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Report

Teaser, summary, work performed and final results

Periodic Reporting for period 1 - FireExtinction (MULTI-PHYSICS METHODOLOGY FOR PHASE CHANGE DUE TO RAPIDLY DEPRESSURISED TWO-PHASE FLOWS)

Teaser

Summary

Aeronautical on-board fire suppression systems, e.g. the one found in the cargo compartment, are based on the interruption of the propagation of chain reactions typically found in aeronautical fuels. These fire suppression systems historically used hydrofluorocarbons (HFCs) as a fire protection fluid. Even small concentrations of these fluids in the air are sufficient to stop the reaction. The most common fire extinction agent has been Halon (R13B1, CFBr3), however due to their high global working potentials (GWPs), industry has been pushed towards more environmentally friendly alternatives. Several alternatives are on the table, in particular Novec-1230 Fire Protection Fluid. Novec-1230 is a sustainable HFCs alternative that works quickly, cleanly and efficiently. The main difference between Halon and Novec-1230 is, in addition to the lower global warming potential of the latest, its higher molecular weight. As a result, the boiling point at ambient pressure of the latter is much higher which results in a more difficult vaporization and dispersion. It is therefore necessary to update the existing simulation and modelling tools to be able to predict, in advance, the behaviour and performance of the new fire extinction agents.
To do that, the following technical objectives are defined:
1. Perform a critical assessment of existing models for phase change and their applicability to current fire suppression agents and feasibility of coupling with multiphase solvers.
2. Implement a selection of the state of the art models of phase change, specifically adjusted for rapidly depressurised multicomponent mixtures, as a user function of a two-phase/multi-phase simulation solver using a Eulerian-Lagrangian approach.
3. Carry out an experimental campaign with at least two different extinction agents and relevant conditions.
4. Perform a high-fidelity direct numerical simulation in a reduced domain where most of the physical scales are obtained. Validate some of the results using the experimental data available from the experiments of point 3.
5. Use the results of point 4: First, develop and calibrate an improved multi-drop model used in an Eulerian-Lagrangian approach and, second, develop a sub-grid two-phase model for a two phase Eulerian-Eulerian computational fluid dynamics (CFD) multiphase solver.
6. Conduct a parametrical study of realistic conditions (flight phases and operational conditions defined by the Topic Leader) of the fire suppresser using both, the Eulerian-Eulerian and Eulerian-Lagrangian CFD U-RANS models developed in point 5. Compare both approaches in terms of accuracy and efficiency.

Work performed

FireExtinction project is developing a multi-physics methodology to couple existing CFD solvers and solutions with models for phase change of rapidly depressurised mist of a fire suppression system. The methodology combines existing models with newly developed ideas which consider the coupling between large and small scales. The new models aim to describe the penetration of a two-phase flow and phase transitions into the confounding space and will be implemented as a user defined function in a tool chain and coupled with the nearfield CFD calculation. Both, a Lagragian and a Eulerian formulation will be followed using existing commercial tools and â€œin-houseâ€ multiphase solvers. Finally, one experiment is proposed to validate the numerical results in one relevant case. The project is organized in 3 main technical work-packages:
WP2, Implementation of models and validation tests, is devoted to set-up and adjustment of a specific test facility to characterize spray, atomization, mixing, phase-change of fire suppression agents in controlled conditions.
WP3 (Models Coupling into HiFi Sim LES CFD codes. Development and implementation of a sub-grid model) aims to integrate 2-phase and phase-change models into a HPC High Fidelity CFD code, which allows solving complex multiphysics / multiphase flows on large-scale applications (highly resolved LES modelling). The implemented models within the CFD will be used to perform a parametric study using the HPC High Fidelity CFD code to get a complete database on the main parameters affecting sub-grid model.
Finally, WP4 (Parametric studies on dedicated suppression agents) is devoted to the integration of the 2-phase, phase-change and sub-grid scale models in the commercial CFD and â€œin-houseâ€ codes suitable for industrial applications.

After the first year, activities in WP2 are almost finished and WP3 and WP4 are under development.

Final results

The project will have a strong impact on research, development and demonstration of an On-board inert Gas Generation System able to develop an environmentally friendly cargo fire suppression system, and in particular to eliminate the use of Halon as fire extinction agent, currently used in aeronautics.
Additionally, by improving innovation capacity and the integration of new knowledge into current designs, the successful implementation and development of this project will have positive impacts on the development of new models for multiphase flow with phase change and detailed numerical simulation of complex multiphase sprays.