Abstract
Large eddy simulation (LES) and Reynolds averaged Navier-Stokes simulation (RANS) of leakage flow in straight-through and stepped labyrinth seals were performed in order to compare their performances in sealing the secondary flow passage of the gas turbine based on the respective discharge coefficients. The results indicate a 17.8% higher leakage prevention performance for the stepped seal relative to that of the straight seal. Further, while the LES predicts an ~7% reduction in the discharge coefficient due to shaft rotation, this effect is underestimated by the RANS. Moreover, the LES correctly predicts a laminarized flow pattern in the clearance, whereas the RANS overestimates the turbulence kinetic energy. In addition, a turbulence kinetic energy spectrum analysis was performed based on the vorticity at selected points in order to identify the flow structure that has a dominant influence on the oscillation of the discharge coefficient. This analysis also enabled identification of the changes in the flow structure due to shaft rotation.
Highlights
Strong viscous resistance continues to occur inside the vortex, which rotates at high speed, greatly affecting the dissipation of kinetic energy and flow resistance of the fluid passing through the labyrinth seal structure
Flowsimulations structures, and compare them with labyrinth seal,values, (ii) the stepped which the stepped structure was added to experimental k-epsilonlabyrinth (RANS) seal andinLES
Simulations of (i) the straight through the casingseal, to obtain anstepped additional reduction relative was to that of the labyrinth (ii) the labyrinth seal in discharge which the coefficient stepped structure added to straight-through labyrinth seal, andreduction (iii) the stepped labyrinth seal under the conditions of the casing to obtain an additional in discharge coefficient relative to that of the astraight-through stationary or rotating shaftseal, were conducted
Summary
Large eddy simulation (LES) and Reynolds averaged Navier-Stokes simulation (RANS) of leakage flow in straight-through and stepped labyrinth seals were performed in order to compare their performances in sealing the secondary flow passage of the gas turbine based on the respective discharge coefficients. A turbulence kinetic energy spectrum analysis was performed based on the vorticity at selected points in order to identify the flow structure that has a dominant influence on the oscillation of the discharge coefficient. This analysis enabled identification of the changes in the flow structure due to shaft rotation.
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