Abstract:
An actively cooled turbine sensor assembly is designed to withstand post-combustion gas-path conditions of gas turbine engines. The housing forms part of a cooling system and includes an elongated tubular structure that may be inserted into the hot flow path. The distal end portion of the sensor assembly is contoured to minimize heat transfer. The housing also includes leading and trailing plenums for flowing cooling air through the housing and out through the distal end portion. Additional side cavities may also be provided for active cooling of the sensor and reducing possible heat conduction paths to the sensor.

Description:
TECHNICAL FIELD 
       [0001]    This disclosure relates generally to gas turbine engines, and specifically to sensor probes for measuring operating conditions in a combustion gas flow path through a turbine of a gas turbine engine. 
       BACKGROUND 
       [0002]    Gas turbine engines suitable for use in aircraft type applications can presently be placed into one of three broad categories, namely turbojet, turbofan and variable cycle engines. Turbojet engines typically include a rotatable compressor, a combustor and a rotatable high pressure turbine which is connected to the compressor by a shaft to form a spool. In operation, the rotating compressor blades raise the temperature and pressure of air entering the turbojet engine. Fuel is mixed and burned with the air in the combustor. Some of the energy of the rapidly expanding gases exiting the combustor is converted by the turbine into rotation of the shaft which, in turn, rotates the compressor. The gases exit the turbojet engine through a nozzle such that the gases provide a force, or thrust, to the engine. 
         [0003]    In contrast, turbofan engines typically include a fan assembly disposed upstream of two or more compressors that are each coupled to one of two or more turbines via coaxial shafts to form two or more coaxially nested spools. For example, a typical turbofan engine includes a low pressure compressor (LCP) coupled to a low pressure turbine (LPT) to form one spool. Downstream of the LPC is a high pressure compressor (HPC) coupled to a high pressure turbine (HPT) disposed upstream of the LPT to form another spool. The combustor is disposed between the HPC and HPT. The spools operate at different pressures and temperatures and rotate at different speeds. Further, in both turbojet and turbofan engines, individual compressors and turbines are subdivided into a number of stages, which are formed of alternating rows of rotor blades and stator vanes. 
         [0004]    In a turbofan engine, a portion of the air passing through the fan assembly by passes the engine core and enters an outer air duct while the remaining air enters the LPC. The turbofan engine bypass ratio refers to the ratio of the air flow through the outer duct divided by the air flow though the turbofan engine core. High bypass ratio turbofan engines accelerate a very large mass of air to relatively low exhaust gas velocities. High bypass turbofan engines are better suited for low aircraft speeds where adequate specific thrust can be provided with reduced noise because of the lower exhaust gas velocities. In contrast, low bypass turbofan engines have low air mass flow rates and high exhaust gas velocities. Low bypass turbofan engines and turbojet engines are better suited for high aircraft speeds because of their high exhaust gas velocities. 
         [0005]    A third category of aircraft gas turbine engines are known as variable cycle gas turbine engines, which combine the operational characteristics of turbojet or low bypass turbofan engines with the operational characteristics of high bypass turbofan engines. High performance variable cycle gas turbine engines are being designed because of their unique ability to operate efficiently at various thrust settings and flight speeds, both subsonic and supersonic. An important feature of the variable cycle gas turbine engine is its capability of maintaining a substantially constant inlet airflow as its thrust is varied. This feature leads to important performance advantages under less than full power engine settings or at maximum thrust conditions, such as during subsonic cruise. 
         [0006]    For example, a variable cycle turbofan engine may include a core engine, first and second fans, and first and second fan bypass ducts. Both fans may have variable pitch inlet guide vanes and variable pitch stator vanes. By varying the pitch of the vanes in the first and second fans, the engine may operate in high bypass and low bypass modes, thereby providing a single engine which is efficient at both low and high aircraft flight speeds respectively. The outer duct walls may be provided with one or more inlets and discharge outlets which can provide additional air to the second fan assembly, depending upon the operational requirements of the engine. Further, U.S. Pat. No. 8,082,727 discloses a variable cycle gas turbine engine with a peripheral duct that receives peripheral inlet air, an auxiliary fan and an auxiliary turbine. The auxiliary turbine is connected to the aft end of the core engine and is configured to receive combustion gases for driving the auxiliary fan that receives air from the peripheral duct. Similarly, U.S. Pat. No. 8,127,528 includes an auxiliary combustor and an auxiliary propulsor or fan disposed in the peripheral duct. Other variable cycle engine designs have been developed and are too numerous to mention here. 
         [0007]    Variable cycle engines, with modulated flow areas and geometries, can achieve higher efficiencies than current turbojet or turbofan engines. To optimize variable cycle engine configurations, higher fidelity sensor measurements must be made of the engine operation. The application and use of sensing probes within the hot gas-path environment of the turbine(s) would be highly desirable, and measurements made by such sensing probes could be used to optimally adjust engine parameters for the given speed or determining turbine integrity through active monitoring of airfoil temperatures. 
         [0008]    Unfortunately, the maximum operating temperature of currently available sensors are hundreds to thousands of degrees lower than the combustion gas temperatures. 
       SUMMARY 
       [0009]    In one aspect, a sensor assembly is disclosed. The sensor assembly may include an elongated housing that may include a proximal end and a distal end portion with a housing body disposed between the proximal end and the distal end portion. The proximal end of the housing may include an opening for accommodating the sensor. The sensor may extend through the housing body to the distal end portion of the housing. The distal end portion of the housing may include a port that extends generally radially through a trailing side of the distal end portion. The distal end portion may also include a leading side disposed diametrically opposite the port and the trailing side of the distal end portion. The leading side of the distal end portion may curve towards and terminate at the trailing side of the distal end portion and distally of the port to provide a contoured distal end to the elongated housing that faces the combustion gas flow. 
         [0010]    In another aspect, a sensor assembly for a turbine of a gas turbine engine is disclosed. The sensor assembly may include an elongated housing that may include a proximal end and a distal end portion. A housing body may be disposed between the proximal end and the distal end portion. The proximal end of the housing may include an opening for accommodating a sensor. The sensor may be axially received through the housing body to the distal end portion of the housing. The elongated housing may include a leading side for engaging combustion gas flow and a trailing side that faces away from the combustion gas flow. The distal end portion of the housing may include a port that extends generally radially through the trailing side at the distal end portion so the port faces away from the combustion gas flow. The leading side of the housing at the distal end portion curves towards and terminates at the trailing side at the distal end portion and distally of the port. The leading side of the housing of the distal end portion may be convex for minimizing the heat transfer coefficient and to minimize the probability of hot combustion gases entering the port and damaging the sensor. The housing body may also include a continuous sidewall with a leading plenum extending through the sidewall along the leading side of the housing and between the proximal end and distal end portion of the housing. The continuous sidewall may further include a trailing plenum extending through the sidewall and along the trailing side of the housing between the proximal end of the housing and the port. Cooling air may be flowed through the leading and trailing plenums. 
         [0011]    In another aspect, a method for measuring a temperature of combustion gases flowing through a turbine of a gas turbine engine is disclosed. The turbine is disposed within an engine case. The method may include coupling a proximal end of a temperature sensor assembly to the engine case at an upstream portion of the turbine. For example, the probe may be disposed within the stator vanes disposed upstream of the first stage rotor blades. A distal end of the temperature sensor assembly may be directed radially inwards from the engine case and into a flow path of combustion gases. The temperature sensor assembly may include an elongated housing that accommodates a sensor. The elongated housing may include a distal end portion. The method may further include sensing combustion gas temperatures through a port disposed in the distal end portion. The port may face away from the flow of combustion gases. The method may further include providing leading and trailing plenums in the housing wherein the leading plenum is disposed in a leading side of the housing that faces the flow of combustion gases and wherein the trailing plenum is disposed in a trailing side of the housing that, like the port, faces away from the flow of combustion gases. The leading plenum may provide communication between a cooling air source and film cooling holes disposed in the distal end portion of the housing. The trailing cooling plenum may provide communication between the cooling air source and the port. The method may further include flowing cooling air through the leading and trailing plenums. 
         [0012]    In any one or more of the embodiments described above, the leading side of the distal end portion of the housing may be convex. 
         [0013]    In any one or more of the embodiments described above, the sensor may include a proximal end and a distal end that at least partially overlaps the port. 
         [0014]    In any one or more of the embodiments described above, the housing body may include a continuous sidewall with a leading plenum extending through the sidewall and between the proximal end and distal end portion of the housing. The leading plenum may be disposed generally diametrically opposite the port. 
         [0015]    In any one or more of the embodiments described above, the leading plenum may in communication with a plurality of film cooling holes disposed in the leading side of the distal end portion of the housing. 
         [0016]    In any one or more of the embodiments described above, the housing may further include a trailing plenum disposed in the trailing side of the housing and generally diametrically opposite from the leading plenum and extending through the sidewall between the proximal end of the housing and the port. 
         [0017]    In any one or more of the embodiments described above, the leading and trailing plenums are in communication with a source of cooling air. 
         [0018]    In any one or more of the embodiments described above, the housing body may include at least one side cavity disposed between the sidewall and the sensor. The at least one side cavity may be disposed between the leading and trailing plenums. 
         [0019]    In any one or more of the embodiments described above, the housing body may include two side cavities disposed between the sidewall and the sensor. The two side cavities are disposed generally diametrically opposite from each other and each side cavity may be disposed between the leading and trailing plenums. 
         [0020]    In any one or more of the embodiments described above, at least one of the side cavities is in communication with a source of cooling air. In a further refinement, where two side cavities are present, both side cavities may be in communication with the source of cooling air. 
         [0021]    In any one or more of the embodiments described above, the housing may be coated with a thermal barrier coating. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0022]      FIG. 1  is a partial perspective view of an engine case that surrounds a turbine, the upstream or first row of stator vanes of the turbine, a bracket for coupling a sensor assembly to the engine case and a cooling air supply that may be delivered to a sensor. 
           [0023]      FIG. 2  is a partial rear perspective view illustrating a row of turbine blades and the spatial relationship between the sensor shown in  FIG. 1  and the turbine blades, which are not shown in  FIG. 1 . 
           [0024]      FIG. 3  is a plan view of the sensor assembly shown in  FIGS. 1-2 . 
           [0025]      FIG. 4  is a side plan view of the sensor assembly shown in  FIGS. 1-3 . 
           [0026]      FIG. 5  is a sectional view taken substantially along line  5 - 5  of  FIG. 4 . 
           [0027]      FIG. 6  is another plan view of the sensor assembly shown in  FIGS. 1-5 . 
           [0028]      FIG. 7  is a sectional view taken substantially along line  7 - 7  of  FIG. 3 . 
       
    
    
     DESCRIPTION 
       [0029]      FIG. 1  shows a partial view of an engine case  10  that encircles a turbine, only parts of which are shown in  FIGS. 1-2 . In  FIG. 1 , a partial view of the upstream row of stator vane  11  is illustrated as coupled to an interior of the engine case  10 .  FIG. 1  also illustrates a bracket  12  that may include four legs, three of which are shown at  13 ,  14 ,  15  that connect the protective plate  16  to the engine case  10 . The plate  16  may include an opening  17  through which a proximal end of a sensor assembly  20  ( FIG. 2 ) protrudes. The distal end portion  21  of the sensor assembly  20  can be seen in  FIG. 1 . The sensor assembly  20 , as shown in  FIGS. 1-2  may also be connected to a conduit  22  which provides communication between the sensor assembly  20  and a cooling air supply as will be discussed below. 
         [0030]      FIG. 2  shows a general spatial relationship between the disclosed sensor assembly  20  and the rotor blades  23  of the first stage of the turbine. The development of highly durable cooled sensor assemblies  20  make possible the effective measurement of engine cycle parameters within the power turbines which may lead to new control paradigms that may incorporate measurements made by such sensor assemblies  20  to optimally adjust engine parameters for a given speed or determining the health or the extent of wear of the turbine blades  23 . The condition of the turbine blades  23  may be determined or estimated by measuring airfoil temperatures. However, to accommodate sensors in a turbine area of a gas turbine engine, cooling is required because the maximum operating temperatures of such sensors is typically hundreds to thousands of degrees lower than the temperature of the combustion gas flow, which is indicated schematically by arrow  24  in  FIG. 1 .  FIG. 2  illustrates a different orientation but the direction of the combustion gas flow is also indicated by the arrow  24  in  FIG. 2 . The reader will note that the contoured distal end portion  21  of the sensor assembly  20  faces the combustion gas flow while a port  25  disposed in the sensor housing  26  faces away from the combustion gas flow as indicated by the arrow  24 . Finally, still referring to  FIG. 2 , it will be noted that the rotor blades  23  are coupled to platforms  27  which, in turn, connect the rotor blades  23  to roots  28  which provide a dovetail connection to an inner case structure (not shown). 
         [0031]    Turning to  FIGS. 3-4 , a sensor assembly  20  that may include a housing  26  that may include a proximal end  31 , a distal portion  21  and a housing body  33  disposed therebetween. The proximal end  31  may include an opening for receiving a sensor module or sensor  34 . While the proximal end  35  of the sensor  34  is prominently shown in  FIG. 3 , the sensor  34  also includes a distal end  36  that may be seen through the port  37  that extends radially through the distal end portion  32  of the housing  26 . The housing body  33  may be cylindrical for aerodynamic purposes. Further, the distal end portion  21  of the housing  26  may be specially designed to include a convex surface  38  that faces the combustion gas flow indicated by the arrow  24 . 
         [0032]    The convex surface  38  in the general contoured configuration of the leading side of the distal end portion  21  of the housing  26  minimizes the heat transfer coefficient by minimizing boundary layer tripping or interrupted boundary layers that may be associated with sharp edges. Hence, the distal end portion  21  of the housing  26  is contoured and has a curved profile from the leading side of the housing  26  that faces the arrow  24  as shown in  FIG. 4  to the trailing side of the housing  26  that faces away from the combustion gas flow as indicated by the arrow  24 . Due to the cylindrical nature of the housing body  33 , the leading and trailing sides of the housing body  33  and the distal end portion  21  of the housing  26  do not include reference numerals. However, for purposes of clarity, it will be noted that the port  37  faces away from the combustion gas flow as indicated by the arrow  24  and therefore is disposed on the trailing side of the distal end portion  21  of the housing  26 . The convex surface  38  as shown in  FIG. 4  and FIG.  5  is disposed generally diametrically opposite the distal end portion  21  of the housing  26  and therefore is in general alignment with the leading side of the housing  26  and distal end portion  21 . This will be further clarified below in connection with the description of  FIGS. 5 and 7 . Further, in addition to minimizing boundary layer tripping or boundary layer interruptions, the convex surface  38  that faces the combustion gas flow as indicated by the arrow  24  also reduces the possibility of hot combustion gases from entering the port  37  which may be caused by unsteady blade passing interactions with local recirculation zones created by flow separations around the sensor assembly  20 . 
         [0033]    Turning to  FIG. 5 , the maximum operating temperature of a typical sensor  34  may be hundreds to thousands of degrees lower than the temperature of the combustion gas flow (see the arrow  24 ). Therefore, to accommodate the sensor  34 , the housing  26  has been designed with a cooling system. Part of that cooling system is shown in  FIG. 5  in the form of a leading plenum  41  and a trailing plenum  42 . The leading plenum  41  is disposed along the leading side of the housing  26  that faces the combustion gas flow (see the arrow  24 ). In contrast, the trailing plenum  42  is in general alignment with the port  37 . Both the leading plenum  41  and trailing plenum  42  may be in communication with the cooling air conduit  22 . The leading plenum  41  may provide communication between the cooling air conduit  22  and the film cooling holes shown schematically at  44  in  FIG. 6 . The film cooling holes  44  may be disposed in the convex surface  38  of the distal end portion  21  of the housing  26 . Thus, air travels from the air supply, through the conduit  22 , through the leading plenum  41  and out through the film cooling holes  44 . 
         [0034]    Film cooling may be used to bleed air from the compressor stage and route at least some of that air through the conduit  22 , through the plenum  41  and out through the film cooling holes  44 . As a result, a thin, cool insulating blanket will flow along the convex surface  38  and past the port  37 . Further, the trailing plenum  42  provides communication between the conduit  22  and the port  37 . Because the trailing plenum  42  has a higher through flow, cooling air passing through the trailing plenum  42  and out through the port  37  provides a film of air to both cool and shield the distal end  36  of the sensor  34  (see  FIG. 5 ) from the hot combustion gases and particulates carried in the combustion gas flow indicated by the arrow  24 . 
         [0035]    Turning to  FIG. 7 , a sectional view of the sensor assembly  20  is shown. The housing body  33  includes a continuous sidewall  45  through which the leading plenum  41  and trailing plenum  42  extend. Further, a pair of side cavities  47 ,  48  are disposed in the sidewall  45  and defined by the sidewall  45  and the sensor  34 . The side cavities  47 ,  48  may also be in communication with the cooling air duct  22  provide slower velocity cooling to the lower heat-load portions of the sensor  34 . 
         [0036]    Thus, cooling air may be used by the sensor assembly  20  in a variety of ways including a cooling air flow through the leading plenum  41  and out through the film cooling holes  44 . The placement and number of film cooling holes  44  may be optimized to tailor the sensor assembly  20  to its intended operating environment. Optimizing the number of film cooling holes  44  may result in effective cooling of the sensor  34  while minimizing possible corruption of the measurements made by the sensor  34  by extraneous amounts of cooling air in the flow path indicated by the arrow  24 . Further, larger quantities of cooling air may be flowed through the trailing plenum  42  and out through the port  37  that faces away from the combustion gas air flow (see the arrow  24 ) which, by virtue of its higher through flow, provide a film of air to both cool and shield the distal end  36  of the sensor  34 . Finally, additional cooling may be provided by air flowing into and out of the cavities  47 ,  48 . The cavities  47 ,  48  do not have an exit port or film hole associated with them. However, small exit ports or film cooling holes could be utilized for the cavities  47 ,  48  as well. 
       INDUSTRIAL APPLICABILITY 
       [0037]    Disclosed herein is a sensor assembly equipped with a housing having a cooling system that protects the enclosed sensor from the extremely harsh looking environment of a gas turbine engine, particularly downstream of the combustor. The aerodynamic contouring of the distal end portion which provides a convex surface for engaging the combustion gas flow minimizes heat loading to the sensor housing. Further, the aerodynamic contouring of the distal end portion of the housing minimizes the possibility of combustion gases entering the port that faces away from the combustion gas flow and through which the distal end of the sensor detects operating temperatures via infrared technology. IR temperature sensors are known to those skilled in the art. 
         [0038]    The housing is equipped with a leading cooling plenum disposed on a side of the housing that faces the combustion gas flow as well as a trailing cooling plenum that faces away from the combustion gas flow. The leading cooling plenum provides highly effective impingement cooling to the leading side of the sensor housing and therefore the portion of the sensor housing with the highest heat load location. The trailing cooling plenum provides an aerodynamic heat shield and a film of cooling air to protect the distal end of the sensor from combustion gas path temperatures and particulates. The additional side cavities that are disposed diametrically opposite the housing from one another and each of which are disposed between the leading and trailing plenums, provide active cooling to the sensor and housing and minimize any heat conduction path to the sensor. 
         [0039]    The use of film holes on the distal end portion as an outlet for the leading plenum cooling airflow may be optimized to minimize measurement air from the cooling airflow. Finally, the housing may be coated with a thermal barrier coating. The thermal barrier coating may include three layers, not including the housing which serves as a metal substrate. The three additional layers include a metallic bond coat, a thermally grown oxide and a ceramic top coat, as will be apparent to those skilled in the art. The thermal barrier coating may be applied using conventional technology such as electron beam physical vapor deposition (EBPVD), air plasma spray (SPS), high velocity oxygen fuel (HVOF), electrostatic spray assisted vapor deposition (ESAVD) and/or direct vapor deposition. The ceramic top coat may be a yttria-stabilized zirconia (YSZ), or other suitable materials as will be apparent to those skilled in the art.