Abstract: An exhaust nozzle of the type utilized with high performance supersonic aircraft is disclosed. The exhaust nozzle is variable between convergent and convergent/divergent geometries, as well as in aperture size. A bearing guiding segments of the nozzle is held within a roller track by an integral hold-down bracket.

Abstract: Apparatus for supplying pressurized cooling air to the turbine blades (20) of a gas turbine engine is disclosed. Multiple nozzles (38 and 40) of a tangential on-board injection system for pressurizing the cooling air are staged to provide variable rates of cooling airflow to the blades.

Abstract: A stator seal land and supporting structure suitable for use in an axial flow rotary machine is disclosed. Included are concepts for matching the thermal response of the seal land to the rotor assembly and for inhibiting rolling or twisting of the seal land under changing thermal conditions. The seal land is free to expand and contract in diameter independently of the supporting stator structure.

Abstract: A gas turbine exhaust nozzle capable of long term, reliable operation is disclosed. Nozzle cooling concepts specifically directed to convergent-divergent exhaust nozzles are developed. The exhaust nozzle disclosed has a cooling liner which is strategically positioned in the nozzle to take advantage of aerodynamic conditions along the axial length of the nozzle.

Abstract: The present invention provides improvements to fan rotor blades of turbofan gas turbine engines. Increased low cycle fatigue life is sought, and a specific object is to obtain a more nearly uniform chordwise distribution of maximum stress levels across the root sections of fan blades.In one effective embodiment incorporating concepts of the present invention the root section of a fan blade is contoured to an arcuate geometry which approximates the contour of the airfoil cross section at the inner wall of the working medium flowpath. Further contour specifications for reducing local stress levels are discussed.

Abstract: Apparatus for supporting the rotor blades of a helicopter is disclosed. Support in droop under both statically and dynamically loaded conditions is discussed. The droop stop mechanism 34 has low susceptibility to the deleterious effects of snow/ice or dirt contamination. The droop stop seat 42 is mounted for rotation in a corresponding receptacle 50 at the base of the rotor blade assembly 14 and is slidable between static stop and dynamic stop positions along the pitch axis of the blade to be supported.

Abstract: Method for controlling the clearance between rotating and stationary components of a gas turbine engine are disclosed. Techniques for achieving close correspondence between the radial position of rotor blade tips and the circumscribing outer air seals are disclosed. In one embodiment turbine case temperature modifying air is provided in flow rate, pressure and temperature varied as a function of engine operating condition. The modifying air is scheduled from a modulating and mixing valve supplied with dual source compressor air. One source supplies relatively low pressure, low temperature air and the other source supplies relatively high pressure, high temperature air. After the air has been used for the active clearance control (cooling the high pressure turbine case) it is then used for cooling the structure that supports the outer air seal and other high pressure turbine component parts.

Abstract: A fan rotor assembly having decreased susceptibility to vibratory damage is disclosed. In one embodiment described the rotor assembly includes a plurality of principal fan blades 22 and a plurality of secondary fan blades 36 associated therewith. The secondary blades are coextensive with the principal fan blades over the inner portion of the principal blade span.

Abstract: Structure coated with graded ceramic material and methods of coating application are disclosed. Techniques for maintaining low stress to strength ratios across the depth of the coating are discussed.In one particular structure the coating is applied to a metal substrate (12) and comprises a metallic bond coat (14), a first interlayer (16) of metal/ceramic material, a second interlayer (18) of metal/ceramic material having an increased proportion of ceramic and an all ceramic layer. Modulation of the metal substrate temperature during the coating process establishes a desired residual stress pattern in the part.

Abstract: Methods and apparatus for improving the thrust specific fuel consumption (TSFC) of a gas turbine engine employing an exterior active clearance control system are disclosed.The pressure within the nacelle compartment to which active clearance control air is discharged is operated under altitude cruise conditions at a level on the order of one to two and one-half pounds per square inch (1-21/2 psi) above the ambient atmosphere. Flow discharging from the nacelle is directed through an aft facing vent nozzle for purposes of thrust recovery.

Abstract: Structure coated with graded ceramic material and methods of coating application are disclosed. Techniques for maintaining low stress to strength ratios across the depth of the coating are discussed. In one particular structure the coating is applied to a metal substrate (12) and comprises a metallic bond coat (14), a first interlayer (16) of metal/ceramic material, a second interlayer (18) of metal/ceramic material having an increased proportion of ceramic and an all ceramic layer. Modulation of the metal substrate temperature during the coating process establishes a desired residual stress pattern in the part.

Abstract: Apparatus for dampening rotor blade vibratory energy in a rotary machine is disclosed. Concepts employing blade to blade damping are discussed.In one detailed form, a damper (52) is disposed to seat against the undersides of adjacent blade platform sections (20) and a seal (42) is spaced sufficiently close to the damper so as to be deflected against the damper under centrifugal loads to augment dampening of the rotor blades by the damper.

Abstract: A gauge for measuring the chord length across an airfoil at a plurality of locations along the span is disclosed. Concepts ensuring accurate measurement notwithstanding deviations of the airfoil contour from design conditions are discussed. Floating gauge plates 46 locate the local position of the airfoil leading edge. A notch 58 in each plate marks the minimum acceptable chord length.

Abstract: Rotor blade and disk structures enabling the disassembly and reassembly of a single rotor blade are disclosed. The concepts are particularly suited to configurations employing interlocking mid-span shrouds which inhibit the withdrawal of a single blade from a disk.In one specific geometry the rotor blade root section (20) and the disk attachment slot (24) are contoured to provide increasing clearance between the bottom of the blade root section and the attachment slot as the blade is withdrawn axially from the slot. Rocking of the blade within the provided clearance enables withdrawal of the blade around the shroud segments (30,32) and airfoil sections (16) of the adjacent blades (12).

Abstract: A turbine rotor assembly 10 for providing cooling air to a turbine blade 28 is disclosed. An annulus 24 is formed between the rotor disk 12 and a segmented sideplate 20 in which the segments have overlapping ends 22. A thin flexible metal strip 36 having overlapping ends 38 is disposed about the radially inward edge of the sideplate segments to seal the leakage flowpath between the overlapping ends 22 of the sideplate segments 20 as the sideplate segments expand and contract with the supporting disk 12.

Abstract: A gas turbine engine and structure for mounting the gas turbine engine on an aircraft is disclosed. Techniques for controlling the magnitude of engine case deflection from the axis of the engine are developed. The transfer of a portion of the gust and thrust loads externally of the engine case to a location downstream of the rearward engine mount generates a reverse moment which counteracts deflection in the engine case.

Abstract: A method to test a rotating metal part at a cryogenic temperature as a comprehensive non-destructive inspection technique is disclosed. This method for proof testing a rotating metal part was arrived at for a material which has the characteristics of high strength and low fracture toughness at an operating temperature and when placed at a cryogenic temperature, the strength of the material is increased and the fracture toughness is decreased.

Abstract: Outer air seal structures of particular suitability for use in gas turbine engines are disclosed. Techniques for improving resistance to erosion while maintaining good abradability are discussed.In one particular structure the ceramic facing material of an outer air seal (30) at the leading edge region (36) is densified by a plasma gun to produce a glazed area (52) which is resistant to erosion.

Abstract: Apparatus for mixing fuel and air for combustion in a gas turbine engine is disclosed. Various construction details capable of reducing pollutant emissions in the engine exhaust are discussed. In detailed form scoops 20 at the upstream end of the combustion chamber 12 provide uniform flow about the fuel nozzles. Deflectors 26 downstream of the fuel nozzles collimate the scooped air to aerodynamically confine the mixing fuel and air. Premature spreading of the fuel and air before nearly homogeneous fuel-air ratios are achieved is inhibited.

Abstract: Effective damping of blade vibratory energy is sought by the apparatus described herein. The concepts relate specifically to what is known as blade to blade damping as is distinguished from blade to ground damping.The dampers employed have a "T" shaped cross section geometry and are designed to extend circumferentially on an engine rotor between the platform sections of each pair of rotor blades. The dampers are of extreme light weight such that the slipload forces required to generate sliding contact between the damper and the blade platforms is low.