Two corotating discs and a peripheral shroud can be used to model the cavity created by compressor or turbine discs in a gas-turbine engine. This thesis describes an experimental investigation into the effect of geometry on the flow and heat transfer in a rotating cavity for three cases: radial outflow, radial inflow and axial throughflow. The study included flow visualisation, pressure and heat transfer measurements. The experimental rig comprised two discs of outer radius 381 mm and a peripheral shroud; the axial distance between the discs was varied up to 171 mm. Air entered or left the cavity through either holes, of outer radius 38.1 mm, in the centre of the discs, or through discrete holes in the shroud. The cavity was rotated up to 2000 rev/min with flow rates of up to 0.2 kg/so One disc could be radiantly heated to produce a temperature profile that increased with increasing radius; the maximum front face temperature was 100°C. Flow visualisation, for the axial throughflow case, was also conducted on a second smaller rig. In a rotating cavity with a radial outflow, it was shown that whilst cobs at the inner radii do not significantly affect the flow structure, relative to the plane-disc cavity, protrusions at the outer radii result in the flow becoming nonaxisymmetric; there was also axial flow in the core. Heat transfer measurements, using the transientanalysis technique, for the cavity with cobs but without protrusions, were reasonably predicted by the solutions of the nonlinear integral equations. For the radial inflow case, radial fins attached to one disc or de-swirl nozzles at inlet to the cavity were both shown to be effective in reducing the pressure drop across the cavity. Measured pressure drops agreed reasonably well with the linear and nonlinear solutions of the momentumintegral equations. Comparison between measured values, using the transient analysis technique, and predicted values of the Nusselt number in a cavity with cobs showed reasonable agreement, provided that Ekman-layer flow occurred. In a rotating cavity with an axial throughflow, flow visualisation revealed that the nonisothermal nonaxisymmetric flow structure differed significantly from the axisymmetric flow in an isothermal cavity. Thermally insulating cobs were shown to affect the flow structure, especially when the axial distance between the cobs was small. Heat transfer measurements, using fluxmeters, showed that the Nusselt number increased with both rotational speed and flow rate. The results were also consistent with measurements obtained from other experimental rigs.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:605161 |
| Date | January 1988 |
| Creators | Farthing, P. R. |
| Publisher | University of Sussex |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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