Valveless Pulsejet Engine

140 decibels. 1400 degrees Farenheight. 2.5 pounds of thrust. This is how a teenager made a fully functioning pulsejet for a school project. I was always fascinated with jet engines, and I made multiple model jet engines out of tin cans. Unfortunately, tin cans cannot withstand the heat generated by conventional jet engines. So I designed a Pulsejet engine with the help of pulsejets.com, and worked with my friend at a local Makerspace to bring my idea to life.

1.) A steel bottle that looks like an Ernleymmer flask/ or some steel sheet metal, and a sheet metal roller

2.) A welder, grinder, and something to cut steel sheet metal and steel pipe with, or just go to a local Makerspace.

3.) A bunch of steel pipe that matches the ratio of the Erlenmeyer steel bottle flask and a metal straw.

4.) Safety equipment and testing rig, which is propane with a valve, pipe, and steel straw.

First of all, we need to find a suitable bottle for the project. It needs to be cone-shaped, and it has to be made of steel. An easy way to test if it is steel is to use a simple magnet. If it attracts, it is likely steel, and if it doesn't, it is a different metal. If you want don't want to follow my exact dimensions, feel free to scale them appropriately. (The ratio must stay the same)

The bottle must be:

Height: 150mm

Width: Approx 1mm

Small Diameter of the cap: 40mm

Large Diameter of the bottom: 60mm

If you are unable to find this bottle, go get sheet metal with a thickness of: , and bend/cut/weld it to size.

You must have these sizes of pipe

Big pipe

Length: 387.35mm

Width: Approx 1mm

Diameter:32mm

Small Pipe (You need two Pieces which can be cut from a longer slab of pipe)

Length: buy 100mm, but you need to cut it into 2, 50mm lengths

Width: approx 1mm

Diameter: 20mm

Before we build the valveless Pulsejet, we must understand how it works. For the model that I am making, there is one intake facing backward and 1 exhaust. There are two main species of pulsejets, one that is valved and one that isn't. The valved type requires a reed valve that oscillates to create a one-way seal. Once the fuel and the air are inside the Pulsejet, they are ignited and sent out through the exhaust to create thrust. Valveless Pulsejets, which are the ones we are making, have no valves and instead use pure geometry and thermodynamics to run. There is a backward-facing intake that sucks in air, and once inside the combustion chamber ignites with the fuel, and the hot gases go out of the exhaust, creating a vacuum that pulls more air in through the intake. This cycle is repeated about 45 to 250 times per second! Both of these systems get very hot, and because of the constant vibration/oscillation/combustion, there is a lot of noise.

If you really don't feel like welding, there is an excellent Integza video detailing how to make a similar pulsejet using carbon fibre and furnace/chimney cement. However, if you already have a welder or live near a makerspace with one, then you can weld the pipe to the lip of the bottle. Then you get your grinder and cut a small oval shape on the bottle on the side and weld a small 50 mm piece of pipe in at about a 45 degree angle. Then get the same smaller pipe and cut a hole in it for another small pipe to join. Again, cut another 50mm piece of pipe at a 45 degree angle, and weld the 2 smaller pipes in. The last small pipe should be about horizontal with the large pipe. After you are all done welding, it is recommended that you build a testing rig to attach the pulsejet to so you can run it safely.

Now it is time to steal a propane tank from your barbecue. You most likely need a one-way regulator valve, so you can adjust the amount of propane going into the pulsejet. Then, to start it up, you first should watch a video by Colinfurze, and get a blower and a lighter or blowtorch. First, you need to add a little bit of propane and light it through the inlet tube. Then, once you have a little fire inside the combustion chamber, use a blower at the inlet to let the exhaust exit and the first pulse begin. While you are doing this, exercise extreme caution because the Pulsejet will be extremely hot.

I am not responsible for any injuries in this process.

THE NEIGHBORS WILL GET ANGRY, SO BE SURE TO TELL THEM FIRST THAT YOUR PULSEJET WILL MAKE A LOT OF NOISE.