3 Data Structure And Analysis

To investigate the effects of rim seal purge flow on the development of secondary flows and heat transfer along the endwall of a turbine, an experimental research program was performed in the Purdue Low-Speed Research Turbine for a range of seal flow conditions and vane index positions. Velocity fields developed within the intra-stage space were measured, ensemble averaged, assessed for significance, and then resolved into field representations of velocity magnitudes, velocity vectors, and vorticity magnitudes.

The primary parametric variables for this study are seal flow rate, turbine stator vane position, and turbine rotor blade position. The seal flow rate determines the radial momentum which the seal flow carries into the mainstream flow, and thus is indicative of the depth of the penetration of the seal jet and subsequent boundary layer disruption. The stator vane position determines how close the vane wake structures pass relative to the measurement plane above the seal. Strong wake vorticity convected with the mainstream flow can be expected to interact with the emergent seal flow. The rotor blade position relative to the measurement plane governs the strength of the upstream propagating potential field generated by the rotor. This potential field can be envisioned as a sinusoidal spatial variation of pressure anchored with a maximum at the rotor blade leading edge stagnation point and rotating with the blade. The streamwise pressure gradient associated with this potential field can be expected to selectively retard low momentum regions of the flow near the endwall and associated with seal flow structures.

Particle Image Velocimetry measurements were taken at four different vane positions, ten different rotor positions, and two different flow rates. Additional data were acquired at a third, intermediate flow rate for the vane relative position designated as Plane A. The vane relative plane designations are shown in Figure 2.15. The total data matrix of Table 3.1 presents 90 data sets each of a radial-axial measurement plane with 3844 vectors, of which a limited amount are rejected based on the analysis acceptance criteria.

Table 3.1 PIV Data Matrix.

Vane Position ^

0 0

Post a comment