Introduction: How to Build a Jet Engine!
More by the author:
About: I'm a Mechanical Engineer who has been a part of this community for over 10 years! My interests have evolved over time, and now center around 3D printing.
I have wanted to build a functioning, jet turbine engine for quite a long time. To me, there's something awesome about the way in which so many different aspects of a jet engine come together to make a functioning unit, that is able to propel massive objects into the sky. I actually tried to make a jet engine out of tin cans years ago! It was one of my first instructables: https://www.instructables.com/id/The-Recycled-Jet-Engine/. Perhaps one of the biggest lessons from that project, was that jet engines shouldn't be made out of tin cans.
This past summer, I had the opportunity of a lifetime to be accepted as an Artist in Residence at Instructables. With all of the new resources I knew I'd have available, I thought this would be the perfect opportunity to try to do a massive project, something that I knew I wouldn't be able to do at home. I knew I had to try to make a functioning jet engine, like I've always wanted to, but knew I didn't have the resources to do so. I poured all of my efforts into the project, and learned so much by doing it.
With that said, I'd suggest you grab a beverage if you intend to read all the way through. The actual complexity of this project didn't hit me until I was discussing it at my final Artist in Residence presentation. To read more about my AiR experience, feel free to check out my forum post here: https://www.instructables.com/community/Fozzy13s-AiR-Experience/
This past summer, I had the opportunity of a lifetime to be accepted as an Artist in Residence at Instructables. With all of the new resources I knew I'd have available, I thought this would be the perfect opportunity to try to do a massive project, something that I knew I wouldn't be able to do at home. I knew I had to try to make a functioning jet engine, like I've always wanted to, but knew I didn't have the resources to do so. I poured all of my efforts into the project, and learned so much by doing it.
With that said, I'd suggest you grab a beverage if you intend to read all the way through. The actual complexity of this project didn't hit me until I was discussing it at my final Artist in Residence presentation. To read more about my AiR experience, feel free to check out my forum post here: https://www.instructables.com/community/Fozzy13s-AiR-Experience/
Step 1: Testing - Video
Testing was difficult to actually do. I just performed the first round of testing, and didn't exactly get the results I wanted. That said, I filmed most of the first round of testing in eight inches of snow, so I think some credit should be granted. Further testing will be done when I'm not away at school, because jet engine testing isn't exactly possible on campus.
The engine naturally wanted to run backwards, and so in these tests, I let it run that way. In the next round of testing, hopefully with some dry conditions, I hope to have a larger air supply to help force the compressor into functioning better than it did in this first round. That said, the engine did in fact propel itself during short portions of my testing, even if it isn't completely obvious in this test.
The engine naturally wanted to run backwards, and so in these tests, I let it run that way. In the next round of testing, hopefully with some dry conditions, I hope to have a larger air supply to help force the compressor into functioning better than it did in this first round. That said, the engine did in fact propel itself during short portions of my testing, even if it isn't completely obvious in this test.
Step 2: Theory of Operation: How a Jet Engine Works
Before one being build a jet engine, it's important to first know how a jet engine works. Luckily, the internet is a fantastic resource for this sort of thing, and one can spend hours researching and watching YouTube videos on how they work, and different homemade versions that people are showing off.
Let's break everything down simply before we proceed.
The first place I started when I first became curious about jet engines was HowStuffWorks, so I'd like to direct your attention to their article here: http://science.howstuffworks.com/transport/flight/modern/turbine.htm
Let's break everything down simply before we proceed.
- Intake: The "compressor/intake turbine/intake fan" pushes and compresses air into the engine.
- Mix and Burn: The air flows past the "flame tube/flame holder", mixing with the fuel. The fuel/air mixture is then ignited and burned.
- Exhaust: The burned fuel and air moves out the back of the engine, and forces the "exhaust turbine/exhaust fan" to spin. This in turn rotates the shaft, which causes the intake turbine to continue to spin, and continue the cycle.
The first place I started when I first became curious about jet engines was HowStuffWorks, so I'd like to direct your attention to their article here: http://science.howstuffworks.com/transport/flight/modern/turbine.htm
Step 3: Working Design/Overview
The following explains the different components of the jet engine I built. Consider this applying what we learned about how a jet engine works in the previous step, to the more specific design of what we'll actually be making.
As an overview, here are some things to keep in mind while we set forth on this adventure of building together.
- Intake: I chose a centrifugal compressor for my intake compressor. A centrifugal compressor sucks air in from its center and forces it to its outside edge. I chose this type of compressor because this would allow me to place my flame tubes on the outside of the engine, and keep the heat of combustion away from the shaft of the engine. Keeping heat away from moving parts as much as possible will keep the engine running longer and safer (hopefully). Additionally, I knew that I could find a centrifugal compressor in a vacuum cleaner motor, so that was one part I wouldn't have to make.
Don't know what a centrifugal compressor is? Check out THIS, or THIS. - Mix and Burn: Using propane as our fuel of choice will make mixing with air extremely easy, since it's a gas at room temperature. Therefore, the fuel will not have to be atomized before burning, as with liquid fuels. Tungsten spark plugs are used to ignite the fuel. The idea is to light the fuel, and have a sustained flame within the engine.
- Exhaust: The exhaust turbine was cut using the Omax water-jet cutter at the shop. I decided that this would be the easiest way to get the most perfectly symmetrical turbine possible, and be able to make it to fit the rest of the body of the engine.
As an overview, here are some things to keep in mind while we set forth on this adventure of building together.
- Most, if not all, of the cutting for this project was done on a vertical band saw, with cutting fluid.
- Most, if not all, of the drilling was done using a drill press, where holes were marked, struck with a hammer and nail to form a dent, and then drilled.
- All welding was done using a TIG welder. I was fortunate enough to have an experienced metalworker and previous AiR, sheetmetalalchemist, teach me TIG welding. I am eternally grateful.
- All metal used in this project unless specified otherwise is Stainless Steel 316
- WHY: When researching the various grades of stainless for this project, and the different ballpark temperature estimates for jet engines, all the numbers looked like NO grade of stainless steel would be able to withstand the heat generated by a jet engine. Therefore, I chose 316, because it has a nice balance of a lot of different properties, was available in a lot of different shapes and sizes, and I had worked with it in small amounts in previous project
Step 4: Main Ingredients
This step is titled "Main Ingredients", because as I keep reading and writing Instructables, a full, detailed, list of materials seems somewhat redundant. Therefore, here are main components that were used in making the jet engine.
-copper tubing.
-stun guns/spark generator
-propane source. regulator?
-probably high temperature silicone stuff for in between joints
-3 brass barb tees
-3 spark plugs
-silicone tubing
- Vacuum cleaner motor fan, 4.7835" diameter
- Stainless steel square tubing 1.5" diameter, 2 feet long
- Stainless steel square tubing 1" diameter, 2 feet long
- Stainless steel plate 6"x6"x1/8"
- Stainless steel plate 12"x12"x1/16"
- Stainless steel plate 12"x12"x3/32"
- Stainless steel bar 1" wide 6ft. long
- 5/16" diameter stainless steel threaded rod, bolts, washers, lock washers.
- 5/8" diameter 12" long round stainless steel bar stock
- Ball bearings. I bought two sets, as close to the appropriate size as possible.
- Three spark plugs
- Coleman camp stove propane and regulator
- A variety of plumbing adapters, see step
- 5/8" diameter vinyl tubing
- 5/8" hose clamps
- Stun gun
- Alligator clips/wire
-copper tubing.
-stun guns/spark generator
-propane source. regulator?
-probably high temperature silicone stuff for in between joints
-3 brass barb tees
-3 spark plugs
-silicone tubing
Step 5: Flame Tubes Pt. 1: Taper
12 More Images
The Flame Tubes are made primarily using 1/5" diameter and 1" diameter stainless steel square tubing.
A 5" long section of 1.5" diameter stainless was cut, and each end had to be shaped differently. One end will need to be tapered, taken from a larger diameter to a smaller diameter.
TAPER:
In my turbine engine there will be three combustion chambers. These will be built and tested before anything else is done to make sure that the core of the engine is working.
A 5" long section of 1.5" diameter stainless was cut, and each end had to be shaped differently. One end will need to be tapered, taken from a larger diameter to a smaller diameter.
TAPER:
- Mark two lines one inch in length on the top of the piece, immediately next to the walls of the tube.
- Mark two spots toward the middle of the tube, so that the distance between them is one inch.
- Cut along the two lines using the vertical band saw. Be sure to cut as close to the wall of the tubing as possible.
- Cut a wedge shape out of the tubing on each side, but cutting from the two spots to the end of each cut line.
- Use needle-nose vice grips, and any other means possible, to bend the cut sides toward the center of the tube.
- Once bent, use the vertical band saw to trim away excess metal on each side. These will be triangle-shaped pieces similar to what we marked on the top side.
In my turbine engine there will be three combustion chambers. These will be built and tested before anything else is done to make sure that the core of the engine is working.
- Using a big spinning wet circular saw thing, cut a 5" length of 1 1/2" diameter stainless steel square tube.
- Make a cut at an angle on one end of the cut piece to form the angled end that will connect to the fan shroud.
- Make 2-4 angled triangle cuts on the other side of the tube to form the compression end of the tube.
- Weld all the joints that were just cut.
- Cut a 5" length of 1" diameter stainless steel square tube.
- Use a drill press to drill holes for the fuel input and spark plug.
- Weld the section of 1" tube to the section of 1.5" square tube.
- Cut a 3" length of 5/8" stainless steel rod.
- Orient the 3" section vertically in a vise or clamp, and use a drill press with a 1/4" bit to drill all the way through the length of rod.
- On one end of the rod, use a 3/32" drill bit to drill multiple small holes horizontally through it.
- Weld the 3" section of stainless rod to square tubing in the fuel input hole.
Step 6: Flame Tubes Pt. 2: Angle
6 More Images
The other end of the 1.5" diameter section needs to be closed off, at an angle to direct the air that will be flowing into the engine.
ANGLE
Even though all the metal was bent into place as best as possible, a multitude of clamps had to be used to hold everything in place, and squish it together to be welded. This was largely made up as I went along, and so I'd advice looking at the pictures.
ANGLE
- Mark two lines 1.5" long on the top of the piece, immediately next to the walls of the tube.
- Clamp the piece in a vice, and use a hacksaw to cut along the lines that were just marked. It is important here to cut through just the top side of the tube, not also through the bottom. This is why a hacksaw is used, and not the vertical band saw.
- Use a vice, and carefully angle the piece that was just cut in it, so that the corner of the jaws of the vice will bend the cut section inward. I was not able to bend the cut flap fully down to the bottom of the tube, but it was close enough to be welded in place.
- Use a vertical band saw to cut away excess metal surrounding the cut flap that was just bent downward.
Even though all the metal was bent into place as best as possible, a multitude of clamps had to be used to hold everything in place, and squish it together to be welded. This was largely made up as I went along, and so I'd advice looking at the pictures.
Step 7: Flame Tubes Pt. 3: Burner
21 More Images
The first image of this step is a good picture of what we will make in this step.
I used two one-foot long, one-inch diameter sections of square stainless steel tubing for the second half of the flame tube. These pieces are where the fuel will be ignited, burn, and be routed to the exhaust turbine.
I decided that the smaller diameter portion of each flame tube should be 5 inches long, like the former, but instead cut three 6" pieces. I decided that cutting down each completed flame tube to the appropriate size would be easier to do at the end, then try to make everything match up perfectly after all of the cutting and welding was done.
-
BURNER:
I used two one-foot long, one-inch diameter sections of square stainless steel tubing for the second half of the flame tube. These pieces are where the fuel will be ignited, burn, and be routed to the exhaust turbine.
I decided that the smaller diameter portion of each flame tube should be 5 inches long, like the former, but instead cut three 6" pieces. I decided that cutting down each completed flame tube to the appropriate size would be easier to do at the end, then try to make everything match up perfectly after all of the cutting and welding was done.
-
BURNER:
- Cut a 6-inch piece of 1" diameter stainless steel tubing.
- Mark and drill a 5/8" diameter hole for the fuel inlet. Mine was centered, 3/4" from the end of the tube that will be welded later to the tapered end of the 1.5" diameter tube.
- Mark, drill, and tap a 1/2" diameter hole for the spark plug. This hole was centered roughly 3/4" from the center of the hole for the fuel inlet.
- Using the vertical bandsaw, cut three 3" sections of 5/8" diameter stainless steel rod.
- Carefully affix each section in a vice, and use a drill press to drill a 3/8" diameter hole all the way through the length of the rod. This will be no easy task. Patience is key here, as is proper placement, and plenty of cutting fluid.
- Use drill press and vice again to drill many small holes, around 1/8" diameter through one end of the tube. This will help disperse the fuel and air in the engine, so that a sustained flame can be created. Many times, this is called a "flame holder". This again will not be easy, and you may or may not break a lot of drill bits in the process.... (sorry). It would be a good idea to use some sandpaper to make the outer surface of the rod rougher, to allow the drill bits to take hold.
- This piece will but pushed firmly into the 5/8" diameter hole that was drilled in the section of 1" diameter square tube.
Step 8: Flame Tubes Pt. 4: Welding/Finishing
12 More Images
Welding was done kind of as I went along, and so writing specific directions for this seems unnecessary. Welds should be placed:
A 7/8" hole was drilled in the center of the 1.5" diameter tube close to the angled end.
The 1" diameter end will then need to be cut/ground so that the 7/8" diameter holes are all the same height if all of the tubes are standing up next to each other.
- Along all the seams that were made as different parts of the tube were cut and bent
- Around the edge where the fuel inlet contacts the flame tube
- Where the tapered 1.5" diameter square tube comes in contact with the 1" diameter tube
A 7/8" hole was drilled in the center of the 1.5" diameter tube close to the angled end.
The 1" diameter end will then need to be cut/ground so that the 7/8" diameter holes are all the same height if all of the tubes are standing up next to each other.
Step 9: Build: Exhaust
23 More Images
The exhaust consists of an end plate, and two sections of bar stock bend into a circle, all welded together. The exhaust turbine goes inside of that housing.
The end plate is made of 3/16" stainless steel plate. This was cut on the water-jet cutter in the Instructables shop, that way all the holes could be perfectly spaced out along the outside. The three square holes needed to be 120° apart, where the exhaust will enter the exhaust turbine.
Because the water-jet cutting didn't turn out perfectly, a few weld beads needed to be placed on the inner circle, to allow the bearings to have a tight fit.
A 6-foot long section of 1" wide bar stock was purchased, and bent into two large rings, using a combination of the metal bender in the shop, a vice, and brute force. The appropriate perfect-circle-making metal bender was not available in the shop.
The exhaust turbine was cut using the Omax water-jet cutter at the shop, after being drawn in Inkscape. It was then placed in a vice, and vice grips were used to carefully bend each blade to a 10° angle. A mark was drawn on the vice with marker to easily identify how far each blade needed to be bent. Ideally, the exhaust gases would come into contact with the blades at a 90° angle. Because this isn't possible with our design, the impact angle will be slightly wider.
Throughout this process, I kept checking to make sure everything fit appropriately. In the pictures you can see a piece of wood cut in the rough shape of a turbine in place of the actual one. This was a test piece used for sizing, to avoid risk of damaging the actual turbine while lining things up.
-
1. Inkscape is an open-source vector graphics creator. If you've heard of Adobe Illustrator, this is like a free version of that program. I'm using it because it's free and available, but feel free to use your vector-graphics editor of choice. Inkscpae is able to save files in *.dxf, which is the format the Omax wants.
The end plate is made of 3/16" stainless steel plate. This was cut on the water-jet cutter in the Instructables shop, that way all the holes could be perfectly spaced out along the outside. The three square holes needed to be 120° apart, where the exhaust will enter the exhaust turbine.
Because the water-jet cutting didn't turn out perfectly, a few weld beads needed to be placed on the inner circle, to allow the bearings to have a tight fit.
A 6-foot long section of 1" wide bar stock was purchased, and bent into two large rings, using a combination of the metal bender in the shop, a vice, and brute force. The appropriate perfect-circle-making metal bender was not available in the shop.
The exhaust turbine was cut using the Omax water-jet cutter at the shop, after being drawn in Inkscape. It was then placed in a vice, and vice grips were used to carefully bend each blade to a 10° angle. A mark was drawn on the vice with marker to easily identify how far each blade needed to be bent. Ideally, the exhaust gases would come into contact with the blades at a 90° angle. Because this isn't possible with our design, the impact angle will be slightly wider.
Throughout this process, I kept checking to make sure everything fit appropriately. In the pictures you can see a piece of wood cut in the rough shape of a turbine in place of the actual one. This was a test piece used for sizing, to avoid risk of damaging the actual turbine while lining things up.
-
1. Inkscape is an open-source vector graphics creator. If you've heard of Adobe Illustrator, this is like a free version of that program. I'm using it because it's free and available, but feel free to use your vector-graphics editor of choice. Inkscpae is able to save files in *.dxf, which is the format the Omax wants.
Step 10: Build: Intake
15 More Images
The intake for the engine is probably the "least clean"/"most poorly planned" part of my project.
The original plan was to use the shroud from the vacuum cleaner motor to snap/bolt on to the engine. Due to the thin walls of the shroud, this wasn't going to work. I was stuck, and kind of scrapped together a shroud using left over 1" bar stock from making the exhaust. The following are directions for what I should have done from the start, and did some version of as I struggled to fix a flawed design.
The original plan was to use the shroud from the vacuum cleaner motor to snap/bolt on to the engine. Due to the thin walls of the shroud, this wasn't going to work. I was stuck, and kind of scrapped together a shroud using left over 1" bar stock from making the exhaust. The following are directions for what I should have done from the start, and did some version of as I struggled to fix a flawed design.
- Use a laser cutter to mark a 6"x6" piece of stainless steel sheet.
- Use a vertical band saw to cut out as much of the circle as possible, and use a vertical belt sander to smooth out the edges. This will make our "intake plate, similar to the "end plate" in the last step.
- Use a drill press and vice to drill a 3/4" circle out of the center of the piece. This is where the bearing will sit.
- Align the flame tubes, intake plate, and end plate, all together, using the threaded rod that will become the shaft. Weld the intake plate to the flame tubes.
- Using a vertical band saw, cut three, 3-4" long pieces of 1" stainless bar stock.
- Using a hammer and vice, bend each piece into an arch to match the circle of the intake plate as best as possible.
- Place each piece on the engine in between each flame tube, and weld each in place.
Step 11: Finishing Pieces
8 More Images
Intake shroud pt. 2: Pictures 1-4
Fuel fixture: Pictures 5-11
This will be used to disperse the propane to each of the three fuel inlets, on each of the three flame tubes, of the engine.
- Using leftover sheet metal, cut out rectangles, arrange them with a hole in the center, and weld them together.
- Weld three stainless steel nuts to the stainless bar stock portions of the intake shroud made in the last step.
- Drill and tap three holes, aligned with the nuts, so that the sheet metal rectangle can be bolted on to the intake shroud from the last step.
Fuel fixture: Pictures 5-11
This will be used to disperse the propane to each of the three fuel inlets, on each of the three flame tubes, of the engine.
- Drill a 3/8" hole through the center of left over 5/8" stainless rod.
- Cut the rod into four pieces.
- Drill two 5/8" holes in a small pieces of leftover 1" diameter stainless square tube.
- Place a piece of the 5/8" rod in each end of the square tubing, and the two holes that were drilled.
- Weld all the pieces in place
Step 12: Fuel System
17 More Images
We will use propane as our fuel source for the jet engine, as explained previously. The companies who make small propane bottles try really hard to make sure you can't easily get to the wonderful flammable goodness, which makes this part challenging. I first bought a Coleman propane stove regulator, so that I would be sure no propane would leak out of the adapter at the bottle.
The regulator came with a second valve built into the end of the regulator, which I decided to use as a sort of on/off valve. This was accomplished by bending brass rod into strange shapes, and forming a sort of hook-and-latch assembly to slide into the end of the regulator and push the built-in valve open. This involved drilling through the end of a brass elbow, and using epoxy to affix a small piece of brass tube in place so that a gas-tight, yet slideable junction was made.
A variety of plumbing adapters were then used, and epoxied together liberally to form a system of valves and fittings that would regulate the flow of propane with no leaks, and end in a 5/8" hose barb adapter. This entire process was challenging, and there has to have been a better way to do it, but this is what I made work.
The regulator came with a second valve built into the end of the regulator, which I decided to use as a sort of on/off valve. This was accomplished by bending brass rod into strange shapes, and forming a sort of hook-and-latch assembly to slide into the end of the regulator and push the built-in valve open. This involved drilling through the end of a brass elbow, and using epoxy to affix a small piece of brass tube in place so that a gas-tight, yet slideable junction was made.
A variety of plumbing adapters were then used, and epoxied together liberally to form a system of valves and fittings that would regulate the flow of propane with no leaks, and end in a 5/8" hose barb adapter. This entire process was challenging, and there has to have been a better way to do it, but this is what I made work.
Step 13: Electrical System
The "electrical system" of this project is hardly of note. I chose to use an inexpensive stun gun to generate the sparks for the spark plugs to light the fuel inside the engine. Alligator clips were used to connect the output terminals of the stun gun to the connections for the spark plugs. Because the gap of the spark plug is shorter than that of the stun gun, the spark will chose the path of least resistance at the spark plug. The flow of the burning fuel will allow other flame tubes to ignite once the first one is successfully lit.
Step 14: Conclusion
This project as mildly successful. I'd like to reiterate that this by completing this project, I learned a great deal, and it was incredible to have the opportunity to do so. Some things I would have done differently are as follows:
Thank you for reading! Feel free to leave a comment, rate this Instructable, and/or subscribe. Getting feedback on my projects is always motivation to keep building and publishing. Thanks!
- Math!: Truth is, a great deal of more calculations and measurements probably should have been done before building began. I should have approached this project less as an artist and more as an engineer.
- CAD: For the most part, the extent of my design was done with pencil and paper, and I went ahead and attached my drawings. I reached a certain point in the project where I looked back and it seemed silly why I didn't take the time to learn some AutoCAD to improve the overall quality of my project, and help avoid some bumps I experienced during the build.
Thank you for reading! Feel free to leave a comment, rate this Instructable, and/or subscribe. Getting feedback on my projects is always motivation to keep building and publishing. Thanks!
We have a be nice policy. Please be positive and constructive.
83 Comments
Flag
I'm no expert but I have done a lot of reading on the topic (as well as in the process of building my own) and roughly 80% of thrust in an axial turbine comes from the air moving around the combustion chamber/s, in a housed jet engine. As you already know, the purpose of the combustion chambers is to take the compressed air, mix it w fuel and you are left with a force that turns the rear blades, in turn exerting the energy through the stator to start the process all over again in the front. So the front fan blades are turned at a faster and faster pace (Depending on how much fuel of course) so not only is the air compressed into the comb chambers but it is compressed around them too as it flows through the narrowing spaces between the comb chambers and the engine housing, producing around 80% of the thrust out of the rear, if all is calculated correctly. Just my two cents but I really like your project! Wish I had the resources you do! Kudos to you and keep at it, you have the makings for something great! And thank you so much for sharing your process and final piece! Inspiring!
Flag
please language change to myanmar
1 reply
Flag
Try some friends, that are good in EN, because i think it is not possible for creator to do that
Flag
Hi my friend you should try to enter the air from the other entry and you have to check if there is air leaks
You did a great job and you have nice ideas you are so smart I think you have the big fan is shaking you just have to check it please my friend
ByteScout BarCode Reader.lnk
Flag
Did this ever work.
Flag
you could connect a motor to axle
Flag
2 questions,
1. How light can this engine get?
2.What would be the maximum thrust posssible?
Flag
So you look like you know a little. I´m 15, A DIY Engineer My self and want to submit somthing for a scholarship science fair, I want to build my own jet engine, I had alot of questions I got answers to on google and stuff, and I am to this: I am going to Get Sheet metal and Cut the propeller blades, then Im going to build my combustion chamber using an old oil filter by taking out the part where its just a tube with holes, Im going to enclose it with a can(like canned beans, that kind if can) then Iḿ going to use a spark plug for ignition, and it will be ran on propane, I got the nozzle and hose off an old grill. Iḿ going to get a gauge, and an open close nozzle to control the pressure. The axle will be A threaded Rod. But I also Need Help as far as fastening the blades into place. Should I take a Bearing and use bolts and put the bolts around the bearing? then I can just have something around the bearing which will hold the whole thing in place.(Keep In mind I will have a bearing on each side.) Because I am guessing that the air and combustion will keep the engine moving. I´ve been thinking this up the past couple of days. s how does it sound and also I am clueless on an enclosure for it.
Get back to me whenever you can and help me please!!. Then I can make an instructable on this!!!
2 replies
Flag
Also if you look at other real engines they have more than one blade, you should try it!! I am going to do that.
Flag
also, Could you put a template for the blades?
Flag
This is very impressive, I want one!
Flag
Now how awesome is that!!
Flag
I'm no expert but I have done a lot of reading on the topic (as well as in the process of building my own) and roughly 80% of thrust in an axial turbine comes from the air moving around the combustion chamber/s, in a housed jet engine. As you already know, the purpose of the combustion chambers is to take the compressed air, mix it w fuel and you are left with a force that turns the rear blades, in turn exerting the energy through the stator to start the process all over again in the front. So the front fan blades are turned at a faster and faster pace (Depending on how much fuel of course) so not only is the air compressed into the comb chambers but it is compressed around them too as it flows through the narrowing spaces between the comb chambers and the engine housing, producing around 80% of the thrust out of the rear, if all is calculated correctly. Just my two cents but I really like your project! Wish I had the resources you do! Kudos to you and keep at it, you have the makings for something great! And thank you so much for sharing your process and final piece! Inspiring!
Flag
Kurt Schreckling made one of the first model working turbojet engines using a 3 tube design very similar to this one in confguration. And it used plywood in the compressor stage housing, and a steel aerosol spray can as a turbine housing. There is a photograph of this prototype in his book -- he along with Thomas Kamps made great early contributions to model turbojet engines. So it is possible to make working jet engines, as experimental devices with very limited materials and simple designs. The point is not to necessarily to make an efficient engine in terms of performance, RPM, power etc. But to make an engine that is efficient in terms of experience, learning, and experiment. That certainly can be achieved without CAD, CNC, and Titanium necessarily. The intent here wasn't to move 100 passengers at 600 mph. But to make a modest try at spinning a rotor through self-sustaining link between a fan and a turbine. Good try, and don't get discouraged!
Flag
do you think this would work in a rocket? and how much newton thrust does the engine itself produce + how much does it weigh?
2 replies
Flag
A rocket works much differently than a jet turbine engine. I haven't measured thrust, but the thing is pretty heavy, and I don't think it would fly under any circumstances safely.
Flag
How about for a bike? Im designing a jet combustion chamber and I might use this your Instructable for the turbine of the the engine. (A turbo might work as well or better but Its cooler if you say that you built the whole thing)
Flag
About how much time did this take to assemble?
Flag
Very good work, congratulations.
1 reply
Flag
Thank you!
Flag
just as a suggestion: if you look at diagrams of get engines as they are professionally made the compression stage uses moving left handed blades and stationary right handed blades to form the compression, basically something looking like this \ / the compression occurs when the moving blade slides over the stationary blade. the stationary blade interferes with the forward moving current causing it's direction to change from moving rotationally to moving forward.
just something you might think about if you're trying to increase compression, the trick might not be to add another fan blade but might be to add a stator. also you're design is kind of funky having three different flame tubes being fed by a centrifugal fan you might decrease the tolerances by adding a stator and a sheath to keep the compressed air compressed.
2 replies
Flag
also: you can still use the rotor stator setup with your centrifugal intake if you pay attention to which way it's spinning, you want the stator to slice the air current being produced by the rotor so the stator being on the outside you'd want something like this: \(/ /)\ where the backslashes are the stator and the forward slashes are the rotor represented by the parenthesis. imagine it spinning clockwise. i would imagine if you build a manifold on the outside of the stator you'd be able to supply all three flame tubes with constant air pressure.
Flag
Thanks for the comment! I'm aware of stator veins, and the body of the engine itself is shaped in such a way that everything comes very close to being aligned perfectly as stator veins would align them. That's not to say it couldn't be improved though; in fact that's one of the thing I will be implementing in the future.
Flag
An easier shortcut would be to take automotive turbo chargers and superchargers to make your routers and stators and shroud your combustion area to make an anular combustion chamber.
Flag
I'm certainly not an engineer, but if you are really going for the centrifugal compressor, why not cut off your existing fan blades, mount radial blades on the remaining fan disk (maybe even spiral them outward) and put a cowling (a plate with a hole in it) on the front to mitigate pressure loss? I've seen electrical submersible water pumps designed in that manner (with water channeled between the motor housing and the outer housing); and squirrel cage fans work in a similar manner. I may be full of pewp, but it seems to me that maybe you could push more air into your combustion chamber that way???
1 reply
Flag
This "cowling" was made in Step 11: Finishing Pieces. I didn't use it in the test, because as air was blown into the engine at the compressor, it could be felt with the hand at the exhaust side in the appropriate places. That said it will certainly be considered for use in future testing.
Flag
Sorry, I don't have experience with jet engine. But it looks like you weld the flame tube in wrong way. If you like to compressed the air, then the wide-side of the flame tube should be at the intake fan (bigger one) and the narrow-side at the exhaust. That's I learned from the gif animation.
2 replies
Flag
Oh wait, the smaller end was intake?
Flag
The smaller end was indeed designed as the intake. During testing, the engine naturally wanted to operate the opposite direction, likely because I had no effective way to get the compressor spinning to speeds in which it would actually compress, if that makes sense. Because of the circumstances in this first round of testing, I allowed the tests to happen backwards, as they were want to do.
Flag
Should be titled " How NOT to make a jet engine"
Flag
It looks like the fins on the intake rotor are backwards. You should try flipping it around, using the jet end as the intake and the intake as the propulsion end; that way you could install a stator underneath the rear rotor, and modify the fin pitch to force air laterally into the channels. You could get some major improvements to compresion efficency that way.
1 reply
Flag
Wait, the larger end was the intake, right?
Flag
shop vac will give you the volume that u need.
Flag
May I ask what type of welding table is that with the holes? Is it a strong arm table or another commercially available one? Or is it custom?
1 reply
Flag
they are commercially available but will set u back up to several thousand or so. but u can make yr own tho. try to find a local make it space that has a plasma table. learn how to use. then make yr own table threw layering of 1/4 to 1/2 in. steel plate. then assemble your layers. and legs that will support the table top.
Flag
jknickel is right ,the speed necessary is too high for your mechanics and the air flow drive your using has to go the other way or you don't get compression . How about scaling it down , it would be safer and you can build the high precision parts easier and a dremel would work for startup . my 2 cents
Flag
As others have said, Balance. VERY important! That thing will become quickly uncontrollable and / or fly apart, if it's not balanced and starts to drive itself hard. As you know, jet engines run at a very high RPM. None of us here want to see you hurt yourself or anyone else! Nice project though. Would like to see the next revision of this after you put some more R&D time in. CAD will help you a lot!
Flag
Great to see the Ible on your "baby" I saw getting "born" this summer.
Good documenting of your learning experience and promising results!
I see some helpful comments appearing below (and more will probably follow). Apart from important safety tips, I think the "cowling" on the front compressor fan to force the air into the combustion area, is the first next thing to try.
With this kind of work I expect the better it starts to work, the more dangers will appear.
1 reply
Flag
Thanks Yvon! When I get back to testing I'll be putting everything people are saying into consideration, putting on the intake cowling that I made, and have better weather to modify things and get some better runs done.
Flag
A few tips for drilling holes in round stock. First off, use a V-block to hold the stock. This prevents it from spinning/rolling and also keeps it straight up and down.
Before you start drilling, use a punch to center mark the stock. This will keep the drill from wandering when you are first starting the hole.
With any drill size over 1/4" in diameter, drill the hole first with a smaller drill as a pilot. For a 3/8" hole, I would drill a 3/16" hole first, though the drill only really needs to by slightly bigger than the web of the larger drill.
Be sure to use the correct speed for the size drill you are using. An easy calculation is to take the cutting speed of the material you are using (measured in surface feet per minute (SFM), found in a machinist handbook or online) multiplied by 4, then divided by the diameter of the cutter you are using. This also works for speeds of end mills and other tools that spin. So a 3/8" drill in steel would be 130x4 / .375 = ~1300 RPM. Keep in mind this is just a starting point and may need to be adjusted up or down.
If you have access to one, use a lathe to drill the holes. Mount the stock in the chuck of the lathe, then put your drills in the tailstock. Don't center punch it though. Instead, use a center drill to make a dimple in the stock. Then go to your normal drills.
If you are unsure of some of the terms I used, google them and it should become apparent what I am talking about.
Properly done, you should NEVER break or burn up a drill.
1 reply
Flag
Good tip NRD, drilling thru a rod was always a pain in the neck.
Flag
Hi, you are going to kill yourself if you dont lock that nut on your fan down. Also, balancing your blades is a great idea. If you ever get it going hard it will vibrate apart. That said, enclose your fire to build more pressure for more power. Have fun and try not to die!
Flag
I like the idea of a homemade or DYI
turbine.
Very nice job so far, I'd like to point out a couple of things that may help.
After studying your design and putting some thought to it it
seems as if your igniters might be relocated out of the tubes and into a
funneling combustion chamber built around the shop vac impeller with
the igniters at the escape end.
At their present locations you are
igniting your fuel in the tubes/ fuel lines which is not allowing a
build up of pressure. Sort of like lighting a fuse inside a firecracker
with open ends or just the powder by itself or igniting gas inside the fuel injector
instead of the piston cylinder.
Having some pneumatic and hydraulic
background I've learned that a container volume under pressure is more
powerful than a tube under pressure.
Combustion in this
application needs to be a controlled, contained explosion in a partially
enclosed volume with a directed pressure escape.
Or I could be completely off base and may just need a beer:)
Flag
People have covered most of everything I had to add, but I wanted to suggest that you consider balance in your further progress. When you get one to kick off proper, you're going to want to ensure that it doesn't shell out. Balance is the key in that case. I would presume that any automotive engine rebuilder would be able to balance your shaft and turbine assembly pretty easily.
Flag
Also, as I see you noted in a further step, steel doesn't hold up particularly well under jet combustion conditions. If possible, I recommend using Aluminum and Titanium in the construction, as aluminum disperses heat well, and titanium has an extremely high melting point (both are used in commercial jet engines specifically because of these properties).
Flag
As an Aircraft Maintenance Engineer I don't really have much to add to the comments, except to emphasize Eye Protection, and the shaft was far too small for safety. In the future, you might try using 3/4" aluminum round stock, and using a die to cut the required threads. This will ensure the integrity of the shaft by minimizing stress concentrations. Something else you might consider is that a jet engine works on a pressure differential. By this I mean that once ignited it should need nothing more than a fuel source in order to run.
In aviation, jet engines are run up before igniting the fuel. I would advice caution in doing this, but you will likely have better results if you do. I recommend using a dremel, drill, or angle grinder to spin the impellers up to a minimum of 2500 rpm before igniting the fuel source. Higher is better in this case. I'm uncertain as to the viability of propane in an experiment like this, but I would also recommend priming the engine before ignition, and lighting with the modified stun gun you mentioned
Hope that helps
Flag
This will be a major rework but I think you need the exhaust outlet from the combustion chamber to be larger than the intake. For the gasses to go the correct direction the air intake has to be a higher pressure than exhaust. The exhaust is lower pressure with a much larger flow
Flag
Wow. Nice work for what I would say is a hand built turbine.
I would like to direct you to Tesla for smaller turbine designs.
The only thing I would suggest that hasnt been said already, is work out a system for centering and getting a more circular rotation.
Flag
Hi from Tübingen University,Schwaben,S. Germany...You should check-out V. SCHAUBERGER (Austria) and his VORTEX RESEARCH... Also maybe you should use PULSES ... Ciao ... Dhan Hurley
Flag
Here are comments from a retired mechanical enineer:
Just keep doing what you are doing. New engineering graduates with practical
hands-on experience are rare. Your enthusiasm and curiosity are admirable.
I am not convinced that AutoCAD skills are essential for your current projects or your future career. I now use cad, but did not in my career (hey, I started with a slide rule!).If I were now starting out, I would learn software intended to convey concepts and ideas to others, such as Adobe Creative Suite.
The impeller you are using appears to be from a Shop Vac. If so, it is likely aluminum, not stainless.Also, I measured my Shop Vac motor speed with a digital tach: 30,200 RPM!
Use eye protection and think about how your creations would disintegrate if they fly apart. Then don’t stand in the way of projectiles.