Periodic Reporting for period 2 - FireExtinction (MULTI-PHYSICS METHODOLOGY FOR PHASE CHANGE DUE TO RAPIDLY DEPRESSURISED TWO-PHASE FLOWS)
Período documentado: 2019-03-01 hasta 2020-02-29
What is the problem being addressed? Why is it important for society?
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 being evaluated, 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 redesign the complete fire suppression system and in particular, to develop new simulation and modelling tools to be able to predict, in advance, the behaviour and performance of the new fire extinction agents.
What are the overall objectives of FireExtinction?
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.
7. Develop a useful simulation and predictive tool for multiphase discharges, to be exploited by the aeronautical industry in the definition and design of the new fire extinction systems.
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 being evaluated, 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 redesign the complete fire suppression system and in particular, to develop new simulation and modelling tools to be able to predict, in advance, the behaviour and performance of the new fire extinction agents.
What are the overall objectives of FireExtinction?
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.
7. Develop a useful simulation and predictive tool for multiphase discharges, to be exploited by the aeronautical industry in the definition and design of the new fire extinction systems.
FireExtinction project has developed 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 new methods & tools are able to evaluate the atomization, dispersion and evaporation of new fire extinction agents in real configurations. The methodology combines existing models with newly developed ideas which consider the coupling between large and small scales in two different schemes: Eulerian and Lagragian, which is able to describe the penetration of a two-phase flow, including phase transition, into the confounding space. The method is implemented as a user defined function in a tool chain and coupled with the nearfield CFD calculation. Both, a Lagragian and a Eulerian formulation are followed using existing commercial tools and “in-house” multiphase solvers. Finally, several experiments are used to validate the numerical results. The project has been 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 “in-house” codes suitable for industrial applications.
The activities have been completed with success and a new tool and methodology have been delivered and evaluated. The tool has already demonstrated that the nozzle used with previous agent halon is not able to atomize with other fire extinction agents, such as Novec or water. This is an important outcome of the project since obliges to a complete redefinition of the system.
The tool will be exploited by the aeronautical industry, in particular Airbus, in predicting the behaviour of new fire extinction agents and provide useful information for design.
The works performed has been disseminated in several international conferences and main data bases, numerical and experimental, are freely distribution (with permission) to the scientific community in Zenodo open data repository.
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 “in-house” codes suitable for industrial applications.
The activities have been completed with success and a new tool and methodology have been delivered and evaluated. The tool has already demonstrated that the nozzle used with previous agent halon is not able to atomize with other fire extinction agents, such as Novec or water. This is an important outcome of the project since obliges to a complete redefinition of the system.
The tool will be exploited by the aeronautical industry, in particular Airbus, in predicting the behaviour of new fire extinction agents and provide useful information for design.
The works performed has been disseminated in several international conferences and main data bases, numerical and experimental, are freely distribution (with permission) to the scientific community in Zenodo open data repository.
FireExtinction presents several progresses beyond the state of the art:
o High-fidelity simulations using LES for the modelling and simulation of two-phase flows with phase transitions of rapidly depressurised mists of fire suppression systems. These models will be integrated in commercial solvers so they can be used as a multiple-droplet model, permitting much coarser meshes and U-RANS turbulence models to analyse the complete geometry or implemented as a sub-grid model in a multi-physics Eulerian-Eulerian approach.
o Experimental measurements of suppression agent atomization and vaporization in controlled conditions for model development and validation.
o Development of a Eulerian-Lagragian approach in the context of U-RANS that can be used to reduce the computational cost and increase the accuracy of the multiphase predictions.
Potential impact
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.
o High-fidelity simulations using LES for the modelling and simulation of two-phase flows with phase transitions of rapidly depressurised mists of fire suppression systems. These models will be integrated in commercial solvers so they can be used as a multiple-droplet model, permitting much coarser meshes and U-RANS turbulence models to analyse the complete geometry or implemented as a sub-grid model in a multi-physics Eulerian-Eulerian approach.
o Experimental measurements of suppression agent atomization and vaporization in controlled conditions for model development and validation.
o Development of a Eulerian-Lagragian approach in the context of U-RANS that can be used to reduce the computational cost and increase the accuracy of the multiphase predictions.
Potential impact
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.