4. Advanced combinations

The operating principle of combustion engines and chambers is based on the confinement of a reactive mixture in an enclosure where the heat released can be recovered. This means maintaining the combustion reaction for as long as necessary, and wherever the mixture has been distributed to consume the fuel efficiently. This stabilization or control of flame or combustion involves the initial stage of ignition, followed by flame development and extinction.

Ignition may be achieved spontaneously by self-ignition under high temperature or pressure conditions, or it may require additional energy. When an energy input is required, the most widespread method is to ignite the mixture with an electric spark (spark plug). But there are many other ways of providing a local or global surplus of energy to activate combustion.

Flame development has traditionally...