Effects of Swirl Velocities From Fan Assemblies Mounted on Lifting Surfaces

Abstract

The penetration of a jet of fluid into a traversal moving stream is a basic configuration of a wide range of engineering applications, such as film cooling and V/STOL aircrafts. This investigation examines experimentally the effect of blowing ratio of fans in crossflow, and numerically, the effect of the swirl velocity of jets in crossflow, downstream of the injection hole. The experimental results indicated an agreement with typically straight jets in crossflow (no vorticity), illustrating that the trace of the jet, remains close to the wall and subsequently enhance cooling at low blowing ratios in the case of turbine blade applications. However, the rotation of the jet results in an imparity between the two parts of the counter rotating vortex pair and as a consequence, the injected fluid not only bends in the direction of the main stream but also diverts in the direction of the rotation in order to conserve its angular momentum. The induction of the swirl velocity on the injected jet destructs one of the two parts of the kidney vortex, which entrains fluid from the crossflow to the jet promoting the mixing between the two fluids while the trace of a swirled jet remains closer to the wall downstream of the injection hole. Finally, the use of contrarotating jet or fan configurations reduces the wall shear stress in a very great extent, leading to better thermal protection of turbine blades, as well as cancels out the yaw torques of each fan separately, resulting in better flight control of typical lift surface.