Homemade Jet Engine

My  Engine

I have always been fascinated with turbine engines. It is amazing that they even work when you examine the relatively few parts inside one. Connect two fans together with a shaft, stuff them in a tube and light a fire in between the fans. That’s all there is to it and they make a fantastic roar when they are running.

Diagram

This is the basic model of a jet engine. Air enters the intake and is compressed by the 1st fan in the system (the compressor). Fuel is now injected and ignited which expands causing a build up of pressure. The hot gas can not exit through the front, so its only way out is by going out the back where it hits the turbine blade. The turbine blade will spin from the hot gas rushing past it. Notice the turbine is connected to the compressor by a shaft. This shaft powers the compressor so the system is able to keep itself running as long as fuel is ignited. Initial startup requires an electric motor to turn the shaft until the engine starts on its own.


Video of the Engine Starting & running.

It is possible to build an engine like this in your own shop. Three main parts are needed.

1. A Turbo off a car

2. A combustion chamber

3. A Flame Tube

The rest of the parts are small subsystems that are needed for starting, cooling, and monitoring which are discussed later. I had to fabricate everything to fit together so a welder and cutting torch are handy to have.

The Turbine

My turbine is a Garrett GT2052 turbo off a small 4 cylinder diesel engine. This is a pretty small turbo but it will work just fine.

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Finding one should not be too difficult. Check your local junk yards or Ebay for a small turbo.

The turbo contains the compressor and the turbine stage of the engine. This works out well because it’s a self contained unit complete with bearings and the shaft. The white cloth is used to plug the oil inlet and exit until I connect the oil pressure system to them.

Combustion Chamber

The combustion chamber was the only part that I had to make from scratch. It is basically a tube inside a tube. The outer tube on my engine is 5 inch diameter. The inner tube is 4 inch diameter. Both tubes are about 12 inches long. The length and diameter do not seem to be a huge factor as long as you have some length to the chamber. I do not know how short it can be and still work.

The tube is made of exhaust pipe as well as the inside tube. I welded a homemade flange on one end so I can bolt a cover on later. The other end has a welded plate with a hole to allow air flow into the turbo.

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The inside tube also called the Flame Tube is very important. All of the compressed air from the turbo needs to pass through all the small drilled holes in this flame tube. You can see that there is a pattern to the holes.The actual flame will be inside this tube and never touches the outer combustion chamber tube. The rushing vortex of air will help keep things cool. Too many holes will cause your flame to go out so you need to really experiment with the layout. I used a free program called Jet Specs and ended up using the the hole pattern it gave me with great results.

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The turbo compressor stage needs to be connected to the combustion chamber as shown. I used plumbing fixtures and rubber plumbing gaskets as show in the picture above.

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The engine will run on propane because it is cheap and easy to use. I need a way to ignite the propane gas inside the chamber so I used a standard automotive spark plug. I drilled and tapped a hole so I could attach one as shown. In the very center of the flame tube is where the propane nozzle goes. I used a piece of 1/4 inch copper tube and smashed one end flat to help dissipate the propane evenly and the other end just connects to a 1/4 inch nipple with a compression fitting. I had to play around with different fittings at the hardware store until I got a setup that worked. The flange gets bolted together with 8 bolts and sealed with high temp red silicone gasket.

Electronics

The only circuit that is needed is something to excite the spark plug. This is needed to ignite the propane so the engine will start. A cheap and easy circuit is to use a power transistor with a 555 timer that will spark the plug when you input 12 volts.

Circuit

Ignition

The output of this circuit needs to feed into a ignition coil off a car or lawn mower. The spark plug will connect to the ignition coil.

Gages & Misc

Gages are not required but I added them to my engine to give me some feedback on what was going on. I added “boost” to measure the air pressure inside the engine. I also added a psi gage for the oil and temperature for the oil. The last gage was just a voltage meter which came with the gage set when I bought it from the automotive store. I want to add engine RPM as well but I have not built that gage yet and I doubt you will find one at a store that will read up to 100,000 RPM. The switch is to turn on the ignition coil and it can be turned off when the engine starts.

Gages

The turbo requires oil pressure for the internal bearings so I had to buy a 12v Shurflow pump that could handle hot oil and I made a small oil resivore out of a coffee can. I used 2 quarts of Synthetic Mobile 1 0w40 oil because the oil will get extremely hot. All the tubing is just 1/4 copper tube with compression fittings. I added a bypass valve so I can control the oil pressure by relieving some of it back into the can. All the copper fittings were obtained at the local hardware store. The black box is just a 12v power supply to power the pump and the ignition circuit. I have used a 12v car battery with great success as well.

Oil Pump

The engine throttle is controlled by the propane valve. I used an oxygen regulator with some fittings off of an outdoor grill to adapt it to fit the propane take.

Propane

I start the engine by using a craftsman shop vac set to “blow” mode (just switch the hoses around). I force air into the turbo’s intake to get the turbine blades spinning. I then turn the ignition on and then the propane slowly up to 50psi. I usually hear a “pop” sound and the a huge rushing of air. The turbine intake will quickly overcome the shop vac so I remove it and shut it off. I can back off on the propane to 35psi once it starts and it will idle nicely.

Engine

The engine sounds fantastic and is extremely loud. I have to wear earplugs when I am around it.

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