Hetero-/homogeneous combustion of hydrogen/air mixtures over platinum at pressures up to 10 bar

Monoliths: A Review of the Basics, Preparation Methods and Their Relevance to Oxidation

“…Alternatively, syngas can be converted to power in a more portable/smaller scale. This can be achieved by catalytically stabilized thermal combustion, which is currently being investigated by e.g., the Combustion Research Group at the Paul Scherrer Institute (Villigen, Switzerland) [251][252][253][254][255][256][257][258][259]. In these studies, the researchers focus on converting fuel/syngas mixtures, via a combination of heterogeneous-homogeneous reactions, over platinum-based catalysts coated onto micro-channels.…”

Effects of heterogeneous–homogeneous interaction on the homogeneous ignition in hydrogen-fueled catalytic microreactors

“…Note that the latter (high pressures) is far in excess of the second explosion limit of hydrogen-air mixtures [79,80]. In addition, in the previous works of Mantzaras et al [64] and Ghermay et al [66] who computed the homogeneous ignition delays for hydrogen-air mixtures in a constant pressure batch reactor using the SENKIN package of CHEMKIN for initial temperatures ranging from 950 to 1250 K, the homogeneous reactivity of hydrogen is not a monotonic quantity of the pressure, but there is a monotonic increase of homogeneous reactivity or a monotonic decrease of homogeneous ignition delay with increasing pressure at equivalence ratio 4 ¼ 0.3 and initial temperatures above 1200 K. Therefore, for the stoichiometric mixture in the range of higher temperatures discussed in the present work, a simple assumption is made that the homogeneous reactivity of hydrogen is enhanced or the homogeneous ignition delay is decreased with increasing pressure. Although this assumption is not accurate enough, but it is worthwhile to make a preliminary exploration and the further study is an interesting task for the future.…”

“…4 bar at equivalence ratio 4 ¼ 0.28) because of the combined effects of the intrinsic gasphase hydrogen kinetics and of the heterogeneously produced water acting as very efficient third body in radical gas-phase chain terminating reactions [64e66]. In addition, the impact of transport, associated with the large diffusivity of hydrogen, on the aforementioned homogeneous inhibition is modest [64]. Moreover, at lean stoichiometries, the heterogeneous chemistry is inhibited by rising pressure [67]; however, when the temperature is above the catalytic ignition temperature (light-off temperatures are in the range of 340e380 K at atmospheric pressure and lean stoichiometries [78]), the dependency of heterogeneous reactivity reverses, indicating an overall positive pressure order of approximately 0.97 [67].…”

Hetero‐/Homogeneous Combustion

“…The combustion of fuel-lean (j 0.32) hydrogen/air mixtures over polycrystalline platinum has been studied in the test rig of Figure 8.6 for pressures of up to 10 bar and 950 T w 1220 K [17,60]. Owing to the low Lewis number of hydrogen, the reactor entry was water-cooled to suppress superadiabatic surface temperatures, as discussed in the context of Figure 8.4.…”

“…High-pressure studies were reported more recently [60] using the gas-phase scheme of Li et al [63], especially developed for elevated pressures. It was shown that gaseous combustion is largely suppressed for p !…”