MIXVAL - Mixer Simulation and Validation

In passenger aircraft, the mixing and distribution of humid airflow from the cabin and engines into the cockpit and passenger cabin, as well as electronic components, takes place at a central location of the air conditioning system, the mixer. So far, the flow and heat transfer processes and the ice formation and accretion cannot be calculated with sufficient accuracy. Therefore, the aim of this project is to develop a method for simulating the physical processes in the mixer.

Short Description

Motivation

In addition to experimental methods, simulation is often used for various problem statements in the development of passenger aircraft, such as structural calculations using FEM and flow analyses using CFD. The advantages of simulation are undisputed, and consist mainly of the fact that it can be used in the product development process at a very early stage, even before components are available as hardware. Furthermore, experiments are usually much more detailed, allowing a closed interpretation of the physical processes that take place. On this account, a cost-effective technical and ecological optimum can be attained. Certain processes that occur in aircraft operation are complex to such a degree that they cannot yet be reliably predicted. These include the flow and heat transfer in air conditioning systems. It goes without saying that the better the design and the detailed-engineering, the more efficiently the air-conditioning system can function.

Objectives

To increase air conditioning efficiency in large capacity passenger aircraft.
To investigate the internal aerodynamics ice accretion of air conditioning components.
To execute CFD simulations.
To conduct experimental analyses.

Content

The project focuses on the development of a method for simulating the physical processes in the mixer. Detailed measurements are being carried out on a generic mixer built specifically for the project and using the most sophisticated optical methods. The experimental data is provided in a database for the validation of the simulation.

The database is supplemented by measurement results from an actual mixer. The data will be imported into the project by Airbus. Successful completion of the project will provide a validated calculation method for simulating the processes in the mixer. Mixers could, therefore, be optimised for a predetermined performance, consequently reducing weight and energy consumption.

Methodology

The aim of the presently proposed project is to develop a CFD simulation method suitable for use in the product development process for mixers. For this purpose, the structure and density distribution of computation meshes, the boundary layer treatment (wall functions), the buoyancy terms in the momentum equation, the forms of the energy equation, numerical parameters, and in particular the turbulence models, have to be investigated and determined.

Furthermore, the models for ice formation and accretion, which are generated and used in the Mo.v.E project, are to be further developed. There are currently three alternatives in turbulence modeling to choose from: RANS (Reynolds Averaged Navier-Stokes), LES (Large Eddy Simulation), and DES (Detached Eddy Simulation).

In the Mo.v.E. (Modeling Ice Accretion in Aircraft Internal Aerodynamics) project, four models were selected from the literature after one year as having the most potential for further development in the second (final) year of the project in terms of ice formation and accretion. The model for ice accretion developed in Mo.v.E will also be applicable to the mixer.

Outcome

Among the most important innovations of this project is the transfer of academic methods into industrial practice, and the completion of the simulation chain through the further development of ice formation and accretion models.

Project Partners

FH JOANNEUM GmbH - Coordinator
PRISMA Engineering GmbH
Technische Universität Graz

Funding program: TAKE OFF