Spectroscopic Methods and Visualization Applied to Combustion Diagnoses - Novel Combustion Concepts for Sustainable Energy Development - page 177

B A

[K] [K]

ca.30 cm ca.30 cm

ca.3 m

[NO x ] in the exhaust
24

Burner

fuel

33 ppm

0.6 m 0.5 m

Air

fuel

B 1 m

A

furnace

8.0 m

Fig. 4 Soot temperature pro les during diffusion HITAC

high temperature island was not steady but instantaneous leading to the low NO x
level. During the diffusion combustion, the fuel and air are injected from distant
nozzles, followed by slow reactions due to a low oxygen concentration along with
mixing the gases.
Spectroscopic temperature measurements were made for non- or semi-radiant
combustion les

during coal gas premixed and diffusion combustions together with the thermo-
couple temperature pro

fl flames. Figures 5 and 6 show the C 2 vibrational temperature pro

les, respectively.
The spatial resolutions of the spectroscopic temperature pro les are much higher

than those obtained with the thermocouples. As in case of the heavy oil combustion,
highly structured temperature distribution is encountered during the premixed HI-
TAC, high-temperature zone localized around the injector while the temperature
uniformity is seen during the diffusion one.
The origin of the difference in the NO x level between the premixed and diffusion
HITACs was also surveyed by directly measuring of spontaneous emission of
radiation from thermally excited NO molecules in the HITAC field. Figure 7 shows

the spectral intensity pro les of NO spontaneous emission of radiation.

The combustion conditions are the same as in Figs. 5 and 6 .