Green-Combustion · Addressing challenging issues for turbulent premixed hydrogen combustion modeling using novel technologies
Horizon 2020 — Marie Skłodowska-Curie Actions
- Duration
- 2021-09-01 → 2023-08-31
- EU contribution
- €178,320
- Participants
- 2
- Scheme
- MSCA-IF
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Results in brief
Addressing challenging issues for turbulent premixed hydrogen combustion modeling using novel technologies
For hydrogen combustion, the most challenging issues are the augmented effects of differential diffusion leading to thermodiffusive instabilities, which can substantially change flame dynamics and heat release rates. Although hydrogen is commonly regarded as a green fuel since it does not emit greenhouse gases, nitrogen oxides (NOx) can be formed during its combustion in the air. It was found that the formation of NOx via the thermal pathway is the primary reaction pathway at close to stoichiometric conditions due to the high temperatures. In fuel-lean premixed hydrogen flames, NOx emissions can be reduced due to the overall lower flame temperatures. However, intrinsic instabilities in premixed hydrogen flames lead to cellular structures, which directly influence local heat release and the local fuel-air ratio and lead to local super-adiabatic temperatures, which control the local reaction pathways of NOx formation. In this project, the characteristic patterns and NOx formation mechanism in the thermodiffusively unstable premixed hydrogen flame are investigated by performing large-scale direct numerical simulations (DNS). In Green Combustion, the following research questions are addressed: (1) The characteristic patterns of thermodiffusively unstable premixed hydrogen flame in a sufficiently large computational domain are quantified; (2) The NOx formation mechanism in the thermodiffusively unstable premixed hydrogen flame is investigated through a reaction pathway analysis; (3) The effects of computational setup (2D vs. 3D) on the characteristic patterns and the NOx reaction pathways are quantified; (4) A new flamelet tabulation method is proposed to predict NOx formation in thermodiffusively unstable premixed hydrogen flames, in which the effects of curvature are considered. The overall objectives of this project are to understand the characteristic patterns and the NOx formation mechanism in thermodiffusively unstable premixed hydrogen flames and to accurately predict the thermodiffusively unstable premixed hydrogen flame using a high-fidelity combustion model.
Data: CORDIS, © European Union
Project objective
Hydrogen is enjoying a renewed and rapidly growing attention in Europe and around the world. The most important advantage of hydrogen usage is that it does emit greenhouse gases. The EU's priority is to develop renewable hydrogen where the H2 is produced from the electrolysis of water, with the electricity stemming from renewable energy. This meets the goal of net-zero greenhouse gas emissions by 2050. There are two options for hydrogen usage. One is the drop-in approach, where only a limited amount of H2 can be added to the fossil fuel to reuse the existing chambers, due to the very different properties of H2. However, this option still emits a large amount of greenhouse gases. The other one is to redesign the existing chambers to burn substantial H2. The most challenging issues for burning substantial H2 are the strong differential diffusion and its induced instabilities. The state-of-the-art combustion model cannot capture these phenomena with accuracy, particularly when they further interact with turbulence. The aim of this proposal is to develop and validate such a model to close this gap. The model will be based on a flamelet approach, and a novel machine learning technology will be introduced to consider the differential diffusion (objective 1). To model the positive and negative curvatures in the unstable premixed H2 flame, a novel flamelet model will be developed based on the detailed a priori and a posteriori analyses of the state-of-the-art DNS datasets (objective 2). Finally, the developed flamelet model will be extended to LES with the differential diffusion and curvature related sub-grid scale (SGS) effects being considered with the artificially thickened flame (ATF) model. Particularly, the SGS effects will be considered by modifying the efficiency function. LES will be conducted for the DNS configuration and a turbulent methane flame with substantial H2 addition using the developed flamelet model coupled with the modified ATF approach (objective 3).
Original text from CORDIS.
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Data: CORDIS, © European Union