Effect Of Entrance Geometry and Rotation On Heat Transfer In A Narrow (AR=1:4) Rectangular Internal Cooling Channel

This paper studies the effect of entrance geometries on the heat transfer and fluid flow in a narrow aspect ratio (AR=1:4) rectangular internal cooling channel, representative of a leading edge of a gas turbine blade, under rotating condition. Numerical simulations are performed to understand the role of the rotation generated forces on the flow for different entrance geometries representative of those encountered in practice. Three different entrance geometries are tested: a S-shape entrance, a 90 degree bend entrance and a twisted entrance that changes its aspect ratio along its length. Numerical simulations are run at a constant Reynolds number (Re =15000), for a range of rotation numbers (Ro =0-0.2) and density ratios (DR =0-0.4). Detailed heat transfer coefficient data at the leading and trailing walls are presented along with streamline profiles at different cross sectional planes that provide an insight into the flow field. It is seen that the entrance profile upstream of the actual test section is significantly different for the different entrance geometries, and has a significant impact on the rotation generated secondary flows. Non-uniformity in flow distribution at the exit of entrance geometry is small for the S-shape entrance while the non-uniformity is prominent at the exit of the changing AR entrance geometry. The entrance effect dies down as the flow progresses further downstream inside the cooling channel and the rotation effect becomes dominant.