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The transfer of stationary circumferential inlet distortion through a rotor is analyzed using unsteady semiactuator disk cascade theory. This method models the blade cascade as one-dimensional wave guides and describes the transmission characteristics of a rotor to be a function of the distortion wave length and the length of the rotor chord, as well as the normal design parameters. Two parametric studies on the response of a loaded rotor to inlet distortions are done for a single rotor operating at off design conditions and a number of rotors operating at their design points. Fourier series representations of arbitrary distortion wave shapes are used for comparison with experimental data.

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The transfer of stationary circumferential inlet distortion through a rotor is analyzed using unsteady thin airfoil cascade theory which can account for the distortion wave length, rotor chord and cascade solidity. The model consists of representing each blade by a moving doublet filament of finite length immersed in a compressible stream containing a velocity distortion. The study is limited to an unloaded, flat plate rotor. This model provides a new physical interpretation for the flow adjustments observed ahead of the rotor and for the generation of sound when an inlet distortion is imposed. The analytical results show the influence of solidity and other rotor design parameters on the distortion transfer. They are found to approach the semi-actuator disk results as the solidity tends to infinity.

The generation of multiple pure tones in Supereonic fans is discussed. The theoretical results of Kurasaka are reviewed and compared with experimental data obtained on a 36" diameter, 1550 ftlsec, 1.6 pressure ratio fan. Detailed measurements on bow shock locations taken with pressure transducers indicate that blade to blade discrepancies are the source 01 MPT eeneration. The paper presents Some experimental results on an attempt to reduce the shock strength, and subsequently the MPT's, through blade modifications. Other attempts at reducing the MPT's through wall treatment, high inlet flow mach number, acoustically treated splitters -are discussed. Experimental data is presented on the validity of these noise reduction methods.