Flow and heat transfer measurements inside a heated multiple rotating cavity with axial throughflow

This thesis discusses experimental results of measurement of heat transfer and velocity flow in a heated multiple cavity test rig with axial throughflow. Of particular interest are the internal cylindrical cavities formed by adjacent discs and the interaction of these with a central axial throughflow of cooling air. Tests were carried out for a range of non-dimensional parameters representative of gas-turbine high pressure compressor internal air system flows (ReF up to 5x106 and Rez up to 2x105). One configuration of the test rig was tested in the course of the reported study (Build 3) and test data from a previous rig configuration (Build 2) were processed, analysed and compared with the tested data. The most significant difference between the two builds of test rig was the size of the annular gap between the (non-rotating) shaft and the disc bores. Build 3 had a wider annular gap ratio, dh/b=0.164, while Build 2 featured a gap ratio of dh/b=0.092. Heat transfer data were obtained from thermocouples and a conduction analysis. Heat transfer results show differences between the versions of the rig, with the higher Nusselt number values in Build 3 attributed to the wider annular gap allowing more of the throughflow to penetrate into the cavity compared to Build 2. An attempt is made to correlate the average disc Nusselt numbers and this indicates the existence of different regimes. A two-component Laser Doppler Anemometry system was used on both rigs to measure cavity axial and tangential velocity components. Optical access in Build 3 also allowed for measurement of radial velocities. The axial and radial velocities inside the cavities are virtually zero. The size of the annular gap between disc bore and shaft has a significant effect on the radial distribution of tangential velocity. An analysis of the frequency spectrum obtained from the tangential velocity measurements shows evidence of periodicity in the flow consistent with the current understanding of the flow structure in a heated rotating cavity with axial throughflow.