Sliding gas sensor settings for dual gases and / or variable gas mixtures

Abstract

A haz gas detection system includes a haz gas sensor and a controller. The haz gas sensor generates an output indicative of a measured concentration of a gas fuel in an airflow vented from a gas turbine enclosure. The controller is communicatively coupled to the haz gas sensor and receives the output from the haz gas sensor; compares the output of the haz gas sensor to a first threshold, wherein the first threshold is determined for operation of the haz gas sensor with methane gas; receives a valve control signal indicative of a propane valve being open; compares the output of the haz gas sensor to a second threshold, wherein the second threshold is determined for operation of the haz gas sensor with propane gas; and in response the determining that the output of the haz gas sensor exceeds the second threshold, generates an alarm, generates instructions to shut down the gas turbine system, or both.

Description

SLIDING GAS SENSOR SETTINGS FOR DUAL GASES AND / OR VARIABLE GAS MIXTURESBACKGROUND

[0001] The present disclosure relates generally to leak detection for gas fuel. In particular, the present disclosure relates to systems and methods for detecting leaks of multiple different types of gas fuel using a single sensor.

[0002] An enclosure may be used to house a variety of equipment, such as compressors, pumps, turbines, valves, furnaces, boilers, gasifiers, gas treatment systems such as acid gas removal (AGR) systems and carbon capture systems, and a variety of other industrial equipment. This equipment and various fluid lines disposed in the enclosure can potentially leak inside the enclosure. As an example, gas turbines engines are used in a variety of applications, including power plants. A gas turbine engine may be coupled to a generator in a stationary or mobile power plant. The gas turbine engine receives fuel for combustion in one or more combustors. The fuel, which may include liquid or gas fuel, may potentially leak within a gas turbine enclosure housing the gas turbine engine. A monitoring system may be fluidly coupled to the gas turbine enclosure to sample the air (i.e., extract the air through one or more sampling lines) to detect the presence of hazardous fluids. Such monitoring systems are typically calibrated to detect the predominant fuel being used. Unfortunately, when a second gas fuel is used, these monitoring systems may trigger alarms and / or trip the power generation units, even if the concentration of the second gas fuel does not actually exceed set thresholds, resulting in unnecessary and costly shutdowns. Accordingly, a need exists for an improved capability to monitor leaks of multiple gas fuels with a single sensor.BRIEF DESCRIPTION

[0003] Certain embodiments commensurate in scope with the originally claimed subject matter are summarized below. These embodiments are not intended to limit thescope of the claimed subject matter, but rather these embodiments are intended only to provide a brief summary of possible forms of the subject matter disclosed in the application. Indeed, the disclosed subject matter may encompass a variety of forms that may be similar to or different from the embodiments set forth below.

[0004] In a first embodiment, a hazardous (“haz”) gas detection system includes a haz gas sensor and a controller. The haz gas sensor is configured to generate an output indicative of a measured concentration of a gas fuel in a sampling airflow vented from a gas turbine system enclosure, the haz gas sensor having been calibrated with methane gas. The controller is communicatively coupled to the haz gas sensor and configured to receive the output from the haz gas sensor; compare the output of the haz gas sensor to a first threshold, wherein the first threshold is determined for operation of the haz gas sensor with methane gas; receive a valve control signal indicative of a propane valve being open; compare the output of the haz gas sensor to a second threshold upon receipt of the valve control signal indicative of the propane valve being open, wherein the second threshold is determined for operation of the haz gas sensor with propane gas, the second threshold being shifted from the first threshold; and in response the determining that the output of the haz gas sensor exceeds the second threshold, generate an alarm, generate instructions to shut down the gas turbine system, generate instructions to trip the gas turbine system, or any combination thereof.

[0005] In a second embodiment, a system includes a gas turbine enclosure; a gas turbine engine disposed within the gas turbine enclosure; an exhaust vent duct configured to route a ventilation flow out of the gas turbine enclosure; a sampling conduit in fluid communication with the exhaust vent duct; a haz gas sensor mounted to the sampling conduit, the haz gas sensor having been calibrated with a first gas fuel, wherein the haz gas sensor is configured to contact a sampling flow diverted from the exhaust vent duct and through the sampling conduit, and generate an output indicative of a measured concentration of a gas fuel in the sampling flow; and a controller communicatively coupled to the haz gas sensor. The controller is configured to receive the output from thehaz gas sensor; compare the output of the haz gas sensor to a first threshold, wherein the first threshold is determined for operation of the haz gas sensor with the first gas fuel or a first gas fuel mixture; receive an indication that a second gas fuel or a second gas fuel mixture is being provided to the gas turbine engine; compare the output of the haz gas sensor to a second threshold upon receipt of the indication that the second gas fuel or the second gas fuel mixture is being provided, wherein the second threshold is determined for operation of the haz gas sensor with the second gas fuel or the second gas fuel mixture, the second threshold being shifted from the first threshold; and in response the determining that the output of the haz gas sensor exceeds the second threshold, generate an alarm, generate instructions to shut down the gas turbine engine, generate instructions to trip the gas turbine engine, or any combination thereof.

[0006] A method includes: receiving, from a haz gas sensor calibrated with a first gas fuel, an output indicative of a measured concentration of a gas fuel in the sampling flow diverted from a ventilation flow out of a gas turbine enclosure of a gas turbine engine; comparing the output of the haz gas sensor to a first threshold, wherein the first threshold is determined for operation of the haz gas sensor with the first gas fuel or a first gas fuel mixture; receiving an indication that a second gas fuel or a second gas fuel mixture is being provided to the gas turbine engine; comparing the output of the haz gas sensor to a second threshold upon receipt of the indication that the second gas fuel or the second gas fuel mixture is being provided, wherein the second threshold is determined for operation of the haz gas sensor with the second gas fuel or the second gas fuel mixture, the second threshold being shifted from the first threshold; and in response the determining that the output of the haz gas sensor exceeds the second threshold, generating an alarm, generating instructions to shut down the gas turbine engine, generating instructions to trip the gas turbine engine, or any combination thereof.BRIEF DESCRIPTION OF THE DRAWINGS

[0007] These and other features, aspects, and advantages of the disclosed subject matter will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:

[0008] FIG. 1 is a schematic of an embodiment of a gas turbine system having a hazardous (“haz”) gas detection system;

[0009] FIG. 2A is a plot of sensor readings for propane in percent lower explosive limit (% LEL) and corresponding actual haz gas concentrations of propane in % LEL generated by the haz gas detection system of FIG. 1;

[0010] FIG. 2B is a plot of the sensor readings for propane in % LEL and corresponding actual haz gas concentrations of propane in % LEL from FIG 2A, but with adjusted thresholds;

[0011] FIG. 3 is a flow chart of a process of shifting settings for a gas sensor of the haz gas detection system of FIG. 1 between sensing methane and propane;

[0012] FIG. 4 is a flow chart of a process of adjusting settings for a gas sensor of the haz gas detection system of FIG. 1 for sensing multiple gases; and

[0013] FIG. 5 is a flow chart of a process of adjusting setting for a gas sensor of the haz gas detection system of FIG. 1 for sensing multiple gases.DETAILED DESCRIPTION

[0014] One or more specific embodiments of the disclosed subject matter will be described below. In an effort to provide a concise description of these embodiments, all features of an actual implementation may not be described in the specification. It shouldbe appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers’ specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure.

[0015] When introducing elements of various embodiments of the disclosed subject matter, the articles “a,” “an,” “the,” and “said” are intended to mean that there are one or more of the elements. The terms “comprising,” “including,” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements.

[0016] FIG. 1 is a schematic of an embodiment of a gas turbine system 10 having a haz gas detection system 12 coupled to a gas turbine enclosure 14 housing a gas turbine engine 16. In the illustrated embodiment, the haz gas detection system 12 includes a controller 18 communicatively coupled to one or more haz gas sensors 20 (e.g., open path infrared (OPIR) sensors or other types of optical / light sensors) via one or more communication lines 24. The haz gas detection system 12 is configured to obtain sensor feedback from the haz gas sensors 20 to facilitate an identification of hazardous gases (e.g., as a result of a fuel leak or other hazardous fluid leak) within the gas turbine enclosure 14, such as a leak of gas or liquid fuel. However, the haz gas detection system 12 also may be configured to detect other types of gases within the gas turbine enclosure 14.

[0017] As is described in more detail below, in present embodiments, one or more sensors 20 may be disposed within or otherwise be coupled to a sample flow, which may be diverted from a fluid flow within the gas turbine enclosure 14, such as an exhausted vent flow, via a sampling conduit 22. However, it should be understood that embodiments are envisaged that include sensors 20 disposed at various other locationsthroughout the gas turbine system 10, as shown in FIG. 1. Although the illustrated embodiment shows communication lines 24 extending between the controller 18 and the various haz gas sensors 20, certain embodiments of the haz gas detection system 12 may use wireless communications to obtain sensor data from the haz gas sensors 20.

[0018] The illustrated controller 18 includes a processor 26, a memory 28, and instructions 30 stored on the memory and executable by the processor 26 to perform a haz gas detection analysis and control. The controller 18 also includes communications circuitry 32, data processing circuitry 34, and one or more control actions 36 in response to the detected haz gas or other conditions within the gas turbine enclosure 14. The communications circuitry 32 may include wired and / or wireless communications circuitry to communicate with the haz gas sensors 20 and retrieve sensor data.

[0019] The data processing circuitry 34 is configured to process the sensor data from the haz gas sensors 20 and perform one or more analyses on the sensor data in order to determine if a leak has occurred or is occurring, if the leak is worsening over time, if the leak is in a particular location, if the leak is attributed to a particular type of fluid (e.g., gas fuel or liquid fuel), and / or if the leak is attributed to another event occurring in the gas turbine gas turbine system 10. The control actions 36 may include triggering an alarm, modifying operational parameters of the gas turbine engine 16, switching between different types of fuel such as liquid and gas fuel, or stopping operation of the gas turbine engine 16. The particular control actions 36 initiated by the controller 18 may depend on the type of feedback retrieved from the haz gas sensors 20. For example, if the haz gas sensors 20 indicate a leakage of liquid fuel, then the control action 36 may trigger a change from liquid fuel operation to gas fuel operation. If the sensor feedback indicates a gradually increasing amount of leakage within the gas turbine enclosure 14 and / or a leakage level above one or more thresholds, then the control actions 36 may trigger an alarm, a corrective action, and / or a shutdown of the gas turbine engine 16.

[0020] As discussed in further detail below, the haz gas sensors 20 may include a variety of sensor types, such as an optical / light sensor (e.g., an open path infrared (OPIR)sensor). Each depicted sensor 20 may include one or more transceivers (e.g., OPIR transceivers) or one or more pairs of transmitters and receivers (e.g., OPIR transmitters and receivers). Details of the haz gas detection system 12 will be discussed in further detail below after providing context for the gas turbine system 10.

[0021] The illustrated gas turbine engine 16 includes an air intake section 40, a compressor section 42, a combustor section 44, a turbine section 46 (i.e., an expansion turbine), an exhaust section 48, and one or more loads 50. The air intake section 40 includes an air treatment system 52 disposed in an intake duct 54 extending from an exterior of the gas turbine enclosure 14 and into the gas turbine enclosure 14 to connect with the compressor section 42. The air treatment system 52 includes one or more air filters 56, one or more silencers 58, and an anti-ice system 60. The air intake section 40 routes an air flow 62 through the intake duct 54 to the compressor section 42, while filtering the air flow 62 with the one or more air filters 56, reducing noise in the air intake section 40 with the one or more silencers 58, and inhibiting ice formation in the air flow 62 with the anti-ice system 60. The air flow 62 then passes through the compressor section 42, which includes a single stage or multi-stage compressor 64. In the illustrated embodiment, the compressor 64 has a plurality of stages of compressor blades 66 coupled to a compressor shaft 68 within an outer compressor casing 70. Although the illustrated embodiment shows four compressor stages, the compressor 64 may include between 1 and 18 or more compressor stages of rotating compressor blades 66 and stationary nozzles (not shown) to compress the air flow 62 before entering the combustor section 44.

[0022] The compressed air is then directed into a plurality of combustors 72 of the combustor section 44 as illustrated by arrows 74. Each combustor 72 in the combustor section 44 may include one or more fuel nozzles 76. The fuel nozzles 76 are configured to mix the compressed air 74 with one or more fuels, such as a liquid fuel delivered along a liquid fuel line 78 (or liquid fuel circuit or flow path) from a liquid fuel system 80 of a dual fuel system 82 and / or a gas fuel delivered along a gas fuel line 84 (or gas fuel circuitor flow path) from a gas fuel system 86, which may include multiple gas fuel systems 86A, 86B for using multiple gas fuels, of the dual fuel system 82. The fuel nozzles 76 may be configured to use only one of the liquid fuel or the gas fuel for a liquid fuel operation or a gas fuel operation, respectively. However, the fuel nozzles 76 also may be configured to simultaneously use both the liquid fuel and the gas fuel for combustion in the combustor 72, for example, during a transition between liquid and gas fuel operation.

[0023] The liquid fuel and the gas fuel may be selected from a variety of fuel types and compositions. For example, the gas fuel may include natural gas, synthetic gas (or syngas), hydrogen, methane, propane, or another suitable gas turbine fuel. Regardless of the specific type of fuel being used in the combustors 72, the fuel nozzles 76 mix the fuel with the compressed air 74, and the fuel-air mixture ignites in a combustion chamber 88 to generate hot combustion gases 90, which are then directed into the turbine section 46.

[0024] The turbine section 46 may include a single stage or multi-stage turbine 92, which includes one or more stages of turbine blades 94 coupled to a turbine shaft 96 within a turbine casing 98. For example, in certain embodiments, the turbine 92 may include between 1 and 4 turbine stages of turbine blades 94 and stationary turbine nozzles (not shown). As the hot combustion gases 90 flow through the turbine section 46, the gases 90 drive rotation of the turbine blades 94 and the turbine shaft 96. In turn, rotation of the turbine shaft 96 drives rotation of the compressor 64 via an intermediate shaft 100 coupled to the compressor shaft 68, and drives rotation of the load 50 via a shaft 102. Although separate shafts 68, 96, 100, and 102 may be used with the gas turbine engine 16, certain embodiments of the gas turbine engine 16 may include one or more common shafts between the compressor section 42, the turbine section 46, and the load 50. The load 50 may include a generator, industrial machinery, a vehicle propulsion system, or any other suitable equipment.

[0025] The gas turbine enclosure 14 generally surrounds the gas turbine engine 16 and provides a protective barrier around the gas turbine engine 16. For example, the gas turbine enclosure 14 may substantially contain the heat generated by combustion in thecombustor section 44, and the gas turbine enclosure 14 may provide a containment for safety reasons. The gas turbine system 10 also includes a ventilation system 104 coupled to the gas turbine enclosure 14. As illustrated, the ventilation system 104 includes an air vent intake 106 and an air vent exhaust 108 coupled to the gas turbine enclosure 14. The air vent intake 106 includes one or more air filters 110 and one or more fans 112 disposed in an intake duct 114, thereby directing and filtering an air flow into the gas turbine enclosure 14 as illustrated by arrow 116. Similarly, the air vent exhaust 108 includes one or more fans 118 disposed in an exhaust vent duct 120 to route the ventilation flow out of the gas turbine enclosure 14 as illustrated by arrow 122. Although the air vent intake 106 and the air vent exhaust 108 may each include fans 112 and 118, in certain embodiments, the fans may be disposed in only one of the air vent intake 106 or the air vent exhaust 108. In operation, the ventilation system 104 circulates the air flow through the gas turbine enclosure 14 as illustrated by arrows 116 and 122, thereby withdrawing heat and / or any leaked fluids (e.g., leaked fuel) out of the gas turbine enclosure 14. A portion of the flow is directed from the exhaust vent duct 120 to the sampling conduit 22 for analysis, such that the haz gas detection system 12 can analyze a smaller volume of flow in a rapid manner. If any leakage occurs inside the gas turbine enclosure 14, the haz gas detection system 12 is configured to identify the leaks (e.g., by analysis of the sampling flow) and enable certain control actions 36.

[0026] The haz gas detection system 12 is communicatively coupled to the plurality of haz gas sensors 20 that are coupled to the gas turbine enclosure 14 of the gas turbine system 10 and to one or more sensors 20 that are coupled to enclosures 124 housing turbomachines 126. In certain embodiments, the turbomachines 126 may include additional gas turbine engines similar to the gas turbine engine 16 disposed inside the gas turbine enclosure 14. However, the turbomachines 126 also may include other equipment, such as combustion systems, gas compressors, reciprocating piston-cylinder combustion engines, boilers, gas treatment systems (e.g., sulfur removal units) for treating a syngas generated by a gasifier (e.g., using coal or another fuel feedstock), or other equipment having a potential for leakage of fuels or hazardous gases.

[0027] The haz gas detection system 12 is configured to simultaneously monitor sensor feedback from the haz gas sensors 20 disposed in each of these systems and provide appropriate control actions 36. If the gas turbine engine 16 and the turbomachines 126 are functionally related and / or dependent on one another as part of a larger system, such as a power plant, then the haz gas detection system 12 may coordinate the control actions 36 between the gas turbine engine 16 and the turbomachines 126. However, in certain embodiments, the gas turbine engine 16 and the turbomachines 126 may be independent from one another, such that the haz gas detection system 12 can provide independent control actions 36 to the gas turbine engine 16 and the various turbomachines 126.

[0028] In each of these systems, the haz gas sensors 20 may be distributed at different locations about the gas turbine enclosure 14, which may provide redundancy in the sensor measurement and may also provide additional information regarding the location of any potential leak occurring in the particular enclosure (e.g., 14 and 124). For example, as illustrated with the gas turbine enclosure 14, the haz gas sensors 20 are distributed at various locations along the gas fuel line 84 and the liquid fuel line 78, the combustors 72, and the air vent exhaust 108. By further example, the haz gas sensors 20 may be coupled to a removable roof panel 15 (or other removable access panel) of the gas turbine enclosure 14. Accordingly, the haz gas sensors 20 may obtain sensor feedback indicative of a greater or lesser presence of leakage in certain locations of the gas turbine enclosure 14, such that the controller 18 can estimate a specific location of the leak, a potential component having a leak, a possible corrective measure, and a possible control actions 36 in the event that the leak cannot be corrected. As discussed in further detail below, the haz gas sensors 20 also may be configured to identify a specific type of fuel leak, such as a type of liquid fuel or gas fuel.

[0029] In certain embodiments, the haz gas sensors 20 are optical sensors. For example, the haz gas sensors 20 may transmit and receive an optical beam (e.g., a beam of light or radiation) through a fluid flow such that changes in characteristics of theoptical beam can be analyzed to determine whether a leak is occurring inside the gas turbine enclosure 14. For example, the haz gas sensors 20 and / or the data processing circuitry 34 of the controller 18 may be configured to analyze changes in the optical beam passing through the fluid flow to determine a composition of any fluid leakage inside the gas turbine enclosure 14.

[0030] The sensors 20 may include infrared (IR) light sensors, laser sensors, electromagnetic radiation sensors, or any other suitable optical-based sensor. In particular, the disclosed haz gas sensor 20 may include an open path infrared (OPIR) sensor. The OPIR sensors 20 may include a pair of a transmitter and a receiver or a pair of a transceiver and a reflector (e.g., a retroreflector). The reflector may include a reflective panel having a substrate layer and a reflective layer (e.g., a mirror layer). The OPIR sensor 20 is configured to direct a beam of infrared light through a fluid flow within the gas turbine system 10 (e.g., within a sampling flow in the sampling conduit 22 that is fluidly coupled to the exhaust vent duct 120). The presence of a potential fuel leak in the gas turbine enclosure 14 can be detected due to an absorption of an infrared wavelength in the beam of infrared light. For example, a particular infrared wavelength may correspond to a particular fuel type, such as a particular liquid fuel, a particular gas fuel, or other hazardous fluid within the gas turbine system 10. However, it should be understood that embodiments are also envisaged that utilize sensors 20 that are not optical sensors. For example, the sensors 20 may include any type of haz gas sensors including and not limited to infra-red, catalaytic bead sensors, etc.

[0031] The sensors 20 are configured to detect specific types of leakages within the gas turbine enclosure 14, such that the controller 18 can identify possible corrective actions 36 for the gas turbine engine 16. For example, sensors 20 may be calibrated using experimentally derived calibration curves to associate sensor readings with concentrations of particular gas of interest. However, if multiple gas fuels (e g., methane and propane) are being used by a gas turbine system 10, a sensor 20 that is calibrated for detection of one gas (e.g., methane), may output incorrect readings in response todetection of a second gas (e.g., propane). Thus, the haz gas detection system 12 may incorrectly determine that alarm and / or trip thresholds have been exceeded, when the actual concentration of the second gas is below the alarm and / or trip thresholds for the second gas. Accordingly, the haz gas detection system 12 may be configured to determine when one or more additional gases may be present and temporarily adjust (e.g., raise) the alarm and / or trip thresholds for a period of time, or during the time at which the one or more additional gases may be present.

[0032] For example, a sensor 20 may be calibrated for methane detection, with an alarm threshold set at 7% of the lower explosive limit (LEL) concentration and a trip threshold set at 11% LEL. However, if the sensor is exposed to propane instead of methane, the sensor may output a reading of 7% LEL when the actual concentration of propane is 4% LEL and may output a reading of 11% LEL when the actual concentration of propane is 6% LEL, as shown in FIG. 2A. Accordingly, this may cause the haz gas detection system 12 to determine that alarm and / or trip thresholds have been exceeded when the actual concentration of propane is below the respective thresholds, which may result in false positive alarms, shut downs, and so forth. Accordingly, to reduce or eliminate such situations, the haz gas detection system 12 may be configured to identify when propane may be present and to adjust alarm and trip thresholds to account for propane being present.

[0033] In one embodiment, the haz gas detection system 12 (e.g., the communications circuit 32 of the haz gas detection system 12) may be communicatively coupled to the dual fuel system 82 (e.g., the gas fuel system 86) wirelessly, via a communication line 128, a communication bus, or some other way. The dual fuel system 82 may provide access to a valve control signal to the haz gas detection system 12, or the haz gas detection system 12 may otherwise have access to the valve control signal. The valve control signal may indicate which, if any, of the valves (e.g., valve 1 and valve 2) are open, enabling flow of gas fuel from the one or more gas fuel systems 86A, 86B to the chamber 88 via the gas fuel lines 84. Based upon which valves are open, the controller18 of the haz gas detection system 12 can determine which fuels are being provided to the combustion chamber 88 via the fuel nozzles 76. Accordingly, the haz gas detection system 12 can determine when specific gases are being provided to the combustion chamber 88 and can temporarily adjust alarm and trip thresholds accordingly.

[0034] However, it should be understood that other embodiments are envisaged that utilize other techniques for determining which fuels are being provided to the combustion chamber 88 by the dual fuel system 82. For example, as shown in FIG. 1, in some embodiments, sensors 20 may be disposed within or coupled to liquid fuel lines 78 and / or gas fuel lines 84. For example, in some embodiments (e.g., embodiments in which blended gases are being used), the sensor 20 may be one or more flowmeters configured to determine which liquids and / or gases are flowing though the liquid fuel lines 78 and / or gas fuel lines 84. In such embodiments, different liquid and / or gas fuels may have dedicated liquid fuel lines 78 and / or gas fuel lines 84. Accordingly, which liquids and / or gases are being provided to the combustion chamber 88 may be determined by using readings from the flowmeters to determine which liquid fuel lines 78 and / or gas fuel lines 84 have liquids and / or gases flowing through them and which liquid fuel lines 78 and / or gas fuel lines 84 are static or mostly static and thus not flowing to the combustion chamber 88. In other embodiments (e.g., embodiments in which variable gas mixtures are being used), the sensor 20 may be an analyzer configured to analyze the liquid and / or gas flowing though the liquid fuel lines 78 and / or gas fuel lines 84 and to determine which fuels are being provided to the combustion chamber 88.

[0035] FIGS. 2A and 2B illustrate shifting thresholds to account for sensor readings not matching actual haz gas concentrations. FIG. 2A is a plot 200 of sensor readings for propane in % LEL (horizontal axis 202) and corresponding actual haz gas concentrations of propane in % LEL (vertical axis 204), when concentrations of propane are measured using a sensor calibrated with methane. As shown, a first alarm threshold 206 for methane is set at 7% LEL, but when the combustors 72 are operating on propane and the sensor reads 7% LEL, the actual haz gas concentration of propane is only about 4% LEL.Similarly, a first trip threshold 208 for methane is set at 11% LEL, but when the combustors 72 are operating on propane and the sensor reads 11% LEL, the actual haz gas concentration of propane is only about 6% LEL. Accordingly, with the first and second thresholds 206, 208 set as shown in FIG. 2A, when the methane-calibrated sensor 20 is exposed to propane, the sensor 20 will read a higher % LEL than the actual haz gas concentration, causing the sensor 20 to assess that the alarm and / or trip thresholds 206, 208 have been crossed.

[0036] To address this problem, the haz gas detection system 12 may determine that the gas fuel being fed to the combustion chamber 88 is different from the gas for which the one or more sensors 20 were calibrated and may shift the alarm and / or trip thresholds 206, 208 to account for the different gas being used. As previously described, in some embodiments, valve control signals may be used to determine which gas fuels are being provided to the combustion chamber 88. However, in other embodiments, flowmeters and / or analyzers may also be used to determine the composition of gas fuels being provided to the combustion chamber 88.

[0037] As shown in FIG. 2B, the first threshold 206 (e.g., the alarm threshold) is shifted up the plot 200 to a shifted alarm threshold 216 at 14% LEL, which is the corresponding sensor reading when the actual haz gas concentration (e g., of propane) is 7% LEL. Similarly, the second threshold 208 (e.g., the trip threshold) is shifted up the plot 200 to a shifted trip threshold 218 at 27% LEL, which is the corresponding sensor reading when the actual haz gas concentration (e.g., of propane) is 11% LEL. The haz gas detection system 12 may operate under with the shifted thresholds 216, 218 as long as the gas fuel flowing to the combustion chamber 88 matches the fuel for which the shifted thresholds are applicable. In some embodiments, the haz gas detection system 12 may continue to operate with the shifted thresholds 216, 218 for a period of time (e.g., 5 seconds, 10 seconds, 30 seconds, 1 minute, 2 minutes, 3 minutes, 5 minutes, 10 minutes, etc.) after the haz gas detection system has determined that a different gas fuel (e.g., methane) is flowing to the combustion chamber 88 chamber to allow the different fuel towork its way through the gas turbine system 10 after flow to the combustion chamber 88 has ceased. Similarly, the haz gas detection system 12 may be configured to monitor the fuel flowing to the combustion chamber 88, either constantly or on a periodic basis, and to adjust various thresholds as needed. Accordingly, though FIGS. 2A and 2B illustrate shifting thresholds to account for methane and propane being used, it should be understood that embodiments are envisaged utilizing other gases.

[0038] Further, embodiments are envisaged in which a different number of thresholds are shifted. For example, the haz gas detection system 12 may be configured to shift one, three, four, five, etc. thresholds based on the type of gas fuel flowing to the combustion chamber 88. Similarly, though FIGS. 2A and 2B illustrate shifting between two sets of thresholds (one set for methane and one set for propane), embodiments are envisaged in which the haz gas detection system 12 shifts between a different number of sets of thresholds. For example, the haz gas detection system may be configured to shift between 3, 4, 5, 6, 7, 8, 9, 10, and so forth sets of thresholds, which may correspond to different gas fuels or mixtures of gas fuels being provided to the combustion chamber 88. Further, it should be understood that the plot 200, the thresholds 206, 208, the shifted thresholds 216, 218, and the relationships between the (methane-calibrated) sensor reading and the actual haz gas concentration (e.g., of propane) are merely examples and that embodiments are envisaged that utilize other values and / or relationships.

[0039] FIG. 3 is a flow chart of a process 300 of shifting gas sensor settings between operation using methane or propane. At block 302, the gas turbine system 10 is operated as described with regard to FIG. 1. For example, fuel is provided to a combustion chamber 88 by nozzles 76 and combusted to produce hot combustion gases. The hot combustion gases cause the turbine blades 94 in a turbine section 46 to rotate a turbine shaft 96. The turbine shaft 96 is coupled to a compressor shaft 68 (e.g., via an intermediate shaft 100) such that rotation of the turbine shaft 96 causes the compressor shaft 68 to rotate. Compressor blades 66 coupled to the compressor shaft 68 rotate around the compressor shaft 68, compressing air that is provided to the combustionchamber 88. In the instant embodiment, the gas fuel system 86A, 86B may include a methane reservoir and a propane reservoir as part of the dual fuel system 82. One or more valves (valve 1, valve 2 of FIG. 1) may be used to allow methane and / or propane to flow from their respective reservoirs, through the gas fuel lines 84, and into the combustion chamber 88. Based on various conditions of the gas turbine system 10, an operator may wish to use methane, propane, or some combination thereof.

[0040] A haz gas sensor 20 may be used to test exhausted vent air diverted through a sampling conduit 22 to identify fuel leaks in the gas turbine enclosure 14. The haz gas sensor 20 may be calibrated based on a calibration curve for methane and, accordingly, may react differently when exposed to propane rather than to methane. As discussed previously with regard to FIGS. 1 and 2, alarm and / or trip thresholds 206, 208 for the haz gas sensor 20 may be set based on the calibration curve for methane. However, when the haz gas sensor 20 is exposed to propane, the sensor 20 may confuse lower concentrations of propane for higher concentrations of methane such that the haz gas sensor 20 may determine that the alarm and / or trip thresholds 206, 208 (originally established for methane) have been exceeded when the actual concentration of propane may be below the alarm and / or trip thresholds 216, 218 that are applicable to propane. This may result in false positive alarms and / or trips, resulting in unnecessary shutdowns, downtime, and / or decreases in reliability and / or performance. As described previously, this false positive issue may be addressed by shifting thresholds when the system 12 determines that propane is being used.

[0041] At decision 304, the process 300 determines whether one or more propane valves are open. For example, the dual fuel system (e.g., the haz gas sensor, a controller, etc.) may have access to a valve control signal for one or more propane valves. Based on the valve control signal, the process 300 may determine whether propane is flowing into the combustion chamber. If the propane valve is closed, the process 300 may assume that only methane is being provided to the combustion chamber (e.g., no propane is flowing to the combustion chamber) and may proceed to block 306. At block 306, the processapplies the methane thresholds (e.g., 206, 208) derived from the methane calibration. For example, a first threshold 206 may be set at 7% LEL, and a second threshold 208 may be set at 11% LEL. However, it should be understood that these thresholds are merely examples and that other embodiments are also envisaged.

[0042] For example, in some embodiments, the process 300 may apply 1 threshold, 2 thresholds, 3 thresholds, 4 thresholds, 5 thresholds, 6 thresholds, 7 thresholds, 8 thresholds, 9, thresholds, 10 thresholds, and so forth. Each threshold may result in the same, different, or various combinations of actions being taken. Further, embodiments are envisaged in which the thresholds 206, 208 are set to different values. For example, thresholds may be set to 1% LEL, 2% LEL, 3% LEL, 4% LEL, 5% LEL, 6% LEL, 7% LEL, 8% LEL, 9% LEL, 10% LEL, 11% LEL, 12% LEL, 13% LEL, 14% LEL, 15% LEL, 16% LEL, 17% LEL, 18% LEL, 19% LEL, 20% LEL, 21% LEL, 22% LEL, 23% LEL, 24% LEL, 25% LEL, 26% LEL, 27% LEL, 28% LEL, 29% LEL, 30% LEL, or any other value. When thresholds 206, 208 are exceeded, various corresponding actions may be taken. For example, when an alarm threshold 206 is exceeded, the process 300 may generate one or more alarms. When a trip threshold 208 is exceeded, the process 300 may generate instructions to shut down the gas turbine system 10, transition to a safe mode, and so forth. It should be understood, however, that other thresholds may be set such that, when crossed, the process 300 performs other functions.

[0043] If the propane valve is open, the process 300 may assume that propane is being provided to the combustion chamber and proceed to block 308. At block 308, the process 300 applies the shifted thresholds 216, 218 for propane haz gas detection. For example, a shifted alarm threshold 216 may be set at 14% LEL, and a shifted trip threshold may be set at 27% LEL. However, it should be understood that these shifted thresholds 216, 218 are merely examples and that other embodiments are also envisaged. For example, in some embodiments, the process 300 may shift and apply 1 threshold, 2 thresholds, 3 thresholds, 4 thresholds, 5 thresholds, 6 thresholds, 7 thresholds, 8 thresholds, 9, thresholds, 10 thresholds, and so forth. Each threshold may result in the same, different,or various combinations of actions being taken. Further, embodiments are envisaged in which the shifted thresholds 216, 218 are set to trigger actions at different values. For example, shifted thresholds may be set to 1% LEL, 2% LEL, 3% LEL, 4% LEL, 5% LEL, 6% LEL, 7% LEL, 8% LEL, 9% LEL, 10% LEL, 11% LEL, 12% LEL, 13% LEL, 14% LEL, 15% LEL, 16% LEL, 17% LEL, 18% LEL, 19% LEL, 20% LEL, 21% LEL, 22% LEL, 23% LEL, 24% LEL, 25% LEL, 26% LEL, 27% LEL, 28% LEL, 29% LEL, 30% LEL, or any other value. When shifted thresholds are exceeded, various corresponding actions may be taken. For example, when the shifted alarm threshold 216 is exceeded, the process 300 may generate one or more alarms. When the shifted trip threshold 218 is exceeded, the process 300 may generate instructions to shut down the gas turbine system 10, transition to a safe mode, and so forth. It should be understood, however, that other shifted thresholds may be set such that, when crossed, the process 300 performs other functions.

[0044] After a period of time, the process 300 returns to decision 304 and determines if the one or more propane valves are open. If the propane valve is closed, the process 300 may assume that only methane is being provided to the combustion chamber (e.g., no propane is flowing to the combustion chamber) and proceed to block 306. If the propane valve is open, the process 300 may assume that propane is being provided to the combustion chamber and proceed to block 308. If the process 300 determines that the propane valve has gone from open to closed, the process 300 may wait for a period of time (e.g., 1 second, 3 seconds, 5 seconds, 10 seconds, 20 seconds, 30 seconds, 10 minutes, 2 minutes, etc.) for the propane to work its way through the gas turbine system 10 before reverting back to applying the methane thresholds (e.g., 206, 208).

[0045] FIG. 4 is a flow chart of a process 400 of adjusting gas sensor settings for sensing multiple gases and / or variable mixtures of gases. At block 402, the process 400 operates the gas turbine system 10. For example, fuel flows to a combustion chamber 88 via nozzles 76 and is combusted to produce hot combustion gases. The hot combustion gases rotate the turbine blades 94 and a turbine shaft 96 in a turbine section 46. Theturbine shaft 96 is coupled to a compressor shaft 68 such that rotation of the turbine shaft 96 causes the compressor shaft 68 and compressor blades 66 to rotate, compressing air that is provided to the combustion chamber 88.

[0046] The gas fuel system 82 of the gas turbine system 10 may include two of more reservoirs for various fuels. For example, the gas fuels may include methane, propane, butane, ethane, one or more high density gases, one or more industrial gases, and / or one or more flammable gases. Fuels may flow through gas fuel lines (e.g., 84) from their respective reservoirs to the combustion chamber 88. Based on various conditions of the gas turbine system 10, an operator may wish to use a particular gas fuel or a particular mixture of gas fuels.

[0047] A haz gas sensor 20 may be used to test exhausted vent air diverted through a sampling conduit 22 to identify fuel leaks in the gas turbine enclosure 14. The haz gas sensor 20 may be calibrated based on a calibration curve for a first gas fuel (e.g., a single gas fuel or a mixture of gas fuels) and, accordingly, may react differently when exposed to a second gas fuel or a different mixture of gas fuels. As discussed previously with regard to FIGS. 1 and 2, alarm and / or trip thresholds 206, 208 for the haz gas sensor 20 may be set based on the calibration curve for a first gas (e.g., methane). However, when the haz gas sensor 20 is exposed to a second gas (e.g., propane), the sensor 20 may confuse lower concentrations of the second gas for higher concentrations of the first gas such that the haz gas sensor 20 may determine that the alarm and / or trip thresholds 206, 208 (originally established for methane) have been exceeded when the actual concentration of propane may be below the alarm and / or trip thresholds 216, 218 that are applicable to propane. This may result in false positive alarms and / or trips, resulting in unnecessary shut downs, downtime, and / or decreases in reliability and / or performance. As described previously, this false positive issue may be addressed by shifting thresholds when the system 12 determines that a different gas fuel or combination of gas fuels is being used than the fuel used to calibrate the haz gas sensor 20.

[0048] At block 404, the process 400 measures one or more characteristics of the gas fuel(s) being provided to the combustion chamber 88. A variety of techniques may be used to identify which gases are flowing through the gas fuel lines 84 (block 406). For example, one or more flow meters may be disposed in or around the gas fuel lines 84 and may be used to identify one or more characteristics of gases flowing through the gas fuel lines 84, which may then be used to identify the gas fuel or gas fuels flowing through the gas fuel lines 84. In other embodiments, an analyzer may be disposed in or around the gas fuel lines 84 and used to determine the composition of gases flowing through the gas fuel lines 84. Further, in some embodiments, the control signals of the valves (e.g., valve 1, valve 2 of FIG. 1) that allow gas fuels to flow from their respective reservoirs through the gas fuel lines 84 may be used to determine which valves are open and thus infer which gases are flowing through the gas fuel lines 84.

[0049] At decision 408, the process 400 determines whether the sensed / identified fuel matches the calibration fuel. If the process 400 determines that the sensed fuel matches the fuel used to calibrate the sensor (e g., the first fuel, such as methane), the process 400 may assume that only the first fuel is being provided to the combustion chamber 88 (e g., no second fuel, such as propane, is flowing to the combustion chamber) and proceed to block 410.

[0050] At block 410, the process 400 applies the thresholds for the calibration fuel derived from the calibration of the sensor 20 with the first fuel (e.g., methane). For example, a first (alarm) threshold 206 may be set at 7% LEL, and a second (trip) threshold 208 may be set at 11% LEL. However, it should be understood that these thresholds 206, 208 are merely examples and that other embodiments are also envisaged. For example, in some embodiments, the process 400 may apply 1 threshold, 2 thresholds, 3 thresholds, 4 thresholds, 5 thresholds, 6 thresholds, 7 thresholds, 8 thresholds, 9, thresholds, 10 thresholds, and so forth. Each threshold may result in the same, different, or various combinations of actions being taken. Further, embodiments are envisaged in which the thresholds 206, 208 are set to trigger actions at different values. For example,thresholds may be set to 1% LEL, 2% LEL, 3% LEL, 4% LEL, 5% LEL, 6% LEL, 7% LEL, 8% LEL, 9% LEL, 10% LEL, 11% LEL, 12% LEL, 13% LEL, 14% LEL, 15% LEL, 16% LEL, 17% LEL, 18% LEL, 19% LEL, 20% LEL, 21% LEL, 22% LEL, 23% LEL, 24% LEL, 25% LEL, 26% LEL, 27% LEL, 28% LEL, 29% LEL, 30% LEL, or any other value. When thresholds 206, 208 are exceeded, various corresponding actions may be taken. For example, when an alarm threshold 206 is exceeded, the process 400 may generate one or more alarms. When a trip threshold 208 is exceeded, the process 400 may generate instructions to shut down the gas turbine system 10, transition to a safe mode, and so forth. It should be understood, however that other thresholds may be set such that, when crossed, the process 400 performs other functions.

[0051] If the sensed fuel does not match the calibration fuel (e.g., the sensed fuel is a second gas fuel, such as propane, or a mixture of the second fuel and the first fuel, or the second fuel and some other fuel), the process 400 may assume that the second fuel or a mixture of fuels that is different from the calibration fuel is being provided to the combustion chamber 88 and proceed to block 412. At block 412, the process 400 applies shifted thresholds for the second fuel (e.g., propane) or a mixture of fuels that is different from the calibration fuel. For example, a shifted alarm threshold 216 may be set at 14% LEL, and a shifted trip threshold may be set at 27% LEL. However, it should be understood that these thresholds are merely examples and that other embodiments are also envisaged. For example, in some embodiments, the process 400 may shift and apply 1 threshold, 2 thresholds, 3 thresholds, 4 thresholds, 5 thresholds, 6 thresholds, 7 thresholds, 8 thresholds, 9, thresholds, 10 thresholds, and so forth. Each shifted threshold may result in the same, different, or various combinations of actions being taken. Further, embodiments are envisaged in which the shifted thresholds are set to trigger actions at different values. For example, thresholds may be set to 1% LEL, 2% LEL, 3% LEL, 4% LEL, 5% LEL, 6% LEL, 7% LEL, 8% LEL, 9% LEL, 10% LEL, 11% LEL, 12% LEL, 13% LEL, 14% LEL, 15% LEL, 16% LEL, 17% LEL, 18% LEL, 19% LEL, 20% LEL, 21% LEL, 22% LEL, 23% LEL, 24% LEL, 25% LEL, 26% LEL, 27% LEL, 28% LEL, 29% LEL, 30% LEL, or any other value. When the shifted thresholds 216,218 are exceeded, various corresponding actions may be taken. For example, when a shifted alarm threshold 216 is exceeded, the process 400 may generate one or more alarms. When a shifted trip threshold 218 is exceeded, the process 400 may generate instructions to shut down the gas turbine system 10, transition to a safe mode, and so forth. It should be understood, however that other thresholds may be set such that, when crossed, the process 400 performs other functions.

[0052] After a period of time, the process 400 returns to block 404 and measures one or more characteristics of the gas fuel flowing through the gas fuel lines 84. If the one or more characteristics of the gas fuel flowing through the gas fuel lines 84 match the calibration fuel, the process 400 may assume that only the calibration fuel (e.g., the first fuel or methane) is being provided to the combustion chamber 88 and apply the thresholds 206, 208 for the calibration fuel. If the one or more characteristics of the gas fuel flowing through the gas fuel lines does not match the calibration fuel, the process 400 may assume that a second fuel, either by itself or in a mixture of other gases, which may or may not include the calibration gas fuel, is being provided to the combustion chamber 88 and proceed to apply shifted thresholds 216, 218 for the identified gas fuel. If the process 400 determines that the gas flowing through the gas fuel lines 84 has changed, the process 400 may wait for a period of time (e g., 1 second, 3 seconds, 5 seconds, 10 seconds, 20 seconds, 30 seconds, 10 minutes, 2 minutes, etc.) for the second fuel or other gas different from the calibration fuel to work its way through the gas turbine system 10 before reverting back to applying the thresholds 206, 208 for the calibration fuel.

[0053] FIG. 5 is a flow chart of a process 500 of adjusting gas sensor settings for sensing multiple gases and / or variable mixtures of gases. At block 502, the process 500 operates the gas turbine system 10, as described above. At block 504, the process 500 (e g., the controller 18) receives a signal from the haz gas sensor 20 disposed in fluid communication with the sampling conduit 22. The sampling conduit 22 receives a portion of the airflow from the exhaust vent duct 120 that is coupled to the gas turbine enclosure14. The output from the haz gas sensor 20 is indicative of a measured gas fuel concentration from the gas turbine enclosure 14. At block 506, the controller 18 compares the output to the first threshold and, more specifically, to a first alarm threshold and a first trip threshold, which are previously set based on the fuel (i.e., the first fuel) used to calibrate the haz gas sensor 20. In embodiments herein, the first fuel may be methane.

[0054] At block 508, the controller 18 determines whether the gas turbine engine 10 is operating on the first fuel (e.g., methane) or on a second, different fuel or fuel blend (e.g., propane). Various methods for determining the fuel composition may be used, as previously discussed herein (e.g., valve position, fuel analyzer, flowmeter, sensor, etc.). At block 510, after the gas turbine engine 10 is determined to be operating on the first fuel, the controller 18 generates an alarm, generates shutdown instructions, and / or generates a trip of the gas turbine engine 10 if the output exceeds the first threshold values, which were previously set for the first fuel. If the first alarm threshold is exceeded, an alarm is generated. If the first trip threshold is exceeded, the gas turbine engine 10 is tripped. (An alarm may also be associated with the tripping of the gas turbine engine 10.)

[0055] Alternately to block 510, after the gas turbine engine 10 is determined to be operating on a second fuel, the controller 18 compares the output to the second threshold and, more specifically, to a second alarm threshold and a second trip threshold, which are previously set based on the fuel (i.e., the second fuel). The second alarm threshold and the second trip threshold are shifted in comparison to the first alarm threshold and the first trip threshold, as shown in FIG. 2B, such that the associated %EEL values for the respective second thresholds are greater than the %LEL values for the respective first thresholds. At block 520, the controller 18 generates an alarm, generates shutdown instructions, and / or generates a trip of the gas turbine engine 10 if the output exceeds the second threshold values, which were previously set for the second fuel. If the second alarm threshold is exceeded, an alarm is generated. If the second trip threshold isexceeded, the gas turbine engine 10 is tripped. (An alarm may also be associated with the tripping of the gas turbine engine 10.)

[0056] Technical effects of the disclosed subject matter include the ability to detect leaks of multiple different gases with a single sensor. In particular, the disclosed measurement techniques include using a sensor calibrated for use with a first gas, determining that a second gas fuel is being provided to the gas turbine system, and adjusting alarm and trip thresholds for the second gas fuel. Use of the present techniques reduce downtime and shutdowns of the gas turbine system, while improving reliability / performance, while keeping costs down by avoiding a need for additional sensors.

[0057] This written description uses examples to describe various embodiments of the disclosed subject matter, including the best mode, and also to enable any person skilled in the art to practice the disclosed subject matter, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the subject matter is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.

Claims

CLAIMS:

1. A haz gas detection system, comprising: a haz gas sensor configured to generate an output indicative of a measured concentration of a gas fuel in a sampling airflow vented from a gas turbine enclosure, the haz gas sensor having been calibrated with methane gas; and a controller communicatively coupled to the haz gas sensor, wherein the controller is configured to: receive the output from the haz gas sensor; compare the output of the haz gas sensor to a first threshold, wherein the first threshold is determined for operation of the haz gas sensor with methane gas; receive a valve control signal indicative of a propane valve being open; compare the output of the haz gas sensor to a second threshold upon receipt of the valve control signal indicative of the propane valve being open, wherein the second threshold is determined for operation of the haz gas sensor with propane gas, the second threshold being shifted from the first threshold; and in response the determining that the output of the haz gas sensor exceeds the second threshold, generate an alarm, generate instructions to shut down the gas turbine system, generate instructions to trip the gas turbine system, or any combination thereof.

2. The haz gas detection system of claim 1, wherein the first threshold comprises a first alarm threshold, and the second threshold comprises a second alarm threshold; wherein the alarm is generated in response the determining that the output of the haz gas sensor exceeds the second threshold; and wherein the second alarm threshold is greater than the first alarm threshold.

3. The has gas detection system of claim 2, wherein the first threshold further comprises a first trip threshold, and the second threshold further comprises a second trip threshold greater than the first trip threshold; wherein the controller is configured to: compare the output of the haz gas sensor to a first trip threshold; compare the output of the haz gas sensor to a second trip threshold; and in response the determining that the output of the haz gas sensor exceeds the second trip threshold, generate the instructions to shut down or trip the gas turbine system.

4. The haz gas detection system of claim 3, wherein the first trip threshold is greater than the first alarm threshold, and wherein the second trip threshold is greater than the second alarm threshold.

5. The haz gas detection system of claim 3, wherein: the first alarm threshold comprises 7% of the lower explosive limit (% LEL); the first trip threshold comprises 11% LEL; the second alarm threshold comprises 14% LEL; and the second trip threshold comprises 27% LEL.

6. The haz gas detection system of claim 1, wherein the haz gas sensor comprises an infrared sensor.

7. A system, comprising: a gas turbine enclosure; a gas turbine engine disposed within the gas turbine enclosure; an exhaust vent duct configured to route a ventilation flow out of the gas turbine enclosure; a sampling conduit in fluid communication with the exhaust vent duct;a haz gas sensor mounted to the sampling conduit, the haz gas sensor having been calibrated with a first gas fuel, wherein the haz gas sensor is configured to contact a sampling flow diverted from the exhaust vent duct and through the sampling conduit, and generate an output indicative of a measured concentration of a gas fuel in the sampling flow; and a controller communicatively coupled to the haz gas sensor, wherein the controller is configured to: receive the output from the haz gas sensor; compare the output of the haz gas sensor to a first threshold, wherein the first threshold is determined for operation of the haz gas sensor with the first gas fuel or a first gas fuel mixture; receive an indication that a second gas fuel or a second gas fuel mixture is being provided to the gas turbine engine; compare the output of the haz gas sensor to a second threshold upon receipt of the indication that the second gas fuel or the second gas fuel mixture is being provided, wherein the second threshold is determined for operation of the haz gas sensor with the second gas fuel or the second gas fuel mixture, the second threshold being shifted from the first threshold; and in response the determining that the output of the haz gas sensor exceeds the second threshold, generate an alarm, generate instructions to shut down the gas turbine engine, generate instructions to trip the gas turbine engine, or any combination thereof.

8. The system of claim 7, wherein the indication that the second gas fuel or the second gas fuel mixture is being provided to the gas turbine engine comprises a valve control signal that corresponds to one or more valves that control flow of the second gas fuel or the second gas fuel mixture to the gas turbine engine.

9. The system of claim 7, wherein the indication that the second gas fuel or the second gas fuel mixture is being provided to the gas turbine engine comprises a measurement by an analyzer configured to measure one or more chemical characteristics of a flow of gas fuel being provided to the gas turbine engine.

10. The system of claim 7, wherein the indication that the second gas fuel or the second gas fuel mixture is being provided to the gas turbine engine comprises a measurement by a flowmeter configured to measure one or more flow rates of a flow of gas fuel being provided to the gas turbine engine.

11. The system of claim 7, wherein the first gas fuel comprises methane, and wherein the second gas fuel comprises propane.

12. The system of claim 7, wherein the first threshold comprises a first alarm threshold, and the second threshold comprises a second alarm threshold; wherein the alarm is generated in response the determining that the output of the haz gas sensor exceeds the second threshold; and wherein the second alarm threshold is greater than the first alarm threshold.

13. The system of claim 12, wherein the first threshold further comprises a first trip threshold, and the second threshold further comprises a second trip threshold greater than the first trip threshold; wherein the controller is configured to: compare the output of the haz gas sensor to the first trip threshold; compare the output of the haz gas sensor to the second trip threshold; and in response the determining that the output of the haz gas sensor exceeds the second trip threshold, generate the instructions to shut down or trip the gas turbine engine.

14. The system of claim 13, wherein the first trip threshold is greater than the first alarm threshold, and wherein the second trip threshold is greater than the second alarm threshold.

15. The system of claim 13, wherein: the first alarm threshold comprises 7% of a lower explosive limit (% LEL); the first trip threshold comprises 11% LEL; the second alarm threshold comprises 14% LEL; and the second alarm threshold comprises 27% LEL.

16. A method, comprising: receiving, from a haz gas sensor calibrated with a first gas fuel, an output indicative of a measured concentration of a gas fuel in a sampling flow diverted from a ventilation flow out of a gas turbine enclosure of a gas turbine engine; comparing the output of the haz gas sensor to a first threshold, wherein the first threshold is determined for operation of the haz gas sensor with the first gas fuel or a first gas fuel mixture; receiving an indication that a second gas fuel or a second gas fuel mixture is being provided to the gas turbine engine; comparing the output of the haz gas sensor to a second threshold upon receipt of the indication that the second gas fuel or the second gas fuel mixture is being provided, wherein the second threshold is determined for operation of the haz gas sensor with the second gas fuel or the second gas fuel mixture, the second threshold being shifted from the first threshold; and in response the determining that the output of the haz gas sensor exceeds the second threshold, generating an alarm, generating instructions to shut down the gas turbine engine, generating instructions to trip the gas turbine engine, or any combination thereof.

17. The method of claim 16, wherein the first threshold comprises a first alarm threshold, wherein the second threshold comprises a second alarm threshold, wherein the alarm is generated in response the determining that the output of the haz gas sensor exceeds the second threshold, the second alarm threshold is greater than the first alarm threshold.

18. The method of claim 17, wherein the first threshold further comprises a first trip threshold, and the second threshold further comprises a second trip threshold greater than the first trip threshold; and wherein the method comprises: comparing the output of the haz gas sensor to the first trip threshold; comparing the output of the haz gas sensor to the second trip threshold; and in response the determining that the output of the haz gas sensor exceeds the second trip threshold, generating the instructions to shut down the gas turbine engine.

19. The method of claim 16, comprising: receiving an indication that the first gas fuel or the first gas fuel mixture is being provided to the gas turbine engine; comparing the output of the haz gas sensor to the first threshold; and in response to the determining that the output of the haz gas sensor exceeds the first threshold, generating the alarm, generating the instructions to shut down or trip the gas turbine engine, or both.

20. The method of claim 16, wherein the first gas fuel comprises methane, and wherein the second gas fuel comprises propane.

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