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Making a gas turbine engine

  1. Apr 27, 2007 #1
    Hello guys,

    I'm a second year BSc aerospace student in Holland, and I'm thinking about making a gas turbine engine. I hope to specialize in powerplants eventually. You people seem knowledgeable, so I thought I'd ask my question here.

    Anyway, bare with me a bit..... I first thought about making the whole thing (engine) from scratch, but while I was drawing the engine It occurred to me that it might take a long time before the thing gets finished. Not to mention the machine skills it would require to make all the parts. I went and talked to the keeper of our uni equipment center (a place where they have all kinds of machines with which you can do things to metals, like form them, etc), and he said it would a very long time to create the parts if the thing is too large... and that it would be difficult for me to make everything precise because I dont have much experience with the machines... anyhow..

    So then I thought I would go with the next thing... which would be to use a turbocharger, for reasons of not being able to get a turbocharger for less than 200 euro (260 USD), i'm not too exited about that either. (hey, im just a student :( )

    So then I hear that some people have created ramjets at home. Has it been done before? How would one go about creating a very fast air input? A leaf blower?

    Any help/comment would be appreciated... :)
  2. jcsd
  3. Apr 27, 2007 #2
  4. Apr 27, 2007 #3


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    You can also check out Jetzilla.com. They have a lot of valveless pulsejets there. Forget about a ramjet; they only work above 400mph or so.
  5. Apr 28, 2007 #4
    Thanks for the replies guys. I managed to get my hands on a 'cheap' turbocharger. :)
  6. Apr 30, 2007 #5


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    Make sure you're prepared for disappointment, and possibly death.
  7. Apr 30, 2007 #6
    Why on earth would anyone want to make a jet engine in their own house for? :confused:

    Why not just make yourself a bomb, same end result.
  8. May 1, 2007 #7
    I will tell you why. I believe that next to my studies I have experiment with these things in real, to fully understand them. What good is it if I'm constantly reading about how to calculate the efficiency, and I don't know what, if I'm not even able to work with these things in real.

    The only two parts where it could go wrong is if the compressor material can not handle ~80.000+rpm and just breaks apart, sending shrapnel everywhere. Or if the combustion chamber can not handle the expansions. Then again, the shrapnel could hit the gastank. Then you have gas in combination with a turbine which has a temp of 1000+ Celsius.

    Anyhow, if people like Ohain were afraid to make these things because it could explode, we would not have anything now.
  9. May 1, 2007 #8


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    You have the right idea, but you're not thinking about the practicalities. At 80 krpm, compressor rotors don't just break apart. They explode. Last year we had a turbine disc fail in one of our cells on a small engine and we were pulling metal fragments out of the wall for days. That is why test cells are ugly, brick and mortar lined rooms with very thick windows and doors.

    You NEVER keep the fuel containment in the cell with the engine. That stays outside and must have a safety solenoid valve in the line, near the fuel inlet at the engine for emergency shut downs. If that thing starts getting away from you, and it will, you need to have a quick way to shut it down.

    There are plenty of other ways things could go wrong. I would suggest you do a bit more reading and research. You need to be familiar with other aspects like dynamic shaft and rotor balancing. You need to understand how the burner operates. What about data acquisition? How are you going to load this engine? Are you going to create/measure thrust?

    You need to know how to be safe.
  10. May 1, 2007 #9


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    That reminds me of an incident at Avro while they were working on the Avrocar flying saucer. They had a catastophic engine failure which resulted in quite an inferno. An evacuation of the building was ordered and everyone was heading out. One engineer who was just arriving on the scene strolled in and disconnected the fuel line. End of problem.
    I was quite appalled that such a terrific design team hadn't included a fuel shut-off in their test rig. After a bullet-proof containment chamber, that should be the first safety precaution.
  11. May 1, 2007 #10

    I understand your curiousity of gas turbines. They are an amazing peice of technology. Its amazing to me that many people do not understand how they work, however they are one of the most simplistic engines, relatively speaking.
    I started your little venture about 2 years ago, and see that we thought alike. I wanted to create a gas turbine laboratory for my university. I wanted to build one (machine it) first, then I saw those "pulse" jets, then I went to the "turbocharger" one, and finally to this idea - which im suggest.
    First, dont machine one unless you plan on spending lots of money and you like to have parts fail many times. Second, pulse jets are cool, but you mise well look at a butane lighter because essentially they are the same. Third, the "turbocharger" gas turbine is about the most rigged thing you can do - yes, it conceptually gets the idea accross, but if you ever want to do "efficiency" calculations or any kind of calculations in that fact, dont go with that kind.
    Now this is what I ultimately decided to do - however, funding became an issue. There are several companies that manufacture affordable Micro gas turbine engines. They output about 100 pounds of thrust (which is plenty for demonstration) and they are electronically fuel injected with an automatic starting. They run anywhere from 600 USD -5000 USD Now this price is REALLY cheap compared to the time and effort of building one.
    Here are the websites to research these.

    So, see what you can get your hands into with these, I suggest going this route. Hope this helps,
  12. May 1, 2007 #11
    Well, I do appreciate all the worries and suggestions, and I will take more safety measures to protect myself and others.

    As far as 'data acquisition' is concerned. I sure do want to do that, but I'm still in the dark on how that has to be done. I don't have access to expensive equipment that can measure things in such extreme temperatures. So I'll have to look into cheap alternatives.

    Who wants to calculate things on a worthless engine (thrust/weight wise) you would probably think? I see this as my first step on the road to building the whole thing from scratch. I eventually hope to hand build every part of the engine, but that's probably years away from now. All I want to do now is get a first experience with these engines.

    The only way (for me) to get a firm grasp on jet engines, is to make them myself. That's a reason I would not buy a ready micro one. I think it's sad & pathetic that aerospace universities/faculties do not have their own jet engines to work with in a proper environment. (They don't in Holland).

    So anyway, I'm not looking into making a 'good engine' yet, I want a working one with which I can 'experiment'.
  13. May 1, 2007 #12
    Yeah, I agree totally. The only real way to get a firm grasp on jet engines is to build one.. However, alot of things have to go right for a gas turbine to function continuously.. and it will be extremely frustrating and very time consuming. I know for me.... producing results is a huge movtivating factor when working on a project (I tend to rush things, very bad habit) .. and I know that building one of these from scratch can take all your time and energy and never really produce a running engine. I am not trying to discourage you from building one. I am just giving my advice on experiences.
    Also, since gas turbine engines are very hard to come by (as you say at the universities in holland) having a running one around not only motivates you but others as well to build one from ground up. When having people excited about your project around you... is another crucial motivating factor.

  14. May 1, 2007 #13


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    You can easily get a thorough grasp on jet engines without building one.

    Fred, you're an industry professional. Have you personally ever built a gas turbine engine from scratch, from bits of raw metal to a finished running product?!
  15. May 2, 2007 #14
    I doubt it. Read all you want about something as simple as welding. After a year of reading about all the techniques, you still will not be able to weld better than someone who has practiced for two weeks.

    Why do you think doctors have practiced so much on dead animals and what not during their studies? According to you, they could have gotten a firm grasp of things through reading alone.
  16. May 2, 2007 #15


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    I guess technically we do that every day :tongue2:

    In college, my senior project was the closest I got when we took a turbo charger and put a can external burner on it and outfitted it with a heat exchanger (recouperator). We did efficiency calcs with and without the heat exchanger. We did no machining for the rotating group and we were doing this under the supervision of a small business that makes very small turbine engines. It was a great experience, but I did learn a ton of stuff from those guys. I shudder to think of all the things that can go wrong when I see/hear of people do this with no guidance the first time out.

    Admittedly, I now think about trying my own from scratch. I am pretty leery of doing it just because to really do it from scratch means a ton of developing my own hardware. Plus, it's not like I can walk into our foundry and pour my own engine case or have a 5 axis machine up my compressor rotors...It would be the same as you wanting to develop your own engine from scratch. I bet you have thought about it!!!
  17. May 2, 2007 #16


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    I agree with Brews. I guess it all depends on what you mean by "getting a grasp."

    There are tons of references out there that will go into every detail of design, maintenance and cycle calculations you could ever want. The things you can't get without some pretty in depth knowledge are things like effects of compressor blade design and so forth.

    Welding is not a good example to compare. Welding is, in comparison, a safe and relatively simple endeavor. To get good is an art form. It takes a ton of practice. The same with your doctor analogy. The point being is that we just want to make sure that you understand that, despite videos of people strapping them on go-karts and such, you are talking about a very unsafe project. It is compounded by your entry level knowledge and lack of experience. The people you see running engines in their garages and on mini bikes are fools and it will only take one failure to change their minds.

    Just be careful and remember this before you hit that igniter button every time: It is NEVER the details that you accounted for that will come back and bite you in the butt. If you get bit, it will be by something you never thought of.
  18. May 2, 2007 #17
    I agree wholeheartedly, the knowledge and experience you gain from actually "building" something from the ground up far exceeds that from reading or learning about it. Conceptually, you can do just fine with books or talking to someone but that only gets you so far. I have seen many A students go through an engineering program but do not know the first thing about practicality... You will never fully understand something unless you actually do it.

    Also, you guys are making this sound as if he wants to build a nuclear power plant with a risk of being exposed to radiation. This is a gas turbine. Yes, it is a bit dangerous - but only locally. Nothing that can't be solved from moving away a couple of feet or meters (whichever you prefer) or shielding it.

    The real question at hand is.... are these dangerous? The answer is yes and no. Yes, they are dangerous if your a grease monkey that slaps things together and goes to town. and No, if you are a intellegent person/engineer they are not dangerous. Because an intellegent person/engineer should always think about every aspect of the project, including not only the design, but manufacturability, cost, and safety. That is what they were hopefully trained for.

  19. May 2, 2007 #18


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    You're right. I don't know what I am talking about.
  20. May 2, 2007 #19


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    My comment about Fred singlehandedly building a jet engine from scratch was tongue-in-cheek, it's absurd to think that this would be the best way to gain expert knowledge on gas turbines. You'd learn a load about prototyping, but very little about gas turbines. Analogies to welding and surgery are ill-conceived; if you want to learn to machine jet engine components then do so, but it won't tell you a thing about their performance. Learning to weld a car chassis won't make you an expert in vehicle dynamics.

    There's a reason why Rolls Royce, GE and Pratt & Whitney have multi-million dollar R&D budgets. It's not just so that they can get a slight market advantage over each other, it's because even doing the most basic development work on even the most basic of these products is a huge task, requiring huge amounts of resources and huge amounts of expertise.

    If it was so easy for some guy with an engineering degree, a basic knowledge of turbomachinery and some workshop skills to build a working jet engine from scratch then they wouldn't bother so much.
    Last edited: May 2, 2007
  21. May 2, 2007 #20


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    C'mon guys, one of the things that is so great about this forum is that we have true experts in here. Listen to them!

    Those of you who are saying you can't understand how a jet engine works without building them are just completely missing what it means to understand how something works. No jet engine that you could cobble together with pare parts is going to be an accurate representation of a "real" jet engine, so it will tell you virtually nothing about how a jet engine works, much less what it actually takes to design/build a real one.

    To learn about efficiency, you read the efficiency equation and description in a thermodynamics book. Building your own poorly-designed (to put it generously) jet engine and plugging bad data into the equation isn't going to improve your understanding of how the equation works.
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