A Study of the Secondary Flow in Aircraft Engine Compressor Disks using Computational Fluid Dynamics

Abstract

The compressor disks of an aircraft engine which operate at very high rotational speeds are exposed to significant temperature gradients. These temperature gradients induce thermal stresses into the rotating disks which along with the existing dynamic stresses significantly reduce their useful field life. Hence it becomes essential to reduce the disk temperature gradients by utilizing a certain percentage of the compressor core flow known as the secondary flow for either heating or cooling these rotating parts. But this extraction of the compressor core flow results in a higher engine fuel burn for a given engine thrust.  Hence the need arises for a better utilization of the secondary flow to effectively reduce the temperature gradients of the rotating compressor disks. As the secondary flow thermal phenomenon  inside the rotating compressor disk cavities is very complex and due to it’s direct impact on the  life expectancy of the disks it becomes critical to understand it’s  thermo-fluid behaviour by the effective use of available Computational Fluid Dynamic tools. In the current study the secondary flow through the compressor disk cavities is simulated using Computational Fluid Dynamics (CFD) and the results are analysed and reported. The analysis of these results help in a better understanding of the distribution of the flow and the variations of the thermal fluid parameters across the secondary flow system. These results are also later used as thermal boundary conditions in the Finite Element model (FEM) to study the impact of various engine design parameters on the disk temperature gradients after being validated by the experimental results. The findings from this computer aided investigation offers support in make design improvements aimed at lowering the disk temperature gradients and enhancing their useful field life