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dannym3141 says...

>> ^GeeSussFreeK:
>> ^potchi79:
So you start a pulse jet with a leaf blower?

Mostly yes, the idea behind most jets is to compress incoming air with fuel. No spark is needed as the compression causes heat. The problem is you need the air already moving to start. The same is true of turbofan engines of most jet airplanes. In my day they used electric motors to start the fan blade spinning. Once they are up to speed, they feed enough air fast enough into the combustion chambers to keep it going. A leave blower is a lot easier to add to a project then an electric motor. If you look up DIY jet engines in youtube, you will see it as the staple for home brew jet starters.
Jets are much more "simple" then combustion engines as they are mainly self sustaining when up to speed. They are very complex in other ways though, like how to not melt down under extreme heat and such. A flame out at low speed typically spells doom for a jet...engine restarts when careening downward is not as experience you want in life.
One thing I have never understood about a pulse jet is how to ramp your speed up. With a turbofan, you just up the fan speed or fan blade pitch...with a pulse just I have no idea. Add more fuel maybe? If that were the case, then the max speed would be dictated by the explosion maximum. If your explosion is to great, you risk vibration annihilation or destruction of your combustion chamber...or you spit the hot air out the back end before the pulse can bring it back for re-ignition? Or perhaps it has to do with pulse modulation and changing how long you wait till your open the valve. The longer you wait, the more thrust you get before the next cycle? Dunno, pulse jets were always more of a curiosity than an area of study.
Edit: Jets are very similar to diesel engine as there is no spark needed...all the heat is gained through compression. Hope that isn't TMI at this point


than

Though your knowledge of jets is impressive. Let's really try to stomp this sign of the internet generation out, shall we?! Who's with me!?

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GeeSussFreeK says...

>> ^potchi79:
So you start a pulse jet with a leaf blower?


Mostly yes, the idea behind most jets is to compress incoming air with fuel. No spark is needed as the compression causes heat. The problem is you need the air already moving to start. The same is true of turbofan engines of most jet airplanes. In my day they used electric motors to start the fan blade spinning. Once they are up to speed, they feed enough air fast enough into the combustion chambers to keep it going. A leave blower is a lot easier to add to a project then an electric motor. If you look up DIY jet engines in youtube, you will see it as the staple for home brew jet starters.

Jets are much more "simple" than combustion engines as they are mainly self sustaining when up to speed. They are very complex in other ways though, like how to not melt down under extreme heat and such. A flame out at low speed typically spells doom for a jet...engine restarts when careening downward is not as experience you want in life.

One thing I have never understood about a pulse jet is how to ramp your speed up. With a turbofan, you just up the fan speed or fan blade pitch...with a pulse jet I have no idea. Add more fuel maybe? If that were the case, then the max speed would be dictated by the explosion maximum. If your explosion is to great, you risk vibration annihilation or destruction of your combustion chamber...or you spit the hot air out the back end before the pulse can bring it back for re-ignition? Or perhaps it has to do with pulse modulation and changing how long you wait till your open the valve. The longer you wait, the more thrust you get before the next cycle? Dunno, pulse jets were always more of a curiosity than an area of study.

Edit: Jets are very similar to diesel engine as there is no spark needed...all the heat is gained through compression. Hope that isn't TMI at this point

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