Effect of Microreactor Inlet Pressure

Elevated operating pressures have been shown to substantially extend the stable combustion regime of methane-fueled catalytic microreactors under steady-state operation [17], the reason being that the catalytic reactivity of CH4 on Pt follows a positive dependence on pressure [9]. A reduction in the ignition (fjg) and steady-state (fst) times is thus expected with rising pressure. This effect is illustrated in Fig. 8.5, where computed tig and fst times are plotted for Cases 1-10. 

The increased catalytic reactivity of methane on Pt at elevated pressures allows for significant fuel consumption at lower wall temperatures than those required at atmospheric pressure, thus facilitating an earlier microreactor ignition. This is evidenced in Figs. 8.6 and 8.7, where streamwise methane catalytic conversion rates and channel wall temperature profiles are plotted for Cases 1 and 5, atp = 1 and 5 bar, respectively. 

In comparison to Case 1, Case 5 exhibits more vigorous combustion at all times, from ignition till steady state (see Fig. 8.6). Both cases display a rear-end ignition, with the reaction zone gradually propagating upstream. With the propagation speed of the reaction front being controlled by the solid thermal diffiisivity 

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