Gas turbine engine with flame failure protection and method of operating the same

Abstract

This invention relates to a gas turbine engine with flame failure protection and a method of operating the same. Specifically, a gas turbine engine includes a combustor assembly (5) having multiple burners (13, 14), an exhaust frame (8) provided with multiple radial struts (20), and an exhaust diffuser (10) extending downstream of the exhaust frame (8) along a longitudinal axis (A). Multiple temperature sensors (23, 25) are located within the exhaust diffuser (10) downstream of the exhaust frame (8) and struts (20) at corresponding angular and radial positions relative to the longitudinal axis (A). A control system (3) is configured to operate based on the response of the temperature sensors (23, 25) and a temperature threshold (T). TH ( ) and redundant logic to detect flame failure at one or more locations in the burner (13, 14).

Description

[0001] Cross-references to related applications This patent application claims priority to European Patent Application No. 20215655.0, filed on 18 December 2020, the entire disclosure of which is incorporated herein by reference. Technical Field

[0002] The present invention relates to a gas turbine engine having flame failure (or interruption) protection based on exhaust gas temperature and to a method of operating the gas turbine engine. Background Technology

[0003] As is well known, flame detection is a critical issue in gas turbine engines because accidental flameout at one or more burners can lead to efficiency losses and, in the worst case, cause unburned fuel in the exhaust and a possible explosion.

[0004] In annular combustors, flame monitoring is often performed using optical flame detectors, which consist of an optical waveguide facing the flame region and an image detector coupled to the waveguide. The aforementioned monitoring systems meet the requirements set by standards and are effective in preventing hazardous conditions that could result in a continuous fuel supply in the absence of a flame; however, they are costly to implement, especially when operating gas turbine engines with canister or canister-annular combustor structures. This is particularly true considering the harsh operating conditions of components exposed to hot combustion gases. Relatively rapid aging of hardware components can lead to false negative (or misjudgment) detections, meaning that the flame detector's response indicates the flame is extinguished when it is actually present. While such events typically do not pose an imminent threat to the structural integrity of the gas turbine engine, they can trigger unnecessary equipment trips and, in any case, require relatively frequent maintenance, accompanied by a significant increase in costs.

[0005] Another proposed approach is to use dedicated temperature sensors mounted in the exhaust frame of a gas turbine engine, located between the least expanded stage and the exhaust strut, to monitor flames based on the circumferential temperature distribution of the exhaust gases. This system relies on the increased exhaust gas temperature diffusion in the event of one or more burner failures, and the positioning of the temperature sensors directly downstream of the turbine aims to reduce exhaust gas mixing and maximize the positional correlation between the burners and the temperature sensors. However, this solution requires not only the installation of an additional set of temperature sensors but also corresponding support structures to hold the temperature sensors in place within the exhaust gas flow within the gas turbine engine's exhaust frame. Electrical connections are also required. While providing the additional set of temperature sensors is generally not a problem in itself, positioning and electrical connections can be, as they require structural intervention in the exhaust system. On the other hand, known flame monitoring systems based on exhaust temperature suffer from potential false positives (or false negatives) because a temperature sensor failure may not be distinguished from a flame absence at the burner and will produce similar results based on the detected temperature diffusion. Summary of the Invention

[0006] Therefore, the object of the present invention is to provide a gas turbine engine and a method of operating a gas turbine engine, which allows for overcoming or at least mitigating the limitations described above.

[0007] According to the present invention, a gas turbine engine is provided, comprising: A burner assembly comprising multiple burners; The exhaust frame is provided with multiple radial struts; An exhaust diffuser extends downstream of the exhaust frame along the longitudinal axis; Multiple temperature sensors are located within the exhaust diffuser, downstream of the exhaust frame and struts, and arranged at corresponding angular and radial positions relative to the longitudinal axis. A control system configured to detect flame failure at one or more points in the burner based on the response of a temperature sensor, a temperature threshold, and redundant logic.

[0008] The size of the exhaust diffuser provides more opportunities to adapt temperature sensors to the required support and connections. Therefore, not only are sensors arranged in the exhaust diffuser generally not critical to the design of the gas turbine engine and have no significant structural impact, but installation and maintenance are also simplified. Furthermore, temperature sensors can be placed in the exhaust diffuser also for control purposes, as exhaust temperature is an indicator of the power delivered by the gas turbine engine. Thus, it is possible to either utilize a single temperature sensor array for both control and flame monitoring, or to provide separate, dedicated temperature sensor arrays sharing support and connection paths. Sensor arrays can also have specifically selected characteristics based on their function.

[0009] Using redundant logic in a group of adjacent temperature sensors avoids, or at least significantly reduces, the risk of false positive detection of flame failure. Indeed, the failure of a single temperature sensor results in a low temperature reading and fails to distinguish the effects of flame failure at one point in the burner. However, temperature sensors can be easily placed according to design preferences, such that cold spots originating from the off burner affect the entire group of burners due to mixing in the hot gas path and upstream of the exhaust diffuser. Because the control system uses redundant logic to evaluate temperature sensors in groups, the effects of a single temperature sensor failing to meet the flame presence criterion can be compensated for by other temperature sensors in the group. In other words, if most temperature sensors in a group meet the flame presence criterion according to the redundant logic (e.g., the sensor response is above a temperature threshold), a potential temperature sensor below the flame presence criterion can be correctly identified as faulty. Therefore, unnecessary equipment shutdowns can be avoided without affecting the safe operation of the gas turbine engine.

[0010] According to one aspect of the invention, the temperature sensor includes a first temperature sensor having a faster first response and a second temperature sensor having a more accurate second response, wherein the control system is configured to determine flame failure at one or more locations in the burner based on the first response of the first temperature sensor.

[0011] A dedicated first temperature sensor for flame monitoring can be added to a second temperature sensor already in place for gas turbine engine control. Aside from sharing a support and connection structure, the characteristics of the first and second temperature sensors can be individually optimized based on their respective functions. The first temperature sensor can be designed for rapid response, as rapid detection of flame failure is required to ensure timely triggering of protective measures and ultimately ensure the safe operation of the gas turbine engine. Alternatively, for load control purposes, the accuracy requirement for the second temperature sensor takes precedence over rapid response, as the typical transient response of a gas turbine engine is not particularly demanding in this context and it is compatible with most commonly used sensors, such as thermocouples.

[0012] According to one aspect of the invention, the exhaust diffuser includes a housing and a support rod extending radially inward from the housing, wherein a first temperature sensor and a second temperature sensor are arranged on the respective support rod.

[0013] In practice, the first temperature sensor is mounted on the same support that has been provided for the second temperature sensor, which is dedicated to load control, without increasing the design complexity of the gas turbine engine.

[0014] According to one aspect of the invention, the support rods are located at a common axial position and are circumferentially distributed around a longitudinal axis, and at least some of the support rods each hold a corresponding first temperature sensor among the first temperature sensors and a corresponding second temperature sensor among the second temperature sensors. Preferably, all the support rods holding a first temperature sensor of the first temperature sensor also each hold a second temperature sensor of the second temperature sensor.

[0015] Therefore, optimal positioning of the first temperature sensor can be achieved to ensure that even at a single burner, the group of first sensors is always affected by the cold spot caused by flame extinction in the exhaust gas.

[0016] According to one aspect of the invention, each of the support rods holding a first temperature sensor in the first temperature sensor also holds a second temperature sensor in the second temperature sensor.

[0017] Therefore, the first temperature sensor is installed using only the existing structure.

[0018] According to one aspect of the invention, the control system is configured to detect flame failure based on M-out-of-N redundant logic in a group of adjacent first temperature sensors, wherein N is the number of first temperature sensors in each group, and M is an integer less than or equal to N-1.

[0019] One example is a 2 out of 3 (2oo3) logic, where flame failure is detected only if two or three of the three first temperature sensors fail to meet the flame presence criterion. A flame failure at one burner nozzle is reflected in a cold spot that spreads along the hot gas path and exhaust diffuser, affecting the adjacent group of first temperature sensors, here three. A poor response from a single first temperature sensor is insufficient to conclude flame failure. Specifically, if no flame failure is detected in the group of first temperature sensors based on the 2 out of 3 redundancy logic, a poor response from a single first temperature sensor can be safely interpreted as a sensor failure. The above can be summarized as NM faulty first temperature sensors and N out of M redundancy logic.

[0020] According to one aspect of the invention, the control system is configured to detect flame failure based on a comparison of a first response of a first temperature sensor with a temperature threshold, wherein the temperature threshold is determined by the average value of the first response of the first temperature sensor and the temperature offset.

[0021] The temperature threshold can be iteratively determined to account for dependencies on the current average temperature, such as with respect to load conditions. Depending on design preferences, the average value can be calculated on a single sample of the first response of the first temperature sensor, as well as over a time period.

[0022] According to the present invention, a method for controlling a gas turbine engine is also provided, the gas turbine engine comprising: A burner assembly comprising multiple burners; The exhaust frame is provided with multiple radial struts; The exhaust diffuser extends downstream of the exhaust frame along the longitudinal axis. The method includes: Multiple temperature sensors are provided in the exhaust diffuser downstream of the exhaust frame and struts at corresponding angular and radial positions relative to the longitudinal axis; Flame failure at one or more points in the burner is detected based on the response of the temperature sensor, temperature thresholds, and redundant logic. Attached Figure Description

[0023] The invention will now be described with reference to the accompanying drawings, which illustrate some non-limiting embodiments of the invention, wherein: - Figure 1 This is a simplified block diagram of a gas turbine engine according to an embodiment of the present invention; - Figure 2 yes Figure 1 A simplified cross-sectional side view of a gas turbine engine; - Figure 3 yes Figure 1 gas turbine engine along Figure 2 Front view of the section cut by plane III-III; - Figure 4 yes Figure 1 A schematic diagram of the burners in a gas turbine engine, which are divided into groups for flame monitoring purposes; - Figure 5 and Figure 6 This shows the relationship between different operating conditions and Figure 1 A diagram illustrating the number of gas turbine engines. Detailed Implementation

[0024] See Figure 1 The number 1 defines a gas turbine engine, which provides a control system 3 and includes a compressor 4, a combustor assembly 5, a turbine 6, an exhaust frame 8, and an axial exhaust diffuser 10, all of which extend about a longitudinal axis, which is located in... Figure 2 The diffuser is represented by A. In one embodiment (not shown), the diffuser may be a radial diffuser. The gas turbine engine also includes a fuel supply system 15 controlled by the control system 3.

[0025] Compressor 4 ( Figure 1The compressor 4 is fed a stream of compressed air drawn from the outside to the first burner assembly 5. The air supply to the compressor 4 is controllable by the control system 3 by adjusting the orientation of the inlet guide vanes 11 of the compressor 4.

[0026] In one embodiment ( Figure 2 In this configuration, the first burner assembly 5 is a sequential burner and includes a plurality of canister burners 12 circumferentially distributed around a longitudinal axis A. Each canister burner 12 includes a corresponding first-stage burner 13 and a second-stage burner 14. However, the burner assembly may be of a different type, such as a single-stage canister or canister-annular burner, or a sequential or single-stage annular burner.

[0027] The canister burner 12 mixes air from the compressor 4 and fuel from the fuel supply system 15 to form a mixture for combustion. The fuel can be gaseous, such as natural gas or syngas, or liquid, such as petroleum gas. The gas turbine engine 1 can be configured to use both different types of fuel, both gaseous and liquid. The fuel supply is controllable by the control system 3 via the fuel supply system 15.

[0028] Turbine 6 receives hot airflow from burner assembly 5 and expands it to extract mechanical work, which is then transmitted to an external user, typically a generator, not shown here.

[0029] Hot gas is then delivered through the exhaust frame 8 and the exhaust diffuser 10. The exhaust frame 8 is positioned directly downstream of the turbine 6 and includes an inner shell 17, an outer shell 18, and multiple struts 20 (e.g., ten). The struts extend radially from the inner shell 17 to the outer shell 18. Figure 3 As shown in the diagram), and evenly spaced in the circumferential direction. One of the struts 20, for example, extends in a vertical plane in the upper portion of the exhaust frame 8, defining an angular position for use with respect to the longitudinal axis A of the gas turbine engine 1. The benchmark.

[0030] The exhaust diffuser 10 extends downstream of the exhaust frame 8 along the longitudinal axis A and includes an inner shell 21 and an outer shell 22, which define a portion of the flow path for exhaust gases.

[0031] The exhaust diffuser 10 also includes multiple temperature sensors, which are thus arranged at corresponding angular and radial positions relative to the longitudinal axis A downstream of the exhaust frame 8 and the strut 20. Specifically, the temperature sensors include a first temperature sensor 23 for flame monitoring purposes and a second temperature sensor 25 for load control (turbine after-temperature or TAT measurement). The first temperature sensor 23 and the second temperature sensor 25 are mounted on a support rod 26 that extends radially inward from the housing 22 at a common axial position, also defining the TAT plane. The support rods 26 are distributed circumferentially and not necessarily in a uniform manner. In one embodiment, each support rod 26 holds a corresponding first temperature sensor 23 and at least one second temperature sensor 25, while special support rods 26 that are longer than the other support rods each hold three second temperature sensors 25. However, it is understood that some of the support rods 26 may hold only the first temperature sensor 23 or the second temperature sensor 25. The first temperature sensor 23 is arranged at a first common radial position at the same first distance from the longitudinal axis A; similarly, the second temperature sensor 25, possibly except those on the longer support rod 26, is arranged at a second common radial position at the same second distance from the longitudinal axis A. In any case, the number, angle, and radial position of the first temperature sensors 23 are selected such that irregularities in the circumferential temperature distribution caused by flame failure (cold spot) at any of the burners 13, 14 affect the corresponding group of adjacent first temperature sensors 23.

[0032] The characteristics of the first response of the first temperature sensor 23 and the second response of the second temperature sensor 25, and in particular, the first and second responses, can be selected based on the specific functions for which they provide temperature sensors. Specifically, the first response of the first temperature sensor 23 (for flame monitoring purposes) is faster than the second response of the second temperature sensor 25, while the second response of the second temperature sensor 25 (for load control purposes) is more accurate than the first response of the first temperature sensor 23.

[0033] Control system 3 is configured to operate gas turbine engine 1 according to received load requests. As defined herein, "control system" should be broadly understood to mean a system that monitors all functions and operations of the gas turbine, including at least control or regulation functions such as load control, determining setpoints and driving actuators to achieve setpoints, primary and secondary frequency control, and protection functions including flame detection and flame failure protection. Specifically, control system may include a first subsystem for control functions and a second subsystem for protection functions.

[0034] The control system 3 determines a setpoint for the gas turbine engine 1 to meet load requests, and based on the determined setpoint and feedback signals from selected sensors and / or detectors, including a second response from the second temperature sensor 25, it drives the inlet guide vanes 11 of the compressor 4 and the fuel supply system 15.

[0035] The control system 3 also performs flame monitoring at either of the burners 13 and 14 based on the first response of the first temperature sensor 23 and redundant logic. Specifically, the control system 3 is configured to detect flame failure based on M redundant logic selected from N in a group of adjacent first temperature sensors 23, where N is the number of first temperature sensors in each group, and M is an integer less than or equal to N-1. In one embodiment, N is 3, M is 2, and the redundant logic is 2 out of 3 logic.

[0036] like Figure 4 The diagram illustrates, in which the first temperature sensor 23 is further identified individually as TS1, ..., TS K The control system 3 defines K groups G1, ..., G2 of N adjacent first temperature sensors 23. K Where K is the total number of the first temperature sensors 23 in the exhaust diffuser 10. Each group G1, ..., G K This includes N corresponding neighboring first temperature sensors 23, and each first temperature sensor 23 belongs to N different groups G1, ..., G2. K In other words, each sensor 23 is connected via the corresponding group G1, ..., G... K Angle position The first component: TS1 is the first component of group G1, which includes first temperature sensors TS1, TS2, and TS3; TS2 is the first component of group G2, which includes first temperature sensors TS2, TS3, and TS4; and so on up to TS. K-1 It is group G K-1 The first component, the group G K-1 Including the first temperature sensor TS K-1 TS K TS1; and TS K It is group G K The first component, the group G K Including the first temperature sensor TS K TS1, TS2.

[0037] The control system 3 is based on the first response of the first temperature sensor 23 and the temperature threshold T. TH The comparison is used to detect flame failure, and the first response includes... Figure 4-6The Chinese characters are labeled T1, ..., T K The corresponding monitoring signal, the temperature threshold is determined by the first response T1, ..., T of the first temperature sensor 23. K The average value and temperature offset ΔT are used to determine the temperature threshold. The temperature threshold can be iteratively updated and calculated, for example, based on the monitoring signals T1, ..., T2 of the first temperature sensor 23. K On a single sample or on samples collected over a period of time.

[0038] Using a 2-out-of-3 logic (typically M-out-of-N), if at least one group G1, ..., G of the first temperature sensor 23 is used... K The first response, specifically the monitoring signals T1, ..., T2 of the two (typically M-1) first temperature sensors 23 in this group. K Below the temperature threshold T TH If the flame failure occurs, the control system 3 detects a flame failure. A flame failure at one of the burners 13 or 14 causes a cold spot, which leads to increased temperature diffusion of the exhaust gas and affects the measurement of the adjacent first temperature sensor 23, causing the measurement to be significantly below the average value. When at least M (two in this embodiment) adjacent first temperature sensors 23 give readings below the temperature threshold T... TH Monitoring signals T1, ..., T K At that time, it recognizes flame failure, but it does not require all first temperature sensors 23 in a group to fail the test. Figure 5 In the example, at the angular position J+1 and J+2 The monitoring signal T from temperature sensor 23 at the location J+1 and T J+2 Below the temperature threshold, and therefore unable to match the temperature threshold T TH A comparison was attempted, but therefore a comparison failed. Group G J and G J+1 Included in angular position J+1 and J+2 Temperature sensors 23 are present at the location, while all other groups contain at most one of them. In fact, group G... J Included in angular position J , J+1 , J+2 Temperature sensor 23 at the location, and group G J+1 Included in angular position J+1 , J+2 , J+3 Temperature sensor 23 at the location. Therefore, based on the redundancy logic of taking 2 out of 3, the control system 3 detects flame failure at one of the burners 13 and 14. Instead, in Figure 6 In the example, only at the angular position J+1 Temperature sensor 23 is below temperature threshold T TH Based on the 2-out-of-3 redundancy logic, the abnormal measurement can be confirmed as an error because it is inconsistent with the measurement of the adjacent first temperature sensor 23.

[0039] Finally, it is obvious that changes and modifications may be made to the described and illustrated gas turbine engine and method without departing from the scope of the appended claims.

[0040] For example, in one embodiment, only one set of temperature sensors can be used for both flame monitoring and load control purposes. This solution can be particularly advantageous if the available sensors are fast and accurate enough to meet the design preferences for both control and flame monitoring functions.

[0041] It is also understood that the number of temperature sensors involved in flame monitoring, as well as their angular and radial positioning, may differ from those described, provided that a group of adjacent sensors (rather than a single sensor) is affected by cold spots as a result of their arrangement.

Claims

1. A gas turbine engine, comprising: Burner assembly (5), the burner assembly including a plurality of burners (13, 14); An exhaust frame (8) is provided with a plurality of radial struts (20); An exhaust diffuser (10) extends downstream of the exhaust frame (8) along a longitudinal axis (A); Multiple temperature sensors (23, 25) are located within the exhaust diffuser (10) downstream of the exhaust frame (8) and the support column (20) and arranged at corresponding angular and radial positions relative to the longitudinal axis (A). Control system (3), the control system being configured to respond based on the response of the temperature sensors (23, 25) and a temperature threshold (T) TH The system includes redundant logic to detect flame failure at one or more of the burners (13, 14); The temperature sensors (23, 25) include a first temperature sensor (23) with a faster first response and a second temperature sensor (25) with a more accurate second response, and the control system (3) is configured to determine flame failure at one or more of the burners (13, 14) based on the first response of the first temperature sensor (23).

2. The gas turbine engine according to claim 1, comprising a compressor (4) and a fuel supply system (15), wherein, The control system (3) is configured to control the air intake of the compressor (4) and the fuel supply to the burner assembly (5) based on the second response of the second temperature sensor (25).

3. The gas turbine engine according to claim 1 or 2, wherein, The exhaust diffuser (10) includes a housing (22) and a support rod (26) extending radially inward from the housing (22), wherein the first temperature sensor (23) and the second temperature sensor (25) are arranged on the respective support rod (26).

4. The gas turbine engine according to claim 3, wherein, The support rods (26) are located at a common axial position and are circumferentially distributed around the longitudinal axis (A), and at least some of the support rods (26) each hold a corresponding first temperature sensor in the first temperature sensor (23) and a corresponding second temperature sensor in the second temperature sensor (25).

5. The gas turbine engine according to claim 4, wherein, Each of the support rods (26) holding one of the first temperature sensors (23) also holds one of the second temperature sensors (25).

6. The gas turbine engine according to claim 2, wherein, The control system (3) is configured to detect flame failure in a group of adjacent first temperature sensors (23) based on redundancy logic of taking M from N, where N is the number of first temperature sensors (23) in each group and M is an integer less than or equal to N-1.

7. The gas turbine engine according to claim 6, wherein, The control system (3) is configured to define K groups (G1, ..., G2) of N adjacent first temperature sensors (23). K ), where K is the number of the first temperature sensors (23) in the exhaust diffuser (10), and each group (G1, ..., G) K ) includes N corresponding neighboring first temperature sensors (23) and each first temperature sensor belongs to N different groups (G1, ..., G K ).

8. The gas turbine engine according to claim 6, wherein, The control system (3) is configured to respond based on a first response of the first temperature sensor (23) and the temperature threshold (T). TH Flame failure is detected by comparing the temperature threshold (T) with the temperature threshold (T). TH The value is determined by the average value of the first response of the first temperature sensor (23) and the temperature offset (ΔT).

9. The gas turbine engine according to claim 8, wherein, The control system (3) is configured to respond to at least one group (G1, …, G) of the first temperature sensor (23). K The groups (G1, ..., G) mentioned in the text K The first response of the M-1 first temperature sensors (23) is lower than the temperature threshold (T) TH The flame failure was detected.

10. A method for controlling a gas turbine engine, the gas turbine engine (1) comprising: Burner assembly (5), the burner assembly including a plurality of burners (13, 14); An exhaust frame (8) is provided with a plurality of radial struts (20); An exhaust diffuser (10) extends downstream of the exhaust frame (8) along a longitudinal axis (A); The method includes: Multiple temperature sensors are provided in the exhaust diffuser (10) downstream of the exhaust frame (8) and the support column (20) relative to the longitudinal axis (A) at corresponding angular and radial positions; Based on the response of the temperature sensor and the temperature threshold (T) TH (and redundant logic to detect flame failure at one or more of the burners (13, 14); The temperature sensors (23, 25) include a first temperature sensor (23) with a faster first response and a second temperature sensor (25) with a more accurate second response, and the detection includes determining flame failure based on the first response of the first temperature sensor (23).

11. The method of claim 10, comprising: The load of the gas turbine engine (1) is controlled based on the second response of the second temperature sensor (25).

12. The method according to any one of claim 10 or 11, wherein, Detecting flame failure includes: in the group (G1, ..., G) of the adjacent first temperature sensor (23) K The application uses redundant logic of taking M from N, where N is the number of groups (G1, ..., G2). K The number of the first temperature sensors (23) in the N-1, and M is an integer less than or equal to N-1.

13. The method according to claim 12, wherein, The detection includes: defining K groups (G1, ..., G2) of N neighboring first temperature sensors (23). K ), where K is the number of the first temperature sensors (23) in the exhaust diffuser (10), and each group (G1, ..., G) K ) includes N corresponding neighboring first temperature sensors (23) and each first temperature sensor belongs to N different groups (G1, ..., G K ).

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