Abstract:
A system and method disclosed may include a dynamic pressure sensor or probe having a wave guide and wave guide tube and a temperature sensor disposed therethrough in order to optimally install and position the temperature sensor to measure combustor flame characteristics. The dynamic pressure sensor is preferably positioned or mounted on the outer casing of the combustor. By taking advantage of the placement of an existing dynamic pressure sensor, a temperature sensor—for instance a fine wire temperature probe—can be disposed through the interior of the dynamic pressure sensor so that combustion flame characteristics can be measured near the combustion liner.

Description:
FIELD OF THE DISCLOSURE 
       [0001]    The present disclosure generally relates to environmental sensors for internal combustion engines, and, more particularly, methods for installing temperature sensors in order to measure the characteristics of a combustor flame for a gas turbine. 
       BACKGROUND 
       [0002]    Combustors on both new and upgraded industrial gas turbines have recently and increasingly utilized Dry Low NOx combustion systems (“DLN combustors” or “DLN combustion systems”). DLN combustors employ lean, premixed combustion for achieving low nitrogen oxide (“NOx”) and carbon monoxide (“CO”) emissions. DLN combustors have also been utilized in order to comply with more strict regulations for pollutant emissions. The cooler flame temperatures of the lean premixed flames of DLN combustors are the primary mechanism for producing lower NOx levels. As a result, DLN combustors have largely replaced standard diffusion combustors that employ water or steam injection for achieving reduction in NOx emissions. 
         [0003]    Many features in DLN combustors make them more complex systems to operate and control than standard diffusion combustors. The increased complexity of DLN combustors may therefore impact the operability, flexibility, and reliability of a gas turbine with which the DLN combustor is installed. Thus, operating and maintenance practices, which would be acceptable or have no negative impact with standard diffusion combustors, are not acceptable when DLN combustors are installed. 
         [0004]    For example, modern gas turbines equipped with DLN combustion systems suffer the problem of thermo-acoustic combustion instability. The acoustic characteristics of the combustion chamber, as well as the response of the combustion flame to the fluctuations of pressure, all play a fundamental role on the conditions which may occur when DLN combustion systems are affected by combustion instabilities. Indeed, thermo-acoustic interaction between acoustic pressure oscillations and flame heat release fluctuations are often regarded as the main origin of combustion instabilities in gas turbines. These instabilities must be avoided since they may generate structural vibrations that, in some cases, may lead to failure of the system. 
         [0005]    Issues in detecting and controlling combustion instability have existed ever since flames have been confined within ducts. These instabilities occur in many types of combustion system from domestic heating systems to rocket motors and gas turbines. In order to detect and prevent these instabilities from occurring, dynamic pressure sensors are often utilized in gas turbine DLN combustion chambers to detect initial combustion instability. If these instabilities are detected at an early stage, the turbine can be adjusted with little effort for smooth and steady combustion. 
         [0006]    These dynamic pressure sensors measure and acquire pressure-related environmental data which may be used to confirm proper operational health of the combustion system, and which can also be used to tune the gas turbine engine so that it is operating with an appropriate balance between combustion dynamics and emissions. 
         [0007]    In addition to measuring dynamic pressure, the determination of flame temperature has historically been attributed great importance in the field of combustion technology. Flame temperature is directly correlated with the chemical reaction kinetics and the formation of pollutants such as, for example, NOx. Moreover, knowledge of the release of energy during the combustion process is indispensable for the design of combustion chambers and determination of the mechanical and the thermal loads of all components utilized in the combustion system. U.S. Patent Pub. No. 2012/0196234 to Bulat et al., the entire contents of which are herein incorporated by reference, discloses several possible positions for a temperature sensor to be used with a combustion chamber. U.S. Pat. No. 5,828,797 to Minott et al., the entire contents of which are herein incorporated by reference, discloses the continuous optical monitoring of the combustion process within an igniter port or a pilot flame port. Other references which generally disclose the desirability to obtain temperature data as part of the combustion process include U.S. Pat. No. 6,546,556 to Ginter and U.S. Patent Pub. No. 2011/0093182 to Weber et al., the entire contents of each are herein incorporated by reference. 
       BRIEF SUMMARY OF THE DISCLOSURE 
       [0008]    The following disclosure presents a summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not an extensive overview of the invention. It is intended to neither identify critical or necessary elements of the invention nor delineate the scope of the invention. Its sole purpose is to present some concepts of the invention in a simplified form as a prelude to the more detailed description that is presented later. 
         [0009]    An embodiment of a system for measuring the characteristics of a combustor flame is provided herein in accordance with the disclosure, the system including a combustion can that is operatively connected to a gas turbine, said combustion can having an outer casing; a dynamic pressure sensor mounted to and operatively connected to said outer casing of said combustion can, wherein said dynamic pressure sensor further comprises a wave guide and wave guide tube; and a temperature sensor disposed through said wave guide and waive guide tube. The combustion can and the gas turbine may further include a dry, low NOx combustion system. The pressure sensor may further include a piezoelectric dynamic pressure sensor. The pressure sensor may further include an end piece. The end may include a channel disposed therein. The temperature sensor may further include a fine wire temperature sensor. The temperature sensor may by disposed through the channel of the end piece. 
         [0010]    In another embodiment of the disclosure, a method is provided for measuring the characteristics of a combustor flame, the method including the steps of operatively connecting a gas turbine to a combustion can having an outer casing; mounting and operatively connecting a dynamic pressure sensor to said outer casing of said combustion can, wherein said dynamic pressure sensor further includes a wave guide and wave guide tube; and disposing a temperature sensor through said wave guide and said waive guide tube. The method may further include the step of disposing the temperature sensor through a channel disposed in an end piece of the dynamic pressures sensor. 
         [0011]    The following description and the annexed drawings set forth in detail certain illustrative aspects of the invention. These aspects are indicative, however, of but a few of the various ways in which the principles of the invention may be employed and the present invention is intended to include all such aspects and their equivalents. Other advantages and novel features of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0012]    The disclosure will be further understood, by way of example, with reference to the accompanying drawings, which may not be drawn to scale, in which: 
           [0013]      FIG. 1  depicts a cross-sectional view of a combustion chamber and gas turbine; 
           [0014]      FIG. 2  depicts a perspective view of the combustion can; 
           [0015]      FIG. 3  depicts cross-sectional view of an embodiment of a sensor system; 
           [0016]      FIG. 4  depicts a close-up view of an embodiment of a dynamic pressure sensor having a fine wire temperature sensor drawn therethrough; and 
           [0017]      FIG. 5  depicts a perspective view of a combustion can having an embodiment of a dynamic pressure sensor and fine wire temperature sensor mounted thereon. 
       
    
    
     DETAILED DESCRIPTION 
       [0018]    The following detailed description and the appended drawings describe and illustrate some embodiments of the invention for the purpose of enabling one of ordinary skill in the relevant art to make and use the invention. As such, the detailed description and illustration of these embodiments are purely illustrative in nature and are in no way intended to limit the scope of the invention, or its protection, in any manner. It should also be understood that the drawings are not to scale and in certain instances details have been omitted, which are not necessary for an understanding of the present invention, such as details of fabrication and assembly. In the accompanying drawings, like numerals represent like components. 
         [0019]    With reference to  FIG. 1 , a combustion chamber  101  generally comprises a combustion liner  103  encased by a flow sleeve  105 . The flow sleeve  105  may also be encased by an outer casing  107 . Combustion chamber  101  may be generally characterized as elongate, or substantially elongate, having an upstream end proximate to an ignition point as well as a downstream end distal to the ignition point. The upstream end of the outer casing  107  may further include a combustion cover  109  having a plurality of nozzles  111  for injecting fuel, air, water, and/or another fluid into the combustion chamber as part of the combustion process. Embodiments of combustion chamber  101 , as described herein, may also be referred to as a combustion can  101 . 
         [0020]    With reference now to  FIG. 2 , industrial gas turbines may comprise a plurality of combustion cans  101  arranged, for instance and as shown in the illustrated embodiment, in a circular array. Each combustion can  101  may be connected to a common downstream location on the engine, which for instance may be a housing for a plurality of pistons or other engine components. A measurement system  200  for detecting or observing the environmental status of one of the combustion cans  101  may include one or more dynamic pressure sensors  201 . A variety of position or placements for dynamic pressure sensor  201  are contemplated within the disclosure. The disclosure further contemplates that measurement system  200  may include more than one dynamic pressure sensor  201 , for instance at any one of the variety of possible positions disclosed herein. In one embodiment, pressure sensor  201  may be mounted on the outer casing  107  of the combustion can, downstream of the combustion cover  109 . In another embodiment, the dynamic pressure sensor  201  may be mounted on or otherwise operatively connected to the injector body. As illustrated in  FIG. 2 , an embodiment of system  200  includes the dynamic pressure sensor  201  mounted on and operatively connected to the outer casing  107  of the combustion can  101  by and through a sensor port  113  extending into the liner  103 . Sensor port  113  may be pre-manufactured in commercial embodiments of combustion chamber  101 . Regardless of its location, the dynamic pressure sensor  201  may be adapted to detect changes in pressure within or proximate to combustion chamber  101 , for instance by being configured to detect thermo-acoustic pressure oscillations within the combustion chamber. 
         [0021]    The dynamic pressure sensor  201  may be in the form of an acoustic microphone that employs a piezoelectric dynamic pressure sensor. The dynamic pressure sensor  201  may also be supported with a protective enclosure that is adapted for high temperature operation within the combustion chamber of a gas turbine engine. An example of a dynamic pressure sensor is disclosed in U.S. Pat. No. 6,928,878 to Eriksen et al., the disclosure of which is incorporated herein by reference in its entirety. An example of a temperature resistant semiconductor support framework for a dynamic pressure sensor is disclosed in U.S. Pat. No. 6,773,951 to Eriksen et al., the disclosure of which is also incorporated herein by reference in its entirety. It is envisioned and well within the subject disclosure that alternative known or to be developed high temperature dynamic pressure sensors may be employed including, for example, PCB sensors (manufactured by PCB Piezoelectronics, Depew, N.Y., USA) and vibrometers. 
         [0022]    With reference to  FIG. 3 , the dynamic pressure sensor  201  disclosed herein generally comprises a housing and inner sensing portion  203 . The pressure sensor  201  may further include a wave guide  205  and wave guide tube  207 . Wave guide  205 , as shown and described, may pass through at least a portion of housing and wave guide tube  207 . In one embodiment, wave guide tube  207  and housing are the same component, although in other embodiments a separate wave guide  207  may be disposed within inner sensing portion  203 . The wave guide  205  and wave guide tube  207  may be operatively connected to outer casing  107  and terminate at, or penetrate through, the combustion liner  103  so as to collect environmental data from the combustion chamber  101  at or beyond liner  103 . Accordingly, pressure sensor  201  may extend passed flow sleeve  105  and outer casing  107 . A temperature sensor  215  may be provided within at least a portion of dynamic pressure sensor  201 . As such, a sensor system may include a pressure sensor  201  and a temperature sensor  215 . Wave guide  205  may be provided in order to guide temperature sensor  215  into at least a portion of the housing and into inner sensing portion  203 . As described herein, temperature sensor  215  may also be inserted through wave guide  205 . A single wave guide  205  and wave guide tube  207  may be utilized for both pressure sensor  201  and temperature sensor  215  or, alternatively, a first wave guide may be used in association with pressure sensor  201  while a second wave guide may be used in association with temperature sensor  215 . 
         [0023]    With reference to  FIG. 4 , sensing system  200  may further include a temperature sensor  215 , which, for instance, may be disposed within the wave guide  205  and wave guide tube  207  of the dynamic pressure sensor  201 , the wave guide  205  and wave guide tube  207  having a sufficient diameter to permit the temperature sensor  215  to be inserted therethrough within the wave guide tube  205 . The temperature sensor  215  may be a fine wire sensor that may be disposed within the wave guide tube and exits the dynamic pressure sensor through a channel in the pressure sensor&#39;s end piece  211 . In one embodiment, the outer diameter of the wave guide tube  207  may have a diameter of approximately ¾ inch while the channel in the pressure sensor&#39;s end piece  211  may be approximately ¼ inch, and wave guide  205  and temperature sensor  215  each have a diameter of approximately ⅛ of an inch. The temperature sensor may detect flame characteristics relating to combustion characteristics such as an equivalence ratio and temperature. In particular, the temperature sensor may be adapted and configured to detect spectral and/or thermal characteristics of the combustor flame that occur downstream from the combustion cover. Temperatures within the combustion chamber  101  may be between 2450 degrees Fahrenheit and 3000 degrees Fahrenheit. As such, embodiments of a temperature sensor  215  must be able to withstand and operate at these high temperatures. Temperature sensor  215  may be constructed of multiple materials. For instance, temperature sensor  215  may be constructed from a first material having lower temperature threshold and a second material having a higher temperature threshold, the second material being the portion of temperature sensor  215  extending towards are past liner  103  into chamber  101 . In embodiments where temperature sensor  215  is comprised of two materials, the first and second materials may be joined at a point within inner sensing portion  203 . The pressure sensor  201  may further include an end piece  211  and locking nut  213  which may secure the end piece  211  to the housing and inner sensing portion  203 . 
         [0024]    With reference to  FIG. 5 , the temperature sensor  215  may be disposed through the dynamic pressure sensor  201  mounted on the outer casing  107  of the combustion can  101 . In the illustrated embodiment, the dynamic pressure sensor  201  is mounted on a sensor port  113 . The resulting sensor system  200  permits a multi-faceted environmental reading to be taken from combustion chamber  101 . Environmental data, including both pressure and temperature readings, taken from combustion chamber  101  may be particularly useful in troubleshooting failures or error sources in a multi-combustor gas turbine. Where, for instance, a single combustor  101  in a combustor array is malfunctioning, direct environmental measurement of each combustor  101  will permit an operator to identify sources of malfunctions not readily apparent by a downstream measurement. It has been estimated that direct environmental measurement of a combustion chamber in a multi-combustor turbine may reduce operating costs by approximately sixty six percent. 
         [0025]    The descriptions set forth above are meant to be illustrative and not limiting. Various modifications of the invention, in addition to those described herein, will be apparent to those skilled in the art from the foregoing description. Such modifications are also intended to fall within the scope of the concepts described herein. The disclosures of each patent, patent application and publication cited or described in this document are hereby incorporated herein by reference, in their entireties. 
         [0026]    The foregoing description of possible implementations consistent with the present disclosure does not represent a comprehensive list of all such implementations or all variations of the implementations described. The description of some implementation should not be construed as an intent to exclude other implementations. For example, artisans will understand how to implement the invention in many other ways, using equivalents and alternatives that do not depart from the scope of the invention. Moreover, unless indicated to the contrary in the preceding description, none of the components described in the implementations are essential to the invention. It is thus intended that the embodiments disclosed in the specification be considered as illustrative, with a true scope and spirit of the invention being indicated by the following claims.