More Pulse Jet Questions

[rockooby]

So I was able to get my pulsejet to run and idle. All I did different was to move the fuel injector from right before the combustion chamber on the inlet pipe to at the very beginning of the combustion chamber after the inlet side cone (I'll include a picture as this description is not the best.) I just screwed in a pipe plug into my old injector hole by the way. So now the issue I face is I can throttle down the pulse jet a little bit but I can't really throttle it up. A narrow throttle control band I guess you could say. As in the video of the pulse jet running that was the max throttle I could achieve, opening the needle valve anymore to let more gas flow would see the pulse jet go out. Also Maybe my cart is not the best but it should be able to roll reasonably well. Though it was not chalked when I tested pulsejet, I saw no movement of the cart. So there has to be more performance in this jet I feel. I failed to take any pictures of my new longer injector I made to better fit the larger diameter span of the new combustion chamber injector position. Though it is still just a tube with holes which has a combined area of holes that add to about 50mm^2. I am looking for more performance and greater throttle range any suggestions on how to achieve either are very welcome. Also anymore details I forgot to add I'll be happy to divulge in a reply. Also what are some good ways of measuring thrust? I was thinking of pulling a known mass against gravity. Or pulling up a brake rotor or two on a bathroom scale and finding the difference between the initial and final forces applied to the scale. Or if there is a good spring gauge I could order or find pretty regularly I'd be happy to hear it.

[racket]

Could you please explain a bit more about the engine stopping when you increase fueling .

[rockooby]

(Could you please explain a bit more about the engine stopping when you increase fueling)-

So in my testing I was able to start the pulse jet by blowing air into the inlet and adjusting the fuel flow rate accordingly to start the pulsing of the pulse jet. Then I would let the pulsejet run for a minute or two without adjusting the fuel flow rate from when I initially started it (this is when I captured my videos.) Then after putting down my phone I went over to the needle valve that meters the propane flow to the engine and barely increased the flow and the pulsejet went out.

A bit of background on my fuel system also. The fuel comes out of the propane tank (an American propane tank[if that helps]) through a screw on connector with an orifice diameter of 3mm. Then it goes through a 1/4 inch npt pipe fitting which is attached to a soft propane line so I can better position the propane tank. It then goes through a 1/4inch T-fitting, which on top of the T-fitting I have attached a pressure gauge. Then the line is adapted from the 1/4npt to the 3/4 npt required to fit the needle valve. The needle valve is a "Summit LFC-08N". Every part of my fuel system before needle valve I call the high side of the fuel system referring to the pressure. The low side is everything past the needle valve in the fuel flow path to the pulsejet. This is where I adapt my fuel line, through use of flare fittings to a 3/8 hard steel fuel line. This then continues to the pulse jet's fuel injector, where the hardline is connected to the injector through a flare fitting so I can disconnect the fuel line easily from the injector. The injector consists on two brass adapters to adapt flare fitting to the steel 1/2 inch pipe fitting which I welded another piece of 3/8 hard fuel line to and then welded a 3/4 pipe fitting over to make the injector. This injector spans about 265mm end to end. The actual perforated part of the injector tube for fuel to enter the pulse jet spans about 140 mm, with each hole being about 1mm down from the previous hole which is arranged to be drilled 180 degrees from the previous hole on the other side of the injector. There are 13 holes in total with a diameter of 1.98 mm (5/64 of an inch.) Which adds up to be a combined injector hole area of about 40mm^2, not 50mm^2 as I said in the original post. I just forgot my dimensions when I typed that out. Though I know I chose the 40mm^2 area in an attempt to have a greater injector spray and hopefully have better mixing as a result in the pulsejet. Though if 50mm^2 performs better I don't know. 

I copied Build Comics injector design and adapted the dimensions to fit mine-


Here is a picture of my injector -






Needle Valve page-

summit-hydraulics.com/product/hydraulic-flow-control-valve-w-free-bi-directional-flow-1-2%E2%80%B3-npt-ports-2/?srsltid=AfmBOoqM_BOIktHudC8PspRgjEMTCAzQ1ZCgs4lucsAdpB61ZuK7FepW

[racket]

I've heard that some American propane tanks have " safety" devices fitted that limit the flow rate , perhaps you might check that first , it might be cutting off the flow once you exceed the rating