help in designing a small turbine

[El-Kablooey]

Getting a few books on the subject is a good idea, the main ingredience in a gas turbine is math and plenty of it... ;-)

http://geetel.net/~turbojer/gallery7.htm

This guy calls himself Turbojet and has a nice website with plenty of fun, he has built a "cheap" micro turbine with only the compressor wheel factory made. Many parts are made from stainless kitchen ware collected from stores.

If you have the right equipment and a bag full of patience something like this would be the way to go, it is heavy and produces little thrust therefore easier and cheaper to make and than a "real" flight engine.

//Anders

Hey, Turbojer has a pretty neat little site! Looking through his picture galleries I saw he has a nice PJ collection too, including a Solar valved PJ, and a gluey.

[Zippiot]

thank you so much for the link johansson!!

i have been looking through the main site, http://geetel.net/~turbojer/index.htm#where%20to%20go

and it is incredible. so many ideas tested over the years. the one i want to attempt, once i have the needed knowledge, is the tiny turbine with co2 cartidges as combustion chambers.

but that is where i want to be, surely not where i am. my first atempt, a few years back, was a modified soup can. it had only the front turbine, a small can as a flameholder/combustion chamber, and a small turbine in the rear...it actually did run but the bearings i used burned up in a matter of moments after start...i wont attempt it again cause i know it wont run correctly, i will make the next one a real turbine with compressors and all. no more half baked ideas with fire, i learned my lesson


on a side note, there is a cricket somewhere in my room and it is driving me insane!!!!!

[Zippiot]

reading through much material on the subject, i see that these turbines create very low compresison (2.2:1). wow...how do you get 16 lbs of thrust on that number? i think it is totally worth it to engineer a spinning stationary spinning staionary type turbine...
i have seen the tiny turbine that boeing made, it is 10 inches long 3.5 inches wide and has a compresison ratio of 35.6:1.

[Zippiot]

ok i gotta problem. i really want to design my own turbine...

the only part i need the design for is the compressor. my plan, however stupid it may be, is to make the tiny turbine using a computer fan as the front turbine. i know they can withstand 30k rpm, but these things tend to run in the 100k rpm's, however unlikely mine works that well...

i still need to machine the compressor and the rear turbine, but the housing should be a cakewalk to find. and flameholder is easy enough to make, nozzle might be dificult, just because i dont know what angle to make it, being the thing is my own design... well i can leave it off and run it at 0 thrust until i figure it out...

well...how bad of an idea is it, or is it feasible?

[Johansson]

Just a friendly advise, starting to invent a new and never tried before gas turbine is heading down a straight road towards failure. Look at what others have done and keep it simple, otherwise you will just be dissapointed.

//Anders

[Zippiot]

yeah i know, i was lookin at some tiny turbines. some ppl used wood for the front compressor, and made tiny soup can sized turbines from it. i just saw that the fan unit on a computer fits nicely inside of a soup can (chunky, has less than 1/16 inch clearance for a nice good seal) and, since the fans are already ballanced and have a driveshaft, seemed feasible...

i have been looking through the plans for the kj-66, its driving me crazy how many of the pages are upside down and if i rotate them they come out all fuzzy and are saved...well it looks like the thing can be scaled down to the size of a soup can with a little math

just thought it was worth a shot and the 2 bux worth of steel i would need.

[skyfrog]

Please also try Heward Microjet's WASP, as it is smaller, lighter, yet is more powerful than KJ66. it delivers 20lbs of thrust.

[Zippiot]

first things first, i gotta make a working model. i am going to start slow with this project, no more explosions in my garage...

im deciding between the kj-66 the one from kurt's book or making a soup can sized model...

[Fricke]

Thomas Kamps turbine design is an alternative. He even have some equations for scaling the engine size up and down. Based on the compressor size.

But if I may suggest: Make the first engine you build big not small... A bigger engine is more *foregiving* than a small one.

And as You wrote earlier, You don´t need the engine to be as effective as it can be. Schrecklings & Kamps designs are a good start...

Just my 2 cents worth...

//F

[Zippiot]

kamps is more complicated than the shrecky (my abbreviation cause i cant spell his name...even as i look at it). kamps book is a follow up to shrecky, his designs are improved for more power but are harder to make. definately gonna make the easiest to build first, then well see where i can go from there...

also does anyone have a pic of their compressors? or the front of the turbine with the cover off, i just need a good pic of what is down there...

[Zippiot]

well im debating the multiple compressor thing. actually no, i just want to know why it isnt done in tiny turbines, its the design used in all the big jets. is it just too complex for a small turbine or is it less efficient at that size?

by the context i see why i am confusing...by two turbine si mean, the one sin the front that scoops up air and the one in the back, which the buring fuel spins up. i know its the wrong name but when i type these posts i can never remember the proper name...

i was talking with a schoolmate about these things. he knows a lot but has never built any...
my first question was, how does water injection add power? i thought it was something to do with adding combustion chamber pressure, but he said something about the heat separating the hydrogen and oxygen which both burn...
the next was what heat does it take to melt stainless steel? is it somewhewre around 1500 or was it much less (not sure if it is celcius, check spelling, or farenheit...check spelling...)

[Johansson]

If your friend tells you that a gas turbine can split water molecules he probably doesen´t know as much as you think... *LOL*

//Anders

[Zippiot]

to be honest, he was just walking through autoshop and overheard my teacher asking about the scorch marks on my car...

something weird happened when i ordered the book...it says there is 1 in stock but shipping from 3k miles away will take 4-6 weeks...

i guess ill get it when i get it, until then ill have to use internet resources to start gathering parts.

[Zippiot]

ok, so while the book is in the mail im really bored, so i will do some experiments while i wait. i gotta few questions, i know they may seem dumb but im just getting background info, i cant trust everything i find on google...

so first question, what is the approx ratio of intake to combustion chamber? ratio of area i guess, but only at a cross section.
next, what is the ratio of length (total) to length (combustion chamber)?
next, intake to exhaust (not really important, i need to make it run before i weld on exhaust...)
ratio of area inside of flameholder to area of total combustion chamber?
are the compressor blades facing the same direction of the impellor blades? or do they point opposite?

well thats all i can think of for now...just remember i want to do some experiments while i wait for the book to arive, and the ratios im asking for are from your best designs, or easiest designs, or whatever you think will help the most.

thanx for all of your help so far, now all i gotta do is build the thing.

[Zippiot]

exactly wut i did a few days ago!!

i have been reading through the rules and such, but looking at the posts and pics i only see the turbo-turbines...


i picked up an airplane magazine while at the ymca today (brother had just had ankle surgery, so he had to do special stuff while i waited to drive him home). they had a 6 page section about the different styles of turbines, and they said just that. the axial flow compressor is vastly complex comapred to the centrifugal flow, but it is much more efficient at larger sizes and much smalled diameter. it is longer than the centrifugal type.

i also saw some things about the multispool turbines ( i think that is the name) its pretty much 2 or 3 different driven axial flow turbines inside of one shell. each can spin freely of the others, but obviously the big operates on different amounts of force than the small.

still, im surprized i cant find an axial flow turbine that is smaller than 3 feet long...

well now i got a challenge, to make an axial flow turbine while i wait for my book to arrive. will it work? probably not but its good experience to start building things that spin