ENGINE COMBUSTION

The NOx formation in hydrogen-air combustion in a pulse detonation engines (PDEs) is investigated numerically and validated with experimental data. The calculations are based on axisymmetric Euler equations and a detailed combustion model consisting of 12 species and 27 reactions. A multi-level, dynamically adaptive grid is used to resolve the structure of the detonation front. The calculated NO concentrations were in good agreement with experimental measurements obtained at two operating frequencies and two equivalence ratios. Further calculations studied in detail the effects of equivalence ratio and residence time on NOx formation under ambient conditions. The results show that NOx formation in the PDE is minimized by running lean or rich mixtures and using the shortest possible detonation tubes. NOx emissions for very lean or very rich mixtures are relatively insensitive to residence time. PDE operation at near-stoichiometric equivalence ratios results in very high NOx levels. However, the NOx emission parameter drops significantly for lean or rich mixtures, reaching values comparable to those obtained with current gas turbine engines.