The interaction of liquid reacting droplets with the pulsating flow in a Rijke-tube combustor

This paper presents the results of a theoretical investigation on the characteristics of a reacting liquid droplet in the self-generated oscillatory flow of a Rijke-pulse combustor. The droplet motion equation, accounting for droplet evaporation due to combustion, was solved using a fourth-order, Runge-Kutta method. The model was applied to a Rijke-type, alcohol-fired combustor for which experimental data exist to be used as entrance parameters. The main conclusions derived from this study are (I) for a range of droplet initial velocity, pulsating flames of liquid fuels are shorter than the corresponding steady flames because of a reduction in lifetime of droplets with the same initial diameter in the pulsating flow, (2) for a range of droplet initial diameter, time-resolved heat generation rates from pulsating sprays exhibit a preferred frequency equal to twice the frequency of the pulsating flow, and (3) droplet initial diameter, droplet initial velocity, and location of the spray in the tube influence the excitation and maintenance of acoustic oscillations in a Rijke-type combustor based on evaluation of the Rayleigh integral over time and volume in the combustor. The theoretical results presented and discussed herein are supported by experimental observations. Copyright (C) 1997 by The Combustion Institute