Catalytic removal of NO from post-flame gases in low pressure stagnation-point flames over platinum

Experimental NO profiles in H-2/O-2/NH3 stagnation point flames over platin um substrates are obtained with laser-induced fluorescence for a range of f lame equivalence ratios and substrate temperatures. This study generates ba seline data against which comprehensive gas-phase and surface chemical mode ls of NO destruction can be compared. The experimental profiles are compare d with the predictions of a one-dimensional stagnation how model that inclu des full gas-phase chemistry, multicomponent transport, and detailed surfac e chemistry. A baseline surface chemistry mechanism, assembled by using con ventional H/O heterogeneous chemistry and NO adsorption and dissociation fo llowed by N-2 desorption, provides good agreement with the experimental res ults for only a limited range of operating conditions. At low temperatures (425 K), the mechanism underpredicts NO removal, while at high temperatures (940 K) and fuel-lean conditions (Phi = 0.7) the mechanism overpredicts NO destruction. Addition of NH2 and N2O production to the surface mechanism d oes not improve the level of agreement. However, consideration of the recon struction of the platinum surface at high temperatures tends to shift the p redicted profiles closer to those observed in the experiment for the high t emperature cases. (C) 2001 by The Combustion Institute.