Introduction

Purpose

The Environmental Control Library, or ECL, targets design and verification of aircraft environmental control systems, including prediction of energy consumption, thermal conditions and human comfort. The library contains models of heat exchangers, compressors, turbines, ejectors or jet pumps, water separator, valves, the cabin and pipes.

Key features involve:

• Flexible composition of user-defined system architectures for efficient model management,
• Real-time capable high performance models enabling Hardware-In-the-Loop (HIL) applications,
• Full support for bidirectional flow for analysis of all modes of operation on ground and in flight,
• Efficient property models of moist air enabling robust and fast simulation of large-scale systems,
• Online visualization of simulation results for intuitive understanding of the system behavior, and
• Configurable model fidelity for faster simulation and right complexity level.

Modeling and simulation

Many simulation tools are essentially user-interfaces for setting the parameters of fixed simulation models. This means that the actual equations that describe the model are impossible, or difficult, to modify by users. This Modelon Modelica library offers a different approach and provides much more flexibility. In combination with a simulation tool, this Modelon library is a complete modeling and simulation tool. This is important to understand, since it implies that the working procedure is slightly different and enables some additional modeling steps:

• Build models that describe the phenomena of interest,
• Tune the model parameters,
• Use the models to set up an experiment that exposes the phenomena of interest,
• Simulate the experiment, and
• Analyze the results.

This Modelon library contains a large set of pre-defined models and templates that makes most modeling tasks straightforward. For many standard tasks it is possible to use the library in the same way as a pure simulation tool, i.e., it is sufficient to choose the right model, define all parameters and start the simulation.

Flexibility with prudence

It is possible for users to modify and extend most of the models in the library, and also to complement the library with custom models. It is also possible to mix with model components from other libraries. This is one of the major benefits of describing models using a high-level modeling language like Modelica. Customization of models and components can be done either from the graphical user interface and diagram view, or, for advanced users, by typing Modelica source code. There is also great flexibility in setting up experiments and analyzing results. The flexibility implies great freedom for users to define models and experiments, but may also require more attention to details and understanding, in case the advanced editing features are used.

Modelon libraries

All Modelon libraries are compatible and can be combined to solve specific engineering design tasks. A Modelon library of particular interest for the Environmental Control library are the Heat Exchanger Library, the Fuel System Library, and Jet Propulsion Library. The former provides more detailed heat exchanger models based on geometric parameterization and highly accurate Nusselt-type heat transfer correlations. The Fuel System Library in turn is used to design and verify fuel systems on civil and military aircraft. Jet Propulsion Library can be used to model the jet engine of an aircraft and may thus provide a key complement when modeling the bleed air system. Please note that these libraries can also be used as a stand-alone solution.