Abstract: A perforating gun assembly used to form perforations in a wellbore includes a charge carrier having a longitudinal axis, and multiple groups of shaped charges that are disposed on the charge carrier. Two or more of the shaped charges within each group are arranged to generate jets oriented substantially along respective axes that converge towards one another. Also, two or more of the groups of shaped charges overlap one another in a longitudinal direction of the charge carrier.

Abstract: A one trip system for perforating and fracking multiple intervals uses a releasable barrier. The barrier can be an inflatable. A pressure booster system is associated with the BHA so that the existing hydrostatic pressure is boosted when the gun or portions thereof are fired. After firing in one interval, the BHA is raised and the barrier is redeployed and the pattern repeats. Instruments allow sensing the conditions in the interval for optimal placement of the gun therein and for monitoring flow, pressure and formation conditions during the fracturing. Circulation between gun firings cleans up the hole. If run in on wireline a water saving tool can be associated with the BHA to rapidly position it where desired. A multitude of perforation charges mounted in the BHA can be selectively fired by selected corresponding detonator based on a predetermined sequence or surface telemetry command.

Abstract: A control method for controlling the intrusion of dissolved solids into a fresh water aquifer located proximate to an ocean includes the steps of: a) frequently measuring the TDS content at a control location, such frequent measuring of TDS content at the control location being conducted at least about once per calendar quarter, the frequent measuring of TDS content at the control location providing a plurality of control location TDS content values; b) comparing one or more of the plurality of control location TDS content values to a predetermined TDS control range; and c) adjusting the TDS content at the control location to within the predetermined TDS control range by one or more control measures.

Abstract: Systems and methods for determining proper phase rotation in a linear motor where the phase rotations associated with power and return strokes are initially unknown. Power having an initial phase rotation is provided to a linear motor until the motor's mover reaches the end of the stroke, and then power to the motor is discontinued. While power is discontinued, the mover is monitored to detect its movement. if the mover moves without power, the mover was at the top of the stroke, so the initial phase rotation is associated with an upward stroke of the mover, and a second phase rotation which is opposite the initial phase rotation is associated with a downward stroke of the mover. Otherwise, the initial phase rotation is associated with the downward stroke of the mover and the second, opposite phase rotation is associated with the upward stroke of the mover.

Abstract: A method of extracting hydrocarbons from a subterranean formation comprises introducing a solution comprising a silicon-containing compound into the subterranean formation. The silicon-containing compound may comprise a terminal group comprising one of an alkanoate group, a fluoroalkanoate group, and a perfluoroalkanoate group, and one or more of an alkoxy group and a chlorine atom bonded to the silicon atom. The method comprises attaching the silicon-containing compound to one or more of formation surfaces of the subterranean formation to form an oleophilic surface on the one or more of the formation surfaces and the surfaces of proppant particles.

Abstract: Higher order simulation of hydrocarbon flows associated with complex fractures produced in the hydraulic fracturing process in a well system may be used to obtain high fidelity results while minimizing a cost of computation. The higher order simulation of hydrocarbon flows may provide efficient and stable simulation algorithms that avoid any artificial boundary treatment inconsistent with the governing equations, while maintaining a uniform order of accuracy. In particular, a re-normalization technique implements higher-order finite difference/finite volume discretization near the boundary of the complex fractures. The simulation of hydrocarbon flows may be used to determine a production activity for the well system.

Abstract: There is described subsea apparatus and a method for processing fluid from a well. In an embodiment, a pipeline (6) may be arranged to carry the multiphase fluid containing liquid and gas from the well. An outlet (10) extending through a wall of the pipeline may let gas out of the pipeline from said region and through the outlet to separate said gas and liquid. A compressor may be connected to the outlet to compress the separated gas. The separated liquid and the compressed gas may be combined. Separated liquid may be conveyed along a sloping portion of the pipe to a low point in the seabed terrain, and may be conveyed to a pump for boosting the flow of liquid. The pump may be located in an excavated hole or glory hole below the seabed.

Abstract: A well tool includes a body defining an enclosed fluid passage. A bipolar electrode is provided in the well tool, changeable between a first, energized state, and a second, different state. The bipolar electrode in the first state produces an ion depletion zone that presents a flow restriction to saline fluids in the fluid passage.

Abstract: A system for reducing salt water intrusion into a fresh water aquifer includes: a) generating means for removing brackish water from the aquifer via an brackish water extraction well at a first distance from the ocean; b) removal means for introducing the removed brackish water into a desalination system to generate a first stream of water with a first salt content and a second stream of water having a second salt content, the first salt content being less than the second salt content and less than the salt content of the removed brackish water; and c) introduction means for introducing at least a portion of the first stream of water into the aquifer via a barrier well at a second distance from the ocean, the second distance being greater than the first distance.

Abstract: A method for selecting drilling parameters for drilling a borehole penetrating the earth with a drill string includes: varying a frequency of an excitation force applied to the drill string using an excitation device controlled by a drill string controller and measuring vibration-related amplitudes of the drill string due to the applied excitation force using a vibration sensor to provide amplitude measurements. The method further includes determining one or more modal properties comprising one or more eigenfrequencies of the drill string using the amplitude measurements and selecting drilling parameters that apply an excitation force at a frequency that avoids a selected range of frequencies that bound the one or more eigenfrequencies.

Abstract: A process of monitoring the intervention of, an instrumented rod with at least one sensor for measuring a strain field along the rod, into the wall and measuring the strain field along the rod in a plurality of given shapes of evolution of the rod during the intervention. The process calculates a simulated strain field for each given shape of the rod, based on at least one first model taking account of the predetermined geometry of the well and the first model being able to determine a local buckling of the rod in the well. Further, the process compares the measured strain field and the simulated strain field in each given shape of evolution of the rod.

Abstract: A housing defines a through passage along its length and is configured to support a group of electrical isolators surrounding the through passage to form an electrically isolating break in a drill string such that each isolator of the group of isolators is subject to no more than a compressive force responsive to extension and retraction of the drill string. The housing defines a housing cavity to receive an electronics package having a signal port and is configured for electrical connection of the signal port across the electrically isolating break. A housing lid can cooperate with a main housing body to define elongated slots for purposes of enhancing the emanation of a locating signal. A housing arrangement can support electrical connections from an electronics package to bridge an electrically isolating gap.

Abstract: A boring tool that is moved by a drill string to form an underground bore. A transmitter transmits a time varying dipole field as a homing field from the boring tool. A pitch sensor detects a pitch orientation of the boring tool. A homing receiver is positionable at a target location for detecting the homing field to produce a set of flux measurements. A processing arrangement uses the pitch orientation and flux measurements with a determined length of the drill string to determine a vertical homing command for use in controlling depth in directing the boring tool to the target location such that the vertical homing command is generated with a particular accuracy at a given range between the transmitter and the homing receiver and which would otherwise be generated with the particular accuracy for a standard range, different from the particular range. An associated system and method are described.

Abstract: This application relates to methods and apparatus for monitoring hydraulic fracturing in well formation and fracture characterization using distributed acoustic sensing (DAS). The method involves interrogating an optic fiber arranged down the path of a borehole to provide a distributed acoustic sensor and also monitoring flow properties of fracturing liquid pumped into the well where the acoustic data from the distributed acoustic sensor is processed together with the flow properties data to provide an indication of at least one fracture characteristic.

Abstract: A composition for stabilizing dispersed particles in an ionically charged solution is disclosed. The composition includes a carbonaceous substrate, the carbonaceous substrate operable to undergo a grafting-to approach for functionalization. The composition also includes a covalently bound stabilizing polymer, the covalently bound stabilizing polymer operable to be prepared as a diazonium salt for grafting to the carbonaceous substrate and a plurality of positively and negatively charged subgroups, the plurality of positively and negatively charged subgroups positioned within the covalently bound stabilizing polymer, where the plurality of positively and negatively charged subgroups are operable to stabilize the dispersed particles amongst positively and negatively charged ions within the ionically charged solution.

Abstract: A downhole apparatus for measuring drilling fluid characteristics. The downhole apparatus may comprise one or more sensors located within a housing. The sensors may include one or more of an imaging device, a resistivity/conductivity sensor, a temperature sensor, a pressure sensor, a flowmeter and a fluid density sensor. The downhole apparatus may also include a controller for receiving measurements and/or determining optimal electromagnetic telemetry transmission settings. The downhole apparatus may also comprise a transmitter for transmitting the measurements and/or the optimal electromagnetic transmission settings. The downhole apparatus may be operated to determine optimal transmission settings for an electromagnetic telemetry system. Optimal transmission settings may include settings relating to one or more of frequency, amplitude, voltage, current, and power.

Abstract: An inspection system to measure the condition of at least the wall of a ground opening, such as a borehole opening, an excavation, and a slurry wall, the inspection system comprising a head unit configured to be lowered into an associated borehole and having a lowering mount configured to be operably and selectively joined to an associated lowering unit to facilitate the lowering of the head unit into the associated borehole during a data collection phase, the data collection phase including at least one of a lowering phase wherein the head unit is lowered in the associated borehole toward an associated bottom extent of the borehole by the associated lowering unit and a raising phase wherein the head unit is raised in the associated borehole away from the associated bottom extent, at least one set of test data being collected concerning one or more physical characteristics of the associated borehole during the data collection phase, the head unit comprising an internal measurement system and a sensor arrangem

Abstract: Apparatus, computer readable medium, and program code for identifying rock properties in real-time during drilling, are provided. An example of an embodiment of such an apparatus includes a downhole sensor subassembly connected between a drill bit and a drill string, acoustic sensors operably coupled to a downhole data interface, and a surface computer operably coupled to the downhole data interface.

Abstract: Disclosed is a monitoring probe for observing groundwater, which is put into an observation well for observing the groundwater to indicate a position of a fresh water-salt water interface of the groundwater. According to the present invention, both ends of a probe body are separated from an inner circumference of an observation well by a catch preventing portion having a convex curved portion or a dumbbell-shaped portion, so that the probe body can be smoothly moved up and down without being caught by a ground-water inlet port of the observation well, thus providing an exact position of a fresh water-salt water interface.

Abstract: Controlling an output of a mining system. The control includes receiving, at a processor, a first signal associated with a position of the shearer, determining, using the processor, the position of the shearer based on the first signal, receiving, at the processor, a second signal associated with a load of a conveyor, and determining, using the processor, the load of the conveyor based on the second signal. The method further includes determining, using the processor, an output of the mining system based on the position of the shearer and the load of the conveyor and controlling a speed of the shearer based on the output of the mining system.

Abstract: A method for initiating a remote operation mode of a work machine, the method including providing the work machine with a work machine-specific safety key; receiving, at a remote control station, a notification from the work machine in response to initiating the remote operation mode of the work machine by said safety key; acknowledging the work machine as being included in a safety system of the remote control station; and configuring the remote control station to start the remote operation mode of the work machine.

Abstract: The present application relates to a system for supporting a roof of a portion of a mine. The system includes a first plurality of stabilizing members disposed above the roof at a first elevation. The first plurality of stabilizing members originate from a first common location and terminate at a second elevation that is higher than the first elevation. The system further includes a second plurality of stabilizing members disposed above the roof and the first plurality of stabilizing members at a third elevation. The second plurality of stabilizing members originate from a second common location and terminate at a fourth elevation that is higher than the third elevation. The second plurality of stabilizing members are disposed generally perpendicular to the first plurality of stabilizing members.

Abstract: A vertically and laterally adjustable frame for a mine ventilation structure having two or more pairs of adjustable height support columns, and a plurality of adjustable length support beams, each support beam mounted to and spanning between a pair of the support columns. A mine overcast and a method of assembling an overcast in an intersection within a mine are also provided, with the overcast including a vertically and laterally adjustable frame, and a plurality of side and ceiling panels mounted to the frame.

Abstract: A water-preserved-mining roof-contacted filling method for controlling fissure of overlying strata and surface subsidence. The method is suitable for controlling fissure of overlying strata and surface subsidence in water-preserved-mining of a mine. A sensor is mounted at the top of a goaf of a filling working face where water-preserved-mining is carried out, and a filling body that is filled is monitored through a stress display device so as to determine whether the goaf is roof-contacted or separated. When the filling body is separated after roof-contacted, the goaf is filled for the second time so as to be roof-contacted fully, so that the purpose of controlling fissure of overlying strata and surface subsidence can be achieved, and protective mining of water resources of the mine can be realized at last. The method is simple and targeted, and has strong operability and high efficiency.

Abstract: A hybrid elastomer/metal on metal motor for a helical gear device includes a rotor and stator comprising a hydraulic motor that produces work when a working fluid is pumped therethrough. The improvement involves the stator being, for part of its length, a conventional or even wall stator, using an elastomer to form a seal against the moving rotor. The stator's remaining length comprises a profiled rigid surface that forms a seal directly with the moving rotor. This gives the motor the high efficiency of the elastomer sealing against the rotor, and simultaneously provides a backup of the stator' s rigid section allowing continued motor operation at reduced efficiency, if the elastomer part failed in service. The invention also includes combinations of a regular disk stack with a rubber lining, a rigid material disk stack (or unitized element) and a circular rigid sleeve which react to rotor sideloading while permitting proper rotor orbiting.

Abstract: A method of localized repair to a damaged thermal barrier, the method including subjecting a part coated in a damaged thermal barrier to electrophoresis treatment, the part being made of an electrically conductive material, the damaged thermal barrier including a ceramic material and presenting at least one damaged zone that is to be repaired, the part being present in an electrolyte including a suspension of particles in a liquid medium, the ceramic coating being deposited by electrophoresis in the damaged zone in order to obtain a repaired thermal barrier for use at temperatures higher than or equal to 1000° C., the particles being made of a material different from the ceramic material present in the damaged thermal barrier.

Abstract: A rotor disk is provided. The rotor disk may comprise a disk lug and a trench. The disk lug may be fixed to a distal surface of the rotor disk. The trench may be disposed on a surface of the disk lug. The trench may extend radially inwards from a distal surface of the disk lug. The trench may be configured to at least partially define a flow path by which cooling air may reach a distal surface of the disk lug in order to provide disk lug cooling.

Abstract: A method for forming a hole in a ceramic matrix composite (CMC) component may be provided. A sacrificial fiber having an environmental barrier coating on an outer surface thereof may be inserted into a porous ceramic preform that includes ceramic fibers. The ceramic preform may be formed into a ceramic matrix composite body. The sacrificial fiber may be removed from the ceramic matrix composite body, the environmental barrier coating of the sacrificial fiber defining an opening in the ceramic matrix composite body. A ceramic matrix composite component may be provided. The ceramic matrix composite component may include an environmental barrier coating of a sacrificial fiber, where the environmental barrier coating forms a lining of a hole passing partly or entirely through a thickness of the ceramic matrix composite body.

Abstract: A component for a turbine engine includes a substrate that includes a first surface, and an insert coupled to the substrate proximate the substrate first surface. The component also includes a channel. The channel is defined by a first channel wall formed in the substrate and a second channel wall formed by at least one coating disposed on the substrate first surface. The component further includes an inlet opening defined in flow communication with the channel. The inlet opening is defined by a first inlet wall formed in the substrate and a second inlet wall defined by the insert.

Abstract: An airfoil may be provided that includes a CMC body and a support piece. The CMC body has an inner surface that defines a chamber within the CMC body. The support piece may be positioned within the chamber of the CMC body. The support piece comprises a channel in a surface of the support piece, the surface being in contact with the inner surface of the CMC body. The channel and the inner surface of the CMC body define a passageway for a cooling fluid. The passageway may wind about the circumference of the CMC body and extend along the span of the airfoil. Outlets may be positioned through the CMC body allowing fluid communication between the passageway and the outer surface of the CMC body.

Abstract: The present disclosure provides systems for preventing improper installation of a damper seal. In various embodiments, an airfoil assembly may comprise a platform, an airfoil extending from the platform, and a platform tab. The airfoil may comprise a gaspath face and a non-gaspath face. The non-gaspath face may at least partially define a cavity. The airfoil may comprise a pressure side and a suction side. The platform tab may be located adjacent to the suction side of the airfoil. The platform tab may extend from the platform in the opposite direction as the airfoil and may be configured to prevent a damper seal tab from being inserted radially inwards of the platform tab.

Abstract: A method to form a hole in a ceramic matrix composite component may be provided. A monolithic rod may be inserted into a porous ceramic preform. The ceramic preform may be formed into a ceramic matrix composite body that includes the monolithic rod. A portion of the monolithic rod may be removed, leaving a remaining portion in the ceramic matrix composite body. The remaining portion may include walls that define the opening in the ceramic matrix composite body. Alternatively or in addition, a ceramic matrix composite component may be provided. The ceramic matrix composite component may comprise a ceramic matrix composite body that includes a portion of a monolithic rod. The portion of the monolithic rod forms a lining around a hole passing partly or entirely through a length of the monolithic rod.

Abstract: A coated component with a coating applied by Electron Beam Physical Vapor Deposition (EB-PVD) includes at least one Non Line of Sight (NLOS) area and at least one Line of Sight (LOS) area, a coating on the workpiece defines a ratio greater than about 10% NLOS/LOS.

Abstract: A method of manufacturing an internally cooled blisk by additive manufacturing processes to provide weight reduction and power-to-weight ratio improvement, leading to improved efficiency, a decrease in fuel burn and lifecycle costs in an engine employing the internally cooled blisk. The method of manufacturing including defining a configuration for the internally cooled blisk, the configuration comprising a disk, an annular array of angularly spaced blades extending about a periphery of the disk and one or more internal cooling features defined within the internally cooled blisk. The method further including the step of programming the configuration into an additive manufacturing system. A powder is deposited into a chamber and an energy source is applied to the deposited powder to consolidate the powder into a cross-sectional shape corresponding to the defined configuration. Additionally provided is an internally cooled blisk.

Abstract: A fiber preform for a hollow turbine engine vane, and a method of fabricating such a hollow vane are provided. The preform includes a first fiber structure including a main longitudinal portion for forming a pressure side wall of an airfoil; a second fiber structure including a main longitudinal portion for forming a suction side wall of the airfoil; each of the first and second fiber structures includes a first interlinking zone extending along the front edge of its main longitudinal portion, which first zones are integral with each other and form a first interlinking portion, and a second interlinking zone extending along the rear edge of its main longitudinal portion, the second zones being integral with each other and forming a second interlinking portion. The main longitudinal portions of the first and second fiber structures are dissociated so as to leave a gap between the main longitudinal portions forming an airfoil hollow.

Abstract: The present disclosure relates generally to a system and method for applying a metallic coating. A first metallic coating may be applied to a portion of a total surface of a part and a second metallic coating may be applied to substantially the total surface. The metallic coating may be applied to a vane cluster for use in a turbomachine.

Abstract: The invention proposes a guide arm for guiding at least one element having an elongated shape (20), corresponding to a set of cables and/or pipes. The arm comprises an inner cavity (62) opening on the outside of the arm at each of the ends thereof, and in which the elements having an elongated shape can extend. According to the invention, this structure more particularly comprises: a frame (8) comprising a beam (18) linked to means (30, 36, 44) for holding the elements having an elongated shape on the outside and along the beam, and a cover (54) of which the walls (56, 58) cover the holding means of the frame, and are engaged with the beam, in such a way as to form the inner cavity in which the elements having and elongated shape extend, shock-absorbing means (68) being arranged between the means (30, 36, 44) for holding the elements having an elongated shape (20), and the longitudinal walls (56, 58), in such a way as to reduce and damp the movements of the means for holding in the cavity (62).

Abstract: A gas turbine engine assembly adapted to separate a high pressure zone from a low pressure zone includes a seal assembly configured to block gasses from passing through the interface of two adjacent components. The seal assembly includes a rod.

Abstract: A seal and bearing assembly of a gas turbine engine having an engine case with a cooling fluid nozzle located between a bearing outer ring and ring segments, and a rotary shaft for rotation in the engine case around a main axis, the seal and bearing assembly can be assembled by positioning the engine case and the rotary shaft in axial alignment, and axially moving the engine case relative to the rotary shaft including moving the bearing outer ring across the axial location of the runner portion and into an assembled condition. The rotary shaft having mounted thereon a bearing inner ring and a runner assembly having a runner portion, a sleeve portion being concentric and radially internal to the runner portion, and a cooling fluid passage having a radial segment leading from an outgoing segment to a returning segment extending in a direction leading back toward the bearing inner ring.

Abstract: An assembly for use in a gas turbine engine is disclosed. The assembly includes a first component arranged adjacent to a second component to form a gap therebetween and a pressure activated seal that resists flow through the gap.

Abstract: A turbine assembly can include a turbine wheel, a shroud component, a turbine housing and a seal that includes a wall and a lower lip that that extends radially outwardly from the wall where the seal is disposed, at least in part, between an outer surface of the shroud component and an inner surface of the turbine housing and where the lower lip is in contact with the turbine housing.

Abstract: A platform trailing edge seal for a turbomachine airfoil (e.g., a blade or vane) assembly includes a body configured to extend into an aft portion of a mateface gap defined between a circumferentially adjacent pair of turbomachine airfoil platforms to minimize flow from entering a blade-vane cavity through the aft portion of the mateface gap.

Abstract: A cartridge for a ceramic matrix composite (CMC) seal segment of a segmented turbine shroud of a gas turbine engine is provided. The cartridge comprises a carrier segment and a CMC seal segment. A surface of the carrier segment and a surface of the CMC seal segment form a mating region proximate the entire perimeter of the CMC seal segment. The carrier segment surface may comprise a channel, and a compressible mating element may be disposed within the channel. Air may be supplied to a cavity, formed by the carrier and CMC seal segment, and the mating region.

Abstract: A shroud for radially encasing a turbine in a gas turbine engine is provided. The shroud comprises a carrier which defines a pin-receiving carrier bore, and a ceramic matrix composite (CMC) seal segment comprising an arcuate flange with a surface facing the turbine and a part that defines a pin-receiving seal segment bore. The seal segment bore is radially spaced from the arcuate flange by a spacing flange which extends radially outward from the arcuate flange to effect receipt within the seal segment bore of an elongated pin. The elongated pin extends through the carrier bore and the seal segment bore, and the elongated pin has a lateral cross-sectional dimension of at least three-eighths of an inch.

Abstract: A ceramic matrix composite (CMC) seal segment for use in a segmented turbine shroud for radially encasing a turbine in a gas turbine engine. The CMC seal segment comprises an arcuate flange having a surface facing the turbine and a portion defining a bore for receiving an elongated pin, with the bore having a length that is at least 70% of the length of the elongated pin received therein. The CMC seal segment is carried by the carrier by at least one of the elongated pins being received within the bore. The CMC seal segment portion defining a pin-receiving bore is radially spaced from the arcuate flange by a spacing flange extending radially outward from the arcuate flange.

Abstract: A method and system for use with actuation system to control a plurality of vanes disposed within a turbine engine, wherein a vane position sensor provides a vane position signal corresponding to a vane position of the plurality of vanes, the actuation system includes a plurality of motors engaged in response to the vane position signal, and a differential gearbox having a plurality of inputs operatively coupled to the plurality of motors and an output operatively coupled to the plurality of vanes, wherein an output speed of the output is a sum of a plurality of input speeds of the plurality of inputs.

Abstract: The invention relates to a turbine engine compressor, in particular of an aeroplane turboprop or turbofan, comprising a stator featuring an annular casing and at least one annular row of variable-pitch vanes, wherein each vane comprises a radially external end having a pivot mounted in an orifice in the casing and connected by a linking member to an control ring (38) capable of pivoting axially in relation to the casing, wherein said linking member comprises a first end fixed to the pivot of the vane and a second end having a pin inserted in a hole (52, 58) in the control ring (38), characterised in that one (58) at least of the holes (52, 58) in the control ring (38) serving for insertion of the pins of the linking members, is oblong in shape and extends in the circumferential direction in order to allow movement of the pin in said oblong hole (58), during rotation of the control ring (38).

Abstract: A pressure probe includes a non-deflecting airfoil, a sensing feature, and an interior passage. The non-deflecting airfoil is made of a metal and configured for use in a gas turbine engine. The airfoil extends from a base to a tapered portion, and thence to a linear portion, along a primary axis. The sensing feature is formed monolithically with the airfoil, as by additive manufacturing. The interior passage is operatively connected to the sensing feature and passes through both the airfoil and the base.

Abstract: A control system for a gas turbine engine is disclosed. In embodiments, control system includes a controller and a high speed recorder. The controller obtains sensor values from sensors connected to the gas turbine engine and publishes a map of trigger events. The high speed recorder reads the sensor values from the controller. The high speed recorder checks a map header for a change to the map header on a predetermined map reading interval, sets a flag when the map header has changed, and reads the map during the next loop of the map reading interval. The control system maintains timestamps assigned for the sensor values and to the trigger events on the same temporal axis.

Abstract: A speed control system for an engine comprising at least one rotary load is provided. The speed control system may include a rotor speed controller configured to regulate speed in the rotary load based on a sensed rotor speed, exclusive of resonant mode speed oscillations, in closed loop feedback with a commanded rotor speed. To provide active damping of resonant mode speed oscillations, a resonance disturbance rejection controller may be configured to compensate a speed control signal by observing a component of the sensed rotor speed that is due to resonant mode oscillations. Based on the observed resonance component, the resonance disturbance rejection controller may compute an adjustment value for the speed control signal. In the particular case of gas turbine engines, the resonance disturbance rejection controller may effect active damping by compensation of a fuel flow request for a gas generator.