Jet engines! how do they work? part 1
Hi there! I´m back for another post. Today we are talking about jet engines. On this post we will talk about how this technology was conceived,then about how it changed and evolved to the present and what this is used for. In another post, I will talk about the future of this technology.
In order for me to explain how a jet engine works, I must define what it is because there are many misconceptions about this. A jet engine is a reaction engine discharging a fast moving jet of some type of fluid(or anything really) that generates thrust by jet propulsion. This includes gas turbines that you can find on airliners and fighters, rocket motors, pulse jets, ramjets and scramjets. I will talk more about these seperately in the future, but for today I will only explain gas turbines, for a very good reason. In common parlance, the term "jet engine" usually refers to gas turbines. These use the same properties as the other examples of jet engines, but have their own special characteristics.
THE HISTORY
Gas turbines have been around for longer than most people think. In 1629, the first gas turbine device came into use when the Italian engineer Giovanni Branca, produced a steam-driven impulse turbine.
Branca´s design was a closed, water-filled vessel with one exhaust nozzle aimed at a turbine or impulse wheel. Solid fuel heated the vessel, and the system directed the resulting steam on to the impulse wheel. The rotating wheel then drove a crude cogwheel reduction gear system. This mechanism, now on display in the British Museum, is said to be the forefounder of the modern turbosupercharger used on reciprocating engines. Since then, gas turbines have changed a lot.
In the early 20th century, the countries that were designing gas turbines at the bleeding edge of their time(Germany, Italy, the UK...etc) all eventually arrived to a similar design. It is called the turbojet engine. It has 2 main variants:
Centrifugal flow turbojets were the first turbojets to be developed. They are very simple(relatively speaking). It consists of an air intake, followed by a centrifugal impeller/compressor, which sends air in a centrifugal fashion to the combustion chamber. Here, the fuel is burnt with the air supplied by the impeller, which creates a gas expansion due to the rise in temperature. The combustion chamber is shaped in a certain way so that it uses this gas expansion to its advantage, accelerating the air a lot. This fast moving air is whats known as the "jet" in jet engines. This fast moving air moves a turbine, which spins the impeller via a driveshaft. The exhaust gases lose energy doing this, but is essential for the engine to work.
Axial flow turbojets are the most advanced type of turbojet. It was designed in parallel with the centrifugal flow trubojet, but due to the high developement costs, the need for rare materials in its design, and the Second World War made it near impossible to develop in the 1940s. This didn´t stop Nazi Germany, who were the first to make the worlds first operational jet fighter, the Messerschmit Me 262. It featured two axial flow turbojet engines. Due to the high complexity of the engines, it´s unreliability, and the need for rare metals, meant it had a high down-time between missions. These turbojets operate like this:
It has an air intake, which is followed by an axial compressor, which differs from a centrifugal compressor in the way it moves air. An axial compressor moves air in an axial fashion, rather than in a centrifugal one. This compresses the air more, while allowing its speed to be decreased less(depending on the airspeed of the aircraft). This can help the engine make more power. There can be various types of compressors, but I will explain them in the future. After moving through the compressors, the compressed air goes into the combustion chamber, whre it is mixed with fuel and burnt. The rest of the engine works just like in the one I described earlier. The fast moving exhaust gases spin the turbine/s and is expelled out through an exhaust, producing power. The turbines in these engines can be used to spin a large variaty of compressors with different sizes and applications.
FROM WW2 TO TODAY
After WW2, there was a dramatic change in every thing from power generation through nuclear reactors and, in the case of many vehicles, the jet engine was becoming a reality. After WW2, engineers where designing new and more advanced types of gas turbines, not just for planes, but also for warships, and even some tanks! Engineers exploited the turbojet design to its limits, and since the technology could be sold to the civilian market for airliners...etc, new designs for new applications needed to be made. In the 1960s, a new type of gas turbine was introduced to both the military and the civilian market, and its called the turbofan.
Turbofans are very similar to turbojets, but are intended for different applications. Here´s how it works:
It´s exactly the same as a turbojet, except that infront of the compressors is a fan driven by a turbine located at the back of the engine. This fan creates thrust by moving varying amounts of air(depending on application) at varying amounts of velocity(again depending on application) around the core of the engine(where the combustion chamber and compressors...etc are located). These engines are also known as"bypass"turbofan engines. There are different bypass ratios depending on the desired application, but what is really important to know is that these engines are more eficient, powerful, and quieter than their older counterparts. The reason for these benefits will be explained in the future.
Some tanks and warships use gas turbines, but they don´t use turbofans, they use gas turbines that are nearly identical to turbojets. In a lot of cases, ships, power stations...etc use turbojets that have been modified to burn natural gas instead of kerosene. These modified engines spin a transmission in some tanks, spin alternators to make electricity...etc. Basically, if you need lots of power to do something, but it also needs to be reliable, just use a jet engine! Turbofans are used on all new fighters, most new types of airliners, and the technology is used on other engines that are very similar, like the turboprop engines.
That´s it for part1! I will soon upload the second part,where I will talk about the future of this technology. I hope you enjoyed reading this. Jet engines are very complicated, so if you have any questions, feel free to ask them, and If you found a mistake in my explanation, please feel free to correct me! Bye!
In order for me to explain how a jet engine works, I must define what it is because there are many misconceptions about this. A jet engine is a reaction engine discharging a fast moving jet of some type of fluid(or anything really) that generates thrust by jet propulsion. This includes gas turbines that you can find on airliners and fighters, rocket motors, pulse jets, ramjets and scramjets. I will talk more about these seperately in the future, but for today I will only explain gas turbines, for a very good reason. In common parlance, the term "jet engine" usually refers to gas turbines. These use the same properties as the other examples of jet engines, but have their own special characteristics.
THE HISTORY
Gas turbines have been around for longer than most people think. In 1629, the first gas turbine device came into use when the Italian engineer Giovanni Branca, produced a steam-driven impulse turbine.
Branca´s design was a closed, water-filled vessel with one exhaust nozzle aimed at a turbine or impulse wheel. Solid fuel heated the vessel, and the system directed the resulting steam on to the impulse wheel. The rotating wheel then drove a crude cogwheel reduction gear system. This mechanism, now on display in the British Museum, is said to be the forefounder of the modern turbosupercharger used on reciprocating engines. Since then, gas turbines have changed a lot.
In the early 20th century, the countries that were designing gas turbines at the bleeding edge of their time(Germany, Italy, the UK...etc) all eventually arrived to a similar design. It is called the turbojet engine. It has 2 main variants:
Centrifugal flow turbojets were the first turbojets to be developed. They are very simple(relatively speaking). It consists of an air intake, followed by a centrifugal impeller/compressor, which sends air in a centrifugal fashion to the combustion chamber. Here, the fuel is burnt with the air supplied by the impeller, which creates a gas expansion due to the rise in temperature. The combustion chamber is shaped in a certain way so that it uses this gas expansion to its advantage, accelerating the air a lot. This fast moving air is whats known as the "jet" in jet engines. This fast moving air moves a turbine, which spins the impeller via a driveshaft. The exhaust gases lose energy doing this, but is essential for the engine to work.
It has an air intake, which is followed by an axial compressor, which differs from a centrifugal compressor in the way it moves air. An axial compressor moves air in an axial fashion, rather than in a centrifugal one. This compresses the air more, while allowing its speed to be decreased less(depending on the airspeed of the aircraft). This can help the engine make more power. There can be various types of compressors, but I will explain them in the future. After moving through the compressors, the compressed air goes into the combustion chamber, whre it is mixed with fuel and burnt. The rest of the engine works just like in the one I described earlier. The fast moving exhaust gases spin the turbine/s and is expelled out through an exhaust, producing power. The turbines in these engines can be used to spin a large variaty of compressors with different sizes and applications.
FROM WW2 TO TODAY
After WW2, there was a dramatic change in every thing from power generation through nuclear reactors and, in the case of many vehicles, the jet engine was becoming a reality. After WW2, engineers where designing new and more advanced types of gas turbines, not just for planes, but also for warships, and even some tanks! Engineers exploited the turbojet design to its limits, and since the technology could be sold to the civilian market for airliners...etc, new designs for new applications needed to be made. In the 1960s, a new type of gas turbine was introduced to both the military and the civilian market, and its called the turbofan.
Turbofans are very similar to turbojets, but are intended for different applications. Here´s how it works:
It´s exactly the same as a turbojet, except that infront of the compressors is a fan driven by a turbine located at the back of the engine. This fan creates thrust by moving varying amounts of air(depending on application) at varying amounts of velocity(again depending on application) around the core of the engine(where the combustion chamber and compressors...etc are located). These engines are also known as"bypass"turbofan engines. There are different bypass ratios depending on the desired application, but what is really important to know is that these engines are more eficient, powerful, and quieter than their older counterparts. The reason for these benefits will be explained in the future.
Some tanks and warships use gas turbines, but they don´t use turbofans, they use gas turbines that are nearly identical to turbojets. In a lot of cases, ships, power stations...etc use turbojets that have been modified to burn natural gas instead of kerosene. These modified engines spin a transmission in some tanks, spin alternators to make electricity...etc. Basically, if you need lots of power to do something, but it also needs to be reliable, just use a jet engine! Turbofans are used on all new fighters, most new types of airliners, and the technology is used on other engines that are very similar, like the turboprop engines.
That´s it for part1! I will soon upload the second part,where I will talk about the future of this technology. I hope you enjoyed reading this. Jet engines are very complicated, so if you have any questions, feel free to ask them, and If you found a mistake in my explanation, please feel free to correct me! Bye!
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