A test rig for LDV and seeding characterization for high speed turbomachinery application: experimental results

摘要

The accuracy and data rate of Laser Doppler Velocimetry (LDV) are strongly influenced by several parameters. To optimize measurements, a system for setting up the velocimeter, not influenced by the specific environment, is needed. It is necessary to choose several optical parameters, to evaluate insemination techniques (not influenced by specific flow fields) and to compare seeding performance in a right range of velocities. A supersonic wind tunnel was constructed, to evaluate the measurement LDV system in a range of velocities from 50 m/s to 450 m/s using various kinds of seeding. Tests were performed both in accelerating velocity zones and in the presence of shock waves. Comparative tests were made using suspension in water of various materials as seeding: Polystyrene (PSL), microballoons, four kinds of commercial aluminum oxide powder in distillate (pH = 6) and acid water (pH = 2), plus other oxides like TiO{sub}2 and ZrO{sub}2.