Indicator Diagram

A plot of pressure vs. volume. This is a graphical representation of the changing relationship between pressure and volume in the cylinder during engine cycles.

Also, known as a PV diagram.

Lines or curves on the indicator diagram represent processes. The areas under curves on the indicator diagram are equal to the work released by the process.

A PV curve or diagram shows the impact of early or late ignition timing on peak cylinder pressure.

Carnot Cycle

An idealized reversible thermodynamic cycle. In 1824 Carnot showed that the amount of heat which could be converted into mechanical work by an ideal perfect heat engine using a perfect gas as the working fluid, depended solely upon the working range of temperature.

Steam Engine Indicator Diagram

The pressure in the cylinder is plotted versus the cylinder volume. This was developed by James Watt and John Southern to improve the efficiency of the steam engine. The work done is the area within the red curve.

See also: Pressure, Steam Engine Indicator Diagram, Volume, Work.

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Subjects: Chemistry Mechanical Engineering Physics