Air cycle and environmental control system application

An aircraft environmental control system (also called air generation unit or air cycle) consists of turbomachinery and heat exchangers.

  • The turbomachinery, often a centrifugal or mixed flow compressor and one or two radial inflow turbines, is mounted in a single shaft, which can also drive a ram air fan, or be itself driven by a motorized cabin air compressor.
  • The heat exchangers are used to dissipate heat from compressed fresh air to some heat sink, or to facilitate the extraction of water. The extracted water, typically upstream of the (last) turbine stage, can be injected into ram air, to intensify the heat transfer. This refrigeration cycle uses air as working fluid.

The transient behavior of an air cycle can be simulated using Environmental Control Library. This library provides all required component and thermodynamic property models and can be used in any design phase, ranging from early design for instance to the development of automatic controls and integration activities (e.g., hardware-in-the-loop in verification and validation).

Functionality to run air cycle models in pure steady-state for very early design is available for experienced users using Jet Propulsion Library. Currently, air cycle example models are only available for the above transient simulation. Consult with Modelon support if your work requires such pure steady-state simulations, mass estimation, and sizing functionality.

Heat exchanger models are structured by the type of parameterization:

  • effectiveness performance map
  • geometric parameterization

and the fluid combinations:

  • air-to-air
  • air-to-refrigerant

Environmental Control Library contains several air-to-air heat exchanger models.

Vapor Cycle Library contains refrigerant-to-air models.

Heat Exchanger Library contains highly detailed heat exchanger models that are parameterized via geometry parameters. Heat exchanger coupling to air cycle models (i.e., use of heat exchangers from other libraries than Environmental Control Library) may require advanced modeling skills. Consult Library Interconnectability for more information, and contact Modelon Support to inquire more information.

Models of electrical drives, for instance for compressors, can be found in Electrification Library. See the Propulsion and Power application for more details.