Thermodynamic Study Into Rotary Internal Engine

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ABSTRACT In modern technology era, fuel consumption always has been main topic as the source of fuel is decreasing day after day. Many research and experiment has been made to improve the performance of the engine consequently will reduce the fuel consumption of the engine. A lot of development was made from the intake stroke until the exhaust stroke such fuel injection and compressor to increase air fuel ratio before injected to the engine. There are many type of engine has been produced nowadays which are reciprocating engine, diesel engine and rotary engine. Ideally the performance of the rotary engine is higher than reciprocating engine but the rate of unburned fuel in rotary engine is higher than reciprocating engine. The project was done to investigate the flow field of the rotary engine, fuel concentration and fuel injection near the spark plug, and the pressure and temperature distribution in the rotary engine.

The methodology to the project was simulate and calculate using computational fluid dynamic software which are GAMBIT and FLUENT. The project was assumed as steady state problem since in order to do dynamic mesh; a lot of consideration must take to finish the task. In GAMBIT, the geometry of the rotary engine was built until meshing task. After that, mesh file was exported into FLUENT in order to declare boundary condition, operating condition, type of turbulence model, and material properties. After simulation was done, the result on temperature, pressure and density has been recorded into data and translated it into graph. The graph was compared to theoretical and journal that related to this project.

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1.1. Overview 1.1.1. Background Felix Wankel, German Engineer produces a great rotary engine on February 1, 1957 after 6-years working on this engine. Basic idea is almost same compare to 4-stroke engine. The Wankel rotary engine is a fascinating beast that features a very clever rearrangement of the four elements of the Otto cycle that is intake, compression, power and exhaust. One great advantage is its high operating speeds that allow the engine to produce twice as much power as a reciprocating engine like Otto cycle at the same weight.

Figure 1.1: Complete cycle of Wankel rotary engine [1]

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The advantages of this rotary engine are its compactness, higher engine speed, inherent balance, and smoothness. The disadvantages are its sealing and leakage problem, lower efficiency and higher unburned hydrocarbon emissions resulting from the flattened combustion chamber shape. As mention before, the flow field in the combustion chamber and the fuel concentration around the spark plugs should be optimized in rotary engine in order to improve their fuel economy.

1.1.2. Motivation The motivation for this research is due to ideology of the Wankel rotary engine which is capable of producing higher efficiency and performance compare to Otto engine. Nevertheless, the flaws on the Wankel rotary engine especially on the flow field in the combustion chamber and fuel concentration around the spark plug in this rotary engine has rised the issue on the optimize on the engine performance.

Typically, each stroke in rotary engine are separated by the rotor within the chamber. This rotor is shaped like a triangle whose sides have been curved outward to allow for a better seal against the chamber wall. The rotor is set up on an eccentric cam which allows for the rotor to have all three of its corners touching the chamber wall at all times. For an example on one of the Wankel engine, Aixro XR 50 that produced maximum power 48 horsepower (hp) when the engine is running at about 8500 rotations per minute (rpm) [11]. Compare to any piston engine is out on the market today, a single cylinder capable to produce 12hp. This

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means a single rotary engine can produce quadruples horsepower than a single piston when comparing to their weight rotary engine only...
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