PROBE BLOCKAGE EFFECTS IN TRANSONIC FLOW THROUGH GUIDE VANES, MEASURED IN A LOW PRESSURE-STEAM TURBINE

摘要

Probe blockage effects are presented for transonic flow through a guide vane row in a three-stage low-pressure (LP) steam model turbine. Accurate experimental data from measurements in a transonic turbine are needed for the verification of CFD results. The accuracy of static pressure measurements in transonic turbine stages is severely affected by the pneumatic probe, which disturbs the surrounding flow-field. These disturbance effects are significantly present during measurements inbetween turbomachinery blade rows. Therefore, the phenomenon associated with mis blockage effect must be investigated and determined. The aim is to measure the blockage effects on the blade passage flow, which are produced by a pneumatic pressure probe immersed in the flow between two adjacent blade rows. In order to measure these effects, two stator blades are instrumented with static pressure taps along the blade chord, as well as along the blade span. During the investigations, the radial and circumferential positions of the probes relative to the blade channel are varied. Pressure probe readings of two four-hole wedge probes with different stem diameters and a five-hole cone probe are compared as well as correlated to the static pressure readings of the stator blade pressure taps Finally, the apparent deviations of the different readings are discussed.