Tesla turbine and Coanda effect
te...@execpc.com
>Seeing the squabble over friction or adhesion when explaining the
>Tesla turbine, I wonder if the Coanda effect, or some variant of it,
>figures in the behavior of the steam or compressed air as it does its
>work on the turbine runners.
>Very briefly, the Coanda effect describes the tendency of a jet of
>fluid to attach itself or "stick" to a surface, curved or flat.
>In the latter case, if the jet is introduced at an angle to the flat
>surface, it will bend down and cling to that surface. The jet will
>be very resistant to separation, especially if ambient air is prevented
>from freely reinvading the surface. The surface itself will be
>below atmospheric pressure. Is the adhesion spoken of quite often in
>connection with the Tesla turbine in fact the Coanda effect?
Tesla Engine Builders Association Inc. (TEBA) 9/10/98 wrote:
While not using this term in 1911, the effect is exactly what Tesla
was explaining.
Tesla's description of this discovery is contained in an article
appearing in the September 18, 1911 periodical "Motor World":
"Dr. Tesla Talks Of Gas Turbines." Also reproduced in our 1994 text:
"Tesla's Engine - A New Dimension For Power," pages 97-100.
Quoting Tesla:
"I have been working at this a long time. Many years ago I invented
a pump for pumping mercury. Just a plain disk, like this, and it would
work very well. 'All right,' I said, 'that is friction.' But one day
I thought it out, and I thought, 'No, that is not friction, it is
something else. The particles are not always sliding by the disks,
but some of them at least are carried along with it. Therefore it
cannot be friction. It must be adhesion.' And that, you see,
was the real beginning.
"For if you can imagine a wheel rotating in a medium, whether the
fluid is receiving or imparting energy, and moving at nearly the same
velocity as the fluid, then you have a minimum of friction, you get
little or no 'slip.' Then you are getting something very different
from friction; you are making use of adhesion alone. It's all so simple,
so very simple. This is the greatest of my inventions...."
Recently we received a letter from the Tesla Coil Builders Association
(TCBA) President, Harry Goldman, regarding this misunderstanding.
Included was a copy of "Tech Musing" by Don Lancaster, appearing in
"Electronics Now," Oct. 1998 issue. In this piece Don includes a listing
of 10 Tesla turbine references he describes as "real science" as well as
listing his three opinions as to why the Tesla turbine/pump can't possibly
operate efficiently.
Mr. Goldman included a note attached to the copy of Don's article stating:
"Don Lancaster has never been able to say a good thing about Tesla.
He's been pretty quiet since my letter to the editor a while back.
Now he's attacking Tesla via the Turbine. I feel you are best
qualified to comment on this."
Following are Don's erroneous assertions and our response;
(A) "Thermodynamic Reversibility Violations"
This opinion is based on Don's mistaken belief that the turbine
operates by friction, thereby giving up the majority of energy as
unrecoverable waste heat. This is, of course, not true.
The majority of the "real science" references offered by Don involved
the work of Professor Warren Rice. The most recent of Prof. Rice's
papers listed by Don is dated 1970. Don is apparently not aware of
the more recent work on the subject which includes Professor Rice's
final work, published just prior to his retirement in 1990, entitled:
"Tesla Turbomachinery."
In this 1990 paper Prof. Rice states: "With proper use of the
analytical results, the rotor efficiency using laminar flow can be
very high, even above 95%." Tesla claimed 98%. So just how does
a 95%+ efficient runner give up the majority of its energy to waste
heat as has been claimed by Don? The fact of the matter is that the
Tesla turbine IS thermodynamically reversible.
(B) "The turbulent flow or otherwise lousy fluid dynamics at the
inputs and outputs."
The input and outputs of a Tesla pump housing are very similar to
those encountered in many centrifugal types. Prof. Rice expresses
the opinion, in his 1990 paper, that pumping efficiency would,
although not strictly tested, probably be limited to approximately
65% due to losses at the inlet and outlet.
This is not unlike other bladed type pumps. Prof. Rice was only able
to offer his opinion in this regard, however, as he did not do testing
of a pump built in strict accordance to the Tesla design. His
experimentation instead involved "co-rotating disks" which did not
employ the central pumping geometry as described by Tesla.
Telsa explained this geometry as necessary to pre-rotate the incoming
fluid, for the purpose of reducing inlet loss.
Commercially available Tesla type pumps have revolutionized the
pumping of difficult fluids and have been documented to achieve higher
pumping efficiencies than conventional bladed type pumps when operated
using high viscosity fluids. This, despite the fact that efficiency has
been compromised in these Tesla type pumps via a drastic increase in
disk spacing and elimination of the central pumping geometry, thereby
allowing the passage of large solids. Texaco documented in 1986, after
the Tesla type pumps had finally became commercially available,
a savings of $68,000 per year, per pump, in comparison to the
conventional bladed type they had replaced.
Prof. Rice also built several experimental turbine models and
achieved ever increasing efficiency as he improved upon his
originally crude models. Prof. Rice's turbine nozzle construction
was not, however, built to the Tesla spec. Even so, Prof. Rice's
final -single stage- version of the Tesla turbine was documented,
using air as the working fluid, of achieving upwards of 36% efficiency.
If the nozzle geometry as employed by Tesla had been used, efficiencies
could have been even higher.
Prof. Rice was also not aware of, and did not use, the numerous
disk support bolts and spacers employed by Tesla. This hardware
is power producing and is absolutely essential for starting torque
and vital for disk stability, without which adhesion can be broken,
allowing friction to manifest.
The bottom line for efficiency is available power in versus available
power out. As such, properly constructed Tesla turbines have been
documented to have a lower steam consumption than comparable bladed
turbines operating in the same class.
Higher efficiency is achieved in bladed turbines of similar size
only by resorting to -multiple- stage configurations.
Conclusions contained in Prof. Rice's final "Tesla Turbomachinery"
paper are, over all, quite positive. It is also acknowledged in
this final 1990 paper that experimentation with turbines, strictly
constructed to the original Tesla design had not been done by him.
He also expressed dismay that much of the work being done by others
was being kept secret and was unavailable.
Prof. Rice's final conclusions include:
"Tesla-type Turbomachinery should be considered in applications
in which conventional machines are inadequate. This includes
applications for small shaft power, or the use of very viscous
fluid or of non-Newtonian fluids. There is some reason to believe
that multiple-disk turbomachines can operate with abrasive two-phase
flow mixtures with less erosion of material from the rotor.
For that reason they should be further investigated for applications
to produce power from geothermal steam and particle laden industrial
gas flows. There may also be unique applications possible using
ceramic disks. There is considerable evidence that multiple disk
turbomachinery can be quieter in operation than is conventional
machinery and that the noise produced is more nearly "white" noise
without a prevailing sound signature. Multiple-disk pumps are
well-known to resist cavitation."
It should be noted that one of Tesla's main promotions for
his turbine was geothermal heat conversion, which he described as:
"Our Future Motive Power."
(C) "All those experimenters who deify Tesla while not knowing
enough math or having the faintest clue how to properly do
decent research."
It is fortunate that Professor Rice used only compressed air as
working fluid in his experimental disk turbines. If steam was employed
he would have experienced efficiencies of much less than 1% using his
construction techniques. The most recent issue of TEBA NEWS (#14)
documents how the Tesla turbine should be constructed for efficient
steam operation.
Respect for Tesla's original work has again been proven the key.
A fully functional Tesla steam turbine test stand can be seen at:
http://execpc.com/~teba/images/tesla7.jpg
The real benefit for the experimenter, and why the Tesla Engine
Builders Association (TEBA) has been possible, is literally Professor
Rice's final word on the subject in his final 1990 presentation:
"It is the ONLY type of turbomachinery that can be easily constructed in
a relatively primitive machine shop." Emphasis ours.
Tesla Engine Builders Association Inc. (TEBA)
http://www.execpc.com/~teba
Permission is hereby granted to copy and distribute this document
in full provided content is not modified.
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Harbin Osteen
Does this guy have a web page?
te...@execpc.com wrote:
>
>
> Respect for Tesla's original work has again been proven the key.
> A fully functional Tesla steam turbine test stand can be seen at:
> http://execpc.com/~teba/images/tesla7.jpg
>
>
--
SeeYaa:) Harbin Osteen
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