Aerodynamic and Acoustic Investigations of Axial Flow Fan and Compressor Blade Rows, Including Three-Dimensional Effects

This report presents the results of a program designed to study the influence of three-dimensional effects on the aerodynamics and acoustics of axial flow fans and compressors. To avoid numerical solutions of the full nonlinear three-dimensional equations, a linearized analysis is employed. This is first applied to the determination of the steady loading on a three-dimensional annular blade row with a prescribed chamber line in inviscid compressible flow. The blades are represented by pressure dipole singularities in a lifting-surface formulation, and a collection procedure is presented for inverting the resulting integral equation. Comparisons are presented between the present results and those of two-dimensional strip theory and an inverse three-dimensional theory. Next the analysis is extended to the case of unsteady flow through the rotor, such as might be caused by inflow distortion or blade flutter. The integral equation for this case is somewhat more complicated, but appears to be solvable by a suitable extension of the procedure developed in the steady problem. Finally, further comparisons are presented between a theoretical model of rotor-stator interaction noise developed under a previous program and a current series of measurements made in an annular cascade facility. (Author)