ระบบเพิ่มแรงขับ (Afterburner) (AB: Afterburner)

What Is an Afterburner?

An afterburner (AB) — also called a reheat system in British terminology — is a secondary combustion chamber installed in the exhaust duct of a military turbofan or turbojet engine, between the turbine exit and the variable exhaust nozzle. By injecting additional fuel into the oxygen-rich exhaust stream and reigniting it, the afterburner produces a dramatic, rapid thrust increase at the cost of extremely high fuel consumption. It enables supersonic flight, rapid acceleration, and high-performance manoeuvring that would be impossible with the core engine alone.

How It Works

Gas turbine combustion uses only a fraction of the available oxygen in intake air — combustor equivalence ratios are deliberately kept below 0.4 to limit turbine inlet temperatures to survivable levels. The turbine exhaust therefore still contains substantial unburned oxygen (approximately 15–17% O2 vs. atmospheric 21%).

The afterburner exploits this residual oxygen. Fuel is injected through spray bars spanning the exhaust duct and ignited by a continuous pilot flame or hot-streak igniter. Without turbine blades to protect, combustion temperatures in the afterburner can reach 1,700–2,200°C (3,090–3,990°F). A variable convergent-divergent (con-di) nozzle expands to accommodate the dramatically increased exhaust volume and optimize the exit pressure ratio for maximum thrust.

Performance Specifications

• Thrust increase: 50–70% above dry (non-afterburning) thrust
• Fuel consumption increase: 200–300% — thrust specific fuel consumption (TSFC) roughly doubles to triples
• Exhaust gas temperature: 1,700–2,200°C (3,090–3,990°F)
• Typical engagement duration: seconds to a few minutes (fuel exhaustion, heat limits)
• Example: F119-PW-100 in F-22 Raptor — 156 kN (35,000 lbf) dry, 222 kN (49,900 lbf) with afterburner

Aircraft Examples

• F119-PW-100 on the Lockheed Martin F-22 Raptor — enables Mach 2.25+ and supersonic cruise (supercruise) without afterburner
• F100-PW-229 on the F-16 Fighting Falcon — 80 kN (17,800 lbf) dry, 130 kN (29,100 lbf) with AB
• EJ200 on the Eurofighter Typhoon — 60 kN (13,500 lbf) dry, 90 kN (20,230 lbf) with AB
• Snecma M88-2 on the Dassault Rafale — 50 kN (11,250 lbf) dry, 75 kN (16,900 lbf) with AB
• Olympus 593 on Concorde — all four engines used full afterburner for takeoff and transonic acceleration to Mach 2.0 cruise

Afterburners are almost exclusively a military technology due to their extreme fuel consumption. The Concorde remains the only commercial aircraft to use afterburning engines in service. Modern military designs focus on maximizing dry thrust to reduce afterburner reliance — the F-22's supercruise capability at Mach 1.8 without afterburner is a notable milestone in this direction.