BACKGROUND

1. Field [0001] Disclosed embodiments are generally related to gas turbine combustors and, more particularly, to sensors used with gas turbine combustors.

2. Description of the Related Art

[0002] One of the problems with running gas turbine combustors tuned for low emissions is the increased possibility of getting combustion anomalies such as flashbacks or lean blow outs. These anomalies can occur more frequently due to the gas turbine combustors running at very lean conditions. These anomalies can be harmful to the combustor units as well as to the safety of the operators. While flashback sensors have previously been proposed they have not been effective in fully detecting the onset of a flashback event. For example, thermocouple sensors have been used; however they have relatively slow reactions times. Also, these types of sensors only protect a highly localized area.

[0003] Other types of sensors beside thermocouple sensors have been used for flashback detection. However they have been incorporated into the support housing of combustor baskets, such as on the fuel rockets of a combustor. Although this is an astute way of implementing sensors, doing makes the combustor basket cumbersome and prohibitively costly. Further, the sensing range of the sensors is very limited thereby reducing the overall efficiency of a flashback detection event. The resulting sensors function as point sensors having a limited range of only a few millimetres. In practice these sensors are as effective or on par with thermocouple sensors for detecting flashback. Therefore there is a need to reliably and quickly detect and warn operators about these anomalies in the gas turbine combustor.

[0004] Also important in the continuous operation of gas turbine combustors is monitoring of the flame igniter's health over time. Monitoring of a flame igniter's health can insure that gas turbine combustors are not needlessly taken offline due to false readings. Such detection of fail rates has become an increasingly important problem as the current failure rate of igniters has increased.

[0005] Therefore there is a need for sensors that are able to address combustion anomalies and ignition issues within gas turbine combustors.

SUMMARY

[0006] Briefly described, aspects of the present disclosure relate to combustor sensor systems. [0007] An aspect of the disclosure provides a sensor system having an ion sensor locatable within a combustor for detecting anomalies in a combustor, wherein the ion sensor comprises an electrode and an insulator surrounding the electrode, wherein the ion sensor detects ions substantially throughout a chamber of the combustor. The system also has a controller operably connected to the ion sensor. [0008] Another aspect of the disclosure provides a sensor system having an ion sensor locatable on an igniter used with combustors, wherein the ion sensor comprises an electrode and an insulator. The system also has a controller operably connected to the ion sensor.

[0009] Still yet another aspect of the disclosure is a sensor system having an ion sensor locatable within a combustor, wherein the ion sensor comprises an electrode and an insulator, wherein the ion sensor generates an electric field that extends greater than 5 mm from a surface of the ion sensor. The system also has a controller operably connected to the ion sensor.

BRIEF DESCRIPTION OF THE DRAWINGS [0010] Fig. 1 shows a cross-sectional view of a combustor ion sensor system in accordance with an embodiment of the present invention.

[0011] Fig. 2 is a view of the combustor ion sensor system shown in Fig. 1 as seen from the combustion chamber.

[0012] Fig. 3 shows a cross-sectional view of a combustor ion sensor system in accordance with another embodiment of the present invention.

[0013] Fig. 4 is a view of the combustor ion sensor system shown in Fig. 3 as seen from the combustion chamber.

[0014] Fig. 5 is a view of the combustor from the combustion chamber.

[0015] Fig. 6 is flow chart showing a method for detecting ions in a combustor.

[0016] Fig. 7 is a view of a combustor ion sensor system in accordance with another embodiment of the present invention.

[0017] Fig. 8 is a view of an igniter used in the combustor ion sensor system shown in Fig. 7.

[0018] Fig. 9 is an alternative embodiment of a combustor ion sensor system used with an igniter.

[0019] Fig. 10 is another alternative embodiment of a combustor ion sensor system used with an igniter.

[0020] Fig. 1 1A is a circuit diagram useable in the combustor ion system shown in any one of Figs. 7-9.

[0021] Fig. 1 IB are graphs of current versus time of the exemplary current and measured current from the igniter and circuit shown in Fig. 1 1A.

[0022] Fig. 12 is a flow chart showing the method for determining the status of an igniter.

DETAILED DESCRIPTION [0023] To facilitate an understanding of embodiments, principles, and features of the present disclosure, they are explained hereinafter with reference to implementation in illustrative embodiments. Embodiments of the present disclosure, however, are not limited to use in the described systems or methods. [0024] The components and materials described hereinafter as making up the various embodiments are intended to be illustrative and not restrictive. Many suitable components and materials that would perform the same or a similar function as the materials described herein are intended to be embraced within the scope of embodiments of the present disclosure. [0025] An embodiment of the present disclosure sets forth a gas turbine combustor that employs ion sensors that provide reliable detection of a combustion anomaly, e.g. flashback, etc. A gas turbine combustor may be constructed with a combustor ion sensor system in place. In some instances, a combustor ion sensor system in accordance with the present disclosure can be achieved by providing a modification to the gas turbine combustor. The modification can provide more coverage and faster response time for sensing combustion anomalies than that which is found in previous combustors. Another embodiment of the present invention can employ the same sensor principles in order to provide reliable monitoring of the flame igniter's performance and provides information on its health that can warn the operator or customer of a future failure of the combustor's igniter system.

[0026] Now referring to the drawings wherein embodiments of the present invention are shown, Fig. 1 shows a cross-sectional view of combustor ion sensor system 100 located within a combustor. The combustor ion sensor system 100 is able to provide sensing of the ion discharge from a combustor flame 1 1. When a threshold level of ions is sensed the combustor ion sensor system 100 is able to take measures to protect components of the combustor from an irregular combustion output, such as a flashback occurrence. Because an ion sensor system 100 is being used measures may be taken quicker than with other sensor systems, thus potentially preserving more of the system. [0027] In practice the combustor ion sensor system 100 is able to take a baseline measurement of the ions discharged from a combustor during typical operation. The baseline measurement can be used to establish a threshold level. The baseline may be obtained at a time when the combustor is operating properly without any apparent adverse effects. The range of the baseline may also be the sensor signal measured at different loads with a factor of safety. For example, 150 % of the measured signal can be used as the baseline. The baseline may also be established during initial testing of the combustor. Also, the baseline may be established, or re-established at various times during the operation of the combustor. This is used to establish the threshold. If the threshold is exceeded the fuel to the combustor can be withdrawn, or the combustor otherwise shut down prior to any potential damage occurring. Alternatively, the combustor ion sensor system 100 can operate by detecting a specific metric related to the ions detected, such as change in number of ions detected, rate of change in number of ions detected, etc. The combustor ion sensor system 100 may also function without first establishing a threshold level and may simply detect any increase in the ions sensed and thus take action to protect the combustor upon detection of ions.

[0028] Figs. 1 and 2 show the combustor ion sensor system 100 having a controller 5, an electrode 10, an electrode insulator 12 and a cable 17. The electrode 10 and electrode insulator 12 comprise the ion sensor 15. The electrode 10 can be located on or integrated into the chamber wall 18. Surrounding the electrode 10 is an electrode insulator 12 which separates the electrode 10 from the chamber wall 18. The chamber wall 18 is grounded via ground wire 14. The ion sensor 15 is located behind the direction in which the combustor flame 1 1 is directed in order to detect a combustion anomaly, such as flashback. The electrode 10 may be made of any material suitable for detecting ions in this environment. The electrode insulator 12 may be made of any material suitable for insulating the electrode 10, such as any type of high temperature material such as alumina, SiC based materials or ceramics, e.g. AI2O3.

[0029] In the embodiment shown in Figs. 1 and 2 the ion sensor 15 forms a disc shape with the electrode 10 in the center of the disc and the electrode insulator 12 surrounding the electrode 10. The disc shape of the ion sensor 15 enables the generation of an electric field 13 and greater ability to detect ions generated by the combustor flame 1 1, such as OH and CH ions, than point sensors. The disc may have a diameter of between 1 15%- 125% of the allowable distance that a flame could come near the back surface of a combustor without increasing its temperature beyond a critical design temperature for the ion sensor 15 or exceeding the threshold level. For example the diameter of the sensor may be greater than 5 mm, or preferably greater than 10 mm. However, it should be understood that the diameter of an ion sensor 15, that is disc shaped may tailored for the size and shape of the combustor that is used. The increased ability to detect ions is due to the larger surface area provided by disc shaped electrode 10 and the role the larger surface area plays in generating the electric field 13. The electric field 13 enables a sensing range of greater than 5 mm and preferably greater than 10 mm from the surface of the electrode 10. The sensing range is the radius, or largest distance of the field extending from the ion sensor 15. For example, to obtain a sensing range of greater than 10 mm an ion sensor 15 that is disc shaped would have a diameter of 1 1.5 to 12.5 mm.

[0030] Other geometries for the electrode 10 may be used as well, such as rectangular, oval, polygonal, or irregular shaped. The disc shaped geometry of electrode 10 makes it easier to retrofit existing combustors and work within existing systems. It should be understood that while one ion sensor 15 is shown in Fig. 1, more than ion sensor 15 may be used in the combustor.

[0031] The electrode 10 is connected to a cable 17, which in the embodiment shown, is a coaxial cable comprising a wire 19 and insulator 16 surrounding the wire 19. Contact 21 shown in Fig. 2 shows where wire 19 contacts the electrode 10. The cable 17 provides the voltage and receives the signal from the ion sensor 15. The cable 17 may carry the signal to a controller 5 where the signal can be used in order to determine whether or not measures should be taken to respond to the combustion anomaly. For example, the controller 5 may determine that fuel should cut off to prevent further combustion. Controller 5 may be a processor, circuit component, distributed network, or other component that is capable of providing the logic that governs the combustor ion sensor systems.

[0032] Figs. 3-5 show combustor ion sensor system 200, which is an alternative embodiment of the system shown in Figs. 1 and 2. In combustor sensor system 200 the electrode 20 forms a continuous ring around the circumference of the combustor. Surrounding electrode 20 is insulator 22, which together form the ion sensor 25. The ion sensor 25 is located behind the direction in which the combustor flame 1 1 is directed.

[0033] The continuous ring is shown in Fig. 5, where the pilot nozzle 24 and main nozzles 26 of the combustor are also shown. While the electrode 20 is formed as a continuous ring, it should be understood that the ring need not be continuous and may instead, for example, include a number of electrodes that are electrically connected around the circumference of the combustor.

[0034] Similar to combustor ion sensor system 100 shown in Figs. 1 and 2, combustor ion sensor system 200 is able to detect the ions that are emitted during a flashback scenario in a combustor. This is accomplished by the increased electric field and ability to detect ions over a greater area than that which is provided by point sensors or thermo-coupled sensors.

[0035] Now turning to Fig. 6, a flow chart showing the method for detecting the ions generated by combustion anomalies is shown. In practice, the combustor ion sensor systems 100 and 200 generate an electric field 19 using the ion sensors 15 or 25. The electric field 19 extracts charges from the flame. During operation as long as the rate of charge extraction is small compared to the ionization rate in the flame, the flame remains quasi-neutral. An electric current flow is established between the sensors 15 or 25 and the flame.

[0036] In step 251, the combustor ion sensor systems 100, or 200 detects ions emitted during combustion. As discussed above this occurs when ions emitted by the combustion process enter the electric field 13 generated by the ion sensors 15 or 25. In step 252 the detected ions are compared to a threshold level of ions. The threshold level of ions may be a predetermined threshold set. For example the threshold may be preset level of ions, or a preset determination of the change in rate of ions detected. In step 253, the combustion anomaly is stopped in response to the detected ions. For example the fuel level being supplied to the combustor may be adjusted.

[0037] Now referring to Figs. 7-10, shown is combustor ion sensor system 300. In the application of the combustor ion sensor system 300 the ion sensors 35 are used with an igniter 31 which is located within the housing 36 in Fig. 7. In combustor ion system 300 an electrode 30a, 30b or 30c is located proximate to the ignition electrode 34. The electrodes 30a, 30b or 30c are used as part of the ion sensor 35, which can include an insulator 32 and cable 17 connected to the electrode 30a, 30b, or 30c. The ion sensor 35 may also be referred to colloquially as "penny" or "stripe" sensors.

[0038] In Fig. 8, electrode 30a is shown to be oval shaped and located on the exterior of the cylindrical housing 33 of the igniter 31. In Fig. 9, electrode 30b is shown to be located on the tip 37 of the igniter 31 adjacent, or near to the ignition electrode 34. The closer the ion sensor 35 is to the tip 37 of the igniter 31 the better it is for detection of ions. In Fig. 10, electrode 30c is shown to be located as a ring encircling the circumference of the tip 37 of the igniter 31. While electrode 30c is shown to be a continuous, it is possible to provide an electrically connected ring of electrodes. The electrode 30c in Fig. 10 can provide a stronger signal with a larger detection zone than the electrodes 30a and 30b. While various geometries are shown for the electrodes in Figs. 8-10, it should be understood that other geometries may be employed.

[0039] Similar to the other combustor ion sensor systems described herein, the combustor ion sensor system 300 is able to detect ions being emitted, in this instance from the igniter 31. In particular, in the case of a lean blow out, the ion sensor 35 will provide a drop in signal due to lack of ions because of a blown out flame. Also, the ion sensing time series signal can be analyzed in real time in the frequency domain. This is in part due to the ability of the ion sensing signal capable of being monitored at very high frequencies, such as for example frequencies in excess of 20 Khz. Analyzing the time series signal can provide accurate information on a blown out flame by the shift and/or disappearance of certain frequency bands.

[0040] The response time of the ion sensor 35 is in milliseconds or faster as the sensor 35 measures the current. Additionally, the ion sensor 35 is also able to monitor the health of the igniter 31 by periodically comparing the ions detected to the previously measured ions from the igniter 31. The measurement of the ionization strength can determine when there is potentially imminent failure of the igniter 31. [0041] Fig. 11A shows a circuit diagram that may be used in exemplary embodiments of the ion sensor system 300 and a graph. By using the circuit diagram shown in Fig. 1 1 A an additional circuit is created using the same components of the igniter 31 to measure the intensity of the spark of the igniter 31. Fig. 1 1B shows an exemplary graph illustrating the current of the igniter 31 and the measured current of the igniter 31 that is processed by the controller 5. Fig. 11A shows controller 5 and igniter 31 connected in a circuit having circuit components, resistors 41, capacitors 42, amplifiers 43 and inductors 44. Inductors 44 are used to create a stepped up Fourier transform function. Now turning to Fig. 12, a flow chart showing the method for determining the status of the igniter 31 in the combustor is shown. In practice, the combustor ion sensor system 300 generates an electric field using the ion sensors 30a, 30b or 30c which is used to detect ions.

[0042] In step 351, a baseline level of the ions emitted by the igniter 31 is established. The baseline level may be stored at the controller 5. The signal from the ion sensor 35 may be baselined using a fully functional operating signal from an igniter 31. In addition to frequency monitoring, several other features of the frequency domain may be analyzed. This can be done by correlating (e.g by providing a similarity analysis) the baselined signal with the currently received signal. The correlation function will drop as the igniter gets older or functions in a progressively poorer manner. The correlation function will provide information on the health of the igniter 31 as well as, for example, a drop in intensity of the igniter 31 and misfiring of the igniter 31. In step 352 ions emitted from the igniter 31 are detected, providing the currently received signal. In step 353 the status of the igniter 31 is determined based on the emitted ions. The status determination may be done periodically or continuously. The detected levels of ions may be compared to previously detected levels of ions in order to establish the health of the igniter 31, using, for example the correlation function discussed above. The determination of status may be done by the controller 5. The status of the igniter 31 may be selected statuses such as near failure, need of maintenance or failure to ignite. Thus the determined threshold can provide early indication to an operator that the igniter 31 is in need of maintenance. The ion sensor 30a, 30b or 30c can also be used to ensure that the igniter 31 is still lit thereby preventing needlessly shutting down a combustor due to false readings of the combustor being lit.

[0043] While embodiments of the present disclosure have been disclosed in exemplary forms, it will be apparent to those skilled in the art that many modifications, additions, and deletions can be made therein without departing from the spirit and scope of the invention and its equivalents, as set forth in the following claims.