Engine Cycles: Otto, Diesel and Carnot

[jamesb87]

Problem / Question

1)Study the engine cycles for the Otto cycle, Diesel cycle, the Carnot cycle and the standard air cycle. Explain the principles of how they work why they are different and the benefits and disadvantages of each of the systems.

I have wrote about the otto cycle practically (four stoke engine how it works) I am now writting about the thermodynamic principle of it. I have shown a PV diagram and wrote down the four stages

1 to 2: Isentropic compression process

2 to 3: Heat addition at a constant volume

3 to 4: Isentropic expansion process

4 to 1: Heat rejection at constant volume.

How can I expand on this...

Any help would be much appreciated.

Regards,

James

 

[jbsteele]

Answer: The Otto cycle is a thermodynamic cycle that describes the functioning of a typical spark-ignition internal combustion engine. It is based on the four strokes of the piston – intake, compression, power, and exhaust – and the two isentropic (constant entropy) processes of compression and expansion. The Otto cycle is used to determine the efficiency and performance of an engine, particularly in automobiles. In the first stage of the cycle, the intake stroke, the piston moves downward, drawing a mixture of air and fuel into the cylinder. This is followed by the compression stroke, in which the piston moves upward, compressing the air-fuel mixture. During the power stroke, the compressed air-fuel mixture is ignited by a spark plug, causing the temperature and pressure in the cylinder to rise. The burning fuel expands, forcing the piston downward and producing mechanical energy. Finally, during the exhaust stroke, the piston moves upward, pushing the exhaust gases out of the cylinder. The two isentropic processes of compression and expansion are important for obtaining maximum efficiency from the engine. In the compression stroke, the air-fuel mixture is compressed adiabatically (without exchanging heat with the environment), increasing its temperature and pressure. The heat generated by the combustion of the fuel is then used to do work in the power stroke. In the expansion stroke, the exhaust gases are expelled isentropically, cooling them and converting more of the heat energy into mechanical energy. The Otto cycle has a number of benefits and disadvantages. On the plus side, the four-stroke design is relatively simple and efficient, making it well-suited for use in automobiles. The isentropic compression and expansion processes also help to increase the efficiency of the engine. On the other hand, the four-stroke design can be less efficient than other types of engines, and the spark plug can be a source of maintenance problems. Additionally, the Otto cycle is limited to spark-ignition engines, and thus cannot be used in diesel or other types of engines.