Research project

Combustion strategies for next generation fuel-flexible burners


A wide use of hydrogen injection into the natural gas network is expected in Europe in the near future. The addition of hydrogen, produced using renewable or alternative energy sources, to natural gas, will contribute to reduce the emissions of greenhouse gases. At the same time it will absorb off-peak power of wind or solar power stations, making them more efficient. First commercial projects, in which addition of up to 15-20% of hydrogen to natural gas pipelines is planned, have already started in Europe. Novel “green” fuels are expected to become important in our energy production in the near future. This is especially the case in the Netherlands, where the government has the ambition to organize the ‘Gasrotonde’, an infrastructure containing a much broader range of gases.While the existing networks for gas storage and delivery can accommodate such amounts of added hydrogen, conventional domestic appliances, such as heating boilers, kitchen stoves, and combined heat and power (CHP) systems cannot automatically do so. Blending of varied amounts of hydrogen to natural gas, or variation of the natural gas composition itself may lead to flashbacks, overheating and damage of gas appliance burners. Also unstable combustion and increase of pollutant emissions may occur. Recent studies by the applicants have demonstrated that the addition of hydrogen to methane can drastically impact the flame stabilization behavior due to specific effects related to the high mass diffusivity of hydrogen: so-called preferential diffusion effects [1]. Preferential diffusion is a somewhat elusive concept, and still poorly understood. Prevailing criteria for fuel interchangeability, traditionally used by burner/gas appliance designers, ignore these effects and are likely to fail when applied to hydrogen containing blends. New approaches, therefore, have to be developed, based on a fundamental understanding of the effects related to preferential diffusion. The main goal of the proposed project is to generate fundamental knowledge and understanding of preferential diffusion effects on the flame stabilization/combustion behavior of hydrogen-enriched natural gas, and to translate this knowledge into new design rules for fuel-flexible burners that can handle natural gas with a broad range of compositions. To meet the project goal, extensive experimental and numerical investigations will be performed, aimed at fundamental understanding of preferential diffusion effects. These effects determine the specific combustion performance of novel fuel blends at conditions typical for low-NOx surface burners used in gas appliances.
People involved in this project: Philip de Goey, Hans van Griensven, Rob Bastiaans, Theo de Groot, Yuri Shoshyn, Faizan Vance & Lyon Hegh.
About the picture:the pictures show top:CH* chemiluminescence vs bottom: heat release rate (scaled with maximum of corresponding 1D flat flame) from numerical simulations for three different mixtures. Alpha=0 is methane, alpha=0.2 is 20%H2+80%CH4 and alpha=0.4 is 40%H2+60%CH4. All three flames have same mixture velocity, and same SL (by tuning phi). As such one could expect that flames should have same angles and burning profiles. But mixture with more H2 burn stronger near flame base, move closer to the burner and lose more heat to burner top surface consequently. This can represent the different changes in stabilization mechanism when mixture Lewis number is changed.