> Paul
>
> Have you seen this?
>
> http://www.wipo.int/pctdb/en/wo.jsp?wo=2004074655
>
> Erik Wahlstrom
>
> Very interesting but so far I don't understand exactly what it is
they > are trying to do and I am not a lawyer let alone a patent
lawyer :) Combining a > Wankel rotary with a turbine is a good idea
no matter how they go about it.
>
> However there must be something beyond that I don't understand
or they
> would never get a patent.
>
> The dwg's are not too clear. Too bad they don't allow 3D's in
patents.
>
> Paul Lamar
This is astonishing! It is obviously an attempt to patent the
conceptual framework of a turbo-compound engine. Their "gas
turbine" is
a turbocharger and the wording about the "fixed pressure ratio"
element
is so cleverly ambiguous that it could be any Otto cycle engine. This
reminds me of the "Look and Feel" patents that Apple once heaped
claims
upon.
I could go on forever about this topic. But, I'll just comment
that it
is sad, for me, to see American giants of engineering innovation like
Pratt & Whitney resorting to this sort of activity to generate
revenue.
Aubrey Thompson
It looks like the patent office will give a patent to anybody
for anything and let it be fought out in the courts making the
lawyers rich. This one should be pretty easy to shoot down.
Paul Lamar
Well, this is just a patent application. I haven't read it in
detail, but if you look at the preliminary report on patentability, it
doesn't look very positive.
Bob W.
Paul,
I think this work is a theoretical study similar to the NASA studies we
have discussed before. They are "sweeping" the rotary engine
compression ratio through a range from 1.2 to 5 in the calculations to
get an overall compression ratio of about 7 to 50. So, from the graph
you can see that to stay below the auto-ignition zone without an
inter-cooler, the overall pressure ratio must be less than about
(2.6)(6) = 15.6 or about (3.8)(4) = 15.2. Hasn't this been known by
hot rodders for at least 50 years? The "new art" that the patent
application claims seems to be the discovery of this Auto Ignition
Zone. I find it curious that, as in the NASA studies, single stage
turbochargers operating at pressure ratios of 6 are assumed to be
readily available.
Aubrey Thompson
What do you mean by a pressure ratio. Lets say it is 6. Does that mean
the pressure in the combustion chamber prior to ignition is 6 X Atmos.?
Are my red and blue chart modifications correct?
Paul Lamar ...No rotor no motor.
Paul,
I think the horizontal axis depicts the combustion chamber pressure
prior to ignition. According to the text, it is the product of the
turbine pressure ratio and the volumetric compression ratio of the
rotary engine raised to the 1.3 power. The origin of this equation is
not explained. Presumably the exponent of 1.3 is a result of
temperature rise during the compression motion. So, your red additions
seem about right. By the normal definition of "boost", it would be the
manifold gauge pressure produced by the turbine. In this case that
would be fixed at either a pressure ratio of 4 (boost of 45 psi) or a
pressure ratio of 6 (boost of 75 psi).
Aubrey Thompson
That is what I was guessing. Notice the little numbers on the
graph such as 1.2, 1.5, 2, 3, 4 and 5 those look like turbo charger
compressor
pressure ratios. They need to state the compression ratio of the Wankel
as well. Nothing other than 9.5:1 to 10:1 are practical anyway.
> Paul Lamar
Paul,
These curves were obtained by doing their calculations for a range of
rotary engine compression ratios. Thus the curves represent the
calculated result as the compression ratio changes from about 1.2 to
5.0. Those numbers along the curves are the particular points where the
rotary engine compression ratio has that value. The crux of their
patent claim is that they have discovered the efficiency curves shown in
figure 5 and these curves indicate that there is a unique point of peak
efficiency when a very low compression ratio rotary engine is turbo
compounded with high boost pressure.
Aubrey Thompson
OK I think I see. Those are very low compression ratios indeed for a Wankel.
That will probably take very unusual Wankel geometry indeed. It may be impractical
to build a rotary engine with such low compression ratios and high leaning
angles. The leaning angle is the angle the apex seal makes with the wear
surface and it is critical to the effective functioning of the apex seal.
I notice the thermal eff. between best and worse is 46% as opposed to 44%.
At a doable compression ratio of 5 with inter-cooler it is 44%.
I would settle for 44% thermal eff. any day compared to the current Mazda Wankel
of 28% or below.
To put this into perspective the hwy MPG of an RX8 would go from the current
25 MPG to 37.5 MPG if my assumptions, my arithmetic and this patent
are correct.
Now somebody needs to build the hardware to prove or disprove it.
Note the results CW achieved with actual piston engine hardware, as far
as compression ratio is concerned, are in conflict with this patent.
Paul Lamar ...No rotor no motor.
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