Do Rotary Engines Have Valves?

Arthur T Knackerbracket has processed the following story:

Rotary engines (also known as Wankel engines and Wankel rotary engines) are quite different from piston or "reciprocating" engines. One of the distinguishing features is that they don't need valves to operate. That's to say, the Wankel rotary engine design doesn't have valves - but quite a few rotary engine designs have incorporated them. Both rotary engines and piston engines utilizeinternal combustion and share the same phases of intake, compression, power, and exhaust. But beyond this similarity, they are very different in design and operation.

The work done by a rotary engine doesn't need to be convertedinto rotational motive power for use by propellers or transmission, as is the case with piston engines.As a result, they are considered more efficient by some metrics and require fewer moving parts to function. The first rotary engines were primarily used for aircraft during World War I, but the design was abandoned due to flaws and inefficiencies.

In 1954, German engineer Felix Wankel invented a new design for an automobile rotary engine for the German car and bike company NSU. After prototype testing by NSU in the following years, they entered into an agreement with Japanese company Mazda to develop Wankel rotary engines for its cars. The first Mazda cars with rotary engines werelaunched in Japan in the 1960s before crossing the Pacific to America in 1971. Remaining one of the few companies that stuck with the rotary engine design, Mazda has, over the years, developed some of the most innovative enginesof this type.

These engines create power by combusting a mixture of compressed air and fuel within a chamber or cylinder, translating the displacement of the rotor or piston into motion. Wankel rotary engines feature anequilateraltriangularrotor with convex edges in an ovaloid chamber or rotor housing(the shape is anepitrochoidwhere the long sides of a symmetrical oval have two curves like a slight figure eight).

As the triangular rotor moves through the chamber, all three of its apexes are in constant contact with the housing (thanks to rotary engine apex seals), creating three gas volumesthat are isolated by the rotor. There are two ports on the same side of the figure eight housing, with the top one for intake of fuel and air and the bottom one for the exhaust of combusted gases. Intake can be assisted by a superchargerpushing air into the chamber, while exhaust can be assisted by a turbochargerpulling air out of the chamber.

As the leading edge of the rotor passes the intake port, it creates avacuum, inducing (or pulling) air and fuel into the chamber. The rotor's motion then compresses the air and fuel, lit by a spark plug (two in Mazda's design), further propelling the rotor along its path and sending the combusted gases out of the exhaust port. The rotor is attached to an eccentric output shaft (containing lobes not on the center of the shaft) via a gear, and as it rotates, the shaft produces a torque that's used to turn the transmission.

So far, we've explained the most basic Wankel rotary engine, but Mazda - the company that popularized it - has developed several variations over the years. One improvement included a concave pocket on each of the three convex edges of the rotor, whichincreased the amount of volumewithin the epitrochoid housing.

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