= 0.833 (see chapter IV).
= 0.714.
Work carried out by other researchers shows that the dependence of thermal-NO with temperature is strong and becomes significant above 1,400 °C (Gupta (1992)) . The flame temperature profiles obtained experimentally (see chapter V) show that such temperatures are exceeded in sections of the combustion chamber even when the furnace wall temperature was set at 900 °C. However, thermal-NO seems unlikely to be a contributor to the formation of NO as an evident direct relationship exists between fuel-N content and NO formed and emitted from the fuels studied (see Figures 39 and 40). Although flame temperature profiles were not obtained for fuel G1 it is deemed that they would not differ greatly from those of fuel M1. Since thermal-NO is mainly dependent on flame temperature (and also on residence time), similar levels of NO formation would be expected from both fuels, regardless their nitrogen content. In addition, the rates of formation of NO are different for both fuels (higher for M1, which has the greater fuel-N content) in the intermediate stages of the flame, between 100 and 400 mm. Thermal-NO would be formed at similar rates.
Experimental work was performed during the course of this thesis in order to determine the amount of thermal-NOX that is formed in the drop-tube furnace. This work is reported in chapter IV. A low-nitrogen fuel was burned at the experimental conditions used in this chapter. Only a minor amount of thermal-NO (approximately 4 ppm-wet) was detected at 1,200 °C furnace wall temperature and = 0.833 (see chapter IV).
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