Ignition Combustion Explosion Environment and Energetic Materials – ACXEME

This project is mainly an industrial research project and is on the optimization of systems using fuels or explosives.
Firstly, reactants will be composed of solid or condensed phases with specific performances expected (ignition sensitivity, combustion velocity, gas production rate). Secondly, explosions will be studied from the beginning in a reactive medium (gas, solid) to their consequences on environment by describing precisely the combustion front. This optimization will be performed using a multidisciplinary approach (energetics, automatic, image processing).

This industrial chair aims at working on 4 scientific locks:
- Understanding of ignition and combustion mechanisms of solid fuels (including airborne particles and tablets),
- Ignition and combustion stability as functions of pressure and/or mixture quality,
- Search of a new pyrotechnic formulation in agreement with REACH regulations,
- Modelization of transport phenomena in heterogeneous materials using a new approach based on cellular automata.

Concerning technological locks, studies will focus on:
- Study on energetic materials in agreement with REACH regulations,
- Combustion limit extension and research of combustion duration optimum,
- Combustion optimization of airborne particles, mixture quality and influence of turbulence,
- Optimization of combustion products flow with heat transfer in a pyrotechnical device.

WP2: studies focused on the suspension characterization of metal particles in the setups used in these studies (Hartman tube, 20 L sphere). PIV measurements and particle concentration measurements have been performed to follow particle trajectories and speed fields. In addition, geometries of the tube and sphere have been implemented in a CFD solver.

WP3.1: studies started with a feasibility study of combined ignition of low-vulnerability gun propellants. This ignition technique consists of a thermal heating using a laser diode followed by a laser breakdown in the pyrolysis zone. Feasibility has been demonstrated but obtained ignition energies are not significantly reduced compared to classical laser ignition.

WP3.2: The modelization using cellular automata is in progress. A first version of the code is working and is under validation.

WP4: The work is in progress in collaboration with the concerned industrial partner.

WP5: A program for images processing based on deep learning is working but is incomplete due to the lack of images.

With the exception of WP1, all packages have now started with the associated theses which resulted in 3 recruitments and registrations at the Orléans University between April and May 2021.

we are in the process of verifying the porosity measurements evaluated by image analysis using techniques complementary to optical microscopy.
We are also in the process of carrying out thermal diffusivity measurements on the studied powders in order to validate the first simulation results obtained by cellular automata.

S. Delbarre, L. Courty, P. Gillard, Combustion de poudres propulsives : étude de faisabilité de l’allumage des produits de pyrolyse par claquage laser, Congrès National de la Recherche des IUT, Lyon (en distanciel), juin 2021.

Combustion de solides subdivisés : Poussières et matériaux énergétiques : Modélisation évoluant vers une approche utilisant les automates cellulaires, P. Gillard, 17ème école de Combustion, école Thématique CNRS-INSIS, 7-11 Juin 2021

Conférence sur la chaire à l'occasion de la fête de la science (12/13 octobre 2019), à l'IUT de Bourges.

This project proposes a significant contribution for the improvement of explosive and propulsive energy systems. Major advances will be proposed on the two following axes:
- Optimization of materials and designed systems,
- Prediction capacity of composition of energetic materials and system design under current and future environmental constraints.
To do so, the three following items will be combined:
- The scientific expertise of the project academic partners, expertise acquired during several decades in the modelling of reactive media based on solid fuels,
- The design capability of safe propulsive and explosive energy systems with solid-phase or condensed materials, know-how mastered by the project's industrial partners,
- The multidisciplinarity of the leading laboratory, particularly in energy systems, but also in nonlinear and hybrid dynamic systems in the context of spatial (porous materials, heterogeneity) and temporal (event and probabilistic) discontinuities.

Optimization concerns the composition of energetic materials, as well as the induced industrial systems, at the level of ignition or combustion but also at small scale at the level of the organization of the heterogeneities. Indeed, the reactive medium leading to combustion or explosion must be perfectly defined from a physic-chemical point of view. For example, in the case of energetic materials such as pyrotechnic compositions, the grains stacking mode, in addition to the knowledge of their sizes and shapes, plays an important role at local level. In the case of low-vulnerability propellants, the energies and environmental conditions (pressure, nature of the pressurizing gases) must be well defined to obtain a safe and reproducible ignition despite the loss of sensitivity of the propellant.

In addition to optimization, there is also a need to adapt to the new environmental conditions more and more present (e.g. REACH Regulation). This adaptability induces a continuous possibility of anticipation. This implies a better control of sensitivities of energetic materials and their relationships with the induced energy conversion system. To minimize the number of trials and errors, we propose, in this project, a multidisciplinary method to "capture" the relevant parameters, best translators of "local" to "global" and vice versa. It is based on a fine description, at temporal and spatial scales, of physic-chemical properties with the help of cellular automata model, inverse methods for parametric identification and images processing. It will then be possible to follow a flame front instantaneously, but also to define the pyrotechnic composition under anticipated constraints more and more severe.

New materials are currently being developed for the replacement of pyrotechnic compositions in thermal batteries (consequence of the application of REACH Regulation). Combustion process of these substances may be affected, or even totally changed, in case of a partial or complete containment. We will therefore be interested in the evacuation of the propellant combustion products (gun propellant in interior ballistic applications) through a non-adiabatic tortuous channel with the search of a flow optimum in order to preserve the limit pressure necessary to maintain the quasi-stationary combustion. We will also optimize the transition of the combustion in a pyrotechnic environment modelled in 1D: transition from a first medium to a second one, through a discontinuity interface of the substance.