Stratified combustion in recirculating flow

The thesis describes a study of mathematical modelling to predictthe combustion structure in a recirculating flow. The feasibility ofapplying stratified combustion principles in recirculating flow hasbeen investigated e~perimentally in a conical jet-stirred reactor. Theconditions for an increase in mass flow rate at blow-off and anextension of the lean burnt limit have been identified. Computermodelling is used as an aid to an understanding of the mechanism bywhich these are achieved,and contours of the aerodynamic parameters,species concentrations, gas temperature and volumetric heat releaserate are presented. Experimental and computed profiles of speciescompositions and temperature inside the reactor are compared and thedifficulties involved in accurate computer modelling of the system arediscussed.These difficulties reside predominantly in the source termsof the species conservation equations, where designation of suitableprobability density functions (pdf) presents many problems. A completetwo-stage global reaction scheme, based upon laminar flame data,represents the kinetics reasonably rigorously, and attention isfocussed upon the pdf problem. The uses of electrostatic probes togive some insights into this are described and the relationships betweenion currents, ion concentrations, and chemical heat release rates areexamined.