How hard could it be to make a jet engine?

[Freshgeardude]

I want to make a jet engine for fun, not to put on a bike or whatever YET, just learn how to make them.

it would be with diesel.

I know the basic design of a jet and using a leaf blower for the intake looks good, I already have one, electric.


how complicated is it to pump the fuel and keep ignition. will one spark and ignition keep it running, or does it need a constant spark running.

I want to make it so in one switch, it would regulate the increase in fuel and the leaf blower speed together, (think those light switches on walls for chandeliers)

has anyone here ever tried/ made a home made one?


I have thought of a rough design, just what I see in my head

jet engine

Edited paint job

I dont want it to be huge, something that is just simple and works. like 2-3 feet long at most.

big edit:

I just realized something. I do not want to build an actual turbine, where the exhaust would help keep the intake moving. for this project, I just want it to be simple, so I can learn where problems come and solve them an easier way that a harder way. I want to learn the simple way a jet works ( intake, compression, combustion, exhaust), and not work on the turbine.

Is it still possible, with the power of a leaf blower to still make this work? I think propane would work best, as others have suggested.

 

[MrPickins]

Be sure to get pics of the aftermath

FWIW, you might have better luck with an old turbo from a car. They managed to get one to work as a turbine engine for a little while on Junkyard Wars.

 

[Freshgeardude]

Originally posted by: MrPickins
Be sure to get pics of the aftermath

FWIW, you might have better luck with an old turbo from a car. They managed to get one to work as a turbine engine for a little while on Junkyard Wars.

I saw people used old turbos, how would it be different than a leafblower tho

 

[Blackjack200]

Originally posted by: freshgeardude

Originally posted by: MrPickins
Be sure to get pics of the aftermath

FWIW, you might have better luck with an old turbo from a car. They managed to get one to work as a turbine engine for a little while on Junkyard Wars.

I saw people used old turbos, how would it be different than a leafblower tho

I think the turbos would have much tighter mechanical tolerances. Just a guess though...

 

[The Boston Dangler]

make sure you record everything and have a family member put it on youtube.

 

[Freshgeardude]

updated OP with a picture on paint

 

[KK]

didn't someone here make one before? i remember watching the video awhile back.

 

[Eli]

Uh... lol..

A jet engine sucks it's own air in, you don't need a leaf blower to do that for you.

You do, however, need to be able to precision machine parts so that they will spin at 20,000RPM....

I recommend building a pulse jet engine first.

 

[BrunoPuntzJones]

How would diesel work for that? Could you compress it down enough to ignite?

 

[Freshgeardude]

Originally posted by: Eli
Uh... lol..

A jet engine sucks it's own air in, you don't need a leaf blower to do that for you.

You do, however, need to be able to precision machine parts so that they will spin at 20,000RPM....

I recommend building a pulse jet engine first.

I think you are thinking of the hugely complicated one, such as in real jets lol

http://science.howstuffworks.com/turbine3.htm

that is as rough of how a jet engine sucks its own air in. using some of the energy of the exaust to turn a shaft which pumps in more air.

 

[Eli]

Originally posted by: BrunoPuntzJones
How would diesel work for that? Could you compress it down enough to ignite?

Not with a leaf blower. :laugh:

Maybe with a turbo.

Text

 

[bob4432]

pulse jet ftw...

http://www.aardvark.co.nz/pjet/

 

[Freshgeardude]

Originally posted by: BrunoPuntzJones
How would diesel work for that? Could you compress it down enough to ignite?

well its just an idea, it doesnt have to be diesel, it could possibly be regular car fuel or propane.

 

[eLiu]

Uhh... I'm not 100% sure you understand how a jet engine works. Here's a nice menomic (sp): Suck, Squeeze, Bang, Blow
Unsurprisingly, your primary components are: 1) intake (suck), 2) compressor (squeeze), 3) combustor (bang), 4,5) turbine (drives the compressor), exhaust (blow)

The intake will draw the air in. This can happen many ways: e.g. forced (fan) in, drawn in b/c the engine is moving forward, drawn in b/c the compressor creates a pressure difference.
Then the compressor squeezes the air... in a commercial jet, the pressure jumps by like a factor of 50; this requires a lot of power. The high compressed (and thus HOT) air goes into the combustor, where fuel is injected. The pressure is so high that it ignites. The burning of fuel adds a lot of extra energy to the air, which then passes through the turbine. The turbine is a compressor in reverse. The air expands through the compressor, which extracts power from the expanding air to drive the turbine. Last, the air continues to expand out of the exhaust nozzle, providing thrust. (Alternatively the turbine can remove ALL useful energy and turn it into shaft-power for electricity.)

That said, building a proper compressor & turbine will be VERY hard. As Eli said, I would suggest starting with a pulse jet (explained more below).

Also, people would have used old turbos because turbos compress air. Turbos & leafblowers would not serve the same purpose in a jet engine.

A leafblower would however have a role in a pulse-jet. The pulse-jet has a lot less moving parts, which makes it a lot simpler. It operates on the same principles as what I described above. You have an intake duct that compresses air by starting with a large cross-sectional area and smoothly squeezing down to a small one. (See: Venturi) The intake pushes air straight into the combustor, which injects fuel & ignites the air-fuel mixture. Lastly, the flow will be expand out of a nozzle (really another venturi) providing thrust. The pulse-jet, lacking a compressor or fan of any type, will not start itself. The leafblower may/may not be able to push enough air into the intake to get things going... depends on how big the engine will be.

At the end of the day, proper compressor/turbine/exhaust design is -everything-. The more compression there is, the more power you can get. The better the turbine is designed, the less power you will waste driving the compressor. And the better the exhuast nozzle is designed, the more power you can extract from the flow as thrust (over-expanded, ideally expanded, under-expanded are keywords). For a small ah heck, turbine/exhaust are less important. But you WILL need compression. (Duh right? You can't just piss fuel into the air, light it on fire, and expect thrust.)

edit: use propane. Also, you'll need an atomizer for the fuel. The smaller the particles, the better.

edit2: pulse-jets will also be a lot safer. On a small engine, the compressor/turbine will be spinning at many thousands of rpm; if something fails (blade detaches, e.g.), the hunk of metal flying out will be deadly.

edit3: combustion should happen in a chamber that doesn't change much in cross-sectional area. Certainly you do not want to be expanding and combusting. Check out some interweb conceptual drawings of intakes & exhausts to see roughly how the sizing works b/c your picture has some problems

 

[Bignate603]

To answer your original question about how hard would it be to make a turbine out of a leaf blower it would be pretty much impossible.

You'd have a better shot doing it out of a turbo charger.

 

[Freshgeardude]

Originally posted by: eLiu
Uhh... I'm not 100% sure you understand how a jet engine works. Here's a nice menomic (sp): Suck, Squeeze, Bang, Blow
Unsurprisingly, your primary components are: 1) intake (suck), 2) compressor (squeeze), 3) combustor (bang), 4,5) turbine (drives the compressor), exhaust (blow)

The intake will draw the air in. This can happen many ways: e.g. forced (fan) in, drawn in b/c the engine is moving forward, drawn in b/c the compressor creates a pressure difference.
Then the compressor squeezes the air... in a commercial jet, the pressure jumps by like a factor of 50; this requires a lot of power. The high compressed (and thus HOT) air goes into the combustor, where fuel is injected. The pressure is so high that it ignites. The burning of fuel adds a lot of extra energy to the air, which then passes through the turbine. The turbine is a compressor in reverse. The air expands through the compressor, which extracts power from the expanding air to drive the turbine. Last, the air continues to expand out of the exhaust nozzle, providing thrust. (Alternatively the turbine can remove ALL useful energy and turn it into shaft-power for electricity.)

That said, building a proper compressor & turbine will be VERY hard. As Eli said, I would suggest starting with a pulse jet (explained more below).

Also, people would have used old turbos because turbos compress air. Turbos & leafblowers would not serve the same purpose in a jet engine.

A leafblower would however have a role in a pulse-jet. The pulse-jet has a lot less moving parts, which makes it a lot simpler. It operates on the same principles as what I described above. You have an intake duct that compresses air by starting with a large cross-sectional area and smoothly squeezing down to a small one. (See: Venturi) The intake pushes air straight into the combustor, which injects fuel & ignites the air-fuel mixture. Lastly, the flow will be expand out of a nozzle (really another venturi) providing thrust. The pulse-jet, lacking a compressor or fan of any type, will not start itself. The leafblower may/may not be able to push enough air into the intake to get things going... depends on how big the engine will be.

At the end of the day, proper compressor/turbine/exhaust design is -everything-. The more compression there is, the more power you can get. The better the turbine is designed, the less power you will waste driving the compressor. And the better the exhuast nozzle is designed, the more power you can extract from the flow as thrust (over-expanded, ideally expanded, under-expanded are keywords). For a small ah heck, turbine/exhaust are less important. But you WILL need compression. (Duh right? You can't just piss fuel into the air, light it on fire, and expect thrust.)

edit: use propane. Also, you'll need an atomizer for the fuel. The smaller the particles, the better.

edit2: pulse-jets will also be a lot safer. On a small engine, the compressor/turbine will be spinning at many thousands of rpm; if something fails (blade detaches, e.g.), the hunk of metal flying out will be deadly.

edit3: combustion should happen in a chamber that doesn't change much in cross-sectional area. Certainly you do not want to be expanding and combusting. Check out some interweb conceptual drawings of intakes & exhausts to see roughly how the sizing works b/c your picture has some problems

Thank you for all of that valuable info. I realized that I drew the spark outside of the compression chamber, I meant to keep it in there. If I did, what else would be a problem with that design. I understand the leafblower problem. I also will look into the pulse-jet idea

 

[91TTZ]

A little tidbit that I'd like to add is that small turbines spin at ridiculous RPM. It's not like a fan in a leaf blower that spins at a few thousand RPM, the turbine and compressor in a turbocharger (and a jet engine made from turbocharger parts) spin at over 100,000 rpm.

 

[Freshgeardude]

updated OP

 

[l0cke]

Here you go, a ramjet powered by a shop vac (on blow) and made from coffee mugs.

http://www.cottrillcyclodyne.c...ggie_Muggs/Maggie.html

 

[91TTZ]

Originally posted by: freshgeardude

I just realized something. I do not want to build an actual turbine, where the exhaust would help keep the intake moving. for this project, I just want it to be simple, so I can learn where problems come and solve them an easier way that a harder way. I want to learn the simple way a jet works ( intake, compression, combustion, exhaust), and not work on the turbine.

Is it still possible, with the power of a leaf blower to still make this work? I think propane would work best, as others have suggested.

What you're trying to make isn't a jet engine, it's a space heater.

space heater

 

[Freshgeardude]

well I looked up ramjet, it seems that it works the way I was picturing it in my mind, a quick wiki of it says that it works best around mach 3, which obviously is going to happen with a leafblower. I still like this concept, and I want to look into it

 

[Freshgeardude]

i am deciding between a ramjet or pulsejet. pulse jets look very interesting, the way they work alone is pretty amazing.

 

[eLiu]

Originally posted by: freshgeardude
well I looked up ramjet, it seems that it works the way I was picturing it in my mind, a quick wiki of it says that it works best around mach 3, which obviously is going to happen with a leafblower. I still like this concept, and I want to look into it

It works best at mach3 mostly for reasons of "free" compression. But as the "mug ramjet" link demonstrated, you can run it on much less. Just don't expect substantial thrust.

 

[spacejamz]

the real question is f you put this on treadmill, will it takeoff?

 

[Freshgeardude]

Originally posted by: spacejamz
the real question is f you put this on treadmill, will it takeoff?

yes