Prosecution Insights
Last updated: April 18, 2026
Application No. 18/736,704

COMBUSTOR SIZE RATING FOR A GAS TURBINE ENGINE USING HYDROGEN FUEL

Final Rejection §103§112
Filed
Jun 07, 2024
Examiner
SUNG, GERALD LUTHER
Art Unit
3741
Tech Center
3700 — Mechanical Engineering & Manufacturing
Assignee
General Electric Company
OA Round
2 (Final)
80%
Grant Probability
Favorable
3-4
OA Rounds
3y 5m
To Grant
99%
With Interview

Examiner Intelligence

Grants 80% — above average
80%
Career Allow Rate
670 granted / 842 resolved
+9.6% vs TC avg
Strong +29% interview lift
Without
With
+28.9%
Interview Lift
resolved cases with interview
Typical timeline
3y 5m
Avg Prosecution
24 currently pending
Career history
866
Total Applications
across all art units

Statute-Specific Performance

§101
0.5%
-39.5% vs TC avg
§103
39.8%
-0.2% vs TC avg
§102
26.4%
-13.6% vs TC avg
§112
28.5%
-11.5% vs TC avg
Black line = Tech Center average estimate • Based on career data from 842 resolved cases

Office Action

§103 §112
DETAILED ACTION Notice of Pre-AIA or AIA Status The present application, filed on or after March 16, 2013, is being examined under the first inventor to file provisions of the AIA . Claim Objections Claim 4 is objected to because of the following informalities: the limitation “the engine centerline” should be “an engine centerline”. Appropriate correction is required. Claim Rejections - 35 USC § 112 The following is a quotation of the first paragraph of 35 U.S.C. 112(a): (a) IN GENERAL.—The specification shall contain a written description of the invention, and of the manner and process of making and using it, in such full, clear, concise, and exact terms as to enable any person skilled in the art to which it pertains, or with which it is most nearly connected, to make and use the same, and shall set forth the best mode contemplated by the inventor or joint inventor of carrying out the invention. The following is a quotation of the first paragraph of pre-AIA 35 U.S.C. 112: The specification shall contain a written description of the invention, and of the manner and process of making and using it, in such full, clear, concise, and exact terms as to enable any person skilled in the art to which it pertains, or with which it is most nearly connected, to make and use the same, and shall set forth the best mode contemplated by the inventor of carrying out his invention. Claims 1-2, 4-5, 7-11, 13-15 and 20-21 are rejected under 35 U.S.C. 112(a) or 35 U.S.C. 112 (pre-AIA ), first paragraph, as failing to comply with the written description requirement. The claim(s) contains subject matter which was not described in the specification in such a way as to reasonably convey to one skilled in the relevant art that the inventor or a joint inventor, or for applications subject to pre-AIA 35 U.S.C. 112, the inventor(s), at the time the application was filed, had possession of the claimed invention. Regarding claim 1, the limitation “a combustor configured to operate with the substantially completely diatomic hydrogen fuel flow, the fuel flow being without diluent… a plurality of openings arranged about the at least one rich cup… a passage extending between a passage inlet and a passage outlet…” is not supported in the original disclosure. The amendment finds support at one location in the specification, para. [0076]. The relevant text of the disclosure states “[w]ith the combustor sized as described in these embodiments, hydrogen fuel can be used without the need of diluents. In some embodiments, no diluent is added to the combustion chamber 430 and the fuel is substantially completely diatomic hydrogen without diluent.” Thus, the specification makes clear that the use of substantially completely diatomic hydrogen without diluent occurs in those embodiments where no diluent is added to the combustion chamber. Thus, the use of hydrogen without diluent is exclusive of the elected embodiment and not disclosed to be consistent with a combustor having at least one set of dilution openings in the dome wall. Claim 13 contains materially similar limitations and is rejected for the same reasons. Claims dependent thereon are rejected for the same reasons. The following is a quotation of 35 U.S.C. 112(b): (b) CONCLUSION.—The specification shall conclude with one or more claims particularly pointing out and distinctly claiming the subject matter which the inventor or a joint inventor regards as the invention. The following is a quotation of 35 U.S.C. 112 (pre-AIA ), second paragraph: The specification shall conclude with one or more claims particularly pointing out and distinctly claiming the subject matter which the applicant regards as his invention. Claim 9 is rejected under 35 U.S.C. 112(b) or 35 U.S.C. 112 (pre-AIA ), second paragraph, as being indefinite for failing to particularly point out and distinctly claim the subject matter which the inventor or a joint inventor (or for applications subject to pre-AIA 35 U.S.C. 112, the applicant), regards as the invention. Regarding claim 9, the limitation “the set of lean cups” renders the claim indefinite because its unclear which set of lean cups is being referred to. Claim Rejections - 35 USC § 103 In the event the determination of the status of the application as subject to AIA 35 U.S.C. 102 and 103 (or as subject to pre-AIA 35 U.S.C. 102 and 103) is incorrect, any correction of the statutory basis (i.e., changing from AIA to pre-AIA ) for the rejection will not be considered a new ground of rejection if the prior art relied upon, and the rationale supporting the rejection, would be the same under either status. The following is a quotation of 35 U.S.C. 103 which forms the basis for all obviousness rejections set forth in this Office action: A patent for a claimed invention may not be obtained, notwithstanding that the claimed invention is not identically disclosed as set forth in section 102, if the differences between the claimed invention and the prior art are such that the claimed invention as a whole would have been obvious before the effective filing date of the claimed invention to a person having ordinary skill in the art to which the claimed invention pertains. Patentability shall not be negated by the manner in which the invention was made. The factual inquiries for establishing a background for determining obviousness under 35 U.S.C. 103 are summarized as follows: 1. Determining the scope and contents of the prior art. 2. Ascertaining the differences between the prior art and the claims at issue. 3. Resolving the level of ordinary skill in the pertinent art. 4. Considering objective evidence present in the application indicating obviousness or nonobviousness. Claim(s) 1-2, 4-5, 7-9, 11, 13-15, 20 is/are rejected under 35 U.S.C. 103 as being unpatentable over Roberts US 5,335,502 in view of Donisi US 2020/0165937, Joshi US 11,578,871, and Berry US 2010/0170253. Regarding claim 1, Roberts discloses a gas turbine engine, see fig. 1, comprising: a fuel delivery assembly 52, 74 configured deliver a fuel flow, ifeul from injector 52; a compressor section 20, 22 configured to compress air flowing therethrough to provide a compressed air flow; and a combustor 24 configured to operate with the substantially completely diatomic hydrogen fuel flow, the fuel flow being without diluent, the combustor is capable of burning hydrogen without diluent, the combustor including an inner liner 60, an outer liner 58, a dome wall 64 having a dome inlet, and a combustion chamber 62, the combustion chamber characterized by a combustor size rating between one inch and seven inches, see col. 6, line 62, col. 7, line 5, at a core air flow parameter, Roberts teaches a turbofan with a bypass that inherently has a core airflow parameter, wherein the combustor size rating is a function of the core air flow parameter, and wherein the combustor size rating is defined by : L2/H wherein H is a maximum height of the combustion chamber measured by a forward line extending form an inner surface of the outer liner to an inner surface of the inner liner, referring to fig. 2, the diameter is taken at the forward end of the combustor as claimed, and L is a length of the combustion chamber measured from a midpoint of the forward line to a midpoint of an aft line, the aft line extending from the inner surface of the inner liner to the inner surface of the outer liner at a leading edge of a turbine nozzle 26, and wherein the core air flow parameter is defined by: Thrust/Bypass Ratio. Roberts does not disclose a hydrogen fuel that comprises a substantially completely hydrogen or a core air flow parameter between two and one half kN and sixty kN, at least one rich cup fluidly coupled to the combustion chamber at the dome inlet, a plurality of openings arranged about the at least one rich cup, and a passage extending between a passage inlet and a passage outlet, the passage outlet defining at least one lean cup in the plurality of openings. Donisi teaches a gas turbine engine similar to that of Roberts and states that GT engines may have any desired maximum thrust from 160-550kN, see para. [0077], and bypass ratios may be any desired ratio form 10-17, see para. [0074]. This results in a core airflow parameter from 9.4-55. It would have been obvious to an ordinary skilled worker to provide a thrust and bypass ratio in the engine of Roberts from between 160-550kN and 10-17, respectively, as taught by Donisi, in order to provide a desired engine characteristic. Supra. Roberts, in view of Donisi, does not disclose a hydrogen fuel that comprises a substantially completely hydrogen. Joshi teaches a similar combustor to Roberts where the engine utilizes hydrogen as a first amount of fuel F1 that is hydrogen and injected into injector 30, see col. 7, lines 5-10. The use of hydrogen allows for reduced combustor volume because there is no length of time need for evaporation, mixing is fast, and reaction rates are high so that length and weight can be reduced by decreasing combustor volume and length. See col. 8, lines 51-57. It would have been obvious to an ordinary skilled worker to provide substantial diatomic hydrogen without diluent in the engine of Roberts, in view of Donisi, as taught by Joshi, in order to provide a smaller lighter engine. Id. Roberts, in view of Donisi and Joshi, does not disclose at least one rich cup fluidly coupled to the combustion chamber at the dome inlet, a plurality of openings arranged about the at least one rich cup, and a passage extending between a passage inlet and a passage outlet, the passage outlet defining at least one lean cup in the plurality of openings. Roberts does teach a plurality of circumferentially spaced injectors 74. Berry teaches at least one rich cup 58 fluidly coupled to the combustion chamber at the dome inlet, a plurality of openings 48 arranged about the at least one rich cup, see fig. 6, and a passage 48 extending between a passage inlet, see fig. 7, the left side of passage 48, and a passage outlet, see fig. 7, the right side of passage 48, the passage outlet defining at least one lean cup in the plurality of openings, passage openings 48 are air wholes and are interpreted as lean cups. It would have been obvious to an ordinary skilled worker to provide a nozzle taught by Berry, in the apparatus of Roberts, in view of Donisi and Joshi, in order to provide a nozzle that allows an air flow to impinge on a fuel stream to induce mixing. See para. [0023]. Regarding claim 2, Roberts, in view of Donisi, Joshi, and Berry, discloses the at least one lean cup in the plurality of openings defines a dilution hole in an off position and defines a lean cup in an on position. Referring to fig. 7, Berry shows a fuel circuit 78 where in conjunction with at least some of the passages 48, the two are interpreted as a lean cup. The fuel passages are capable of being turned off and there for the lean cup would operate as only a dilution hole with the air flowing through some of the passages 48. PNG media_image1.png 572 681 media_image1.png Greyscale Regarding claim 4, Roberts, in view of Donisi, Joshi, and Berry, discloses the at least one rich cup is a plurality of rich cups and the plurality of openings is multiple sets of lean cups including the at least one leap cup, the multiple sets of lean cups arranged circumferentially about the engine centerline, each set of lean cups associated with a respective rich cup of the plurality of rich cups. Referring to fig. 6, Berry shows a plurality of rich cups 58, interpreted as at least the two holes labeled 58, and the plurality of openings 48 are interpreted as multiple sets of lean cups, interpreted as the four closes holes 48, each of the fuel nozzles of fig. 6 would be circumferentially arranged about the engine centerline combustor of Roberts and thus each set of lean cups is associated with a respective rich cup of the plurality of rich cups. Regarding claim 5, Roberts, in view of Donisi, Joshi, and Berry, discloses all elements including each set of lean cups comprises at least one lean cup spaced a first linear distance from the respective rich cup and another at least one lean cup spaced a second liner distance from the respective rich cup. PNG media_image2.png 572 681 media_image2.png Greyscale Regarding claim 7, Roberts, in view of Donisi, Joshi, and Berry, discloses each set of lean cups further comprises a first lean cup spaced radially outward from the respective rich cup and a second lean cup spaced radially inward from the respective rich cup. For the purposes of claim 7, referring to the annotated figure above, Berry shows a rich cup, rich cup a, b and a plurality of lean cups sets, a, b, where the lean cup sets have one cup radially outward of the rich cup and a second cup radially inward therefrom. Regarding claim 8, Roberts, in view of Donisi, Joshi, and Berry, discloses the first linear distance is equal to the second linear distance. Referring to claim 7, the rich cups are at the center of the injector and the lean cups are chosen to be those cups that are equidistant therefrom, thus, the first and second linear distances are the same. Regarding claim 9, Roberts, in view of Donisi, Joshi, and Berry, discloses the set of lean cups includes an array of lean cups annularly arranged a radial distance about the respective rich cup. Referring to fig. 6 for example, Berry shows the rich cups 58 are surrounded annularly by the lean cups 48. Regarding claim 11, Roberts, in view of Donisi, Joshi, and Berry, discloses the combustor size rating is based on the thrust of the gas turbine engine and the thrust is between sixty kN and 500 kN. Donisi teaches the thrust is between 160-550 kN. See para. [0077]. Regarding claim 13, Roberts, in view of Donisi, Joshi, and Berry, discloses all elements as discussed in claim 1. Furthermore, when the nozzles of Berry are integrated in the engine of Roberts, the nozzles would be annularly/circumferentially distributed about the combustor. Thus, Roberts, in view of Donisi, Joshi, and Berry, discloses a plurality of spaced rich cups, each element 58 in each of the nozzles circumferentially spaced, fluidly coupled to the combustion chamber and a plurality of lean cups interspersed amongst the plurality of spaced rich cups, the lean cups surround the rich cups in a given injector where the lean cups are interspersed between rich cups of adjacent nozzles. Regarding claim 14, Roberts, in view of Donisi, Joshi, and Berry, discloses a dome wall 64 coupled to the inner liner 60 further defining the combustion chamber 62, with the plurality of lean cups 48 located in the dome wall. The injectors are located in the dome wall and thus the lean cups 48 are in the dome wall. Regarding claim 15, Roberts, in view of Donisi, Joshi, and Berry, discloses all elements referring to claim 1 above. Regarding claim 20, Roberts, in view of Donisi, Joshi, and Berry, discloses all elements referring to claim 11 above. Claim(s) 10 and 21 is/are rejected under 35 U.S.C. 103 as being unpatentable over Roberts, in view of Donisi, Joshi, and Berry, as applied to claim 1 above, and further in view of Chen US 2009/0199563. Regarding claims 10 and 21, Roberts, in view of Donisi, Joshi, and Berry, discloses all elements including a core air flow parameter between 2.5 and 50 kN. Donisi teaches the core air flow parameter being between 9-50kN. Roberts, in view of Donisi, Joshi, and Berry, does not disclose the combustor size rating is between two inches and three and one quarter inches. Chen teaches that the size of the combustor can vary based on application. In some applications a combustor can have a size rating up to 4. See para. [0037]. It would have been obvious to an ordinary skilled worker to provide a combustor size rating of up to 4 in the engine of Roberts, in view of Donisi, Joshi, and Berry, as taught by Chen, in order to provide the desired performance for a particular application. Id. Response to Arguments Applicant’s arguments with respect to all claim(s) have been considered but are moot because the new ground of rejection does not rely on any reference applied in the prior rejection of record for any teaching or matter specifically challenged in the argument. The Applicant argues that the amendment warrants removal of the new matter and indefiniteness rejections and that the hydrogen without diluent is supported in the original disclosure. The Examiner disagrees at least in part. The Amendment provided herein derives from one paragraph in the specification. At para. [0076], the specification makes clear that the use of diatomic hydrogen without diluent is in the embodiments where the combustor is configured to operate without diluents. While it is potentially conceivable to utilize hydrogen without any diluents mixed in, the specification makes clear that the embodiment in which this is contemplated is not compatible with the combustor having a diluent. Thus, while an indefiniteness rejection is withheld, the amendment still raises the same new matter issue at its core. Additionally, since the claims omit the contradictory limitations, new prior art is applied in view of the scope change. Conclusion Applicant's amendment necessitated the new ground(s) of rejection presented in this Office action. Accordingly, THIS ACTION IS MADE FINAL. See MPEP § 706.07(a). Applicant is reminded of the extension of time policy as set forth in 37 CFR 1.136(a). A shortened statutory period for reply to this final action is set to expire THREE MONTHS from the mailing date of this action. In the event a first reply is filed within TWO MONTHS of the mailing date of this final action and the advisory action is not mailed until after the end of the THREE-MONTH shortened statutory period, then the shortened statutory period will expire on the date the advisory action is mailed, and any nonprovisional extension fee (37 CFR 1.17(a)) pursuant to 37 CFR 1.136(a) will be calculated from the mailing date of the advisory action. In no event, however, will the statutory period for reply expire later than SIX MONTHS from the mailing date of this final action. Any inquiry concerning this communication or earlier communications from the examiner should be directed to GERALD LUTHER SUNG whose telephone number is (571)270-3765. The examiner can normally be reached 9-5 PST. Examiner interviews are available via telephone, in-person, and video conferencing using a USPTO supplied web-based collaboration tool. To schedule an interview, applicant is encouraged to use the USPTO Automated Interview Request (AIR) at http://www.uspto.gov/interviewpractice. If attempts to reach the examiner by telephone are unsuccessful, the examiner’s supervisor, Devon Kramer can be reached at (571)272-7118. The fax phone number for the organization where this application or proceeding is assigned is 571-273-8300. Information regarding the status of published or unpublished applications may be obtained from Patent Center. Unpublished application information in Patent Center is available to registered users. To file and manage patent submissions in Patent Center, visit: https://patentcenter.uspto.gov. Visit https://www.uspto.gov/patents/apply/patent-center for more information about Patent Center and https://www.uspto.gov/patents/docx for information about filing in DOCX format. For additional questions, contact the Electronic Business Center (EBC) at 866-217-9197 (toll-free). If you would like assistance from a USPTO Customer Service Representative, call 800-786-9199 (IN USA OR CANADA) or 571-272-1000. /GERALD L SUNG/Primary Examiner, Art Unit 3741
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Prosecution Timeline

Jun 07, 2024
Application Filed
Nov 26, 2024
Response after Non-Final Action
Sep 11, 2025
Non-Final Rejection — §103, §112
Dec 02, 2025
Examiner Interview Summary
Dec 02, 2025
Applicant Interview (Telephonic)
Dec 16, 2025
Response Filed
Feb 19, 2026
Final Rejection — §103, §112
Mar 04, 2026
Examiner Interview Summary
Mar 04, 2026
Applicant Interview (Telephonic)
Apr 16, 2026
Response after Non-Final Action
Apr 16, 2026
Notice of Allowance

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Study what changed to get past this examiner. Based on 5 most recent grants.

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Prosecution Projections

3-4
Expected OA Rounds
80%
Grant Probability
99%
With Interview (+28.9%)
3y 5m
Median Time to Grant
Moderate
PTA Risk
Based on 842 resolved cases by this examiner. Grant probability derived from career allow rate.

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