Pulse jets are very interesting jets. They were used to power the german V-1 during WW2. They, like other jets, use Sir Issac Newton's third law of motion which states, for every action there is an equal and opposite reaction. What this means is that the burnt fuel/air leaving the back of the jet is the action and thrust is the reaction. They are used on control-line planes and can reach very high speeds. Models pulse jets can reach 120 decibels, there is the same noise level if you stand 3 feet from a model pulse jets as if you stand 50metres from a full size turbine jet. I have made a brauner jet throughout the year and have eventually started it. Once i pressure feed it, got some Propylene Oxide and a better pump. This is the method i used. I used a spark in a long tube which i put up the tailpipe. The metering jet hole size was 1.5mm. To start it i pumped about 4 time and flicked the on switch. When i did this i got a loud pop and a flame out the back. I then realised i should try flicking the switch on the down pump as this might help it to re-ignite. When i did this i got a pop and a sucking noise. After a few attempts i started getting very short runs. And eventually i got a sustained run, for about 6 seconds until the fuel ran out. Soon i will put some photos up and also some noises of the different things i have described above.
 
 

The air enters the front of the jet and as it passes the fuel pipe it sucks some fuel up with it. It then procedes to the flutter valve where the air forces it (the valve) open, the air/fuel mixture then goes into the combustion chamber where it is ignited by a spark plug. The force of the explosion forces the valve closed and then the low pressure caused by the burnt fuel escaping down the tail pipe opens the valve and sucks more fuel through, this process happens about 200 - 250 times per second.

On the bench and ready to be started!!!