Application of Furnace Analysis to Internal Combustion Engines

Numerous studies in the literature support the analytical description of furnaces which is commonly known as Furnace Analysis and which is summarized by the Firing Equation: Hf = Hf+H3/(a0*(1-H3/H3m)) where the Firing Constants, Hf , ef , and Hsm, are the Idle heat, the Intrinsic Efficiency, and the Maximum Output, respectively. This analytical model correctly predicts the common pattern of behavior observed in furnaces, that of a limiting or maximum output value as firing rate is increased and an optimum thermal efficiency at an intermediate firing rate. Based on observations of practical device performance, the Firing Constants are evaluated and are used to describe the thermal behavior of a furnace. The Firing Equation was developed assuming that wall and stack losses can be linearized with output. In the current paper, this analysis has been applied to performance data from a 3.4 liter, sequential fuel injected, six cylinder engine which was operated on a dynamometer. The results show that the Firing Equation can adequately describe the variation of output with frring rate, but that the typical assumptions about wall and stack loss dependence require modification. For the engine dynamometer data the essential features of the Perfonnance Curves, i.e. the variation of firing rate, Heat Utilization Factor and thermal efficiency with output, are described by the Furnace Analysis with these modifications in place.