Patent Description:
Gas turbine engine efficiency is directly related to the level of control of the gap between a blade tip and a corresponding outer air seal. A capacitance-based BTC probe (cap probe) may be placed proximate the outer air seal to monitor this gap. Traditional cap probes and cap probe installations tend to alter engine structures comprising the outer air seal, tending thereby to compromise the operation of the air seal and tending to reduce engine efficiency.

<CIT> discloses a turbomachine stage having a housing in which is arranged a moving vane arrangement with multiple moving vanes which have an exterior shroud band with at least one radial sealing flange. The sealing flange has a recess arrangement with at least one radial recess in which a radial projection is arranged. There is arranged on the housing a sensor arrangement with at least one capacitive sensor for detecting a radial clearance to a peripheral surface of the sealing flange.

According to an aspect of the invention, there is provided a method for measuring axial shift and radial gap of rotating components of gas turbine engines as recited in claim <NUM>.

The detailed description of exemplary embodiments herein makes reference to the accompanying drawings, which show exemplary embodiments by way of illustration and their best mode. While these exemplary embodiments are described in sufficient detail to enable those skilled in the art to practice the disclosures, it should be understood that other embodiments may be realized and that logical, chemical, and mechanical changes may be made without departing from the scope of the disclosures. For example, the steps recited in any of the method or process descriptions may be executed in any order and are not necessarily limited to the order presented. Also, any reference to attached, fixed, connected or the like may include permanent, removable, temporary, partial, full and/or any other possible attachment option.

In various embodiments and with reference to <FIG>, a gas turbine engine <NUM> is provided. Gas turbine engine <NUM> may be a two-spool turbofan that generally incorporates a fan section <NUM>, a compressor section <NUM>, a combustor section <NUM> and a turbine section <NUM>. Alternative engines may include, for example, an augmenter section among other systems or features. In operation, fan section <NUM> can drive air along a bypass flow-path B while compressor section <NUM> can drive air for compression and communication into combustor section <NUM> then expansion through turbine section <NUM>. Although depicted as a turbofan gas turbine engine <NUM> herein, it should be understood that the concepts described herein are not limited to use with turbofans as the teachings may be applied to other types of turbine engines including turbojet engines, a low-bypass turbofans, a high bypass turbofans, or any other gas turbine known to those skilled in the art including single spool and three-spool architectures.

Gas turbine engine <NUM> may generally comprise a low speed spool <NUM> and a high speed spool <NUM> mounted for rotation about an engine central longitudinal axis A-A' relative to an engine static structure <NUM> via one or more bearing systems <NUM> (shown as bearing system <NUM>-<NUM> and bearing system <NUM>-<NUM>). It should be understood that various bearing systems <NUM> at various locations may alternatively or additionally be provided, including for example, bearing system <NUM>, bearing system <NUM>-<NUM>, and bearing system <NUM>-<NUM>.

Low speed spool <NUM> may generally comprise an inner shaft <NUM> that interconnects a fan <NUM>, a low pressure (or first) compressor section <NUM> (also referred to a low pressure compressor) and a low pressure (or first) turbine section <NUM>. Inner shaft <NUM> may be connected to fan <NUM> through a geared architecture <NUM> that can drive fan <NUM> at a lower speed than low speed spool <NUM>. Geared architecture <NUM> may comprise a gear assembly <NUM> enclosed within a gear housing <NUM>. Gear assembly <NUM> couples inner shaft <NUM> to a rotating fan structure. High speed spool <NUM> may comprise an outer shaft <NUM> that interconnects a high pressure compressor ("HPC") <NUM> (e.g., a second compressor section) and high pressure (or second) turbine section <NUM>. A combustor <NUM> may be located between HPC <NUM> and high pressure turbine <NUM>. A mid-turbine frame <NUM> of engine static structure <NUM> may be located generally between high pressure turbine <NUM> and low pressure turbine <NUM>. Mid-turbine frame <NUM> may support one or more bearing systems <NUM> in turbine section <NUM>. Inner shaft <NUM> and outer shaft <NUM> may be concentric and rotate via bearing systems <NUM> about the engine central longitudinal axis A-A', which is collinear with their longitudinal axes. As used herein, a "high pressure" compressor or turbine experiences a higher pressure than a corresponding "low pressure" compressor or turbine.

The core airflow C may be compressed by low pressure compressor <NUM> then HPC <NUM>, mixed and burned with fuel in combustor <NUM>, then expanded over high pressure turbine <NUM> and low pressure turbine <NUM>. Mid-turbine frame <NUM> includes airfoils <NUM> which are in the core airflow path. Low pressure turbine <NUM>, and high pressure turbine <NUM> rotationally drive the respective low speed spool <NUM> and high speed spool <NUM> in response to the expansion.

HPC <NUM> may comprise alternating rows of rotating rotors and stationary stators. Stators may have a cantilevered configuration or a shrouded configuration. More specifically, a stator may comprise a stator vane, a casing support and a hub support. In this regard, a stator vane may be supported along an outer diameter by a casing support and along an inner diameter by a hub support. In contrast, a cantilevered stator may comprise a stator vane that is only retained and/or supported at the casing (e.g., along an outer diameter). One or more BTC probes <NUM> (<FIG> described below) may be located radially outward of a compressor blade of compressor section <NUM>, a turbine blade of turbine section <NUM> and may be embedded, respectively, in a compressor case or a turbine case, or as may be located radially outward of a fan blade as described below with reference to <FIG>.

Rotors may be configured to compress and spin a fluid flow. Stators may be configured to receive and straighten the fluid flow. In operation, the fluid flow discharged from the trailing edge of stators may be straightened (e.g., the flow may be directed in a substantially parallel path to the centerline of the engine and/or HPC) to increase and/or improve the efficiency of the engine and, more specifically, to achieve maximum and/or near maximum compression and efficiency when the straightened air is compressed and spun by rotor <NUM>.

With reference to <FIG> and <FIG>, a fan section <NUM> having a probe <NUM>, is provided. Fan <NUM> comprises blade <NUM> coupled at blade root <NUM> to a fan disk <NUM> and compressor inlet cone <NUM>. Fan <NUM> may be coupled to a shaft, such as inner shaft <NUM>, where inner shaft <NUM> may be in mechanical communication with geared architecture <NUM>, or may be in mechanical communication with the low spool shaft directly. Tip <NUM> of blade <NUM> lies proximate rub strip <NUM> which forms a part of the inner aerodynamic surface <NUM> of fan case <NUM>. A BTC probe <NUM> lies radially outward of blade <NUM> and proximate tip <NUM> between inner aerodynamic surface <NUM> and outer casing <NUM> of fan case <NUM>. BTC probe <NUM> comprises a portion of rub strip <NUM> and may be co-molded in part with rub strip <NUM> or may be embedded within rub strip <NUM>. Fan case <NUM> may be coupled at an aft end to pylon <NUM> which may be coupled to compressor casing <NUM>. As fan <NUM> rotates about the shaft it tends to draw in gas <NUM>, such as, for example air, at the fore end of fan case <NUM>. Rotating fan <NUM> tends to accelerate gas <NUM> along inner aerodynamic surface <NUM> toward pylon <NUM> passing between inner aerodynamic surface <NUM> and compressor casing <NUM> as fan exhaust <NUM>.

Portion of gas <NUM> may escape fan <NUM> by passing over tip <NUM> through a gap <NUM> between tip <NUM> and inner aerodynamic surface <NUM> tending to decrease efficiency. The width of gap <NUM> between tip <NUM> and inner aerodynamic surface <NUM> may vary with respect to a position along the chord line of blade <NUM>. The BTC probe <NUM> may be located axially (relative to the axis of rotation of fan <NUM>, with momentary reference to A-A' in <FIG>) within a bounded portion of rub strip <NUM> bounded at the forward end by a leading edge of blade <NUM> and at the aft end by a trailing edge of blade <NUM>. A plurality of BTC probes may be located axially within the bounded portion of rub strip <NUM> along the chord of blade <NUM>. A plurality of BTC probes may be located circumferentially around fan section <NUM> within the bounded portion of rub strip <NUM>.

With additional reference to <FIG>, a BTC probe <NUM> may comprise a housing <NUM> and a cap <NUM> enclosing an interior volume of the housing <NUM> when coupled at a top surface of a body <NUM> of the housing <NUM>. Housing <NUM> may comprise a portion of rub strip <NUM>, or may comprise a portion of a turbine case, or a compressor case. Cap <NUM> may comprise an alignment feature <NUM> configured to align with an alignment block <NUM> of housing 302Housing <NUM> may further comprise a body <NUM> having a top surface and a cylindrical portion <NUM> extending toward a bottom surface <NUM>. A neck <NUM> may extend radially from body <NUM> and alignment block <NUM> may comprise a portion of neck <NUM>. A hard lead <NUM> may be inserted through housing <NUM> via neck <NUM>. Housing <NUM> may enclose a sensor element <NUM>. A sensor head <NUM> of sensor element <NUM> may extend through bottom surface <NUM>. Sensor element <NUM> may be surrounded by an inner hat insulator <NUM>, an inner housing <NUM> and an outer hat insulator <NUM>.

With additional reference to <FIG> and <FIG> a BTC probe <NUM> may comprise a housing <NUM> having features, geometries, construction, materials, manufacturing techniques, and/or internal components similar to housing <NUM>. Housing <NUM> may be mounted radially outward of a structure <NUM> such as, for example, a turbine case or a compressor case. Housing <NUM> may comprise a body <NUM> having neck <NUM> extending radially from the body <NUM> configured to accept hard lead <NUM>. Housing <NUM> may further comprise a cap <NUM> enclosing an interior volume of the housing <NUM> when coupled at a top surface of body <NUM>. Body <NUM> may comprise a bottom surface <NUM> opposite the top surface and in contact with structure <NUM>. Bottom surface <NUM> may be positioned proximate bore <NUM> and counterbore <NUM> through structure <NUM>. Sensor element <NUM> may be inserted into bore <NUM> and counterbore <NUM> with shank <NUM> of sensor element <NUM> extending radially through structure <NUM> into housing <NUM>. Shank <NUM> may be coupled at threaded coupling <NUM> to nut <NUM> and insulated from contact with body <NUM> and structure <NUM> by hat insulator <NUM>. With nut <NUM> coupled to shank <NUM> sensor head <NUM> of sensor element <NUM> may be drawn to rest within counterbore <NUM> against counterbore insulator <NUM>. In this regard, sensor element <NUM> may couple housing <NUM> to structure <NUM>.

With brief reference to <FIG>, a hard lead such as hard lead <NUM> may be a driven guard hard lead and comprise a lead wire <NUM> surrounded by a driven guard <NUM> containing a first layer of insulating material <NUM> therein. Driven guard <NUM> is surrounded by a second layer of insulating material <NUM> contained within a hard shield <NUM> such as, for example, a metallic tube such as one of a steel, a stainless steel, an alloy, and/or an aluminum. A length L1 of driven guard <NUM> and a length L2 of lead wire <NUM> are exposed for assembly. Lead wire <NUM> is coupled to and is in electronic communication with a sensor element, such as sensor element <NUM> or <NUM>. Hard shield <NUM> is coupled to and in electronic communication with a housing such as housing <NUM> or <NUM>. Driven guard <NUM> may be coupled to and in electronic communication with an interior structure of a housing such as, for example, inner housing <NUM>. A hard lead such as hard lead <NUM> may have a diameter about <NUM> in. (<NUM>) where about in this context means +/-<NUM> in.

With additional reference to <FIG>, various head shapes of a sensor head of a sensor element having features, geometries, construction, materials, manufacturing techniques, and/or internal components similar to sensor element <NUM> and sensor element <NUM> are illustrated in a radial orientation as viewed toward a bottom surface of a body of a housing such as, for example, housing <NUM> or housing <NUM>. Triangular head 600a is defined at first vertex 602a, second vertex 604a, and third vertex 606a each having a corresponding interior angle. Triangular head 600a may be defined by first vertex 602a, second vertex 604a, and third vertex 606a to have a desired planform such as, for example, isosceles, equilateral, scalene, acute, obtuse, right, and/or the like. Quadrilateral head 600b is defined at first vertex 602b, second vertex 604b, third vertex 606b, and fourth vertex 608b each having a corresponding interior angle. In this regard, quadrilateral head may define a quadrilateral having a desired planform such as, for example, rectangular, square, rhomboidal, trapezoidal, frustoconical, and/or the like. A cranked arrow head <NUM> is defined at first vertex <NUM>, second vertex <NUM>, third vertex <NUM>, and fourth vertex <NUM> with a fifth vertex <NUM> and a sixth vertex <NUM>. The fifth vertex <NUM> and the sixth vertex <NUM> may define an area of relatively increased or decreased X-Z slope along the perimeter of the cranked arrow head <NUM> between each of their respective adjacent vertexes.

A concave head 600c may comprise a concave curve 602c and may be defined between a first vertex 604c a second vertex 606c and a third vertex 608c. A convex head 600d may comprise a convex curve 602d and may be defined between a first vertex 604d a second vertex 606d and a third vertex 608d. A compound curved head 600e may comprise a compound curve 602e and may be defined between a first vertex 604e a second vertex 606e and a third vertex 608e. Compound curve 602e may comprise a local plateau 610e defined by a region of relatively low X-Z slope along the perimeter of the compound curved head where the ratio of change in Z-axis position with respect to X-axis position is less than or equal <NUM>:<NUM>. The local plateau 610e may have a region where the slope is zero.

Curved heads (600c, 600d, and 600e) may be unilateral or bilateral. Stated another way, and with additional reference <FIG>, the curve of a curved head may be mirrored about a centerline (i.e., 612f) perpendicular to a line defined between the first vertex (e.g., 604c, 604e, 604f) and the second vertex (e.g., 606c, 606e, 606f). In a similar manner, any of the curves (602c, 602d, 602e) may be offset relative to the Z-axis and/or truncated with respect to the X-axis tending thereby to define a frustum or half-frustum with the third vertex (e.g., 608f) and a fourth vertex (e.g., 610f). Any of the vertexes of the various heads (600a, 600b, 600c, 600d, 600e, 600f, and <NUM>) may be rounded tending thereby to ease manufacturing and reduce stress concentrations which may develop at hard corners.

With renewed reference again to <FIG>, a sensor element of BTC probe <NUM>, such as sensor element <NUM> or sensor element <NUM>, may be energized by lead wire <NUM> and an electric field flows between the sensor element a ground plane such as, for example, structure. As a blade tip, such as tip <NUM> of blade <NUM>, passes proximate to sensor element <NUM>, an electric field tends to flow across gap <NUM> into the blade tip inducing a capacitance between the blade tip and the sensor element <NUM> which tends to vary with respect to the width of gap <NUM>. In this regard, the gap between a non-continuous target (e.g., a blade tip of a turbine blade) and a sensor head may be determined as a function of the change in capacitance occurring at a frequency which is a function of the time the blade tip dwells within the electric field. In a similar manner, a BTC probe <NUM> may be used to measure a gap between a probe head and other rotating components of gas turbine engine <NUM> which may be continuous or nearly continuous targets such as, for example, a knife edge seal.

In various embodiments and with additional reference to <FIG>, a schematic diagram of a system <NUM> for measuring axial shift and radial gap of rotating components of gas turbine engines, such as gas turbine engine <NUM>, is illustrated. System <NUM> may comprise sensors <NUM>, controller <NUM>, and a display system <NUM>. Sensors <NUM> may be in electronic communication with controller <NUM> and comprise one or more BTC probes <NUM>. Sensors <NUM> may output sensor data <NUM> to controller <NUM>. In various embodiments, sensor data <NUM> may comprise a time varying signal with respect to a voltage (i.e., a time variant voltage signal). As discussed above with regard to capacitance between the blade tip and the sensor element, the peak voltage of the time variant voltage signal may be a function of the distance between the target (e.g., a blade tip) and the sensor. In various embodiments, the voltage signal function for a target distance (e.g., a gap such as gap <NUM>) may vary dependent upon target axial position as shown in <FIG> illustrates four voltage-distance curves X1, X2, X3, and X4 each correlated to an axial position (for example a position along axis A-A' of gas turbine engine <NUM>) of a target such as, for example, a blade tip or knife edge seal.

A sensor head of the BTC probe <NUM> may be configured as described with reference to <FIG> above to generate a desired position (axial or radial) variant response (i.e., variant with respect to the position of a target) in the time varying signal of sensor data <NUM>. The sensors <NUM> may comprise a first BTC sensor configured to generate an axial position variant response in the time varying signal. In this regard, and in a similar fashion to the various voltage-distance curves, a pulse width of the time variant voltage signal may vary with respect to axial position as shown in <FIG>.

<FIG> illustrates the path of blade tips <NUM> over a triangular head <NUM> of a first BTC sensor and a rectangular quadrilateral head <NUM> of a second BTC sensor. Blade tips <NUM> may shift axially (X-axis) with respect to triangular head <NUM> as indicated by arrow <NUM> along the axis of rotation A-A' of a gas turbine engine. In response, the pulse width P of a first time variant voltage signal <NUM>' from the first BTC sensor may change from a first pulse width P1 to a second pulse width P2. In comparison, shifting blade tips <NUM> as indicated by arrow <NUM> with respect to rectangular quadrilateral head <NUM> produces a steady state response in the pulse width P of a second time variant voltage signal <NUM>' from the second BTC sensor. In this regard, controller <NUM> may determine an axial position of a rotating target such as blade tips <NUM> based on the variance between the first pulse width P1 and the second pulse width P2. P1 may be correlated with a first voltage-distance curve (e.g., X1) and P2 may be correlated with a second voltage-distance curve (e.g., X2). In this regard, a radial distance between the first BTC sensor and the target such as blade tips <NUM> may be determined based on a voltage distance curve calibrated to the axial position of the target.

In like regard and as illustrated by <FIG>, controller <NUM> may determine an axial position of a rotating target such as knife edge seal <NUM>. Knife edge seal may shift axially along axis of rotation A-A' of a gas turbine with respect to triangular head <NUM> to a position <NUM>'. Knife edge seal <NUM> may comprise a small gap <NUM>. In response the pulse width from the first BTC sensor may change from a first pulse width P to a second pulse width P' as marked between dropouts produced by gap <NUM> from a relatively steady state voltage. The steady state voltage may between about <NUM> volt to about <NUM> millivolts where about in this context means ± <NUM> millivolts.

In various embodiments, and with reference to <FIG>, controller <NUM> determines an axial position of a rotating target such as knife edge seal <NUM> which may be a continuous target. As knife edge seal <NUM> shifts axially as indicated by arrow <NUM>, voltage variance with respect to time is relatively steady state. However, in response to an axial shift in the knife edge seal <NUM> the first BTC sensor generates a position variant voltage signal <NUM>" while the second BTC sensor generates a relatively steady state voltage signal <NUM>". In this regard, controller <NUM> determines the axial shift of the knife edge seal <NUM> as a function of the position variant voltage signal and the stead state voltage signal. In various embodiments, controller <NUM> may determine a target background error correction based on the steady state voltage signal.

Display system <NUM> may be in electronic communication with controller <NUM> and receive position data <NUM> from controller <NUM>. Display system <NUM> may comprise hardware and/or software configured to display position data <NUM>. The position data <NUM> may comprise engineering units describing an axial shift (along the X-axis, i.e. the axis of rotation of gas turbine engine <NUM>) of a rotating component with respect to the position of a sensor. The position data <NUM> may comprise engineering units describing a radial gap between the rotating component and the sensor.

Any of the system <NUM> components may be in communication with controller <NUM> via a network. System <NUM> may be computer based, and may comprise a processor, a tangible non-transitory computer-readable memory, and/or a network interface, along with other suitable system software and hardware components. Controller <NUM> may be implemented in a single processor or one or more processors configured to implement various logical operations in response to execution of instructions, for example, instructions stored on a non-transitory, tangible, computer-readable medium such as, for example, memory <NUM> which may store data used, for example, for trending and analysis/prognosis purposes. The one or more processors can be a general purpose processor, a microprocessor, a microcontroller, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof. Controller <NUM> may be configured as a central network element or hub to access various systems, engines, and components of system <NUM>. Controller <NUM> may comprise a network, computer-based system, and/or software components configured to provide an access point to various systems, engines, and components of system <NUM>.

With reference now to <FIG>, a method <NUM> of determining the position of a rotating component may comprise controller <NUM> receiving sensor data <NUM> comprising a first time variant voltage signal (step <NUM>) from BTC probe <NUM>. Controller <NUM> may extract a first pulse width and a second pulse width from the sensor data <NUM> (step <NUM>). Controller <NUM> may determine an axial position of a rotating target (such as, for example, blade tips <NUM>, knife edge seal <NUM>, or knife edge seal <NUM>) based on the variance between the first pulse width and the second pulse width (step <NUM>). Controller <NUM> may select a voltage-distance curve based on the first pulse width and the second pulse width (step <NUM>). Controller <NUM> may determine a radial position of the rotating target based on the voltage component of the first time voltage signal and the voltage distance curve (step <NUM>). Controller <NUM> may receive a second a second time variant voltage signal. Controller <NUM> may determine the axial position of the rotating target based a voltage variance between the first time variant voltage signal and the second time variant voltage signal, wherein the voltage variance with respect to time is relatively steady state for each of the first time variant voltage signal and the second time variant voltage signal.

However, the benefits, advantages, solutions to problems, and any elements that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as critical, required, or essential features or elements of the disclosures.

The scope of the disclosures is accordingly to be limited by nothing other than the appended claims, in which reference to an element in the singular is not intended to mean "one and only one" unless explicitly so stated, but rather "one or more.

In the detailed description herein, references to "one embodiment", "an embodiment", "an example embodiment", etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. After reading the description, it will be apparent to one skilled in the relevant art(s) how to implement the disclosure in alternative embodiment.

Claim 1:
A system (<NUM>) for measuring axial shift and radial gap of rotating components (<NUM>) of gas turbine engines (<NUM>), the system (<NUM>) comprising:
a processor; and
a tangible, non-transitory memory configured to communicate with the processor,
the tangible, non-transitory memory having instructions stored thereon that, in response to execution by the processor, cause the processor to perform operations comprising:
receiving, by the processor, a first time variant voltage signal (<NUM>") from a first blade tip clearance sensor, wherein in response to an axial shift (<NUM>) in a rotating component (<NUM>) the first blade tip clearance sensor is configured to generate a position variant response in the first time variant voltage signal (<NUM>"); and
wherein the system (<NUM>) is characterised by the operations further comprising:
receiving, by the processor, a second time variant voltage signal (<NUM>") from a second blade tip clearance sensor, wherein in response to an axial shift (<NUM>) in a rotating component the second blade tip clearance sensor is configured to generate a relatively steady state response in the second time variant voltage signal (<NUM>"); and
determining, by the processor, the axial position of the rotating target (<NUM>) based on a voltage variance between the first time variant voltage signal (<NUM>") and the second time variant voltage signal (<NUM>"), wherein the voltage variance with respect to time is relatively steady state for each of the first time variant voltage signal (<NUM>") and the second time variant voltage signal (<NUM>").