HD Animation: Thermodynamic processes in a four-stroke petrol engine

The animation shows the thermodynamic processes taking place inside a four-stroke Otto engine.

The four-stroke Otto engine accompanies us every day, often without us noticing: In cars, it drives pistons through exactly four steps – intake, compression, power, exhaust. Lawn mowers, motorcycles, and emergency generators also use this principle. Although modern vehicles are becoming increasingly electrified, the Otto engine remains one of the most widely used machines in the world thanks to its simple design and high power density.

Instructions for Use

The windows can be enlarged or reduced with a click, as with all animations.

You can also enlarge or reduce the contents of a window yourself. To do this, click one of the selection buttons under the heading “Views”:

After starting the application, you can watch the animation in full-screen mode. To do this, click “View” and then “Full Screen”:

To exit full-screen mode, press the Esc key.

Explanations

The current state is marked in a PV diagram. A PV diagram (pressure-volume diagram) is used to visualize the state of a gas, in this case the air-fuel mixture inside the cylinder of an internal combustion engine. The four strokes are color-coded in the PV diagram.

The ignition timing is also shown. The ignition timing is the moment when the air-fuel mixture in the cylinder is ignited.

If the engine speed is changed (by accelerating), the ignition occurs earlier. This is because the speed of combustion is always constant. By shifting the ignition timing, it is ensured that the flame front hits the piston at exactly the right moment.

This relationship between engine speed, ignition timing, and flame front position ensures optimal engine performance.

The flame front spreads in the cylinder at an almost constant speed. To ensure that the maximum pressure acts on the piston at the optimal moment, the ignition timing must be adjusted depending on engine speed. At low speeds the ignition occurs later, at high speeds earlier. Even a few degrees of deviation can cause the engine to produce less power or burn inefficiently. Modern engine control units correct the ignition timing up to hundreds of times per second.

Overview and Download

Title	Thermodynamic Processes in a Four-Stroke Otto Engine
Target Group	Teachers and Presenters
Platforms	Microsoft® Windows® Apple® Macintosh® (version-dependent)
Features	Full-screen mode lossless scaling supports large displays and projection screens
License	Freeware
Download	Contact

Contributors

C. Hein, S. Rikowski

Sources

• Idea and initial concept: Tamara Riehle
• Technical drawing of the engine: based on Ulrich Rapp (http://www.ulrich-rapp.de/stoff/fahrzeug/motor/index.htm)
• Authoring tool (control elements included): Adobe Animate

Share

Share the animation with your colleagues.