Experimental and numerical investigation of flow structure and heat transfer in gas turbine HP compressor secondary air systems

With the continuing growth of the air traffic sector and a drive towards increasinglyefficient aero engines the overall pressure ratio of such engines is set to climb. As a consequence, blade tip clearances will become proportionally larger as blade size decreases. Accurate sizing of the tip clearance is dependent on knowledge of the radial growth of the compressor discs, which in turn is dependent on their radial temperature gradient. Currently, 2D thermo-mechanical models based upon empirical correlations and scaling laws are used to predict this radial growth and the temperature increase in the secondary air system. These require knowledge of the buoyancy-induced flow that occurs in heated cavities between adjacent co-rotating discs. This thesis presents experimental and numerical results of the heat transfer and flow structure of a buoyancy-induced rotating cavity flow field undertaken using the University of Sussex TFMRC Multiple Cavity Rig. This rig simulates the rotating components of a gas turbine secondary air system of a high pressure compressor. The objective is to gain a deeper understanding of the flow mechanisms operating within a rotating cavity at low Rossby numbers, representative of non-dimensional engine conditions and demonstrate that the shroud is the dominant source of heat transfer to the axial throughflow. The working conditions cover the range: 1.1×105