Simulation of Helmholtz Resonance Effects in Aircraft ECS

Abstract

Helmholtz resonators are closed volumes that are connected to pipes. They exhibit a pronounced resonance frequency, where small boundary pressure excitations in the volume or the environment lead to large mass flow excitations in the pipe. Aircraft have a topology similar to Helmholtz resonators, the closed volume is represented by the cabin, while the pipe is represented by the Environmental Control System. Some discrepancies appear due to the non-zero mass-flow or friction effects in aircraft ECS. Preliminary analyses showed, that resonance effects might still appear in spite of this differences. A detailed aircraft-level model of an ECS is presented in the equation-based modelling language Modelica. In simulations of this model, the appearance of Helmholtz resonance effects in aircrafts could not be confirmed.