Chapter 11—Cryogenics

Abstract

SUMMARYThe dilution e!ect of air stream according to agent type on #ame structure and NO emission behaviour is numerically analysed with detailed chemistry. The adopted fuel is hydrogen diluted with the argon of volume percentage 50 per cent and the volume percentage of diluents (H O, CO and N ) in air stream is systematically changed from 10 to 50. The radiative heat loss term, based on an optically thin model, is included to clearly describe the #ame structure and NO emission behaviour, especially at low strain rates.The e!ect of dilution of air stream on the decrease of maximum #ame temperature varies as CO 'H O'N . The qualitative tendency of the numerically predicted mole fractions of H, O and OH is well described using a simpli"ed formula, based on a partial equilibrium concept. It is seen that the H O addition to air stream is the most e!ective for reducing NO emission. In the case of the addition of H O and N the NO emission behaviour is governed by the thermal e!ect and in the case of CO addition it is governed by both the thermal e!ect and the chemical e!ect. But the chemical e!ect, which is mainly attributed by the Fenimore mechanism to the breakdown of CO , is much more predominant in comparison with the thermal e!ect.