Abstract:
This invention relates to an internal combustion engine having a cavity for inspection, comprising: an inspection device mounted within a housing, the housing at least partially located within the cavity to be inspected and having a shutter which is actuable between a closed configuration and an open configuration; and an actuation mechanism for moving the shutter between the closed configuration and the open configuration.

Description:
TECHNICAL FIELD OF INVENTION 
       [0001]    This invention relates to an inspection device for an internal combustion engine. 
       BACKGROUND OF INVENTION 
       [0002]      FIG. 1  shows a ducted fan gas turbine engine  10  comprising, in axial flow series: an air intake  12 , a propulsive fan  14  having a plurality of fan blades  16 , an intermediate pressure compressor  18 , a high-pressure compressor  20 , a combustor  22 , a high-pressure turbine  24 , an intermediate pressure turbine  26 , a low-pressure turbine  28  and a core exhaust nozzle  30 . A nacelle  32  generally surrounds the engine  10  and defines the intake  12 , a bypass duct  34  and a bypass exhaust nozzle  36 . 
         [0003]    Air entering the intake  12  is accelerated by the fan  14  to produce a bypass flow and a core flow. The bypass flow travels down the bypass duct  34  and exits the bypass exhaust nozzle  36  to provide the majority of the propulsive thrust produced by the engine  10 . The core flow enters in axial flow series the intermediate pressure compressor  18 , high pressure compressor  20  and the combustor  22 , where fuel is added to the compressed air and the mixture burnt. The hot combustion products expand through and drive the high, intermediate and low-pressure turbines  24 ,  26 ,  28  before being exhausted through the nozzle  30  to provide additional propulsive thrust. The high, intermediate and low-pressure turbines  24 ,  26 ,  28  respectively drive the high and intermediate pressure compressors  20 ,  18  and the fan  14  by interconnecting shafts  38 ,  40 ,  42 . 
         [0004]    It is known in modern gas turbine engines  10  to use a boroscope to inspect the interior of the engine  10  both after assembly and during servicing to detect the fitness of the engine  10 . Thus, engines  10  are known to have inspection ports in various locations to allow boroscopes to be inserted.  FIG. 2  shows such a port  210  for a compressor  18  which includes an outer casing wall  212  and an inner casing wall  214  which house annular arrays of compressor rotor blades  216  and stator vanes  218 . The port  210  includes flanged apertures  220 ,  222  through the inner  214  and outer  212  walls and is shown in a closed configuration in which the apertures  220 ,  222  are sealed with a plug  224 . In this known example, the plug  224  constitutes sealing members  226 ,  228  for the inner and outer wall apertures  220 ,  222  which are linked by a link rod  230 . The plug  224  can be realisably secured within the port  210  in any suitable manner and configured to be removed from the exterior of the compressor  18  when boroscope access is required. As will be appreciated, once removed, a boroscope can be inserted as required. 
         [0005]    Typically, the inspection ports  210  are located around the engine core so that, for example, each stage of the compressor  18  may have a circumferential distribution of inspection ports, as might the combustor or various turbine stages. 
         [0006]    The present invention seeks to provide an improved way of inspecting the interior of an internal combustion engine. 
       Statements of Invention 
       [0007]    In a first aspect, the present invention provide an internal combustion engine having a cavity for inspection, comprising: an inspection device mounted within a housing, the housing at least partially located within the cavity to be inspected and having a shutter which is actuable between a closed configuration and an open configuration; and an actuation mechanism for moving the shutter between the closed configuration and the open configuration. 
         [0008]    Providing an inspection device behind a shutter allows the inspection device to be left in situ and used whenever the engine conditions allow. For example, in the case of a gas turbine engine, the inspection device may be placed within a section of compressor and exposed to view the operation of the compressor during start up or close down periods when the temperature is not excessive. Having an inspection device can provide important information about the operation of the engine and can aid engine health monitoring schemes. 
         [0009]    The inspection device may be configured to allow visual inspection of the cavity. The inspection device may be an optical device. The optical device may comprise a camera. The optical device may be configured to receive infrared spectrum. In an alternative embodiment, the optical device may be a fibre optic cable or other light channelling medium or conduit. The optical device may be coupled to a light sensor which is remote to the inspection device. 
         [0010]    The inspection device may be retractable between a stowed position and an inspection position. 
         [0011]    The shutter may be retractably stowed within the housing when in the closed configuration and actuated into the cavity so as to expose the inspection device when in the open configuration. 
         [0012]    The shutter may be configured to be actuated by the inspection device when the inspection device is moved between the stowed and inspection positions. The shutter may be acutable so as to move laterally across a field of view of the inspection device when moving between the open and closed configurations. The shutter may include a cleaning device for cleaning the inspection device. 
         [0013]    The shutter and inspection device may be simultaneously actuable. The inspection device, actuation mechanism and shutter may comprise a single module which includes one part of a two part mounting system for mounting the device to the engine. The mounting system may be a threaded bore and corresponding boss or flange. 
         [0014]    The actuation mechanism may be one taken from the group including pneumatic, hydraulic or electrical. The actuation mechanism may be linear or rotary. 
         [0015]    The housing may be at least partially formed by a wall of the cavity. The cavity may include moving parts of the internal combustion engine. 
         [0016]    The shutter may include first and second shutter plates. The first and second shutter plates may be symmetrically arranged. The shutter may be cup shaped. The shutter plates may be pivotably mounted. The shutter plates may be biased against a restraining element which retains the shutter plates in place when in the closed position. Upon actuating the shutter from the closed configuration to the open configuration may include moving the shutter plates relative to the restraining element such that the bias results in the inspection device being exposed to the cavity. 
         [0017]    The internal combustion engine may be a gas turbine engine. 
         [0018]    In a second aspect, the present invention provides an aircraft having the internal combustion engine according to the first aspect. 
         [0019]    The actuation mechanism may be operable from the cockpit of an aircraft or as part of an engine health monitoring system. 
     
    
     
       DESCRIPTION OF DRAWINGS 
         [0020]    Embodiments of the invention will now be described with the aid of the following drawings of which: 
           [0021]      FIG. 1  shows a typical gas turbine engine. 
           [0022]      FIG. 2  shows a known arrangement for a boroscope inspection port. 
           [0023]      FIGS. 3   a  and  3   b  show a retractable inspection device in a stowed and inspection position accordingly. 
       
    
    
     DETAILED DESCRIPTION OF INVENTION 
       [0024]      FIG. 3  shows a portion of an internal combustion engine  310  in the form of a compressor wall  312  of a gas turbine engine, similar to the one shown in  FIG. 2 . The wall  312  is adjacent to the gas flow path  314  of the compressor which represents a cavity  316 . As noted above, inspecting such a cavity can be beneficial for determining the condition of the engine, both prior to use and during a service interval. 
         [0025]    The engine  310  includes an inspection device  318  in the form of a camera which is mounted within a housing  320 . In the described embodiment, the housing is in the form of an aperture  322  in the compressor wall  312 . The inspection device  318  is retractably mounted in the housing  320  so as to be movable between a stowed position (as shown in  FIG. 3   a ) where the inspection device  312  is shielded from the environment of the cavity, and an inspection position (as shown in  FIG. 3   b ) in which the inspection device  318  is exposed to the cavity so as to allow inspection. 
         [0026]    The engine  310  also includes a shutter  324  which provides an environmental shield for the inspection device  318  in the stowed position. The shutter  324  is arranged to be actuable between a closed configuration ( FIG. 3   a ) and an open configuration ( FIG. 3   b ). In the described embodiment, the shutter  324  is also retractably mounted within the housing  320  so as to have a stowed position which corresponds to the closed configuration, and an inspection position which corresponds to the open configuration. 
         [0027]    The shutter  324  includes a cup shaped shield  326  having an internal chamber which fits over and receives the inspection device  318  when in the stowed position. The cup shaped shield  326  is inverted within the housing aperture  322  such that a base  326  of the cup faces the gas flow path  314  with the side walls  328  being snugly received within the aperture  322  of the compressor wall  312 , with the inspection device  318  located within the internal chamber of the shutter  324 . In this way, the shutter  324  and housing  320  combine to provide an enclosed protective space for the inspection device  318 , with the base of the shutter  324  shielding the inspection device  318  from the cavity  316 . 
         [0028]    The shutter  324  is made from two shutter plates  326   a,    326   b  which are similar to each other in construction and arranged in a symmetrically opposing manner so as to each provide half of the cup shaped shield  326  when in a closed configuration. Each shutter plate  326   a,    326   b  is pivotably mounted  329  to an actuation mechanism  330  towards a distal end of the shutter  324  relative to the cavity such that, when they are not constrained by the housing  320 , rotating the shutter plates  326   a,    326   b,  about the pivot  329  results in each shutter plate  326   a,    326   b  being moved away from the inspection device  318  to expose it to the cavity  316 . 
         [0029]    As the shutter plates  326   a,    326   b  are symmetrically arranged, they form a pincer or scissor-like arrangement such that the cup-like structure of the shutter  324  pivotably parts along a midline so as to reveal the inspection device  318 . 
         [0030]    As described above, the shutter  324  can be thought of a shield to protect the inspection device  318  from the ambient operating environment which may be beyond the safe operating environment for the inspection device  318 . For example, in the case of a compressor, the in use operating temperature may be several hundred degrees which would damage the inspection device  318 . Thus, in this case, the shutter acts as a thermal shield and may be made from any suitable temperature resistant metal alloy or ceramic as known in the art. 
         [0031]    The inspection device  318  of the embodiment is a camera. The camera may be configured to detect infrared emitted within the compressor but it will be appreciated that other visual and non-visual inspection devices may be advantageously used depending on the application. Having an infrared camera is particularly advantageous as it allows the thermal condition of the engine to be analysed during, for example, a wind down period. This can provide an invaluable insight into the condition of the engine and allow detection of flaws in components. 
         [0032]    In the described embodiment, the camera is arranged to sense visible light and includes a wide angle lens  331  in the form of a 150 degree lens and a plurality of LEDs  333  to illuminate the interior of the cavity to be inspected. 
         [0033]    In another embodiment, the inspection device is in the form of a light channelling medium or conduit such as fibre optic cable or light pipe which terminates at  331  as shown in  FIG. 3   b , in view of the cavity. Such a fibre optic may include the aforementioned wide angle lens. The camera, or sensor which detects the light, is located remote to the cavity. Thus, once exposed to the cavity, the end of the fibre optic  331  collects light from the cavity and channels them to the sensor which detects them. It will be appreciated that the sensor will have some associated electronics to process the signal of the sensed image which may or may not be local to the sensor. In this way, the shielding requirements may be much reduced as sensitive electronic components associated with the sensor and signal processing equipment need not be protected from the environment of the cavity to the same degree. 
         [0034]    As described above, the inspection device  318  is retractable between a stowed position and an inspection position in conjunction with the shutter plates  326   a,    326   b,  ( FIGS. 3   a  and  3   b  respectively). An actuation mechanism  330  is included in the arrangement and is operable to move the inspection device  318  and shutter  324  between the stowed position and the inspection position. 
         [0035]    The actuation mechanism  330  of the described embodiment is a linear actuator  332  which is operable to retract and deploy the inspection device  318  and shutter  324  simultaneously. Thus, the actuation mechanism  330  includes driving mechanism  332  located within a actuation housing  334 . The driving mechanism  332  is linked to the shutter  324  and inspection device  318  via push rods  326  which are operably extended in use after an appropriate driving signal is provided. The type of linear actuator and driving mechanism  332  may be hydraulic, pneumatic or electrical and it will be appreciated that non-linear, e.g. rotary, actuators may also be suitably applied. 
         [0036]    As will be appreciated, the actuation of the shutters  324  can be achieved in multiple ways. In one advantageous embodiment, the shutter plates  326   a,    326   b,  are resiliently biased against a restraining element in the form of the walls of the housing aperture  322  such that pushing the shutter  324  into the cavity  316  results in the lateral movement and associated opening of the shutter plates  326   a,    326   b.  Withdrawing the shutter  324  back into the recess causes the shutter plates  326   a,    326   b  to contact the shoulder  338  of the housing aperture  322  which rotates the plates  326   a,    326   b  about the pivot, thereby closing them. 
         [0037]    The inside surface of the shutter  324  which faces the inspection device  318  lens (or sensor as the case may be) may include a cleaning device  340  which acts to clean the inspection device  318  upon opening of the shutter plates  326   a,    326   b  and the associated lateral movement. In one advantageous embodiment, the cleaning device  340  may be a cloth or bristled structure. 
         [0038]    The inspection device  318  arrangement may be inserted into the housing aperture  322  and secured by any known means. In one embodiment, the inspection device  318  and shutter  324  are threadingly engaged within the compressor wall  320  such that they can be removed for maintenance purposes. In this case, the shutter  324 , inspection device  318  and actuation mechanism  330  are constructed and presented to the engine  310  as a single module. 
         [0039]    Providing an inspection device  318  behind a shutter  324  allows the inspection device  318  to be left in situ and used whenever the engine conditions allow. For example, in the case of a gas turbine engine  10 , the inspection device  318  may be placed within a section of compressor and exposed to view the operation of the compressor during start up or close down periods when the temperature is not excessive, but while it is still hot enough to give off a useful thermal signature. Having an inspection device can provide important information about the operation of the engine and can aid engine health monitoring schemes. Arranging the device to be retractable is particularly advantageous as it allows a broader field of view to be accommodated. 
         [0040]    Thus, in use, upon engine shut down, the actuator mechanism  330  is energised so as to push the device into the gas stream flow path  314  to allow the wide angle lens  331  to view the rotating components as they windmill down to stop. Once the rotation speed is low enough to enable a sufficient video capture rate, the rotations are recorded and logged directly to the EMU (Engine Monitoring Unit). Once the required capture is complete, the actuation mechanism  330  pulls the device back into the aperture  322  and the shutter is closed so as to seal off the gas path. 
         [0041]    Although not shown, the inspection device  318  arrangement also includes a means of removing the data captured by the camera. Hence, the inspection device  318  may be hard wired to the EMU or could be wirelessly connected. 
         [0042]    It will be appreciated that the trigger for energising the actuation mechanism  330  may be automatic or may be provided by an operator. The operator may be local to the engine, for example, a pilot or maintenance staff, or may be a remote monitor such as an engine health monitoring system. 
         [0043]    As will be appreciated, the above described embodiments are illustrative of the broader inventive concept which is defined by the appended claims. As such other variations on the above described embodiments will be possible. 
         [0044]    For example, although the invention is described primarily from a view point of being used on a compressor of a gas turbine engine  10 , it will be appreciated that the invention is applicable to various types of internal combustion engine and may be implemented at various locations around such an engine. For example, in the case of a gas turbine engine, the invention may be utilised in the compressor, combustor, or any other area in which active inspection may be beneficial. Further, there may be annular arrays of the inspection devices  318  around a given compressor stage so as to give a fuller, if not complete, view. 
         [0045]    In other embodiments of the invention, the shutter  324  may include a single plate or an iris like structure. Further, the shutter may not be retractable with the inspection device but may be configured to move laterally with respect to the inspection device and housing aperture. Further still, the inspection device may be suitable type which may provide valuable data, such as a thermocouple, visible light spectrum, or pressure to name a few.