Full annulus URANS simulations are presented to investigate distortion phase shift in a single stage transonic fan. The fan is subject to a 90 degree sector inlet total pressure distortion. Simulation results are presented for choke, design, and near-stall operating conditions. Circumferential profiles of swirl, total pressure, total temperature, power, and phase shift are analyzed at 10%, 30%, 50%, 70%, and 90% span. Phase shift is a measure of the rotational translation of a distortion profile and is valuable for understanding the translational motion of distortion as it passes through the fan. At choke and design operating conditions the phase shift is positive in the direction of rotor rotation. At near-stall the phase shift is negative opposite rotor rotation for the outer 30% span. Local power reaches a maximum value, resulting in the generation of a uniform pressure region. This region causes increased distortion content in the near-stall case over a wide circumferential extent resulting in a negative phase shift.

Understanding distortion transfer and generation through fan and compressor blade rows is able to assist in blade design and performance prediction. Using full annulus URANS simulations, the effects of distortion as it passes through the rotor of a transonic fan at five radial locations (10%, 30%, 50%, 70%, and 90% span) are analyzed. The inlet distortion profile is a 90-degree sector with a 15% total pressure deficit. Fourier distortion descriptors are used in this study to quantitatively describe distortion transfer and generation. Results are presented and compared for three operating points (near-stall, design, and choke). These results are used to explain the relationship between inlet total pressure distortion, pressure-induced swirl, total pressure distortion transfer, total temperature distortion generation, and circumferential rotor power variation. It is shown that very large changes in pressure-induced swirl and distortion transfer and generation occur between near-stall and design, but only small changes are seen between design and choke. The greatest changes are shown to be near the tip. Local power variations are shown to correlate with total pressure distortion transfer and total temperature distortion generation.

An important consideration for fan and compressor design is quantifying distortion transfer and generation blade row by blade row. Detailed information about the magnitude of distortion and the shape of the distortion profile and how it changes through blade rows increases the understanding of flow physics and helps predict aerodynamic performance. Using full annulus URANS simulations, this paper analyzes what happens to distortion as it passes through the rotor and stator blade rows at 10%, 30%, 50%, 70%, and 90% span. Fourier distortion descriptors are used in this study to quantitatively describe distortion transfer and generation. With these descriptors, evidence of pressure-induced swirl is shown at the fan inlet. It is also shown that although there is very little distortion at the 10% span of the inlet, after passing through the rotor blade row the 10% span has the greatest amount of total pressure and total temperature distortion. This radial migration of distortion is attributed to the high hade angle of the hub. The total pressure and total temperature profiles have significant circumferential phase shifts after passing through the rotor and slight phase shifts after passing through the stator. In general, the calculated phase shifts are greatest at the 10% and 90% spans, the nearest locations to the hub and the tip clearance gap, respectively.