DNS analysis of a cubic meso-scale combustion chamber: I. Cold flow topology & dynamics

A quasi-cubic 8×10×88×10×8 mm 33 meso-scale air/methane asymmetric whirl combustion chamber is analyzed. The study is two-fold and this paper is the first part, dealing with cold (non reactive) flow analysis. The aim is to get an insight of this particular flow dynamics to validate the numerical procedure against experimental results and to highlight the impact of the reaction on the dynamics. In this first paper, two different flow rate cases are considered. Practical–numerical–issues arising from the strong inhomogeneity of the flow do not allow for complete uniform statistical convergence of the computations: only local convergence in fast evolving zones could be reached. Two velocity components in a planar section can be compared to PIV results, allowing for partial validation of the computations. Cold flow topology and dynamics analysis allow to evidence: (i) strong shear zones between the air jet and the Central Vortex Zone (CVZ); (ii) reverse flow between air jet and wall, enhancing local air/fuel mixing; (iii) ring-shaped structures at the vicinity of the impinging jet (on the upper face of the chamber); (iv) presence of secondary vortices in the bulk of the chamber, for the higher flow rate case.