EULER-LAGRANGE METHOD FOR NUMERICAL SIMULATION OF WATER DROPLET-LADEN COMPRESSOR FLOWS

摘要

To assure a safe operation of aero-engines in wet atmospheric conditions, the effects of water ingestion need to be fully understood and tested. In that point of interest the influence of water droplets on the flow characteristics in the compressor is mainly focused. Numerical simulation methods may be of great use in that case to examine in more detail the two-phase flow in compressor stages. Concerning this matter, a FORTRAN source code for the dispersed phase has been developed at the Laboratory of Turbo Machinery at the Helmut Schmidt University (University of the Federal Armed Forces), Germany, using the Euler-Lagrange method for the simulation of water droplet motion under high speed conditions with the continuous flow in turbo compressors. Implemented models consider droplet phenomena including turbulent dispersion, deformation, flow induced secondary breakup as well as splashing on wall surfaces. The source code communicates with ANSYS CFX 13.0 flow solver by the embedded user subroutine interface, at which readout of continuous phase data and input of disperse phase data using source terms is proceeded. In consequence fully coupled calculations are enabled by what the disperse phase may take influence on the flow pattern of the continuous phase. Due to the segregated computation the memory of the source code itself remains independent and offers advantages in modeling droplet breakup when memory may be dynamically allocated according to the numbers of droplets generated. Both the solver of the motion equations and the implemented models demonstrate their qualities in stability, efficiency and flexibility. In the test facility at the Laboratory a linear axial compressor cascade with water droplet loading has been investigated. For validation reasons the experiments were simulated numerically.