An experimental and two-dimensional modeling investigation of combustion chemistry in a laminar non-plug-flow reactor

Abstract

Laminar flow reactor design is generally limited to small tube diameters to ensure radial species homogeneity. Under such conditions, the chemistry can be conveniently described with one-dimensional kinetic modeling despite the existence of a parabolic radial velocity profile. In this study, experimental data are presented for dilute CO/H 2 O/O 2 and CH 4 /O 2 reaction baths in a laminar flow reactor under non-plug-flow conditions at atmospheric pressure and high temperatures (1000–1450 K). Measured species concentrations sampled along the centerline axis of a 3-cm-diameter reactor are compared with calculations from a two-dimensional model that is coupled with well-calibrated detailed kinetic mechanisms from the literature, and that takes into account radial diffusion transport and the development of the laminar velocity field. The good agreement that is observed between the experimental data and the model calculations extends the conditions under which laminar flow reactors can produce accurate data for investigating combustion chemistry. Species Damköhler numbers ( Da i ), defined as the ratio of the characteristic radial diffusion time to the characteristic reaction time of a species i , are calculated from the model results and used to characterize the extent of departure from plug flow conditions. The results suggest that for systems where the minimum Da i exceeds 40, radial mass transport becomes locally negligible such that plug flow behavior exists along the centerline stream on the timescale defined by the local velocity.