Turbojet Engine (how NOT to)

This is not finnished because it won't work. You could make it work though according to rajat1sharma by making a bigger multistage compressor, or mabey with a big centrifugal compressor. Sorry to anyone who started building this, you will have to do your own problem solving if you want it to run.

The concept of a jet engine is basically a rocket that uses air as the oxidizer instead of something that's already stored on board. There are many types of jet engines, but I will focus on turbojets. The purpose of a turbojet is to push a lot of air out the back of itself at high speed to provide forward thrust. It does this by combining the air with a fuel like propane or kerosene in a combustion chamber and igniting it to cause it to expand and rush out the rear of the engine. The heated, high pressure gasses flowing out spin a turbine at the back of the engine which provides the power for the compressor. The compressor is a fan at the front of the engine that forces air into the combustion chamber to be mixed with fuel.

This instructable will show you how to build a small turbojet from scratch. This design could be scaled up to be used on anything once you have practiced with a small one.
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ron3421 year ago
Not yet for pics, I'm still putting the materials together and drawing it out - its to be used at the end of a long string of piped water to power a drill to put down a geothermal well - think a 100' of 1 1/4" polyprop pipe ending in maybe a 2' piece of 3" pvc pipe with a row of axial blades turning on a shaft inside with water pumped in at maybe 50 psi/ 50 gpm at one end with the blades driving a 4" dia earth bit at the outlet of the 3" pipe - this is all a maybe! but hell I now have an easy way to make a bunch of blades. Jets have static blades that deflect the flow back to a better angle for each seceding row of rotary blades but I'm hoping I don't have to do that. I'll send a pic when I get there
Jaycub (author)  ron3421 year ago
A geothermal well, what is that exactly? One that is deep enough to never freeze or something? I am just hoping you are not actually trying to put a geothermal power plant in your yard! But if you do then that is very ambitious of you.

You will need to have some stator blades to hold the axel, so why not put them between each turbine blade?
ron3421 year ago
Hello Jaycub and congratulations on a great attempt at an axial flow jet. One of the comments added that its really difficult to come up with a working axial compressor.
I think you did well with the tools you had - learning to tig weld would be a great help to you.
I had been looking for a week for a simple way to build an axial water turbine short of CNC machining - the blades had me stumped til I came across your instructible - it gave me your idea on how to make the blades simply - so thanks!!
Jaycub (author)  ron3421 year ago
Cool, I'm glad there was some benefit to this other than just what I learned. Do you have pictures of your water turbine?

I can tig weld but it has been a couple years now since I've done it. But since this instructable I purchased a cheap flux wire welder, and I have an oxyhydrogen torch partway made.
brendonl2 years ago
You have done an excellent job, it looks like you you put a quite decent amount of work into this bit of engineering. You have got some inventors potential :)
marksteamnz3 years ago
. Your design unfortunately has zero chance of working. Even if the compressor stage was perfectly designed and the combustor correctly dimensioned you can not get enough pressure rise in the compressor to over come the drag of the bearings etc. Axial Gas turbines need multiple compressor blades stacked with stators and the blades need to be aerodynamically perfect and unfortunately this gets worse the smaller the turbine is.

Thumbs up for trying but by your lack of responses recently I guess you have found it won't spin up.
Don't give up, just take a step back. You need to go to a gas turbine forum and talk to experienced builders and perhaps start with a bigger engine with a centrifugal compressor and an axial exhaust turbine. Get your eye in. and slowly sneak up on a pure axial, it's a monster of a mission
Jaycub (author)  marksteamnz3 years ago
I didn't realy expect it to work, at least not very well. I just wanted something that would look cool to submit to the epilog challenge and the makerbot contest. Thanks for the advice.
Hi Jaycub
I am agree with marksteamnz as i tried the project and found it not working. to get it working i increase the size of compressor so that more intake air can flow into combustion chamber. and this worked. also i opened the ball bearing covers and washed the excess grease which make them run smoother.
Jaycub (author)  rajat1sharma3 years ago
You actually got it running with a bigger compressor?
Yes it worked and runs fine.. but now trying to add a turbo prop to make cooler.
You need to clarify. You can not have got this design to run with a bigger axial fan compressor. With out many compressor stages of vastly improved sophistication the design will not run. As far as I can determine no amateur builder had ever got a home made axial turbine to run certainly not in the small sizes this instructable refers to. If you have used a centrifugal fan that is quite possible but that is not what is under discussion. Pictures or a youtube video would help clear up the confusion
Jaycub (author)  rajat1sharma3 years ago
Awesome! I'll have to re-work mine to have a better compressor. Can you post a video on youtube or some pictures?

Is there anything else you changed from what I show on this intructable that I would need to change to make mine work?
_Scratch_3 years ago
Argh! Don't cut the tubing with tin snips! Use a pipe cutting tool, the one that clamps down and spins around.
Hello Jaycub.. Great work ... your way of design is very simple and will definately runs.. I am waiting for your last steps.. I have already build till the step discribed..

Please get well soon and help us to finish this project.
Jaycub (author)  rajat1sharma3 years ago
Thanks. I can't guarantee it will work but I think it will. The only steps left are to braze the back of the combustion chamber to the center tube, and attatch the fuel lines ans igniter wires. You could be done before me! Be carefull if you test it.

I am already well but it is spring break so I can't use the high school's welders for a week.
I got most of the parts to build the engine. It sure would be nice to get the plans on how to finish it.
Jaycub (author)  fixitmankeith3 years ago
I'm working on it.
rimar20003 years ago
Video? This work deserves it.
Jaycub (author)  rimar20003 years ago
There will be a video by the end of the week if everything works out as planned.
OK, thanks. Please, then send me a PM.
Hi nice job, is there more? As how it is the tube attached to the pipe ? Could the blades be silver soldered in place? All of that wire does not look like it will be balanced to well.
Jaycub (author)  fixitmankeith3 years ago
This is not quite finnished, I had to post it like this to enter it in the epilog challenge. I have pretty sick since Friday. This instructable should be finnished within the next few days.