Environmental Engineering Reference
In-Depth Information
FIGURE 2.20 Chemical luminescence of HiTAC.
difference in the ratio of the spontaneous emission spectra of CH A-X(0,0) (431.5
nm), C 2 (516.5 nm) was observed at any point. As shown in Figures 2.18 and 2.19 ,
the domain of combustion reaction is distributed outside the fuel jet diffusion in the
state of a thin film in the vicinity of the burners, which is a typical shape of a diffused
flame. When the effect of entraining the in-furnace gas is much higher, it can be
considered that the fuel jet diffusion takes in the in-furnace gas before its ignition to
contain some concentration of oxygen, resulting in a form of premixed combustion
flame. It was reported by Weber and others 4 in the IFRF that, according to the results
obtained by measuring the in-furnace flow, the EGR (exhaust gas recirculation) to the
airflow is small in the vicinity of the burners, in the case of the distributed combustion
flame when fuel jetting is made parallel to the airflow. But the EGR at 3 m down from
the nozzle attains 400%. It may be conjectured that the existence of OH at the outer
side of the fuel is caused by oxygen being supplied dominantly by its diffusion from
the outside, and therefore a burned-gas recirculating effect in the vicinity of the burner
is relatively small. In the case of condition (e), which showed the lowest NO x , it can
be also confirmed from results (shown in Figure 2.21 ) obtained by measuring the OH
distribution at the lower portion of the flame on and after 385 mm from each burner,
that the combustion range is distributed not in a thin film state but in a cubic state,
compared with the state of distribution at the upper portion of the flame.
From these results, it can be judged that the reason no noticeable change is
found in the spontaneous emission spectra is that the EGR is small at the upper
stream portion of the flame. As for the cases of combustion conditions (d) and (e),
it can be also assumed that since the difference in NO x concentration between both
conditions is relatively small, the difference in oxygen concentration in the jet
diffusion due to the EGR is relatively small, resulting in showing none of the changes
in the spectrum. In other words, it can be interpreted that, in the case of the distributed
 
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