Abstract: In an aspect, a method is provided for attenuating jet engine noise. Air velocity, adjacent to an inlet fan duct outer wall, is increased to a greater rate than typical velocity of an operational engine ambient inlet airflow, adjacent to the inlet fan duct outer wall. Boundary layer and associated turbulence is reduced or eliminated. Refraction and absorption of inlet sound into an acoustic liner is optimized. In an aspect, air velocity is increased by injecting air. In an aspect, air velocity is increased by exerting a suction force. In an aspect, a system is provided to attenuate jet engine noise. In an aspect, a fluid duct is provided opening to an inlet fan duct outer wall and to aft of a fan rotor.

Abstract: A system for jet engine noise control of a jet engine having a main jet stream exiting an exhaust nozzle and flowing along a jet axis includes a thermal acoustic shield directed at a non-zero angle relative to the jet axis. The thermal acoustic shield may be configurable about the main jet stream. The system may further include at least a fluidic chevron injected at a location relative to the nozzle exit for enhancing mixing in the main jet stream and creating a non-circular jet stream.

Abstract: A diffuser includes an opening along the diffuser wall for preventing or delaying boundary layer separation of the main flow. The opening may include a curved passageway having a curvature convex relative to the main flow for utilizing the Coanda effect. A gas turbine may include the diffuser with an opening and a centerbody with an opening, each for providing a secondary flow of fluid into the diffuser. The gas turbine may direct fluid from an upstream turbine stage to the opening. A steam turbine may include the diffuser and may situate the opening downstream the diffuser inlet but upstream the location of boundary separation.

Abstract: In an aspect, a method is provided for attenuating jet engine noise. Air velocity, adjacent to an inlet fan duct outer wall, is increased to a greater rate than typical velocity of an operational engine ambient inlet airflow, adjacent to the inlet fan duct outer wall. Boundary layer and associated turbulence is reduced or eliminated. Refraction and absorption of inlet sound into an acoustic liner is optimized. In an aspect, air velocity is increased by injecting air. In an aspect, air velocity is increased by exerting a suction force. In an aspect, a system is provided to attenuate jet engine noise. In an aspect, a fluid duct is provided opening to an inlet fan duct outer wall and to aft of a fan rotor.

Abstract: A system for jet engine noise control of a jet engine having a main jet stream exiting an exhaust nozzle and flowing along a jet axis includes a thermal acoustic shield directed at a non-zero angle relative to the jet axis. The thermal acoustic shield may be configurable about the main jet stream. The system may further include at least a fluidic chevron injected at a location relative to the nozzle exit for enhancing mixing in the main jet stream and creating a non-circular jet stream.

Abstract: A diffuser includes an opening along the diffuser wall for preventing or delaying boundary layer separation of the main flow. The opening may include a curved passageway having a curvature convex relative to the main flow for utilizing the Coanda effect. A gas turbine may include the diffuser with an opening and a centerbody with an opening, each for providing a secondary flow of fluid into the diffuser. The gas turbine may direct fluid from an upstream turbine stage to the opening. A steam turbine may include the diffuser and may situate the opening downstream the diffuser inlet but upstream the location of boundary separation.

Abstract: An active effective flow-through area control system includes an upstream wall-flow perturber and a downstream wall-flow perturber situated in an inlet region of an aircraft engine. The downstream wall-flow perturber is positioned downstream from the upstream wall-flow perturber. The upstream and downstream wall-flow perturbers are configured to generate and trap at least one region of separated, vortical flow in the airflow through the inlet region. A method, for actively changing an effective flow-through area of an inlet region of an aircraft engine, includes creating at least one region of separated, vortical flow in an airflow passage defined by the inlet region. The method further includes trapping the region of separated, vortical flow in the airflow passage. The region of separated, vortical flow partially obstructs a main inlet airflow.

Abstract: A non-intrusive method of monitoring the integrity of a rotating member comprising mounting at least one sensor in a stationary frame of reference in a casing over the rotating member, measuring the pressure field of the rotating member, comparing the measured pressure field with a corresponding reference pressure field, identifying variations in the measured pressure field, the variations indicative of a fault in the rotating member, and generating an output indicative of an identified fault.

Abstract: A non-intrusive method of monitoring the integrity of a rotating member comprising mounting at least one sensor in a stationary frame of reference in a casing over the rotating member, measuring the pressure field of the rotating member, comparing the measured pressure field with a corresponding reference pressure field, identifying variations in the measured pressure field, the variations indicative of a fault in the rotating member, and generating an output indicative of an identified fault.

Abstract: A surge condition in a stalled gas turbine engine is promoted by modulating a time-varying component of an operating parameter of the gas turbine engine, such as the fuel flow to the combustor plenum of the engine, substantially in phase with a time-varying component of the pressure in the combustor plenum, thereby allowing normal operation of the engine to resume during the surge condition by eliminating the stall-inducing agent.

Abstract: An acoustic duct such as a jet engine fan duct is lined with numerous peripherally spaced, longitudinally extending strips of sound-absorbing material which are effective to scatter spinning mode acoustic pressure fields to higher order, attenuating modes for improved noise suppression. These strips can be alternated with other strips having a different acoustical impedance, or combined with a longitudinally segmented treatment.