Abstract:
A system for monitoring a rotating component in a fuel-vapor zone includes a housing of the rotating component in contact with the fuel-vapor zone; at least one temperature sensor in contact with an outer surface of the housing, wherein the at least one temperature sensor monitors a temperature of the outer surface of the housing and provides an indication when the temperature exceeds a selected temperature; and a controller connected to the at least one temperature sensor to receive the indication, wherein the controller terminates operation of the rotating component upon receipt of the indication.

Description:
BACKGROUND 
       [0001]    The present invention is related to component monitoring, and in particular to a system and method for providing thermal protection for rotating components in fuel-vapor zones. 
         [0002]    Rotating aircraft components, such as those in motor driven compressors, are susceptible to high surface temperatures at the component housings during certain failure modes of the rotating components. The surfaces of these housings may be located within fuel-vapor zones. The surface temperatures in contact with fuel-vapors must remain below an ignition threshold so as to avoid ignition of the vapors. This requires that during normal operation, and during any failure modes, component surface temperatures remain below the ignition threshold. 
         [0003]    Some failure modes in rotating engine components, such as failures at bearing rub surfaces in a motor driven compressor, may generate temperatures beyond those allowed by FAA and aircraft guidelines. These failures can initiate at internal points within the rotating components where protection devices cannot be installed, or signals cannot be read externally. Therefore, it is desirable to provide a system for detecting these internal failures so that failure modes may be handled prior to component surface temperatures reaching an ignition threshold within fuel-vapor zones. 
       SUMMARY 
       [0004]    A system for monitoring a rotating component in a fuel-vapor zone includes a housing of the rotating component, at least one temperature sensor, and a controller. The housing is in contact with the fuel-vapor zone. The at least one temperature sensor that is in contact with an outer surface of the housing monitors a temperature of the outer surface of the housing and provides an indication when the temperature exceeds a selected temperature. The controller is connected to the at least one temperature sensor to receive the indication of excess temperature, and terminates operation of the rotating component upon receipt of the indication. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]      FIG. 1  is a block diagram illustrating a system for monitoring a rotating aircraft component according to an embodiment of the present invention. 
           [0006]      FIG. 2  is a schematic diagram of a motor driven compressor (MDC) according to an embodiment of the present invention. 
           [0007]      FIG. 3  is a schematic diagram of a modeled component housing for an MDC according to an embodiment of the present invention. 
           [0008]      FIG. 4  is a schematic diagram of a housing for an MDC showing a location of attached temperature sensors according to an embodiment of the present invention. 
           [0009]      FIG. 5  is a schematic diagram of a temperature sensor bonded to a component housing according to an embodiment of the present invention. 
           [0010]      FIG. 6  is a flowchart illustrating a method of determining a location for at least one sensor on the surface of a component according to an embodiment of the present invention. 
           [0011]      FIG. 7  is a flowchart illustrating a method of monitoring a surface temperature of a rotating aircraft component according to an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0012]    The present invention describes a system and method for providing thermal protection for rotating components in fuel-vapor zones. A thermal path is analytically determined from an initiation site of a failure to the surface of a housing of the rotating component using a housing model. Optimum locations for thermal sensors on the surface of the component are determined by performing a thermal analysis on the housing model. The sensors are bonded to the surface of the component at the optimum locations and monitor the surface temperature of the component during normal system operation. If the surface temperature reaches a selected temperature, the sensors provide an indication to a controller. Action may then be taken, such as the controller terminating operation of the rotating component. 
         [0013]      FIG. 1  is a block diagram illustrating a system  10  for monitoring a rotating component  12  of an aircraft within a fuel-vapor zone  14 . Rotating component  12  is any component of an aircraft with rotating components, such as a motor driven compressor (MDC). Sensors  16  are connected to a housing surface of component  12  to monitor the surface temperature of component  12 . Sensors  16  are any sensors capable of measuring a temperature, such as thermal switches, thermocouples, resistive temperature devices (RTDs), or any other known devices. Sensors  16  are connected to communicate with controller  18  and indicate to controller  18  when the surface temperature of component  12  reaches a selected temperature, such as approximately 435° F. The selected temperature is typically lower than the ignition limit of the vapors in fuel-vapor zone  14 . In one non-limiting embodiment, the communication between sensors  16  and controller  18  may be accomplished using a wired connection. In other embodiments, sensors  16  may communicate with controller  18  wirelessly using, for example, radio-frequency (RF) transceivers or any other devices capable of wireless communication. Once sensors  16  indicate the surface temperature has reached the selected temperature, controller  18  shuts down rotating component  12  through shutoff module  20 . Shutoff module  20  may be part of engine controller  18 , or may be a separate mechanical component. The selected temperature is selected to allow enough time for rotating component  12  to be shut down such that the surface temperature of component  12  never reaches an ignition threshold that would cause ignition of the vapors within fuel-vapor zone  14 . Controller  18  is any electronic controller of a rotating aircraft component, such as an electric motor control. The number of sensors  16  included in the system  10  may be determined, for example, using safety level requirements combined with a failure rate of a single sensor  16 . 
         [0014]      FIG. 2  is a schematic diagram of MDC  30  according to an embodiment of the present invention. MDC  30  includes tie rod  32 , motor shafts  34   a  and  34   b,  stator winding  36 , rotor compressor stages  38   a  and  38   b,  thrust runner  40 , housing  42 , journal bearings  44   a  and  44   b,  and thrust bearings  46   a  and  46   b.  In one non-limiting embodiment, stator winding  36  drives compressor stages  38   a  and  38   b.  In other embodiments, the rotating component may be driven by any rotating machine, such as a turbine. Motor shafts  34   a  and  34   b  rotate on journal bearings  44   a  and  44   b.  Thrust runner  40  is utilized to prevent axial movement of the rotating components of MDC  30 . Thrust bearings  46   a  and  46   b  prevent contact between thrust runner  40  and housing  42 . Failure modes can occur, for example, due to failures of any of bearings  44   a,    44   b,    46   a  and  46   b.  When a failure occurs at thrust bearing  46   b,  for example, heat is generated due to contact between thrust runner  40  and housing  42 . This heat is conducted to the surface of housing  42  which can create temperatures above normal operating temperatures. 
         [0015]      FIG. 3  is a schematic diagram of modeled component housing  60  according to an embodiment of the present invention. Modeled component housing  60  is a thermal model that corresponds to housing  42  of MDC  30  ( FIG. 2 ). Modeled component housing  60  is generated using a housing model, such as a finite element model (FEM). Thermal analysis using, for example, computational fluid dynamics (CFD) is performed on the FEM to generate modeled component housing  60 . Modeled component housing  60  includes thermal indicators  62  that indicate the sections of modeled component housing  60  that heat up to the greatest temperatures over the shortest period of time. Thermal indicators  62  are utilized to obtain the ideal locations to place temperature sensors. 
         [0016]      FIG. 4  is a schematic diagram of housing  42  showing locations of temperature sensors  70  according to an embodiment of the present invention. Temperature sensors  70  are placed on housing  42  based upon the temperature profile obtained using modeled component housing  60  ( FIG. 3 ). Sensors  70  are any thermal sensors capable of measuring a surface temperature of housing  42  such as thermal switches, thermocouples, resistive temperature devices (RTDs), or any other known devices. In one non-limiting example, if using thermal switches, sensors  70  remain closed during normal system operation. If the temperature of housing  42  reaches a selected temperature, sensors  70  open, indicating to controller  18  ( FIG. 1 ) that MDC  30  ( FIG. 2 ) should be shut down. 
         [0017]      FIG. 5  is a schematic diagram illustrating one of the plurality of temperature sensors  70  bonded to component housing  42  according to an embodiment of the present invention. Flat  80  is machined on housing  42  to accommodate sensor  70 . Wire  82  connects sensor  70  with controller  18  ( FIG. 1 ). To avoid chafing, wire  82  may be encapsulated in wire wrap  84 . In one embodiment, sensor  70  is bonded to flat  80  using any known suitable bonding agent. However, other suitable ways may be utilized to connect sensor  70  to flat  80  without departing from the scope of the invention. 
         [0018]      FIG. 6  is a flowchart illustrating method  100  of determining a location of sensors  70  on the surface of a component according to an embodiment of the present invention. At step  102 , failure initiation sites are determined using a housing model, known failure sites, or other known method of determining initiation sites for failure modes. At step  104 , a housing model, such as a finite element model, is used to determine a thermal path from the initiation sites to a surface of the component. At step  106 , thermal analysis is performed on the housing model to determine locations on the surface of the component that reach the greatest temperatures over the shortest period of time using, for example, computational fluid dynamics. At step  108 , thermal sensors are attached to these locations for use during normal system operation. 
         [0019]      FIG. 7  is a flowchart illustrating method  120  of monitoring a surface temperature of a component of an engine according to an embodiment of the present invention. At step  122 , sensors  70  monitor the temperature of component housing  42 . At step  124 , it is determined if the temperature measured at step  122  is greater than a selected temperature. This selected temperature is selected to allow enough time for the component to be shut down so that the surface temperature of the component never reaches an ignition threshold that would cause ignition of the vapors within a fuel-vapor zone. If the temperature is greater than the predefined temperature, method  120  proceeds to step  126 . If the temperature is less than the predefined temperature, method  120  returns to step  122 . At step  126 , sensors  70  indicate that the surface temperature is greater than the predefined temperature to controller  18 . At step  128 , controller  18  shuts down the component. 
         [0020]    In this way, the present invention describes a system and method for determining a thermal path for detection of failure modes in gas turbine engine components. Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.