OCR Text |
Show increased presence of carbon dioxide in the fuel mixture not only eliminates knock effectively but also reduces the energy release rate throughout. Increasing the extent of the diluent in the fuel results also in a sharp increase in the concentration of the unconverted methane in the exhaust. This is a reflection of the relative slowing down of the combustion processes and the narrowing of the effective flammability limits leaving increasing proportions of the charge unconsumed [14]. The bulk of the carbon dioxide in the fuel acts as a diluent and does not suffer changes. However, the carbon monoxide exhaust concentrations tend to increase somewhat, both a reflection of the partial and incomplete oxidation precesses at light load and the increased contributions of factors such as carbon dioxide dissociation at high loads. Increasing the pilot quantity and quality tends to be quite effective in reducing the exhaust emissions of the methane and carbon monoxide but may increase the oxides of nitrogen [14]. Acknowledgements This contribution has drawn freely and extensively on the work of numerous ex-students and colleagues to w h o m the authors are grateful. In particular they wish to acknowledge the contributions of Messrs Y. Al-Alousi, N. Amoozegar, R. Gustafson, A. Hanafi, L. Jensen, B. Soriano, G. Zhou, B. B. Ale and M . Karbassi. The financial assistance of Natural Sciences and Engineering Research Council of Canada (NSERC) and Canadian Imperial Oil Company is gratefully acknowledged. References 1. Karim, G A. , Hanafi, A. S. and Zhou, G., "A Kinetic Investigation of the Oxidation of Heating Value Fuel Mixtures of Methane and Diluents", Proc. 15th A S M E / E T C E Conference, Houston, Texas, January 1992, published in PD-Vol. 41, Emerging Energy Technology-1992, ed. S. R. Gollahalli, p. 103. 2. Karim, G. A. and Hanafi, A S . , "An Analytical Examination of the Partial Oxidation of Rich Mixtures of Methane and a Oxygen", Proc. of A S M E 14th Annual Energy-Sources Technology Conference & Exhibition, Houston, Texas, January, 1991, published in Fossil Fuel Combustion - 1991, ed. R. Ruiz, PD-Vol. 33, p. 127. 3. Zhou, G. "Analytical Studies of Methane Combustion and the Production of Hydrogen and/or Synthesis Gas by the Uncatalyzed Partial Oxidation of Methane", Ph. D. Thesis of University of Calgary-Mechanical Engineering, 1993. 4. Coward, H. F. and Jones, G. W., "Limits of Flammability of Gases and Vapours", U S Bureau of Mines Bulletin No. 503, 1952. 5. Wierzba,L, Bade Shrestha, S. O. and Karim, G A. "An Approach for Predicting the Flammability Limits of Fuel/Diluent Mixtures in Air", Journal of the Institute of Energy, 1996, Vol. 69, pp. 122-130. 6. Wierzba, I. and Karim, G. A., " A Predictive Approach for the Flammability Limits of Methane- Nitrogen Mixtures", Transactions of the ASME/Journal of Energy Resources Technology, December, 1990, Vol. 112, p. 251. 11 |