The looped tube is A valvless jet and the straight through is A valves --if u want 2 know what The valve is for as me =) FPS australia -- look up on utube =)

Pulse jets for a project report ,great idea

The looped design has a serious flaw in concept, though, and that is Isaac Newton...For every action there is an equal and opposite reaction. When the jet engine draws air in from the back, it pushes the car in the opposite direction, you can thank the conservation of momentum for that. And if the engine is drawing air in from the back, it will create a force pushing the car backwards. Now, granted, the release of energy from the fuel burning being propelled backward and pushing the car forward will overcome the "backward" force, but now the jet has to overcome that force. It would be far more efficient to have the air in-take in the front of the car instead of the back. This way, the jet force and the in-take forces are added together, not subtracted.

This is assuming that the pulse-jet draws in air from the front and expels it out of the back, similar to a jet engine. A pulse-jet uses cycles. It draws in air with fuel mixture, then detonates that mixture to form an explosion. The explosion moves equally out of the intake and exhaust. In a valved pulse-jet, the intake has a set of valves on it to contain this force and send it only out of the exhaust. In a valveless pulse-jet (As the U-shaped type is), there are no such valves (no moving parts at all, in fact). Instead, both the intake and the exhaust are pointed backwards to achieve a net greater thrust from the explosive exhaust cycle. While it is slightly less efficient to point the intake away form the airstream, it makes up for it's lack of intake air with a much greater thrust.

So, in summary, you light off an explosion in a can with two holes. If both holes are pointing the same direction, you get more thrust. After the explosion, both holes act as an intake (one hole has a shorter tube, allowing it to be the primary intake). Then the explosion is ignited again, and the process repeats. There is no continuous flow of air through the engine as there is in a Turbojet or a Ramjet.

Hope that cleared some things up,

-Bob

ur right, but simply using a can with two holes will only produce a few pulses because,to cause significant decrease in pressure during the intake phase u need to utilize the full momentum of the exhaust gases but using two holes simply means not all the gases expand inside the can and significant amount of the fuel burn outside

If you build using those plan, you wont get the pulsing action. The pulsing is created by the U-Shaped. This is because when the fuel ignites the hot gases come out of the intake and the exhaust, and then gas is sucked back in through the intake and the exhaust. Because the intake is shorter, Oxygen will be sucked through the intake, but because the exhaust is longer some of the hot gases from the previous pulse is sucked back in through the exhaust, and it is this gas that ignites the fuel for the next pulse.

u dont need the u-shape to cause the pulsating action.As far as a pulse jet engine is concerned even a straight tube with the intake at the front and the exhaust at the back will produce pulsating action except that it may only produce minimal thrust

This explanation of the pulsing cycle of the pulse-jet engine is correct, but it has one flaw. This type of action does not require any kind of U-shape to happen. Only one chamber with a long tube and a short tube, which this design is.

This design is basically one of the U-shaped designs, unbent for ease of construction.

-Bob

Post Scriptum: See http://www.pulse-jets.com/ for a better explanation than I am able to give.

the intake doenst create that much force? and i think the disign itself creates a better thrust because the thrust after the exposion is more than the vacoum and with the intake in front since its valveless, it leaks so even though most of the force go bakcwards, some goes fowarnd, much more than if you were to have a u design

it creates as much force as u want it to

if you coil a heat resistant fuel line or a metal fuel line a few coils around the exhaust and then into the combustion chamber, you can vaporize your liquid fuel before it is in the chamber. you will need a fuel pump to keep it flowing, and some experimenting to get the number of coiled right. most have between 4 to 6 coils.

Who knows if you're still interested or already found a solution, but if you haven't, what you are looking for is a heat exchanger. Can be as simple as wrapping your fuel lines around the very hot nozzle, vaporizing your fuel. Obviously this MUST be done with metal lines. This is very dangerous if done incorrectly however.

Surely that requires the engine to be running first? might be wrong but seems logical that there wouldnt be any heat otherwise...unless of course u start it with gas first.

Do you still have a copy of your plans? If so I would like a copy. Thanks JonL.

would love a set if you still have them mate.

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Sure--send me a copy. I'm the engineering teacher at a local high school and we are always looking for new plans. brian.smith@rsd.edu Thanks

thanks

And, hey...can you buy the parts at the local hardware store/menards...or must they be ordered?