Inlet-Efficiency Question Regarding Porous Ramps

KJ_Lesnick

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I was wondering about porous ramps/surfaces and how much efficiency they produce in inlet-designs over non-porous ramps/surfaces. I also wonder what effect the size of the pores play on boundary-layer removal (Instinctively larger sounds better, but many ultra-efficient inlets like the XB-70 use rather small pores, and most laminar flow control concepts use very very small holes)


KJ Lesnick
 

rousseau

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The ramp was used to press the bountary layer deviating the direction of inlet. It is clearly that structure of ramp is simple than any conventional inlet though, but the thickness of structure of head-on/frontal resistance of fixed conventioanl inlet is smaller than ramp(DSI).
The non-pore ramp certainly is advanced than pore used ramp. The WHY is always more important than WHAT. You could think why the pore must be used and the effect.
The first benefit is "simple", so if you have to process pore on Ramp, yes, it can reduce weight, we say reluctantly, but you lost simple as one of the benefit in process.
Historically, you can see the pore socalled, was not only used Ramp inlet, also former VG inlet before 70's, but the pore was nolonger being on VG inlet after F-14 emerged.
The key point here is boundary layer. So we can ask farely, if the Ramp was formed improvedly, why take pore unneccessarily.

Of cource, if you give me any practical case, I maybe analysis much better for you, but I don't know why do you ask such superior question.
 

KJ_Lesnick

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I mean this with no offense, but I really didn't understand much of what you said.

Thank you though,
KJ Lesnick
 

Justo Miranda

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Some conventional and esoteric stuff at
http://newsgroups.derkeiler.com/Archive/Rec/rec.aviation.military/2007-06/msg00697.html

http://www.usenet.com/newsgroups/rec.aviation.military/msg15671.html

http://www.thewebfairy.com/missilegate/rfz/swaz/chapter13.htm
 

KJ_Lesnick

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Justo Miranda,

Thank you for the links... I really appreciate them, though when it came to porous ramps, I was talking about inlet-ramps and surfaces that had lots of small holes in them to skim off turbulent air -- like on the F-4 and F-15's inlets. What is mentioned in this article is a little beyond the scope of what I was looking for.

In either case... I'm confused about the first link, which said the Germans experimentally managed to make it work in properly-shaped aerodynamic structures. In others it said it shared no little success (does no little success mean "no success" or "major success" as in "it was not a little success, but a major success"?)

The third link sounds a little bit suspicious in terms of accuracy, but I could be wrong

Regarding the foamed aluminum -- the foamed aluminum is created using the diffusion-bonding process -- which is actually something I know, and have likened it to glass-blowing except doing it with metal (superplastic-deformation/diffusion-bonding). This is quite amazing as this is like 20 years ahead of the US and USSR. I didn't know diffusion bonding was possible (at least superplastic deformation) with aluminum although I know it could be done with titanium and damascus steel.


KJ Lesnick
BTW: The article said the foamed aluminum used could take 1000 C or so. I take it the foamed aluminum was able to take higher temperatures than regular aluminum sheets because of the high internal surface-area able to reflect a lot of heat around?
 

Justo Miranda

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I do regret that all the sources mentioned in the Luftschwamm are doubtful.
There is another possible line of research, the work by Dr. Werner Pfeninger on the Northrop X-21A about the laminar boundary layer and suction surface.
In my opinion, the Damascus Steel is not a good example as it was obtained from an iron ore with a high content of carbon, being afterwards pounded to increase its density.
The ideal porous material could be obtained in Zero-G conditions injecting gas in a mass of melted metal.

http://archaeology.about.com/od/ancientweapons/a/damascus_steel_2.htm

http://archaeology.about.com/od/ancientweapons/a/damascus_steel.htm

http://en.wikipedia.org/wiki/Damascus_steel

http://en.wikipedia.org/wiki/Northrop_X-21

http://home.att.net/~jbaugher2/b66_6.html
 

KJ_Lesnick

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Justo Miranda,

I do actually know a thing or two about the X-21A -- From what I remember, the problem with the set-up was that the pores kept getting clogged up, and due to the shape of the pores it was very difficult to practically clear them in-flight by blowing the crud that embedded itself in the pores out.

The statement about Damascus-Steel was not meant to state that it would make a good porous material. I just know it's capable of superplastic-deformation.


BTW, I got two questions
-When did the USA and UK start studying the foamed-metallurgy from the Germans?
-When did the USA reach a state where they could produce this stuff themselves?
 

Justo Miranda

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I have not been able to find any reliable reference on the subject, prior to the publication of the book "The High Frontier" by Gerard O'Neill, William Marrow and Company, ISBN 0962237906,in 1976.

Apparently, the manufacturing of the "luftschwamm" by the Allies was unsuccesful. Perhaps that is the reason why they used stainless steel panal cells as insulation stuff in the Mercury, Gemini and Apollo spaceships......
It possibly may be only manufactured in Zero-G conditions.

http://www.freerepublic.com/focus/f-news/1068606/posts

http://groups.google.co.id/group/rec.aviation.military/browse_thread/thread/cb5aec657ef64b82
 

KJ_Lesnick

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Justo Miranda

parently, the manufacturing of the "luftschwamm" by the Allies was unsuccesful. Perhaps that is the reason why they used stainless steel panal cells as insulation stuff in the Mercury, Gemini and Apollo spaceships......

Wow, I'm suprized it wasn't do-able, especially when you consider that some diffusion-bonding techniques were available in the early to mid 1960's... for example General Electric designed the compressor blades of the GE-4 out of wide-chord diffusion bonded blades. I'm surprised NASA didn't use any of the diffusion-bonding tech (which GE had some).

It possibly may be only manufactured in Zero-G conditions.

How would you simulate zero-G conditions? Wouldn't that mean you'd have to manufacture the stuff in a vomit-comet?


BTW: Thank you for the links
 

KJ_Lesnick

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rousseau,

The porous obviously was used for drawing redundant boundary-layer. This is not a new tech, US studied it 30 years ago.

*THAT* I know (I was temporarily side tracked by the foamed metal thing, however) -- In fact it was more like 40-50 years ago (The F-4 Phantom used it, and it entered service in 1960).

What I was wondering was how much inlet efficiency was gained by using porous ramps and the effects of the size of the pores' effects on the inlet efficiency at various mach-numbers compared to a non-porous ramp.


KJ Lesnick
 

rousseau

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Do you want to determinate quality or quantity?
There is no wind tannel, there is no way to calculate the efficient number. It is hardly to say 4.6 or 0.73.
But concerning to the attribution, non porous clearly is advanced much more than apertured DSI. You can deduced it by yourself. If the ramp was formed so perfectly that is enough to press boundary layer out, why it has to be holed?
 

KJ_Lesnick

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rousseau said:
Do you want to determinate quality or quantity?
There is no wind channel, there is no way to calculate the efficient number. It is hardly to say 4.6 or 0.73.
But concerning to the attribution, non porous clearly is advanced much more than apertured DSI. You can deduced it by yourself. If the ramp was formed so perfectly that is enough to press boundary layer out, why it has to be holed?

When you say pressed the boundary layer out, you mean like an F-35 style design right?


KJ
 

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