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Wankel (Rotary) Engine: Otto Cycle

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Wankel (Rotary) Engine: Otto Cycle WANKEL PARTS Knowing the basic components in the engine is vital to knowing how the engine (ROTARY) functions. The diagram below labels the important parts of the engine that are ENGINE: OTTO mentioned later. Intake Port CYCLE Outlet Port WHAT IS IT? Fixed Gear Output Shaft The Wankel engine is an internal combustion engine that uses the four strokes of a typical Otto cycle (intake, compression, combustion, exhaust) to create kinetic Housing energy. This kinetic energy is converted into rotational energy used to spin the cars transmission and ultimately propel the car. Spark Plug Figure 1: Parts Unlike it’s piston-driven counter-part, the Triangular Rotor Wankel engine directly converts pressure into rotating motion. Ø INTAKE PORT: The entry point for the gas into the engine. HISTORY Ø OUTPUT SHAFT: Moves the rotational The Wankel engine was designed in 1951 by kinetic energy from the rotor to the rest German engineer Felix Wankel for NSU of the car. Motorenwerke AG (NSU), a German Ø TRIANGULAR ROTOR: Divides the automobile manufacturer. The initial design chamber into intake, compression, and had the housing and the rotor of the engine combustion areas and supports the move on independent axes. This was later energy of the system and the engines changed so that the housing remained fixed gear set. (This is the version covered in this article). Ø SPARK PLUG: Provides the electric energy used to combust the compressed The engine saw its first commercial use in fuel. Norton Motorcycles, a British motorcycle Ø HOUSING: Contains the combustion company. It then moved on to cars in 1961 reaction and guides the motion of the when Mazda partnered with NSU to make triangular rotor. rotary engines a standard in commercially Ø FIXED GEAR: Gear attached to the available vehicles. housing to ensure the correct movement Currently, the engine sees use in of the rotor within the housing. motorcycles, racecars, airplanes, and even Ø OUTLET PORT: Exit area for ignited go-carts. gasoline. HOW DOES IT WORK? cycle re-enters during intake, the housing is extended to touch the edge of the rotor. The engine functions in a four step process: INTAKE, COMPRESSION, IGNITION, Unlike traditional engines where the amount EXHAUST. During these four stages, the of fuel entering the engine is controlled by a engine converts gasoline into energy that the camshaft (valve-operating component on car uses to move. These stages are known as piston engines) synced with the rest of the strokes, making the Wankel engine a 4- engines motion, fuel enters into a Wankel stroke engine, similar to the conventional engine based on the rotation of its rotor. piston engine. COMPRESSION A Wankel engine differs from a traditional Compression is piston engine because of the unique design the second of the housing and rotor. As opposed to the stroke in the single piston-head surface which typical cycle. In this engines have, the Wankel engine’s rotors phase, the rotor have three sides. This allows three actions to forces the take place during one rotation of the rotor. mixture into a PROCESS tighter area of the housing, The following process tracks the flow of creating a gasoline as it enters the engine until it is pressurized combusted and exits it. It is important to air/fuel mixture note however that these stages, as was Figure 3: Compression (Figure 3). mentioned before, happen simultaneously. It is important INTAKE that the fuel be compacted at this stage, because it will not ignite if it isn’t at the The first stroke in correct pressure. the cycle. During this phase, a drop in IGNITION pressure caused by Taking the the rotor’s motion compressed mixture draws in an air/fuel from the previous mixture (Figure 2). stroke, the third This mixture is stroke, ignition, drawn around the ignites the mixture rotor and forced into (Figure 4) creating the second stroke of the exhaust and the the cycle. energy used to move Figure 2: Intake the rotor. In order to ensure that none of the exhaust from the previous To compensate for Figure 4: Ignition the odd area needed to contour to the shape and position of the the engines absence of highly stressed rotor at this point, the spark plug(s) need to components such as camshafts or be positioned in a way to ensure the mixture crankshafts. burns evenly. The problems with the Wankel engine come This is the most important stage in the cycle from the seals at the edges of the triangular because it determines the speed and power rotor. These edges, by design, are in outputted by the engine. constant contact with the housing of the engine. The material therefore has to allow EXHAUST the rotor to move without restricting The fourth and final movement and prevent any leaks between stroke of the Wankel the three sides of the rotor. This is especially engine process is the hard to maintain as the seals experience expulsion of the wear due to engine use. exhaust through the outlet port (Seen on Refrences Figure 5 in black). Singh, Rachender. "The Wankel Rotary The sudden Combustion Engine: Construction & expansion of the now Working." Automobile Infotech. 18 gaseous fuel Apr. 2014. Web. 23 Mar. 2016. mixture forces the rotor back around to "Wankel Engine." Wikipedia. Wikimedia Foundation, 14 Mar. 2016. Web. 20 Figure 5: Exhaust its initial position. The exhaust is drawn Mar. 2016. from the engine to the exhaust system of the car. Wankel vs. Piston Engine While both engines serve the same purpose, there are a number of key design differences between them. For one, the Wankel engine converts pressure directly into the rotation of the output shaft, while a piston engine uses the vertical motion of its pistons to do this. This difference leads to Wankel engines being typically lighter than their piston counter-parts, leading to machines needing light, compact engines (motorcycles, chainsaws) using rotary engines. Additionally, Wankel engines can withstand higher engine revolutions due to the inherent motion of the rotor to the output shaft and .
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