# DeLaval Subsonic Effect

## Main Question or Discussion Point

Have you seen this patent application?
US 2017/0316133 A1
Basically from my humble understanding, he is saying the DeLaval effect can occur at less than Mach 1 at the throat, with air about 0.5 Mach. Sorry, this doc is 100 pages, here are pertinent section numbers:
Standard equation EQ 1, section 157
His modified equations, EQ 6.13 section 643 and EQ 7.1 a-d section 685.
Also see section 693 for interesting statement.
I am curious what you think of this document? Some bold statements are being made about energy harvesting from ambient atmospheric heat.
http://www.freepatentsonline.com/y2017/0316133.html
Scroll down slightly to see blue ink, download patent image as a pdf.

Related Mechanical Engineering News on Phys.org
Gold Member
What exactly are you calling the "de Laval effect" here?

In a C-D nozzle, when the flow velocity increases through the diverging exit section.

Gold Member
Well I haven't read the patent, but if this person claims that you can have supersonic flow in a C-D nozzle without achieving sonic conditions at the throat, then he has a gross misunderstanding of thermodynamics and/or fluid dynamics somewhere in his patent.

russ_watters
Mentor
It's about the worst wall of text I've ever seen. It makes me wonder if it is designed to be unreadable*. There's no way I'm going to try to dive into it, but at face value the claims are highly suspect.

*The few paragraphs on the origin of life were helpful though.

JBA
Yes, I agree about the excessive text, but the question is about the equation 1 and 6.13 . He shows the derivation of 6.13 in preceeding equations, so using the pdf version it is possible to ignore the text and follow the equations instead. I cannot see where the trail is faulty from eq1 to 6.13. Need help from others to identify the error if it exists. He is saying that Eq 1, standard, assumes incompressible flow at subsonic entry when in reality that inlet flow is slightly compressible. He shows equation steps to adjust equation 1 and result is 6.13. If there is an error in the equations, can this error be identified? Or, from your experience with C-D nozzles, is it conceivable to have a choking but subsonic at exit?

The question is the validity of the equation steps shown as EQ 6.1 through 6.13, found in document sections (632) through (656).

It might be easier to see by comparing EQ 1.b to EQ 6.8, these are located in sections 155 and 638.

Gold Member
Equation 1b is canonical and can be found in any gas dynamics textbook. It makes no assumption about incoming compressible flow whatsoever. In fact, it really doesn't make any assumption of any kind other than a steady, inviscid flow.

Equation 6.13 is also canonical and can be found in any gas dynamics textbook. It relates the ratio of the area to the sonic area for any given Mach number.

Equations 7.1 are incorrect, and his numbers from them are therefore incorrect. They appear to be improperly-simplified versions of the standard isentropic flow ratios with exit conditions substituted into them. These equations should be fairly standard (and he even references the standard answer of $p_0/p_e = 1.893$ in the document, though this value changes depending on $M_e$, a fact he doesn't seem to appreciate). It appears this comes from math errors in his equation 6.11, where the $\gamma/2$ term should be $(\gamma-1)/2$.

His paragraph 693 sounds like word soup to me. I have no idea what he is attempting to say.

I also don't see anywhere a claim that you can achieve supersonic flow without reaching Mach 1 at the throat. The simple answer is that you cannot, and equation 1b proves that (or can with a little extra math).

However, this is a different question than asking if a nozzle can be choked but subsonic at the exit. The answer to that is a resounding yes. Choking just means the flow is Mach 1 at the throat, and occurs at a much smaller pressure ratio than a uniform supersonic exit. If you just barely achieve sonic flow at the throat but don't have enough pressure ratio to fully start the nozzle, then a normal shock develops between the throat and the exit, and everything downstream of that is subsonic. This is, again, something found in any gas dynamics textbook.

I attempted to read some of it although as others have pointed out it is quite difficult. In addition to randomly, and pointlessly, discussing the origins of life he also talks about “universal background matter” and “universal background energy”.

It’s not even entirely clear to me what the “invention” is. I think he is claiming to convert the thermal energy of ambient air into kinetic energy then convert this kentic energy into electrical energy with a turbine. The author mistakenly thinks that as a fluid accelerates through a nozzle, this increased kinetic energy comes from the thermal energy (Browninan motion) of the fluid.

At one point he claims that efficiency greater than 100% are achievable.

russ_watters
jrmichler
The patent examiner got lucky on this one, the inventor expressly abandoned the patent application. Twenty claims, the first of which has 2846 words. I skimmed a few of the claims. They all appear to be technobabble.

Asymptotic and russ_watters
russ_watters
Mentor
Given this:
At one point he claims that efficiency greater than 100% are achievable.
...and this:
The patent examiner got lucky on this one, the inventor expressly abandoned the patent application.
I think we can safely judge this bunk close the thread as moot. Thanks guys.