Hey guys, did you notice the difference in flame and shear volume of the engine in comparison to the night run? Interesting yes?
This is basically completely due to the ignition source being placed at the front of the engine instead of toward the rear.
The vid on the bottom right had the fuel stinger in the position i'm going to stick with... so the question is whats next?
Should I remove the second baffle, or cut back the exhaust nozzle first, what would you guys like to see?
I wish I could test the thrust output to compare before cutting it though!
My write up thus far:
The basic idea...
We start off with a scratch build of a ramjet... completely different to most standard ramjet designs out there. A flame holder I haven't as yet seen been used... heck lets just throw in a second one for experimental sake. And while we are at it, we will keep the tail cone long with a small exit nozzle. The idea being, that as I progress through each stage of the ramjet, I will document via video all the changes made, and record them as I go along, taking submissions from forum members as to what they think might be a prudent next step and seeing exactly how small changes might effect particular parts of ramjet performance.
In its original state, the stinger is plugged at the end of 6mm copper pipe, with 4 angled holes toward the FH. Its placement is about 1cm foward of the FH. A sparkler was inserted into the back of tailpipe, and the gas initiated. We had flame stabilisation, though it wasn't very big, nor very loud. When looking into the front of the engine, we could not see the flame reaching the 1st or primary flame holder (PFH)
Night run. Still in the same state, but it would be easier to see the heat patterns on the engine and help us understand whats going on inside. We noticed the majority of heat in the engine was confined to the area behind the second baffle and the exit nozzle. We noticed that the flame was again not stabilising behind the primary flame holder. There was only a small blue flame and it was surrounded by a rich orange colour, we also noticed large blue pops and bangs. It was decided that firstly, we would change the fuel stinger as those traces of blue flame popping out of the inlet might have been due to the engine trying to stabilise the flame at the PFH as I was slowly turning up the gas to keep the pressure high. I notice it also chewed about half of a 4kg within about 10 minutes... which leads me to believe my stinger probably isn't as high pressure as it should be.
We changed the fuel stinger, and where it was placed in regards to the flameholder. It was moved foward approximately 1 inch, with now only 2 holes instead of 4. This time, however i did something completely different...I inserted the sparkler in the front of the engine, so it would burn TOWARDS the PFH and the stinger. Immediately I noticed a problem. The burning gasses passed the PFH and started coming out the inlet, and started to burn my nozzle. I believe that there are 2 reasons for this,
there is alot of pressure at the exit cone, meaning that an increase in pressure from the expanding gasses would not be presented with a large enough exit nozzle for it all to pass out, hence coming out the inlet.
I think this is an important point for all ramjet design.
The fuel stinger was too far foward.
I believe this might have been moderately successful. I managed to achieve sustained flame stabilisation behind the flameholder. I could throttle it quite well too. It was extremely loud in comparison to all previous tests and there was a clear and evident blue flame exiting the exhaust nozzle. This was with the original fuel stinger too, I believe in this case the ignition point was the critical factor, and the stinger location is working for the engine IN ITS CURRENT STATE ONLY. At this point, I am not sure, but am assessing the possibilty, that a higher amount of thrust at low airspeed could possibly be generated by having the smaller exit nozzle, as most of if not all of the air that was entering the inlet nozzle was being combusted and exiting the exit nozzle.
Is this write up ok? I really want to feel like I'm contributing something, so if others who come here, and try to build a ramjet, they might see particular things going on their ramjets that possibly might have been seen before in my experiments. You know, just want to feel i'm doing my part as I'm still kind of a noob and all, I want to take some time to try and give something back. (you guys have really been helpful and patient, figured I'd atleast TRY to do something helpful)
As listed above the video's of the runs are here, the 4th run was most promising if you haven't seen it yet, it was conducted this afternoon.