Abstract
In order to carry out reliable LES or Helmholtz solver computations in aeronautical combustion chambers, it is crucial to impose the right boundary conditions at both inlet and outlet of the combustion system. This means providing acoustic boundary impedances that take into account all the stages in compressors and turbines. This study is a follow up of works where the boundary condition were derived from the isentropic and isenthalpic Linearized Euler Equations. Specific terms are added to the quasi-1D LEE in order to account for enthalpy jumps induced by the rotor stages of the compressors and turbines. This system of equations also accounts for the entropyacoustic coupling since, in addition to the continuity and momentum equations, the entropy equation is also considered. The numerical implementation is validated by comparing the numerical results with analytical solutions in several model problems. The effective impedance of the inlet air-circuit of an actual helicopter engine is then computed in order to illustrate the potential of the method as well as the importance of the rotor terms added.