RESIDENCE TIME DISTRIBUTIONS IN A COLD, CONFINED SWIRL FLOW - IMPLICATIONS FOR CHEMICAL-ENGINEERING COMBUSTION MODELING

Residence time distributions (RTD) in a confined, cold swirling how ha ve been measured with a fast-response probe and helium as a tracer. Th e test-rig represented a scaled down version of a burner. The effect o f variation of flow velocities and swirl angle on the flow pattern in the near-burner zone of the laboratory furnace-model were studied. RTD results have been used to derive a chemical reaction engineering mode l for the mixing process. The model is based on a combination of plug flow reactors and continuous stirred tank reactors, which represent th e main how characteristics in regard of mixing in the near-burner zone . The model is well suited to handle mixing in complex flows with seve ral zones of recirculation. Simulated RTD curves compared well with th ose of the experiment at the two swirl numbers studied. Modelling of t he mixing is a prerequisite to handle the chemistry. A simplified, wel l characterised flow pattern makes it possible to investigate the impo rtance of mixing intensity on the (pollution) chemistry in furnaces. T he reactor model developed here will be the basis for the development of a chemical reaction engineering combustion model. (C) 1997 Elsevier Science Ltd.