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Show Our intent in this paper is to focus on the application of Furnace Analysis to a different class of combustion devices, than has been previously demonstrated, that of internal combustion engines. Application of the Analysis to Furnaces and Engines Our approach will be to demonstrate the application of the analysis to steam plant boilers ftrst, then apply it to an internal combustion engine. Boilers: The boiler data come from the Pennsylvania State University's West Campus Steam Plant [10]. The data are for gas firing of several boilers from different manufacturers including Wicks, Babcock & Wilcox and Erie City with capacities ranging from 75,000 110,000 pph steam at 530°F and 250 psig. All but the Babcock & Wilcox unit use coal as the primary fuel and can be co-fired with oil and gas. Table 1 presents ftring data, flue gas analyses and flue gas temperatures. Figs. 2 and 3 show the fits of Eqs. (5) - (7) to the data in Table 1. The Firing Constants are the fitting parameters, which were determined by using the graphics software package Kaleidagraph 3.0. For the boilers, the wall loss is assumed to be constant, so the proportionality constant c in Eq. (2) IS zero. The Firing Constants each have a physical interpretation and can be used as a basis for comparison of combustion systems. The Idle Heat H/ gives a numerical value to the combination of losses that must be balanced for the system to be "ready" to deliver an output. The relative magnitude of H/ indicates. the degree to which heat losses are designed into a device as a necessary function, such as the water cooling of internal combustion engines to control engine temperature, or are inevitable but undesirable limitations caused by finite temperature differences with the surroundings, such as natural convective losses from the outer walls of a boiler. The theoretical maximum output Hsm indicates the range over which the useful output will continue to increase as the ftring rate is increased. This can be useful in judging the output range for which the device has a reasonable efficiency, since efficiency falls off to zero as the device approaches its theoretical maximum output (e.g., Eq. (6)). As shown by Essenhigh, if represents the upper limit to the operational efficiency for the device [8]. From the flue gas analyses and flue gas temperatures in Table 1, we can verify the Validity of a key assumption in the development of the Firing Equation, that of a linear relationship between the exhaust gas enthalpy and the useful output. To calculate the 7 |
