Everyone knows that the engines of fighter aircraft are generally equipped with afterburner . During takeoff and emergency situations, the afterburner can be turned on to obtain stronger thrust. From the outside, the aircraft will also eject a long Long flame. So what is the specific principle of the afterburner?
If you want to know the principle of afterburner, you must first understand the principle of jet engine. To put it simply, a jet engine sucks air through the air inlet, and then compresses it by compressor and then enters combustion chamber to mix with fuel. The energy generated can continue to push the turbine to rotate, so that compressor can continue to work. , the gas in the combustion chamber is ejected from the tail nozzle of to form thrust. At this time, because there is still some oxygen in the gas, as long as fuel is injected into the high-temperature gas, the fuel can be burned violently and generate greater thrust. Moreover, when modern military turbofan engines turn on afterburner, the tail nozzle will work together with the afterburner to continuously generate powerful thrust.
The emergence of the afterburner allows fighter jets to obtain very large thrust in a short period of time, which is of great significance in air combat. Let’s take the famous F404 engine in the United States as an example. The F404 engine is a relatively advanced medium-thrust engine in the world, with a small size and high thrust. Under normal circumstances, its maximum thrust is only 48.9 kilonewtons, which is indeed not large, but when the afterburner is turned on, the thrust will suddenly increase to 78.7 kilonewtons, an increase of about 30 kilonewtons, which is nearly three tons of thrust.
So can a fighter jet fly with the afterburner turned on all the time? Of course not, because the oxygen content in the gas passing through the combustion chamber is very low. Although injecting a large amount of fuel at this time will generate thrust, the fuel consumption will also increase rapidly. Generally speaking, aircraft will strictly control the time of the afterburner in order to save fuel during air combat and flight. So passenger aircraft are very concerned about fuel consumption. Are there any models equipped with afterburners?
General passenger aircraft use large bypass ratio turbofan engines, such as Boeing 747. The typical identification feature is that the front end of the engine has a very large diameter fan. However, the disadvantage of the high bypass ratio turbofan engine is that its diameter is too large and the resistance is relatively large, so it is difficult to fly at high speeds. When the United Kingdom and France designed the Concorde, they emphasized continuous flight at high altitudes at a speed of Mach 2, which is equivalent to more than twice that of a Boeing 747 aircraft.
In order to achieve the required performance, Concorde uses a small bypass ratio turbojet engine, whose diameter is significantly smaller than the large channel ratio turbofan engine used by general aircraft. Concorde turns on the afterburner when taking off, and when the aircraft accelerates from Mach 0.95 to Mach 1.7, it also uses the afterburner to increase speed. But when the speed increases to about Mach 2, the aircraft will turn off the afterburner and fly economically. A simple calculation shows that when the Concorde takes off, its four engines consume about two tons of fuel. Two tons of fuel are equivalent to the total internal fuel of the light fighter . In other words, a Concorde fighter jet consumes as much fuel as a light fighter aircraft performs a mission when taking off.
In addition to the Concorde, the Tu-144 supersonic passenger aircraft developed by the Soviet Union also used a similar solution. Four turbojet engines with afterburners were installed under the fuselage. However, the economics of these two types of passenger aircraft are not good enough. Therefore, after the two supersonic passenger aircraft and have withdrawn from the stage of history, will there be any real supersonic civil aviation passenger aircraft?
