Rotary Engines

Estimated Reading Time: 4 Minutes

Hey, another car post! I should just make this a series or something.

As you may know, a car engine requires a mixture of air and fuel in order to run – the two are formed into a mixture, at which point they enter the engine, are compressed, ignited, and leave the engine. The force of the ignited gas’ explosion within the engine is what ultimately creates the power from that engine, the power ultimately used to move the car. This cycle can briefly be described in four words – suck, squeeze, bang, blow(incoming 12-year-olds). While this process is typically done using pistons within cylindrical chambers to compress the air-fuel mixture (hence the usage of terms such as four-cylinder to denote engines), it can also be done an entirely different mechanism, and that is the premise of the Wankel rotary engine (expect more 12-year-olds).

Initially dreamt up by German Felix Wankel(pictured above) in the 1920s, first built by him in the 1950s, and improved upon by Hanns Dieter Paschke, the rotary engine, as previously discussed, uses the same cycle of compression and ignition that a piston-powered car would use, although, in lieu of pistons, this design utilizes a triangular(some have compared it to a Dorito) rotor that spins around at incredible speed and is in constant contact with the edges of a chamber, creating three separate chambers in which the process occurs. The opening up of any one of these three allows the air-fuel mixture to flow in, and as the rotor continues to spin, the mixture is compressed against the walls of the

As you may know, a car engine requires a mixture of air and fuel in order to run – the two are formed into a mixture, at which point they enter the engine, are compressed, ignited, and leave the engine. The force of the ignited gas’ explosion within the engine is what ultimately creates the power from that engine, the power ultimately used to move the car. This cycle can briefly be described in four words – suck, squeeze, bang, blow(incoming 12-year-olds). While this process is typically done using pistons within cylindrical chambers to compress the air-fuel mixture(hence the usage of terms such as four-cylinder to denote engines), it can also be done an entirely different mechanism, and that is the premise of the Wankel rotary engine(expect more 12-year-olds).

Initially dreamt up by German Felix Wankel(pictured above) in the 1920s, first built by him in the 1950s, and improved upon by Hanns Dieter Paschke, the rotary engine, as previously discussed, uses the same cycle of compression and ignition that a piston-powered car would use, although, in lieu of pistons, this design utilizes a triangular (some have compared it to a Dorito) rotor that spins around at incredible speed and is in constant contact with the edges of a chamber, creating three separate chambers in which the process occurs. The opening up of any one of these three allows the air-fuel mixture to flow in, and as the rotor continues to spin, the mixture is compressed against the walls of the chamber until it arrives at the spark plugs, which ignite the mixture as they would in a standard piston engine, forcing the rotor to continue on its journey until the mixture is expelled as exhaust gases and the chamber is refilled with more of the air-fuel mixture. This process occurs three times at once and continues until the engine is shut off.

As with anything, the rotary engine layout has its inherent benefits and drawbacks. For one, this setup allows engines to produce great amounts of power in a rather compact package. For example, the naturally aspirated(no turbocharger or supercharger) 13B-REW found in several of Mazda’s cars is, as the name would imply, about 1.3 liters in displacement, but produces about 230 horsepower – which equates to an absurd number of specific output(hp per liter) – for context, the latest Honda Civic Si, which has a 1.5 liter turbocharged engine, produces 205 hp. In addition, these engines are not prone to sudden catastrophic failure, and, if well-maintained, can be very reliable. However, at the same time, their gas mileage is not great, and in addition, they need to burn oil in order to lubricate their seals, which themselves can wear quickly – after all, they are rubbing against a wall 24/7.

In the decades since the rotary’s inception, the primary adopter of the technology has been Mazda. Since the creation of the first Mazda Cosmo sports car, rotary engines have found a home within the walls of this Japanese company. Automobile icons such as the RX7 and RX8 have been popularized and praised for the unique characteristics of their engines, although since the RX8, which lasted until the early 2010s, ended production, the rotary engine has yet to see a comeback. Mazda has confirmed that it will most likely be used as a range extender for a future hybrid model, although other details are scarce. At least fans of this engine(myself included) can breathe a sigh of relief in knowing that it will return someday.

-Allen Parayil

Author at StemTalksNC

Sources:

https://auto.howstuffworks.com/rotary-engine1.htm

https://nationalspeedinc.com/advantages-and-disadvantages-of-a-rotary-engine/

https://www.popularmechanics.com/cars/car-technology/a7103/mazda-wankel-rotary-engine/

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