A versatile numerical tool based on the open-source framework OpenFOAM has been developed in this paper for modeling time-accurate,low-Mach number reacting flows,with a particular interest in small-scale flames.This tool consists of a gas-phase Navier-Stokes solver and a solid-wall heat conduction solver which can be implemented alone,or used together in a coupled means to reveal the small-scale combustion's characteristics of significantly enhanced flame-wall thermal coupling.Validation works has proved that the tool is capable of reproducing experimental flames at various scales (from conventional to small scales),including well-recognized micro-flame features in literature such as three modes of premixed flame dynamics (weak flames,flames with repetitive extinction and ignition,and stable flames).Then,an experimentally-already-found but rarely-simulated unique phenomenon of diffusion flame street is successfully reproduced with well-captured flame structures.Moreover,the conjugate heat transfer model with the specific formulation of solid-wall heat conduction enables an attempt to simulate a novel,thermally-orthotropic combustor with its axial thermal conductivities superior to the transverse ones.Finally,computational performance of the developed OpenFOAM solver is compared to that of the previously-used compressible flow solver Eilmer.The OpenFOAM solver is found to show better wave-damping abilities for overcoming acoustic wave effects at the initial stage of simulations,and is much more efficient in terms of the computational cost.