regenerative ramjet engine

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nanotech1
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regenerative ramjet engine

Post by nanotech1 » Sat Dec 30, 2006 3:35 pm

ok look at this and try to comment this one because it seems to be kind of cool design

http://www.google.com/patents?vid=USPAT3841092

is this design worth any consideration :) or is it a doom one :(

nanotech1
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regenerative ramjet engine

Post by nanotech1 » Sun Dec 31, 2006 5:28 pm

here the whole patent in JPEG format :)

please take into account that this ramjet employs a feedback system to direct some exhaust to the intake so it could self substain a static thrust

COOL COOL COOL :) :)

but does it work please comment

steve

P.S i just hope that the files resolution is good enought to read the text :/
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larry cottrill
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Regenerative Ramjet

Post by larry cottrill » Mon Jan 01, 2007 8:16 pm

Yes, that's the one I was talking about a few years ago on the old forums. Not the first cyclical flow jet design, but probably the simplest ever patented! Thanks, nano, for giving everyone a chance to see this! My Cyclodyne design came long after this, of course, but I had not seen this at the time - I ran across it (and many others!) while doing my own patent searches. While this seems like not a very "practical" design for use in a vehicle, the simplicity of it is a marvel. Even the description is a wonder of conciseness and unpretentiousness.

One of the most sophisticated designs I saw didn'r even have a physical boundary between the two streams, just a kind of "shear plane" between the hot and cold air. It had a patent description about eight pages long, jam-packed with differential equations relating to mass flows at different stations in the device. It was a "folded" sort of engine - the most physically compact engine I ever saw a patent for. Someday maybe I'll rediscover the patent number so someone could post it - I think it was from the late 1970s or early '80s.

L Cottrill

nanotech1
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Regenerative Ramjet

Post by nanotech1 » Tue Jan 02, 2007 3:09 am

Larry do you think that this design could be self substaining for static thrust operation because like the patent description i like the idea of using dynamic pressure flow of the combustion chamber exit pipe
to supercharge the intake part of it as long has the exhaust gaz to intake charge ratio disolution doesnt flame out the ramjet in a way what i am trying to say is making a ramjet engine behave like in a gaz turbine it would be run like a dynamic brayton cycle gaz flow but without having any moving parts

yep a solid state turbocharge ramjet COOL :)

steve

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self substaining ramjet engine

Post by nanotech1 » Tue Jan 02, 2007 4:25 am


Mark
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Post by Mark » Wed Jan 03, 2007 3:34 pm

"substantial engine thrust as zero and near zero engine velocity". This sounds like one of those gray area engines. Some might call it a pressure jet and some a ramjet just as Foa says the valveless pulsejet and subsonic ramjet line of demarcation becomes blurred. Maybe it's a valveless pulsejet or perhaps one could kind of liken it to a half of a liquid fueled rocket, preheating the fuel to do work. It doesn't have reed valves so it can't be a valved pulsejet. ha
Mark
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Stuart
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Re: Regenerative Ramjet

Post by Stuart » Sat Jan 06, 2007 1:40 am

Larry Cottrill wrote:Yes, that's the one I was talking about a few years ago on the old forums. Not the first cyclical flow jet design, but probably the simplest ever patented! Thanks, nano, for giving everyone a chance to see this! My Cyclodyne design came long after this, of course, but I had not seen this at the time - I ran across it (and many others!) while doing my own patent searches. While this seems like not a very "practical" design for use in a vehicle, the simplicity of it is a marvel. Even the description is a wonder of conciseness and unpretentiousness.

One of the most sophisticated designs I saw didn'r even have a physical boundary between the two streams, just a kind of "shear plane" between the hot and cold air. It had a patent description about eight pages long, jam-packed with differential equations relating to mass flows at different stations in the device. It was a "folded" sort of engine - the most physically compact engine I ever saw a patent for. Someday maybe I'll rediscover the patent number so someone could post it - I think it was from the late 1970s or early '80s.

L Cottrill
Larry, this is what I've been working on for years. I can tell you it does work, but not very well (at least so far). Maybe I should have patented what I have. Actrually, the design makes some mistakes, and there is an easier way to build it. I doubt the guy got it working the way he has it, without using forced air like everyone else.
I'm writing an automated airplane designer in java, useful later when you guys get ready to bolt a p-jet onto some wings

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Re: Regenerative Ramjet

Post by Stuart » Sat Jan 06, 2007 1:42 am

nanotech1 wrote:Larry do you think that this design could be self substaining for static thrust operation because like the patent description i like the idea of using dynamic pressure flow of the combustion chamber exit pipe
to supercharge the intake part of it as long has the exhaust gaz to intake charge ratio disolution doesnt flame out the ramjet in a way what i am trying to say is making a ramjet engine behave like in a gaz turbine it would be run like a dynamic brayton cycle gaz flow but without having any moving parts

yep a solid state turbocharge ramjet COOL :)

steve
If you and Larry want to discuss what I know privately, let me know. I have some insights. The design has it's tricky points (don't they all).
I'm writing an automated airplane designer in java, useful later when you guys get ready to bolt a p-jet onto some wings

krzys Mnich
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Re: regenerative ramjet engine

Post by krzys Mnich » Tue Jul 22, 2008 8:22 pm

I guess many people thought out an engine like this, however, not many of them calculated it. I did, many years ago - and it cannot work, unfortunately.

The point is, that the intake air is accelerated by the exhaust gas, but also heated by it. The hot air can't be efficiently compressed, and it is imposiible to obtain the initial pressure in the combustion chamber in this way.
It is possible when the working medium is not a gas, but a steam, that may condense in contact with a cold liquid and increase its density dramatically. Such steam injectors were widely used in steam engines, but they don't work with gases.

Is it possible to make it work? One way is to cool the exhaust gas (the most efficient way is to exchange the heat with the compressed air after the diffuser), but this also cannot work! The heat lost in the heat exchanger is proportional to the velocity lost, so we finally haven't enough speed to compress the air again. Maybe one can think out a heat exchanger without speed lost?

There is another possible way to make it work: decrease the velocity lost. The idea is to mix the exhaust gas with the intake air in a vortex chamber, similar as a "vortex tube" http://en.wikipedia.org/wiki/Vortex_tube
The velocity profile in the chamber tends to the rigid rotation, so the external layers move quite fast, while the core rotates slowly - but the temperature is uniform in the equilibrium state. So, it is theoretically possible to compress the external layer of the vortex to the pressure in the combustion chamber.

Of course I never tested that idea, nor even calculated it in details. But it may be interesting...

regards

krzys

ps. It's my first message, hello to all. You recalled my very old (and very theoretical) hobby :-)
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Regenerative ramjet with vortex mixing

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Re: regenerative ramjet engine

Post by metiz » Tue Jul 22, 2008 11:43 pm

CURSES! thats the 2nd time in 2 months that a idea I got was already pattented! :P
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Re: regenerative ramjet engine

Post by Mike Everman » Tue Jul 22, 2008 11:45 pm

Welcome, krzys, and Faaaaaaascinating. Nothing to add, just Faaaaaascinating.
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krzys Mnich
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Re: regenerative ramjet engine

Post by krzys Mnich » Wed Jul 23, 2008 7:07 pm

Thank you, Mike, for the welcome.

Larry, could you find more about the patent you mentioned:
One of the most sophisticated designs I saw didn'r even have a physical boundary between the two streams, just a kind of "shear plane" between the hot and cold air. It had a patent description about eight pages long, jam-packed with differential equations relating to mass flows at different stations in the device. It was a "folded" sort of engine - the most physically compact engine I ever saw a patent for. Someday maybe I'll rediscover the patent number so someone could post it - I think it was from the late 1970s or early '80s.
There may be some smart tricks worth attention.

However, the engine seems to be too sophisticated for amateurs. Pulsejets are easier to build, I guess.

regards

krzys

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Re: regenerative ramjet engine

Post by larry cottrill » Thu Jul 24, 2008 6:51 pm

krzys Mnich wrote:Larry, could you find more about the patent you mentioned:
One of the most sophisticated designs I saw didn'r even have a physical boundary between the two streams, just a kind of "shear plane" between the hot and cold air. It had a patent description about eight pages long, jam-packed with differential equations relating to mass flows at different stations in the device. It was a "folded" sort of engine - the most physically compact engine I ever saw a patent for. Someday maybe I'll rediscover the patent number so someone could post it - I think it was from the late 1970s or early '80s.
krzys -

This was unearthed in about 2001 or 2002 -- I'm sure I printed a copy of it, but it's probably so far buried in my junk paper mess that finding it would be a major project. I need to do some cleaning up at home, and I'll keep it in mind. I know I'll recognize it when I see it again. But, it may be a while before this happens, or of course, it may be just lost for good. Someone could search for it, but you have to remember that on patent searches you can't just look for "jet engines" -- a lot of them are listed as combustors, heaters, air movers, etc. etc. You have to know your way around the verbal territory. That's one of the reasons professional patent searches cost the big bucks (dollars).

And yes, this was WAY more sophisticated than your average valveless pulsejet. It was made up of carefully plotted smooth curves in three dimensions; I doubt that the concept would even work if there was any "roughness" to it (like using a bunch of conical segments). Of course, I could easily be wrong.

L Cottrill

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Re: regenerative ramjet engine

Post by Stuart » Sat Jul 26, 2008 4:36 am

I can tell you that I have worked extensively with this kind of design and while what is pictured will "run" if configured as a pressurejet, it will not run as configured as a gas burning self sustaining jet. Unless by running you mean having cold air come in and hot air come out, which is a jet without poop.
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Re: regenerative ramjet engine

Post by Viv » Sat Jul 26, 2008 1:34 pm

The first rule of thermodynamics states very clearly that you can not win! I am afraid this design comes under that.

The major killer for all ideas like this is "pressure loss", some thing turbine builders know all about as its a design factor for them, I would question the ability of the recirculated exhaust gas to usefully add pressure or volume to the intake by entrainment, any energy taken from the exhaust is lost to propulsion, the losses will add up and negate the gains.

I would recommend Foa's book on propulsion as it covers these types of engine and other interesting types as well.

Viv
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