Abstract: Acoustic noise resulting from the interaction of a periodic pressure and velocity fluctuation induced by a periodically passing blade wake interacting with a downstream airfoil (10)is attenuated by locating an antisymmetric pressure wave generator (30) adjacent the leading edge (18) of the vane (10).

Abstract: A self-exciting optical strain sensor (20) includes dual parallel bridges (22,24) having parallel facing surfaces (32,34). Light energy (38) entering a Fabry-Perot cavity (36) formed by this surfaces (32,34) induces a periodic buildup and release of energy in the cavity (36) which is directly related to the natural resonant frequency of the bridges (22,24). Analysis of the intensity of light emitted (50) from the cavity (36) determines the bridge natural frequency.

Abstract: An arrangement for cancelling unwanted noise generated by sequential blade rows (16, 18) in a gas turbine engine (10) includes a plurality of acoustic sources (52) disposed on the blades (36-42) of the downstream row (18).

Abstract: A self-exciting optical strain sensor (20) includes dual parallel bridges (22,24) having parallel facing surfaces (32,34). Light energy (38) entering a Fabry-Perot cavity (36) formed by this surfaces (32,34) induces a periodic buildup and release of energy in the cavity (36) which is directly related to the natural resonant frequency of the bridges (22,24). Analysis of the intensity of light emitted (50) from the cavity (36) determines the bridge natural frequency.

Abstract: An electrical an (10) for the icing-susceptible stator vane stage (16) located in an air inlet section (12) of a turbomachine (not shown). A plurality of stator vanes (20) which are electrically isolated from a plurality of structural shrouds (30, 32) are grouped in one continuous, or a plurality of contiguous arcs about a fanshaft which is generally coincidental with the turbomachine's longitudinal axis (X--X). Low voltage alternating current is provided by an alternator (not shown). This current is directed through a plurality of electrical conductors (26) and is further distributed through each stator vane (20) which is either electrically conductive or employs an electrically conductive medium disposed proximate to an icing susceptible surface of an airfoil contour (21). The electrical current flow, which is generally directed in a radial orientation through each stator vane (20) causes a direct electrically-resistive heating effect to the airfoil contour surfaces (21) of the stator vanes (20).

Abstract: An impinging jet mixer 40 includes a central atomizer 42 for providing a conical fuel stream 50 and means 56, 58 for providing a plurality of intersecting gas jets 62, 66 which meet the conical fuel spray 50 at an interaction zone 64 spaced downstream of the atomizer discharge opening 70.

Abstract: A pneumatic pressure controller includes an actuator (50) and a throttling valve (12) for regulating a flow of gas (10). A pressure comparator (22) provides a modulated pressure signal (58) to the controller (50). The pressure comparator (22) includes an outlet orifice (70) for compensating at elevated supply pressures, P.sub.SUP.

Abstract: A segmented brush seal (10) having coaxial annular backing (20) and side (25) plates sandwiching a plurality of tightly packed, circumferentially arrayed bristles (30) which extend radially inwardly at a constant circumferential skew angle, and its method of manufacture, is disclosed. The side plate (25) has a plurality of radially inwardly extending tabs (32) each having a tab end (34) which extends proximate to an inner diameter (22) of the backing plate. The sandwiched plates (20, 25) and bristles (30) are welded together at each tab (32), wherein the resulting weld zone (50) lenghtwisely extends from the radially innermost tab end (34) to an outer circumferential weld (40) at the local bristle skew angle. The seal is then lengthwisely bifurcated through each weld zone (50) at the local bristle skew angle to produce the segmented seal (10).

Abstract: A bleed valve (20) includes a reciprocating sliding element (42) with a circular head (48) joined to an annular wall (50). An annular first chamber (52) defined by the wall (50), the head (48), and the central support (30) has a variable volume dependent upon the relative position of the sliding element (42). The valve (20) includes a housing (22) having a base (26) with first and second annular partitions (62,64) protruding from the base (26). An annular second chamber (66) is defined by the first partition (62), the platform (34) of the central support (30), the second partition (64), and the base (26). An opening (72) in the central support (30) connects the second chamber (66) in fluid communication to the first chamber (52). Control air supplied from an engine source flows through a first bore (78) into the second chamber (66) which is vented to ambient via a second bore (80). The first and second bores (78,80) have a primary and secondary metering orifice (84,86).

Abstract: An annular combustor liner (30) includes louvers (52, 54, 56, 70, 72) for inducing the formation of a single toroidal vortex (68) adjacent a domed upstream portion (34) of the liner (30).

Abstract: A spiral wound containment ring (b 20l ) is received within a radially inward facing channel (38) in an engine case (18).

Abstract: An annular support (22) accommodates differential thermal growth between first and second support rings (24, 26). The support (22) prevents relative axial, circumferential lateral and bending movement between the rings (24, 26), while allowing uniform differential radial expansion and contraction.

Abstract: A method for correcting a hot start condition in a gas turbine without requiring a complete shutdown and reinitiation of the startup sequence includes temporarily interrupting the flow of fuel to the engine for a brief period of time following detection of an impending hot start condition.

Abstract: Flow of cooling air to a thermal clearance control system in a gas turbine engine is selectably scheduled between a normal power level versus clearance schedule and an increased efficiency cruising schedule. Selection of the cruising schedule is accompanied by a limitation on the rate of engine power increase during the period when the cruise schedule is selected.

Abstract: A supersonic inlet flow duct (10) is provided with a pivoting bleed stability door (34) and biasing spring (42). The door (34) opens under the influence of increased static fluid pressure behind a shock front (24) which is displaced forwardly by a downstream pressure perturbation. The opened door (34) diverts portions (31, 44) of the inlet duct flow stabilizing the shock front (24a) and downstream shock train (25) within the duct (10) until the perturbation subsides.

Abstract: A method for preventing rubbing between a gas turbine engine rotor and surrounding annular shroud during transient changes in engine power monitors high rotor speed for determining the existence of a thermal mismatch between the rotor and shroud supporting turbine case (9). The method directs the cooling flow modulating valve (44) to substantially shut off the flow of cooling air to the case (9) for a period of time sufficient to allow the thermal mismatch to pass.

Abstract: An axisymmetric thrust vectoring exhaust nozzle includes a plurality of divergent flaps (30) each supported at the upstream end by a universal joint (32) and at the downstream end by a load link (34) connected to a unison ring (36) positioned by actuators (45).

Abstract: A method for enhancing the thermal response of the engine case and annular shroud during the transient response period following a step change in engine power provides for the temporary reduction or elimination of the flow of cooling air supplied to the engine case by the active clearance control system. An alternate method additionally substitutes a flow of relatively warm air to further increase the response of the case.

Abstract: A fan blade retention device includes a retaining flange (18) located aft of the blade fixing element (7). The flange (18) abuts an outwardly facing circumferential groove (13) located between the flange (18) and the female half of the blade fixing element (10). The groove (13) is large enough to allow the blade fixing element (7) machining tool to be removed. The fan blade (28) includes an extension (21) of the blade root (11) on the aft side of the blade (28). When the blade root (11) is fully received within the female half of the blade fixing element (10), the blade extension (21) spans the width (20) of the groove and contacts the flange (18), thereby preventing the fan blade (28) from traveling aft.

Abstract: A key-in-ignition warning switch (10) is integrally mounted within an ignition switch (11). The warning switch (10), positioned along the rotational axis (17) of the ignition switch (10), comprises an inner plunger (15), an outer plunger (16), a plunger spring (28), and a housing spring (31). As the ignition key (26) is inserted into the key cylinder (12), a linkage (14) between the key cylinder (12) and the warning switch (10) pushes against the inner plunger (15), which in turn pushes against the outer plunger (16). As the key (26) is inserted completely into the key cylinder (12), contacts (24,25) attached to the plungers (15,16) make contact with terminals (34,36) located within a terminal block (35) attached to the ignition switch (11). When both plunger contacts (24,25) and mating terminals (34,36) are in contact, the key-in-ignition warning circuit is completed, thereby enabling the associated warning devices.