Torque probe cooling for gas turbine engine using internal fluid flow

Reference is made to US patent application entitled “TORQUE PROBE COOLING FOR GAS TURBINE ENGINE USING EXTERNAL AIR” and filed on Feb. 2, 2021, the entirety of which is incorporated by reference herein, and whose application number will be indicated here when known.

The application relates generally to gas turbine engines and, more particularly, to gas turbine engines with torque measuring probes.

On some gas turbine engines, such as turboprop or turboshaft engines, the output torque of the engine is measured with a torque probe which uses a torque meter. In some engine architectures, it may be necessary to install the torque probe in a hot section of the engine. The elevated temperature in the hot section caused by the hardware surrounding the torque probe may have an impact on the electronic components of the torque probe.

There is disclosed a gas turbine engine, comprising: an exhaust case enclosing an exhaust duct and a bearing housing, the bearing housing defining a bearing cavity and enclosing bearings mounted to a shaft; a torque probe extending inwardly into the exhaust case along a torque probe axis and positioned adjacent to the exhaust duct, the torque probe configured to determine a torque on the shaft; a sleeve enclosing at least part of the torque probe, the sleeve defining a flow passage between an inner surface of the sleeve and an outer surface of the torque probe, the flow passage being in fluid communication with a flow passage inlet of the sleeve and with a flow passage outlet of the sleeve, the flow passage inlet in fluid communication with the bearing cavity to receive a cooling fluid therefrom; and a vent extending between a vent inlet in fluid communication with the flow passage outlet and a vent outlet positioned outside the exhaust case; wherein during operation of the gas turbine engine, the cooling fluid flows from the bearing cavity, into the flow passage along the outer surface of the torque probe to cool the torque probe, and into the vent to be discharged via the vent outlet.

There is disclosed a method for cooling a torque probe disposed adjacent to an exhaust duct within an exhaust case of a gas turbine engine, the method comprising: forming a fluid flow path from a bearing cavity of the gas turbine engine to an outlet positioned outside of the exhaust case; and positioning the torque probe within the fluid flow path downstream of the bearing cavity and upstream of the outlet, a cooling fluid flowing from the bearing cavity, along the torque probe to cool the torque probe, and to the outlet when the gas turbine engine is operating.

There is disclosed a torque probe heat shield mountable about an outer surface of a torque probe, the torque probe heat shield comprising: an elongated sleeve extending along a sleeve axis between a first sleeve end and a second sleeve end, the sleeve mountable about the torque probe to define a flow passage between an inner surface of the sleeve and an outer surface of the torque probe, the flow passage being in fluid communication with a flow passage inlet of the sleeve and with a flow passage outlet of the sleeve spaced apart along the sleeve axis from the flow passage inlet, a cooling fluid configured to flow into the flow passage via the flow passage inlet, through the flow passage along the outer surface of the torque probe to cool the torque probe, and out of the flow passage via the flow passage outlet.

Reference is now made to the accompanying figures in which:

FIG. 1 is a schematic cross-sectional view of a gas turbine engine;

FIG. 2 is an enlarged cross-sectional view of the region II-II in FIG. 1 showing a torque probe;

FIG. 3 is a perspective view of a sleeve mountable about the torque probe of FIG. 2 ;

FIG. 4 is a perspective view of part of an outer surface of an exhaust case of the gas turbine engine of FIG. 1 ; and

FIG. 5 is an enlarged cross-sectional view of part of the gas turbine engine of FIG. 1 showing another configuration of the torque probe.

FIG. 1 illustrates a gas turbine engine 10 of a type preferably provided for use in subsonic flight, generally comprising in serial flow communication a compressor section 14 for pressurizing the air, a combustor 16 in which the compressed air is mixed with fuel and ignited for generating an annular stream of hot combustion gases, and a turbine section 18 for extracting energy from the combustion gases. The gas turbine engine 10 extends along a longitudinal center axis 11 about which many of its components rotate. In FIG. 1 , the turbine section 18 drives a propeller 12 mounted at an end of the gas turbine engine 10 opposite to an air inlet 13 .

The internal components of the gas turbine engine 10 (sometimes referred to herein simply as the “engine 10 ”) are housed in a casing 15 . The casing 15 is an annular body defining an interior of the engine 10 which houses the turbomachinery and other components of the engine 10 . Referring to FIG. 1 , the casing 15 is made up of multiple casing segments, or cases, which are axially adjacent each other and connected to one another. In the configuration of the engine 10 shown in FIG. 1 , one the casing segments is an exhaust case 15 A. The exhaust case 15 A is an annular body that defines an interior volume in which one or more exhaust ducts 17 and other components are housed. Each exhaust duct 17 defines a flow path from the exit of the turbine section 18 to convey the combustion gases out of the casing 15 and away from the engine 10 via an exhaust outlet 17 A. The exhaust duct 17 has an interior surface 17 B which faces the hot combustion gases, and an exterior surface 17 C which faces inwardly toward the volume defined by the exhaust case 15 A. During operation of the engine 10 , when hot combustion gases are flowing through the exhaust duct 17 , the interior and exterior surfaces 17 B, 17 C heat up such that they radiate heat into the exhaust case 15 A, and also provide convection heat transfer to the exhaust case 15 A by heating the air therein with the exhaust duct 17 . The casing 15 also includes the following cases: a reduction gearbox case 15 B which houses a reduction gearbox 31 , a hot section case 15 C which houses the turbine section 18 , a cold section case 15 D which houses the compressor section 14 , and an accessory gearbox case 15 E which houses the accessory gearbox 50 . Referring to FIG. 1 , the exhaust case 15 A is mounted to the reduction gearbox case 15 B at one axial end of the exhaust case 15 A, and is mounted to the hot section case 15 C at the other axial end of the exhaust case 15 A. The cases may be mounted to each other with mating radially-outer flanges that are bolted together. The cases may be made of metal of any suitable alloy. The casing 15 may have more or fewer cases than the ones shown in FIG. 1 , and the cases may be arranged differently than as shown.

Referring to FIG. 1 , the engine 10 has a nacelle 19 . The nacelle 19 is an annular body, made up of one or more segments, which surrounds the casing 15 and one or more of its cases. The nacelle 19 has an outer surface 19 A which forms part of the visible exterior of the engine, and an inner surface 19 B which faces toward the casing 15 . Referring to FIG. 1 , the nacelle 19 surrounds and encloses at least the exhaust case 15 A and the reduction gearbox case 15 B. The inner surface 19 B of the nacelle 19 A is spaced apart from surfaces of parts of casing 15 , such as from the surfaces of the exhaust case 15 A and the reduction gearbox case 15 B as shown in FIG. 1 , in a direction parallel to a radial line from the center axis 11 of the engine 10 . A nacelle flow passage 19 C is thus defined in this radial or annular space between the inner surface 19 B of the nacelle 19 A and these surfaces of the cases 15 A, 15 B. Ambient air from outside the engine circulates through, or is present within, the nacelle flow passage 19 C.

Referring to FIG. 1 , the reduction gearbox 31 (sometimes referred to herein simply as the “RGB 31 ”) of engine 10 is drivingly engaged to an output shaft 18 A driven by the turbine section 18 . In FIG. 1 , the RGB 31 is disposed axially between the turbine section 18 and the propeller 12 . The output shaft 18 A of the engine 10 is thus drivingly connected to the propeller 12 via the RGB 31 . The RGB 31 processes and outputs the rotational drive transferred thereto from the turbine section 18 via the output shaft 18 A through known gear reduction techniques. The RGB 31 allows for the propeller 12 to be driven at its optimal rotational speed, which may be different from the rotational speed of the turbine section 18 .

Referring to FIG. 1 , the accessory gearbox 50 (sometimes referred to herein simply as the “AGB 50 ”) the engine 10 receives a rotational output and in turn drives accessories (e.g. fuel pump, starter-generator, oil pump, scavenge pump, etc.) that contribute to the functionality of the engine 10 . The AGB 50 can be designed with side-facing accessories, top-facing accessories, or rear-facing accessories depending on the installation needs. The AGB 50 is positioned at an end of the engine 10 that is axially opposite to the end of the engine 10 at which the RGB 31 is located. The AGB 50 is aft of the air inlet 13 . The AGB 50 is housed within the accessory gearbox case 15 E, but it may also be free of a case. The AGB 50 is outside of the exhaust case 15 A. In an alternate possible embodiment the engine 10 , the engine 10 is free of an AGB 50 . The AGB 50 can be arranged relative to the casing 15 of the engine 10 differently than as shown in FIG. 1 . For example, the AGB 50 may be mounted on the side of the engine 10 , and forward of the air inlet 13 . The circumferential angular position of the AGB 50 may be selected to suit specific installation needs. Other positions and arrangements for the AGB 50 are thus possible.

Referring to FIG. 1 , the engine 10 is a “reverse-flow” engine 10 because gases flow through its components from the air inlet 13 at a rear or aft portion of the engine 10 , to the exhaust outlet 17 A at a front portion of the engine 10 . This is in contrast to “through-flow” gas turbine engines in which gases flow through the core of the engine from a front portion to a rear portion. The direction of the flow of gases through the engine 10 is shown in FIG. 1 with arrows F. The direction of the flow of gases F through the engine 10 can be better appreciated by considering that the gases flow through the engine 10 in the same direction D as the one along which the engine 10 travels during forward flight. Stated differently, gases flow through the engine 10 from a rear end adjacent the AGB 50 towards a front end adjacent the propeller 12 . In an alternate embodiment, the engine 10 is a through-flow engine 10 . Referring to FIG. 1 , the engine 10 is a reverse-flow turboprop engine 10 . The engine 10 may be another type of gas turbine engine, for example, a turbofan and a turbojet.

It will thus be appreciated that the expressions “forward” and “aft” used herein may refer to the relative disposition of components of the engine 10 , in correspondence to the “forward” and “aft” directions of the engine 10 and aircraft including the engine 10 as defined with respect to the direction of travel D. In the embodiment shown, a component of the engine 10 that is “forward” of another component is arranged within the engine 10 such that it is located closer to the propeller 12 . Similarly, a component of the engine 10 that is “aft” of another component is arranged within the engine 10 such that it is further away from the propeller 12 .

Referring to FIG. 1 , the engine 10 includes a bearing housing 40 disposed within, and housed by, the exhaust case 15 A. The bearing housing 40 is an annular body defining an internal bearing cavity 42 in which one or bearings 44 are located. The bearings 44 engage and support the output shaft 18 A and its rotation about the center axis 11 of the engine 10 . The bearing housing 40 and the bearing cavity 42 are sealed off from a remainder of the internal volume of the exhaust case 15 A to prevent oil or an oil mist from escaping the bearing cavity 42 and entering the hot zone within the exhaust case 15 A adjacent to the exhaust duct 17 . The pressure within the bearing housing 40 , or the pressure of the bearing cavity 42 , may thus be different than a pressure within the remainder of the exhaust case 15 A. The engine 10 may also have other bearing housings 40 to enclose other bearings 44 of the engine 10 which support other shafts or different portions of the output shaft 18 A. These additional bearing housings 40 may be enclosed by other cases of the casing 15 .

Referring to FIG. 1 , the engine 10 has a torque probe 20 configured to measure a torque of a shaft of the engine 10 . The torque probe 20 may house or include electronic components, such as a torque meter or a phase shift torque meter, to measure the torque on, or generated by, the output shaft 18 A. The torque probe 20 is an elongated body extending along a torque probe axis 21 (see FIG. 2 ) from a first end inwardly into the exhaust case 15 A to a second end that measures the torque of the output shaft 18 A. Most of the torque probe 20 , including the second end, is disposed within the exhaust case 15 A. More particularly, the second end and some of the length of the torque probe 20 defined along the torque probe axis 21 is positioned within the bearing cavity 42 . A portion of the torque probe 20 , such as the first end, is located outside of the exhaust case 15 A within the nacelle flow passage 19 C. The torque probe 20 extends inwardly into the exhaust case 15 A through an opening in the exhaust case 15 A, which is described in greater detail below. The torque probe 20 may not be mounted directly to the exhaust case 15 A, and may instead be positioned relative to the exhaust case 15 A to displace with respect to the exhaust case 15 A, as described in greater detail below. The torque probe axis 21 is straight. Referring to FIG. 2 , the orientation vector of the torque probe axis 21 in the plane of the page showing FIG. 2 has a radial component (parallel to a line extending radially from the center axis 11 of the engine 10 ) and an axial component (parallel to the center axis 11 ). The magnitude of the radial component of the orientation vector of the torque probe axis 21 is much greater than the magnitude of the axial component of the orientation vector, such that the torque probe axis 21 has a substantially radial orientation.

Referring to FIG. 1 , some or all of the torque probe 20 is positioned adjacent to the exhaust duct 17 within the exhaust case 15 A. By “adjacent”, it is understood that the torque probe 20 is positioned in proximity to the exhaust duct 17 such that it is exposed to heat radiating from the hot exterior surface 17 C of the exhaust duct 17 during operation of the engine 10 . In embodiments, only some of the torque probe 20 may be positioned adjacent to the exhaust duct 17 and exposed to its radiative heat. For example, in an embodiment, only the length of the torque probe 20 extending radially relative to the center axis 11 between the exhaust case 15 A and the bearing housing 40 is positioned adjacent to the exhaust duct 17 and exposed to its radiative heat. The torque probe 20 may also be exposed to convection heat transfer from the air heated by the surfaces of the exhaust duct 17 .

The proximity of the torque probe 20 and its electronic equipment to the exhaust duct 17 and the heat radiated by the exhaust duct 17 requires that thermal protection be provided to the torque probe 20 . Referring to FIG. 2 , some or all of the length of the torque probe 20 may be shielded from the hot exterior surface 17 C of the exhaust duct 17 by a thermal blanket 33 . The thermal blanket 33 is a covering which may be wrapped or draped around components to thermally insulate them. Referring to FIG. 2 , the thermal blanket 33 is disposed within the exhaust case 15 A. It is positioned axially, relative to the center axis 11 , between the torque probe 20 and the exhaust duct 17 , so as to cover the torque probe 20 and protect it from some of the radiative heat emanating from the exhaust duct 17 . The thermal blanket 33 has one or more openings 33 A through which the torque probe 20 is inserted and extends through. The thermal blanket 33 may be mounted to any suitable structure within the exhaust case 15 A. For example, and referring to FIG. 2 , part of the thermal blanket 33 extends along the bearing housing 40 and may be attached thereto.

The thermal blanket 33 provides temperature protection to the torque probe 20 by blocking at least some of the radiative heat from the exhaust duct 17 before it is experienced by the torque probe 20 . The thermal blanket 33 thus provides “passive” thermal protection because is protects the torque probe 20 solely because of its presence between the torque probe 20 and the exhaust duct 17 . Additional passive thermal protection may be provided by a torque probe heat shield 24 . Referring to FIG. 2 , the torque probe heat shield 24 encloses part of the annular body of the torque probe 20 to further thermally insulate the torque probe 20 by blocking at least some of the radiative heat from the exhaust duct 17 before it is experienced by the torque probe 20 . The torque probe heat shield 24 may have any suitable shape or arrangement to achieve this functionality. For example, the torque probe heat shield 24 may be a curved metal material positioned axially between the thermal blanket 33 and the torque probe 20 . In another possible configuration, the torque probe heat shield 24 is a box or cuboid enclosing some or all of the torque probe 20 . In yet another possible configuration, an example of which is shown in FIG. 2 , the torque probe heat shield 24 is, or includes, a sleeve 26 . The torque probe heat shield 24 may be used in the after-market, such as for retrofitting, replacing, or repairing a torque probe 20 and/or engine 10 to provide improved thermal protection for the torque probe 20 .

Referring to FIGS. 2 and 3 , the sleeve 26 is a hollow body which encloses or houses the torque probe 20 . The sleeve 26 is a separate and distinct component from the torque probe 20 , and is mounted to the torque probe 20 . In the embodiment shown in FIGS. 2 and 3 , the sleeve 26 is a cylindrical body which fully surrounds some or all of an cylindrical outer surface 21 A of the torque probe 20 . The outer surface 21 A of the torque probe 20 faces toward the interior of the exhaust case 15 A. Referring to FIG. 2 , the sleeve 26 fully surrounds only some of the length of the torque probe 20 . The sleeve 26 may have other annular shapes which achieve the above-described functionality. The sleeve 26 extends along a sleeve axis 26 A between a first sleeve end 27 A and a second sleeve end 27 B. Referring to FIG. 2 , the first sleeve end 27 A is disposed closer to the exhaust case 15 A than the second sleeve end 27 B. Referring to FIG. 2 , the second sleeve end 27 B is disposed closer to the bearing housing 40 than the first sleeve end 27 A. Most of the axial length of the sleeve 26 , defined along the sleeve axis 26 A, is located within the exhaust case 15 A and surrounds the outer surface 21 A of the torque probe 20 . Referring to FIGS. 2 and 4 , some of the sleeve 26 at the first sleeve end 27 A is positioned outside of the exhaust case 15 A in the nacelle flow passage 19 C. For example, an attachment nut 26 B of the sleeve 26 , used to secure the sleeve 26 to the torque probe 20 , is positioned outside of the exhaust case 15 A in the nacelle flow passage 19 C. When the sleeve 26 is mounted to the torque probe 20 , it is concentric with the torque probe 20 . When the sleeve 26 is mounted to the torque probe 20 , the sleeve axis 26 A is coaxial with the torque probe axis 21 .

For some engine configurations, the passive thermal protection provided by the thermal blanket 33 and/or the sleeve 26 may not be sufficient. The torque probe 20 may need to be further provided with more “active” thermal protection, which is now described in greater detail.

The active thermal protection of the torque probe 20 is provided by allowing a cooling fluid to flow along the outer surface 21 A of the torque probe 20 . This may be achieved in different ways. For example, and referring to FIG. 2 , an inner surface 26 BI of the sleeve 26 is spaced apart from the outer surface 21 A of the torque probe 20 in a direction being radial to both the sleeve axis 26 A and the torque probe axis 21 . This spacing of the inner surface 26 BI from the outer surface 21 A forms an annular gap that surrounds the outer surface 21 A. When a cooling fluid is allowed to circulate in this annular gap, the annular gap becomes a flow passage 28 . The flow passage 28 is concentric about the torque probe axis 21 . The flow passage 28 is concentric about the sleeve axis 26 A. The flow passage 28 is elongated, and extends in a direction that is parallel to the torque probe axis 21 .

Referring to FIGS. 2 and 3 , the cooling fluid enters the flow passage 28 through a flow passage inlet 28 A, and exits the flow passage 28 through a flow passage outlet 28 B. The cooling fluid therefore travels through the entirety of the flow passage 28 along the outer surface 21 A of the torque probe 20 to cool the torque probe 20 . The flow passage inlet and outlet 28 A, 28 B are defined in the sleeve 26 . The flow passage inlet and outlet 28 A, 28 B are axially spaced apart from each other along the sleeve axis 26 A. The flow passage inlet and outlet 28 A, 28 B are positioned entirely within the exhaust case 15 A. The flow passage inlet 28 A is in fluid communication with the bearing cavity 42 to receive the cooling fluid CF therefrom. The bearing cavity 42 is the source of the cooling fluid CF. The cooling fluid CF in FIG. 2 is therefore a mixture of air and oil entrained by the air from the bearing cavity 42 . The oil may be in the form of an oil mist entrained by the air from the bearing cavity 42 . The cooling fluid CF is said to be “cooling” because the air and oil mixture from the bearing cavity 42 is known to be at a lower temperature than the air within the exhaust case 15 A surrounding the torque probe 20 . Referring to FIG. 2 , the bearing housing 40 has a protruding housing portion 46 that extends radially and defines a bearing housing passage 46 A in fluid communication with both the flow passage inlet 28 A and the bearing cavity 42 . The bearing housing 40 also has an internal torque probe housing 48 within the exhaust case 15 A that is spaced apart from, and separate from, the bearing housing passage 46 A. The internal torque probe housing 48 is a cylindrical body that is coaxial along its length with the torque probe axis 21 . It defines a through passage leading into the bearing cavity 42 . The sleeve 26 is positioned in the internal torque probe housing 48 for displacement relative thereto, as explained in greater detail below. The torque probe 20 extends through the internal torque probe housing 48 . Referring to FIG. 2 , the sleeve 26 is sealed to the internal torque probe housing 48 on a side of the flow passage inlet 28 A that is closest to the bearing housing 40 , such as with an O-ring. This sealing helps to prevent oil mist and air from bearing cavity 42 entering the flow passage 28 or along the outer surface 21 A of the torque probe 20 .

Referring to FIGS. 2 and 3 , the flow passage inlet 28 A of the sleeve 26 is defined by one or more inlet slots 29 A that extending through the sleeve 26 and form an opening therein. The inlet slots 29 A extend from an inner surface of the sleeve 26 to an outer surface 26 D of the sleeve 26 . The inlet slots 29 A are spaced apart from each other around a circumference of the sleeve 26 . The inlet slots 29 A are spaced apart circumferentially relative to the torque probe axis 21 . The cooling fluid CF is directed along the torque probe axis 21 and along the sleeve axis 26 A toward the first sleeve end 27 A. Similarly, the flow passage outlet 28 B is defined by one or more outlet slots 29 B extending through the sleeve 26 . The outlet slots 29 B extend from the inner surface of the sleeve 26 to the outer surface 26 D of the sleeve 26 . The outlet slots 29 B are spaced apart from each other around a circumference of the sleeve 26 . The outlet slots 29 B are spaced apart circumferentially relative to the torque probe axis 21 . The outlet slots 29 B are positioned closer to the exhaust case 15 A than the inlet slots 29 A. The outlet slots 29 B are positioned radially outwardly from the inlet slots 29 A relative to the center axis 11 . The inlet and outlet slots 29 A, 29 B may be of the same design, arrangement and size, or may differ from each other in any one of these respects. The number and size of the inlet and outlet slots 29 A, 29 B may vary. It may be desirable to optimise the size of the inlet or outlet slots 29 A, 29 B to make them as large as possible in view of the available space constraints. Referring to FIGS. 2 and 3 , the inlet slots 29 A are disposed at the second sleeve end 27 B. The outlet slots 29 B are positioned between the first and second sleeve ends 27 A, 27 B. The outlet slots 29 B are closer to the exhaust case 15 A than the inlet slots 29 A. Thus, the flow passage outlet 28 B of the sleeve 26 is positioned between opposite ends of the sleeve 26 . In an alternate embodiment, the flow passage inlet 28 A and/or the flow passage outlet 28 B is defined by a singular annular opening in the sleeve 26 .

Referring to FIGS. 2 and 4 , a vent 36 is used to evacuate the cooling fluid CF from the exhaust case 15 A after it has been used to cool the torque probe 20 . The vent 36 , sometimes referred to herein as a vent line 36 , is any suitable tube, conduit, pipe, etc. that extends between a vent inlet 36 A in fluid communication with the flow passage outlet 28 B, and a vent outlet 36 B that is located outside of the exhaust case 15 A. Many different configurations of the vent 36 are possible to achieve this functionality. For example, and referring to FIGS. 2 and 4 , a boss 45 on the outer surface of the exhaust case 15 A defines part of the vent 36 . The boss 45 includes a boss vent line 45 A which extends through the exhaust case 15 A. An inner end of the boss vent line 45 A defines the vent inlet 36 A and is in direct fluid communication with the flow passage outlet 28 B. An outer end of the boss vent line 45 A is positioned outside of the exhaust case 15 A and is mounted to a main vent line 45 B which extends along the outer surface of the casing 15 of the engine 10 to the AGB 50 (see FIG. 1 ). The main vent line 45 B at the AGB 50 defines the vent outlet 36 B.

During operation of the engine 10 , the cooling fluid CF is caused to flow from the bearing cavity 42 to the main vent line 45 B. Referring to FIG. 2 , the cooling fluid CF flows from the bearing cavity 42 , through the bearing housing passage 46 A of the protruding housing portion 46 and into the inlet slots 29 A of the flow passage inlet 28 A. The cooling fluid CF is then conveyed through the flow passage 28 in a radially outward direction relative to the center axis 11 and in direct contact with the peripheral outer surface 21 A of the torque probe 20 to cool the torque probe 20 . It then flows through the outlet slots 29 B of the flow passage outlet 28 B, through the vent inlet 36 A of the boss vent line 45 B, out of the exhaust case 15 A via the boss vent line 45 A, and then along the main vent line 45 B toward the vent outlet 36 B.

The sleeve 26 and the flow passage 28 it defines thus use cooler fluid from the bearing cavity 42 to cool the torque probe 20 . Although it provides an active cooling solution when compared to the static, passive cooling solutions provided by the thermal blanket 33 and torque probe heat shield 24 , the cooling fluid CF is a passive fluid flow driven along the outer surface 21 A of the torque probe 20 . The cooling fluid CF is generated by the difference in pressure between the cooling fluid CF in the bearing cavity 42 and the pressure in the AGB 50 where the vent outlet 36 B is positioned. Referring to FIGS. 1, 2 and 4 , an interior of the reduction gearbox case 15 B is in fluid communication with an interior of the accessory gearbox case 15 E via the boss and main vent lines 45 A, 45 B. An interior of the reduction gearbox case 15 B is in fluid communication with the bearing cavity 42 . This arrangement may take many forms.

For example, and referring to FIG. 2 , the interior of the reduction gearbox case 15 B and the bearing cavity 42 form a common open space within the casing 15 through which fluid is free to travel. Therefore, the boss and main vent lines 45 A, 45 B fluidly link, via the sleeve 26 , the RGB 31 and the AGB 50 . The vent outlet 36 B is in fluid communication with the AGB 50 or the accessory gearbox case 15 E so that the cooling fluid CF may be discharged into the accessory gearbox case 15 E. The vent 36 therefore helps to balance the pressure between the RGB 31 and the AGB 50 . For example, air within the bearing cavity 42 may be pressurized to seal the bearings 44 , and is evacuated along with oil mist out of the RGB 31 cavity to the AGB 50 because the cavity of the accessory gearbox case 15 E is at a lower pressure than the reduction gearbox case 15 B. The pressure differential between fluid in the reduction gearbox case 15 B and the accessory gearbox case 15 E causes the cooling fluid CF to flow from the bearing cavity 42 to the accessory gearbox case 15 E, thereby allowing the cooling airflow CL to flow through the sleeve 26 along the outer surface 21 A of the torque probe 20 . The cooling fluid CF is thus driven passively by the pressure differential between the gearboxes 31 , 50 , and the cooling fluid CF is dumped into the accessory gearbox case 15 E. The cooling fluid CF is not actively driven by a pump or other device. In an alternate embodiment, however, a pump or other device may be used to supplement the cooling fluid CF, or to provide all of the cooling fluid CF. A fluid flow path is thus defined from the bearing cavity 42 to the vent outlet 36 B positioned outside of the exhaust case 15 A, such as in the accessory gearbox case 15 E.

Thus, in the configuration shown in FIG. 2 , the sleeve 26 and its flow passage 28 use the air and oil mist in the vent 36 between the RGB 31 and the AGB 50 to cool the torque probe 20 . This technique allows for employing an existing vent line 36 between the RGB 31 and the AGB 50 , which is already used to balance pressure between the gearboxes 31 , 50 , and give it an additional cooling function. The use of an existing component of the engine 10 , the vent line 36 , helps to minimize the weight impact of this cooling technique. Thus, this cooling technique uses the passive fluid flow through an existing vent line 36 of the engine 10 and diverts it along the torque probe 20 to provide cooling. In an alternate embodiment, the vent line 36 vents to another location of the engine 10 outside of the exhaust case 15 A that is at a lower pressure than the bearing cavity 42 .

By flowing in the flow passage 28 , the cooling fluid CF, which is cooler than the environment surrounding the exhaust duct 17 , helps to maintain the torque probe 20 at an acceptable temperature. The sleeve 26 defining the flow passage 28 thus provides a cooling scheme surrounding the torque probe 20 that allows for the installation of the torque probe 20 in a hot environment. This may allow the temperature of the torque probe 20 to remain within an acceptable limit. The cooling fluid CF is thus an “active” cooling method, when compared to the passive thermal blanket 33 and the torque probe heat shield 24 , which helps to provide increased cooling capacity. This may be helpful in conditions where the passive cooling systems are less efficient, such as during hot days or where there is low ventilation within the nacelle flow passage 19 C. Using such an active cooling method may allow for the torque probe 20 to be used in harsher and hotter environments. By contributing to thermally protecting the torque probe 20 from the turbine exhaust environment, the active cooling fluid CF contributes to ensuring the reliability, accuracy and durability of the engine measurement system. Indeed, in a configuration of the engine 10 , the active cooling provided by the cooling fluid CF is sufficient such that there is no need for the thermal blanket 33 , the heat shield formed by the sleeve 26 and the cooling fluid CF being sufficient to provide adequate thermal protection for the torque probe 20 .

Referring to FIGS. 2 and 4 , the boss 45 on the outer surface of the exhaust case 15 A also includes an external torque probe housing 49 . The external torque probe housing 49 defines the protruding feature of the boss 45 which extends radially outwardly from the exhaust case 15 A, and which delimits an opening 48 A in the exhaust case 15 A. The external torque probe housing 49 is used to locate the torque probe 20 and the sleeve 26 . The external torque probe housing 49 extends inwardly from the exhaust case 15 A a limited amount to locate the torque probe 20 and the sleeve 26 adjacent to the exhaust case 15 A. The external torque probe housing 49 is an annular body which encloses the torque probe 20 and the sleeve 26 therein. The first sleeve end 27 A is positioned radially outwardly of the external torque probe housing 49 , as is part of the torque probe 20 . The torque probe 20 and the sleeve 26 extend through the opening 48 A.

Referring to FIG. 2 , the sleeve 26 has suitable sealing to prevent the air and oil mixture of the cooling fluid CF from entering the hot zone surrounding the exhaust duct 17 , and to prevent the cooling fluid CF from entering the nacelle flow passage 19 C. The sleeve 26 is sealed to the exhaust case 15 A, such that the cooling fluid CF is prevented from entering, or escaping from, the exhaust case 15 A. Referring to FIG. 2 , the sleeve 26 has sealing on opposite sides of the flow passage outlet 28 B. The sleeve 26 is sealed on a first side of the flow passage outlet 28 B that is closer to exhaust case 15 A, and is also sealed to the exhaust case 15 A on a second side of the flow passage outlet 28 B that is closer to the bearing housing 40 than the first side of the flow passage outlet 28 B. The sealing with the exhaust case 15 A defines a plenum 43 about or around the flow passage outlet 28 B. Referring to FIG. 2 , the plenum 43 is an annular volume that circumferentially surrounds the cylindrical outer surface 26 D of the sleeve 26 . The plenum 43 is in fluid communication with the vent inlet 36 A, such that the cooling fluid CF flows through the outlet slots 29 B, into the plenum 43 and through the vent inlet 36 A. The sealing of the exhausts case 15 A thus confines the cooling fluid CF to flow through the flow passage 28 and along the torque probe 20 , thereby preventing the cooling fluid CF from exiting exhaust case 15 A except via the path to the vent outlet 36 B.

Referring to FIG. 2 , one possible configuration of sealing for the sleeve 26 is described in greater detail. The external torque probe housing 49 extends inwardly from the exhaust case 15 A and delimits the opening 48 A in the exhaust case 15 A. A first seal 41 A is positioned between an inner surface of the external torque probe housing 49 and the outer surface 26 D of the sleeve 26 on the first side of the flow passage outlet 28 B closest to the exhaust case 15 A. The first seal 41 A helps to seal off the plenum 43 so that the cooling fluid CF therein does not escape through the opening 48 A into the nacelle flow passage 19 C. A second seal 41 B is positioned between the inner surface of the torque probe housing 49 and the outer surface 26 D of the sleeve 26 on the second side of the flow passage outlet 28 B closest to the bearing housing 40 . The second seal 41 B helps to seal off the plenum 43 so that the cooling fluid CF therein does not escape into the hot zone of the exhaust case 15 A surrounding the exhaust duct 17 . The first and second seals 41 A, 41 B delimit the plenum 43 along with the surfaces of the sleeve 26 and the external torque probe housing 49 . The axial extent of the plenum 43 , as measured in a direction parallel to the sleeve axis 26 A, is defined between the axially spaced-apart first and second seals 41 A, 41 B. In the configuration shown, once the cooling fluid CF exits the sleeve 26 , it enters the plenum 43 created by the first and second seals 41 A, 41 B, to then flow passively into the vent inlet 36 A. The first and second seals 41 A, 41 B are dynamic seals. As opposed to static seals, the first and second seals 41 A, 41 B accommodate the movement of the torque probe 20 and of the sleeve 26 relative to the exhaust case 15 A during operation of the engine 10 , while still performing their sealing function. The torque probe 20 and sleeve 26 are mounted relative to exhaust case 15 A and the bearing housing 40 such that they are able to displace relative to these bodies in a direction along the torque probe axis 21 due to thermal loads, or due to maneuver loads during aircraft fight. The first and second seals 41 A, 41 B may be mounted against any suitable land or flange of the sleeve 26 and/or of the external torque probe housing 49 , as shown in FIG. 2 . Alternatively, one or both of the first or second seals 41 A, 41 B may be static seals. In an alternate embodiment, the sleeve 26 is free of sealing with the exhaust case 15 A. In such an embodiment, the flow passage outlet 28 B is directly coupled to the vent inlet 36 A.

Referring to FIG. 2 , and as mentioned above, the sleeve 26 and flow passage 28 cooling technique disclosed herein may be applied against only some of the length of the torque probe 20 , as measured along the torque probe axis 21 . The torque probe includes a first torque probe segment 23 A having a first length defined along the torque probe axis 21 , and a second torque probe segment 23 B extending from the first torque probe segment 23 A and having a second length defined along the torque probe axis 21 . The first torque probe segment 23 A is disposed within the exhaust case 15 A and is exposed to the exhaust duct 17 , such that first torque probe segment 23 A is exposed to heat radiating from the hot exterior surface 17 C of the exhaust duct 17 during operation of the engine 10 . The second torque probe segment 23 B is longer than the first torque probe segment 23 A. The second torque probe segment 23 B extends radially inwardly relative to the center axis 11 from the first torque probe segment 23 A through the bearing cavity 42 to an end in proximity to the output shaft 18 A. The flow passage 28 defined by the sleeve 26 extends along only the first length of the first torque probe segment 23 A, since this is the portion of the torque probe 20 that may require thermal protection. Referring to FIG. 2 , some or all of the first torque probe segment 23 A lies, or is positioned, outside of the thermal blanket 33 . The second torque probe segment 23 B is covered by the thermal blanket 33 .

Referring to FIG. 5 , another configuration for cooling the torque probe 20 is now described in greater detail. Any feature shown in FIG. 5 which is not annotated with a reference number has the same reference number as the similar feature shown in FIGS. 1 - 4 . Similarly, the description of a feature above with respect to FIGS. 1-4 applies mutatis mutandis to the similar feature shown in FIG. 5 . A vent conduit 45 A is disposed partially within the exhaust case 15 A, and also extends through the exhaust case 15 A. The vent conduit 45 A extends through another opening 450 in the exhaust case 15 A delimited by the boss 45 on the outer surface of the exhaust case 15 A. The vent conduit 45 A is a separate component from the main vent line 45 B and from the sleeve 26 . The vent conduit 45 A is disposed between the sleeve 26 and the vent 36 .

An inner end of the vent conduit 45 A defines a vent conduit inlet 45 AI and is in fluid communication with the flow passage outlet 28 B within the exhaust case 15 A. An outer end of the vent conduit 45 A is positioned outside of the exhaust case 15 A and defines a vent conduit outlet 45 AO. The vent conduit outlet 45 AO is in fluid communication with the vent inlet 36 A. The outer end is mounted to the main vent line 45 B which extends along the outer surface of the casing 15 of the engine 10 to another portion of the casing 15 , such as the accessory gearbox case 15 E. The inner end of the vent conduit 45 A is threaded and is fixedly mounted to a venting line mounting 46 B that is part of the bearing housing 40 . The venting line mounting 46 B defines a venting line mounting passage 46 BP through which the cooling fluid CF enters after exiting the flow passage outlet 28 B. The vent conduit 45 A does not displace relative to the exhaust case 15 A. The configuration represented in FIG. 5 shows that the cooling fluid CF flows indirectly between the flow passage 28 and the vent 36 , via a separate threaded venting line mounting 46 B. Although shown in FIG. 5 as being covered by the thermal blanket 33 , the venting line mounting 46 B may be uncovered and unshielded relative to the exhaust duct 17 because it is merely a transfer tube that is free of heat sensitive electronic components.

Referring to FIG. 5 , a plenum body 43 A, shown in FIG. 5 as another sleeve, is sealed to the exhaust case 15 A on a first side of the flow passage outlet 28 B nearest to the exhaust case 15 A, and is sealed to the bearing housing 40 on a second side of the flow passage outlet 28 B nearest to the bearing housing 40 . The plenum body 43 A is also spaced apart from the outer surface 26 D of the sleeve 28 , so as to form a second plenum 43 C about the flow passage outlet 28 B between the plenum body 43 A and the sleeve 26 . The second plenum 43 C is an annular volume that circumferentially surrounds the cylindrical outer surface 26 D of the sleeve 26 . The second plenum 43 is in fluid communication with the vent conduit inlet 45 AI via the venting line mounting 46 B, such that the cooling fluid CF flows through the outlet slots 29 B, into the second plenum 43 C and through the venting line mounting 46 B. The axial extent of the second plenum 43 C, as measured in a direction parallel to the sleeve axis 26 A, is defined between the axially spaced-apart seals shown in FIG. 5 .

One possible sealing configuration is shown in FIG. 5 . A rope seal 141 A is defined between an outer surface of the plenum body 43 A and the boss or other surface of the exhaust case 15 A, to prevent air from the nacelle flow passage 19 C flowing into the exhaust case 15 A. A first static O-ring 141 B 1 is provided between the outer surface 21 A of the torque probe 20 and an inner surface of the sleeve 26 , a second static O-ring 141 B 2 is provided between the outer surface 26 D of the sleeve 26 and the inner surface of the plenum body 43 A, and a third static O-ring 141 B 3 is provided between an outer surface of the plenum body 43 A and an inner surface of the bearing housing portion 46 . The first, second and third static O-rings 141 B 1 , 141 B 2 , 141 B 3 prevent relative movement between their sealed components, such that the torque probe 20 , the sleeve 26 , the bearing housing portion 46 and the plenum body 43 A are configured to displace together relative to the exhaust case 15 A in response to thermal or maneuvering loads, as explained above. The first and second static O-rings 141 B 1 and 141 B 2 prevent the oil and air mixture of cooling fluid CF from escaping the second plenum 43 C and entering the nacelle flow passage 19 C. The third static O-ring 141 B 3 prevents the oil and air mixture of cooling fluid CF from escaping the second plenum 43 C and entering the inner cavity of the exhaust case 15 A. A static metallic crush seal 141 C is provided between the inner end of the vent conduit 45 A and the outlet of the venting line mounting 46 B. When the vent conduit 45 A is threadably attached to the venting line mounting 46 B, the static metallic crush seal 141 C is compressed to create a seal.

The vent conduit 45 A and the main vent line 45 B may be attached together using any suitable technique. For example, and referring to FIG. 5 , the outer end of the vent conduit 45 A includes a floating flange 47 that is mounted to the main vent line 45 B. In the illustrated embodiment, the orientation of the vent conduit 45 A may be difficult to predict once it has been threadably attached to the venting line mounting 46 B, whereas the orientation of the main vent line 45 B and its direction along the outer surface of the exhaust case 15 A is known. The floating flange 47 allows the vent conduit 45 A to be connected to the main vent line 45 B irrespective of the orientation of the outer end of the vent conduit 45 A. The floating flange 47 may have any suitable configuration to achieve this functionality. For example, the floating flange 47 may be shaped like a parallelogram and have a central aperture 47 A. The floating flange 47 is placed onto the outer end of the vent conduit 45 A after the vent conduit 45 A has been mounted to the bearing housing 40 , by inserting the outer end of the vent conduit 45 A into the central aperture 47 A of the floating flange 47 . The orientation of the floating flange 47 can be selected based on the known orientation of the mating flange 47 B of the main vent line 45 B. Once the floating flange 47 and the mating flange 47 B are brought together, they may be secured to one another with suitable fasteners, so as to fluidly connect the internal and external venting lines 45 A, 45 B such that the main vent line 45 B has the desired orientation toward the AGB 50 .

During operation of the engine 10 in the configuration shown in FIG. 5 , the cooling fluid CF is conveyed passively from the bearing cavity 42 , through the bearing housing passage 46 A and into the flow passage 28 via the inlet slots 29 A. The cooling fluid CF travels in a radially outward direction relative to the center axis 11 and in direct contact with the peripheral outer surface 21 A of the torque probe 20 to cool the torque probe 20 . It then flows through the outlet slots 29 B of the flow passage outlet 28 B, into the second plenum 43 C, and through the venting line mounting passage 46 BP before entering the vent conduit 45 A. It then flows along the vent conduit 45 A out of the exhaust case 15 A, and then along the main vent line 45 B toward the vent outlet 36 B at the AGB 50 .

Referring to FIG. 2 , a method for cooling the torque probe 20 includes forming the fluid flow path from the bearing cavity 42 to the vent outlet 36 B positioned outside of the exhaust case 15 A, such as at the accessory gearbox case 15 E. The method includes positioning the torque probe 20 within the fluid flow path downstream of the bearing cavity 42 and upstream of the vent outlet 36 B. The cooling fluid CF flows from the bearing cavity 42 , along the torque probe 20 to cool the torque probe 20 , and to the vent outlet 36 B when the engine 10 is operating. Referring to FIG. 2 , a method of cooling the torque probe 42 includes allowing an oil and air mixture from the bearing housing 40 to be driven along the outer surface 21 A of the torque probe 20 , either passively or actively. The method also includes discharging the oil and air mixture out of the exhaust case 15 A enclosing part of the torque probe 20 .

The embodiments described in this document provide non-limiting examples of possible implementations of the present technology. Upon review of the present disclosure, a person of ordinary skill in the art will recognize that changes may be made to the embodiments described herein without departing from the scope of the present technology. Yet further modifications could be implemented by a person of ordinary skill in the art in view of the present disclosure, and such modifications would be within the scope of the present technology.