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Show considerable enthalpy by furnace heat transfer. This results in exceptionally low N O x emissions. The product recirculation is induced, rather than forced, driven by jet entrainment and shaped by furnace aerodynamics. A negative effect of this approach is a certain loss of combustion stability which is likely to restrict the range of practical utility to processes involving fairly hot furnaces. The problems that application of the burner poses for research are most intriguing, particularly in mathematical modelling. The combustion process here cannot, for example, be plausibly portrayed by classical flamelet theory. Prompt N O x may be prominent, and N O x "reburning" may be important. There is considerable matter, too, for experimental research and for theoretical analysis. W e currently have work underway on cold (physical) modelling, on more furnace studies, and on mathematical modelling. This has already produced a paper (Grandmaison, Yimer, Sobiesiak & Becker 1996) in which theory and cold modelling are combined to yield important insights on mixing and reaction in the field of the burner inside a furnace, and on the scaleup characteristics of the burner. 2. The burners tested As described in the patent application (Besick, Rahbar, Becker & Sobiesiak 1995), it is characteristic of the C G R I burner concept that it incorporates: • A ring, of radius r\. of round fuel ports, TV in number, of diameter D\. whose axes are at an angle, 0\. to the burner axis. • A ring, of radius A*2, of round air ports, N in number, of diameter Dj, whose axes are at an angle, 9i, to the burner axis. Typically Oz < 9\ and r-i < r\. • Uniform angular spacing of the alternating fuel and air ports about the burner axis. These features are illustrated in Fig. 1 for the case r\ - n, N' - 6. The values of the design parameters for the two burners employed in the present work are summarized in Table 1. Both burners have N = 7, and the second has r\ = r^. The model designations of these burners are C G R I / C A G C T - X B M 1 and C G R I / C A G C T - X B M 2 , or X B M 1 and X B M 2 for short, where X B M means experimental burner model. Both were built with mild steel bodies and stainless steel outlet porting. The burner bodies barely lasted the course of the trials reported herein, and were badly wasted by corrosion by the end. Although by then a reasonably adequate number of trials had been made for the immediate purposes of the research, this degradation effectively forced a conclusion to the work. W e have since built another burner, the X B M 3 , entirely of stainless steel, which allows even smaller fuel-port angles, and work is continuing under a new project with a different scope. The research burners have certain features, such as provision for variation of 6\, D\ and D2 in the X B M 2 and X B M 3 , that are unlikely to be used in production models. Because of the patent applications in process, construction details beyond the basic features shown in Fig. 1 will not be discussed in this paper. Although interesting to anyone wishing to build a burner, these details are unimportant for the aspects of burner performance here considered. The number N = 7 of pairs of fuel and air ports in the X B M 1 , X B M 2 and X B M 3 burners makes a comfortably compact array of jets. W e have designed a fourth research-style burner, which w e will in due time build and test, the X B M 4 , that allows N = 4 or 8. The latter, with N = 3 |