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Show 1. Introduction. This paper describes the performance characteristics of a small laboratory furnace with a focus, particularly, on the influence of stoichiometry on the variation of Firing Rate with Output, and on the variation of the specific exhaust enthaply with Output, as predicted by Furnace Analysis. The context of these measurements is with regard to the need to predict such performance characteristics for furnaces and engines in general, and the need for verification of the phenomenological predictive models developed in Furnace Analysis. Furnace Analysis is a theoretical study of the thermal performance characteristics of furnaces and engines that originated with the Hudson-Orrock equation for boilers, initiated by Hudson [1] in 1890, with an extension by Orrock [2] in 1926. In subsequent developments, as described in Reviews [e.g., see 3-5], the focus was on extension from boilers to furnaces in general, and later to engines. With the advent of massive computational facilties, particularly in the last 20 years, the types of phenomenological studies carried out by the Furance Analysis approach were expected to be superceded by detailed mechanistic modelling. Increasingly, however, it has been recognized that there is scope or even need for parallel analysis using phenomenological methods, jointly, for speed and for generality. The framework of such results also then provides a suite of approximate targets for the more complex and detailed computer modelling. Consequently, there has been revived interest in the Furnace Analysis approach, with particular attention to its limitations. One limitation has been known to be description of the exhaust enthalpy profile, which is examined inter alia in this paper; this then permits focus on the principal problem addressed here, as identified above, of the influence of stoichiometry. 2. Background. It has been known for many decades, following the Hudson-Orrock boiler studies, and ever since Armstrong's pioneering experimental furnace studies in 1927 [6], that the thermal efficiency of an industrial furnace or engine is a strong function of the useful output or delivered load. The efficiency rises from zero at zero load, or Idle, to a 2 |