Replotting an Air Standard Cycle.

Definition

You should replot the process after you change engine parameters, such as compression ratio.

Where it occurs.

Line "Engine parameters 1" allows you to change parameters common to all engines. The parameters are cylinder volume at bottom dead centre (BDC), pressure at BDC and temperature at BDC. Replot if any of these are changed. Line "Engine parameters 2" allows you to change parameters specific to the selected engine. Replot if any of these are changed.

Special features

The default plots are chosen to constrast different cycle processes. The parameters used do not match the real world well. For example, the Otto cycle uses a compression ratio of \( r_v=4.5 \), more reminiscent of engines in the early 20th century . The compression ratio of a modern automobile makes isochoric cooling process will be difficult to interpret with precision on the pV diagram.

How to draw it

Select an engine and then edit the parameters in the text boxes (identified as "Engine parameters 1" and "Engine parameters 2".) Left click "Replot cycle".

The theory

Exercises

(1) Use radio buttons to select the Ts plot and the Diesel Cycle. Change the compression ratio from 8 to 18 and replot the cycle. Scroll down to review the table of energy flows for each process. (2) Use radio buttons to select the pV plot and the Carnot Cycle. Change the BDC temperature from 500 to 300 K and replot. You will notice a large change in the range of pressure, and that it is difficult to distinguish between individual processes by eye.