OCR Text |
Show -e-carbon monoxide -B-methane -0 - fonnaldehyde ---- - _ -0-- (7-- 0.4 0.6 0.8 1.0 1.2 1.4 Figure 2. Influence of equivalence ratio on species concentrations (0.1 sec residence time, 1200 K). average temperature would be expected to decrease with decreasing equivalence ratio. As the fuel-lean flammability limit is reached, the methane concentration would increase as the flame started to quench. In present calculation, the reactor temperature was held.constant at 1200 K, so that these temperature effects are not observed. There are many other types of analysis in which the fluid mechanics issues are greatly simplified or removed entirely. Beyond the PSR model present above other examples include the static (or closed) reactor, the plug flow reactor, and even the highly idealized laminar flame. Their applicability to practical combustion environments can be very useful, even if valid only under very limited conditions. For example, even in turbulent combustors, there is usually a laminar boundary layer near any cooled surfaces, and laminar flame analysis can be used to predict heat transfer to those surfaces, as well as the effects of flame quenching on those surfaces. If this technique is used, detailed chemical kinetic submodels can be employed, which is extremely important for these problems since it is commonly believed that such quenching may be responsible for production of P AH, dioxins and many other toxic chemicals in incineration and other systems. -5- |