Air/fuel mixing

Since 1981, three-way catalytic systems have been standard in new cars sold in North America.6,280 These systems consist of platinum, palladium, and rhodium catalysts dispersed on an activated alumina layer ( wash-coat ) on a ceramic honeycomb monolith the Pt and Pd serve primarily to catalyze oxidation of the CO and hydrocarbons, and the Rh to catalyze reduction of the NO. These converters operate with a near-stoichiometric air-fuel mix at 400-600 °C higher temperatures may cause the Rh to react with the washcoat. In some designs, the catalyst bed is electrically heated at start-up to avoid the problem of temporarily excessive CO emissions from a cold catalyst. Zeolite-type catalysts containing bound metal atoms or ions (e.g., Cu/ZSM-5) have been proposed as alternatives to systems based on precious metals. 

The function of a burner is to mix oxygen, in the form of air, with the fuel so that the fuel will burn more efficiently. Burners are available in a variety of different designs, all engineered with the intent to maximize air/fuel mixing efficiency, and in more recent times we have the added concern of also minimizing the formation of atmospheric pollutants. Please be aware that fuel will burn at the end of a pipe with no burner at all but the combustion will be far from efficient. 

Z. Han, L. Fan, and R. D. Reitz, Multidimensional modeling of spray atomization and air-fuel mixing in a direct-injection spark-ignition engine, SAE Technical Paper 970884, Society of Automotive Engineers, Warrendale, 1997. 

One of the more common factors causing high oxygen levels in flue gas at the absolute combustion point is poor air-fuel mixing. To promote air-fuel mixing, the following parameters should act as a guide ... 

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