I wonder how well a direct tap into the side of the combustion chamber would work with a little flap valve? There is that Russian book that has an illustration of something along those lines. You can arrange for the tap to create pressure or draw a vacuum depending on which way the reed is positioned. Maybe a fuel line with the ability to draw in a slight bit of air, like the intake venturi on a Dynajet, only 95% smaller would work, have the valved fuel line offset/channeled a bit so as not to be exposed to the heat of the chamber so much. The tiny fuel/air port would not really affect the workings of the valveless I should think. I once put a "Sibley" reed valve in the front of my Logan and left the side port as is and it reved up just as peppy as without the reed, sort of a hybrid. But what I am describing would be something with a much smaller signature, just a fuel line that works by tapping the vacuum phase of the engine.
Another time I used an expensive, tiny store-bought reed, not much larger than a few BBs, that sleeved inside some silicone fuel tubing to tap the pressure off the front end of my little Logan. I had one of those brass fittings screwed into the head of the Logan and nippled off to the silicone line which fed into an air tight fuel tank. The tank recieved pressure from the silicone line and drove the fuel into the side port of the Logan. But what happened was a non-linear effect. The pressure kept increasing and the engine would flood and after it stopped the fuel kept spraying for a bit, sort of a fluidic capacitor effect. ha
Lastly, we can recall a few examples of a valveless drawing liquid fuel without the aid of pressure; however I think, as with my Logan experiments, that it is tricky to do so without some of the fuel getting spewed out of the intake, wasted because it is not delivered properly to the pulsejet. And instead of pressurizing an entire tank, I would like to think there is some way to grab a portion of the fuel line and pressurize/partition only that segment of the system so as not to reinvent the propane tank. Wouldn't it be neat to make a little fuel pump that ran on the heat of the engine?http://blog.modernmechanix.com/2006/04/ ... pulse-jet/http://www.elderrubber.com/duckbill-valves.htm