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Show deteremined was 1.5. This procedure, likewise, provided values of the fitting coefficients, bo and Co. With the Idle wall loss determined, a value of the Idle heat was then obtained, using Eq. 7, which gave a value of 1.9. This completed determination of the firing parameters needed for the remaining performance curves. Firing Curve and Total Exhaust Curve. These are shown in Figs. 6 and 7 which show both the original measurements (from Table 1) and the values corrected to 25% Excess Air. The graphs includes a calculated curve using Eq. 1, with the parameter n° given by Eq. 11. As these show, the agreement for both is good. However, it may be noted at this point that these curves are substantially insensitive to changes in parameter values. Efficiency and HUF. Figure 8 illustrates the last two performance curves, for, respectively, the operational thermal efficiency, 11, defined by: 11 = HJHr; and the Heat Utilization Factor, n, defined by Eq. 2. The back-plotted curves are calculated from the relevant equations using the coefficients obtained from the previous graphs: Significantly, both these graphs are very sensitive to small changes in parameter values, unlike nearly all the other curves. The HUF curve is of particular interest as it shows two important charateristics: the first is that it is slightly sigmoid, and the second is that the curve is reasonably approximated by a straight line over most of its range. The straight line is the first approximation defined by Eq. 2 when the Intrinsic Efficiency parameter, n°, is a constant. The sigmoid behavior is essentially second order departure from linearity and it is due jointly to the curvature of the specific enthalpy defined by Eq. 9 and to the quadratic behavior of the wall loss. The departures from linearity are governed by the dependence of n° on output, defined by Eq. 11 . This can otherwise be represented by the ratio: (nao/nO); and its departures from unity. This is illustrated in Fig. 9. 6. Discussion and Conclusions. The most immediate conclusion from the foregoing results is the demonstration that the equations presented are reasonably well supported by the (randomly selected) experimental results used to test them. 12 |
