Are stages 2-3 and 1-4 adiabatic in the OTTO cycle?

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In summary, the graph of the OTTO cycle in the link provided shows that stages (2-3) and (1-4) are isochoric (constant volume) and not adiabatic. Adiabatic and isentropic processes are essentially the same, however, not all adiabatic processes are isentropic. The adiabats on the diagram are represented by stages (1-2) and (3-4), while the other two stages are isochoric.
  • #1
JakePearson
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hey guys, just wanted to know, in the graph of the OTTO cycle in the link

http://www.qrg.northwestern.edu/thermo/design-library/otto/Otto-Pv-diagram.gif

are stage (2-3) and (1-4) adiabatic or not, if so why are they

the reason i ask is that i have a graph showing that these stages are adiabatic, however, adiabatic processes are where no heat is exchanged QIN = 0
 
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  • #2
Adiabatic and isentropic are one and the same thing. The adiabats on your diagram are 1-2 and 3-4. The other two, 2-3 and 1-4 are isochoric (constant volume).
 
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  • #3
kuruman said:
Adiabatic and isentropic are one and the same thing.
Isentropic processes are always adiabatic. Adiabatic processes, however, are not always isentropic. A non-isentropic adiabatic process, such as free expansion of a gas, should not be referred to as adiabatic, in my view. However, I seem to have lost that battle.

AM
 
  • #4
Andrew Mason said:
Isentropic processes are always adiabatic. Adiabatic processes, however, are not always isentropic. A non-isentropic adiabatic process, such as free expansion of a gas, should not be referred to as adiabatic, in my view. However, I seem to have lost that battle.

AM
Thanks for pointing out the subtle difference. I should have confined myself to answering the original question instead of trying to generalize.
 

1. What is an adiabatic process in the Otto Cycle?

An adiabatic process in the Otto Cycle is one where there is no heat transfer between the working fluid and its surroundings. This means that the system is thermally isolated and does not exchange heat with its environment.

2. How does the Otto Cycle work?

The Otto Cycle is a thermodynamic cycle that is used in internal combustion engines. It consists of four processes: intake, compression, power, and exhaust. In the intake process, the fuel and air mixture is drawn into the cylinder. In the compression process, the mixture is compressed, which increases its temperature and pressure. The power process is where the spark plug ignites the compressed mixture, causing it to combust and expand, creating mechanical energy to power the engine. Finally, in the exhaust process, the waste products are expelled from the cylinder.

3. What is the efficiency of the Otto Cycle?

The efficiency of the Otto Cycle is determined by the compression ratio, which is the ratio of the volume of the cylinder when the piston is at the bottom of its stroke to the volume when the piston is at the top of its stroke. The higher the compression ratio, the higher the efficiency of the cycle, as more energy is extracted from the fuel-air mixture.

4. What are the advantages of using the Otto Cycle in engines?

The Otto Cycle is widely used in internal combustion engines due to its high efficiency, low emissions, and low cost. It also allows for a smooth and continuous power output, making it suitable for use in vehicles and other machinery.

5. How is the Otto Cycle different from the Diesel Cycle?

The main difference between the Otto Cycle and the Diesel Cycle is the type of combustion that takes place. In the Otto Cycle, the fuel-air mixture is ignited by a spark plug, while in the Diesel Cycle, the fuel is injected into the hot compressed air, causing it to self-ignite. This results in higher efficiency and power output for the Diesel Cycle, but also leads to higher emissions and a more complex engine design.

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