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Show Conclusions The analysis presented here provides an semi-empirical means of describing the behavior of combustion and thennal systems. Its simple foundation in the First Law of Thennodynamics gives the analysis generality so that it can be applied to broad classes of systems ranging from materials processing devices such as glass tanks and kilns, to power generation devices such as boilers and internal combustion engines. Application of the analysis to engine perfonnance data was carried out in two stages. In the fIrst stage, fits of Eqs. (5)-(7) to the engine data showed departures from agreement that were identifIed as arising from a breakdown in the assumption of a linear relationship between losses and engine speed. In the second stage, accounting for quadratic variation of frictional power losses provided improved agreement between tha analysis and the data. - With sufficient perfonnance data and appropriate assumptions on how losses vary with the useful output, the analysis captures the essential features of device behavior, such as an asymptotic approach to a theoretical maximum output as the frring rate increases. The results of the analysis can be used in design considerations, such as to predict an operating condition for maximum efficiency. In addition, the fItting parameters have physical meaning and can assist in the comparison of different types of combustion systems and in more precisely targeting the associated, more-detailed, mechanistic analyses that are additionally needed. Acknowledgments The authors are grateful to E. J. Driscoll of the Office of Physical Plant at The Pennsylvania State University for supplying data from the PSU Steam Plants, and R.F. Wiltse, K.E. Deer and T. H. Zarger of General Motors' Powertrain Division for supplying engine perfonnance data. References 1. Hudson, J.G., "Heat Transmission in Boilers." Mech. Eng., 70, 449 (1890). 2. Orrock, G.A., "Radiation in Boiler Furnaces." Trans. ASME, 48,218 (1926). 3. Armstrong, H.C., "Characteristics of Furnace Curves as an Aid to Fuel Control." Mech. Eng., 144, 445 (1927). 4. Wohlenberg, W.J., and D.E. Wise, 'The Distribution of Energy in a Pulverized-Coal Furnace." Trans. ASME, FSP60-19, 531 (1938). 5. McAdams, W.H., and H.C. Hottel, "Heat Transmission." 2nd ed., McGraw-Hill, New York, 77-84 (1942). 17 |
