Step 3: Figuring the size of the combustion chamber

Here is a quick rundown of the process of how the jet works and how to figure the size of the combustion chamber you will be making for your jet engine.

The combustion chamber works by allowing compressed air coming from the turbo's compressor to be mixed with fuel and burned. The hot gasses then escape through the rear of the combustion chamber to move through the turbine stage of the turbo where the turbine extracts power from the moving gasses and converts them to rotational shaft energy. This rotating shaft then powers the compressor attached to the other end to bring in more air to make the process continue. Any additional energy left in the hot gasses as they pass the turbine create thrust. Simple enough, but actually a bit complicated to build and get it right.

The combustion chamber is made from a large piece of tubular steel with caps on both ends. Inside of the combustion chamber is a flametube. This flametube is made of another smaller piece of tubing which runs the length of the combustion chamber and has many holes drilled in it. The holes allow the compressed air to pass through in certain ratios which are beneficial for 3 steps. Step one is mixing the air and fuel. The combustion process also begins here. Step to is to provide air for the completion of combustion, and step three is to supply cooling air to lower the temperatures before the airstream comes into contact with the turbine blades.

To calculate the flametube dimensions, you double the diameter of the inducer of your turbocharger, and this will give you the diameter of the flametube. Multiply the diameter of the inducer of the turbo x 6, and this will give you the length of the flametube. Again, the inducer of the turbo is the part of the compressor blades that can be seen from the front of the turbo with the covers (or housings) on. While a compressor wheel in a turbo may be 5 or 6 inches in diameter, the inducer will be considerably smaller. The inducer of the turbos I like to use (ST-50 and VT-50 models) is 3 inches in diameter, so the flame tube dimensions would be 6 inches in diameter by 18 inches in length. This is of course a recomended starting point, and can be fudged a little. I wanted a slightly smaller combustion chamber so I decided to use a 5 inch diamter flametube with a 10 inch length. I chose the 5 inch diameter flametube primarily because the tubing is easy to aquire as diesel truck exhaust pipe. The 10 inch length was figured because the engine will be going into the small motorcycle frame of the mini jet bike eventually.

With the size of the flame tube calculated, you can then find the size of the combustion chamber. Since the flametube will fit inside of the combustion chamber, the combustion chamber housing will have to be a larger diameter. A recomended starting point is to have a minimum 1 inch space around the flametube, and the length should be the same as the flametube. I chose an 8 inch diameter combustion chamber housing, because it fits the need for the airspace and it is a commonly available size in steel tubing. With the 5 inch diameter flametube, I will have a 1.5 inch gap between the flamtube and the combustion chamber housing. Try to use steel tubing instead of pipe when possible. The difference between 8 inch tubing and 8 inch pipe would be that the tubing would be measured at 8 inches outside diameter and you then select the thickness of the "wall" you need. I chose a 1/8th inch wall thickness for my engine. 8 inch steel pipe would have an inside dimension of roughly 8 inches and the wall thickness is determined by a schedule or strength number such as "schedule 40" or "schedule 80" Steel pipe tends to be much thicker in the "wall" than tubing, and can add considerably to the overall weight of the engine.

Now that you have the rough dimensions you will be using for your jet engine, you can proceed to putting it together with the caps on the ends and the fuel injectors. All of these parts combine to form the complete combustion chamber.
This might be a stupid question (they're really are stupid questions) where does the exhaust go when it's in the motorcycle frame?
After sending that comment I realized that I used the wrong they're. I meant to use there. I appologize to the whole of the Internet.
<p>actually, if you're referring to the they're in the parenthesis, you would be correct. there is referring to a location, not something like they're.</p>
However, you did misspell apologize...and that just will not cut it buddy.
I thought I checked all of the words.... I was mistaken.
<p>No no, he was right when he said he used the wrong &quot;they're&quot;.</p><p>they're really stupid questions would be correct, but what it should have been is </p><p>there really are stupid questions</p><p>J</p>
Okay, yup. After re-reading it, I was actually incorrrct myself. I read that as &quot;they're really stupid questions.&quot; My bad.
<p>well, i have some ideals on a jet engine design, use kerosene, it must have atleast 30 to 1 compression ratio for fuel to ignight. a kind of impeller on one side and a compression chamber on the oposite side, the turbine drive shaft would be attached to a starter/generator. exhaust into thrust. the faster it turns the greater pressure for combustion, i will have to build a working model.. jet engines use atmosphereic air vrs rocket engine carries its own oxigen</p>
I also had another question. You mention using jet fuel liquids. Would using gasoline be a bad thing? Would liquid propane work? Or natural gas? I do not want to start a debate about a hydrogen generator so I will not even add that.
I also had another question. You mention using jet fuel liquids. Would using gasoline be a bad thing? Would liquid propane work? Or natural gas? I do not want to start a debate about a hydrogen generator so I will not even add that.
Anything is possible after all you say one is available for 40k. <br>Possible by you and me? Seriously doubtful. Now while its not fair for me to judge your skills and resources, theres an old adage... (If you have to ask).<br>I did a Google search for &quot; turbine powered glider &quot; and then selected images. There is a lot of slick stuff out there. It seems there are quite a few 2 and 3 model turbines being used as sustainer's. My suggestion of using 4 might be over-kill, but as stated earlier it sure would look cool. What I see in my minds eye is something like the De Havilland Comet, only a glider profile.
<p>I am F.Russell Grice i like to try my Grice-Device Fuel-Expander on a turbine engine to see how many more MPG it get them? A auto gets 5 to 16 more MPG look scnow.comgricedevice read Grice-Device can help streatch miles per gallon?</p>
<p>Curious about the weight to thrust ration? Wondering if a small light weight version could be made safe enough to fit inside a 800 lb glider and used as a sustainer engine.</p>
<p>You might look into model aircraft turbines. There a bit pricey at <br>2500.00 per engine new, and only about 15lbs of thrust so you will need <br>at least 4 engines to work as &quot;sustainer engines&quot;. This would give <br>60lbs thrust. Still kinda light but If my memory serves me correctly <br>gliders have a 20:1 or better glide ratio (I think). 40 to 60 - <br>Wikipedia. So 4 engines should work pretty good as a sustainer. And all <br> for a mere 10,000.00. Rest assured you would have the slickest <br>personal glider on earth. I would duct them with two in each wing if <br>possible as they are only about 6&quot; in diameter. If you build it I want a <br> photo.</p>
Glider manufactures build one today, single sustainer, 40 lbs and it mounts into the fusilage behind the seat pilot seat, at near center of gravity. At the press of a button a hatch opens, the sustainer appears and you start engine, works in reverse also. I was wondering if this might be a possible build. You can buy it for $40k.
<p>Your own personal U2...</p>
<p>Excuse me but the web site: http://icdn4.digitaltrends.com/image/2015-mercedes-benz-gla45-amg-rear-spoiler-2-1500x1000.jpg-- does NOT belong in my writings. I was trying to cut n paste. and it did NOT cut, but it pasted a photo of a Mercedes AMG. Sorry</p>
<p>Sorry for the misplaced reply comment. The comment about the sustainer's was meant for someone else.</p>
<p>You might look into model aircraft turbines. There a bit pricey at 2500.00 per engine new, and only about 15lbs of thrust so you will need at least 4 engines to work as &quot;sustainer engines&quot;. This would give 60lbs thrust. Still kinda light but If my memory serves me correctly gliders have a 20:1 or better glide ratio (I think). 40 to 60 - Wikipedia. So 4 engines should work pretty good as a sustainer. And all for a mere 10,000.00. Rest assured you would have the slickest personal glider on earth. I would duct them with two in each wing if possible as they are only about 6&quot; in diameter. If you build it I want a photo.</p>
Never gonna work unless you start at the beginning. <br><br>Now build a miniure arc reactor and have someone drill a hugehole in your sternum so you can mount it. For sake of ease just rout the interface wiring just route the wires out down below.<br><br>Go ahead an start building your suit, by the time you are ready to power it there should be a viable engine of some kind. Lol<br><br>Do not attempt any of the suggestions in this message as they are probably dangerous and were meant as humor. I know not too good huh?<br><br>Anyway, cheers all
<p>okay i know this sounds stupid but im wanting to make a real working ironman suit but i need to know how to make to turbine small enough to fit the hand and feet so my suit can fly. i need some help. more or less hands on help.</p>
<p>Sorry to say, but you'll never be able to make it actually fly (for a couple of reasons). First off, if you make the turbines small enough to fit in your palm (literally), then they would not have nearly enough power to lift you off the ground. Second, Jet Engines produce huge amounts of heat, and so you would have singed hands if you ever tried. Also, Jet Engines need a large amount of air traveling (more or less) in a linear direction, so unless you have a large hole in your hand to allow air to enter the turbines, you would have a lot of trouble pumping through enough air. Lastly, unlike in the movies, controlling flight with the center of thrust(s) being the ends of your limbs is really difficult. Really cool idea though :)</p>
<p>This is actually wrong, anything is possible. The trick is having he lines stronge enoguh to support the pressure. As long as lift exceeds weight yo have flight. With .1% of atmospheric change you get 212 lbs of lift. Do with as you will!</p>
<p>Listen, I work on an aircraft that has one VERY large augmented jet engine (F110-GE-100), with a maximum thrust of 28,000 lbs and a dry weight of roughly 4,000 lbs (no fuel). 28,000/4,000 = 7. That is a Thrust to weight ratio of 7:1. For the purposes of math, the average (looks like most of us are men) male weighs ~180lbs plus the weight of the suit, lets say at least 80 lbs. Therefore (180 + 80 = 260) lbs / 7 = ~37 lbs for the engine running at MAX not factoring in the weight of the engine in the suit, the thrust necessary to sustain flight with fuel onboard or protective equipment given that the turbine inlet temperature can hit 1510 degrees Celsius. Using the same ratio applied to my jet. This engine will consume ~78 lbs of fuel per 1 flying hour (NOT AUGMENTED/NO BURNER) (78/6.7=11.6G*3.62(for FY2014)=$42/hr). The added weight of fuel will bump your engine size up to roughly 48 lbs (for 1 hr flight time). And thus, you will be putting a 180lbs man in a 80(suit)+48(eng)+78(fuel&lt;1hr)=206lbs for the whole suit minus the pilot, safety equipment, the ACTUAL size of the engine given that I got lazy with my math earlier, and no flight controls (fly straight until you hit something). There is much more but you get the picture. The total weight with all of these things would weigh ~300-350lbs, which makes it impractical given that the pilot probably cannot hold it up. </p><p>All that being said, you would be better off using an external combustion engine (chemical rocket engine), or you could do humanity a HUGE solid and start researching/developing a more efficient hall effect thruster. But please, for your's and everyone else's safety, please don't actually try to make an Iron Man suit. Failure to comply may result in injury or death to personnel.</p>
<p>You should be more worried about him succeeding. Injury and death by accidents is a hell of a lot better than knowing there's a walking flying death machine that can go anywhere and destroy anything. </p>
Yeah and if you dropspit on the floor screen, before you caraformer acetate you can go back in time.
<p>idk if you could fly, but there are lots of people who have built Iron Man's blaster thingies</p>
Use plasma engines
<p>Watch this:</p><p>https://www.youtube.com/watch?v=Czy0pXRRZcs</p>
Im pretty sure iron man doesnt yse simple turbine engines for his advance suit,one if the engines where that small it would not work and two in the movie he has flew in space and water.
<p>It's not real... It's a movie. Special effects, photoshop, cgi...</p><p>Gesh, next people will think the cgi effects used by Nasa for the planets and all are reall on the spot photos...</p>
I can see no advantage of having thrusters mounted in the hands and feet; it would make the hands of the suit clumsy and not very good at other tasks. It would also be impossible to control. Central on the back is the best place for a thruster, out of the way.
<p>Based on the reply from the aircraft guy, I would suggest you add a hook to the back of the suit and using relatively invisible line, simply hoist the man in the suit into the air for your YouTube Video. You can use software to edit out the lines just like they do in the movies. Iron man really doesn't fly its done with greenscreen and cables with very good editing.</p><p>Get some fireworks to create the illusion of rocket power and there you go. Up, up in the air. Its Iron man....</p>
I don't think it is stupid and not possible. And, it doesn't have to be the same as the movies. It needs a lot of knowledge and enthusiasm. I don't have too much aerodynamic knowledge but I could join you if u r serious.
I've been wondering if a &quot;quad&quot; type thing can be made with jet engines
<p>This thing is so far beyond the capability of 99.99% of instructable-types (including me). But I just love reading creative &quot;logic&quot; especially when it seems so Rube Golberg-ish. Colossal entrainment! Thanks!</p>
<p>Oh my good LORD !! Wouldn't it be totally awesome if we ALL had jet turbine engines? They run on practically anything combustible (like the Chrysler gas turbine of 1965//Leno's got one.) No phttp://icdn4.digitaltrends.com/image/2015-mercedes-benz-gla45-amg-rear-spoiler-2-1500x1000.jpgistons, rods, crank, rings, camshaft, lifters pushrods, rocker arms, valve springs, valves oil seals NONE OF THAT. A simple gas turbine and NO it's NOT THE MAZDAAAAH Wankel either. Check out the sites--wow!</p>
<p>There is a guy who built what has to be the most intricate turbo jet engine. His site is www.rcdon.com. Check it out if you are looking to build one of these.</p>
<p>These incidents modern machine needs a skilled engineer team a great team of workers.</p><p>http://www.friv8.in </p>
<p>This instructable is from 2006. No wonder the links are dead. This one should be canned...</p>
<p>Just tried the links and videos at the bottom of the 'structable, no go. The sites have both gone dark and are now place holders and the videos are messed up, VLC wouldn't even show the videos - so be wary. The build however looks impressive.</p>
I am trying (somehow) to put this together with a waveboard to make it hover at least a foot. can anyone help?
f=ma my friend. it is the most important thing you will ever learn.
I'm assuming that f = either force or fuel. m = mass. what is a?
force = mass * acceleration. Newton's second law of motion.
<p>Gravity should be included in the calculation. Newton wasn't in touch with gravity in space or black holes, etc.</p>
i thought it was the third law of motion?
Nope, it's the second law:<br> <br> From http://en.wikipedia.org/wiki/Newton's_laws_of_motion<br> <br> Second law: A body of mass m subject to a force F undergoes an acceleration a that has the same direction as the force and a magnitude that is directly proportional to the force and inversely proportional to the mass, i.e., <strong>F = ma</strong>. Alternatively, the total force applied on a body is equal to the time derivative of linear momentum of the body<br>

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Bio: I guess I consider myself a born tinkerer and mad inventor of sorts. I like to take projects, modify them, push them to the next ... More »
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