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# Air Nozzle Question, should be easy?

## Air Nozzle Question, should be easy?

(OP)
Hello
I am self-learning the DeLaval nozzle, or Convergent-Divergent nozzle, and have read much from many different sources.
Have one question about the C-D nozzle with air.

The standard math shows choking at Mach 1, and the math derivations describe this. In my readings, I have found a single reference that does not agree with the standard formulas, taking into consideration real gas effects. This fellow, Abramov, is saying that considering air as a real gas, the throat critical flow is not M=1, but is instead much lower at M=0.5345 for air. His conclusion is that the effect of increasing velocity at the diverging section can be achieved with all velocities less than M=1 in the pipe, thereby avoiding Mach waves and shock. This seems odd to me.

QUESTION: Is this a legitimate statement, or is this false? If false, can you point to the falsity?

This is an interesting question because I can see two possible answers, and both contain amazing implications.
1. Abramov is correct that in practice, the DeLaval effect can occur at M=0.5345 at throat, which implies all other reference materials and texts are erroneously assuming ideal gas behavior for air in a simple C-D nozzle. For this case, it leads to many energy-efficient applications of devices that could avoid shock entropy generation.
2. Abramov is not correct. He has generated a steady stream of patent applications and some granted patents over the last decade, all of which are based on this core idea of when the Delaval effect occurs. I doubt he has made a mistake, which then leads to the possibility of a complicated, long-term Scam or ruse. Equally amazing possibility here.

Abramov does supply a derivation of his math, and I can see the algebra is correct there, but is there some error buried within this derivation that you can identify? Possibly the very first step of his math contains an assumption that is wrong? If Abramov's documents are part of a Scam, it should be possible to reveal that via his math derivation steps, but my ability level is not high enough to see if there is an error buried there, especially if the error was purposely buried.

Attached is an edited pdf excerpt from his original lengthy document. Equations 6.1 to 6.9 show his derivation.

Abramov also states that "in practice" the DeLaval effect is seen at M<1. If a person has hands-on experience with C-D nozzles, then this is another path that could be used to reveal if Abramov is telling the truth or not.

Any help would be much appreciated. I hope that you see this as an interesting problem. Of course, I can send you any additional material, if needed.

### RE: Air Nozzle Question, should be easy?

This reminds me of something my Dad taught me. If someone backs up to a wall, and takes on the world, BE CAREFUL! They either know something you don't, or they are crazy.

Good Luck,
Latexman

### RE: Air Nozzle Question, should be easy?

(OP)
I tend to agree with you, but that is only anecdotal. Was hoping some forum reader might be confident with the standard math derivation for Mach1 choking, and would be able to point out where in Abramov's math derivation there is an error. His documents are lengthy, 200+ pages each, and make a convincing argument, on the surface anyway. Clearly, a large amount of effort and expense and apparent expertise has been devoted to these docs. There are some red-flags in his docs, but the math derivation for choking is where the make-or-break will be proven, IMO.
If you want to see the raw data of all his writings, best site is ESPACENET, search on Yuri Abramov. Here, can download pdfs, and can also view the correspondence between patent offices and him, for each of the files.
After reading his raw data, you will be appreciative of my condensed version pdf attached to original post!
I am still hoping that a forum reader will be able to provide some assistance with the math derivations; both the classic method and Abramov's seem equally correct to my level of understanding, and that is the mystery.

### RE: Air Nozzle Question, should be easy?

The USPTO doesn't necessarily check the physics; their only bete noir is anything over-unity, if you stay away from any such claims, they'll give you a pass. Your invention doesn't have to work; which is why prototypes are not required. In some cases, the patent expired before the actual technology was put into use; Julius Lilienthal's invention of the field effect transistor (FET) wasn't physically realized until 20 years after patent award

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers Entire Forum list http://www.eng-tips.com/forumlist.cfm

### RE: Air Nozzle Question, should be easy?

(OP)
Good point IRstuff, I am no expert on patents, but believe it is only the numbered claims that are being patented. The many pages of description are only included to give background detail to the claims. This implies the description is not checked for accuracy by patent office.
Either way you look at it, Abramov is a master in his field; that field being compressible flow theory, or that field being able to weave a very complex, multilevel scam!
He submits patent applications every year or so, with different titles, but the description content is mostly cut and paste identical between all of them. This could point to an attempt to claim "patent pending" since some of the applications are always in process at any given time. But that is just conjecture, his math derivation is where the proof will be found.

### RE: Air Nozzle Question, should be easy?

Jerome Lemuelson was invention scammer, par excellence; he used continuations to masterful level, to the point where he got awarded patents for things invented by others, VCR, bar coding, etc.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers Entire Forum list http://www.eng-tips.com/forumlist.cfm

### RE: Air Nozzle Question, should be easy?

(OP)
Good to know about other scammers. Abramov's arguments are just so tantalizing in their potential applications, I can't let it drop without seeing proof of fraud. Will need to roll up my sleeves and do the math derivation comparison, side by side, on my own it looks like. It is do-able....given enough time and effort! He is not claiming others' work, instead he is claiming performance not commonly discussed, reason being most ejectors or nozzles are operated choked, not slightly before choking, that is rarely documented in papers. Good news is he supplies a large quantity of data, so there is plenty to work with.

### RE: Air Nozzle Question, should be easy?

That presumes that CFD is an independent method of analysis, but it's not necessarily that, since CFD is a conventional physics-based solution engine.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers Entire Forum list http://www.eng-tips.com/forumlist.cfm

### RE: Air Nozzle Question, should be easy?

I'm not sure he's talking about CFD, per se; it looks more like he's talking about Navier-Stokes at a macro level, which isn't necessarily true of CFD. Nevertheless, CFD does use Navier-Stokes, but at a more microscope level, albeit, not necessarily at the atomic level; that said, CFD does a credible job of modeling turbulence, vortex shedding, boundary layer effects, etc., which is not doable in anything done by hand.

Of concern is his continual referencing Feynman's Lectures on Physics, which is the text I had in college, but that was more than 40 years ago, so for a patent awarded in 2018, it's an oddly anachronistic reference.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers Entire Forum list http://www.eng-tips.com/forumlist.cfm

### RE: Air Nozzle Question, should be easy?

Note while that Abramov is prolific with applications, he only has a couple of patents awarded, although I didn't do an exhaustive search, and their not related to the subject at hand
https://www.freepatentsonline.com/result.html?sort...

I'm SHOCKED!!! He actually has a 9-page patent award: https://www.freepatentsonline.com/7313287.html Although, not sure why he got that awarded; we studied hexagon pixel arrays in a class in college, 43 years ago. That was pick-breaker; turned out it wasn't possible to come up with a closed form solution for the 2D Fourier transform for the image

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers Entire Forum list http://www.eng-tips.com/forumlist.cfm

### RE: Air Nozzle Question, should be easy?

(OP)
Here is one red flag, attached [936] to [946]. To my somewhat incomplete level of knowledge on the subject, it appears the formula at [943] is only half-true, and it appears to me the formula at [945] has wrong units of moles when value of R is using Kg. It would be helpful if a forum reader could confirm my suspicion here. Is this showing Abramov's magician card trick with the formulas? I mean to say that using R which = Cp-Cv is to look at energy of PV. But total energy will use Cp to include the sum of both PV and internal temp energy. Is he mixing and matching the energy portions incorrectly, it looks that way to me.

### RE: Air Nozzle Question, should be easy?

(OP)
Yes, that is correct the two recent awards are more narrow, for the water condensation only. The non=awarded applications are the ones that discuss the energy from air heat to kinetic energy.

### RE: Air Nozzle Question, should be easy?

Might be easier in the future to directly reference the patent application as a whole https://www.freepatentsonline.com/20180266395.pdf

It does seem like sloppy math/physics. 44.64 is the number of moles in a "cube" meter, but its mass is only 1.225 kg. Other sloppiness is that certain values are at STD, which are not the conditions he's citing.

TLDR, so I'm not going to chase that rabbit at 107 pages for the entire document

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers Entire Forum list http://www.eng-tips.com/forumlist.cfm

### RE: Air Nozzle Question, should be easy?

(OP)
The standard gas flow energy equation includes Cv*T for heat energy, 1/2*V^2 for kinetic energy, and PV or mRT for PV energy, all being summed. Or alternately, CpT plus the K.E.
He shows input energy being only CvT, but then shows output energy as only mRT (with incorrect units). This is BOGUS. He is conveniently ignoring that all three of Pressure, Volume, and Temperature will change together.
I know his text is TLDR, but he did lure me into reading thoroughly. His text contains majority of correct information, but the conclusion is where he pitches the curve ball. Like most con games, it is based on fact but skewed when it progresses forward.
Of course, I could be wrong on that, which is why I posted in the first place to see if any forum readers might have some specific insight. The comments have helped me immensely to collect thoughts on this. A valuable learning experience. Thank You for the thoughtful comments.

### RE: Air Nozzle Question, should be easy?

Hi,
To you and others
A serie of videos about compressible flow is available on Youtube :
The lecturer Prof john R.Biddle may want to support your query: jrbiddle@cpp.edu
The videos cover incompressible and compressible flow (34 videos).
Good luck
Pierre

### RE: Air Nozzle Question, should be easy?

(OP)
Thank You Pierre,
That video is EXACTLY what I am seeking. I will study closely to gain some footing, and then will reach out to Prof Biddle if and when I get stuck.
Very good video, it matches exactly what I was trying to explain in above posts,
THANK YOU IMMENSELY, right on target. The derivation is the true method to de-bunk Abramov, who knows? Need real proof to be assured.
RLund

### RE: Air Nozzle Question, should be easy?

HI,
The text book to support the videos is the following :
Frank White, Fluid Mechanics, 5th ed., McGraw-Hill, 2016
note : More recent editions are available .

Pierre

### RE: Air Nozzle Question, should be easy?

Hi,
Update is welcome !
Pierre

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