A Numerical Simulation of the Effects of Swirling Flow on Jet Penetration in a Rotating Channel

Abstract

The hydrodynamic effects of a jet in a swirling cross-flow problem, which is related to gas turbine blades film cooling, were numerically simulated using large eddy simulation with artificial inflow boundary conditions. The purpose of this study is to investigate the effects of swirling flow on a jet effusing from an inclined hole in a rotating channel. The finite volume method and the unsteady PISO algorithm were applied on a non-uniform staggered grid. The work is naturally divided into two main parts. The first part (the swirl flow generator), is a channel rotates axially to generate a turbulent swirling flow at different values of swirl number (SN) of 0.0, 0.15, 0.3, and 0.5 while the second part (test section), is a channel rotating about a parallel axis to investigate the interaction of a square jet with the turbulent swirling flow, generated by the first part, for the prediction of the film cooling under rotating conditions. Four different values of rotation number (Ro) were applied to the test section. The air jet was injected at 30 deg in the streamwise direction, at a velocity ratio of 1.0 and a jet Reynolds number of 4,700, based on the hole width and the jet exit velocity. It was found that the swirling flows primarily displayed the velocity profile of a forced vortex. Weak reverse flow was observed near the main vortex core, which moved in the direction of the swirl and deformed the kidney shape of the Counter Rotating Vortex Pair. As SN increases (SN > 0), the jet trajectory twists in an increasingly x-axis direction due to the centrifugal force effects of the swirl flow, and shifts from the centreline of the channel Flow Turbulence Combust to the right-hand side (Z/D = + 1.5). Also, it was shown that rotation has a strong impact on the mixing behaviour and film cooling effectiveness. Finally, it was concluded that the film cooling decreases rapidly as SN increases.

A numerical study of rotation effects on jets effusing from inclined holes into a cross-flow

“…It is well know that there are substantial differences between the behaviour of film cooling in a rotating environment and film cooling under stationary conditions. This study is a continuation of the work of Alzurfi and Turan [16] who investigated the effects of swirling flow on film injection inside a rotating channel at VR of 1.0. In the present study, multiple jet injections at a VR of 0.5 were simulated over a flat plate employing periodic boundary conditions in the spanwise direction.…”

“…The constant density term has no influence on flow dynamics and can be incorporated into the pressure gradient term (P eff =p − 1 2 ρ o 2 r 2 ). [16] On the other hand, the temperature differences of the jet into cross-flow cause density variations, thus, the ideal gas law for an incompressible flow was used in order to compute the spatial and the temporal density variations throughout the computational domain every time step except the boundary values.…”

“…In the cross-flow block, grid refinement was performed in X-and Y-directions while approaching the jet exit, using the algebraic stretching function, used by Alzurfi and Turan. [16] Table 1 shows the grid points used in each direction in the cross-flow and the jet flow regions. Although there are small discrepancies as we move away from the jet exit, our results predict the trends much better than the computational results of Ajersch et al [2] In Figure 4, the profiles of centreline and spanwise-averaged film cooling effectiveness were compared with the LES results of Farhadi et al [14] for the condition of Ro = 0.0.…”

“…In the present study, multiple jet injections at a VR of 0.5 were simulated over a flat plate employing periodic boundary conditions in the spanwise direction. The study focuses on the differences between the behaviour of film cooling interaction in a channel as reported in the work of Alzurfi and Turan [16] regarding film cooling behaviour over a flat plate. Additionally, it focuses on the aspects of numerical investigations concerning the effects of Coriolis and buoyancy forces induced by rotation.…”

“…Additionally, it focuses on the aspects of numerical investigations concerning the effects of Coriolis and buoyancy forces induced by rotation. The same in-house code, developed by Alzurfi and Turan, [16] was used to compute the rotational film cooling using LES method.…”