Due to its widespread availability and its environmental and technological benefits, Natural Gas is of great interest to the European Energy policy. Therefore a deep understanding and high-level training in the experimental and numerical tools for investigating natural gas combustion in new burners are of upmost importance for future developments.

Natural Gas will be one of the key parameters in the European energy policy for the next decades. Forecasters predict that natural gas consumption in the EU will double over the next 25 years. European natural gas consumption currently represents approximately 17% of world consumption. European gas imports are expected to reach slightly over 80% of total consumption by 2030. To tackle this challenge, the EU is investing heavily in natural gas equipment, as demonstrated by the construction of the Nabucco pipeline in Turkey.

Due to its availability and environmental and technological benefits, natural gas covers a significant proportion of the European energy landscape. In particular, the use of natural gas makes it possible to divide CO2 emissions nearly by 2 compared to coal. It also enables the use of gas turbines with an efficiency close to 50%. Natural gas is present in all sectors from companies/business to personal/private sector. About 35% of the gas imported or produced in Europe is used in the residential and tertiary sectors for the production of hot water or heat. Another 35% is used in petrochemicals or glass industries. Finally, 30% is used for electricity generation. Moreover, natural gas is starting to be used in the automotive industry, but severe issues related to storage and safety still limit such development.

However, natural gas is a fossil fuel whose energy conversion is mainly achieved by combustion. This combustion process induces two main side effects: the production of greenhouse gases (CO2) and the emission of pollutant species such as nitrogen oxides (NOx) and soot particles. Conventional techniques used to reduce these emissions, already low compared to usual fossil fuels, are often post-combustion treatments and they include CO2 storage, flue gases cleaned up by catalytic and non-catalytic conversions. Another solution is to act directly on the combustion process in order to limit pollutant emissions at the source while maximizing combustion efficiency. New processes are currently using this strategy, for example regenerative burners, flameless combustion, combustion of highly diluted mixtures or oxy-combustion.

These processes, which are already being used in some industrial units, are still poorly understood and are very difficult to transpose from one industry to another. It is therefore extremely important to develop academic and research studies on these new combustion processes to make best use of existing resources while limiting their environmental impact. These new combustion processes are very different from existing technologies and constitute real technological breakthroughs:

• flows of different compositions using multiple entries;
• complex geometry of injectors, which results in highly complex unsteady flows;
• wide range of spatial scales from millimetres up to tens of meters;
• high pressure and high temperature (gas turbine, steam reforming for synthetic gas production);
• massive flue gas recirculation, to ensure flame stabilization for low-calorific fuels and reduction of pollutant emissions.

These points show that deep understanding and detailed experiments and modelling of the combustion processes are of paramount importance. In particular, the appropriate description of the interactions between the combustion process (high speed and high temperature process) and the system aerodynamics is crucial in order to develop innovative combustion systems. Considering the complex nature of these phenomena, the use of both experimental investigations and Computational Fluid Dynamics (CFD) is acknowledged to be essential for the development and implementation of such novel combustion technologies. In particular, CFD calculations can be applied directly at the industrial scale of interest, thus avoiding scaling-up the results from lab-scale experiments, while experimental investigations are necessary to understanding fine phenomena and validating physical models used in CFD.

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