Pipe fitting Ramjet

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nitroburn
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Pipe fitting Ramjet

Post by nitroburn » Sun Jun 04, 2006 1:56 am

I've been playing around with a 'ramjet' if that is what it is yet but i have a few questions. (dont knock its noobishness :P, i know its not purrdy)

Does a compressor provide enough air movement to properly sustain a ramjet while stationary? I would assume it would depend on placement and if its blowing into the hole or around the ramjet aswell.

The 'ramjet' is made from 2 reducers and a 1 1/2inch D x 2inch L nipple
1 reducer is a 1/2 to 1 1/2 inch, the other is 1 inch to 1 1/2 Inch. Inside as the flame holder/diffuser I used a lid from a canning jar I cut to fit inside and punched holes in. I have a 1/4 inch tube coming off a propane torch providing fuel. its attached to a 1/4 inch copper tube that is slighly flattened then flared at the end.

I am able to get it to stay lit even with the compressor shooting lots of air through, but i really dont see much thrust (was that expected) until i turn the tank over then the flame at the end gets nice and blue and very pointed and the pulsejet wiggles on the stand. I'm thinking I'm just not providing much fuel.

nitroburn
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re: Pipe fitting Ramjet

Post by nitroburn » Sun Jun 04, 2006 6:38 pm

When is a ramjet, a ramjet?

I know with the pulsejets its easy to tell if its operating as it should because it makes a horridly loud noise (if it ain't loud, it ain't runnin :P)

But what about with ramjets? Just if there is thrust? or am i playing with a glorified torch :P

Zippiot
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re: Pipe fitting Ramjet

Post by Zippiot » Mon Jun 05, 2006 5:20 pm

I have a modified ramjet from the maggie muggs plans, it is louder than any turbine or pulsejet I have ever heard. The police have shown up a few times from noise complaints.

An air hose will not give you the airflow you need, a leaf blower or powerful shop vac will do the trick. You can get up to 8 pounds of thrust off of a 5 hp shop vac.
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Re: re: Pipe fitting Ramjet

Post by larry cottrill » Mon Jun 05, 2006 6:06 pm

Zippiot wrote:I have a modified ramjet from the maggie muggs plans, it is louder than any turbine or pulsejet I have ever heard. The police have shown up a few times from noise complaints.

An air hose will not give you the airflow you need, a leaf blower or powerful shop vac will do the trick. You can get up to 8 pounds of thrust off of a 5 hp shop vac.
Are you SURE of that thrust figure? Of course, 5 hp is quite a blower!

Here's what I'd like you to do if you have what you think is a reliable thrust measuring setup: (a) Measure the thrust from the blower nozzle alone, without the ramjet in the way; (b) Measure the thrust from the blower alone (i.e. no firing) with the ramjet mounted in place - the difference between this and the previous figure will show us the net engine drag; (c) Measure the best thrust you can get with the best lean burning you can obtain. The difference between this and the original measurement at (a) is the NET usable thrust.

Of course, you are required to film the whole process and report back ;-)

L Cottrill

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re: Pipe fitting Ramjet

Post by Zippiot » Mon Jun 05, 2006 6:14 pm

Did it a while ago :) just no film, I'll pice it back together and film that now that I have acess to a digital vid camera.

It made less than 1 pound shooting through the ramjet, about 1 pound with the hose alone (there is a nozzle on the end of it) and about 7.5+ under power!! Using bacon grease mixed with white gas i got that high, kerosine made about 4 pounds and gasoline made 3...

Sorry but it isnt the modified maggie muggs, it was my own design. The modified makes about 3 pounds of thrust, but it makes noise like no other!!!
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Re: re: Pipe fitting Ramjet

Post by larry cottrill » Mon Jun 05, 2006 6:18 pm

Zippiot wrote:Sorry but it isnt the modified maggie muggs, it was my own design. The modified makes about 3 pounds of thrust, but it makes noise like no other!!!
Zip, that probably doesn't sound like much to you, but if you basically kept the lightweight structure of the design, that's fantastic! Please provide more info on your build of the engine!

L Cottrill

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re: Pipe fitting Ramjet

Post by Zippiot » Mon Jun 05, 2006 6:43 pm

Well first off I found 2 ss mugs that would fit together, with a little force and heat. I changed the deasign of the flame holder to a slotted slanted piece of metal. Also restricted the itnake using a alrge washer, this seemed to prevent flame coming out the front and suer increased the itnernal pressure.


edit-and I cannot spell, I will leave it the way it is just for laughs :)
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re: Pipe fitting Ramjet

Post by larry cottrill » Mon Jun 05, 2006 7:31 pm

Zip -

Ah, yes, I remember that part of the discussion - I didn't remember that you ever said anything about performance, at that time, though.

Here's the significance of the washer, I think: It will always theoretically be better to have a smooth diffuser than something like your washer - BUT, if the restriction of the washer gives you better performance (i.e. higher static pressure, which keeps the flame back where it belongs), the problem is probably that the original diffuser design has too large an inlet. What you should definitely try (in my opinion) is to make a simple conical diffuser with a front end just a bit larger than the ID of your washer and the rear end to match what you have. I'll bet that sucker would do an even better job of generating thrust if the inlet flow were smoothed out!

Please consider trying this. Keep everything else the same, just develop a smooth diffuser with the reduced inlet size. The cone angle should be fairly small - a long cone is better than a stubby one, theoretically. So, your engine would end up somewhat longer than it is now.

L Cottrill

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re: Pipe fitting Ramjet

Post by Zippiot » Tue Jun 06, 2006 12:08 am

Ill need a welder for that, time to get off my butt and buy one. Sometime it backfired so powerfully that the vacume would stall ocasionally, super high pressure air shot right down the tube and disrupted the thing maybe...

I do need a better nozzle for the thing, was not getting the full power out of the fuel. If I grab a welder and redesign the nozzle and intake I might be able to up the power, who know by how much. Gonna need to grab some more 4 pound bacon packs from costco, the bacon grease really gives off a pleasant smell and loads of power :)


Great now I wanna re-assemble it, thanx for sparking my interest guys I didnt have enough on my plate already :)
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Re: re: Pipe fitting Ramjet

Post by larry cottrill » Tue Jun 06, 2006 5:35 pm

Zippiot wrote:Ill need a welder for that, time to get off my butt and buy one. Sometime it backfired so powerfully that the vacume would stall ocasionally, super high pressure air shot right down the tube and disrupted the thing maybe...
Ha! Reminds me of when I was first trying to start the Elektra I pulsejet and generally using too much air from the leaf blower at the intake. The thing would start to fire and kick back so violently it felt like the recoil from firing a 22 calibre pistol!
I do need a better nozzle for the thing, was not getting the full power out of the fuel. If I grab a welder and redesign the nozzle and intake I might be able to up the power, who know by how much.
Please start out by just modifying ONE thing - the diffuser, as described earlier. I'll bet you will be really surprised at the difference made by this one detail.
Great now I wanna re-assemble it, thanx for sparking my interest guys I didnt have enough on my plate already :)
That'll teach you to mess with us ... ;-)

L Cottrill

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re: Pipe fitting Ramjet

Post by Zippiot » Tue Jun 06, 2006 6:01 pm

Before I modify it would you like me to take a series of tests to see thrust/fuel consumption and all again?

Then modify it slowly and see what changes. I will need to build a better test stand, anyone have some good plans?

Also nitroburn, you may need to increase the length of your nozzle; the reaction (for me atleast) seems to be more effective underpressure.
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re: Pipe fitting Ramjet

Post by larry cottrill » Tue Jun 06, 2006 6:07 pm

I would run it again until you know that you know the rates of fuel and air that seem to give optimal (or the best you can get) results, and get these accurately recorded, along with the net thrust obtained. It's just a good idea to set an accurate "benchmark" before you make an important change, if you really want to learn from it.

L Cottrill

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