Regan Brown
Afterburners are used to increase thrust in jet engines, mostly in military supersonic aircraft. They are used for short periods of time to improve aircraft take-off, climb, or combat performance. Due to their high fuel consumption, afterburners are only used when necessary, as they significantly increase fuel consumption and decrease fuel efficiency. This text will explore the impact of afterburners on fuel consumption and the trade-offs involved in their usage.
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What You'll Learn
- Afterburner fuel consumption varies depending on the aircraft, engine, fuel capacity, and altitude
- Afterburners use roughly 2lb of fuel per lbf of thrust per hour
- Afterburners are used sparingly in modern jets due to longer-range missions
- Afterburner exit volume flow must be accommodated to prevent compressor stall
- Afterburners are generally used only in military aircraft
Afterburner fuel consumption varies depending on the aircraft, engine, fuel capacity, and altitude
Afterburners are used to increase thrust, usually for supersonic flight, takeoff, and combat. They are mostly used on military supersonic aircraft and are considered standard equipment on fighter aircraft. The use of afterburners, however, is limited to short periods due to their high fuel consumption, which also makes sustained high speeds impossible.
The fuel consumption of afterburners varies depending on several factors, including the aircraft, engine, fuel capacity, and altitude. Different aircraft have different internal fuel capacities, which directly impacts the duration of afterburner usage. For example, the Tomcat has more than double the internal fuel capacity of the MiG. The type of engine also plays a role, with turbojet engines exhibiting a gain of up to 50% in efficiency when afterburning, while turbofan engines can achieve gains of up to 70% depending on the bypass ratio.
Altitude is another factor influencing afterburner fuel consumption. At higher altitudes, the efficiency of afterburners can be affected by factors such as speed and pressure. For instance, the SR-71 aircraft demonstrated reasonable efficiency at high altitudes due to its high speed (Mach 3.2) and high pressure resulting from ram intake. Additionally, the throttle setting and temperature can also impact fuel consumption.
The specific fuel consumption of afterburners is typically measured in pounds of fuel used per pound of thrust. On average, afterburners use around 2 pounds of fuel per pound of thrust per hour, with values ranging from 1.5 to nearly 3 pounds per pound of thrust per hour. Modern fighter jets typically operate at around 2 pounds per pound of thrust per hour. In comparison, when jets are not using afterburners, their fuel consumption is significantly lower, ranging from 0.7 to 0.9 pounds per pound of thrust per hour.
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Afterburners use roughly 2lb of fuel per lbf of thrust per hour
Afterburners are used to increase thrust, usually for supersonic flight, takeoff, and combat. They are mostly used on military supersonic aircraft and are considered standard equipment on fighter jets. The afterburning process involves injecting additional fuel into a combustor or "burner" in the jet pipe behind the turbine, reheating the exhaust gas. This process significantly increases thrust without the need for a bigger engine, which would add weight.
Due to their high fuel consumption, afterburners are typically used sparingly and only for short periods. The specific fuel consumption of an afterburner, or the amount of fuel used per unit of thrust, is much higher than that of the core engine. Afterburners use approximately 2lb of fuel per lbf of thrust per hour, with values ranging from 1.5 to nearly 3lb/lbf/hr. Most modern fighter jets operate at around 2lb/lbf/hr.
To illustrate the fuel consumption of afterburners, consider a jet with 15,000lb of usable fuel that produces 35,000lbf of thrust in afterburner mode. This jet will consume 70,000lb of fuel per hour, or 1,167lb of fuel per minute. With its 15,000lb fuel load, the jet would have just under 13 minutes of afterburner time. In practice, pilots would rarely use the afterburner for an extended period, except in specific scenarios such as an alert launch intercept.
The high fuel consumption of afterburners limits their use to short-duration, high-thrust requirements. These include heavyweight or short-runway takeoffs, assisting catapult launches from aircraft carriers, and air combat. While afterburners provide a significant increase in thrust, they do so at the cost of decreased fuel efficiency.
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Afterburners are used sparingly in modern jets due to longer-range missions
Afterburners are an additional combustion component used on some jet engines, mostly those on military supersonic aircraft. They increase thrust by injecting additional fuel into a combustor in the jet pipe behind the turbine, “reheating” the exhaust gas. This process significantly increases thrust without adding much weight or complexity to the engine.
However, afterburners also significantly increase fuel consumption, resulting in decreased fuel efficiency. Due to this, their use is limited to short periods and specific scenarios, such as heavyweight or short-runway take-offs, assisting catapult launches from aircraft carriers, and during air combat.
In modern times, the use of afterburners has become even more sparing as jets are increasingly performing longer-range missions. While supercruise can help improve fuel efficiency, it still burns 2-4 times more fuel than subsonic cruise, making supersonic speeds incompatible with long-range or long-duration missions.
The high fuel consumption of afterburners limits their practicality, especially for modern jets with longer-range capabilities. As such, afterburners are used sparingly, only in specific situations where the benefits of increased thrust outweigh the significant fuel costs.
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Afterburner exit volume flow must be accommodated to prevent compressor stall
Afterburners are used to increase the thrust of jet engines, usually for supersonic flight, take-off, and combat. They are mostly used on military aircraft, but some civilian planes, such as Concorde, have also used them. The afterburning process involves injecting additional fuel into a combustor in the jet pipe behind the turbine, which reheats the exhaust gas and significantly increases thrust.
Due to their high fuel consumption, afterburners are only used for short periods and specific purposes, such as heavyweight or short-runway take-offs, catapult launches from aircraft carriers, and air combat. The increased fuel flow in the afterburner leads to a higher specific fuel consumption (SFC).
The use of an afterburner results in an increased volume flow at the exit, which must be accommodated to prevent a compressor stall. Compressor stalls occur in gas turbine engines when the smooth airflow over the compressor blades is disrupted, leading to a momentary power drop and, in some cases, a loud bang. This disruption in airflow can cause unstable airflow patterns and, if not managed properly, can lead to a more severe issue called a compressor surge, where the airflow comes to a complete halt, potentially damaging engine components.
To prevent compressor stalls, the exit nozzle of the afterburner is designed with a larger throat area to accommodate the increased volume flow. This prevents any pressure increase in the jet pipe, which could cause the gas to flow upstream and re-ignite, leading to a compressor stall. Modern afterburner designs incorporate variable-geometry (VG) nozzles to handle the increased volume flow and multiple stages of augmentation through separate spray bars. Additionally, anti-stall systems are in place, which automatically dump away unwanted air to prevent compressor stalling.
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![Afterburner [Explicit]](https://m.media-amazon.com/images/I/814n6aOJk-L._AC_UY218_.jpg)
Afterburners are generally used only in military aircraft
Afterburners are mostly used in military aircraft, and they are considered standard equipment on fighter jets. They are used in some civilian aircraft, such as NASA research aircraft, the Tupolev Tu-144, Concorde, and the White Knight of Scaled Composites. However, their use is limited due to their high fuel consumption.
Afterburners are an additional combustion component added to jet engines. They increase thrust by injecting extra fuel into a combustor (or "burner") in the jet pipe behind the turbine, reheating the exhaust gas. This process significantly increases thrust without needing a bigger engine, but it also increases fuel consumption, limiting its use to short periods.
The high fuel consumption of afterburners makes them impractical for long-duration use. They are typically used for short-duration, high-thrust requirements, such as heavyweight or short-runway take-offs, assisting catapult launches from aircraft carriers, and during air combat. The extra speed provided by afterburners can be advantageous in combat situations.
The extent of the increase in thrust from an afterburner can vary. For example, the afterburners on the Olympus engines of the Concorde supersonic jet only increased thrust by 17%, while the thrust increase in modern military aircraft can range from approximately 40% to 70%. The use of afterburners can also cause the engine to stall if the airflow reverses direction, requiring the expansion of the exhaust nozzle section to prevent this.
In modern times, the use of afterburners has become more sparing due to the longer-range missions of aircraft. However, they remain a popular choice for aircraft designers due to the extra speed and power they provide, especially in military applications.
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Frequently asked questions
Afterburners use approximately 2lb of fuel per lbf of thrust per hour. This can vary from 1.5 to nearly 3lb/lbf/hr, but most modern fighters operate at around 2.
Afterburners have a higher specific fuel consumption (SFC) than jet engines. When jets aren't using afterburners, they typically burn around 0.7 to 0.9lb/lbf/hr.
This depends on many factors, including the aircraft, engine, fuel capacity, altitude, throttle setting, and temperature. Smaller fourth-generation fighters can sit at 25,000 ft for around 5 minutes using afterburners before running out of fuel.
