# How to read the Otto cycle TS diagram

## What is meant by the Otto cycle TS diagram?

The diagram that shows the variation of the temperature and the entropy properties of the working substance/ fluid during various processes of an Otto cycle is called the Otto cycle TS diagram

### Theoretical Otto cycle TS diagram

In the TS diagram, Entropy “s” is represented in the X-axis and the Temperature “T” in the Y-axis. so at any point on the TS diagram we can know the respective temperature and the entropy of that point easily.

With respect to the TS diagram

• Line 1-2 represents the adiabatic compression process of the air. During this process, entropy remains constant i.e. S1=S2 and the temperature increases from T1 to T2
• Curve 2-3 represents the constant volume heat addition process. During this process air temperature increases from T2 to T3 and the entropy increases from S2 to S3.
• Line 3-4 represents the adiabatic expansion process of the air. During this process, S3=S4 and the temperature decreases from T3 to T4
• Curve 4-1 represents the constant volume heat rejection process. During this process air temperature decreases from T4 to T1 and the entropy increases from S4 to S1, thus air returns to the initial state and the cycle repeat as discussed in curve path 1 to 4.

If you want to know the actual and the theoretical PV diagram of the Otto cycle then click/tap here

If you want to know more about the Otto cycle and its efficiency then click/tap here

If you want to compare the Diesel cycle with the Otto cycle to see which is better then click/tap here

## references

• Thermal Engineering by R.K Rajput
• Internal Combustion Engine by M.L Mathur, R.P Sharma

https://en.wikipedia.org/wiki/Otto_cycle