What effect does temperature have on the formation of nitrogen oxides in engines?

The formation of nitrogen oxides (NOx) in engines is significantly influenced by temperature. At higher temperatures, combustion reactions become more vigorous and provide the necessary energy for nitrogen (N₂) and oxygen (O₂) in the air to react and form nitrogen oxides. This process is facilitated by the increased kinetic energy of the gaseous molecules, which enhances the collision frequency and energy of these molecules, leading to the production of NOx.

In the context of engines, the combustion chambers reach very high temperatures, typically above 1200°C, which is optimal for this reaction to occur. Thus, the relationship between temperature and NOx formation is direct; as the temperature rises, so does the formation of nitrogen oxides.

Lower temperatures, on the other hand, would reduce the energy of the reactants and thus decrease the likelihood of formation of nitrogen oxides. The impact of temperature on the efficiency of fuel use is relevant, but it is the high temperatures specifically that drive the formation of these harmful pollutants.