Instrumentation

Fundamental measurements were performed with both 2D and 3D pneu­matic probes in the axial gaps between the blade rows, and with surface pres­sure tappings at the casing and on the vanes. In addition to that, a comprehen-

Figure 2. Single sensor dynamic pressure probe (left), dynamic pressure transducer at the casing (center and right)

sive analysis of the unsteady ft>w field was carried out. Field traverses with high resolution both in space and time were performed using single sensor dy­namic pressure probes. The probe shown in Fig. 2 (left hand side) was devel­oped and manufactured at the Institute of Jet Propulsion and Turbomachinery. The head diameter is 2 mm, and the probe is equipped with an Entran EPIH – 112 fast response semiconductor pressure transducer. It is supplied by constant current and calibrated by an independent variation of pressure and temperature. The approximation of the characteristics is realized by two-dimensional poly – noms (Maass, 1995). Additional investigations with fhsh mounted dynamic pressure transducers at the casing above the rotors show the effects on the tip clearance ft>w. One Kulite XCP-062-25D fast response semiconductor pres­sure transducer (Fig. 2 right hand side) is mounted at different axial positions of the casing element shown in Fig. 2 (center). The circumferential traverse of the element enables field measurements with a resolution of 550 (R3) to 600 (R1) measuring points.