On 2022-05-17
by Hydrogen+

Airbus Protect: modelling accidental phenomena for better risk management

Modelling accidental phenomena

Interview with Alban MAHON – Accidental Phenomena Modelling Specialist at Airbus Protect

Can you tell us about your work in relation to safety and industrial risks linked to hydrogen?

For the last eight years I have been working in quantification of consequences related to accidental phenomena. This includes, for example, fires, explosions and the release of toxic products into the atmosphere. The aim of these calculations, and therefore these studies, is to determine the safety distances to be established in official documents according to predefined thresholds to dimension the appropriate prevention and protection measures. This may concern, for example, heat fluxes in the event of flammable product releases or a fire. Any constraints related to the environment of the industrial site are also taken into account in these studies.

Since 2021, I am involved in the Airbus zero emission aircraft project. I am contributing with my knowledge and expertise to the phenomenology of using hydrogen as a fuel. This of course involves the question of establishing safety distances between on-board equipment for example, but also all the impacts linked to the modification of the fuel. In other words, are the requirements currently followed for the use of Kerosene still applicable or do they need to be evolved for the use of hydrogen. We are therefore assessing all the impacts of this change as well as the safety consequences in the context of hydrogen storage and distribution.

Methods and tools

From the point of view of the methods and tools currently used in the industry, the assessment of risks and safety distances is based on several different model ranges, from the simplest to the most complex. The latter require a 3D model of the geometry with a fine resolution of the physics thanks to the use of computers or even supercomputers. These more complex models allow us, for example, to take into account all the physical phenomena without having to resort to strong assumptions.

The methods used depend in particular on the objectives and challenges of the studies. In the context of industrial or airport infrastructures involving hydrogen, methodologies based on experimental correlations are often used. This takes into account potential strong  assumptions consideration which could depend on the maturity of the project as well as the engineer’s feedback. It is also important to mention that the majority of the models used were mainly developed, more than 20 years ago, in relation to the use of hydrocarbons.

Therefore, the development of the hydrogen sector must be accompanied by the update of these calculation methods in order to take into account hydrogen specificities (extremely flammable product, specific physico-chemical properties) or the conditions of the new use cases (cryogenic hydrogen storage, high distribution pressure, etc.).

For example, the storage of hydrogen in a liquid form, with a temperature close to absolute zero, leads to the specific consideration of cryogenic impact.

Currently the update of models takes considerations of many actors, new models, best practices as well as regularly published actualisations related to hydrogen into account. Part of our work is therefore to capitalise on these new possibilities and establish new calculation practices.

However, certain problems linked to hydrogen are still poorly understood. This is the case, for example, with detonation phenomena, which are accompanied by shock waves and high combustion speeds.

These purely physical considerations are the core preoccupation of specialised laboratories and their research will undoubtedly contribute to future versions of the models or the development of new calculation approaches.

Finally, it is important to remember that the critical eye of the engineer in charge of these estimates is essential in order to evaluate the safety distances between the infrastructure and the surrounding population in a prudent manner. However, the constraints mentioned above may be significantly different in the case of a product where safety is at the heart of the development. This is the case, for example, of the hydrogen aircraft.

Can you tell us about your work on the hydrogen aircraft project?

Generally speaking, a distinction should be made between future airport infrastructures and the aircraft itself. For the former, approaches from industry are used to define safety distances for both passengers and airport staff. For the aircraft, the constraints to maintain the current level of safety are very important. It is therefore necessary to understand the maximum of the physical phenomena in order to be able to propose a design that meets all the constraints, including those of safety.

Unlike the development of the latest aircraft (A350, A320neo), for the hydrogen aircraft, we are starting almost from scratch. The approach we have taken is to look at the current state of the requirements defined for kerosene fuel and to ask ourselves whether what has been defined is valid for hydrogen. This approach makes it possible to identify the points on which a significant evolution is necessary and reveals the need for any kind of knowledge consolidation. For example, is the thermal attack of a kerosene flame similar or different to a hydrogen flame? Will the requirements for structures capable of containing a kerosene fire be different for hydrogen? This work is ongoing and I am actively involved in it.

This work is also accompanied by updates and developments of new tools, the validation needs of which are carried out in parallel by setting up experimental tests and studying scientific publications. The research focuses in particular on several areas such as hydrogen combustion, structural strength, cryogenic aspects, etc. The use of hydrogen can be seen as a challenge because of its use in extreme conditions, from cryogenic storage temperatures to more violent combustion/explosion. This is a real exploration in the field of physics.

The objective is to push research further and further in order to understand all the accidental phenomena that can occur on a hydrogen-powered aircraft. This will increase our knowledge of the factors that can lead to risks. Ultimately, this exploration work allows us to anticipate possible risks, to avoid them and to propose solutions, designs or infrastructures with a high level of safety.

Airbus Protect

Airbus Protect is specialised in the field of performance and risk management and offers a comprehensive range of services, particularly for the hydrogen sector.

The services provided are aimed at optimising the performance and continuity of service of their clients’ systems and installations with a view to the sustainability of their activities:

  • Sustainability: Environment and industrial risks, regulatory files (ICPE, ATEX, hazards and environmental impacts, etc.), energy management, fire safety engineering, risk management & supply chain
  • Safety: Reliability and operational safety, operational availability and total cost of ownership, maintenance optimisation, human factors
  • Security: Governance, audits and services in industrial cyber security, security operation centre
  • The services of consulting, studies, training coupled with digital modelling tools enable us to support all the players in the value chain, and in particular:
  • Mobility players (aeroplanes, helicopters, trains, automobiles, ships, buses, cars, autonomous systems, etc.)
  • All associated infrastructures (assembly and manufacturing sites, multimodal infrastructures (airports, stations, ports, etc.), infrastructures and industrial production systems (including electrolysers), transport, hydrogen liquefaction.

Airbus Protect teams are involved in all phases of the life cycle of a system or installation, particularly for the validation of concepts and scenarios in the project phase but also for the improvement and optimisation of performance in the operations phase.

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