Swirling flow heat transfer and hydrodynamics in the model of blade cyclone cooling with inlet co-swirling flow

Abstract Swirling flow heat transfer and hydrodynamics were studied experimentally in the round passage, simulating the blade cyclone cooling. The smooth passage with one- and two inclined-tangential flow supply and the additional co-swirling flow at the inlet is considered. The Reynolds number, based on the average axial speed and passage internal diameter was ranged from 40 000 to 108 000, the co-swirling flow ratio Gd/GƩ was varied from 0 to 0.23. At Gd/GƩ ≤ 0.11 in the passage with one tangential slot the co-swirling flow influences weakly on the heat transfer enhancement and pressure drop ratio. In the passage with two slots, the Nud/Nud0 ratio drops down immediately from Gd = 0, moreover in this case the heat transfer is about 20% lower than that in the passage with one slot. At the identical total pressure in front of the passage, both schemes are comparable in terms of the total pressure losses. When pressure losses in swirl generators are taken into consideration at Gd = 0 two slots scheme demonstrates a greater Reynolds analogy factor than that for the one slot configuration. Also in terms of this factor, the two slots scheme looks better than the continuous and broken V-shaped ribs commonly used in the internal blade cooling. At Gd/GƩ > 0.5 - 0.6, the co-swirling flow reduces the heat transfer ratio and Reynolds analogy factor. In the passage with one inlet slot in the limited area of Gd/GƩ ratio, the pressure losses in the 90° exit bend are lower compared with the axial flow in the bend. In the passage with two slots in the entire range of Reynolds number, these losses are below those if the axial flow exists in the bend. This very attractive feature can be employed in the blade cyclone cooling design when the coolant discharges into the trailing edge area.