Abstract: A computer-implemented model of fan section of a gas turbine engine accounts for the turbulence in the gas flow emanating from the rotor assembly and impinging upon an inlet to the stator vane cascade. The model allows for user-input variations in the sweep and/or lean angles for the stator vanes. The model determines the resulting acoustic response of the fan section as a function of the turbulence and the lean and/or sweep angles of the vanes. The model may be embodied in software that is rapidly executed in a computer. This way, an optimum arrangement in terms of fan noise reduction is quickly determined for the stator vane lean and sweep physical positioning in the fan section of a gas turbine engine.

Abstract: A stator assembly for reducing noise in the outermost portion of the working medium flow path is disclosed. Various construction details are developed which relate to the reduction in noise within the outer twenty percent (20%) of the working medium flow path. In one particular embodiment, an annular channel extends rearwardly from a location between the blades and the vanes for capturing a significant portion of the wake turbulent flow from the tip region of the rotor blades. The annular channel is bounded by a pair of circumferentially extending walls, at least one of which has acoustic treatment to absorb tonal and broadband noise.

Abstract: A stator assembly for reducing noise in the outer most portion of the working medium flow path is disclosed. Various construction details are developed which relate to the reduction to noise within the outer twenty percent (20%) of the working medium flow path. In one particular embodiment, the number of radially extending surfaces in the outermost portion of the working medium flow path is reduced.

Abstract: Noise is reduced on an aircraft engine of the type having aft mounted propeller blades 10 which pass through exhaust gas streams 20 expelled from circumferentially spaced nozzles 14. The nozzles 14 are rotated, or the exhaust flow deflected, such that the high velocity exhaust streams 20a expelled from the nozzles 14 are directed away from their normal axial direction to impact the blades 10 at the same relative angle of attack 36a as the relative angle of attack 34 of the low velocity ambient air stream 22 thereby reducing fluctuations in blade lift and the associated noise.

Abstract: A prop-fan of the type having a high solidity factor (1 or greater) near the root fairing to a lower solidity factor (less than 1) near the tip and operable over a critical Mach No. range is designed for sound suppression by contouring the tip so that its sweep and sweep distribution of the leading and trailing edge bears a judicious relationship with the Mach surface. This feature is obtainable by designing the planform from a prescribed linearized or non-linearized acoustic theory and tailoring in the sweep so that the leading and trailing edges fall behind the Mach surface.

Abstract: A prop-fan of the type having a high solidity factor (1 or greater) near the root fairing to a lower solidity factor (less than 1) near the tip and operable over a critical Mach No. range is designed for sound suppression by contouring the tip so that its sweep and sweep distribution of the leading and trailing edge bears a judicious relationship with the Mach surface. This feature is obtainable by designing the planform from a prescribed linearized or non-linearized acoustic theory and tailoring in the sweep so that the leading and trailing edges fall behind the Mach surface.