Patent Description:
A gas turbine engine includes an engine shaft that connects a turbine rotor to a load such as a fan, a propeller or a helicopter rotor. Various systems and method exist for preventing turbine rotor overspeed or shear of the engine shaft. While prior art systems and methods in this space have various benefits, there is still room in the art for improvement.

<CIT> discloses shaft shear detection through shaft oscillation.

<CIT> discloses a gas turbine engine health monitoring system with shaft-twist sensors.

According to an aspect of the present invention, a method is provided involving a turbine engine. During this method, data is received indicative of twist of a shaft of the turbine engine. The data is monitored over time to identity one or more reversal events while the turbine engine is operating, where each of the reversal events corresponds to a reversal in a value sign of the data. Shaft shear is identified in the shaft based on occurrence of N number of the reversal events.

According to another aspect of the present invention, another method is provided in accordance with claim <NUM>.

According to still another aspect of the present invention, an assembly is provided for a turbine engine. This assembly includes a shaft, a sensor and a controller. The sensor is configured to provide sensor data indicative of a parameter of the shaft. The parameter is or includes twist of the shaft and/or torque applied to the shaft. The controller is configured to monitor the sensor data over time to identify one or more reversal events while the turbine engine is operating. Each of the reversal events corresponds to a reversal in a value sign of the sensor data. The controller is also configured to identify shaft shear in the shaft based on occurrence of N number of the reversal events.

The following optional features may be applied to any of the above aspects.

The ringing may include a plurality of reversal events in the monitored data. Each of the reversal events may correspond to a reversal in a value sign of the monitored data.

The assembly may also include a fuel system. The fuel system may include a flow regulator. The controller may also be configured to signal the flow regulator to stop fuel flow when the shaft shear in the shaft is identified.

The assembly may also include a load and a turbine rotor. The shaft may couple the load to the turbine rotor.

The N number of the reversal events may be one of the reversal events.

The N number of the reversal events may be two or more of the reversal events.

The N number of the reversal events may change based on an operational parameter of the turbine engine.

The operational parameter may be or otherwise include rotational speed of the shaft.

The operational parameter may be or otherwise include power output of the turbine engine.

The identifying of the shaft shear in the shaft may also be based on the N number of the reversal events occurring within a predetermined period.

The predetermined period may change based on an operational parameter of the turbine engine.

The identifying of the shaft shear in the shaft may also be based on a magnitude of at least one of the N number of the reversal events.

The method may also include measuring the data using a sensor.

The method may also include shutting down the turbine engine when the shaft shear in the shaft is identified.

The occurrence of the N number of the reversal events may be indicative of ringing of the data.

The data may also be indicative of torque applied to the shaft.

The present disclosure includes systems and methods for identifying / detecting shaft shear in a gas turbine engine. For ease of description, the turbine engine is described below as a turbofan turbine engine. The present disclosure, however, is not limited to such an exemplary turbine engine. The turbine engine, for example, may alternatively be a turbojet turbine engine, a turboprop turbine engine, a turboshaft turbine engine, an auxiliary power unit, an industrial turbine engine for a power plant, or any other type of turbine engine in which identifying shaft shear would be useful.

<FIG> illustrates an aircraft propulsion system <NUM> with a turbofan turbine engine <NUM>. This turbine engine <NUM> extends along an axial centerline <NUM> of the turbine engine <NUM> between an upstream airflow inlet <NUM> and a downstream airflow exhaust <NUM>. The turbine engine <NUM> includes a fan section <NUM>, a compressor section <NUM>, a combustor section <NUM> and a turbine section <NUM>.

The fan section <NUM> includes a fan rotor <NUM>. The compressor section <NUM> includes a compressor rotor <NUM>. The turbine section <NUM> includes a high pressure turbine (HPT) rotor <NUM> and a low pressure turbine (LPT) rotor <NUM>, where the LPT rotor <NUM> is configured as a power turbine rotor. Each of these rotors <NUM>-<NUM> includes a plurality of rotor blades arranged circumferentially around and connected to one or more respective rotor disks.

The fan rotor <NUM> is connected to the LPT rotor <NUM> through a low speed shaft <NUM>. The compressor rotor <NUM> is connected to the HPT rotor <NUM> through a high speed shaft <NUM>. The low speed shaft <NUM> and the high speed shaft <NUM> of <FIG> are rotatable about the axial centerline <NUM>; e.g., a rotational axis. The low speed shaft <NUM> of <FIG> extends through a bore of the high speed shaft <NUM> between the fan rotor <NUM> and the LPT rotor <NUM>.

During operation, air enters the turbine engine <NUM> through the airflow inlet <NUM>. This air is directed through the fan section <NUM> and into a core flowpath <NUM> and a bypass flowpath <NUM>. The core flowpath <NUM> extends sequentially through the engine sections <NUM>-<NUM>; e.g., an engine core. The air within the core flowpath <NUM> may be referred to as "core air". The bypass flowpath <NUM> extends through a bypass duct, which bypasses the engine core. The air within the bypass flowpath <NUM> may be referred to as "bypass air".

The core air is compressed by the compressor rotor <NUM> and directed into a (e.g., annular) combustion chamber <NUM> of a (e.g., annular) combustor <NUM> in the combustor section <NUM>. Fuel is injected into the combustion chamber <NUM> by one or more fuel injectors <NUM>. This fuel is mixed with the compressed core air to provide a fuel-air mixture. The fuel-air mixture is ignited and combustion products thereof flow through and sequentially cause the HPT rotor <NUM> and the LPT rotor <NUM> to rotate. The rotation of the HPT rotor <NUM> drives rotation of the compressor rotor <NUM> and, thus, compression of air received from an inlet into the core flowpath <NUM>. The rotation of the LPT rotor <NUM> drives rotation of the fan rotor <NUM>, which propels bypass air through and out of the bypass flowpath <NUM>. The propulsion of the bypass air may account for a significant portion (e.g., a majority) of thrust generated by the turbine engine <NUM>.

<FIG> illustrates an assembly <NUM> for the turbine engine <NUM>. This turbine engine assembly <NUM> includes a fuel system <NUM>, a sensor system <NUM> and a controller <NUM>.

The fuel system <NUM> of <FIG> includes a fuel reservoir <NUM>, a fuel flow regulator <NUM> and the one or more fuel injectors <NUM>. The fuel reservoir <NUM> may be configured as or otherwise include a container; e.g., a tank, a cylinder, a pressure vessel, a bladder, etc. The fuel reservoir <NUM> is configured to contain and hold a quantity of fuel. The flow regulator <NUM> may be configured as or otherwise include a pump (e.g., a main fuel pump) and/or a valve (e.g., a shutoff valve, a flow control valve, etc.). This flow regulator <NUM> is configured to regulate a flow of the fuel from the fuel reservoir <NUM> to the fuel injectors <NUM>. The flow regulator <NUM> of <FIG>, for example, is configured to direct (e.g., pump) the fuel out of the fuel reservoir <NUM> for delivery to the fuel injectors <NUM>. The fuel system <NUM>, of course, may also include one or more additional components such as, but not limited to, a fuel filter, a heat exchanger (e.g., a heater) and/or an additional flow regulator (e.g., a boost pump, a bypass valve, a pressure regulating valve, etc.).

The sensor system <NUM> is configured to measure one or more engine parameters indicative of shaft twist and/or shaft torque. The term "shaft twist" may describe a condition where at least an axial portion or an entirety of a shaft (e.g., temporarily and/or resiliently) twists along its axial centerline / rotational axis in response, for example, to a torque input. The term "shaft torque" may describe torque transmitted through at least an axial portion or an entirety of a shaft. The sensor system <NUM> of <FIG> includes a sensor rotor <NUM> and a sensor probe <NUM>.

The sensor rotor <NUM> may be configured as a phonic wheel with inter-digited tooth pairs. The sensor rotor <NUM> of <FIG>, for example, includes a torque rotor <NUM> and a reference rotor <NUM>.

The torque rotor <NUM> is connected to (e.g., formed integral with, or fastened, welded, bonded and/or otherwise attached to) a shaft <NUM> of the turbine engine <NUM> at an axial first location <NUM>, which engine shaft <NUM> may be configured as any one of the engine shafts <NUM>, <NUM> in <FIG>. The torque rotor <NUM> of <FIG> projects radially out from the engine shaft <NUM> to an outer periphery. Referring to <FIG>, the torque rotor <NUM> includes one or more torque teeth <NUM> arranged circumferentially about the axial centerline <NUM> in a circular array at the torque rotor outer periphery.

Referring to <FIG>, the reference rotor <NUM> includes a rotor mount <NUM>, a rotor tube <NUM>, a rotor hub <NUM> and one or more reference teeth <NUM> (e.g., see <FIG>). The rotor mount <NUM> is connected to (e.g., formed integral with, or fastened, bonded and/or otherwise attached to) the engine shaft <NUM> at an axial second location <NUM>. This second location <NUM> is axially displaced from the first location <NUM> along the axial centerline <NUM> by a relatively large distance. The rotor tube <NUM> connects the rotor hub <NUM> to the rotor mount <NUM>. The rotor tube <NUM> of <FIG>, for example, is formed integral with and extends axially along the axial centerline <NUM> and the engine shaft <NUM> from the rotor mount <NUM> to the rotor hub <NUM>. An entirety of the rotor tube <NUM> is radially displaced outward from the engine shaft <NUM>. The rotor hub <NUM> is arranged axially next to (e.g., immediately adjacent, but not touching) a hub <NUM> of the torque rotor <NUM>. Referring to <FIG>, the reference teeth <NUM> are arranged circumferentially about the axial centerline <NUM> in a circular array at an outer periphery of the rotor hub <NUM>.

The torque teeth <NUM> of <FIG> are interspersed with the reference teeth <NUM>, and vice versa. Each of the reference teeth <NUM>, for example, is located within a respective gap circumferentially between a circumferentially adjacent pair of the torque teeth <NUM>. Similarly, each of the torque teeth <NUM> is located within a respective gap circumferentially between a circumferentially adjacent pair of the reference teeth <NUM>. With this arrangement, the torque teeth <NUM> are configured to circumferentially move (e.g., shift) relative to and without impediment (e.g., blockage, resistance, etc.) from the reference teeth <NUM> during operation of the turbine engine <NUM>. For example, during a first condition (e.g., where the engine shaft <NUM> is unloaded or subject to a relatively small torque) of <FIG>, each of the reference teeth <NUM> is spaced from a respective torque tooth <NUM> by a circumferential first distance <NUM>. During a second condition (e.g., where the engine shaft <NUM> is subject to a relatively high torque) of <FIG>, each of the reference teeth <NUM> is spaced from a respective torque tooth <NUM> by a circumferential second distance <NUM> that is different (e.g., greater or less) than the first distance <NUM>.

Referring to <FIG>, the sensor probe <NUM> may be configured as a magnetic pickup probe. The sensor probe <NUM> is configured to measure movement (e.g., shifts) between the torque teeth <NUM> and the reference teeth <NUM> during operation of the turbine engine <NUM>. The sensor probe <NUM>, for example, may be configured to output sensor data (e.g., a voltage signal) indicative of when each of the teeth <NUM>, <NUM> passes a tip of the sensor probe <NUM>. For example, the sensor probe <NUM> may generate / output an electric pulse each time a tip of one of the teeth <NUM>, <NUM> passes the sensor probe tip. This sensor data may then be correlated to map or otherwise determine how the tips of adjacent pairs of the teeth <NUM> and <NUM> are moving relative to one another by the controller <NUM>.

Referring to <FIG>, the controller <NUM> is in signal communication with one or more of the turbine engine components <NUM> and <NUM>. The controller <NUM> of <FIG>, for example, may be hardwired to and/or wirelessly coupled with the turbine engine components <NUM> and <NUM>.

The controller <NUM> may be configured as an onboard engine controller; e.g., an electronic engine controller (EEC), an electronic control unit (ECU), a full-authority digital engine controller (FADEC), etc. The controller <NUM> may be implemented with a combination of hardware and software. The hardware may include memory <NUM> and at least one processing device <NUM>, which processing device <NUM> may include one or more single-core and/or multicore processors. The hardware may also or alternatively include analog and/or digital circuitry other than that described above.

The memory <NUM> is configured to store software (e.g., program instructions) for execution by the processing device <NUM>, which software execution may control and/or facilitate performance of one or more operations such as those described in the methods below. The memory <NUM> may be a non-transitory computer readable medium. For example, the memory <NUM> may be configured as or include a volatile memory and/or a nonvolatile memory. Examples of a volatile memory may include a random access memory (RAM) such as a dynamic random access memory (DRAM), a static random access memory (SRAM), a synchronous dynamic random access memory (SDRAM), a video random access memory (VRAM), etc. Examples of a nonvolatile memory may include a read only memory (ROM), an electrically erasable programmable read-only memory (EEPROM), a computer hard drive, etc..

<FIG> is a flow diagram of a method <NUM> involving (e.g., monitoring and/or controlling) a turbine engine. For ease of description, this method <NUM> is described below with reference to the turbine engine <NUM> of <FIG> and the turbine engine assembly <NUM> of <FIG>. The method <NUM>, however, may alternatively be performed for other turbine engine configurations and with other turbine engine assemblies.

In step <NUM>, the sensor system <NUM> provides sensor data to the controller <NUM>. In particular, the sensor system <NUM> of <FIG> measures the one or more engine parameters indicative of the twist in the engine shaft <NUM> (the shaft twist) and/or the torque applied to the engine shaft <NUM> (the shaft torque). The sensor probe <NUM> of <FIG> and <FIG>, for example, may generate and/or output an electric pulse each time the tip of one of the sensor rotor teeth <NUM>, <NUM> passes (e.g., is in close radial proximity with) the tip of the sensor probe <NUM>. These electrical pulses may be communicated from the sensor system <NUM> to the controller <NUM> as the sensor data. This sensor data is indicative of the shaft twist and/or the shaft torque as described below in further detail.

In step <NUM>, the controller <NUM> receives the sensor data from the sensor system <NUM>.

In step <NUM>, the controller <NUM> processes the received sensor data to determine shaft twist data and/or shaft torque data. The controller <NUM> of <FIG> and <FIG>, for example, processes the sensor data to identify when each of the sensor rotor teeth <NUM>, <NUM> passes the sensor probe <NUM>. <FIG> includes a graphic example of the sensor data communicated from the sensor system <NUM> to the controller <NUM> as a voltage wave - a sensor signal. This voltage wave includes a plurality of (e.g., high, top) peaks, where each of the peaks corresponds with the tip of one of the rotor sensor rotor teeth <NUM>, <NUM> passing (e.g., directly radially below) the tip of the sensor probe <NUM>. <FIG> illustrates how each set of the rotor teeth (e.g., one of the torque teeth <NUM> and an adjacent one of the reference teeth <NUM>) passing the sensor probe <NUM> may generate a unique electrical signal wave. Using this correlation, the controller <NUM> may identify points where the signal wave crosses a baseline (e.g., a zero voltage line). Each time the signal wave crosses the baseline, the controller <NUM> may start or stop a respective counter. The time between the start and the stop of the respective counter may represent temporal duration (e.g., period of time) between a respective set of the sensor rotor teeth <NUM>, <NUM> passing the sensor probe <NUM>.

<FIG> illustrates how the time counters may change relative to torque applied to the engine shaft <NUM>. Each of the time counters includes a mark counter (labeled as "mark") and a space counter (labeled as "space"). The term "mark counter" may describe a temporal duration between tips of the rotor teeth <NUM> and <NUM> in a common set (e.g., the same set) passing the sensor probe <NUM>. The term "space counter" may describe a temporal duration between a tip of a last one of the rotor teeth (e.g., <NUM>) in a set and a tip of a first one of the rotor teeth (e.g., <NUM>) in an adjacent (e.g., rotationally next) set passing the sensor probe <NUM>. Referring to <FIG>, when a relatively low torque (or no torque) is applied to the engine shaft <NUM>, the mark counter may be relatively large and the space counter may be relatively small. Thus, a circumferential distance between tips of the rotor teeth <NUM> and <NUM> in a common set is relatively large (or small). Referring to <FIG>, when a relatively high torque is applied to the engine shaft <NUM>, the mark counter may be relatively small and the space counter may be relatively large. Thus, the circumferential distance between tips of the rotor teeth <NUM> and <NUM> in a common set is relatively small (or large). The controller <NUM> may correlate this change in the mark counter, the change in the space counter and/or the change in the circumferential distance between tips to determine the twist of the engine shaft <NUM> (shaft twist) and/or the torque applied to the engine shaft <NUM> (shaft torque).

Referring to <FIG>, during normal turbine engine operation, the shaft twist and/or the shaft torque (see signal <NUM>) may slightly fluctuate up and down due to, for example, tolerance, vibrations, environmental condition, etc. During this normal turbine engine operation, however, the shaft twist and/or the shaft torque may remain positive. In other words, a value of the shaft twist and/or a value of the shaft torque may not dip below a zero (<NUM>) value since the engine shaft <NUM> of <FIG> transmits a positive torque from an input <NUM> (e.g., at least one of the turbine rotors <NUM>, <NUM> of <FIG>) to a load <NUM> (e.g., one of the rotors <NUM>, <NUM> of <FIG>).

Referring to <FIG>, in a case of a shaft shear event (e.g., fracture of the engine shaft <NUM> between the input <NUM> and the load <NUM>), the torque transmitted by the engine shaft <NUM> may suddenly drop to a zero (<NUM>) value and the engine shaft <NUM> may free spin since there is no longer a (e.g., significant, besides rotational bearing drag, windage, etc.) load to counteract the torque applied by the input <NUM>. However, due to the rapid drop in transmitted torque, the engine shaft <NUM> may be subject to ringing. More particularly, as the shaft twist drops to the zero value, momentum of the untwisting may cause the engine shaft <NUM> to twist partially in a negative value direction. Similarly, as the shaft torque drops to the zero value, the momentum of the untwisting may cause the engine shaft <NUM> to be subject to a negative value torque. This ringing effect is shown in <FIG> where the value of the shaft twist and/or the value of the shaft torque (see signal <NUM>) fluctuates (e.g., rings, oscillates, etc.) above and below a zero value baseline. When the shaft twist value / the shaft torque value is above the zero value baseline, that value has a positive (+) value sign; e.g., the value is a mathematical positive number. When the shaft twist value and/or the shaft torque value is below the zero value baseline, that value has a negative (-) value sign; e.g., the value is a mathematical negative number.

In step <NUM>, the controller <NUM> monitors the shaft twist data and/or the shaft torque data to identify one or more reversal events. The term "reversal event" may describe a reversal in the value sign of the data from one point in time to another point in time. For example, referring to <FIG>, a first reversal event occurs in a first period of time <NUM>. In this first period of time <NUM>, the value sign of the monitored shaft twist data and/or the monitored shaft torque data changes from a positive value sign to a negative value sign. By contrast a second (e.g., opposite) reversal event occurs in a second period of time <NUM>. In this second period of time <NUM>, the value sign of the monitored shaft twist data and/or the monitored shaft torque data changes from a negative value sign to a positive value sign.

In step <NUM>, the controller <NUM> identifies shaft shear in the engine shaft <NUM> based on occurrence of N-number of the reversal events. In other words, where the controller <NUM> identifies N-number of the reversal events have occurred (e.g., ringing of the monitored data about the zero value baseline) in a predetermined period (e.g., period of time), the controller <NUM> will determine the engine shaft <NUM> has sheared. The N-number of reversal events may be a single event (e.g., N = <NUM>), or the N-number of events may be multiple events (e.g., N ≥ <NUM>). The N-number of reversal events may be selected in order to reduce (e.g., minimize) duration / time before identifying shaft shear, while at the same time reducing (e.g., minimizing) likelihood of or preventing false positives.

The value of N may be constant. Alternatively, the value of N may change based on one or more operational parameters of the turbine engine <NUM>. Examples of these operational parameters may include, but are not limited to, rotational speed of the engine shaft <NUM> and power output (e.g., thrust output, torque output, etc.) of the turbine engine <NUM>. For example, where the rotational speed of the engine shaft <NUM> is relatively slow and/or the power output of the turbine engine <NUM> is relatively low, there may be more time to gather data before identifying shaft shear. In such conditions therefore the value of N may be relatively high. However, where the rotational speed of the engine shaft <NUM> is relatively fast and/or the power output of the turbine engine <NUM> is relatively high, there may be less time to gather data before identifying shaft shear. In such conditions therefore the value of N may be relatively low.

The predetermined period for identifying the reversal events may be constant. Alternatively, the predetermined period for identifying the reversal events may be varied based on, for example, the one or more operational parameters of the turbine engine <NUM>. For example, where the rotational speed of the engine shaft <NUM> is relatively slow and/or the power output of the turbine engine <NUM> is relatively low, the predetermined period for identifying the reversal events may be relatively long / large. However, where the rotational speed of the engine shaft <NUM> is relatively fast and/or the power output of the turbine engine <NUM> is relatively high, the predetermined period for identifying the reversal events may be relatively short / small.

In some embodiments, the reversal event may be of any magnitude. In other embodiments, the reversal event may only be counted where a magnitude <NUM> (see <FIG>) between a maximum positive value and a maximum negative value is greater than a predetermined threshold.

In step <NUM>, the controller <NUM> shuts down the turbine engine <NUM> when the shaft shear in the engine shaft <NUM> is identified. The controller <NUM> of <FIG>, for example, may signal the flow regulator <NUM> (e.g., the pump and/or the valve) to stop a flow of fuel from the fuel reservoir <NUM> to the fuel injectors <NUM>. In this manner, the controller <NUM> may prevent an overspeed event of the engine shaft <NUM> and the input <NUM> (e.g., one of the turbine rotors <NUM>, <NUM>).

In some embodiments, the predetermined period for identifying the reversal events is controlled by providing a continuously updated buffer memory. For example, the controller <NUM> may monitor the shaft twist data and/or the shaft torque data stored in the buffer memory. As new values for the shaft twist data and/or the shaft torque data are determined and entered, the oldest values are deleted. Thus, the predetermined period may be related to a number of data values entered opposed to a specific temporal duration.

The method <NUM> is described above with respect to the turbofan turbine engine <NUM> of <FIG>. However, the method <NUM> may also be utilized for other types of gas turbine engines as described above. For example, the method <NUM> may be utilized for a turboprop turbine engine where, for example, the input <NUM> is a turbine rotor and the load <NUM> is a compressor rotor or a propeller rotor. In another example, the method <NUM> may be utilized for a turboshaft turbine engine where, for example, the input <NUM> is a turbine rotor and the load <NUM> is a compressor rotor or a helicopter rotor. In still another example, the method <NUM> may be utilized for an auxiliary power unit or an industrial turbine engine where, for example, the input <NUM> is a turbine rotor and the load <NUM> is a compressor rotor or a generator. The present disclosure, of course, is not limited to the foregoing exemplary arrangements.

Claim 1:
A method (<NUM>) involving a turbine engine (<NUM>), comprising:
(<NUM>) receiving data indicative of twist of a shaft (<NUM>) of the turbine engine (<NUM>);
(<NUM>) monitoring the data over time to identity one or more reversal events while the turbine engine (<NUM>) is operating, wherein each of the reversal events corresponds to a reversal in a value sign of the data; and
(<NUM>) identifying shaft shear in the shaft (<NUM>) based on occurrence of N number of the reversal events.