Abstract
A rotary engine is one of the ancient internal-combustion engines ever used. These type of engines were designed with an odd number of cylinder per row in a radial configuration. The crack shaft remained stationary throughout the operation. One advantage of this kind of engine is that it is a simple engine that utilizes less moving components. On the other hand, a piston engine or a reciprocating engine is a heat engine that uses one or several reciprocating pistons. The piston engine converts pressure into a rotating motion. A piston engine has the capability to seal the gap in between the pistons and the cylinder, an advantage of this engine compared to a type rotary engine.
The article describes two types of engines; the rotary engine and the piston engine. It examines the variations between these two engines and their different areas of application. The various application of the two type of engines is based on the various cars that the two are installed in. Also, the disadvantages and advantages of the two are explained, where it is determined why the piston engine is most preferred by the auto manufacturers and car enthusiasts. In the article, the engine that fetches most application benefits is described. More precisely, the piston engine has the most application than the rotary engine
Introduction
Rotary combustion engines failed to achieve what piston engines did because of high maintenance engines, the heat problems, and the heavy carbonization problems.
Since the invention of the first vehicle to date, technology has been rapidly changing and upgrading. Different mechanisms have been invented or improved from time to time. The automobile industry has not been left behind on this. With rapidly rising competition among vehicle manufacturers, the pressure to make more efficient vehicles has constantly been rising to win the largest shares of the ever expanding car market (Davis, 1999). This includes fuel consumption, engine torque, as well as efficiency. This led to the upgrade from the rotary to the piston engine.
A. Mazda Rx-7, a miraculous car enthusiast’s dream
The Mazda Rx-7 is a Japanese sports car that was manufactured from 1978 to 2002. The car had come after the Mazda Rx-3 before it was upgraded to the Mazda Rx-8. Perhaps the most inviting thing about this car is that implements the rotary engine. While other car manufacturers quickly disposed of the type rotary engine, a few, however, stuck to maintaining and improving the rotary engine. One of these companies is notably Mazda, which applies this engine in their Rx series automobiles (Whitney, 2003).
Regarding engines, the RX-7 originally included a twin-rotor Wankel rotary engine with a rear-wheel drive and a front-midship design (McCOSH, 2002). Despite the major shift away from rotary engines and the worldwide advisories against this engine-type due to its inefficiency, Mazda proved the world wrong about it with their classic masterpiece.
B. Thesis
How do rotary engines work compare to piston engines?
A. The combustion process
The rotary engine is well known for its high horsepower, better handling as well as its immunity to catastrophic failure. However, this type of engine has often had its downside. The point of discussion, therefore, is whether the rotary engine has failed to match the qualities of the piston engine. This is argued using reported problems such as high maintenance engines, the heat problems, and the heavy carbonization.
How do rotary engines work compared to piston engines?
The rotary engine was an early internal combustion engine with an odd number of cylinders in each row, arranged in a radial manner. The crankshaft remains stationary in operation while the crankcase connected to the cylinders rotates about as a single unit. This type of engine was embraced in the World War 1 era, where the main area of application was aviation. Additionally, it was also preferred in some the early cars and motorcycles (Hege, 2001).
On the other hand, the piston engine, also referred to as a reciprocating engine, is a type of engine that transforms pressure into rotary motion. Most of these reciprocating engines are usually heat-based, although there also exists pneumatic and hydraulic piston engines. Today’s motor vehicles mainly use an internal combustion engine that includes either a spark-ignition system or a compression–ignition system (Davis, 1999).
1. Rotary engine combustion process
The combustion process of a rotary engine has four main stages: intake, compression, combustion, and exhaust. Each occurs in its part of the engine housing. The rotary engine uses the pressure that is created when fuel and the air are burned together. This pressure is contained in a chamber formed by a part of the engine housing that is sealed by a face of the triangle-shaped rotor. The rotor follows a destined path that keeps every single peak of the rotor in contact with the housing. While the rotor is in motion, each of the three gas volumes expands and contracts, which draws air and fuel inside the engine. (Hege, 2001).
2. Piston engine combustion process
The piston engine works in a combustion cycle that incorporates some strokes depending on the type of car. The most common mechanism in the modern world is the four-stroke combination cycle; intake stroke, compression stroke, combustion stroke and exhaust stroke. (Davis, 1999).
Intake stroke: As the piston rotates, it starts from the top, where the intake valve opens as the piston goes down to allow the engine to take in a cylinder containing air and gasoline.
Compression stroke: When the piston pulls back upwards, it compresses the air-fuel mixture thus creating pressure.
Combustion stroke: The moment the piston reaches the top of the stroke, the spark plug emits a spark which ignites the gasoline mixture. The pressure increases rapidly and explodes, thus pushing the piston down.
Exhaust stroke: The piston hits the bottom of the stroke, where the valve opens, and the exhaust leaves the cylinder towards the tailpipe. The engine is then ready for the next cycle, where a fresh mixture of air and gas is taken in, and the cycle is repeated.
B. Real life examples
Rotary engines are not as common today as compared to the beginning of the 20th century. This is not a big surprise comparing its efficiency to the piston engines. However, Mazda, being the only car manufacturer applying rotary engines is a leading example through their RX-series vehicle (Whitney, 2003). Most airplane manufacturers prefer rotary engines due to fewer rotating parts and smoother power transmission (Hege, 2001). Rotary engines are not prone to engine knock, operates with almost zero vibrations, and can reach higher revolutions per minutes compared with a piston engine.
The rotary engine has fewer moving parts compared to the usual four-stroke piston engine. This is because of numerous components in the piston engine such as valves, crankshaft, and piston while the rotary has just a single triangular rotor. Minimizing of these parts transforms into better reliability. Furthermore, all parts in a rotary engine rotate in a continuous manner in one direction unlike the violent and sudden changes in the direction of piston engines. This translates to better power delivery in rotary engines (McCOSH, 2012).
Daily use problems
One major complaint concerning the rotary engine is its huge fuel consumption (Vance, 1999). This is because this engine does not burn oil out of the fault; rather, it uses oil squirters which take small amounts of oil into the fuel to lubricate the engine seal. Car owners incur high costs due to the lower gas mileage of their rotary engine cars (Vance, 1999).Rotary engines have a high torque hence a heavy duty performance. However, this develops into a huge problem due to wearing out of certain parts (e.g. seals as a result of the friction).
In conclusion, despite the reliability of rotary engines regarding smoother power transmission, weight reliability, and high horsepower, these engines require constant maintenance and regular checkups. However, the notable success by Mazda in their RX-series proves that this type of engine is a superb one. Therefore, rotary combustion engines have not failed to achieve what piston engines did because of high maintenance engines, the heat problems, and the massive carbonization problems.
References
Davis, T. (1999, March 5). This motoring century; ROTARY HYSTERIA. Sydney Morning Herald (Australia), pp. 5.
Hege, John B (2001). The Wankel Rotary Engine: A History. Jefferson, NC: McFarland.
McCOSH, D. (2002, March 29). The return of the Wankel engine. The New York Times, pp. 1.
Vance, B. (1999, July 16). Innovative NSU doomed by engine problems. The Ottawa Citizen,
Whitney, T. (2003, February 28). Mazda's RX-8 revives the rotary driving force: Automaker is the only one in the world to offer engine. Ottawa Citizen, pp. C8.
