The John and Marcia Price College of Engineering
16 Modeling and Simulation of Turbulent Premixed Hydrogen Flames
Alex Gilsoul
Faculty Mentor: Alex Novoselov (Mechanical Engineering, University of Utah)
With global warming becoming an ever-present danger, it is important that we work to lower our carbon emissions. As such, hydrogen has been proposed as a green alternative to natural gas for energy conversion in gas turbines, as it is carbon neutral.
Because of its low molecular weight and high reactivity, hydrogen gas expresses some unique properties during combustion, such as unstable flame fronts [1]. These instabilities strongly modify global properties of the flame, such as flame speed, that are relevant to modeling systems like gas turbines.
Good models to predict the effects of these instabilities do not exist. Simulations of hydrogen flames at small scales are possible with Direct Numerical Simulations (DNS) which solve the Navier-Stokes Equations, however for full combustor scales this type of modeling is computationally intractable.
We simulated 3D laminar and turbulent hydrogen flames on a small-scale. The thermochemical quantities of these flames were analyzed and compared to 1D flame solutions modeled with Cantera using the Pele Suite of flow simulation codes and C++ and Python codes we wrote. Our codes use GPU parallelization to generate a large number of flame paths simultaneously by following progress variable gradients through the flame front [2]. Then, we used trilinear interpolation to determine the properties of points along these paths such as temperature, mixture fraction, and curvature. Plotting this data, we found that our 1D Cantera flames will not give us enough information. However, we did discover that curvature seems to have a large impact on whether a given flame path will reach adiabatic flame temperature (AFT), stay below AFT, or go higher than AFT. These results imply that curvature will be an important piece of an effective model, and so we will pursue it further.
References
[1] Berger, L., Attili, A., Pitsch, H. (2022). Intrinsic instabilities in premixed hydrogen flames: Parametric variation of pressure, equivalence ratio, and temperature. Part 1 – Dispersion relations in the linear regime. DOI: https://doi.org/10.1016/j.combustflame.2021.111935
[2] Chan, W. L., Kolla, H., Chen, J.H., Ihme, M. (2014, April 13). Assessment of model assumptions and budget terms of the unsteady flamelet equations for a turbulent reacting jet-in-cross-flow. DOI: http://dx.doi.org/10.1016/j.combustflame.2014.04.007