Disk heat transfer in a rotating cavity with an axial throughflow of cooling air

Abstract A heated, rotating cavity with an axial throughflow of air is used as an experimental model for a pair of gas turbine, high-pressure compressor disks. Tests were carried out on a single rotating cavity comprising two disks of radius b = 0.4845m, bounded at the circumference by a carbon fiber shroud. Experiments were conducted with and without a heated shroud and for the range of parameters: 0.03 ≤ βΔT ≤ 0.3; 2 × 103 ≤ Rez ≤ 16 × 104 and 2 × 105 ≤ Reφ ≤ 5 × 106; for cavity gap ratios G = 0.13 and 0.36, and a constant value of inlet radius ratio of a/b = 0.1. Measurements were also made of the air temperature inside the cavity by three thermocouple probes. The heat transfer from the disks was measured using thermopile flux meters. The measurements of cavity air temperature and cavity heat transfer were used to estimate the fraction of the central throughflow entering the cavity. This shows only a slight dependence on the gap ratio. For Ro 10, this decreases to around 10 percent. Two mechanisms appear to operate in influencing the heat transfer. Firstly, heating of the air inside the cavity destablizes it and convection occurs under the action of rotationally induced buoyancy forces. Secondly, the central throughflow encourages mixing with the cavity air, which can either affect the heat transfer directly (as, for example, at the inner radii of the disks) or indirectly through the action of vortex breakdown. For the smaller gap ratio cavity, rotational effects become increasingly important toward the outer radius across a wide range of Rossby numbers. For the wider gap ratio cavity, this is restricted to a narrower range of Ro. In the region 4 ≤ Ro ≤ 5, the gap ratio plays a crucial role in affecting the disk heat transfer. At smaller values of Ro, where a significant fraction of the throughflow enters the cavity, the disk heat transfer rate does not appear to be affected by the gap ratio. At larger values, increasing the gap ratio also increases the heat transfer.