Dynamic analysis of two-wheel bleed air environment control system of the aircraft

Abstract

Dynamic analysis of the Environmental Control System (ECS) is essential for enhancing system performance and control. This study presents the dynamic modeling and analysis of a two-wheel bleed air ECS for aircraft, developed using the ECS library in Dymola, a commercial 1-D dynamic simulation software based on the Modelica language. The model represents a high-pressure water separator two-wheel bleed air ECS and focuses on the transient behavior of its key components. The analysis captures the dynamic response in terms of hot-side heat flow rate for the compact heat exchangers, outlet temperatures on the hot and cold sides of the heat exchangers, and the outlet temperature of the cold air unit (CAU). Additionally, corrected flow and corrected speed of the CAU, along with shaft power, torque, and angular speed, were investigated. To ensure reliability, a separate steady-state analysis was conducted using MATLAB, as dynamic studies of such systems are limited in the literature. The simulation results show strong agreement with the steady-state MATLAB analysis, validating the accuracy of the developed model. System-level responses were obtained at approximately 26 s, 52 s, and 78 s for shaft mass moments of inertia of 0.01 kg m2, 0.02 kg m2, and 0.03 kg m2, respectively. These results demonstrate the influence of shaft inertia on dynamic performance. The developed dynamic model provides a valuable tool for system-level analysis during the early design phase, particularly when experimental data are not available.