UNITED STATES PATENT AND TRADEMARK OFFICE
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`BEFORE THE PATENT TRIAL AND APPEAL BOARD
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`GENERAL ELECTRIC COMPANY,
`Petitioner,
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`v.
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`UNITED TECHNOLOGIES CORPORATION,
`Patent Owner
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`DECLARATION OF DR. ZOLTÁN S. SPAKOVSZKY
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`Case IPR2016-00526
`Patent No. 7,966,807
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`UTC-2017.001
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`GE v. UTC
`Trial IPR2016-00526
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`
`
`
`BEFORE THE PATENT TRIAL AND APPEAL BOARD
`
`
`
`
`
`
`GENERAL ELECTRIC COMPANY,
`Petitioner,
`
`v.
`
`UNITED TECHNOLOGIES CORPORATION,
`Patent Owner
`
`
`
`
`
`DECLARATION OF DR. ZOLTÁN S. SPAKOVSZKY
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`
`
`
`
`
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`Case IPR2016-00526
`Patent No. 7,966,807
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`
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`
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`UTC-2017.001
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`GE v. UTC
`Trial IPR2016-00526
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`
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`I, Zoltán S. Spakovszky, declare as follows:
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`Case No. IPR2016-00526
`Declaration of Dr. Zoltán S. Spakovszky
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`Introduction
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`I.
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`1.
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`I have been retained by United Technologies Corporation (“Patent
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`Owner”) as an independent expert consultant in this proceeding before the United
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`States Patent and Trademark Office. I understand that this proceeding involves U.S.
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`Patent No. 7,966,807 B2 (“the ’807 patent”) (GE-1001)1, the application for which
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`was filed on January 17, 2007, as U.S. Patent Application No. 11/654,472, and
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`issued on June 28, 2011.
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`2.
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`All of the opinions contained in this Declaration are based on the
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`documents I reviewed and my knowledge and professional judgment. In forming
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`the opinions expressed in this Declaration, I reviewed the ’807 patent, the
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`Declaration provided by Dr. Magdy Attia (GE-1003), the other Exhibits cited by
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`the Petitioner, and the other materials cited in this declaration. I have also drawn
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`on my experience and knowledge of gas-turbine engines.
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`3. My opinions have been also guided by my appreciation of how a
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`person of ordinary skill in the art would have understood the claims of the ’807
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`1 Where appropriate, I refer to exhibits attached to the petition for Inter Partes
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`Review of the ’807 patent.
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`patent at the time of the invention, which I have been asked to assume as
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`January 17, 2007, the filing date of the ’472 application.
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`4.
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`Based on my analysis, it is my opinion that the Young and McGarry
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`references relied on by Dr. Attia do not disclose or suggest all of the features
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`recited in the claims of the ’807 patent. In particular, neither Young nor McGarry
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`discloses or suggests a vapor cooling assembly associated with a non-rotating
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`component extending into a “turbine flowpath.” And it would not have been
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`obvious to modify either reference to include this feature given the technical
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`problems that would have resulted. Young and McGarry also fail to disclose the
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`“flow guide” of claims 15-20 that “direct[s] . . . air toward the condenser section of
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`the vapor cooling assembly.” Therefore, I disagree with Dr. Attia’s obviousness
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`conclusions.
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`II. Qualifications
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`5.
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` I am currently a professor of Aeronautics and Astronautics at the
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`Massachusetts Institute of Technology (“MIT”) and I have served in this position
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`since 2012. I have also served as the Vehicle Sector Head in the Department of
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`Aeronautics and Astronautics at MIT since 2015. I have also been the director of
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`the MIT Gas Turbine Laboratory since 2008.
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`6.
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`I was an Associate Professor of Aeronautics and Astronautics at MIT
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`from 2005-2012, and Assistant Professor of Aeronautics and Astronautics at MIT
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`from 2001-2005. I teach courses relating to thermodynamics and energy
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`conversion, propulsion and fluid mechanics, and aero-acoustics.
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`7.
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`I received a Ph.D. in Aeronautics and Astronautics from MIT in 2000,
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`an M.S. in Aeronautics and Astronautics from MIT in 1999, and a Diplom
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`Ingenieur in Mechanical Engineering from ETH in Zurich, Switzerland in 1997.
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`8.
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`I have authored over 40 peer reviewed journal and over 50 conference
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`papers related to gas turbine engines and propulsion systems. I am also a named
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`inventor on two U.S. patents relating to turbomachinery or the components thereof.
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`9.
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`I have served in a number of organizations related to gas turbine
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`engines and turbomachinery. For example, I am currently the review chair for the
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`American Society of Mechanical Engineers (ASME) International Gas Turbine
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`Institute (IGTI) Turbo Expo and Conference. I previously served as chair of the
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`ASME IGTI Turbomachinery Committee, and as an Associate Editor of the ASME
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`Journal of Turbomachinery. In addition, I am a Fellow in the ASME, and an
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`Associate Fellow in the American Institute of Aeronautics and Astronautics
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`(AIAA).
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`10.
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`I have received awards for a number of my publications, including
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`best paper award in 2014 from the ASME IGTI Aircraft Engine Committee, best
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`paper awards in 2000, 2002, 2006, 2007, 2011, and 2012 from the ASME IGTI
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`Turbomachinery Committee, and a best paper award in 2000 from the ASME IGTI,
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`Structures & Dynamics Committee. My research in gas turbine engines has also
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`been recognized by my peers and resulted in awards, including, the ASME Gas
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`Turbine Award in 2012.
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`11.
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`I have also received several teaching awards including the Ruth and
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`Joel Spira Award for Excellence in Teaching in 2009, and the Aero-Astro
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`Undergraduate Teaching Award in 2008.
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`12. My curriculum vitae, which includes a detailed summary of my
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`background and experience is provided as Exhibit UTC-2010.
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`III. Legal Standards
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`13.
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`I understand that Dr. Magdy Attia and Petitioner argue that the claims
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`of the ’807 patent are obvious. See generally Petition; GE-1003. Regarding
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`obviousness, counsel has informed me that a patent claim is unpatentable if the
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`differences between the claimed invention and the prior art are such that the
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`claimed invention as a whole would have been obvious before the effective filing
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`date of the claimed invention to a person having ordinary skill in the art. In this
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`proceeding, I have used the filing date of the ’472 application as the time of the
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`invention for my analysis.
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`14. The claimed subject matter as a whole must be considered when
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`determining obviousness. Additionally, I understand that this obviousness analysis
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`takes into account the scope and content of the prior art, the differences between
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`the claimed subject matter and the prior art, and the level of ordinary skill in the art
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`at the time of the invention. I understand that the burden of establishing the
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`obviousness of the claimed invention rests on the Petitioner and Dr. Attia, and
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`therefore, for purposes of my obviousness analysis, I have used the level of
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`ordinary skill in the art as defined by Dr. Attia. See GE-1003, ¶ 4. I understand that
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`the proponent of an obviousness challenge must provide clear reasoning showing
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`why the claimed subject matter would have been obvious to a person of ordinary
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`skill in the art at the time of the invention.
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`15.
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`I understand that multiple prior art references or teachings can be
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`combined to show that a patent claim would have been obvious. When taking this
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`approach, I understand that the proponent of obviousness must show that a person
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`of ordinary skill in the art would have had reason or motivation to combine the
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`references in the way the elements are recited in the claim.
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`IV. The ’807 Patent
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`16. The ’807 patent discloses a novel method of cooling the non-rotating
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`structures in the turbine section of a gas turbine engine. ’807 patent, Abstract,
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`1:41-44 (also cited as GE-1001). The ’807 patent uses a vapor cooling assembly to
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`extract heat from the non-rotating components in the turbine section of the turbine
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`engine and transfer the heat to a relatively cooler bypass duct. ’807 patent, 1:44-56.
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`The heat transferred to the bypass duct is recovered in the form of additional thrust
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`generated by the engine. ’807 patent, 1:57-58.
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`17.
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`The ’807 patent discloses a gas turbine engine that has a fan
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`section 12, low-pressure and high—pressure compressor sections 14, 16, combustor
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`section 18, high—pressure and low-pressure turbine sections 20, 22, and a bypass
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`fan duct 24- ’807 patent, 1:65-2:1- I have reproduced below an annotated version
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`of Fig. 1 of the ’807 patent to illustrate these features.
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`Fan
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`18-
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`In the above figure, the compressor sections are shown in green, the
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`turbine sections are shown in red, and the combustor section, located in between
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`the compressor and turbine sections, is shown in yellow.
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`Declaration of Dr. Zoltén S. Spakovszky
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`A.
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`Flowpaths
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`19.
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`The ’807 patent also discloses two primary flowpaths. A flowpath is a
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`path through which air and/or combustion gases flow. The two flowpaths disclosed
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`by the ’807 patent, namely the engine/gas flowpath and the bypass flowpath are
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`illustrated, in an annotated version of Fig. 1 of the ’807 patent below.
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`10
`\
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`_
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`fin14
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`FIG. 1
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`20. As illustrated in the above figure, fan 12 forces air into both the
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`engine/gas flowpath shown in yellow, and into the bypass flowpath shown in blue.
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`Air flowing through the bypass flowpath is separate from the air that enters the
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`engine/gas flowpath. Air in the bypass flowpath does not pass through the
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`compressor sections, the combustor, or the turbine sections. ’807 patent, 2: 15-16.
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`21. The ratio of the mass flow rate of air in the bypass flowpath to the
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`mass flow rate of air in the engine/gas flowpath is termed the “bypass ratio.” See
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`GE-1014.028 (Problem 1-5). Mass flow rate of air refers to the mass of air flowing
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`through a passageway per unit time. The mass flow rate of air at a particular
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`location in the bypass flowpath may be written as (ρ V Ac), where ρ is the density
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`of air at that location, V is the velocity of the air at that location, and Ac is the
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`cross-sectional area of the bypass flowpath at that location. Frank P. Incropera &
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`David P. DeWitt, Introduction to Heat Transfer (4th ed., John Wiley & Sons 1996)
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`(UTC-2011.009).
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`22. Compressors 14 and 16 increase the pressure of the air flowing in the
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`engine/gas flowpath. See GE-1014.049. The compressed air enters combustor 18
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`where it is mixed with fuel. Combustion of the fuel in combustor 18 releases heat,
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`which significantly increases the temperature of the combustion gases leaving the
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`combustor. See GE-1014.051.
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`23. After leaving the combustor, the flow passes into the high-pressure
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`and low-pressure turbine sections 20, 22. A “turbine” is a device that has rotatable
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`blades located in a fluid passageway that changes the angular momentum flux of
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`the fluid flow and converts it into shaft power. The high-pressure and low-pressure
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`turbine sections 20, 22 each include rings of rotatable turbine blades axially
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`separated from each other. See ’807 patent, Fig. 1; see also GE-1014.052. Turbine
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`sections 20, 22 also include non-rotating vanes located between adjacent rings of
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`rotatable turbine blades. See ’807 patent, Fig. 1; see also GE-1014.052.
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`24. The high temperature and high pressure combustion gas from the
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`combustor expands over the turbine sections to create shaft work. See
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`GE-1014.051. In particular, the hot combustion gases expand as they pass through
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`the turbine section, causing the rotatable turbine blades in turbine sections 20, 22 to
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`rotate. See GE-1014.051-.053. After passing through the turbine sections, the
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`combustion gases exit the engine through a nozzle in the engine/gas flowpath,
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`creating thrust. See GE-1014.054. The rotating turbine blades in the high pressure
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`turbine section 20 rotate the high pressure compressor 16 via a shaft. See
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`GE-1014.063. The rotating turbine blades in the low pressure turbine section 22
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`rotate the fan 12 and the low pressure compressor 14 via a shaft. See GE-1014.063.
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`Rotation of the fan forces air to flow through both the engine/gas flowpath and the
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`bypass flowpath. See e.g. GE-1014.021. The flow of air through the bypass
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`passage and out of the bypass nozzle also creates thrust.
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`25.
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`It is well known that turbines experience high temperatures. The gas
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`temperatures in the turbine can reach 3,000° F (see ’807 patent, 3:22-25), and at
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`these high temperatures the materials used in the turbine components can melt. The
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`performance of the materials may also degrade due to exposure to the high gas
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`temperatures.
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`26. Traditional approaches for operating turbine components efficiently at
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`high temperatures and pressures while maintaining a relatively long lifespan
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`include manufacturing
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`them from advanced materials, applying specially
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`engineered thermal barrier coatings, or diverting relatively cooler air from the
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`compressor to flow over the turbine components. ’807 patent, 1:8-9, 4:10. These
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`approaches can add cost, complexity, and weight to the engine, or reduce the
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`engine’s overall efficiency.
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`27. To maintain turbine component temperatures within operational limits,
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`the ’807 patent uses a specially-positioned and configured vapor cooling assembly
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`26. ’807 patent, 2:9-15. The vapor cooling assembly provides “improved cooling
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`capabilities for gas turbine engines, in order to better maintain engine components
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`at temperatures below designated maximum operating temperature levels.” ’807
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`patent, 1:13-15. The vapor cooling assembly includes a vaporization section 34 and
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`a condenser section 36. ’807 patent, 2:30-32. The condenser section is located at
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`least partially in the bypass flowpath. ’807 patent, 2:33-34. The vaporization
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`section is located in a non-rotating component, such as a strut or vane 32. ’807
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`patent, 2:24-32. The ’807 patent disclosure, including combined Figures 1 and 2
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`below and the related text, disclose that the vapor cooling assembly 26 is located in
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`the turbine section of the engine.
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`FIG. 1
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`B.
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`Interpretation of the claim term “turbine flowpath”
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`28.
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`Claims 4 and 8 recite a “turbine flowpath.” As I explain above, the
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`components of a gas turbine engine are typically divided into a number of sections.
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`The ’807 patent follows this standard practice and differentiates the “turbine
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`section”—which may comprise a high—pressure turbine section and a loW—pressure
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`turbine section—from other sections in the engine, such as the “fan section,” the
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`“compressor section,” and the “combustor section.” ’807 patent, 1:64-2:1.
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`29. The ’807 patent also describes
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`the
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`flowpaths
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`through
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`these
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`components in terms of sections. One of these sections of flowpath in the ’807
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`patent is the “turbine flowpath.” ’807 patent, 1:41-45. A “flowpath” is a path of
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`flow of air or other gases.
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`30. Given its plain language, it would have been clear to an ordinarily
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`skilled artisan that a “turbine flowpath” is located within the “turbine.” As I
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`discussed above, a turbine is a device that includes rotatable blades separated by
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`non-rotating vanes. See GE-1014.052, GE1014.070. The rotating blades and the
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`non-rotating vanes of the turbine are located in the path of flow of combustion
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`gases. See GE-1014.052, GE1014.070. The high pressure and high temperature
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`combustion gas expands over the turbine blades creating shaft work. See
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`GE-1014.051. Thus, the term “turbine flowpath” refers to the section of the turbine
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`through which combustion gases flow.
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`31. Publications from manufacturers of gas turbine engines (e.g. GE and
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`Rolls Royce) illustrate that the term “turbine flowpath” commonly refers to the
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`portion of a turbine where the combustion gases flow. For example, U.S. Patent No.
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`6,547,518 assigned to the General Electric Company discloses an engine in which
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`“[t]urbine blades 20 radially extend across a turbine flowpath 22 which encloses a
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`hot working gas flow 26 in the turbine section 10.” UTC-2012, 3:6-7.
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`32.
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`I understand that in the Institution Decision, the Board interpreted
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`“turbine flowpath” as covering all sections of the engine/gas flowpath downstream
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`of the combustor. I disagree with the Board’s interpretation because it
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`encompasses portions of the engine/gas flowpath that are not in the turbine section,
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`but that lie upstream and downstream of the turbine.
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`33. As I explained above,
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`the engine/gas flowpath
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`includes an
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`exhaust/nozzle section downstream of the turbine section. Combustion gases
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`leaving the turbine section pass through the nozzle section to generate thrust.
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`Similarly, there is a section of the engine/gas flowpath, located between the
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`combustor and the turbine flowpath, upstream of the turbine sections. This section
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`directs the combustion gases leaving the combustor to flow to the turbine section.
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`34. The sections of the engine/gas flowpath upstream and downstream of
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`the turbine sections, however, are not considered part of the “turbine flowpath.”
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`Practitioners in the field of gas turbine engines refer to the portion of the turbine
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`through which combustion gases flow (e.g. the bladed region of turbine) as the
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`turbine flowpath. The section of the engine/gas flowpath between the combustor
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`and the turbine section, and the section of the engine/gas flowpath between the
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`turbine section and the nozzle section are separate and distinct from the turbine
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`flowpath. Thus, the term “turbine flowpath” refers to the portion of the turbine
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`through which combustion gases flow.
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`V. The Cited References and Arguments Regarding Obviousness
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`35. Petitioner and Dr. Attia have cited two references, Young and
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`McGarry, in their arguments about the claims of the ’807 patent. See generally
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`Petition, GE-1003. Young discloses a heat exchanger located downstream from the
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`last stage of the turbine. McGarry discloses an integral heat pipe and vane located
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`in the compressor section upstream of the turbine section. Thus, neither Young nor
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`McGarry discloses a heat exchanger disposed in the turbine section of the gas
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`turbine engine.
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`36. Dr. Attia has argued that it would have been obvious to move
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`Young’s heat exchanger upstream into the turbine section. Regarding McGarry, he
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`has argued that it would have been obvious to place a heat pipe downstream in
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`McGarry’s turbine section. GE-1003, ¶¶ 79-83. Both of these arguments are
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`incorrect. As an initial matter, I have never seen the technology relied upon by Dr.
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`Attia (i.e., heat pipes in a turbine section) used in a production aircraft engine. In
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`addition to this general evidence of nonobviousness, Dr. Attia’s combination
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`would transfer heat away from the combustion gases in the turbine section, which
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`could significantly alter the thermodynamic cycle and therefore degrade the thrust
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`produced by the engine. Dr. Attia fails to account for this and other technical
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`problems that would have dissuaded an ordinarily skilled artisan from making his
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`proposed changes to Young and McGarry. Below, I address Dr. Attia’s arguments
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`regarding Young and McGarry in turn.
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`A. Young
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`37. Dr. Attia first argues that the ’807 claims would have been obvious in
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`view of Young. See, e.g., GE-1003 ¶¶ 55-96. Below I explain Young’s disclosure
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`and then address why Dr. Attia’s modification of Young would defeat Young’s
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`goal of using waste heat.
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`1.
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`Disclosure of Young
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`38. Young proposes to improve the thrust of a gas turbine engine by
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`transferring waste heat from combustion gases downstream of the last turbine stage
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`to the bypass duct. GE-1005.001. Young proposes to use a heat exchanger for this
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`heat transfer. GE-1005.001.
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`39. Young recognizes the disadvantages of removing too much heat from
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`the turbine sections. For example, Young discloses a configuration in which a heat
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`pipe is used to connect hot turbine vanes to vanes at the discharge end of the high
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`pressure compressor. GE-1005.003, lines 49-52. Young notes that doing so adds
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`heat to the combustion system, reducing the amount of fuel required by the engine.
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`GE-1005.003, lines 52-55. But, Young also states that the “amount of heat which
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`can be taken from the vanes is limited, however, to avoid cooling the working fluid
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`flowing through the vanes, because this would adversely affect the efficiency of
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`the downstream stages of the turbine.” GE-1005.003, lines 55-60.
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`40. To better understand Young’s cautionary statement, one must
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`recognize that the thrust in a by-pass or turbofan engine of the type disclosed by
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`Young is primarily generated in the bypass flowpath by the fan. But the fan itself is
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`rotated by the rotating blades of the low-pressure turbine. GE-1014.021.
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`41. The amount of work that can be extracted from the combustion gases
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`flowing through the turbine is directly related to the temperature of the combustion
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`gases in the turbine. GE1015.056-.057. This means that if the temperature of the
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`combustion gases entering the turbine is lowered, less work can be extracted from
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`the turbine for a given flow rate of combustion gases through the turbine. Because
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`the fan is driven by the low-pressure turbine, a reduction in the amount of work
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`extracted from the turbine would reduce the thrust generated by the fan.
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`42. To avoid these disadvantageous effects, Young proposes to transfer
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`heat from the hot turbine exhaust downstream of the last turbine stage, and put it
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`into the fan exhaust. GE-1005.003, lines 63-66. Young proposes to do so with the
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`help of a heat exchanger in the form of interconnected vanes 24, 26 that span both
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`the bypass duct 16 and the jet pipe 20 (sometimes referred to as the “exhaust duct”)
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`of the core engine. GE-1005.003, Abstract. Young’s arrangement is illustrated in
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`the annotated version of Fig. 1 of Young excerpted below.
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` Compressor
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`‘ll.
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`43. One of ordinary skill
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`in the art would recognize that once the
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`combustion gases exit the last stage of the turbine, no further work is extracted
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`from those gases. In other words, the enthalpy of the combustion gases leaving the
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`last stage of the turbine comprises kinetic energy and waste heat- Young reiterates
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`its focus on “waste heat” when it explains positioning the vanes “downstream of
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`the last stage of the turbine to pick—up heat, which is at this stage waste heat, from
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`the jet pipe.” GE-1005.004, lines 20-23 (emphasis added)- The vanes put this waste
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`heat from the jet pipe “into the bypass air to raise its temperature.” GE—l005.004,
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`lines 24-28. By locating the vanes “downstream of the last turbine stage,” where
`
`the heat would otherwise be wasted, Young teaches that its engine generates
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`17
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`UTC-2017.018
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`Case No. IPR2016-00526
`Declaration of Dr. Zoltán S. Spakovszky
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`additional thrust without removing heat from the turbine. GE-1005.004, lines 20-
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`23.
`
`44. Enthalpy is a thermodynamic state variable that represents the total
`
`energy content of a system and equals the internal energy of the system plus the
`
`flow work, which is the product of pressure and volume of the system. See Jack D.
`
`Mattingly, Elements of Propulsion Gas Turbines and Rockets (AIAA 2006) (UTC-
`
`2014.016). In Young’s arrangement, heat from the combustion gases is transferred
`
`to vane 26, which transfers heat to vane 24. GE-1005.004, lines 19-28. Heat from
`
`vane 24 is transferred to the air flowing in the bypass duct, thereby heating the air
`
`in the bypass duct. GE-1005.004, lines 26-28. This in turn increases the kinetic
`
`energy of the air in the bypass duct and generates additional thrust.
`
`2. Moving Young’s heat exchanger upstream would disrupt
`Young’s Brayton cycle and could decrease thrust rather
`than increase it
`
`45.
`
`I understand that Dr. Attia has argued that it would have been obvious
`
`to modify Young by moving its heat exchanger from the exhaust section of the
`
`engine to the turbine section. GE-1003 at ¶¶ 79-83. This is incorrect.
`
`46. The goal of a propulsion system (e.g. a turbofan engine) is to convert
`
`chemical energy stored in the fuel (e.g., heat) into propulsive power. The
`
`propulsion system includes an engine (e.g., the gas turbine heat engine) and a
`
`propulsor (e.g., the fan). The engine (e.g., the gas turbine heat engine) converts
`
`
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`18
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`UTC-2017.019
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`Case No. IPR2016-00526
`Declaration of Dr. Zoltán S. Spakovszky
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`heat into mechanical shaft work. See e.g. GE-1014.021. The thermal efficiency
`
`“ηT” indicates how well the heat released by combustion of the fuel is converted
`
`into mechanical shaft work. See GE-1014.057.
`
`47. For ideal cycles, thermal efficiency, ηT, depends on the ratio of two
`
`temperatures: (1) the average temperature, TR, at which heat is rejected in the cycle,
`
`and (2) the average temperature, TA, at which heat is absorbed in the cycle. Highest
`
`thermal efficiency is achieved if the average temperatures during heat exchange are
`
`the minimum and maximum temperatures in the cycle (i.e., Carnot cycle, ηT = 1 -
`
`(Tmin/Tmax)). For an ideal Brayton cycle, thermal efficiency ηT = 1 - (TR/TA). See
`
`e.g. GE-1014.057.
`
`48. The propulsor (e.g., the fan of the turbofan engine) takes the shaft
`
`power from the turbine and converts it into propulsive power. The metric to
`
`measure the conversion of shaft power into propulsive power is propulsive
`
`efficiency “ηP,” which indicates how well the shaft power is converted into
`
`propulsive power. GE-1014.058. The overall efficiency “η” of the engine is the
`
`product of the thermal efficiency and the propulsive efficiency (i.e. η = ηT x ηP).
`
`UTC-2014.010.
`
`49. The overall efficiency, η, is a measure of how well the propulsion
`
`system (e.g., the turbofan engine) converts heat released by combustions of the fuel
`
`
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`19
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`UTC-2017.020
`
`
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`Case No. IPR2016-00526
`Declaration of Dr. Zoltán S. Spakovszky
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`into propulsive work. Overall efficiency is inversely proportional to thrust-
`
`specific-fuel-consumption, which represents the amount of fuel required to
`
`generate a unit of thrust. See UTC-2014.006, .012. In other words, if the overall
`
`efficiency is high, the thrust-specific-fuel-consumption is low, meaning that less
`
`fuel is required to generate every pound of thrust. Thus, to reduce fuel
`
`consumption, both thermal efficiency and propulsive efficiency must be high so
`
`that the overall efficiency is also high.
`
`50. Moving Young’s heat pipe into the turbine section would remove heat
`
`from the combustion gases before the turbine could extract shaft work from the
`
`combustion gases. Removing heat from the combustion gases would cool the
`
`combustion gases entering the turbine sections. In other words, the average
`
`temperature at which heat is absorbed in the cycle, TA, would be lowered. Because
`
`ηT = 1 - (TR/TA), reducing TA would reduce the thermal efficiency, ηT
`
`51. A reduction in the thermal efficiency would decrease the overall
`
`efficiency of the engine unless the propulsive efficiency increases sufficiently to
`
`offset the reduction in thermal efficiency. Determining whether the propulsive
`
`efficiency can offset the loss of thermal efficiency would have involved a careful
`
`analysis of the thermodynamic and mechanical aspects of the engine. Thus, one of
`
`ordinary skill in the art would not have been motivated to move Young’s heat
`
`exchanger into the turbine section because it would not have guaranteed an
`
`
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`20
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`UTC-2017.021
`
`
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`Case No. IPR2016-00526
`Declaration of Dr. Zoltán S. Spakovszky
`
`increase in the overall efficiency. Quite the contrary, one of ordinary skill in the art
`
`would have recognized that moving Young’s heat pipe into the turbine section may
`
`reduce the overall efficiency. This is because Young already achieved some thrust
`
`benefit without reducing TA. It did so by placing its heat exchanger downstream of
`
`the turbine.
`
`52. Another way to understand the effect of moving Young’s heat pipe is
`
`in terms of the thrust generated by the engine. Consider Young’s engine without
`
`the heat exchanger disclosed by Young. In this case, the combustion gases flowing
`
`through jet pipe 20 would generate a first thrust component F1. See GE-1014.028
`
`(Problem 1-5). Similarly, the air flowing through the bypass duct 16 would
`
`generate a second thrust component F2 (see GE-1014. 028, problem 1-5),
`
`producing a total engine thrust of F1 + F2, which I will denote as F. See
`
`GE-1014.059, Eq. 5-93.
`
`53. Now consider the same engine but with the heat exchanger disclosed
`
`by Young. By transferring heat from the combustion gases exiting the last turbine
`
`stage to the bypass duct, Young’s heat exchanger generates an additional amount
`
`of thrust, which I will denote as. “∆F.” GE-1005.001, Abstract. One of ordinary
`
`skill in the art would have understood that Young generates the additional thrust
`
`∆F, without substantially altering the thrust F already being generated by the
`
`engine. By placing the heat exchanger downstream of the last turbine stage,
`
`
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`21
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`UTC-2017.022
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`
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`Case No. IPR2016-00526
`Declaration of Dr. Zoltán S. Spakovszky
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`Young’s arrangement produces a thrust F + ∆F, which is more than the thrust F
`
`produced by the engine in the absence of Young’s heat exchanger. Thus, one of
`
`ordinary skill in the art would have understood that Young’s technique aims to
`
`generate additional thrust by recovering some of the heat that would have
`
`otherwise been wasted. However, Young achieves this without reducing the
`
`amount of heat available to the turbine for extracting work, which is used to drive
`
`the fan.
`
`54.
`
`If one were to move Young’s heat exchanger upstream into the
`
`turbine stages, the combustion gases flowing through the turbine would be cooled
`
`by that heat exchanger. As I discussed earlier, as the temperature of the combustion
`
`gases decreases, so does the amount of work that can be extracted by the turbine.
`
`In other words, there would be less energy available to spin the turbine wheel and
`
`therefore to spin the fan. This in turn would reduce the amount of thrust being
`
`generated by the fan.
`
`55.
`
`I will denote as “∆FLoss” the loss of thrust from the fan caused due to
`
`cooling of the combustion gases in the turbine. As discussed above, the heat
`
`transferred into the bypass duct would cause an increase in the thrust generated in
`
`the bypass duct. I will denote the increased thrust generated in the bypass duct as
`
`“∆FGain.” The total thrust generated by Young’s engine with a heat exchanger in the
`
`turbine section would then be F - ∆FLoss + ∆FGain, where F is the thrust generated by
`
`
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`22
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`UTC-2017.023
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`
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`Case No. IPR2016-00526
`Declaration of Dr. Zoltán S. Spakovszky
`
`the engine in the absence of any heat exchanger. One of ordinary skill in the art
`
`would recognize that when ∆FLoss exceeds ∆FGain, the total thrust generated by the
`
`engine with a heat exchanger in the turbine sections would in fact be lower than in
`
`an engine with no heat exchanger at all.
`
`56. Young does not contemplate removing heat from the turbine and does
`
`not suggest moving its heat pipe into the turbine. Instead, Young repeatedly refers
`
`to “waste heat,” which is not capable of driving a turbine because it is heat that
`
`remains in the combustion gases after they exit the last turbine stage. Young
`
`proposes simply to recover heat that would otherwise have been rejected to the
`
`ambient (i.e. wasted). By transferring some of this waste heat to the bypass duct,
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`Young’s engine generates thrust F + ∆F, which would be higher than the thrust F
`
`generated by the engine without Young’s heat exchanger.
`
`57. Given
`
`the complexities
`
`involved with moving Young’s heat
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`exchanger to the turbine section, and the likelihood that such a move could in fact
`
`lower the thrust generated by the engine, it is my opinion that one of ordinary skill
`
`in the art would not have been motivated to move Young’s heat exchange
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