For a plane to move through the air, the propulsion system is responsible for generating a specific thrust force. Modern aircrafts use an afterburner to attain this extra energy necessary for its improved efficiency in operating aircrafts. An afterburner, therefore, is able to produce good performance due to the thrust provided which is important for large ranges. Most of the airplanes would require an afterburner to enable them to develop sufficient thrust necessary for taking off and accelerating. Therefore the focus of the discussion will be to analyze the dynamics of the afterburner theory and its operation.
An afterburner or sometimes referred to as a reheat is a component that is mostly found on jet engines such as those used in the military which require moving at the highest speed possible. The main purpose of the afterburner is to provide an increased thrust force that is essential in the provision of supersonic flights, combat situations, and take off. In understanding how the afterburner works, it is crucial to understand what is referred to as the afterburning effect. The effect is achieved via the addition of extra fuel in the turbine through the jet pipe. The afterburner theory and operation is based on the increase of the thrust force that is achieved by the consumption of high fuel.
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According to Sforza (2016), afterburners can operate in such a way that pilots can activate or deactivate them during flight. Maximum power is achieved when the engine is producing maximum thrust wet. Military power is achieved when the engine is in the process of producing a maximum thrust dry. The general principle under which the afterburner works is referred to as the mass flow rate. The resultant thrust force produced is dependent on two important factors. One is the mass of the gas, and secondly is the velocity or speed of the exhaust gas. Therefore, the jet engine will only be in a position to produce an increased thrust under two circumstances, one, when the gas is accelerated at a higher velocity and secondly, exiting a gas with a higher mass from the engine. An afterburner is more effective in a scenario whereby generation of increased power is required for periods that are short. Therefore, its main means of increasing the thrust is by increasing the velocity of the exhaust gas through acceleration. It is, however, crucial to note that the fuel mass added to the gas is not responsible for an increase in the exhaust mass.
The main principle behind the operation of an afterburner is that it adds oxygen directly and instantaneously into the exhaust system and thereafter burn it with the remaining oxygen left in the turbine. The result is the buildup of heat which causes the expansion of the exhaust gases hence increases the jet thrust by more than a half or more. The afterburner possesses a big advantage in that the thrust can be significantly increased without necessarily adding complexity or weight to the engine ( Schobeiri, 2012). An afterburner is regarded as a conglomeration of fuel injectors, an adjustable nozzle, a tube and a flame holder which forms the region where the fuel burns in. An adjustable nozzle is necessary especially for a jet engine so that it can work when both of the afterburners are either on or off. The afterburner is also associated with certain disadvantages that can either reduce its efficiency or increase its management costs. Lee et al. (2015), asserted in generating its power in the form of thrust, the afterburner uses an immense amount of fuel. Therefore, most jets and planes are only reduced to a position where they can use the afterburners sparingly. A good example of the sparing use of the afterburners is when a military jet takes off from the ground or when it is making maneuvers at high speed.
The general design of an afterburner is simple. It also operates with high sensitive tolerances. The first challenge in successful of the afterburners is to maintain a stable flame because ignition must occur within the air that is racing all through. The fuel entering the afterburner do so through small tubes that are arranged in series ranging from 10 or so. The inside of the afterburner is also designed in such a way that the flame flows along a definite axis to prevent any potential contact with the walls. The ignition source and the fuel tubes are placed strategically in front of the jet pipe. The importance of this strategy is that it ensures that the burning exhaust gas flows out of the engine thereby creating a stable zone for the mixture of fuel and air. A stable flow of the gases is essential because it guarantees a quick ignition of the flame and a consistent burning of the gases at a single location. If the burning is not consistent, then the likelihood is that oscillatory movements will be formed that could act to damage the jet pipe or the nozzle.
The afterburner has been used for many years since the periods of the World Wars and has thus assisted in the field of the military. The primary principle of the afterburner is that it provides the jet or aircraft with an extra thrust by increasing combustion through an increased use of fuel. It is advantageous for the pilots who experience an increased efficiency when taking off or maneuvering through sharp bends in the air. The main disadvantage associated with the afterburner is the increased use of fuel hence it can be difficult to sustain. More advances are being made on the afterburners, and the prospect of having better and improved inventions regarding the same remains a reality.
References
Lee, J., Lin, K. C., & Eklund, D. (2015). Challenges in fuel injection for high-speed propulsion systems. AIAA Journal .
Schobeiri, M. T. (2012). Modeling of Recuperators, Combustion Chambers, Afterburners. In Turbomachinery Flow Physics and Dynamic Performance (pp. 367-382). Springer, Berlin, Heidelberg.
Sforza, P. M. (2016). Theory of aerospace propulsion . Butterworth-Heinemann.
