Abstract: A turbomachine includes a compressor, a combustor operatively connected to the compressor, and an injection nozzle operatively connected to the combustor. The injection nozzle includes a main body having a first end section that extends to a second end section to define an inner flow path. The injection nozzle further includes an outlet arranged at the second end section of the main body, at least one passage that extends within the main body and is fluidly connected to the outlet, and at least one conduit extending between the inner flow path and the at least one passage.

Abstract: A turbomachine includes a compressor, a turbine, and a combustor operatively connected to the turbine. The turbomachine further includes a cap member mounted to the combustor. The cap member includes a first surface and a second surface. A combustion chamber is defined within the combustor. An injection nozzle is supported at the second surface of the cap member. The injection nozzle includes a first end that extends through an inner flow path to a second end. The first end is configured to receive an amount of a first fluid and the second end is configured to receive an amount of a second fluid. A mixture of the first and second fluids is discharged from the second end of the injection nozzle.

Abstract: A gas turbine engine is provided and includes a combustor having a first interior in which a first fuel is combustible, a turbine into which products of at least the combustion of the first fuel are receivable, a transition zone, including a second interior in which a second fuel and the products of the combustion of the first fuel are combustible, a plurality of fuel injectors which are configured to supply the second fuel to the second interior in any one of a single axial stage, multiple axial stages, a single axial circumferential stage and multiple axial circumferential stages, a compressor, by which air is supplied to the first and second interiors for the combustion therein, and a control system configured to control relative amounts of the air to the first and second interiors and relative amounts of the first and second fuels supplied to the first and second interiors.

Abstract: A gas turbine engine is provided and includes a fuel circuit, including multiple fuel circuit branches, a combustor having a first interior in which a first fuel supplied thereto by any one of the multiple fuel circuit branches is combustible, a turbine, a transition zone, including a second interior in which a second fuel supplied thereto by any one of the multiple fuel circuit branches, the second fuel including gas receivable by the fuel circuit from an external source, and the products of the combustion of the first fuel are combustible, the transition zone being disposed to fluidly couple the combustor and the turbine to one another, and a plurality of fuel injectors which supply the second fuel to the second interior in any one of a single axial stage, multiple axial stages, a single axial circumferential stage and multiple axial circumferential stages.

Abstract: A method for forming a thermal barrier coating on a combustor panel or a fuel nozzle comprises the steps of: providing a component selected from the group consisting of a combustor panel, a bulkhead heat shield, and a fuel nozzle; optionally depositing a first layer of a metallic alloy onto the component; and depositing a ceramic composition layer using an electron beam physical vapor deposition technique. If the component is formed from a yttrium or other active element doped single crystal superalloy, the first layer may be omitted and the ceramic composition layer may be deposited directly onto a surface of the component.

Abstract: A pilot assembly for a fuel injector of a gas turbine engine may include a longitudinal passageway having an outlet end. A mass flow in the longitudinal passageway may generally flow towards the outlet end during operation of the engine. The pilot assembly may also include a liquid fuel nozzle that is positioned to direct a mixture of liquid fuel and air near the outlet end, and a compressed air inlet that is configured to direct air compressed by a compressor of the engine to a compressor discharge pressure into the longitudinal passageway without a substantial loss of pressure. The longitudinal passageway may also include a flow restriction section. The flow restriction section may be a narrowed section of the longitudinal passageway, in which an upstream side of the flow restriction section may have compressed air at substantially the compressor discharge pressure and a downstream side may have air at a lower pressure and a higher velocity.

Abstract: The present invention concerns a unit (1) for aircraft turbomachine comprising a housing (6), and first (8a) and second (8b) fuel injection systems, where each system comprises: an injector (10a, 10b) fitted with an attachment plate (16a, 16b) traversed by three mounting holes positioned according to a first configuration for the first systems and according to a second configuration distinct from the first for the second systems; a reception device (12a, 12b) installed on the housing; a sealing joint (14) interposed between the plate and the reception device; and securing screws (18a, 18b) attaching the plate on to its reception device. According to the invention, the sealing joints (14) are identical for the first and second fuel injection systems.

Abstract: A catalyst conduit for a catalytic reactor of a turbine combustor, the conduit comprising a tube including an inlet and an outlet, and a wall with an interior surface and an exterior surface. The tube contains a variation in its cross sectional area along at least a portion of its length to change a property of a fluid flowing adjacent the wall of the tube. An oxidation catalyst is deposited on at least a portion of the tube.

Abstract: A combustion installation including a combustion device with a combustion space for combustion of a fuel and an oxygen-containing gas to a combustion gas in the combustion space and a membrane device is described. The membrane device is arranged for the flow of air, past a membrane in a second compartment of the membrane device, to be in the same direction as the flow of combustion gases, past the membrane in a first compartment of the membrane device.

Abstract: A combustor swirler for a gas turbine engine and method of manufacturing by metal injection molding an inner component and an outer cylindrical component. Indentations are molded in one of the inner and outer components and sealed by the engagement of the components together to form a series of fluid flow passages. The inner and outer components are molded with interlocking features for ensuring proper alignment of the components during assembly.

Abstract: Methods of managing fuel temperatures in fuel injectors for gas turbine engines include cooling fuel circuits by initiating fuel flow therethrough using opened, closed, and semi-open control techniques. A fuel injector for a gas turbine engine includes a feed arm having a fuel inlet fitting for delivering fuel to at least one fuel conduit extending through the feed arm. A nozzle body depends from the feed arm and has at least one fuel circuit extending therethrough. The fuel circuit is configured and adapted to receive fuel from the feed arm and to issue fuel from an exit orifice of the nozzle body. Sensing means are provided adjacent to the at least one fuel circuit. The sensing means are configured and adapted to provide temperature feedback in order to control fuel flow in the at least one fuel circuit to maintain fuel temperature within a predetermined range.

Abstract: A fuel injector for a gas turbine engine may include a pilot assembly extending along a longitudinal axis. The pilot assembly may be configured to direct a pilot fuel-air mixture to a combustor of the gas turbine engine. The fuel injector may also include a rich catalyst module circumferentially disposed about the pilot assembly. The catalyst module may be configured to simultaneously direct a stream of compressed air and a stream of first fuel-air mixture therethrough without intermixing. The fuel injector may also include a post mix zone disposed downstream of the catalyst module. The post mix zone may be configured to mix the compressed air and the first fuel air mixture to create a main fuel-air mixture. The fuel injector may further include an air swirler disposed downstream of the post mix zone. The air swirler may be configured to direct the main fuel-air mixture to the combustor without intermixing with the pilot fuel-air mixture.

Abstract: In the fuel nozzle, the fuel is circulated in a helical path around the interface of a stem of the fuel nozzle and a flange for increase the cooling.

Abstract: A secondary nozzle is provided for a gas turbine. The secondary nozzle includes a flange and an elongated nozzle body extending from the flange. At least one premix fuel injector is spaced radially from the nozzle body and extends from the flange generally parallel to the nozzle body. At least one second nozzle tube is fluidly connected to the fuel source and spaced radially outward from the first nozzle tube with a proximal end fixed to the flange. The second nozzle tube has a distal end, spaced from the proximal end, with at least one aperture therein. A passageway extends between the proximal end and the distal end of the second nozzle tube, with the passageway fluidly connecting to the fuel source and the aperture.

Abstract: A feed injector for providing feed to a gasifier of an integrated gasification combined cycle system includes: a base leading to a body and terminating in a tip, the tip including an exitway for injecting feed into the gasifier; the tip including a mating of an inner shell disposed within a core insert, with an outer shell in which the core insert is disposed; a plurality of spacers disposed between the core insert and inner shell thus providing an inner annular space, and another plurality of spacers disposed between the core insert and outer shell thus providing an outer annular space; the inner annular space and the outer annular space being in fluid communication at the tip and providing for a flow of coolant from the base to the tip and back to the base. A method of fabrication and an integrated gasification combined cycle power plant are also disclosed.

Abstract: A fuel injector for a gas turbine engine is disclosed which includes an inlet fitting for receiving fuel, a nozzle for issuing fuel into the gas turbine engine, an injector body extending between the inlet fitting and the nozzle and having and interior bore extending therethrough, and an elongated fuel tube disposed within the interior bore of the injector body for delivering fuel from the inlet fitting to the nozzle. The fuel tube has an inlet end portion dynamically associated with the inlet fitting and an outlet end portion rigidly connected to the nozzle. An adapter is operatively associated with either the inlet end section of the fuel tube or a reception bore formed with the inlet fitting of the injector for accommodating a seal member in a manner that permits thermal growth of the injector body relative to the fuel tube.

Abstract: Disclosed is a combustor including a baffle plate having at least one through baffle hole and at least one fuel nozzle extending through the at least one baffle hole. A plurality of injection holes extend through the at least one fuel nozzle and are configured to meter a flow of diluent into the combustor. Further disclosed is a method for providing diluent to a combustor including providing a plurality of openings located at at least one fuel nozzle extending through a through hole in a baffle plate. The diluent is flowed through the plurality of openings toward at least one airflow opening in the at least one fuel nozzle.

Abstract: A combustion process for burning fuel in a combustion chamber is provided. The process includes supplying fuel and air to a burner, the amount of air supplied being at least as much as required for stoichiometric combustion of the fuel and subsequent dilution of the combustion process. The process also includes injecting the fuel and all the air from the burner directly into the combustion chamber in a substantially unmixed state as a fuel stream within an air stream. Fuel is injected from a nozzle, which is nested within an air nozzle. The fuel nozzle ejects a fuel stream of such thickness that the fuel burns in the combustion chamber as a diffusion flame with a high surface-to-volume ratio at or close to the stoichiometric fuel/air ratio. The flow of air through the air nozzle is subject to the venturi effect.

Abstract: A fuel delivery system for a turbine engine has at least one fuel injector having an upstream orifice arrangement that produces a first pressure drop of flowing fuel and a downstream orifice arrangement that produces a second pressure drop of the flowing fuel. The upstream orifice arrangement or the downstream orifice arrangement includes a noncylindrical orifice.

Abstract: Pilot fuel injected from fuel injection ports 21 of a pilot nozzle 2 bumps against an inner wall surface of a tapered portion of an inner circumference of a cone 41 of a pilot cone 4. At this time, the position where a pilot fuel from the fuel injection ports 21 hits is located in a range from a middle of the tapered portion of the inner circumference of a cone 41 to a downstream-side tip thereof.

Abstract: A gas turbine engine fuel nozzle assemblage (10) comprises a nozzle outer body (25) comprising a premixing section (23) and an interiorly disposed first fuel passageway (22) to supply fuel to the premixing section (23), and more interiorly a central channel (33) comprising an inlet (30) from an air supply, an aperture (19) at an upstream end to receive a lance (18), and a downstream-disposed annular bearing surface (21) adapted to slidingly engage the lance, the fuel nozzle assemblage adapted so that the lance may be alternatably selected as any interchangeable one of a gas lance, an oil lance, and a non-fueling dummy lance. Between the lance and the central channel (33) is formed a cooling fluid passageway (24) that is in fluid communication with the inlet (30) and one or more cooling fluid passageway exits (60). The interchangeability of the lances (18) is effective to provide a desired flexible functionality to said fuel nozzle assemblage.

Abstract: A fuel injector (36) for alternate fuels (26A, 26B) with energy densities that differ by at least about a factor of two. Vanes (47B) extend radially from a fuel delivery tube structure (20B) with first and second fuel supply channels (19A, 19B). Each vane has first and second radial passages (21A, 21B) communicating with the respective fuel supply channels, and first and second sets of apertures (23A, 23B) between the respective radial passages and the surface (49) of the vane. The first fuel supply channel, first radial passage, and first apertures form a first fuel delivery pathway providing a first fuel flow rate at a given backpressure. The second fuel supply channel, second radial passage, and second apertures form a second fuel delivery pathway providing a second fuel flow rate that may be at least about twice first fuel flow rate at the given backpressure.

Abstract: A fuel injector for a secondary fuel nozzle in a gas turbine includes axially oriented air slots and a plurality of fuel injection holes disposed between the air slots. The plurality of fuel injection holes include axially oriented injection holes and circumferentially oriented injection holes such that fuel input through the plurality of fuel injection holes is injected in both a circumferential direction and an axial direction to mix with air flowing through the air slots.

Abstract: A rocket engine system includes a combustion chamber defining a centerline axis, an oxidizer supply, a first fuel delivery circuit connected to a fuel supply, a second fuel delivery circuit connected to the fuel supply, and an injector assembly positioned at the combustion chamber. The injector assembly includes a faceplate having a plurality of openings therethrough, a first injector element connected to the first fuel delivery circuit and extending into one of the openings in the faceplate, and a second injector element connected to the second fuel delivery circuit and extending into another of the openings in the faceplate. Annular oxidizer outlets are formed at the openings in the faceplate and connected to the oxidizer supply to deliver oxidizer to the combustion chamber.

Abstract: A combustor assembly in a gas turbine engine. The combustor assembly includes a combustor device coupled to a main engine casing, a first fuel injection system, a transition duct, and an intermediate duct. The combustor device includes a flow sleeve for receiving pressurized air and a liner disposed radially inwardly from the flow sleeve. The first fuel injection system provides fuel that is ignited with the pressurized air creating first working gases. The intermediate duct is disposed between the liner and the transition duct and defines a path for the first working gases to flow from the liner to the transition duct. An intermediate duct inlet portion is associated with a liner outlet and allows movement between the intermediate duct and the liner. An intermediate duct outlet portion is associated with a transition duct inlet section and allows movement between the intermediate duct and the transition duct.

Abstract: A fuel injector for a gas turbine combustor is disclosed which includes a fuel nozzle for issuing fuel into the combustor for combustion, at least one photodetector responsive to flame radiation indicative of an OH chemiluminescence peak, and at least one photodiode responsive to flame radiation indicative of a CH chemiluminescence peak.

Abstract: A combustor apparatus for use in a gas turbine engine. The combustor apparatus includes a liner, a flow sleeve, and a fuel injection system. The liner includes an inner volume, wherein a portion of the inner volume defines a main combustion zone. The flow sleeve receives compressed air, is positioned radially outward from the liner, and includes a forward end and an aft end. The fuel injection system is coupled to the flow sleeve and provides fuel into the inner volume of the liner downstream from the main combustion zone. The fuel injection system includes a fuel manifold and a fuel dispensing structure. The fuel manifold is coupled to the flow sleeve and includes a cavity for receiving fuel. The fuel dispensing structure is associated with the cavity and distributes fuel from the cavity to the liner inner volume.

Abstract: A torch igniter and method of cooling the torch igniter includes axially flowing a first stream of gaseous oxidizer through a torch throat and vortically flowing a second stream of the gaseous oxidizer within a combustion chamber.

Abstract: A secondary fuel nozzle is formed by brazing and welding a central core, a cylindrical body, and a unitary secondary fuel nozzle portion. The central core has a central bore for receiving a liquid fuel cartridge, and at least two passages concentric with the central bore. The secondary fuel nozzle portion includes a base flange and a main shaft having a central bore for aligning with the central bore of the core and for receiving the liquid fuel cartridge, and a plurality of peripheral bores disposed at spaced locations about the central bore for flow communication with the concentric passages of the core. The core is brazed to the base flange and the cylindrical body is disposed around the core and welded to the base flange to define a one-piece secondary fuel nozzle assembly.

Abstract: A gas turbine combustor having a self-purging pilot fuel injection system and method of operation thereof is disclosed. The pilot fuel injection system comprises a radial inflow swirler, a generally axially extending centerbody, and at least one fuel injection source. In operation a fluid containing at least air passes along the centerbody outer surface clearing any remaining fuel from proximate the fuel injection source so as to prevent flame attachment proximate the fuel injection source.

Abstract: A turbomachine combustion chamber including a substantially L-shaped fuel injector and means for mounting and fastening the injector in an orifice of the casing of the chamber, said means including an outer collar carried by the injector and a removable annular spacer surrounding the injector and designed to be interposed between the collar of the injector and the casing.

Abstract: A combustor assembly for a gas turbine engine comprises a casing arrangement defining an aperture and a seal element mounted on the casing arrangement through which a component of the combustor can extend. The seal element comprises a relatively flexible force absorbing portion and a relatively rigid sealing portion. The force absorbing portion is provided between the sealing portion and the casing arrangement. The force absorbing portion is resiliently deformable to absorb force during movement of the casing arrangement. Such resilient deformation restricts transmission of the forces to the sealing portion. The seal element may be configured to carry a seal member.

Abstract: A process of coating an article includes the steps of (1) applying a ceramic compound to at least one surface of an article to form a layer of ceramic compound; (2) applying at least one inert compound upon the ceramic compound layer to form a protective layer, wherein the at least one inert compound is composed of a first inert compound having a cubic crystalline structure of formula (I) A3B2X3O12, or a second inert compound comprising a hexagonal crystalline structure of formula (II) A4B6X6O26, or a mixture of the first inert compound and the second inert compound; (3) optionally drying the coated article; (4) optionally repeating steps (2) and (3); and (5) heat treating the coated article.

Abstract: A secondary fuel delivery system for delivering a secondary stream of fuel and/or diluent to a secondary combustion zone located in the transition piece of a combustion engine, downstream of the engine primary combustion region is disclosed. The system includes a manifold formed integral to, and surrounding a portion of, the transition piece, a manifold inlet port, and a collection of injection nozzles. A flowsleeve augments fuel/diluent flow velocity and improves the system cooling effectiveness. Passive cooling elements, including effusion cooling holes located within the transition boundary and thermal-stress-dissipating gaps that resist thermal stress accumulation, provide supplemental heat dissipation in key areas.

Abstract: A valve assembly is disclosed for modulating the flow of fuel to a fuel nozzle at a high frequency or in a stepped manner to actively control combustion in a gas turbine engine which includes a valve housing defining an inlet portion for receiving fuel from a fuel source at an initial flow rate and an outlet portion for delivering fuel to a fuel nozzle at the initial flow rate or a modulated flow rate depending upon a detected combustion condition, and a mechanism disposed within the valve housing for modulating the flow rate of fuel to the outlet portion in response to a detected combustion condition.

Abstract: A common regulator valve is provided for a variable displacement pump fuel metering scheme in which the common regulator valve both controls working output to a pump actuator to control displacement of the variable displacement pump and also to control bypass of excess fuel flow. The regulator valve also includes a differential piston which generates a compensation force off of the bypass flow in order to compensate for changes in spring force and flow reaction force at different system pressures and operational states. As a result, errors in the metered fuel flow can be either eliminated or substantially reduced.

Abstract: An injection nozzle for a turbomachine includes a main body having a first end portion that extends to a second end portion defining an exterior wall having an outer surface. A plurality of fluid delivery tubes extend through the main body. Each of the plurality of fluid delivery tubes includes a first fluid inlet for receiving a first fluid, a second fluid inlet for receiving a second fluid and an outlet. The injection nozzle further includes a coolant delivery system arranged within the main body. The coolant delivery system guides a coolant along at least one of a portion of the exterior wall and around the plurality of fluid delivery tubes.

Abstract: A fuel nozzle for a gas turbine engine includes an engine mount end and a discharge end that discharges an air/fuel mixture into a combustion chamber. The fuel nozzle includes a centerbody and a heat shield. The heat shield is fixed to the centerbody at a mid-mount position that is centrally located between first and second ends of the heat shield to allow the heat shield to remain thermally isolated from radially adjacent components to reduce the adverse effects of thermal stresses.

Abstract: With a lean premix burner (1), a plurality of preferably V-shaped, closely spaced fuel channels (12) is formed into the circumferential fuel-supplied film application surface (8) of the atomizer lip (9) in the direction of flow, in order to achieve a better heat transfer to the fuel due to the uniform fuel distribution and a transverse flux in the plurality of small fuel flows caused by the Marangoni effect, to completely converse the fuel by early vaporization and improved spraying, to reduce nitrogen oxide emission and to suppress combustion-driven pressure oscillations.

Abstract: A fuel injector assembly for use in a turbine engine having a combustion section and a turbine section downstream from the combustion section. The fuel injector assembly includes a flow sleeve defining a pre-mixing passage of the combustion section and including a sleeve wall having a forward end proximate to a cover plate of the combustion section and an opposed aft end. An annular cavity in fluid communication with a source of fuel is formed in the sleeve wall adjacent the aft end. A fuel dispensing structure is associated with the cavity and includes at least one fuel distribution aperture for distributing fuel from the cavity to the pre-mixing passage.

Abstract: Fuel control arrangements for gas turbine engines generally comprise an injector and a fuel control valve. Typically the fuel control valve is controlled in terms of fuel demand through fuel pressure presented to the valve. Fuel demand may vary and in such circumstances stagnation of fuel adjacent to the valve may cause degradation of the fuel and therefore spurious operational performance. By providing a dedicated working fluid, and typically hydraulic, pressure to the valve a variable aperture port can be displaced to alter the fuel flow configuration within the valve. In such circumstances different fuel valve conditions can be generated by altering the available area of aperture in the port to divert or present fuel to the injector between and across first or primary fuel paths and second or pilot fuel paths as required. Thus more flexibility with regard to fuel presentation to the injector is achieved as well as consistency with respect to avoiding fuel degradation as fuel demand varies.

Abstract: An axially staged combustion system is provided for a gas turbine engine comprising a main body structure having a plurality of first and second injectors. First structure provides fuel to at least one of the first injectors. The fuel provided to the one first injector is adapted to mix with air and ignite to produce a flame such that the flame associated with the one first injector defines a flame front having an average length when measured from a reference surface of the main body structure. Each of the second injectors comprising a section extending from the reference surface of the main body structure through the flame front and having a length greater than the average length of the flame front. Second structure provides fuel to at least one of the second injectors. The fuel passes through the one second injector and exits the one second injector at a location axially spaced from the flame front.

Abstract: A bearing plate assembly for a turbine engine fuel injector includes a bearing plate 30, with an opening 80 bordered by a race 82. A swivel ball 90 nests inside the race and is rotatable relative thereto. A lock, which may be a tip bushing 108 resists disengagement of the swivel ball from the race. A fuel injector nozzle 38 extends through an opening 98 in the swivel ball. During engine operation, the ball can swivel inside the race to accommodate rotational movement of the nozzle about lateral and radial axes.

Abstract: Fuel injector assemblies with frictionally damped fuel supply members, including fuel feed strips. More particularly, the invention provides friction dampers and/or assemblies that frictionally damp movement of fuel supply members in at least one direction. Some of the embodiments provide a friction damper that is easily serviceable, and can be installed after final assembly of a fuel injector. Aspects of the invention are applicable to other components of fuel injectors and gas turbine engines in addition to fuel supply members.

Abstract: A fuel flow path and a flow path of air for combustion are disposed coaxially to create a coaxial jet such that a fuel flow is embraced by an air flow. A large number of such fuel flow paths and air flow paths are arranged in a wall surface of a combustion chamber to create coaxial nozzle jets. Some of the flow paths of air for combustion are arranged inclinedly so as to create rotation for the stabilization of combustion and straight portions not having an inclination angle are added respectively to upstream ends of such inclined air flow paths. Fuel is jetted toward or within the straight portions.

Abstract: A fuel nozzle having a fuel conveying member surrounded by a sheath. An air passage is defined between the fuel conveying member and the sheath for directing air to an air swirler provided at one end of the fuel conveying member. At one flow director is provided in the air passage for promoting air and fuel uniformity and distribution at a spray tip of the fuel nozzle.

Abstract: On a burner for a gas-turbine combustion chamber which comprises a lean premix burner with centrally integrated stabilizing burner, a core air annulus (11) accommodating the atomizer nozzle (10) of the stabilizing burner is concentrically surrounded by a main air annulus (4) supplying the weak air-fuel mixture. In the adjacent issuing areas of the main air annulus and the core air annulus, a flame stabilization ring (13), which is heated by the combustion gases and whose cross-sectional surface increases in area toward the combustion chamber (5), is provided to produce an approximately hollow-cylindrical hot-gas recirculation zone (17) originating at the flame stabilization ring which ensures a stable flame formation throughout the range of operating conditions of the gas turbine.

Abstract: A fuel supply assembly for a gas turbine engine including a manifold portion with a transfer conduit, a fuel nozzle with an entry conduit and disconnectable means for retaining the transfer and entry conduits in mating engagement with one another.

Abstract: A method for fabricating a fuel nozzle assembly includes providing a nozzle portion including a fuel passageway defined about a center axis of the fuel nozzle assembly. A longitudinal axis of a first peg is oriented to intersect the fuel nozzle assembly center axis such that a first plane is defined. The first peg defines a first opening having a centerline intersecting the first peg longitudinal axis and obliquely oriented with respect to the first plane. The first peg is coupled in flow communication with the fuel passageway such that the first peg extends radially outward from the nozzle portion and such that the first opening is configured to direct a flow of fuel in an oblique direction with respect to the fuel nozzle assembly center axis to facilitate fuel mixing.

Abstract: A method of manufacturing an internal manifold of a gas turbine engine including machining an annular channel in a ring by a turning process, and varying a position of a tool bit relative to the surface of the ring as a function of a relative circumferential location of the tool bit around the ring such that the channel has a cross-sectional area that varies around a circumference of the ring.