An assessment was conducted to determine the suitability of subscale, low-Mach-number, particle image velocimetry (PIV) testing and computational fluid dynamics (CFD) analysis to evaluate swirling flow downstream of a swirl pattern generation system composed of continuous patterns of turning vanes. Successful demonstration of the evaluation methods required acceptable comparison of the PIV and CFD to an independent five-hole probe measurement performed at the design Mach number and full-scale geometry. The focus of the investigation was on direct comparison of flow angles and flow features one diameter downstream of the swirl pattern generator. Both the subscale PIV and the CFD provide adequate representation of the swirling flow produced by the full-scale generator. The subscale PIV and CFD may be used to predict the performance of the full-scale swirl pattern generator and allow for inexpensive testing and analysis to be performed during the design process, thus improving the accuracy of generating a desired swirl pattern.
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.
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