Overview
The GENIAL project aimed at developing a numerical methodology and a SW tool to model the current return networks (called ALEEN, ALmost Equipotential Electrical Network) installed aboard composite aircrafts. It was able to:
- input geometry and material properties of ALEEN (including also metallic structural parts of the aircraft if any) from CAD;
- accept measured data as partial characterization of ALEEN sub-parts;
- evaluate the impedance matrix of ALEEN in the frequency range DC-100 kHz, also considering the EWIS (Electrical Wiring Interconnection System) and the electromagnetic interaction with aircraft body;
- interface the above-mentioned impedance matrix with an electrical database of EWIS, in order to evaluate the impedance between any two interconnection points of EWIS.
A 3D full-wave procedure was implemented based on PEEC (Partial Element Equivalent Circuit) method. A number of improvements with respect to “standard” PEEC algorithm was implemented (e.g. non-orthogonal PEEC to avoid staircase problem; modelling of anisotropic composites; modelling of non-radiating networks; effective skin-effect modelling; Model Order Reduction, MOR). Acceleration methods like MLFMA (Multi-Level Fast Multipole Algorithm) and parallel coding were applied in order to allow effective analysis of large structures in a limited amount of time, with currently available HW resources (i.e. no expensive HPC resources required). The computational module was integrated, together with pre-processing and post-processing modules, into a SW CAE tool (“ALEEN Modelling Tool”) also providing user-friendly working procedures, projects management, data storing and data navigation. A general “client-server” HW configuration was allowed (without any limitations about the number of clients and servers) with automatic dispatching procedures for optimal exploitation of the HW resources. The procedure was validated against experimental data measured on a mock-up.
Funding
Results
Executive Summary:
The metallic bodies of “standard” aircrafts are commonly used as conductive electrical pathways for the return of direct and alternating currents, faults currents, lightning currents and also other functions related to voltage differentials, electrostatic charge draining, electromagnetic shielding etc.
Such a procedure is not applicable on aircrafts made of composite materials because of their low conductivity. A dedicated conductive electrical pathway, named “Almost Equipotential Network (ALEEN)” or “Current Return Network (CRN)” has therefore to be integrated into the aircraft body. Such networks can be practically realised in several different ways, mainly exploiting both structural metallic parts of the aircraft (beams, seats rails, etc.) and also dedicated paths, but anyway they can never be an ideal ground and worse performance than those currently obtained on metal aircraft may be expected.
Accurate electrical/electromagnetic characterization of ALEEN structure is therefore important:
- To be able to correctly design electrical systems such as EWIS, reducing risks and saving mass
- To estimate how the ALEEN configuration works with respect to other required functions (e.g. faults currents, lightning currents, electromagnetic shielding, etc.)
- To optimize the ALEEN configuration itself without needing expensive (and sometime practically unfeasible) repeated bread boarding.
In the framework of GENIAL project, a tool dedicated to ALEEN networks modelling has been developed. The Tool is able:
- To input aircraft and ALEEN geometries and material properties from CAD (e.g. CATIA)
- To evaluate the equivalent impedance matrix at ALEEN terminals in the frequency range DC-hundreds of kHz’s, also considering the EWIS and the electromagnetic interaction with aircraft body
- To visualize induced current and potential distribution on the aircraft/ALEEN.
Simulation methods having special “low-frequency stability” and “high-fidelity modelling” features (mainly based on S-PEEC: Surface-Partial Element Equivalent Circuit formulation) have been customized and validated for this kind of applications.
The implementing team of Genial was made of Ingegneria Dei Sistemi S.p.A. and the University of L’Aquila. They interfaced with Safran Engineering Services.