Abstract: A power transmission module for an aircraft, the module including a torque input connected to a turbine shaft, a first torque output and a second torque output, the power transmission module including a mechanical reducer including a sun gear forming the torque input, and planet gears carried by a planet carrier, wherein each of the planet gears includes at least three independent toothings and further includes a first toothing meshed with the sun gear, a second toothing meshed with an element forming one of the torque outputs, and a third toothing meshed with another element.

Abstract: Disclosed is a turbomachine (10) with counter-rotating turbine for an aircraft, comprising: —a high-pressure body, —a low-pressure counter-rotating turbine (22), —a planetary-type mechanical epicyclic reduction gear (42), —a guide bearings (56-62) for the turbine shafts (36, 38), characterised in that said reduction gear (42) and certain of the bearings (60, 62) are housed in a lubrication chamber (86) supplied with oil and comprising dynamic seals (86a-86d), and in that the turbomachine comprises circuits (C1, C2) for pressurising these seals.

Abstract: An aircraft engine nacelle for coupling to a wing of an aircraft is disclosed having a fore end, and an aft end that is immoveable relative to the fore end. The aft end includes a major axis Mj and a minor axis Mi, and the nacelle is configured such the minor axis Mi is closer to vertical V than the major axis Mj when the nacelle is coupled to the wing and the aircraft is stationary on the ground. An aircraft system and an aircraft are disclosed each including the aircraft engine nacelle.

Abstract: A method of distributing power within a gas turbine engine is disclosed. In various embodiments, the method includes driving a high pressure turbine having a first stage and a second stage with an exhaust stream from a combustor, the first stage connected to a high pressure turbine first stage spool and the second stage connected to a high pressure turbine second stage spool; driving a high pressure compressor connected to a high pressure compressor spool via a differential system, the differential system having a first stage input gear connected to the high pressure turbine first stage spool, a second stage input gear connected to the high pressure turbine second stage spool and an output gear assembly connected to the high pressure compressor spool; and selectively applying an auxiliary input power into at least one of the high pressure compressor spool and the high pressure turbine.

Abstract: A dual-flow turbojet engine having a central shaft surrounded by a high-pressure body which rotate about the same longitudinal axis while being independent in rotation, and including a fan driven by the central pressure shaft; a high-pressure compressor and a high-pressure turbine mounted on the high-pressure body; an inter-turbine casing; a low-pressure turbine mounted on a low-pressure rotor surrounding the central shaft; an exhaust casing on which an output cone is mounted; a reduction gear with which the low-pressure rotor drives the central pressure shaft; two bearings mounted on the exhaust casing and respectively receiving the central shaft and the low-pressure rotor; a bearing mounted on the inter-turbine casing and receiving the low-pressure rotor.

Abstract: A turbofan gas turbine engine includes, in axial flow sequence, a heat exchanger module, a fan assembly, a compressor module, and a turbine module. The fan assembly includes fan blades defining a corresponding fan area (AFAN). The heat exchanger module is in fluid communication with the fan assembly by an inlet duct, and includes radially-extending vanes arranged in a circumferential array with at least one vane including a heat transfer element for heat transfer from a first fluid contained within each element to an airflow passing over a surface of each heat transfer element before entering the fan assembly inlet. Each heat transfer element extends axially along the corresponding vane, with a swept heat transfer element area (AHTE) being the wetted surface area of all heat transfer elements in contact with the airflow. A Fan to Element Area parameter FEA of AHTE/AFAN lies in the range of 47 to 132.

Abstract: A turbojet engine including a shaft surrounded by a low-pressure rotor surrounded by a coaxial and independent high-pressure spool, this turbojet engine including from upstream to downstream: a fan driven by the shaft; a low-pressure compressor carried by the rotor; an inter-compressor casing; a high-pressure compressor and a high-pressure turbine carried by the high-pressure spool; an inter-turbine casing; a low-pressure turbine carried by the rotor; an exhaust casing; this turbojet engine including an upstream rotor bearing carried by the inter-compressor casing; a downstream rotor bearing carried by the exhaust casing; a gearbox downstream of the downstream bearing and through which the rotor drives the shaft; a downstream shaft bearing downstream of the downstream rotor bearing.

Abstract: A gas turbine engine includes a very high speed low pressure turbine such that a quantity defined by the exit area of the low pressure turbine multiplied by the square of the low pressure turbine rotational speed compared to the same parameters for the high pressure turbine is at a ratio between about 0.5 and about 1.5. The high pressure turbine is supported by a bearing positioned at a point where the first shaft connects to a hub carrying turbine rotors associated with the second turbine section.

Abstract: A gas turbine engine includes a shaft and a hub supported by the shaft. A housing includes an inlet and an intermediate case that respectively provide an inlet and an intermediate case flow path. A rotor is connected to the hub and supports a compressor section arranged axially between the inlet and the intermediate case flow paths. A compressor section inlet has a radially inner boundary that is spaced a second radial distance from the rotational axis different from the first radial distance. First and second bearings support the shaft relative to the intermediate case and the inlet case, respectively. An inner race of the first bearing and an inner race of the second bearing engage and rotate with the hub. A fan shaft is drivingly connected to a fan having fan blades. A gear system is connected to the fan shaft and driven through a flex shaft.

Abstract: A method of distributing power within a gas turbine engine is disclosed. In various embodiments, the method includes driving a high pressure turbine having a first stage and a second stage with an exhaust stream from a combustor, the first stage connected to a high pressure turbine first stage spool and the second stage connected to a high pressure turbine second stage spool; driving a high pressure compressor connected to a high pressure compressor spool via a differential system, the differential system having a first stage input gear connected to the high pressure turbine first stage spool, a second stage input gear connected to the high pressure turbine second stage spool and an output gear assembly connected to the high pressure compressor spool; and selectively applying an auxiliary input power into at least one of the high pressure compressor spool and the high pressure turbine.

Abstract: An engine assembly includes an engine including a component and defining an opening and an interior, the component including a first side and an opposite second side, the second side positioned within the interior of the engine. The engine assembly also includes an inspection tool having a first member including at least one of a receiver or a transmitter and directed at the first side of the component. The inspection tool also includes a second member including the other of the receiver or the transmitter and positioned at least partially within the interior of the engine and directed at the second side of the component to communicate a signal with the first member through the component, the second member being a robotic arm extending through the opening of the engine.

Abstract: Turbine engine (10) with a contra-rotating turbine for an aircraft, the turbine engine comprising a contra-rotating turbine (22) whose first rotor (22a) is configured to rotate in a first direction of rotation and is connected to a first turbine shaft (36), and a second rotor (22b) is configured to rotate in an opposite direction of rotation and is connected to a second turbine shaft (38), the first rotor comprising turbine wheels (36a) inserted between turbine wheels (38a) of the second rotor, the turbine engine further comprising a mechanical reduction gear (42) with an epicyclic gear train which comprises a sun gear (44) driven in rotation by said second shaft, a ring gear (40) driven in rotation by said first shaft, and a planet carrier (46) fixed to a stator casing (28) of the turbine engine situated downstream from the contra-rotating turbine with respect to direction of flow of the gases in the turbine engine, the turbine engine further comprising a bearing (56) for guiding the second shaft with res

Abstract: A gas turbine engine, in particular an aircraft engine, includes: a turbine connected via an input shaft device to a gearbox device having a sun gear, a planet carrier having a plurality of planet gears attached thereto, and a ring gear, the sun gear is connected to the input shaft device, the planet carrier or the ring gear is connected to a propulsive fan via an output shaft device of the gearbox device, with a rear carrier bearing device radially between the planet carrier and a part on the input shaft on the input side of the gearbox device.

Abstract: A geared turbomachine includes: a fan, a low pressure shaft which drives the fan rotationally around the main axis of the turbomachine, a speed reducer interposed between the fan and the low pressure shaft, and an alternator driven by the low pressure shaft. The alternator includes an inductor and an armature of which one of the inductor and the armature is integral with the fan and the other of the inductor and the armature is integral with the low pressure shaft.

Abstract: An exoskeletal gas turbine engine having a rotatable outer shaft and an inner stationary case enclosed in a casing. The engine comprises a compressor section at an inlet end, a combustor section, and a turbine section at an outlet end. Rotating compressor blades and turbine blades are attached to, and extend radially inward from, an inner surface of the outer shaft. Stationary vanes are attached, and extend radially outward from, an outer surface of the inner stationary case. The outer shaft rotates around a front bearing and a rear bearing. An inlet compressor blade arrangement is attached to the outer race of the front bearing. An outlet turbine blade arrangement is attached to the outer race of the rear bearing. The inner race of the front and rear bearings attach to the inner stationary case.

Abstract: A gas turbine engine for an aircraft includes an engine core with a turbine, a compressor, and a core shaft connecting them. The engine includes a fan, with a plurality of fan blades, located upstream of the core and a gearbox receiving an input from the core shaft and outputting drive so the fan is at a lower rotational speed than the core shaft. The turbine includes a plurality of stages of axially spaced rotor blades mounted on a rotor, which are surrounded by a turbine casing. The turbine has an inlet defined at an upstream end of a first stage of blades and an outlet defined at a downstream end of a last stage of blades and a ratio of the area of the outlet to the inlet is at between 2.5 and 3.5. This increases the pressure ratio of and power extracted from the turbine and the engine.

Abstract: The present disclosure is directed to a method of operating a gas turbine engine with an interdigitated turbine section. The engine includes a fan rotor, an intermediate pressure compressor, a high pressure compressor, a combustion section, and a turbine section in serial flow arrangement. The turbine section includes, in serial flow arrangement, a first stage of a low speed turbine rotor, a high speed turbine rotor, a second stage of the low speed turbine rotor, an intermediate speed turbine rotor, and one or more additional stages of the low speed turbine rotor. The low speed turbine rotor is coupled to the fan rotor via a low pressure shaft. The intermediate speed turbine rotor is coupled to the intermediate pressure compressor via an intermediate pressure shaft. The high speed turbine rotor is coupled to the high pressure compressor via a high pressure shaft.

Abstract: The present disclosure is directed to a gas turbine engine defining a longitudinal direction, a radial direction, and a circumferential direction, and wherein the gas turbine engine defines an upstream end and a downstream end along the longitudinal direction. The gas turbine engine includes a turbine section that includes a first rotating component and a second rotating component. The first rotating component includes an inner shroud and an outer shroud outward of the inner shroud in the radial direction. The outer shroud defines a plurality of outer shroud airfoils extended inward of the outer shroud along the radial direction. The first rotating component further includes at least one connecting airfoil coupling the inner shroud and the outer shroud. The second rotating component is upstream of the one or more connecting airfoils of the first rotating component along the longitudinal direction. The second rotating component includes a plurality of second airfoils extended outward in the radial direction.

Abstract: The present disclosure is directed to a gas turbine engine defining a longitudinal direction, a radial direction, and a circumferential direction, and an upstream end and a downstream end along the longitudinal direction. The gas turbine engine includes a turbine section, a gearbox proximate to the turbine section, and a driveshaft. The turbine section includes a first rotating component interdigitated with a second rotating component along the longitudinal direction. The first rotating component includes an outer shroud defining a plurality of outer shroud airfoils extended inward of the outer shroud along the radial direction and one or more connecting airfoils coupling the outer shroud to a radially extended rotor. The second rotating component includes an inner shroud defining a plurality of inner shroud airfoils extended outward of the inner shroud along the radial direction. The second rotating component is coupled to an input shaft connected to an input gear of the gearbox.

Abstract: A compressor of an axial turbine engine comprising two rotors or contra-rotating drums, of which an inner rotor and an outer rotor are each provided with blade rows forming a regular alternating pattern. The inner rotor is provided with a radial annular junction fixed to the transmission shaft coming from a turbine. The outer rotor surrounds the inner rotor. The compressor also comprises a rotating bearing linked to the outer rotor and arranged axially level with the radial junction of the inner rotor so as to align the mechanical links axially. This alignment limits the effect of centrifugal force between the clearances between the blades and the walls of the rotors. A transmission with a pinion with a radial rotation axis allows the outer rotor to be driven by the inner rotor.

Abstract: A turbomachine is provided, wherein the rotor comprises a planetary gear on which low-pressure end stage blades are arranged, wherein the planetary gear is designed in such a way that the frequency of the rotating blades is lower than the frequency of the rotor.

Abstract: A gas turbine apparatus may include one or more driving shafts; a compressor configured to receive power from the one or more driving shafts, suck air, and compress the sucked air at high pressure. The gas turbine may include a combustor configured to mix the compressed air with fuel, and combust the fuel mixture to generate combustion gas. A turbine is connected to the one or more driving shafts and is configured to rotate while the combustion gas passes through the turbine. The turbine may include one or more first turbine blades configured to rotate in a first direction and one or more second turbine blades configured to rotate in a second direction opposite to the first direction. The one or more first turbine blades and the one or more second turbine blades may be alternately arranged along an axial direction of the turbine.

Abstract: A gas turbine engine includes a very high speed low pressure turbine such that a quantity defined by the exit area of the low pressure turbine multiplied by the square of the low pressure turbine rotational speed compared to the same parameters for the high pressure turbine is at a ratio between about 0.5 and about 1.5. The high pressure turbine is supported by a bearing positioned at a point where the first shaft connects to a hub carrying turbine rotors associated with the second turbine section.

Abstract: A gas turbine engine system includes a fan section, a low pressure compressor section downstream of the fan section, a first engine core downstream from the low pressure compressor section, a second engine core downstream from the low pressure compressor section, and a flowpath control mechanism configured to selectively restrict fluid flow through the second engine core. The first engine core includes a first engine core compressor section, a first engine core combustor downstream of the first engine core compressor section, and a first engine core turbine section downstream of the first engine core combustor. The second engine core includes a second engine core compressor section, a second engine core combustor downstream of the second engine core compressor section, and a second engine core turbine section downstream of the second engine core combustor.

Abstract: An assembly in a turbine engine for controlling plural toothed pivotally-mounted blades arranged in azimuth around the axis of the turbine engine and including an actuator ring controlling a position of the blades. Racks mounted on the ring present corresponding sets of teeth meshing with the set of teeth of a respective one of the blades to place it in a selected angular position, and they are held in the radial direction by radial positioning mechanism fastened to the blade. Each rack is mounted on the ring by plural guides spaced apart circumferentially around the ring, that connect together movements of the rack and of the ring in the circumferential direction, and that are configured to slide relative to the ring, for each guide in its own radial direction, and relative to the rack in a direction of movement that is substantially radial and specific to the rack.

Abstract: An exemplary gas turbine engine includes a turbine section operative to impart rotational energy to a compressor section. The turbine section includes at least a low-pressure turbine and a high-pressure turbine, and a number of stages in the low pressure turbine is from three to five.

Abstract: A tip turbine engine provides an axial compressor rotor that is counter-rotated relative to a fan. A planetary gearset couples rotation of a fan to an axial compressor rotor, such that the axial compressor rotor is driven by rotation of the fan in a rotational direction opposite that of the fan. By counter-rotating the axial compressor rotor, a final stage of compressor vanes between the final stage of compressor blades and inlets to the hollow fan blades of the fan are eliminated. As a result, the length of the axial compressor and the overall length of the tip turbine engine are decreased.

Abstract: A gas turbine engine typically includes a fan section, a compressor section, a combustor section and a turbine section. A speed reduction device such as an epicyclical gear assembly may be utilized to drive the fan section such that the fan section may rotate at a speed different than the turbine section so as to increase the overall propulsive efficiency of the engine. In such engine architectures, a shaft driven by one of the turbine sections provides an input to the epicyclical gear assembly that drives the fan section at a speed different than the turbine section such that both the turbine section and the fan section can rotate at closer to optimal speeds providing increased performance attributes and performance by desirable combinations of the disclosed features of the various components of the described and disclosed gas turbine engine.

Abstract: A propulsion system and methods are presented. A substantially tubular structure comprises a central axis through a longitudinal geometric center, and a first fan rotates around the central axis, and comprises a first fan hub and first fan blades. The fan hub is rotationally coupled to the substantially tubular structure, and the first fan blades are coupled to the first fan hub and increase in chord length with increasing distance from the first fan hub. A second fan is rotationally coupled to the substantially tubular structure and rotates around the central axis and contra-rotates relative to the first fan. Second fan blades are coupled to the second fan hub, and a nacelle circumscribing the first fan and the second fan is coupled to and rotates with the first fan.

Abstract: An adaptive cycle gas turbine engine is disclosed having a number of features. A fan arrangement is provided having counter-rotating fan stages, one fan stage is operable to be clutched and decoupled from the other stage. A high pressure compressor bypass is also provided. A clutch is provided to at least partially drive an intermediate pressure compressor with a high pressure turbine when the high pressure compressor is bypassed. A partial bypass of the high pressure turbine may be provided.

Abstract: A gas turbine engine typically includes a fan section, a compressor section, a combustor section and a turbine section. A speed reduction device such as an epicyclical gear assembly may be utilized to drive the fan section such that the fan section may rotate at a speed different than the turbine section so as to increase the overall propulsive efficiency of the engine. In such engine architectures, a shaft driven by one of the turbine sections provides an input to the epicyclical gear assembly that drives the fan section at a speed different than the turbine section such that both the turbine section and the fan section can rotate at closer to optimal speeds providing increased performance attributes and performance by desirable combinations of the disclosed features of the various components of the described and disclosed gas turbine engine.

Abstract: A turbofan engine includes a fan rotatable about an axis, a compressor section, a combustor in fluid communication with the compressor section, a turbine section in fluid communication with the combustor, and a fan drive gear system including a carrier for supporting a plurality of gears. A torque frame is attached to the carrier. A plurality of connectors extends between the carrier and torque frame for securing the torque frame to the carrier. A scupper captures lubricant during gear operation and directing lubricant into a space between at least one of the plurality of connectors and at least one of the torque frame and the carrier.

Abstract: A turbine engine including two respectively upstream and downstream external impellers that are nonstreamlined, coaxial, and contrarotating is provided. The downstream impeller is retractable so as to reduce its diameter. The blades of the downstream impeller are mounted so as to pivot about a pivot, the axis of which forms a nonzero angle, notably perpendicular, with the axis of rotation of the impeller, the blades in the retracted position being tilted about the pivot.

Abstract: A propfan engine has a power-producing core, a plurality of nozzles for exhausting exhaust gas from the core, and a row of propeller blades rotatable about an axis. The blades are positioned downstream of the exhaust nozzles. The exhaust nozzles are rotatable about said axis. The nozzles can be aligned with the gaps between successive propeller blades in order to reduce noise during operation of the engine.

Abstract: A fan-turbine rotor assembly includes one or more turbine ring rotors. Each turbine ring rotor is cast as a single integral annular ring. By forming the turbine as one or more rings, leakage between adjacent blade platforms is minimized which increases engine efficiency. Assembly of the turbine ring rotors to the diffuser ring includes axial installation and radial locking of each turbine ring rotor.

Abstract: A bypass aeronautical engine including a fan, an LP compressor, an HP compressor, a combustion chamber, an HP turbine, and at least one LP turbine stage is disclosed. The LP turbine stage includes a first movable bladed wheel carried by a first turbine shaft and a second movable bladed wheel turning in the opposite direction to the first wheel. The fan is driven by the second wheel via a second turbine shaft and by the first shaft via a module for reversing its direction of rotation. The reversing module includes two bevel pinions carried respectively by the first and second LP turbine shafts, and a reversing pinion.

Abstract: An air vehicle propulsion system incorporates an engine core with a power shaft to drive an outer blade row. The power shaft extends through and is supported by a counter rotation transmission unit which drives an inner blade row in counter rotational motion to the outer blade row. The counter rotation transmission unit exchanges power from the engine core with the shaft. An actuator engages the shaft for translation from a first retracted position to a second extended position.

Abstract: Gas turbine engine systems involving tip fans are provided. In this regard, a representative gas turbine engine system includes: a multi-stage fan having a first rotatable set of blades and a second counter-rotatable set of blades, the first rotatable set of blades defining an inner fan and a tip fan; and an epicyclic differential gear assembly operative to receive a torque input and differentially apply the torque input to the first set of blades and the second set of blades.

Abstract: A turbine engine for aircraft includes a gas generator as well as to a receiver driven by a power turbine, and to an electric power generator, the rotor of which centered on a rotor axis distinct from the longitudinal axis, is driven into rotation by the power turbine, via a mechanical gear transmission, including a toothed drive wheel centered on the axis. Further the receiver includes a first propeller driven by a free power turbine and the toothed drive wheel is attached on an outer case of this power turbine.

Abstract: A compressor section includes a counter rotating low pressure compressor that includes outer and inner compressor blades interspersed with one another and are configured to rotate in an opposite direction than one another about an axis of rotation. A transmission couples at least one of the outer and inner compressor blades to a shaft. A turbine section includes a counter rotating low pressure turbine having an outer rotor that includes an outer set of turbine blades. An inner rotor has an inner set of turbine blades interspersed with the outer set of turbine blades. The outer rotor is configured to rotate in an opposite direction about the axis of rotation from the inner rotor. A gear system couples at least one of the outer and inner rotors to the shaft.

Abstract: A gas turbine engine includes a shaft defining an axis of rotation. An inner rotor directly drives the shaft and includes an inner set of blades. An outer rotor has an outer set of blades interspersed with the inner set of blades. The outer rotor is configured to rotate in an opposite direction about the axis of rotation from the inner rotor. A gear system is engaged to the outer rotor and is positioned upstream of the inner set of blades.

Abstract: A gas turbine engine includes a shaft defining an axis of rotation. An outer turbine rotor directly drives the shaft and includes an outer set of blades. An inner turbine rotor has an inner set of blades interspersed with the outer set of blades. The inner turbine rotor is configured to rotate in an opposite direction about the axis of rotation from the outer turbine rotor. A gear system couples the inner turbine rotor to the shaft and is configured to rotate the inner set of blades at a faster speed than the outer set of blades. The gear system is mounted to a mid-turbine frame.

Abstract: Gas turbine engine systems and related methods involving vane-blade count ratios greater than unity are provided. In this regard, a representative turbine stage for a gas turbine engine includes a first set of rotatable blades operative to be positioned downstream of and adjacent to a first set of vanes, a number of blades of the first set of blades being less than a number of vanes of the first set of vanes.

Abstract: An epicyclic gear train includes planetary gears rotatably mounted on spindles supported by an annular carrier and including axially spaced apart forward and aft sets of output teeth extending radially outwardly from a planetary gear hub and axially spaced apart forward and aft roller bearings disposed between planetary gears and spindles. The forward and aft roller bearings are axially aligned with or adjacent to spaced apart forward set of output teeth and input gear respectively. A ring gear meshes with forward set of output teeth and an external gear meshes with aft set of output teeth. An input gear fixedly attached to hub aft of aft set of output teeth and engaged with a sun gear. The output teeth, input gear, ring gear, external gear, and sun gear may all be helical. A turbofan gas turbine engine may include counter-rotatable first and second fan stages driven by a low pressure turbine through the gear train.

Abstract: A fluid distribution system for use in a gas turbine engine includes a fan shaft, a damper, a bearing, and a pump. The damper supports the bearing, and the bearing supports the fan shaft. The pump is connected to and driven by the fan shaft. The pump is also fluidically connected to the damper.

Abstract: An exemplary gas turbine engine includes a turbine section operative to impart rotational energy to a compressor section. The turbine section includes at least a low-pressure turbine and a high-pressure turbine, and a ratio of a number of stages in the low-pressure turbine to a number of stages in the high-pressure turbine is 2.

Abstract: A turbomachine comprises a turbine shaft, first and second rotors, first and second propulsion stages, and a magnetic stator. The first rotor is rotationally coupled to the turbine shaft, and coaxially arranged along an axis. The first propulsion stage is rotationally coupled to the first rotor, opposite the turbine shaft. The second rotor is coaxially arranged about the first rotor, and the second propulsion stage is rotationally coupled to second rotor, opposite the turbine shaft and adjacent the first propulsion stage. The magnetic stator is coaxially arranged between the first rotor and the second rotor, forming a magnetic coupling between the and second rotors to drive the second propulsion stage in contra-rotation with respect to the first propulsion stage.

Abstract: An aircraft propulsion unit includes a gas-turbine core engine 10 having at least one compressor, one combustion chamber and one turbine driving a main shaft 11. The main shaft 11 of the gas-turbine core engine 10 is operationally connected to at least two separate fans 6-9 via a mechanical drive connection, each of them being arranged beside the gas-turbine core engine 10.

Abstract: Gas turbine engine systems involving tip fans are provided. In this regard, a representative gas turbine engine system includes: a multi-stage fan having a first rotatable set of blades and a second counter-rotatable set of blades, the second rotatable set of blades defining an inner fan and a tip fan and being located downstream of the first set of rotatable blades; and an epicyclic differential gear assembly operative to receive a torque input and differentially apply the torque input to the first set of blades and the second set of blades.

Abstract: A Brayton cycle internal combustion engine of the open, or constant pressure type, in which rotary power is produced by the pressure of hot gasses against confined, rotor protrusions.