New ramjet experiments

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Irvine.J
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re: New ramjet experiments

Post by Irvine.J » Fri Dec 01, 2006 1:18 am

well, first, I think having a fuel tank as a counterballance would be a very bad idea... As fuel is used, well, that side gets lighter and... you get the point. Having the tank in the middle wouldn't be too bad, but, would the gas not be pulled out to the ramjet as it gets going faster?
Hehe yeah remember how I said "Flying" and "Bomb" :D

I have an huge electric motor that I salvaged from an industrial washing machine that would have the power to get it up to speed for sure,(Though I might need to gear it abit but i doubt it.) and plenty of rc controls.

I like the idea of leaving the disc brake on so one can just pull it to shut the motor down, nice touch :D.

Larry thanks for your comment I'm glad i'm on the right track. For now I might just put this aside, though I'm pretty keen to be able to properly test the maximum speeds and thrust of Pjs, ramjet, etc engines... i'm a "jet addict" now for sure. Anyway I'll turn the motor around and run it backwards for you Simon as I got my brothers camera today, should be interesting, I'll also run it the original way, and just dump massive amounts of gas in there and see if i can get the flame to crawl back up.
REMEMBER I've got an engine, that i decided to run when in a totally wierd config... and I'm going to run it each time I modify it and record the effects of the modification here.

Thanks for your help guys. Best wishes and merry christmas to you all.
#47.
I want to change my forum name now to ... simply to JIrvine or Irvs or something. How would one do that?

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re: New ramjet experiments

Post by Zippiot » Fri Dec 01, 2006 4:15 am

Something just isn't right...

It should be much louder, loud enough for the police to make a visit...

Maybe not enough air, but the spinning setup would fix that. Just watched the videos again thats why I bring it up.

Glad people are finally building little rams.
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re: New ramjet experiments

Post by Irvine.J » Fri Dec 01, 2006 10:23 am

GREAT SCOTT!!!!
They might say.

My next 2 videos.

In video 1... (bottom left.)

In the first one, the fuel stinger was moved to 1 inch closer to the inlet and away from the PFH. This time however, i stuck the sparkler in the front instead of the back... with a slightly higher pressure stinger.

I now realise just how important the placement of your ignition source is, not only did the flame breach the SFH (Secondary flame holder) it breached the primary too!!! I had to shut it down after a short run in fear of burning my blower nozzle. There is a video of this and but i thought hmmm.... i'm getting closer...

In video two... (bottom right) Successful-ish?
Fuel stinger returned to postition just a fraction infront of the flameholder.

I'd say this was successful as far as a physically not to spec ramjet would be escpecially at lower airspeeds. The flame was now sitting right behind the flameholder... it was INSANELY LOUD, and im not kidding!! Louder then i've ever heard it.
Its amazing how a few small changes like ignition point and 1 inch on the stinger can do. It had a whopping blue flame too, that becomes visable as soon as the sparkler is burnt away. You can see the metal wind break being moved by the exhaust thrust. Anyway for what it is, with a smaller then prescribed exhaust cone, its really something. Im not sure what effect cutting back the exhaust or removing the baffle will have, but I can't wait to find out!!! Zippiot your right, it should have been darn loud... and now it seems it is! Or atleast getting there... My neighbours must hate me!
Enjoy.

http://mangyjet.freewebpage.org/rj.html

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re: New ramjet experiments

Post by Irvine.J » Fri Dec 01, 2006 4:29 pm

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.

Run 1-
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)

Run 2-
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.

Run 3.
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,

Firstly,
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.

Secondly,
The fuel stinger was too far foward.

Run 4-
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)
Thanks guys.
James.

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.
http://mangyjet.freewebpage.org/rj.html

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re: New ramjet experiments

Post by Zippiot » Fri Dec 01, 2006 7:30 pm

Thats the noise I'm talking about!!!

Notice how in runs 3 and 4 you cant even hear the blower? Good stuff congrats


Im not so sure about run 4...seems combustion left the ramjet a few times (running rich) but the blue indicates a proper propane mixture...I am stumped...


If you run out of sparklers a rag soaked in kerosine (gasoline diesel whatever) shoved upt he tailpipe works. Problem is retrieving it before the flaming rag gets too far away.
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Re: re: New ramjet experiments

Post by fuelburner » Fri Dec 01, 2006 9:27 pm

hi,I was impressed when I saw your idea of having a ram jet on a axle,been thinking the very same after seeing the helicopter with the tip jets on it.

I was hoping to make the same thing as you ,but to have the axle flat rather than pointing upwards ,the main reason is that if it should disassemble itself there would be a relative safe plane to avoid.

also I would use a piece of thick seamless hydraulic tube as a axle with the arms attached to this,the fuel would be pumped into the tube from one end ,perhaps at a couple of psi. there is a way around the seal problem to a degree,if the end of the tube has a step in it,the fuel will be forced against the tube wall and not dribble out of the end were the fuel comes in,of course this is a very vague solution as you would also have air forced in with the fuel as the 2 arms started to rotate and create suction.
also ,if the two arms are the same (tubes) the fuel would fill the other counterbalanced one ,and avoid out of balance problems. (the residual air in the other arm will be squashed by the fuel)

this would simply mean using a relatively loose ptfe washer to seal the fuel line into the tube to prevent this,the fuel would travel up a small dia steel tube inside the main arm,or just use the arm as the fuel pipe. a oil burner nozzle would be fitted into the end which can be changed to suit the fuel requirements to a degree. as they do not flow double the flow for double the pressure ,so is self regulating and a small increase or decrease of fuel pressure to the main shaft might provide enough of a throttle.

the fuel would be injected across the back face of the diffuser,this would avoid the problem of the fuel been centrifuged to one side,this would rely on this effect as the full amount of air would see the fuel as it travelled through the atomised fuel. this will work as I have experience of diy gas turbines and this is how I injected the fuel in my first afterburner,I.e. across the very fast stream of gas. also it works at very low and high fuel pressures ,but in this case fuel pressure will not be wanting !!!!

so I think your idea is a goer ,and hope to do the same in the future when I finish other related fuel burning projects :-)

regards jon
Number47 wrote:Hmm, so i scratched my head and low and behold I'd been gazing at a spare tire for about 20 minutes + or - ...




Then it hit me, what about a car axle?! EUREKA! as us auzzies would say.
A car axle generally could handle 200mph for atleast a short time. If exceedingly well oiled, and completely cut away to remove almost all of the unecissary metal and tyre etc just leaving the "hub", much like cutting of the rear axle of an old car that was front wheel drive. Even so, you could cut either axle, as the hole left for the diff could be used to run the fuel up it. You could cut the axle to about 1/2 a foot, and weld it to a large base plate and anchor it to the ground...with the hub now in the correct position you could simply attach the "swing arm" if its well oiled and completely free it should spin with very little resistance, be solid as a rock too.

This would allow me to keep the propane tank well away also.
If you think this might just do the trick, I might start thinking about an appropriate gas system that can handle the turning motion. An rpm meter from your standard car should be sufficient (though i can easily aquire an electronic one) to work out what speed its travelling at a certain throttle setting, as Simon so nicely pointed out, RPM would be directly related to the speed the engine was travelling.
I believe this might be the answer, what do you guys think?

Najm wrote:
Are you providing it with fuel after the primary flameholder?
Try aspirating your ramjet, you are currently injecting fuel into it if I'm not much mistaken.
Also the ramjet's diffuser is not slowing the air down as much as it should, try using a higher ratio of intake area to combustion chamber area to slow down the air.
Maybe the rate of combustion is not faster than air velocity?
And in the night run video what are the blue flashes at the intake?
BTW How do the pulse-jet poeple measure their pulse-jet's thrust??
Hi najm, well the fuel stinger is slightly infront of the primary flameholder, and yes your correct its lpg under moderate pressure. (my holes are a little large then i would like as i broke my really fine drillbit by not paying attention.) I think the PFH (primary flame holder) should be slowing the air down enough, it might just be the small nozzle basically creates a pressure zone at the rear where the incoming air wont allow it any further foward? What do you think? The blue flashes I THINK are caused because I was running out of gas and might have been loosing pressure. I had to slowly keep increasing the gas as it had died once or twice... which basically meant that it was coming in and out of life... WAIT A MINUTE!!!

I noticed when starting the second ramjet I made, that big blue flash meant it was BOOMING into life, however there is also the possibility the gas was starting to combust in the primary or "intended" combustion zone at the primary flameholder, but I wasn't supplying enough gas to contine it combusting up there... your question just made me think of that... What do you think??? If this was true I can only IMAGINE the amount of volume/speed that exhaust would be coming out the back... I HOPE SO... but I bet one of the physicists will tell me its not going to happen :(

I really didn't think of that blue flame in regards to what a ramjet looks like when it starts...I will FOR SURE be running it again with a full tank and try and get that same effect and the combustion up there next to PFH.
Thanks for the question I hadn't thought of that, you the man! Way to go!

How do you measure its thrust??? I'm working on it! Lol!

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re: New ramjet experiments

Post by thecheat » Fri Dec 01, 2006 9:34 pm

Well, atleast this time I could see everything but the videos on the page...

Anyways, 47, is there any way you could send me the videos? I can't view youtube stuff, which I suspect is the reason I can't view the videos... try PMing them to me, if that won't work, I can PM you my email address.

hope something works out for you!
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re: New ramjet experiments

Post by Irvine.J » Sat Dec 02, 2006 2:48 am

Thankyou Zippiot, fuelburner and the cheat for your responses. (I'm working on getting you the video's right now)

Zippiot as you say it did seem on occasion if the blower moved slightly away from the nozzle for a split second that huge blue flame tounge would leap out. While I was looking into the engine, it seemed like I was battling to keep the flame behind the flameholder as I stepped up the gas.
I'm of the opinion right now that the flameholder isn't quite the right ratio, perhaps the second baffle is generating a little too much pressure escpecially when added to the smaller noze cone.
I don't know what I want to do next... remove the baffle or cut the tail cone...any ideas??? Glad you like Zippiot, its amazing that its atleast functioning somewhat correctly in this modified state.

Fuelburner (jon) thanks for your response and I feel privelaged to be your #1 post :D Its an interesting idea for sure, both rotor orientations I can see have pro's and con's, for example the rotor you suggest might act as a trebuchet in the unfortunate event of critical failure, but would be like you say easier to avoid the projectile.
I see you have a good understanding of hydrolics and related parts, and look forward to your future posts, :D Perhaps a quick sketch as to how the gas line up the centre would fit into the rotating part so the gas line doesn't wind up on itself and still keeps the seal on the rotating arm? Thanks for the reply I appreciate it, your knowledge on gas turbines would be much appreciated here.

The cheat I pm'd u :D

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Woohoo! I'm now Irvine J

Post by Irvine.J » Sat Dec 02, 2006 4:34 am

Just thought I'd let you know :D Thx mike everything worked perfectly, way to go :D

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re: New ramjet experiments

Post by Mike Everman » Sat Dec 02, 2006 4:46 am

My pleasure, James.
Mike
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re: New ramjet experiments

Post by Najm » Sat Dec 02, 2006 10:00 am

I don't know what I want to do next... remove the baffle or cut the tail cone...any ideas???
Increase the dimeter of the tail cone, the secondary flame holder might have been helping in combustion( slowing down the gases).
It's just an idea, up to you to do what you want to do.

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re: New ramjet experiments

Post by Najm » Sat Dec 02, 2006 10:01 am

Sorry , double post.
The page wasn't loading.
Last edited by Najm on Sun Dec 03, 2006 6:22 am, edited 1 time in total.

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re: New ramjet experiments

Post by thecheat » Sat Dec 02, 2006 8:51 pm

it took me a second to figure out it was you 47... (I'll call you the new name soon, I'll remember it after about seeing it the hundredth time...)

checking out the PM... (check your PM's)

Hope my jet works... I just finished welding it and the fuel line... haven't figured if I'll put a sparkplug in it or not...
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Re: re: New ramjet experiments

Post by fuelburner » Sat Dec 02, 2006 11:16 pm

hi ,thanks for the reply :lol: on the seal side a quick a dirty solution to the problem could be solved by getting a relatively cheap air tool swivel joint. simply have a normal hose end on the axle with a short piece of hose ,then have the swivel joint on this. the short piece of hose would help if the hose end on the axle was not 100% central. these handle 10 bar of pressure and if you spray a bit of oil onto it ,this should be enough to get you up and running quickly with this idea.

been thinking about the counter weight on the other side ,this may not be a good idea having it the same length ,since it is undriven ,at the higher speeds you may get deflection and this would put the balance out of the window big time ,perhaps taking a idea from nasa's centrifuge and have a mass close to the centreline to create the required balance weight ???

regards jon
Irvine.J wrote:Thankyou Zippiot, fuelburner and the cheat for your responses. (I'm working on getting you the video's right now)

Zippiot as you say it did seem on occasion if the blower moved slightly away from the nozzle for a split second that huge blue flame tounge would leap out. While I was looking into the engine, it seemed like I was battling to keep the flame behind the flameholder as I stepped up the gas.
I'm of the opinion right now that the flameholder isn't quite the right ratio, perhaps the second baffle is generating a little too much pressure escpecially when added to the smaller noze cone.
I don't know what I want to do next... remove the baffle or cut the tail cone...any ideas??? Glad you like Zippiot, its amazing that its atleast functioning somewhat correctly in this modified state.

Fuelburner (jon) thanks for your response and I feel privelaged to be your #1 post :D Its an interesting idea for sure, both rotor orientations I can see have pro's and con's, for example the rotor you suggest might act as a trebuchet in the unfortunate event of critical failure, but would be like you say easier to avoid the projectile.
I see you have a good understanding of hydrolics and related parts, and look forward to your future posts, :D Perhaps a quick sketch as to how the gas line up the centre would fit into the rotating part so the gas line doesn't wind up on itself and still keeps the seal on the rotating arm? Thanks for the reply I appreciate it, your knowledge on gas turbines would be much appreciated here.

The cheat I pm'd u :D

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re: New ramjet experiments

Post by Irvine.J » Sun Dec 03, 2006 5:59 am

As Najim requested i've hacked off a small 1/2 inch piece of the tail cone. The original diameter was 3 cm, with an area of 7.06sqcm

Now its 1/2 inch shorter with a diameter of 3.5cm and area of 9.61, a difference of 2.55 sqcm. I know it doesn't sound like much, but the exit nozzle is considerably larger, and will exponentially grow each time I chop a bit more off, so I'll keep my cuts short. I'll be running it in about 3 hours, stand by.

After one or two more cuts it will be really easy (instead of really fidgety) to remove the second baffle, so we might get to that soon.

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