Hey Folks,

I noticed a Pulse Jet for sale on RCU and I'm curious as to how they work. I have a basic idea of how a micro-turbine works, but, the Pulse Jet looks cosmic in appearance. Can anyone tell me in a nutshell? Thanks.

Steve

I think thay make more noise than thrust... And they can make a lot of thrust!!!

The noise a pulse jet makes is mind boggling. Actually like putting a jack hammer on your head while being inside a large jet engine right besides a heavy metal concert.

Lot's of noise is the concept here

A nice explenation (and neat site) of how pulsejets work:
http://www.aardvark.co.nz/pjet/howtheywork.shtml

Steve,
Yes, they use NOISE as a drive medium!
John.

A pulse jet operates by using a metal flapper valve on the front end of the combustion chamber which opens to let air into the tube and ignites it, the combustion pressure slams the flapper valve shut and the thrust goes out the tail pipe creating a vacuum in the combustion chamber which opens the flapper valve letting in fresh air which ignites and slams the flapper valve shut,(pulses), ergo pulse jet. As everyone has said, VERY noisy and the tail pipe gets red hot.
We flew a control line pulse jet in a school yard where there was some construction going on and the jackhammer operator asked us to leave cause we were too noisy.

they are noisy my friend, but notheless still very fantastic device. basically, the poor mans jet engine. really simple. those germans used them for the flying bomb in ww2

anyway, i am sure u can reduce the noise.
how?..

add a shroud nozzle encasing the tail pipe! must extend bit further than tail pipe!
function is 2fold
1. high velocity of exaust stream will interact & pull in more air creating an overall higher mass airflow. greater thrust.
2. interaction with slower ambient air inside the secondary nozzle will "muffle the higher pitched notes! much like what happens in a turbofan (compare it to a turbojet)

oh yeah, interested in building one? found a really cool site with free plans http://home3.inet.tele.dk/kennethm/index.htm
so go check it out man