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Show droplets burning in stagnant oxygen (Fig. 8). This suggests liquid-phase cracking/coking within a portion of the droplets increasing the visible flame length and thus decreasing the extracted burning rates. This explanation is consistent with the highly radiative nature of the flame. Industrial Applications. Based on the results obtained from bench-scale tests, a global liquid-fuel burner was tested in a large industrial furnace. The injector position used was "25." The results indicated that replacing three of the twenty-two air-oil burners in a borosilicate glass-melting furnace with oxy-fuel burners showed improved fuel efficiencies. Fig. 9a depicts the heat input normalised with the pre-retrofit air-fuel burner heat input. The heat input from the air burners is plotted with squares, the total (air + oxy-fuel burner) heat input is plotted with triangles. The numbers 1, 2 and 3 at the abscissa indicate the sequential replacement of the three air burners by oxy-fuel burners. The total heat input trend can be seen to be downward. The temperatures measured in the bottom of the glass melt in front of the throat is shown in Fig. 9b. The strong increase in temperature as a result of only three oxy-fuel burners is apparent. These results should be seen in the light of the decreased heat input (Fig. 9a). Considering the large thermal inertia of the melt, the rate of temperature increase is large. Detailed thermal imaging analysis revealed that the closer proximity of the oxy-fuel flame to the glass melt in combination with uniform heating removed the insulating foam layer under the oxy-fuel flames. This resulted in a large increase in heat transfer to the melt. In addition to more favourable furnace operating conditions, a large increase in pack-tomelt ratios have been experienced during the tests. Finally, glass quality as measured by seed counts per 100 g of glass improved from 947 to 775 in only six days. CONCLUSIONS The rationale, design, and application of a new liquid-fuel oxygen burner are presented. Computational Fluid Dynamics, coupled with optical spray characterisation, were used to develop this concept burner. Detailed experimental information obtained in a rapid-heating test furnace confmned numerical calculations. In addition, these results indicate that good atomisation can significantly improve combustion performance and lower pollutant emissions. Improved heat-transfer characteristics leading to higher thermal efficiencies and improved product quality has been demonstrated in a commercial borosilicate glass furnace. ACKNOWLEDGEMENTS The authors would like to thank MEPA - Saudi Arabia for the studentship and financial support to one of the authors (A.D.A), BOC for financial support and permission for publication of the results and Mr. G. Cole for assistance in all experimental work. REFERENCES 1. Missaghi, M., Yap, L.T., Ahmadi, S.H., AI-Fawaz, A.D., Hampartsoumian, E., Pourkashanian, M. and Williams, A. "Experimental and theoretical studies of low NOx oxygen enriched natural gas combustion in process furnaces", International Gas Research Conference, 1992. 2. Pourkashanian, M., Yap, L. and Williams, A. "The use of oxygen enrichment in combustion technology", Applied Energy Research Conference, Swansea, 1989. |