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 .
This is the third office action on the merits. This office action is in response to the request for continued examination filed on 12/22/2025. Applicant has amended claims 2, 5, 9, and 13. Claims 22-26 remain withdrawn from further consideration. Claims 2-15 and 27 are pending and examined.
Continued Examination Under 37 CFR 1.114
A request for continued examination under 37 CFR 1.114, including the fee set forth in 37 CFR 1.17(e), was filed in this application after final rejection. Since this application is eligible for continued examination under 37 CFR 1.114, and the fee set forth in 37 CFR 1.17(e) has been timely paid, the finality of the previous Office action has been withdrawn pursuant to 37 CFR 1.114. Applicant's submission filed on December 22, 2025 has been entered.
Claim Objections
Claim 9 is objected to because of the following informalities:
Claim 9, lines 16-17: “shutting off flow of the primary fuel from the primary fuel source” is believed to be in error for --shutting off flow of the first primary fuel from the first primary fuel source-- (note that there is only one primary fuel source, namely “the first primary fuel source”)
Appropriate correction is required.
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.
This application currently names joint inventors. In considering patentability of the claims the examiner presumes that the subject matter of the various claims was commonly owned as of the effective filing date of the claimed invention(s) absent any evidence to the contrary. Applicant is advised of the obligation under 37 CFR 1.56 to point out the inventor and effective filing dates of each claim that was not commonly owned as of the effective filing date of the later invention in order for the examiner to consider the applicability of 35 U.S.C. 102(b)(2)(C) for any potential 35 U.S.C. 102(a)(2) prior art against the later invention.
Claims 2, 4, 7-8, and 27 are rejected under 35 U.S.C. 103 as being unpatentable over Stammen (US 2015/0184594 A1), in view of Surnilla (US 2012/0048242 A1: IDS reference), Durand (US 2021/0062729 A1), and Chen (CN 203763980 U: references to text will be based on Machine Translation provided in the prior office action).
Regarding claim 2, Stammen teaches (Figs. 1-3) a method of controlling fuel supply to two or more gas turbine engines (10 – Fig. 1; 82 – Fig. 2, which shows two gas turbine engines 82), the method comprising:
(a) supplying a primary fuel (20 – Fig. 1; Fig. 2 shows two lines 20, one for each gas turbine 82) to the two or more gas turbine engines (10) – (via primary fuel line 21 – see also ¶ [0017], ll. 1-3) from a primary fuel source (Fig. 1: box 20);
(b) receiving an indication (“receive fuel flow interruption signal” – Fig. 3, block 92) that a supply pressure of the primary fuel (20) to an identified gas turbine engine (10) that is at least one of the two or more gas turbine engines (82) falls below a set point (¶ [0019], ll. 6-10: “An interruption event may result when a fuel flow of the primary fuel 20 along the primary fuel line 21 to the gas turbine system 10 is temporarily hindered or stalled (e.g., temporary flow decrease, reduction in fuel flow, fluctuation in fuel flow, or other instabilities)”. A flow decrease or a reduction in fuel flow indicates that the supply pressure has decreased, or fallen below a set point);
(c) determining (via sensors 46) that the supply pressure of the primary fuel (20) to the at least one of the two or more gas turbine engines (82) remains below the set point (note that sensors 46 may be a pressure control sensor or pressure sensors – see ¶ [0022], ll. 5-8. The controller 48 receives the fuel flow interruption signal from one or more sensors 46 – see ¶ [0029], ll. 3-5, and would determine that the supply pressure remains below the set point, based on the data received from the one or more sensors 46);
(d) a secondary fuel (22 – Figs. 1-2), wherein the secondary fuel (22) is contained within one or more secondary fuel tanks (as shown by ref. nos. “22” and “84” in Fig. 2); and
(e) causing supply of the secondary fuel (22) to the identified gas turbine engine (10, 82) in place of at least some of the primary fuel (20) supplied to the identified gas turbine engine (10, 82) – (¶ [0019], ll. 10-14: “Generally, the gas turbine system 10 may compensate for an interruption event by increasing fuel flow of the secondary fuel 22 from the secondary fuel line 23 (e.g., transitioning from the primary fuel 20 to the secondary fuel 22)”).
However, Stammen does not teach identifying an amount of the secondary fuel available.
Surnilla teaches (Figs. 2-3) a fuel system (200 – Fig. 2; 300 – Fig. 3) for an internal combustion engine (200 – Fig. 2) comprising a first fuel tank (302) and a second fuel tank (312).
It is noted that the first fuel tank (302) and the second fuel tank (312) contain fuel level sensors (306 and 316, respectively).
Surnilla further teaches identifying an amount of fuel available in the first fuel tank (302) and the second fuel tank (312) – (Fig. 4, block 404 – see also ¶ [0063], ll. 4-10).
It would have been obvious to a person having ordinary skill in the art before the effective filing date to modify Stammen by including the step of identifying an amount of the secondary fuel available, in order to determine if a sufficient amount of the secondary fuel is available for direct injection, as taught by Surnilla (¶ [0065], ll. 1-2).
However, Stammen, in view of Surnilla, does not teach a filter is disposed between the primary fuel source and the two or more gas turbine engines.
Durand teaches (Fig. 2) a fuel system (200) for a gas turbine engine (100) comprising a primary fuel source (224), wherein a filter is disposed (on fuel conduit 228) between the primary fuel source (224) and the gas turbine engine (100) – (¶ [0036], ll. 1-4: “the fuel system 220 additionally includes one or more fuel filters, which can be located within the fuel conduit 228, at fuel outlets for the primary fuel supply 224 and/or the backup boost pump 226”).
It would have been obvious to a person having ordinary skill in the art before the effective filing date to modify Stammen, in view of Surnilla, by including a filter disposed between the primary fuel source and the two or more gas turbine engines, in order to filter out particulate matter from the fuel for better combustion, as taught by Durand (¶ [0036], ll. 11-13).
However, Stammen, in view of Surnilla and Durand, does not teach the step of:
(f) in response to (c), isolating the filter from fluid communication with the primary fuel source and the two or more gas turbine engines based on a pressure differential across the filter exceeding a threshold.
It is noted that Durand further teaches performing a maintenance action on the fuel filter, such as cleaning or replacing the filter, based on multiple fuel pressure readings that determine whether the filter has become congested (¶ [0037], ll. 7-15).
Chen teaches (Fig. 1) a filtration device used on a boiler, the filtration device comprising a filter (3), control valves (2 and 7), and pressure sensors (1 and 10); and further teaches:
isolating the filter (by closing control valves 2 and 7) from fluid communication with the boiler based on a pressure differential (as measured by pressure sensors 1 and 10) across the filter (3) exceeding a threshold (¶ [0026], ll. 11-14: “If the multi-stage filter is not cleaned in time and the pressure difference between the first and second sensors continues to increase and reaches the automatic switching value, the controller will send instructions to the control valve, the first and second control valves 2 and 7 will automatically close”).
It would have been obvious to a person having ordinary skill in the art before the effective filing date to modify Stammen, in view of Surnilla and Durand, by including Chen’s arrangement of the filtration device comprising the control valves and the pressure sensors, all with respect to Durand’s filter, thus providing the step of: (f) in response to step (c), isolating the filter from fluid communication with the primary fuel source and the two or more gas turbine engines based on a pressure differential across the filter exceeding a threshold, in order to provide a means for isolating the filter (by closing controls valves 2 and 7), thereby allowing the filter to be taken out for cleaning or replacement, as taught by Chen (¶ [0026], ll. 13-14 and 20-21).
However, Stammen, in view of Surnilla, Durand, and Chen does not teach isolating the filter includes shutting off flow of the primary fuel from the primary fuel source to the two or more gas turbine engines.
It is noted that Durand teaches (Fig. 2) a fuel supply system similar to that of Stammen’s in that Durand’s fuel supply system (200) also comprises a primary fuel source (224) and a secondary fuel (226). As stated in ¶ [0036], ll. 1-4, Durand teaches one or more fuel filters, which can be located at fuel outlets for the primary fuel supply (224) and/or the secondary fuel (226). By taking the teaching of Chen’s means of isolating the filter (control valves 2 and 7) and applying it to Durand’s fuel filter located at the outlet of the primary fuel supply (224), the resulting combination would teach: isolating the filter (Durand’s filter at the outlet of 224) includes shutting off flow (via Chen’s control valves) of the primary fuel from the primary fuel source (Durand, 224) to the gas turbine engine (Durand, 100); and would further allow step (e) to be performed because the secondary fuel (226) would not be restricted from providing fuel to the gas turbine engine (100).
It would have been obvious to a person having ordinary skill in the art before the effective filing date of the claimed invention to modify Stammen, in view of Surnilla, Durand, and Chen, such that isolating the filter includes shutting off flow of the primary fuel from the primary fuel source to the two or more gas turbine engines, because it has been held under the “obvious to try” provision, that choosing from a finite number of identified, predictable solutions (in this case, to choose between various locations of including a fuel filter in the fuel supply system of Stammen, the various locations taught by Durand), with a reasonable expectation of success (in this case, applying control valves on a fuel filter located specifically at the outlet of the primary fuel source would allow isolating the filter for cleaning or replacement of the filter, as taught by Chen, thereby shutting off flow of the primary fuel from the primary fuel source to the two or more gas turbine engines, and further allow the secondary fuel to be supplied to the identified gas turbine engine in place of at least some of the primary fuel supplied to the identified gas turbine engine) was an obvious extension of prior art teachings. See KSR Int’l Co. v. Teleflex Inc., 550 U.S. 398, 415-421, 82 USPQ2d 1385, 1395-97 (2007), MPEP 2143 (I)(E).
Regarding claim 4, Stammen, in view of Surnilla, Durand, and Chen, teaches the invention as claimed and as discussed above for claim 2, and Stammen further teaches (Fig. 2) the secondary fuel (22) is CNG and/or natural gas (as shown in Fig. 2, natural gas supply 76 is contained within secondary fuel 22).
Regarding claim 7, Stammen, in view of Surnilla, Durand, and Chen, teaches the invention as claimed and as discussed above for claim 2, and Stammen further teaches (Fig. 1) the primary fuel (20) is supplied to the two or more gas turbine engines (10, 82) via one or more of: a hybrid hub system, a multiple hub and spoke system, or a daisy chain system (¶ [0017], ll. 1-4: “The turbine combustor 14 may have multiple fuel nozzles configured to receive the primary fuel 20 from a primary fuel line 21 and/or the secondary fuel 22 from a secondary fuel line 23”. In this case, this could be interpreted as a daisy chain system because the multiple fuel nozzles are all fluidly connected together in a sequence to receive the primary fuel 20).
Regarding claim 8, Stammen, in view of Surnilla, Durand, and Chen, teaches the invention as claimed and as discussed above for claim 7, and Stammen further teaches (Fig. 1) the secondary fuel (22) is supplied to a fuel manifold configured to provide fuel to the identified gas turbine engine (10, 82) – (¶ [0017], ll. 1-4: “The turbine combustor 14 may have multiple fuel nozzles configured to receive the primary fuel 20 from a primary fuel line 21 and/or the secondary fuel 22 from a secondary fuel line 23”. In this case, there must inherently be a manifold to distribute the secondary fuel 22 to multiple fuel nozzles).
Regarding claim 27, Stammen, in view of Surnilla, Durand, and Chen, teaches the invention as claimed and as discussed above for claim 2, and the combination further teaches (Chen , Fig. 1):
a first valve (2) is disposed upstream of the filter (3),
a second valve (7) is disposed downstream of the filter (3),
a first sensor (1) disposed upstream of the first valve (2) is configured to provide a first pressure measurement (¶ [0017], l. 3),
a second sensor (10) disposed downstream of the second valve (7) is configured to provide a second pressure measurement (¶ [0017], l. 4), and
when a pressure differential between the first pressure measurement (from 1) and the second pressure measurement (from 10) exceeds a predetermined threshold, closing each of the first valve (2) and second valve (7) – (¶ [0026], ll. 11-14: “If the multi-stage filter is not cleaned in time and the pressure difference between the first and second sensors continues to increase and reaches the automatic switching value, the controller will send instructions to the control valve, the first and second control valves 2 and 7 will automatically close. Note that this is also a contingent limitation – see below).
As stated in the rejection of claim 2 above, Chen’s arrangement of the filtration device (Fig. 1) comprising the control valves and the pressure sensors was added to Durand’s filter in order to provide the physical structure needed for isolating the filter from fluid communication with the primary fuel source and the two or more gas turbine engines.
The recitation “when a pressure differential between the first pressure measurement and the second pressure measurement exceeds a predetermined threshold, closing each of the first valve and second valve” may be interpreted as a conditional claim limitation that is only required to be performed when the recited condition is met. Consequently, if none of the recited conditions are met, then the claimed method is requiring no steps be performed. “The broadest reasonable interpretation of a method (or process) claim having contingent limitations requires only those steps that must be performed and does not include steps that are not required to be performed because the condition(s) precedent are not met.” See MPEP 2111.04, II. In this case, the claim is not explicitly requiring any steps be performed because the condition (a pressure differential between the first pressure measurement and the second pressure measurement exceeds a predetermined threshold) is not required to occur.
Claim 3 is rejected under 35 U.S.C. 103 as being unpatentable over Stammen (US 2015/0184594 A1), in view of Surnilla (US 2012/0048242 A1: IDS reference), Durand (US 2021/0062729 A1), and Chen (CN 203763980 U: references to text will be based on Machine Translation provided in the prior office action), and in further view of Kraft (US 2018/0030902 A1).
Regarding claim 3, Stammen, in view of Surnilla, Durand, and Chen, teaches the invention as claimed and as discussed above for claim 2, except for the primary fuel comprising field gas and/or pipeline gas.
Kraft teaches (Fig. 15) a similar fuel supply for a gas turbine comprising a primary fuel (1502) and a secondary fuel (1530). Kraft further teaches “at a duel fuel gas turbine power plant, pipeline natural gas is typically the primary fuel source”.
It would have been obvious to a person having ordinary skill in the art before the effective filing date to modify Stammen, in view of Surnilla, Durand, and Chen, such that the primary fuel comprises field gas and/or pipeline gas, because it was known that in power plants having multiple gas turbines, pipeline natural gas is typically the primary fuel source, as taught by Kraft (¶ [0141], ll. 1-4).
Claims 5-6 are rejected under 35 U.S.C. 103 as being unpatentable over Stammen (US 2015/0184594 A1), in view of Surnilla (US 2012/0048242 A1: IDS reference), Durand (US 2021/0062729 A1), and Chen (CN 203763980 U: references to text will be based on Machine Translation provided in the prior office action), and in further view of Heckel (US 2013/0076530 A1).
Regarding claim 5, Stammen, in view of Surnilla, Durand, and Chen, teaches the invention as claimed and as discussed above for claim 2, except for (b’) in response to receiving the indication:
initiating a timer; and
increasing a data sampling rate associated with the two or more gas turbine engines prior to step (c).
Heckel teaches (Figs. 4-5) a monitoring system (200 – Fig. 4) for a portable electronic device (¶ [0008], ll. 1-2) comprising a processor (201), a power controller (208), and several environmental sensors (204, 205, 206, and 207).
Heckel further teaches initiating a timer (¶ [0020], l. 6: “Upon initialization the system will set a timer”); and
increasing a data sampling rate (Fig. 5: S408 – see also ¶ [0020], ll. 21-22: “If the event is determined to be significant and ongoing the sample rate will be increased S408 for better resolution”).
It would have been obvious to a person having ordinary skill in the art before the effective filing date to modify Stammen, in view of Surnilla, Durand, and Chen, by including the step of (b’) in response to receiving the indication: initiating a timer; and increasing a data sampling rate associated with the two or more gas turbine engines prior to step (c), in order to provide for better resolution of data from the sensors (in this case, the supply pressure of Stammen via the pressure sensors of Chen), as taught by Heckel (¶ [0020], ll. 21-22).
Regarding claim 6, Stammen, in view of Surnilla, Durand, Chen, and Heckel, teaches the invention as claimed and as discussed above for claim 5, and the combination further teaches repeating steps (a), (b), (b'), (c), (d), and (e) for at least some gas turbine engines of the two or more gas turbine engines (Stammen, 82) still operating using the primary fuel (Stammen, 20) – (Stammen’s Fig. 2 shows two gas turbine engines 82 each with their own feed compressors 13 and 78, respectively. As shown in Stammen’s Figs. 1 and 2, the feed compressors 13 and 78 provides a primary fuel to the respective gas turbine engine 10, 82. Therefore, the method would be repeated for each of the gas turbine engines 82).
Furthermore, it has been held that mere duplication of parts (in this case, duplicating the method steps for a second gas turbine engine) has no patentable significance unless a new and unexpected result is produced. In re Harza, 274 F.2d 669, 124 USPQ 378 (CCPA 1960), MPEP 2144.04 (VI)(B).
Claim 9 is rejected under 35 U.S.C. 103 as being unpatentable over Stammen (US 2015/0184594 A1), in view of Durand (US 2021/0062729 A1) and Chen (CN 203763980 U: references to text will be based on Machine Translation provided in the prior office action).
Regarding claim 9, Stammen teaches (Figs. 1-3) a method of controlling fuel supply to two or more gas turbine engines (10 – Fig. 1; 82 – Fig. 2, which shows two gas turbine engines 82), the method comprising:
(a) supplying a first primary fuel (20 – Fig. 1) to the two or more gas turbine engines (10) – (via primary fuel line 21 – see also ¶ [0017], ll. 1-3) from a first primary fuel source (Fig. 1: box 20);
(b) receiving an indication (“receive fuel flow interruption signal” – Fig. 3, block 92) that a supply pressure of the first primary fuel (20) to the two or more gas turbine engines (82) falls below a set point (¶ [0019], ll. 6-10: “An interruption event may result when a fuel flow of the primary fuel 20 along the primary fuel line 21 to the gas turbine system 10 is temporarily hindered or stalled (e.g., temporary flow decrease, reduction in fuel flow, fluctuation in fuel flow, or other instabilities)”. A flow decrease or a reduction in fuel flow indicates that the supply pressure has decreased, or fallen below a set point);
(c) determining (via sensors 46) that the supply pressure of the first primary fuel (20) to the two or more gas turbine engines (82) remains below the set point (note that sensors 46 may be a pressure control sensor or pressure sensors – see ¶ [0022], ll. 5-8. The controller 48 receives the fuel flow interruption signal from one or more sensors 46 – see ¶ [0029], ll. 3-5, and would determine that the supply pressure remains below the set point, based on the data received from the one or more sensors 46);
(d) identifying an amount of a second primary fuel (“supplemental fuel” from head tank 54 and fuel blending skid 60 – see ¶ [0025], ll. 1-4. Also, ¶ [0027], ll. 22-24 teaches “the controller 48 may additionally be configured to identify the amount of fuel stored within the head tank 54”); and
(e) causing supply of the second primary fuel (supplemental fuel) to the two or more gas turbine engines (10, 82) in place of at least some of the first primary fuel (20) supplied to the two or more gas turbine engines (10, 82) – (¶ [0027], ll. 1-6: “at the detection of the interruption event where fuel flow of the primary or first fuel from the primary fuel line 21 is interrupted, the fuel valve 42 disposed upstream of the primary fuel line 21 is configured to open to allow the supplemental fuel to be routed to the combustor 22 of the turbine 16”).
However, Stammen does not teach a filter is disposed between the first primary fuel source and the two or more gas turbine engines.
Durand teaches (Fig. 2) a fuel system (200) for a gas turbine engine (100) comprising a first primary fuel source (222), wherein a filter is disposed (on fuel conduit 228) between the first primary fuel source (222) and the gas turbine engine (100) – (¶ [0036], ll. 1-4: “the fuel system 220 additionally includes one or more fuel filters, which can be located within the fuel conduit 228, at fuel outlets for the primary fuel supply 224 and/or the backup boost pump 226”).
It would have been obvious to a person having ordinary skill in the art before the effective filing date to modify Stammen by including a filter disposed between the first primary fuel source and the two or more gas turbine engines, in order to filter out particulate matter from the fuel for better combustion, as taught by Durand (¶ [0036], ll. 11-13).
However, Stammen, in view of Durand, does not teach the step of:
(f) in response to (c), isolating the filter from fluid communication with the first primary fuel source and the two or more gas turbine engines based on a pressure differential across the filter exceeding a threshold.
It is noted that Durand further teaches performing a maintenance action on the fuel filter, such as cleaning or replacing the filter, based on multiple fuel pressure readings that determine whether the filter has become congested (¶ [0037], ll. 7-15).
Chen teaches (Fig. 1) a filtration device used on a boiler, the filtration device comprising a filter (3), control valves (2 and 7), and pressure sensors (1 and 10); and further teaches:
isolating the filter (by closing control valves 2 and 7) from fluid communication with the boiler based on a pressure differential (as measured by pressure sensors 1 and 10) across the filter (3) exceeding a threshold (¶ [0026], ll. 11-14: “If the multi-stage filter is not cleaned in time and the pressure difference between the first and second sensors continues to increase and reaches the automatic switching value, the controller will send instructions to the control valve, the first and second control valves 2 and 7 will automatically close”).
It would have been obvious to a person having ordinary skill in the art before the effective filing date to modify Stammen, in view of Durand, by including Chen’s arrangement of the filtration device comprising the control valves and the pressure sensors, all with respect to Durand’s filter, thus providing the step of: (f) in response to step (c), isolating the filter from fluid communication with the primary fuel source and the two or more gas turbine engines based on a pressure differential across the filter exceeding a threshold, in order to provide a means for isolating the filter (by closing controls valves 2 and 7), thereby allowing the filter to be taken out for cleaning or replacement, as taught by Chen (¶ [0026], ll. 13-14 and 20-21).
However, Stammen, in view of Durand and Chen does not teach isolating the filter includes shutting off flow of the primary fuel from the primary fuel source to the two or more gas turbine engines.
It is noted that Durand teaches (Fig. 2) a fuel supply system similar to that of Stammen’s in that Durand’s fuel supply system (200) also comprises a first primary fuel source (224) and a second primary fuel (226). As stated in ¶ [0036], ll. 1-4, Durand teaches one or more fuel filters, which can be located at fuel outlets for the first primary fuel supply (224) and/or the second primary fuel (226). By taking the teaching of Chen’s means of isolating the filter (control valves 2 and 7) and applying it to Durand’s fuel filter located at the outlet of the first primary fuel supply (224), the resulting combination would teach: isolating the filter (Durand’s filter at the outlet of 224) includes shutting off flow (via Chen’s control valves) of the primary fuel from the primary fuel source (Durand, 224) to the gas turbine engine (Durand, 100); and would further allow step (e) to be performed because the second primary fuel (226) would not be restricted from providing fuel to the gas turbine engine (100).
It would have been obvious to a person having ordinary skill in the art before the effective filing date of the claimed invention to modify Stammen, in view of Durand, and Chen, such that isolating the filter includes shutting off flow of the primary fuel from the primary fuel source to the two or more gas turbine engines, because it has been held under the “obvious to try” provision, that choosing from a finite number of identified, predictable solutions (in this case, to choose between various locations of including a fuel filter in the fuel supply system of Stammen, the various locations taught by Durand), with a reasonable expectation of success (in this case, applying control valves on a fuel filter located specifically at the outlet of the first primary fuel source would allow isolating the filter for cleaning or replacement of the filter, as taught by Chen, thereby shutting off flow of the primary fuel from the primary fuel source to the two or more gas turbine engines, and further allow the second primary fuel to be supplied to the identified gas turbine engine in place of at least some of the first primary fuel supplied to the identified gas turbine engine) was an obvious extension of prior art teachings. See KSR Int’l Co. v. Teleflex Inc., 550 U.S. 398, 415-421, 82 USPQ2d 1385, 1395-97 (2007), MPEP 2143 (I)(E).
Claims 10-11 and 14 are rejected under 35 U.S.C. 103 as being unpatentable over Stammen (US 2015/0184594 A1), in view of Durand (US 2021/0062729 A1) and Chen (CN 203763980 U: references to text will be based on Machine Translation provided in the prior office action), and in further view of Kraft (US 2018/0030902 A1).
Regarding claim 10, Stammen, in view of Durand and Chen, teaches the invention as claimed and as discussed above for claim 9, except for the first primary fuel comprises field gas and/or pipeline gas.
Kraft teaches (Fig. 15) a similar fuel supply for a gas turbine comprising a primary fuel (1502) and a secondary fuel (1530). Kraft further teaches “at a duel fuel gas turbine power plant, pipeline natural gas is typically the primary fuel source”.
It would have been obvious to a person having ordinary skill in the art before the effective filing date to modify Stammen, in view of Durand and Chen, such that the primary fuel comprises field gas and/or pipeline gas, because it was known that in power plants having multiple gas turbines, pipeline natural gas is typically the primary fuel source, as taught by Kraft (¶ [0141], ll. 1-4).
Regarding claim 11, Stammen, in view of Durand, Chen, and Kraft, teaches the invention as claimed and as discussed above for claim 10, and Stammen further teaches (Fig. 2) the second primary fuel (supplemental fuel from head tank 54) is CNG and/or natural gas (as shown in Fig. 2, natural gas supply 62 is supplied to head tank 54 to make “supplemental fuel”).
Regarding claim 14, Stammen, in view of Durand, Chen, and Kraft, teaches the invention as claimed and as discussed above for claim 11, and Stammen further teaches (Fig. 1) the first primary fuel (20) and the second primary fuel (supplemental fuel) are supplied to the two or more gas turbine engines (10, 82) via one or more of: a hybrid hub system, a multiple hub and spoke system, or a daisy chain system (¶ [0017], ll. 1-4: “The turbine combustor 14 may have multiple fuel nozzles configured to receive the primary fuel 20 from a primary fuel line 21 and/or the secondary fuel 22 from a secondary fuel line 23”. In this case, this could be interpreted as a daisy chain system because the multiple fuel nozzles are all fluidly connected together in a sequence to receive the primary fuel 20. Note that the “supplemental fuel” would also be supplied to the multiple fuel nozzles).
Claims 12 and 15 are rejected under 35 U.S.C. 103 as being unpatentable over Stammen (US 2015/0184594 A1), in view of Durand (US 2021/0062729 A1), Chen (CN 203763980 U: references to text will be based on Machine Translation provided in the prior office action), and Kraft (US 2018/0030902 A1), and in further view of Surnilla (US 2012/0048242 A1: IDS reference).
Regarding claim 12, Stammen, in view of Durand, Chen, and Kraft, teaches the invention as claimed and as discussed above for claim 11, and Stammen further teaches (i) a secondary fuel (22 – Figs. 1-2), wherein the secondary fuel (22) is contained within one or more secondary fuel tanks (as shown by ref. nos. “22” and “84” in Fig. 2); and
(j) causing supply of the secondary fuel (22) to the two of more gas turbine engines (10, 82) in place of at least some of the first primary fuel (20) or second primary fuel supplied to the two or more gas turbine engines (10, 82) – (¶ [0019], ll. 10-14: “Generally, the gas turbine system 10 may compensate for an interruption event by increasing fuel flow of the secondary fuel 22 from the secondary fuel line 23 (e.g., transitioning from the primary fuel 20 to the secondary fuel 22)”).
However, Stammen, in view of Durand, Chen, and Kraft, does not teach (g) receiving an indication that supply pressure of the second primary fuel to the two or more gas turbine engines falls below a set point; and
(h) determining that the supply pressure of the second primary fuel to the two or more gas turbine engines remains below the set point.
It is noted that Stammen teaches sensors (46) that can detect an interruption of the primary fuel from the primary fuel (20) to the combustor (14) of the gas turbine (82) – (¶ [0029], ll. 6-11). Since the supplemental fuel is routed to the combustor via primary fuel line (21) – (see ¶ [0027], ll. 3-6), the sensors (46) would also be able to detect an interruption of the supplemental fuel.
It would have been obvious to a person having ordinary skill in the art before the effective filing date to modify Stammen, in view of Durand, Chen, and Kraft, by including the steps of (g) receiving an indication that supply pressure of the second primary fuel to the two or more gas turbine engines falls below a set point; and (h) determining that the supply pressure of the second primary fuel to the two or more gas turbine engines remains below the set point, in order to detect an interruption of the second primary fuel, similar to that of the first primary fuel, since both the first primary fuel and the second primary fuel share the same primary fuel line (21).
However, Stammen, in view of Durand, Chen, and Kraft, does not teach identifying an amount of the secondary fuel available.
Surnilla teaches (Figs. 2-3) a fuel system (200 – Fig. 2; 300 – Fig. 3) for an internal combustion engine (200 – Fig. 2) comprising a first fuel tank (302) and a second fuel tank (312).
It is noted that the first fuel tank (302) and the second fuel tank (312) contain fuel level sensors (306 and 316, respectively).
Surnilla further teaches identifying an amount of fuel available in the first fuel tank (302) and the second fuel tank (312) – (Fig. 4, block 404 – see also ¶ [0063], ll. 4-10).
It would have been obvious to a person having ordinary skill in the art before the effective filing date to modify Stammen, in view of Durand, Chen, and Kraft, by including the step of identifying an amount of the secondary fuel available, in order to determine if a sufficient amount of the secondary fuel is available for direct injection, as taught by Surnilla (¶ [0065], ll. 1-2).
Regarding claim 15, Stammen, in view of Durand, Chen, Kraft, and Surnilla, teaches the invention as claimed and as discussed above for claim 12, and Stammen further teaches (Fig. 1) the second primary fuel (supplemental fuel) is supplied to the two or more gas turbine engines (10, 82) as a liquid (¶ [0016], ll. 5-9: “The turbine combustor 14 may receive a liquid fuel, a gas fuel (e.g., natural gas), a process gas fuel, and/or a blended fuel (e.g., a mixture of natural gas and process gas) from a primary fuel supply 20 (e.g., a first fuel) and/or a secondary fuel supply 22 (e.g., a second fuel)”. Note that the “supplemental fuel” is designed to have a composition similar to the composition of the primary fuel 20 – see ¶ [0025], ll. 21-23).
Claim 13 is rejected under 35 U.S.C. 103 as being unpatentable over Stammen (US 2015/0184594 A1), in view of Durand (US 2021/0062729 A1), Chen (CN 203763980 U: references to text will be based on Machine Translation provided in the prior office action ), Kraft (US 2018/0030902 A1), and Surnilla (US 2012/0048242 A1: IDS reference), and in further view of Heckel (US 2013/0076530 A1).
Regarding claim 13, Stammen, in view of Durand, Chen, Kraft, and Surnilla, teaches the invention as claimed and as discussed above for claim 12, except for (g’) in response to receiving the indication:
initiating a timer; and
increasing a data sampling rate associated with the two or more gas turbine engines prior to step (h).
Heckel teaches (Figs. 4-5) a monitoring system (200 – Fig. 4) for a portable electronic device (¶ [0008], ll. 1-2) comprising a processor (201), a power controller (208), and several environmental sensors (204, 205, 206, and 207).
Heckel further teaches initiating a timer (¶ [0020], l. 6: “Upon initialization the system will set a timer”); and
increasing a data sampling rate (Fig. 5: S408 – see also ¶ [0020], ll. 21-22: “If the event is determined to be significant and ongoing the sample rate will be increased S408 for better resolution”).
It would have been obvious to a person having ordinary skill in the art before the effective filing date to modify Stammen, in view of Durand, Chen, Kraft, and Surnilla, by including the step of (g’) in response to receiving the indication: initiating a timer; and increasing a data sampling rate associated with the two or more gas turbine engines prior to step (h), in order to provide for better resolution of data from the sensors (in this case, the supply pressure of Stammen via the pressure sensors of Chen), as taught by Heckel (¶ [0020], ll. 21-22).
Response to Arguments
Applicant's arguments filed December 22, 2025 have been fully considered but they are not persuasive.
Regarding Applicant’s argument (pg. 8 of REMARKS) that “Chen’s bypass system maintains continuous flow of the primary fluid from the primary source to the boiler through an alternate path”, it is noted that the rejection of claims 2 and 9 above has been amended to take only the teaching of isolating the filter using the control valves (2 and 7) and the pressure sensors (1 and 10) to modify the fuel supply system of Stammen, in view of Durand. The bypass line shown in Chen is not relied upon for the proposed modification. However, even if the bypass line were to be included in the proposed modification, a person having ordinary skill in the art would have found it obvious to turn off the bypass line (by closing control valves 4 and 9 as shown in Chen’s Fig. 1) in order to shut off any fluid going to the intended destination (in Chen, it is a boiler; in Stammen, it is the two gas turbine engines) and to isolate the filter for cleaning and/or replacement.
As stated in the above rejections for claims 2 and 9, the proposed modification results in adding control valves to the fuel filter located at the outlet of the primary fuel source. Thus, the filter is isolated by shutting off the control valve, which in turn shuts off flow of primary fuel from the primary fuel source to the two or more gas turbine engines.
Conclusion
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/HENRY NG/Examiner, Art Unit 3741 /DEVON C KRAMER/Supervisory Patent Examiner, Art Unit 3741
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