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Show were 100J/kmol and 1012 m3 /kg. s(oxidizer),respectively. These values can be considered as appropriate in terms of the order of magnitude according to global kinetic data for typical hydrocarbon fuel combustion [7]. However, the present results suggest that the evaluation of reaction rate may need to be considered to obtain good agreement with the experimental data. Apart from the above argument, inlet turbulent properties are found to be sensitive to determination of flow field in the mathematical simulation. Although it is conceived that turbulent intensity remains constant with varying pressure levels, as reported in reference [8], further confirmation of the intensity level for each burner condition is necessary. The other possibility is the flame radiation model used in the simulation code. For the present calculation, the six-flux model was used with absorptivity and scattering coefficient kept constant regardless of pressure levels despite the physical fact that gas emissivity is pressure dependent. Nevertheless, the experimental results seem to indicate that the effect of radiative heat transfer is of secondary importance in determination of the flame pattern. 4. Burner Design Criteria Based upon information gained in the present experiment and various experience in the past, criteria are proposed here to establish a framework for rational burner design. Table 2 presents a summary of the design criteria for the high Reynolds number group burners tested here. The use of this criteria is to compare all data with that of a newly designed burner and to identify differences between them. By integrating the designer's individual experience to the criteria data, one can establish an optimum burner design. 4.1 Basic Data Basic data consists of specification data, design data and performance data. Specification data provides an outline of reformer burner specifications, some of which has been already mentioned in Section 1.2. Design data gives some important design values, such as firing density and flow Reynolds numbers. Firing density is directly relevant to compactness of reformer vessel, as it reduces the combustion chamber volume. For the present case, the firing density per chamber volume is calculated as 1,070kW/m3 , while the value is in the range between 500kW/m3 and 2,OOOkW/m3 for current reformer designs. The firing density per chamber cross sectional area is important to identify the shape of flames. A high value for this firing density implies that the flame must be long so as to avoid 12 |
