WO2019221727A1

WO2019221727A1 - Method for detecting outboard-transverse flame migration in an aeroderivative turbine engine, and corresponding detection and control system

Info

Publication number: WO2019221727A1
Application number: PCT/US2018/032994
Authority: WO
Inventors: Jean-Roch JACQUES; Noor Azman MOHAMAT NOR
Original assignee: Siemens Aktiengesellschaft; Siemens Energy, Inc.
Priority date: 2018-05-16
Filing date: 2018-05-16
Publication date: 2019-11-21

Abstract

Outboard-transverse flame migration in an annular profile combustion gas pathway (22) of an aeroderivative turbine engine (10) is detected with a dual-immersion thermocouple probe (32). A first thermocouple (34) in the probe is oriented radially midway between inner (24) and outer (26) circumferential surfaces that define the pathway. A second thermocouple (36) in the probe is oriented nearer to the outer circumferential surface of the pathway. A controller (38) detects outboard-transverse flame migration in the combustion gas pathway, when the second thermocouple temperature exceeds the first thermocouple temperature. An outboard-transverse flame migration detection and control system for an aeroderivative turbine engine comprises an aeroderivative turbine engine (10) having a combustion gas pathway (22) and a dual-immersion thermocouple probe (32) oriented in an inter-turbine duct (20) of the exhaust section of the pathway. The dual-immersion thermocouple probe comprises an elongated probe housing, a first thermocouple in the probe housing proximate a housing tip, for generating a first signal (S1A), and a second thermocouple in the probe housing proximate a housing base, for generating a second signal (SIB). A Controller (38) is separately coupled to the first and second thermocouples for receiving the separate first and second signals and correlating the received first and second thermocouple signals with exhaust gas temperatures in the combustion gas pathway proximate the respective thermocouples.

Description

METHOD FOR DETECTING OUTBOARD-TRANSVERSE FLAME MIGRATION IN AN AERODERIVATIVE TURBINE ENGINE, AND CORRESPONDING DETECTION AND

CONTROL SYSTEM

TECHNICAL FIELD

[0001] The invention relates to a method and system for detecting outboard- transverse flame migration in an aeroderivative turbine engine, in order to reduce likelihood of engine damage.

BACKGROUND

[0002] Aeroderivative gas turbines are mainly used for mechanical drives applications such as, driving sales gas (i.e., natural gas conditioned to meet customer specifications), gas lifting or gas injection turbo-compressors, main oil line (MOL) pumps and for power generations application driving 2 or 4 pole turbo-generators in oil and gas production. Aeroderivative jet engines are typically used for oil and gas application, due to their lightweight configuration, versatility, and quick response time. However, given that they are a derivative of an on- wing engine, their constructions employ lightweight material, as well as advanced aerodynamic, aero- thermal, and combustion technology that require good quality fuel and combustion airfor full power, continuous base load operations. In the airline industry, the gas turbine is operated at full power or base load only during take-off and landing while in the oil and gas industry, the gas turbine— especially for mechanical drive application— is typically operated at base load continuously to meet the production demand.

[0003] Under such land-based, continuous base load applications, the aero thermal stresses and gas temperatures are always at their base load operating conditions. Any excursions in the operating profile, particularly variations in fuel and air quality, will have adverse impact on the aero thermal stresses and gas temperatures. Such situations will not only affect the fatigue life cycle of the gas turbine components but also the heat transfers rates of the components— especially the hot section components. Understanding these operating conditions is a key effort in successful implementation of preventive maintenance programs for aeroderivative turbine engines. In offshore oil production, preventive maintenance is one of the key activities in order to maintain the high output of crude oil, and to reduce the production costs associated with repairs and unplanned production outages.

SUMMARY OF INVENTION

[0004] An investigation was conducted to determine causes of what appeared to be engine overheating damage to turbine seal segments and other components that formed a portion of the outer annular circumference of a combustion gas pathway of an aeroderivative turbine engine. Based on inspection of the damaged seals and the other damaged components, it was estimated that they were exposed to temperatures in the range of 1000° C to 1050° C. Normal operating temperature is in the range 860° C - 900° C.

[0005] The investigation determined that damage to components forming the outer circumferential periphery of the annular profile, combustion gas pathway in examined aeroderivative turbine engines was attributable to outboard-transverse flame migration in the pathway. It was determined that variations in fuel composition caused the combustion flame to migrate toward the outboard circumferential side of the combustion gas pathway, under some operating conditions. The study monitored local temperature of exhaust gas, by inserting a monitoring thermocouple probe proximate the outer circumferential periphery of the combustion gas pathway. The study also monitored orientation of the combustion flame front during engine operation. Locally increasing temperature proximate the outer circumferential periphery of the annular profile, combustion gas pathway, as measured by the monitoring thermocouple probe, correlated with outboard-transverse flame migration. The inventors’ solution to the overheating problem was to monitor the exhaust gas temperature proximate the the outer circumferential periphery of the annular profile, combustion gas pathway, by insertion of an outer-periphery thermocouple probe, and alter the fuel/air mixture (FAM) to re-center the flame in the annular, combustion gas pathway when monitored temperature proximate the outer circumferential periphery exceeded monitored temperature at the center of the pathway. This solution of the present invention mitigated overheating of components that form the outer annular periphery of the combustion gas pathway.

[0006] Exemplary embodiments described herein mitigate potential aeroderivative turbine engine damage in outer circumferential surface components of the engine that define its annular combustion gas pathway, by detecting outboard-transverse flame migration with a dual-immersion thermocouple probe. A first thermocouple in the probe is oriented radially midway between inner and outer circumferential surfaces that define the combustion gas pathway. The second thermocouple in the probe is oriented nearer to the outer circumferential surface that defines the combustion gas pathway. A controller detects outboard-transverse flame migration in the combustion gas pathway, when the second thermocouple temperature exceeds the first thermocouple temperature. In some embodiments, the controller enunciates when the first or the second thermocouple temperature exceeds a maximum temperature. In other embodiments, an engine control system, coupled to the controller, mitigates flame migration detected by the controller, by altering fuel/air mixture burned in the combustion gas pathway, re-centering the flame in the annular combustion gas pathway.

[0007] Exemplary embodiments of the invention feature methods for detecting outboard-transverse flame migration in an aeroderivative turbine engine, having an annular profile, combustion gas pathway, radially bounded by inner and outer circumferential surfaces. The combustion gas pathway extends axially from a combustion section, through a turbine section, and an exhaust section. A dual- immersion thermocouple probe is oriented in an inter-turbine duct (ITD) of the exhaust section of the combustion gas pathway, so that a first thermocouple in the probe is oriented radially midway between the inner and outer circumferential surfaces of the pathway, and second thermocouple in the probe is oriented nearer to the outer circumferential surface of the pathway. The first and second thermocouples send respective first and second signals to a controller, which receives and correlates the respective thermocouple signals with local exhaust gas temperature at each respective thermocouple location in the combustion gas pathway. The controller determines respective first and second temperatures of the exhaust gas, using the first and second thermocouple signals. The controller identifies an outboard-transverse flame migration in the combustion gas pathway, when the second temperature exceeds the first temperature. In some embodiments, the controller enunciates when either of the temperatures exceeds a maximum temperature. In other embodiments, an engine control system, coupled to the controller, alters fuel/air mixture (FAM) burned in the combustion section to re-center the flame in the combustion gas pathway, when the controller determines that either of the first or second temperatures exceeds the maximum temperature. In other embodiments, a plurality of circumferentially spaced, dual-immersion, thermocouple probes, each having first and second thermocouples is coupled to the controller.

[0008] Other exemplary embodiments of the invention feature an outboard-transverse flame migration detection and control system for an aeroderivative turbine engine, having an annular profile, combustion gas pathway, radially bounded by inner and outer circumferential surfaces, with the pathway extending axially from a combustion section, through a turbine section including alternating rows of turbine blades and stator vanes, and an exhaust section. A dual-immersion thermocouple probe is oriented in an inter-turbine duct (ITD) of the exhaust section of the pathway, axially downstream of a last row of stator vanes or turbine blades. The dual-immersion thermocouple probe has elongated probe housing. A housing base is coupled to the outer circumferential surface of the pathway, and a distal housing tip is oriented radially midway between the inner and outer circumferential surfaces of the pathway. A first thermocouple is oriented in the probe housing proximate the housing tip, for generating a first signal that is proportional to its local temperature. A second thermocouple is oriented in the probe housing proximate the housing base, for generating a second signal that is proportional to its local temperature A controller is separately coupled to the first and second thermocouples, for receiving the respective, separate first and second signals sent by them. The controller correlates the received, respective, first and second thermocouple signals with exhaust gas temperatures in the combustion gas pathway proximate the respective thermocouples, and identifies outboard-transverse flame migration, when the second sensed temperature exceeds the first sensed temperature. In some embodiments, an engine control system coupled to the controller, regulates fuel/air mixture (FAM) burned in the combustion section in order to re-center the flame in the combustion gas pathway when the second sensed temperature exceeds the first sensed temperature. In some embodiments, the engine control system switches FAM regulation, based on the second sensed temperature, when it exceeds the first sensed temperature. In other embodiments, the engine control system regulates the FAM based on the higher of the first or second sensed temperatures.

[0009] Other outboard-transverse flame migration detection and control system embodiments incorporate a plurality of dual-immersion thermocouple probes, in circumferentially spaced relationship, within the exhaust section of the pathway, respectively coupled to the controller. Each of the dual-immersion thermocouple probes sends respective first and second sensed temperature signals to the controller. The controller identifies an outboard-transverse flame migration in the combustion gas pathway when at least one of the respective second sensed temperatures exceeds at least one of the first sensed temperatures

[0010] The respective features of the exemplary embodiments of the invention that are described herein may be applied jointly or severally in any combination or sub- combination.

BRIEF DESCRIPTION OF DRAWINGS

[0011] The exemplary embodiments of the invention are further described in the following detailed description in conjunction with the accompanying drawings, in which: [0012] FIG. 1 is a fragmentary, axial cross section of an aeroderivative turbine engine, which incorporates an embodiment of the flame migration detection and control system of the present invention;

[0013] FIG. 2 is a radial cross section of the engine, taken along 2-2 of FIG. 1;

[0014] FIG. 3 is an axial schematic view showing outboard-transverse flame migration in an aeroderivative turbine engine that does not incorporate the flame migration detection and control system of the present invention;

[0015] FIG. 4 is an axial schematic view showing outboard-transverse flame migration in the aeroderivative turbine engine of FIG. 1 that incorporates at least one dual-immersion thermocouple of the flame-migration detection portion of the control system of the present invention;

[0016] FIG. 5 is a schematic diagram of the flame-migration detection portion of the control system of the present invention; and

[0017] FIG. 6 is an axial cross-sectional view of a dual-immersion thermocouple, which is constructed in accordance with an embodiment of the present invention.

[0018] To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. The figures are not drawn to scale.

DESCRIPTION OF EMBODIMENTS

[0019] During operating engine studies, local temperature of exhaust gas proximate the outer circumferential periphery of the combustion gas pathway and spatial orientation of the combustion flame front in were monitored. During monitoring, it was determined that locally increasing temperature proximate the outer circumferential periphery of the annular profile, combustion gas pathway correlated with observed, outboard-transverse flame migration. Flame migration should not have occurred under normal operating conditions. It was determined that damage to components forming the outer circumferential periphery of the annular profile, combustion gas pathway in examined aero derivative turbine engines was attributable to the outboard-transverse flame migration. The high outward exhaust gas temperature caused several observed structural overheating problems in the engine, including, among others, premature failure of seal segments, erosion of turbine blades, and‘Z’ notch, shroud-interlock, abutment surfaces. In addition to possible engine damage, the outboard flame traverse resulted in lower average, core-exhaust temperature measurement by existing thermocouples that were oriented approximately at the radial midline of the annular profile, exhaust gas pathway, which lowered engine operating efficiency.

[0020] Through further investigation, it was determined that the traverse flame shift was attributable to liquid dropout, heavy hydrocarbons in the fuel gas used to power the engine that exceeded fuel dryness and contamination specifications for normal engine operation. For example, fuel dryness specifications require sampled fuel gas temperature to be at least 20°C above dew point. Contamination specifications require fuel particulate filtration to 5 -micron nominal, and 20-micron absolute standards. Heavy hydrocarbon liquids in fuel gas exceeding the temperature dew point quality specification caused the combustion zone to be skewed, moving the peak combustion temperatures outwards in the combustor. Nozzles in combustor burners of the engines are often designed to give a balanced mass flow of fuel gas across the engine’s combustion chamber(s), through incorporation of matrices of asymmetrical nozzle holes. However, fuel flow of each nozzle varies with fuel composition. Given the likelihood that fuel composition changes with different fuel sources and changes in atmospheric temperature and humidity conditions, it is not always practical to select different engine burner configurations in anticipation of future changes in fuel composition.

[0021] The inventors discovered that by altering the fuel/air mixture combusted by the engine, they could re-center the combustion-gas flame front without resorting to use of different burner configurations for different fuel compositions. Their solution to avoid engine damage in the outer circumferential periphery of the annular, combustion gas pathway was to monitor the exhaust gas temperature, and alter the fuel/air mixture (FAM) to re-center the flame in the pathway when monitored temperature proximate the outer circumferential periphery exceeded monitored temperature at the center of the pathway. The flame migration and detection system embodiments disclosed herein reduce likelihood of overheating engine components in the outer circumferential periphery of the annular, combustion gas pathway.

[0022] Exemplary embodiments of the invention are utilized to re-center outboard- transverse flame migration in an annular profile, combustion gas pathway of aeroderivative turbine engines. Flame migration is detected with a dual-immersion thermocouple probe. A first thermocouple in the probe is oriented radially midway between inner and outer circumferential surfaces that define the pathway, and second thermocouple in the probe is oriented nearer to the outer circumferential surface of the pathway. A controller detects outboard-transverse flame migration in the combustion gas pathway, when the second thermocouple temperature exceeds the first thermocouple temperature. An engine control system, separately coupled to or incorporated within the controller, mitigates flame migration by altering fuel/air mixture burned by the burner(s) in the combustion gas pathway.

[0023] The aeroderivative turbine engine 10 of FIGs. 1 and 2 is of known design, and includes a compressor section 12, a combustion section 14, and turbine section 16, a power turbine section 18, and an exhaust section 19 downstream of the turbine section. The exhaust section 19 includes an inter-turbine duct (ITD) 20 between the turbine section 16 and the power turbine section 18, and extends downstream of the power turbine section 18 to an exhaust stack. An annular profile, combustion gas pathway (pathway) 22 is radially bounded by inner 24 and outer 26 circumferential surfaces. Exemplary turbine seal segments 28 form part of the outer circumferential surface 26 of the pathway 22. The pathway 22 extends axially from the combustion section 14, through the turbine section 16 and its alternating rows of stator vanes 29 and turbine blades 30, and incorporates the exhaust section 19, including the ITD 20. The pathway 22 defines an annular centerline 27, having a radial height corresponding to approximately half the blade height H_B of the turbine blade 30.

[0024] The exemplary flame migration detection and control system 31 of FIGs. 1-6 includes a plurality of 17 dual-immersion thermocouple probes 32, oriented at equally spaced, circumferential positions in the inter-turbine duct 20 of the exhaust section 19 of the pathway 22, axially downstream of a last row of stator vanes 29 or turbine blades 30. In some embodiments, the flame migration detection and control system has as few as one dual-immersion thermocouple probe 32. In other embodiments, the flame migration detection and control system has any desired plurality of such probes. Probe locations are notated herein as X, where X is an integer (e.g., 1-17) that designates the probe circumferential position. Each probe 32 has a first thermocouple 34 that is oriented at location A, radially between the inner 24 and outer 26 circumferential surfaces of the pathway 22, generally proximate the annular centerline 27. The first thermocouple 34 generates and sends a first signal SXA that is proportional to local exhaust gas temperature Tl at location A. The probe 32 has a second thermocouple 36 that is oriented at location B nearer to the outer circumferential surface 26 of the pathway 22. The second thermocouple 36 generates and sends a second signal SXB that is proportional to local exhaust gas temperature T2 at location B.

[0025] The flame migration detection and control system 31 has a controller 38, separately coupled to each of the first 34 and second 36 thermocouples of each of the plurality X of thermocouple probes 32, for receiving the respective, separate first SXA and second SXB signals generated by them. The controller 38 correlates the received, respective, first SXA and second SXB thermocouple signals with respective local exhaust gas temperatures Tl and T2 in the combustion gas pathway 22, proximate the respective thermocouple locations A and B. The controller 38 does not average the received signals SA and SB and does not average the temperatures Tl and T2 for any individual thermocouple probe 32, as both of those separate temperatures are utilized by the flame migration detection and control system 31 to detect flame front migration within the annular, combustion gas pathway 22. As will be explained in detail hereafter, the controller 38 identifies outboard-transverse flame migration, in various permutations, when the second sensed temperature T2 exceeds the first sensed temperature Tl at any one or more of the circumferential locations X of the probes 32.

[0026] The controller 38 is of known construction; it incorporates a processor 39A, which accesses and executes a non-transient instruction set, resident in software modules that are stored in a non-volatile memory device 39B. While reference to an exemplary controller 38 platform architecture and implementation by software modules executed by the processor 39A, it is also to be understood that exemplary embodiments of the invention may be implemented in various forms of hardware, software, firmware, special purpose processors, or a combination thereof. Preferably, aspects of the invention embodiments are implemented in software as a program tangibly embodied on the program-storage memory device 39B. The program may be uploaded to, and executed by, a machine comprising any suitable architecture. Preferably, the machine is implemented on a computer platform having hardware such as one or more central processing units (CPU), a random access memory (RAM), and input/output (I/O) interface(s). The computer platform also includes an operating system and microinstruction code. The various processes and functions described herein may be either part of the microinstruction code or part of the program (or combination thereof) which is executed via the operating system. In addition, various other peripheral devices may be connected to the computer/controller platform. In the embodiments of FIGs. 1 and 2, the controller 38 incorporates functions of a plant control system (PCS) 41A, a safety instrumented system (SIS) 41B, and an engine control system (ECS) 42.

[0027] FIGs. 3 and 4 compare, respectively, combustion gas temperature profile and temperature monitoring in an exemplary annular, exhaust-gas pathway 22 with a known, single-immersion thermocouple probe 44 and with an embodiment of a dual immersion thermocouple probe 32 of the present invention. Each of the figures shows schematically a centered combustion-gas flame front 50, where the highest flame temperature T_A is oriented radially at approximately fifty percent of the turbine blade height H_b, in conformance with engine operational specifications_. This centered flame-temperature location T_A corresponds to approximately the annular centerline 27 of the pathway 22. Combustion gas, outbound transverse-flame migration is illustrated with the dashed line 52 in both figures. The maximum temperature TB* of the transverse-flame migration, combustion-gas front 52 is now closer to the blade tip and outer circumferential surface of the combustion gas pathway 22 (shown for illustrative purposes only at approximately 80% H_B). The outwardly directed, maximum temperature T_B* of the combustion gas, flame-migration pattern 52 may overheat components within the outer circumferential surface of the combustion gas pathway 22.

[0028] The single-immersion thermocouple probe 44 of FIG. 3 is not capable of determining the maximum temperature T_B* of the transverse-flame migration, combustion-gas front 52. Its single thermocouple 46 detects temperature T_A*, which is actually T_B* - (X+Y). A temperature monitoring controller reading T_A* would continue to operate the engine under“normal” operating conditions, because that temperature is below the maximum operating temperature allowable under the established engine specification. There is also the risk that the monitoring controller, reading T_A* will trigger a fictitious signal for the fuel control system of the engine to increase fuel flow in the fuel air mixture (FAM) to increase the temperature to meet the required set-point specification temperature T_A. In fact, the actual maximum operating temperature T_B* in the migrated, combustion-gas flame front 52 exceeds temperature specifications T_B for the outer circumferential surfaces of the engine’s combustion gas pathway. This could lead to over-firing of the engine, leading to overheating of the turbine and reducing the life of components.

[0029] In contrast, the dual-immersion thermocouple probe 32 of FIG. 4 monitors all of the actual temperatures T_A and T_B of the centered, combustion-gas flame front 50 and the corresponding actual temperatures T_A* and T_B* of the migrated, combustion- gas flame front 52, with the respective thermocouples 34 (thermocouple signal SXA) and 36 (thermocouple signal SXB). Thus, the controller 38 ascertains that temperature T_B* exceeds the specification temperature T_B by Z degrees, and that Temperature TA* is X degrees lower than the specification temperature TA. [0030] A schematic diagram and structure of an exemplary dual-immersion, thermocouple probe 32 are shown in FIGs. 5 and 6. Radial orientation of the probe 32 relative to the annular, exhaust-gas pathway 22 is shown in FIG. 2. The probe 32 has an elongated, hollow probe housing 60, for retention of the first 34 and second 36 thermocouples. A housing base 62 is coupled to components in the engine that form the outer circumferential surface 26 of the of the annular, exhaust-gas pathway 22. A distal tip 64 of the housing 60 is oriented approximately radially midway between the inner 24 and outer 26 circumferential surfaces of the pathway— generally slightly below the annular centerline 27. In some embodiments, outer envelope dimensions of the dual-immersion probes 32 matches those of existing single-thermocouple probes, for easy substitution in existing aeroderivative engine designs during initial manufacture or in subsequently scheduled maintenance service.

[0031] The probe housing 60 has lower 66 A and upper 66B windows formed in its outer peripheral surface, for exposure of the respective, internally contained, first 34 and second 36 thermocouples to exhaust gas. The lower housing window 66A is oriented within the exhaust gas pathway 22 at approximately the annular centerline 27, so that the first thermocouple 34 senses local temperature at the same centerline location. As previously mentioned, the thermocouple 34 generates a first signal SXA that is proportional to its local temperature Tl at the annular centerline 27. The upper housing window 66B is oriented within the exhaust gas pathway 22 proximate the housing base 62, so that the second thermocouple 36 senses local temperature closer to the outer circumferential surface 26 of the of the annular, exhaust-gas pathway 22. As previously mentioned, the second thermocouple 36 generates a second signal SXB that is proportional to its local temperature T2.

[0032] Referring to FIGs. 4 and 6, a design goal for relative orientation of the first 34 and second 36 thermocouples within the length of the housing 60 is to enable the sensing system 31 to detect sufficient temperature differential between Tl and T2, so that the controller 38 can correlate increasing relative higher temperature shift in T2 relative to Tl with corresponding physical shift of the combustion flame contours within the annular, exhaust gas pathway from a relatively centered position 50 to a more outward-transverse position 52. In the exemplary embodiment of FIGs. 4 and 6, the first thermocouple 34 is oriented at approximately 50% of the length of the turbine blade H_B, and the second thermocouple 36 is oriented at approximately 80% of H_B.

[0033] As noted previously, empirical studies of operating engines identified fuel quality deviations from fuel quality specifications as a cause of transverse-flame migration, such as the migration 52 of FIGs. 3 and 4. Ability of the flame migration and detection system 31 to monitor the Temperatures Tl and T2, at the locations A and B in the combustion gas pathway 22, provides information needed to prevent overheating of the engine 10 components that form the pathway’s outer circumferential surface 26.

[0034] Referring to FIGs. 1-6, the exemplary embodiment of the flame migration and detection system 31, illustrated therein, orients at least one dual-immersion thermocouple probe 32 in the inter-turbine duct 20 of the exhaust section 19 of the combustion gas pathway 22. Multiple thermocouple probe 32 embodiments are discussed below. Operation of the flame migration and detection system 31 with one exemplary thermocouple probe 32 is now described. The first thermocouple 34 of the dual-immersion thermocouple probe 32 is oriented radially midway between the inner 24 and outer 26 circumferential surfaces of the pathway. The second thermocouple 36 of the probe 32 is oriented nearer to the outer circumferential surface 26 of the pathway 22. The first thermocouple 34 sends a first signal SXA to the controller 38, which is indicative of its locally sensed temperature Tl in the exhaust gas pathway 22 at location A. The second thermocouple 36 sends a second signal SXB to the controller 38, which is indicative of its locally sensed temperature T2 in the exhaust gas pathway 22 at location B.

[0035] The controller 38 receives and correlates the respective thermocouple signals SXA and SXB with local exhaust gas temperature Tl and T2 at each respective thermocouple location in the combustion gas pathway 22. Once the controller 38 determines the respective temperatures Tl and T2, it can identify an outboard- transverse flame migration (e.g., combustion flame front 52 of FIGs. 3 and 4) in the combustion gas pathway 22, when the second temperature T2 exceeds the first temperature T 1.

[0036] In some embodiments, the controller 38 determines when either of Tl or T2 exceeds a maximum designated temperature and enunciates the information to the flame migration and detection system 31, and/or to other operating and control systems of the engine 10 to which it is coupled, such as the engine control system 42. In some embodiments, when Tl or T2 exceed the maximum temperature, the engine control system 42 causes the fuel injector(s) 40 to alter the fuel/air mixture burned in the combustion section 14 of the engine 10, such as by varying the fuel supply rate signal FX sent to the respective injector(s). Air/fuel mixture is altered to re-center the identified outboard-transverse flame migration (e.g., the migrated flame contours 52 of FIGs. 3 and 4) in the combustion gas pathway 22, radially towards the first thermocouple 34 of the dual-immersion thermocouple probe 32, so that they achieve the centered profile of the flame contours 50.

[0037] In other embodiments, the engine control system 42 regulates fuel/air mixture burned in the combustion section 14 by relying on the temperature reading Tl, but switches regulation, relying on the second temperature T2, when the latter exceeds Tl. In some embodiments, the engine control system 42 switches regulation control from Tl to T2 when the latter exceeds Tl by a designated margin or range (e.g., do not switch to T2 unless it exceeds Tl by 20° C). In some embodiments, the engine control system regulates fuel/air mixture burned in the combustion section 14, by relying on the higher of either Tl or T2.

[0038] In some embodiments, the controller 38 samples simultaneously and repetitively in real time, and separately averages sampling windows of pluralities of the respective first signals SXA and second signals SXB, generated respectively by the first thermocouple 34 and the second thermocouple 36. The averages of the respective signals SXA and SXB are used to determine the respective first and second temperatures Tl and T2. [0039] In the embodiment of FIGs. 1, and 2, there are 17 circumferentially spaced, dual-immersion thermocouple probes 32. In some embodiments, the controller 38 receives all of the thermocouple signals S1A-S17A of all 17 of the first thermocouples 34 in each of the probes 32. In some embodiments, the controller 38 receives all of the thermocouple signals S1B-S17B of all 17 of the second thermocouples 36 in each of the probes 32. Ideally, when the controller 38 receives all 34 of the separate thermocouple signals SXA and SXB, it can determine the local temperatures Tl and T2 at each circumferential location within the exhaust gas pathway 22. Then, the controller 38 optionally can determine whether Tl or T2 at any of the circumferential locations is indicative of transverse flame front migration towards the outer circumferential surfaces 26 of the combustion gas pathway 22.

[0040] If the controller 38 architecture does not have sufficient communications or processing bandwidth to process all 34 of the signals SXA and SXB, some of the respective groups of signals are averaged separately to determine Tl and/or T2. In some embodiments, the controller receives and processes each of the Tl temperatures sensed by each of the first thermocouples 34 of the probes 32, but averages clusters of the T2 temperatures sensed by each of the second thermocouples 36. In this way, the controller 38 and the engine control system 42 regulate fuel/air mixture burned in the engine 10 under normal operating conditions with all of the circumferential Tl temperatures. If transverse flame migration in the combustion gas pathway 22 is detected through an excessive, averaged T2 temperature, the engine control system 42 can initiate fuel/air regulation alterations needed to re-center the flame in the pathway.

[0041] Advantageously, the thermocouple probes 32 are sized to conform to mounting interface specifications of existing single-immersion thermocouple probes (e.g., probe 44), for retrofitting in existing engine designs. For example, if there are eight single-immersion thermocouple probes in an existing engine design, eight of the dual-immersion probes 32 are substituted for them. If the existing controller 38 architecture is not capable of receiving all potential signals SXA and SXB generated by the new thermocouple probes 32, some of the separate signals can be averaged, so that the controller can process separately averaged Tl and T2 temperatures.

[0042] It is to be understood that, because some of the constituent system components, such as the controller 38, and/or the plant control system 41 A, and/or the safety instrumented system 41B, and/or the engine control system 42 and method steps depicted in the accompanying figures are preferably implemented in software, the actual connections between the system components (or the process steps) may differ depending upon the manner in which the exemplary embodiments are programmed. Specifically, any of the computer platforms or devices may be interconnected using any existing or later discovered networking technology; all may be connected through a larger network system, such as a corporate network, metropolitan network or a global network, such as the Internet. For example, as noted above, the controller 38 may incorporate one or more of the engine control system 42, the plant control system 41 A, or the safety instrumented system 41B.

[0043] Although various embodiments that incorporate the invention have been shown and described in detail herein, others can readily devise many other varied embodiments that still incorporate the claimed invention. The invention is not limited in its application to the exemplary embodiment details of construction and the arrangement of components set forth in the description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. In addition, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of“including,”“comprising,” or“having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless specified or limited otherwise, the terms“mounted”,“connected”,“supported”, and“coupled” and variations thereof are to be interpreted broadly; they encompass direct and indirect mountings, connections, supports, and couplings. Further,“connected” and“coupled” are not restricted to physical, mechanical, or electrical connections or couplings.

Claims

CLAIMS What is claimed is:

1. A method for detecting outboard-transverse flame migration in an aeroderivative turbine engine, comprising:

providing an aeroderivative turbine engine (10) having an annular profile, combustion gas pathway (22), radially bounded by inner (24) and outer (26) circumferential surfaces; the pathway extending axially from a combustion section (14), through a turbine section (16), and an exhaust section (19);

orienting a dual-immersion thermocouple probe (32) in an inter-turbine duct (20) of the exhaust section of the combustion gas pathway, so that a first thermocouple (34) in the probe is oriented radially midway between the inner and outer circumferential surfaces of the pathway, and second thermocouple (36) in the probe is oriented nearer to the outer circumferential surface thereof;

sending separate, respective first (SA) and second (SB) signals from the first and second thermocouples to a controller (38), which receives and correlates the respective thermocouple signals with local exhaust gas temperature at each respective thermocouple location in the combustion gas pathway;

determining, with the controller, a first temperature of the exhaust gas, using the first signal sent by the first thermocouple;

determining, with the controller, a second temperature of the exhaust gas, using the second signal sent by the second thermocouple; and

identifying an outboard-transverse flame migration in the combustion gas pathway, with the controller, when the second temperature exceeds the first temperature.

2. The method of claim 1, further comprising:

determining, with the controller (38), whether either of the first or second temperatures exceeds a maximum temperature; and

enunciating, with the controller, when either of the first or second temperatures exceeds the maximum temperature.

3. The method of claim 1, further comprising:

altering fuel/air mixture burned in the combustion section (14), with an engine control system (42) coupled to the controller, when the controller determines that either of the first or second temperatures exceeds the maximum temperature.

4. The method of claim 1, further comprising:

an engine control system (42), coupled to the controller (38), regulating fuel/air mixture burned in the combustion section (14) based on the first temperature; and

the engine control system switching regulation of fuel/air mixture burned in the combustion section, based on the second temperature, when it exceeds the first temperature.

5. The method of claim 4, the engine control system (42) switching regulation of fuel/air mixture burned in the combustion section (14), based on the second temperature, when it exceeds the first temperature by a designated temperature margin.

6. The method of claim 1, further comprising:

an engine control system (42), coupled to the controller (38), regulating fuel/air mixture burned in the combustion section (14) based on both of the first and second temperatures; and

the engine control system altering fuel/air mixture burned in the combustion section based on the higher of the first or the second temperature.

7. The method of claim 1, the controller (38), repetitively in real time, sampling simultaneously, and averaging pluralities of first (SA) and second (SB) signals to determine the respective first and second temperatures.

8 The method of claim 1, further comprising an engine control system (42), coupled to the controller (38), altering the outboard-transverse flame migration in the combustion gas pathway (22) identified by the controller, by altering fuel/air mixture burned in the combustion section (14).

9. The method of claim 1, further comprising an engine control system (42), coupled to the controller (38), re-centering the identified outboard-transverse flame migration in the combustion gas pathway (22), radially towards the first thermocouple (34), by altering fuel/air mixture burned in the combustion section (14).

10. The method of claim 1, further comprising:

orienting a plurality of the dual-immersion thermocouple probes (32) in circumferentially spaced relationship, within the inter-turbine duct (20) of the exhaust section (19) of the pathway (22), so that each respective first thermocouple in each respective probe is oriented radially midway between the inner (24) and outer (26) circumferential surfaces of the pathway, and each respective second thermocouple (36) in each respective probe is oriented nearer to the outer circumferential surface thereof;

sending separate, respective first (SXA) and second (SXB) signals from each of the first and second thermocouples in each of the respective dual-immersion thermocouple probes to the controller (38), which receives and correlates the respective thermocouple signals with respective local, exhaust gas temperatures in the combustion gas pathway;

determining, with the controller, respective first temperatures of the exhaust gas, using the respective first signal sent by each of the respective first thermocouples; determining, with the controller, respective second temperatures of the exhaust gas, using the respective second signal sent by each of the respective second thermocouples; and

identifying an outboard-transverse flame migration in the combustion gas pathway, with the controller, when at least one of the respective second temperatures exceeds at least one of the first temperatures.

11. The method of claim 10, further comprising the controller (38) averaging at least two of the respective plurality of first temperatures, and/or the respective plurality of second temperatures, and identifying an outboard-transverse flame migration in the combustion gas pathway (22), using the averaged first temperature, or the averaged second temperature, or both of the averaged first and second temperatures.

12. The method of claim 10, further comprising the controller (38) averaging all of the respective plurality of second temperatures, and identifying an outboard- transverse flame migration in the combustion gas pathway, when the averaged second temperature exceeds at least one of the first temperatures.

13. An outboard-transverse flame migration detection and control system for an aeroderivative turbine engine, comprising:

an aeroderivative turbine engine (10) having an annular profile, combustion gas pathway (22), radially bounded by inner (24) and outer (26) circumferential surfaces, the pathway extending axially from a combustion section (14), through a turbine section (16) including alternating rows of turbine blades (30) and stator vanes (29), and an exhaust section (19);

a dual-immersion thermocouple probe (32), oriented in an inter-turbine duct (20) of the exhaust section of the pathway, axially downstream of a last row of stator vanes or turbine blades, having:

an elongated probe housing (60), having: a housing base (62) coupled to the outer circumferential surface of the pathway, and a distal housing tip (64) oriented radially midway between the inner and outer circumferential surfaces of the pathway; a first thermocouple (34) in the probe housing proximate the housing tip, for generating a first signal (SA) that is proportional to its local temperature; and

a second thermocouple (36) in the probe housing proximate the housing base, for generating a second signal (SB) that is proportional to its local temperature;

a controller (38), separately coupled to the first and second thermocouples, for receiving the respective, separate first and second signals sent there from, the controller correlating the received, respective, first and second thermocouple signals with exhaust gas temperatures in the combustion gas pathway proximate the respective thermocouples;

the controller identifying outboard-transverse flame migration, when the second sensed temperature exceeds the first sensed temperature.

14. The system of claim 13, further comprising an engine control system (42) coupled to the controller, the engine control system regulating fuel/air mixture burned in the combustion section (14) based on the first temperature; and switching regulation of fuel/air mixture burned in the combustion section, based on the second temperature, when it exceeds the first temperature.

15. The system of claim 13, further comprising an engine control system (42) coupled to the controller (38), the engine control system regulating fuel/air mixture burned in the combustion section (14) based on the higher of the first or the second temperature.

16. The system of claim 13, further comprising:

a plurality of the dual-immersion thermocouple probes (32), in circumferentially spaced relationship, within the inter-turbine duct (20) of the exhaust section (19) of the pathway (22), so that each respective first thermocouple (34) in each respective probe is oriented radially midway between the inner (24) and outer (26) circumferential surfaces of the pathway, and each respective second thermocouple (36) in each respective probe is oriented nearer to the outer circumferential surface thereof;

the controller (38) receiving separate, respective first (SXA) and second (SXB) signals from each of the first and second thermocouples in each of the respective dual-immersion thermocouple probes, and correlating the respective thermocouple signals with respective local, exhaust gas temperatures in the combustion gas pathway;

the controller determining respective first temperatures of the exhaust gas, using the respective first signal sent by each of the respective first thermocouples; the controller determining respective second temperatures of the exhaust gas, using the respective second signal sent by each of the respective second thermocouples; and

the controller identifying an outboard-transverse flame migration in the combustion gas pathway when at least one of the respective second temperatures exceeds at least one of the first temperatures.

17. The system of claim 16, the controller (38) averaging at least two of the respective plurality of first temperatures, and/or the respective plurality of second temperatures, and identifying an outboard-transverse flame migration in the combustion gas pathway (22), using the averaged first temperature, or the averaged second temperature, or both of the averaged first and second temperatures.

18. The system of claim 16, the controller (38) averaging all of the respective plurality of second temperatures, and identifying an outboard-transverse flame migration in the combustion gas pathway (22), when the averaged second temperature exceeds at least one of the first temperatures.

19. The system of claim 18, further comprising an engine control system (42) coupled to the controller (38), the engine control system regulating fuel/air mixture burned in the combustion section (14) based on the higher of the first or the averaged second temperature.

20. The system of claim 16, further comprising an engine control system (42) coupled to the controller (38), the engine control system regulating fuel/air mixture burned in the combustion section (14) based on the highest of the entire first temperatures or the entire second temperatures.