Otto Cycle

PV diagram

TS diagram

thermal efficiency

engine diagram

compression ratio r

8

temperature of the heat sink

T

H

293

temperature of the heat source

T

C

1500

Area

::shdw

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The Otto cycle is an idealized thermodynamic cycle proposed by Nikolaus August Otto in 1876. This cycle describes the functioning of a typical reciprocating piston engine (see snapshot 4 or the "engine diagram" button). This thermodynamic cycle is used in automobile engines. This cycle consists of two adiabatic and two isochoric transformations. The thermal efficiency of this cycle is given by:

η=1-

1-γ

r

, where

r

is the compression ratio and

γ

is the specific heat ratio, taken to be 1.4 for air in the present Demonstration.

This Demonstration plots the four transformations in the PV (i.e. pressure vs. volume) and TS (i.e. temperature vs. entropy) diagrams. The adiabatic and isochoric transformations are shown in blue and red, respectively. The areas shown in the PV and TS diagrams are equal to the net work and to the net heat transfer, respectively. These two quantities are equal. You can set the values of the heat source temperature, the heat sink temperature, and the compression ratio.