John and Marcia Price College of Engineering
10 The Influence of Flame-Front Instabilities on Deflagration to Detonation Transition for Premixed Hydrogen Flames
Kayden Jenkins and Alex Novoselov
Faculty Mentor: Dr. Alex G. Novoselov (Department of Mechanical Engineering, University of Utah)
Alternative fuels have become an important research topic as the need to reduce carbon emissions continues to grow. One of the most promising alternatives being researched is hydrogen due to its high energy density per mass compared to fuels like gasoline. Hydrogen possesses some unique attributes, such as flame-front instabilities, which arise due to it having a high reactivity coupled with a low molecular mass. These instabilities have a strong influence on the flame characteristics as they can enable rapid acceleration. This can lead to the flame-front undergoing Deflagration to Detonation Transition (DDT), or moving from a subsonic deflagration wave to a supersonic detonation wave [1]. As research into alternative fuels continues to grow, a focus on new technologies like rotating detonation engines grows with it. Thorough research into the dynamics of hydrogen flames, DDT for example, is necessary before new technologies can be considered as feasible. Ample research has been conducted utilizing physical obstructions in the combustion chamber to trigger DDT, but little has focused on how flame-front instabilities can affect DDT. As such, we conducted 3D simulations for both non-unity and unity Lewis number cases to test the effects of thermo-diffusive flame-front instabilities on DDT. This was done using PeleC, a compressible solver from the Pele Suite of Computation Fluid Dynamics (CFD) software for chemically reacting flows. From these simulations, we found that the unity-Lewis number case experienced DDT more quickly than the non-unity case, given our chosen boundary conditions. This implies that hydrodynamic instabilities have a significant effect on the flame-front as well as thermo-diffusive instabilities. This is evidence since thermo-diffusive instabilities are absent in the unity-Lewis number case, while hydrodynamic instabilities are present in both cases. Understanding how these two sources of instability play a role in inducing DDT is an area that requires further inquiry, which we plan to pursue.
Footnote
[1] J. H. S. Lee, (2008). The detonation phenomenon. New York, Ny: Cambridge University Press.