Direct numerical simulations of the Taylor-Green Vortex interacting with a hydrogen diffusion flame: Reynolds number and non-unity Lewis number effects

TL;DR

This study uses direct numerical simulations to explore how hydrogen diffusion flames interact with turbulent vortices in the Taylor-Green Vortex, revealing effects of Reynolds number and Lewis number on flame-turbulence dynamics.

Contribution

It provides new insights into hydrogen flame-turbulence interactions at various Reynolds numbers and non-unity Lewis numbers using DNS, highlighting turbulence suppression and flame strengthening effects.

Findings

Vortices dissipate quickly at low Reynolds numbers.

High Reynolds numbers show vortex stretching and turbulence transition.

Heat release suppresses turbulence intensity and development.

Abstract

Understanding the interactions between hydrogen flame and turbulent vortices is important for developing the next-generation carbon neutral combustion systems. In the present work, we perform several direct numerical simulation (DNS) cases to study the dynamics of a hydrogen diffusion flame embedded in the Taylor-Green Vortex (TGV). The evolution of flame and vortex is investigated for a range of initial Reynolds numbers up to 3200 with different mass diffusion models. We show that the vortices dissipate rapidly in cases at low Reynolds numbers, while the consistent stretching, splitting and twisting of vortex tubes are observed in cases with evident turbulence transition at high Reynolds numbers. Regarding the interactions between the flame and vortex, it is demonstrated that the heat release generated by the flame has suppression effects on the turbulence intensity and its development of the TGV. Meanwhile, the intense turbulence provides abundant kinetic energy, accelerating the mixing of the diffusion flame with a contribution to higher strain rate and larger curvatures of the flame. Considering the effects of non-unity Lewis number, it is revealed that the flame strength is more intense in the cases with mixture averaged model. However, this effect is relatively suppressed under the impacts of the intense turbulence.