This paper reports an investigation on the influences of air−fuel injection momentum rate and the air−fuel premixing on the moderate or intense low oxygen dilution (MILD) combustion in a 20-kW recuperative furnace. Various patterns of partially and fully premixed reactants have proven experimentally to work extremely well in the present furnace. H2 recorded for a variety of equivalence ratios at a firing rate of 10 kW. The present numerical study suggests that there is a critical momentum rate of the inlet fuel−air mixture below which the MILD combustion cannot occur. Also, it is revealed, both experimentally and numerically, that, above the critical rate, both the inlet fuel−air mixedness and momentum rate impose insignificant influence on the stability of and emissions from the MILD combustion.
Impacts of initial conditions on the characteristics of premixed moderate or intense low-oxygen dilution (MILD) combustion from a single jet burner in a laboratory-scale furnace are investigated through Reynolds-averaged Navier–Stokes (RANS) modeling and experiments. Different initial conditions examined include the area of the nozzle (A), equivalence ratio (Φ), thermal input (P), and initial dilution of reactants (f). Very low emissions of NO
x
, CO, and H2 are measured for the MILD conditions when the furnace is operated under the premixed mode. The numerical results have shown that premixed MILD combustion can occur at the present furnace and burner system only when Re exceeds a critical value (Re
c). When Re ≥ Re
c, a stable MILD combustion can be established, irrespective of the variation of A, Φ, or f. The diagram of the stability limits for the premixed MILD combustion based on the furnace temperature and recirculation rate is also presented.
The development of the time-translation operators in a matrix element of an arbitrary operator is examined. It is noted that we may interpret time as evolving from some remotely early time (t0) to a time in the far future (t∝) and then back to (t0). Using this interpretation, a perturbation expansion is developed for Green's functions defined along this path and a separation of the two-particle interaction terms into self-energy parts and single-particle Green's function terms is justified for quantities on this path. A connection is established between the real-time Green's functions and the Green's function defined along the path, thereby yielding a perturbation expansion for the real-time functions and a justification of the separation of the interaction terms in the equations of motion for the real-time quantities. The transport equations of Kadanoff and Baym are derived without resorting to an analytic continuation from imaginary times and without the correction terms of Fujita.
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