Simulations and Modeling of Turbulent Combustion Using Fuel Mixtures with High Hydrogen Content

• Applicant: Professor Dr.-Ing. Heinz Pitsch
• Subject Area: Fluid Mechanics
• Term: from 2016 to 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 277815585

Stationary gas turbines play a significant role in the present energy supply, and their importance will continue to grow in the energy landscape of the future, partly because of their good load flexibility and quick start capability. As a consequence of the present efforts for renewable energy and cleaner use of fossil fuels, fuel-flexible operation of gas turbines, and particularly fuel enrichment by hydrogen, is becoming an inceasingly important topic in fundamental research and technology. Examples include the use of hydrogen as energy storage and the combustion of syngas in the integrated gasification combined cycle (IGCC) process. However, the enrichment of fuels with high fractions of hydrogen results for lean stationary gas turbine combustion in a significant change in combustion characteristics. This can result in increased combustion noise, flashback, unwanted combustion instabilities, and eventually in complete machine failure. Here, especially thermo-diffusive instabilities, induced by differential diffusion of hydrogen, play an important role and can lead to strongly altered and cellular flame structures exhibiting locally extinguished regions. The topic of the present project proposal is therefore the combustion of fuel mixtures with high hydrogen content (HHC). The goal is to enable computer-based simulations of turbulent combustion processes in combustion chambers considering the effects found in fuel flexible operation. Such simulations nowadays are an important part of the development and optimization of gas turbines. One of the main scientific challenges for modeling is here that the complex interaction of flame structure, differential diffusion, thermo-diffusive instability, and turbulence is not yet sufficiently understood. Within this project, these phenomena shall be investigated by means of direct numerical simulations (DNS). For this, DNS will be performed for premixed turbulent combustion of methane/hydrogen mixtures with different hydrogen content. Using systematic analysis tools, the resulting data will be analyzed a priori and a posteriori to address some important questions, for example with respect to flame structure, burning rate, and the influence of thermo-diffusive instabilities on the turbulence. The working hypothesis is that the combustion of HHC fuels can be described by suitable multi-scalar models. An appropriate formulation and modeling of the resulting unclosed terms will be developed based on the systematic analysis of the DNS data.

• DFG Programme: Research Grants