The Design and Evaluation of Screens to Provide Multi-Cycle 20% Amplitude Sinusoidal Variations in the AFRF Rotor Inlet Axial Velocity Component.

摘要

This memorandum describes the results of an effort initiated in April 1973, whose objective was to provide new disturbance-producing screens for use in the Axial Flow Research Fan (AFRF). The performance of the screens originally developed for use in this facility was characterized by the generation of axial velocity profiles whose maximum and minimum values differed from the mean value by approximately 6% and by the presence of harmonics whose amplitude was on the order of 20% of the amplitude of the fundamental. The new screens were designed to produce axial velocity profiles with variations about the mean value of plus or minus 20%, and care was exercised in the selection of materials and in the assembly of the screens in an attempt to reduce the amplitude of the other harmonics relative to the amplitude of the fundamental. Results are presented for one-, two-, four-, six-, nine-, and fifteen-cycle screens which show that the design objectives were met to within a few percent. In addition, appendices are included which: (1) describe the performance characteristics of the original one-cycle screen, (2) define a modified approach and the design characteristics adopted to permit fabrication of twelve- and fifteen-cycle screens, and (3) contain design charts that are useful in the selection of the screening materials required in a development program of this type. (Author)