jet engines! how do they work? part 2
Hi there! I´m back for another post. On my last post, I explained how jet engines(gas turbines) worked and where they came from. On this post, I will talk about the future of this technology.
If you read my previous post(which you should have so you can understand this bettter) you will already know that the most prevelant type of gas turbine in aircraft are turbofans, albeit with the exception of helicopters or smaller aircraft which do not require this type of engine. Turbofans are very powerful, relatively efficient and quiet. But, like everything in engineering, things could always be better or more advanced. Turbofans(gas turbines in general) have a problem. Every spinning component in the engine has its optimal RPM(revolutions per minute).
The front fans in turbofan engines cannot spin too fast because, while they might push more air at higher RPMs, when they reach the speed of sound, they will become very loud and produce massive amounts of drag, thus drastically reducing efficiency. Compressors can´t spin too fast either for the same reason, and might even have compressor stalls(when the air stalls in the compressor and the air exits the engine through the intake!). These elements are directly connected to the power turbine, which takes energy from the exhaust gases in order to spin the compressors...etc. There isn´t much you can do to fix this by traditional methods(changing the shape of the blades of the turbine or the compressor, changing the size of each component...etc). Engines need something to change the speed of each element to reach its peak efficiency. There are currently two methods for doing this, albeit one is more ambitious now than the other and will most likely be used in a very long time from now:
1.Transmissions; this method consists of having a gearbox that can reduce the speed of the driveshaft driving each component to its optimal ratio. This will make engines heavier than they are currently(for now), but can make engines more efficient by 15%. This might not seem like much, but it could save airlines millions of dollars a year per plane, thus reducing plane ticket prices, making them even more affordable. It also makes planes up to 60% quieter according to some sources, and it´s a step towards helping the environment. They already exist, and General Electric wants to sell them by the end of the year.
2.Electric engines; this method is one that I´ve fantasized of for a while(btw, I thought I could have made a patent out of it, but the idea was already taken!). It consists of removing most if not all of the power turbines that spin each component. Few would only be kept to make elcetricity for the electric motors to reduce the amount of energy lost in the exhaust. Electric motors would be used to spin each component, and you could potentially connect different components together if an engine fails through a clutch. With these electric engines, you could spin each component to its peak efficiency at different altitudes, reducing noise, the chance of compressor stalls, increasing power output and the spool up time would theoretically be instant. There are...urm... a few "minor" problems with this idea:
1.The electric motors would need to be A LOT lighter than they are now, and would need to be way more powerful too. You could fix this issue with supercooling the engines with liquid helium or nitrogen, but that could make these engines a maintanence nightmare.
2.The batteries that would be installed on board these aircraft would have to be substantially lighter and more energy-dense then they are now. They should also be designed to be safer in-flight, reducing the chance of a fire or worse, an explosion.
The image above shows a drawing I made of what I believe an electrically assisted turbofan would look like
To be honest, there are more problems than I could even count with this idea, but that´s because our material science must catch up to this. It´s more of a chemistry problem(lighter and more conductive materials...etc) than a mechanical engineering endeavor. From this idea you could make engines that are incredibly powerful in such a wide variety of flight regimes that it´s difficult to imagine what this couldn´t be used for! A lot of what I wrote about an electrically assisted jet engine came form me, because, while ideas might already on the internet, not many details are available; and I´m a15 year old pretend engineer, so you have been warned!
That´s it for part two of my series on how jet engines work. I hoped you enjoyed reading this as much as I´ve had writing this. I frecuently have many weird and unconventional solutions to make jet engines more powerful, rocket motors more usable in different regimes...etc. If you would like to read about all those crazy ideas then just tell me, I would be delighted to see what you think of them. If you have any questions about any of my posts, or you would like to correct me, please feel free to tell me.
Thank you for reading, bye!
If you read my previous post(which you should have so you can understand this bettter) you will already know that the most prevelant type of gas turbine in aircraft are turbofans, albeit with the exception of helicopters or smaller aircraft which do not require this type of engine. Turbofans are very powerful, relatively efficient and quiet. But, like everything in engineering, things could always be better or more advanced. Turbofans(gas turbines in general) have a problem. Every spinning component in the engine has its optimal RPM(revolutions per minute).
The front fans in turbofan engines cannot spin too fast because, while they might push more air at higher RPMs, when they reach the speed of sound, they will become very loud and produce massive amounts of drag, thus drastically reducing efficiency. Compressors can´t spin too fast either for the same reason, and might even have compressor stalls(when the air stalls in the compressor and the air exits the engine through the intake!). These elements are directly connected to the power turbine, which takes energy from the exhaust gases in order to spin the compressors...etc. There isn´t much you can do to fix this by traditional methods(changing the shape of the blades of the turbine or the compressor, changing the size of each component...etc). Engines need something to change the speed of each element to reach its peak efficiency. There are currently two methods for doing this, albeit one is more ambitious now than the other and will most likely be used in a very long time from now:
1.Transmissions; this method consists of having a gearbox that can reduce the speed of the driveshaft driving each component to its optimal ratio. This will make engines heavier than they are currently(for now), but can make engines more efficient by 15%. This might not seem like much, but it could save airlines millions of dollars a year per plane, thus reducing plane ticket prices, making them even more affordable. It also makes planes up to 60% quieter according to some sources, and it´s a step towards helping the environment. They already exist, and General Electric wants to sell them by the end of the year.
2.Electric engines; this method is one that I´ve fantasized of for a while(btw, I thought I could have made a patent out of it, but the idea was already taken!). It consists of removing most if not all of the power turbines that spin each component. Few would only be kept to make elcetricity for the electric motors to reduce the amount of energy lost in the exhaust. Electric motors would be used to spin each component, and you could potentially connect different components together if an engine fails through a clutch. With these electric engines, you could spin each component to its peak efficiency at different altitudes, reducing noise, the chance of compressor stalls, increasing power output and the spool up time would theoretically be instant. There are...urm... a few "minor" problems with this idea:
1.The electric motors would need to be A LOT lighter than they are now, and would need to be way more powerful too. You could fix this issue with supercooling the engines with liquid helium or nitrogen, but that could make these engines a maintanence nightmare.
2.The batteries that would be installed on board these aircraft would have to be substantially lighter and more energy-dense then they are now. They should also be designed to be safer in-flight, reducing the chance of a fire or worse, an explosion.
The image above shows a drawing I made of what I believe an electrically assisted turbofan would look like
To be honest, there are more problems than I could even count with this idea, but that´s because our material science must catch up to this. It´s more of a chemistry problem(lighter and more conductive materials...etc) than a mechanical engineering endeavor. From this idea you could make engines that are incredibly powerful in such a wide variety of flight regimes that it´s difficult to imagine what this couldn´t be used for! A lot of what I wrote about an electrically assisted jet engine came form me, because, while ideas might already on the internet, not many details are available; and I´m a15 year old pretend engineer, so you have been warned!
That´s it for part two of my series on how jet engines work. I hoped you enjoyed reading this as much as I´ve had writing this. I frecuently have many weird and unconventional solutions to make jet engines more powerful, rocket motors more usable in different regimes...etc. If you would like to read about all those crazy ideas then just tell me, I would be delighted to see what you think of them. If you have any questions about any of my posts, or you would like to correct me, please feel free to tell me.
Thank you for reading, bye!
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