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Show -13- IFRF infrastructure, as a major portion of the work was executed at the CEGB Marchwood Laboratories. Furthermore, the investigation report provided a wealth of detailed measurements on which several workers within the IFRF Membership have been basing the development of mathematical models. However, a major conclusion reached during the 1981 determination of IFRF Members' long term technical objectives was, that these studies would be more fruitfully continued in terms of detailed investigations of various aspects of the "near field" of flames, i.e. the processes which occur within, circa, the first two burner diameters downstream of the burner, the argument being that if these processes were well understood, then the ability to scale the results of semi-industrial scale experiments would follow. It was noted during the subsequent planning that the majority of work undertaken at Umuiden concerned short intense, type II flames produced from burners employing swirling flows as shown in figure 13. Thus it was decided to concentrate on these relatively complicated flames. An important feature of a type II flame is the internal recirculation zone (IRZ) situated in the "near field" of the burner. This aerodynamic effect is achieved typically by imparting swirl to the combustion air (for example using a vane swirler) and is instrumental in recycling hot combustion products to the region at which, for example with pulverised coal firing, the incoming primary air/pulverised coal stream mixes with the secondary air in order to provide heat; - to effect the initial devolatilisation process; - for a source of ignition for the mixture of the products of devolatilization and the combustion air. As already indicated, the processes which occur in the near field are extremely complex and in many respects not understood in detail. This |