OTTO CYCLE

OTTO CYCLE

The Otto cycle is a set of processes used by spark ignition internal combustion engines (2-stroke or 4-stroke cycles). These engines a) ingest a mixture of fuel and air, b) compress it, c) cause it to react, thus effectively adding heat through converting chemical energy into thermal energy, d) expand the combustion products, and then e) eject the combustion products and replace them with a new charge of fuel and air. The different processes are shown in Figure

1. Intake stroke, gasoline vapor and air drawn into engine (5à1).

2. Compression stroke, p, T increase (1à2).

3. Combustion (spark), short time, essentially constant volume (2à3). Model: heat absorbed from a series of reservoirs at temperatures T2 to T3.

4. Power stroke: valve opens, gas escapes.

5. Valve exhaust: valve opens, gas escapes.

6. (4à1) model: rejection of heat to reservoirs at temperatures T4 and T1.

7. Exhaust stroke, piston pushes remaining products out of chamber (1à5).