afterburners

An afterburner, officially called a reheat in British terminology, is an auxiliary combustion component used on some jet engines to increase thrust. It injects additional fuel into the hot exhaust stream and ignites it, producing a second, high-temperature flame that accelerates exhaust gases and thus increases propulsion. Afterburners are common on military supersonic fighter and bomber aircraft and on some civilian supersonic transports.

Function and design: After the turbine, within the exhaust or jet pipe, an afterburner assembly houses fuel injectors, igniters, and flameholders. Fuel is metered into the annular space and combusted in the presence of the hot exhaust gases. The flameholder stabilizes the flame; a variable-area or fixed nozzle controls expansion to optimize thrust at a given speed and altitude. The result is a large but temporary thrust increase at the cost of substantially higher fuel consumption.

Performance and use: Thrust can increase by about 30–150 percent depending on engine and conditions, but typical military usage aims for tens of seconds to a few minutes, such as for takeoff, combat thrust, or rapid climb. The afterburner increases the exhaust gas temperature and velocity and raises the aircraft's infrared signature and fuel burn. Notable examples include many Cold War and modern fighters; civilian applications have been rare, with the Concorde using afterburners for takeoff and acceleration to supersonic speed.

Limitations and safety: Afterburners are highly fuel-inefficient and generate extreme heat, demanding robust materials, cooling, and maintenance. They are generally unsuitable for sustained operation except where high thrust is needed briefly. They also produce a noticeable infrared plume and can impact engine stability if not controlled properly.