After building a couple non-selfsus jet turbines, i now whant to try building a selfsus one. I saw a lot of simple designs using superchargers, but there is one personal problem for me: i absolutely hate radial compressor engines. Thats why i wanted to make one with a axial compressor. My designgoals are relatively simple: it just needs to selfsustain. I thought about using steel for the casing and for all of the sensitive things behind the combustionchamber. For the compressor infront i would use a cheaper material. Can anyone help me with the math and maybe give me tips for the material choices? Its my first real jet engine project which is not just a EDF with an afterburner strapped on.
Unless you're an extremely skilled metal working modeler , forget trying to make an axial compressor stage, there have been a few made ,but the performance won't be any better than a radial engine .
If you want a simple self sustaining engine then use an EDF fan , its efficiency should be high enough to get the engine working as the turbine stage can be a little cruder but still work well enough to power it .
Most axial comp stages produce little static pressure rise but mainly dynamic velocity , this velocity needs to be reduced in an efficient diffuser downstream of the EDF fan to convert into static pressure before it enters the flametube and onwards to the axial turbine stage .
LOL, you may "hate" radial comp wheels/engines , but they are the best choice at our mass flow levels.
And what about a multy stage one? Seems oretty simple to me. I could use two turbocharger, one larger and one smaller and just skip the generator of the first one and just hook it up to the generator of the second one. Then just route the high pressure air from the first one in the second one, and pressurise it even more. Then its the same as with every other. Although iam not shre if that would be overkill and would hit the structural and temperatural limits of the parts. The first one would need to spin slower than the second one i think. I also think that it would be a major advantage because the amaller one doesnt create that much centrifugal force so the turbine could theoreticaly create more thrust.
Hi racket, then i dont completely understand how radialcompressors work. My thoughtprocess here was really simple: Big radialcompressor = A lot of air intake, but cant spin that high so cant compress that high. Small radialcompressor = Not a lot of air intake, can spin high so can compress air high. Big + Small = A lot of intake + good compression. I thought good compression would be better than just a lot of air without compression because good compression means more air molekules on a tinyer space which helps burning the fuel more efficiently and therefore would save fuel and create more thrust. I thought with the expansion of the compressed gas you would get >30% of the energy that you put in to compress back and that the burned fuel would make up that deficid and would make the turbine more efficient. Maybe i just dont understand how turbines work.
The pressure that is developed depends on the exducer tip speed of the compressor , a big compressor needs less RPM to achieve the same tip speed as a small comp wheel , for the same exducer tip speed you'll have the same pressure ...............simple :-)
My comp wheel is 175mm diameter and only needs 60,000 rpm to achieve a high pressure , an 87.5 mm comp wheel would need 120,000 rpm to produce the same pressure .
Hi, I now read through the book and understood the basics. The only problem for me is that the book says you need a lot of equipment which is expensive. Iam unfortuanetly very limited with my budget so i whanted to ask you which equipment i really need to even consider building. And i whanted to ask you a bit about the parts. Same thing as bevor, iam limited with my budget so i whanted to ask what i can do to keep the overall cost low. I know that that is not that ideal for trying to build a jet turbine but i wanna atleast try.
Last Edit: Sept 23, 2023 12:55:40 GMT -5 by nima0908
Turbine engines need precision of components , so theres really no way around the need for things like a lathe, mill and welders , thats why guys use turbochargers as the basis for their engines , the combustor can be rather crudely made without the need for precision .
Hi, so i can cut costs by using a turbocharger? Does that mean using the whole charger or just the compressorwheel? From that what i understood from the book, the compressor is the thing where you need a lot of precission and that you can just use a 65mm turbocharger comp wheel because the big companies building them optimised them. The other thing where you need precission is the Guide vane carrier, but in the book, it looked doable with your hand and it looked like you could get relatively good precision even with your hand. Same with the turbine wheel. In the book, he just used a metal ring and carefully cut stripes into it, put metal plates in it and weldet it. Doesnt seem impossible to me to do it by hand.
Last Edit: Sept 24, 2023 5:02:21 GMT -5 by nima0908
Hello, in the last few month, i couldnt really continue this project because of health issues. Yesterday i read an article about rde`s (rotating detonation engines) and got very intrested. One thing in particular caught my eye. I sadly didnt fully understood what it sayd, so i whanted to ask if any one of you could maybe explain it to me. It soundet like a really fun project (although its not doable for me because it is probaply too difficult) because it could replace the combustion chamber and generate more thrust.
Last Edit: Jan 6, 2024 16:51:30 GMT -5 by nima0908