achieved particular gasoline consumptions of higher than O.5lb/bhp/hour. Amongst different issues, it was used to develop the very best inter—porting association between the 2 levels.
The R2 engine was the choice three-stage structure, constructed however not investigated intimately. R3 refers to a combustion stage solely, which is getting used as a fundamental unit to construct up a variety of engines; it has a displacement of 1,216 c.c., and has produced 180 bhp at four,500 rpm below check circumstances.
The remaining engine of which particulars could also be given is the two—R6. This can be a army engine fashioned of two banks of a two—stage engine. Every excessive strain (combustion) stage has a displacement of 1,265 c.c., and is fed by a low-pressure stage of three,250 c.c. The design energy is 350 bhp at four,500 rpm, for a weight of 939lb-a spectacular power-to-weight ratio for a diesel.
To minds and ears used to gasoline engines, 939 lbs for a 350 horsepower engine appears lower than “spectacular,” nevertheless it appears to be like like a contemporary GM Duramax V8 Diesel makes about 330 hp from round 850 lbs, so, actually, for the time that’s fairly rattling good. Diesels want a lot heavier crankcases to face up to the excessive compression, so that they are usually heavy.
It doesn’t appear to be the Rolls-Royce twin-rotor Diesel Wankel really ever made it into manufacturing, even on army automobiles, and I do not know if Rolls ever had some engineer feverishly planning a Diesel Wankel Silver Shadow, however I actually, actually wish to think about it.