The technical field generally relates to gas turbines and more specifically relates to gas turbine exhaust.
A gas turbine typically comprises a compressor for compressing air and a combustor where the compressed air from the compressor and gas fuel are mixed and burned. The hot gases from the combustor drive the turbine stages to generate power. Normally, for installed turbines, performance monitoring is done through daily checks and measurements and periodic performance tests. The results are later used for maintenance and repair diagnostic processes. For example, after a fault occurs, the previously recorded trends of the machine are analyzed to identify the cause of failure and maintenance action required to recover from the identified failure.
Methods as described above generally are not able to predict and prevent significant turbine damage. Furthermore, due to inherent time delays associated with analyzing faults, determining failure causes, and identifying corrective action steps, use of present methods often results in undesirable lengths of repair time for critical turbine components.
Disclosed herein are methods and systems for substance profile measurements in gas turbine exhaust. In an embodiment, a method comprises determining a concentration of a substance at a location, identifying the substance at the location as associated with a first combustor component from a plurality of combustor components, and transmitting an alert in reference to the first combustor component when the concentration of the substance crosses a threshold level.
In an embodiment, a system may comprise a subsystem that determines a concentration of a substance at a location in a turbine, a subsystem that identifies the substance at the location as associated with a first combustor component out of a plurality of combustor components, and a subsystem that transmits an alert in reference to the first combustor component when the concentration of the substance crosses a threshold level.
In an embodiment, a system may comprise a plurality of probes, a processor adapted to execute computer-readable instructions, and a memory communicatively coupled to the processor. The memory may have computer-readable instructions that, if executed by the first processor, cause the processor to perform operations comprising determining a concentration of a substance at a location, identifying the substance at the location as associated with a first combustor out of a plurality of combustors, and transmitting an alert in reference to the first combustor when the concentration of the substance crosses a threshold level.
This Brief Description of the Invention is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Brief Description of the Invention is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. Furthermore, the claimed subject matter is not limited to limitations that solve any or all disadvantages noted in any part of this disclosure.
A more detailed understanding may be had from the following description, given by way of example in conjunction with the accompanying drawings wherein:
The combustion gases swirl partially around the axial centerline of the gas turbine 10, as the gases move axially through the turbine 16. This swirl of the combustion gases is due to the rotation of the turbine blades and the expansion of the hot gases moving from stage to stage. The amount of swirl in the combustion gases between the combustion section 12 and exhaust ducts 19 depends on hardware geometry and the operating condition of the gas turbine 10, such as its stage load, duty cycle, ambient temperature and other factors which change the mass flow and density moving through the turbine. When the combustion gases exit the exhaust duct 19, the gases have swirled about the axis of the gas turbine and may not axially align with the combustion chambers that generated the gases.
Analysis of the aforementioned exhaust swirls, for a given hardware design, during the operation of the gas turbine may assist in the determination of defective combustion chambers. A swirl chart may be created for a gas turbine using exhaust thermocouples and parameters that represent mass flow through the turbine. The swirl chart may help determine the originating combustion chamber of the exhaust at a specified fuel load.
The swirl angle may be impacted by the mechanical layout of the buckets (i.e., exit angle), as well as the distance between the last stage bucket of the turbine and exhaust probes. Swirl angle may be a function of the operation of the gas turbine once hardware of the gas turbine is in a fixed or consistent state. At low output, the swirl angle is likely to vary between combustor cans and have a high degree of uncertainty. Historically post event data was used to correlate combustion damage to hot or cold spots in the exhaust temperature to develop a swirl chart. Currently other processes, such as intentional fuel flow manipulations, have been used to develop swirl charts.
Swirl charts may indicate the angle between any combustion chamber and the point where the exhaust from the combustion chamber crosses the exhaust outlet of the gas turbine. In the arrangement described in
The injection of a substance such as a tracer gas or particle may help determine the originating combustion chamber of exhaust at a specified fuel load. In an embodiment, the substance may initially be a liquid or a solid that may transform into a gaseous state or produce a gaseous product, or the like before, after, or during its travel through a combustion chamber.
In an embodiment at block 452, particles may be injected in a similar manner to a tracer gas. The choice of particle may be based on the ability of a particle to survive and not negatively alter combustion. An exemplary detection method may be Rayleigh scattering which may use the particle “talc.” Another exemplary detection method may include the use of fluorescent or luminescent particles. As these particles pass thru a laser light probe, a laser light at a different (e.g., longer) wavelength may be detected, thus enabling a method to detect swirl.
In an embodiment at block 452, N2O may be injected which may result in higher NOx, O2, and other emissions that may be detected after combustion. All emissions (NO, NO2, CO, CO2 & O2) may be monitored. In another embodiment, CO2 may be injected and the emissions monitored. The injection of different gases (N2O or CO2) may cause significantly different shifts in emissions and different directions in reading from the normal combustion operation. A minimal amount of gas may change the emissions, but not significantly change the firing temperature or mass flow. These embodiments, with regard to the injection of CO2, NO2, or the like, may be measured using tunable diode laser absorption spectroscopy (TDLAS) and may impact the temperature of the reaction the least, while shifting emissions. The tracer gas may be injected in one or more combustor locations to enable downstream determination of swirl. The injection may be a steady injection or happen at on-off measurement intervals. The injection amount may be metered to produce a bounded range of downstream concentrations.
At block 454, the tracer gas may be detected by a probe. The probe may operate using TDLAS or a Rayleigh scattering probe, for example. The gas concentration detection probe may be located at the same approximate location as a Tc probe. In an embodiment, the probe may have integrated functions such as the capability of measuring temperature and gas concentration. At block 456, the concentration of the tracer gas and other gases as well as the temperature may be measured an analyzed against a threshold. At block 458, the analysis of the gas concentration and temperature may alert a device and allow the device to determine the likely probe location for the associated nozzle injected with the tracer gas at the load point. At block 460, the swirl angle and load may be determined and recorded. Analysis of circumferential location with higher tracer gas concentrations may be used to determine the swirl angle. In an embodiment, this method may be repeated at different loads in order to create the table or chart that may allow for the determination of a source combustion chamber based on exhaust temperature or exhaust gas concentration at a particular load. Repetition of the method may allow for a more accurate chart.
A measurement array comprising temperature measurement probes (e.g., thermocouple probes) and gas measurement probes (e.g., TDLAS probes) may be at or near the same location in order to more accurately diagnose issues with combustors and other parts of the gas turbine. The gas measurement devices may be tunable diode laser absorption spectroscopy probes or other chemical sensing technology for the detection of gases. Swirl charts may vary based on the design of the gas turbine.
Monitoring and diagnosis of individual combustor chamber problems may be done with further analysis of emissions. A damaged combustor chamber may produce high concentrations of emissions, such as NOx (nitrous oxide), O2 (oxygen gas), or CO (carbon monoxide). Emissions are measured in bulk today with assumed mixing to give average output. Emissions are sensitive to local damage not seen in bulk temperature. A method of combustor to combustor (can-to-can) detection using emission gas measurement may improve ability to assess the health state of individual combustors. Emission concentration measurements may be taken at the thermocouple plane in order to more accurately diagnose combustor issues.
Emission concentration monitoring may allow detection of combustion damage that is not related to changes in air flow and temperature that can be seen by exhaust outlet thermocouples. Combustion hardware damage (e.g., damage to the burner tube, nozzle, or liner) may shows up as increases in NOx or CO. CO turn up is a significant indication of lean blow-out potential and detection of CO, for example, may trigger automated measures to avert a pending blow out. This condition may be true for premixed and diffusion combustors with diluent (water/steam) combustors.
In an embodiment, there may be a system for in-situ measurement of emission. A circumferential profile may be measured in a gas turbine diffuser at an exhaust Tc plane. In-situ measurements may be accomplished by a tunable diode laser absorption spectroscopy (TDLAS) probe. An exhaust Tc shield and mount may be modified to create a fiber-optically fed laser probe that senses the same location of emissions gases as the exhaust thermocouples. The same amount of measurement channels as the exhaust Tc probes may be used for TDLAS probes in obtaining a complete profile. These profiles may be used for combustion hardware diagnostics and tuning purposes. Averaging or otherwise analyzing the emissions data from all probes may allow for a bulk emissions measurement, which may be used for emissions control.
In an embodiment, a specific absorption wavelength may be chosen for each species of gas to be measured. Each of these diodes may be time-division-multiplexed (TDM) or wavelength-division-multiplexed (WDM) into multiple probes. If the wavelengths are sufficiently apart, there is minimal chance of cross-talk for WDM and all the lasers may be run simultaneously for simultaneous emissions species measurements. Otherwise, TDM may be employed. Wavelength of each diode may be swept using a ramped diode injection current input. Gas species may be detected by absorption at a species specific wavelength. The detection sensitivity may be improved by applying ratiometric balanced detection where a reference laser output is used for temporal correlation. Sensitivity of measurements may be further improved by lock-in measurements at sweep frequency and its second harmonic and obtaining the 2f/1f signal ratio (ratio of second harmonic signal to first harmonic signal), which has been shown to be stable and minimally affected by instantaneous noise (vibrations) and drift (thermal). In addition, laser dependent variations may be may be excluded from probe to probe by multiplexing a single laser between all the measurement probes. Multiplexing allows the use of lasers with significantly reduced power in comparison to situations where a plurality of lasers are dedicated to a plurality of probes.
A detector 614 may receive a de-MUXed signal from MUX 615 and a reference signal 612 from TDL device 608 in order to determine the type of gas detected or temperature detected. The processor/controller 602 may be communicatively connected to devices such as the TDL device 608, detector 614, and MUX 615 and may control or process information in connection with the communicatively connected devices. Processor 602 may also be connected to an on-site monitor/gas turbine controller 604 or other gas turbine equipment, which may include equipment that may interact with the combustors of the gas turbine. There may be n number of lasers and detectors (shown as 1:n in
A detector 714 may receive a de-MUXed signal from TDLAS probe 720 and may also receive a reference signal 712 from TDL device 707, in order to determine the type of gas detected or temperature detected. The processor/controller 702 may be communicatively connected to devices such as the TDL device 707, detector 714, and valve control 709. The processor/controller 702 may control or process information in connection with the communicatively connected devices. Processor 702 may also be connected to an on-site monitor/gas turbine controller 704 or other gas turbine equipment, which may include equipment that may interact with the combustors of the gas turbine.
A detector 614 may receive a de-MUXed signal from MUX 814 and a reference signal 812 from TDL device 808 in order to determine the type of gas detected or temperature detected. The processor/controller 802 may be communicatively connected to devices such as the TDL device 808, detector 818, and MUX 814. The processor 802 may control or process information in connection with the communicatively connected devices. Processor 802 may also be connected to an on-site monitor/gas turbine controller 804 or other gas turbine equipment, which may include equipment that may interact with the combustors of the gas turbine.
Systems discussed herein, may allow for real time, in-situ measurement and spatial distribution of emissions gases. Disclosed herein, among other things, is a system for spatially-distinct measurements to assess conditions of individual combustor cans. The system may also have a higher rate of response over methods that use extraction and mechanical devices such as valves and condensers. The fast response of the system may allow for real time, close loop emissions control. Enhanced NH3 control to reduce slip may replace feed forward estimates and calculations.
Combustor reactions may be automated using emission concentrations instead of, or in addition to, exhaust temperature measurements. For example emission concentrations may be used for can-to-can fuel tuning including optimization of emissions and other combustion dynamics rather than the cumulative or average readings of emissions of a gas turbine. The systems disclosed herein may analyze and react to emission readings so that a gas turbine may be tuned based on the emission or other gas readings associated with an individual can (e.g., outlier or dysfunctional can). For example, for CO or lean blow out, the gas turbine may be tuned based emission readings associated with an individual outlier can.
Without limiting the scope, interpretation, or application of the claims appearing herein, a technical effect of one or more of the example embodiments disclosed herein is to provide detection of combustion damage that is not related to changes in air flow and temperature that can be seen by exhaust outlet thermocouples. Another technical effect of one or more of the embodiments disclosed herein is tighter gas turbine and selective catalyst reduction (SCR) systems control may be enabled by real-time measurement of combustion gas composition exiting the gas turbine. The real-time sensor may preclude the need for “NOx forwarding” or complementary filtering.
The computer 920 may further include a hard disk drive 927 for reading from and writing to a hard disk (not shown), a magnetic disk drive 928 for reading from or writing to a removable magnetic disk 929, and an optical disk drive 930 for reading from or writing to a removable optical disk 931 such as a CD-ROM or other optical media. The hard disk drive 927, magnetic disk drive 928, and optical disk drive 930 are connected to the system bus 923 by a hard disk drive interface 932, a magnetic disk drive interface 933, and an optical drive interface 934, respectively. The drives and their associated computer-readable media provide non-volatile storage of computer readable instructions, data structures, program modules and other data for the computer 920.
Although the exemplary environment described herein employs a hard disk, a removable magnetic disk 929, and a removable optical disk 931, it should be appreciated that other types of computer readable media which can store data that is accessible by a computer may also be used in the exemplary operating environment. Such other types of media include, but are not limited to, a magnetic cassette, a flash memory card, a digital video or versatile disk, a Bernoulli cartridge, a random access memory (RAM), a read-only memory (ROM), and the like.
A number of program modules may be stored on the hard disk, magnetic disk 929, optical disk 931, ROM 924 or RAM 925, including an operating system 935, one or more application programs 936, other program modules 937 and program data 938. A user may enter commands and information into the computer 920 through input devices such as a keyboard 940 and pointing device 942. Other input devices (not shown) may include a microphone, joystick, game pad, satellite disk, scanner, or the like. These and other input devices are often connected to the processing unit 921 through a serial port interface 946 that is coupled to the system bus, but may be connected by other interfaces, such as a parallel port, game port, or universal serial bus (USB). A monitor 947 or other type of display device is also connected to the system bus 923 via an interface, such as a video adapter 948. In addition to the monitor 947, a computer may include other peripheral output devices (not shown), such as speakers and printers. The exemplary system of
The computer 920 may operate in a networked environment using logical connections to one or more remote computers, such as a remote computer 949. The remote computer 949 may be a personal computer, a server, a router, a network PC, a peer device or other common network node, and may include many or all of the elements described above relative to the computer 920, although only a memory storage device 950 has been illustrated in
When used in a LAN networking environment, the computer 920 is connected to the LAN 951 through a network interface or adapter 953. When used in a WAN networking environment, the computer 920 may include a modem 954 or other means for establishing communications over the wide area network 952, such as the Internet. The modem 954, which may be internal or external, is connected to the system bus 923 via the serial port interface 946. In a networked environment, program modules depicted relative to the computer 920, or portions thereof, may be stored in the remote memory storage device. It will be appreciated that the network connections shown are exemplary and other means of establishing a communications link between the computers may be used.
Computer 920 may include a variety of computer readable storage media. Computer readable storage media can be any available media that can be accessed by computer 920 and includes both volatile and nonvolatile media, removable and non-removable media. By way of example, and not limitation, computer readable media may comprise computer storage media and communication media. Computer storage media include both volatile and nonvolatile, removable and non-removable media implemented in any method or technology for storage of information such as computer readable instructions, data structures, program modules or other data. Computer storage media include, but are not limited to, RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital versatile disks (DVD) or other optical disk storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other medium which can be used to store the desired information and which can be accessed by computer 920. Combinations of any of the above should also be included within the scope of computer readable media that may be used to store source code for implementing the methods and systems described herein. Any combination of the features or elements disclosed herein may be used in one or more embodiments.
In describing preferred embodiments of the subject matter of the present disclosure, as illustrated in the Figures, specific terminology is employed for the sake of clarity. The claimed subject matter, however, is not intended to be limited to the specific terminology so selected, and it is to be understood that each specific element includes all technical equivalents that operate in a similar manner to accomplish a similar purpose.
This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention 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 languages of the claims. As used herein, an element or function recited in the singular and proceeded with the word “a” or “an” should be understood as not excluding plural said elements or functions, unless such exclusion is explicitly recited. Furthermore, references to “one embodiment” of the claimed invention should not be interpreted as excluding the existence of additional embodiments that also incorporate the recited features.