Investigation of colorless distributed combustion regime using a high internal recirculative combustor

Abstract

This study aims at investigating the combustion characteristics of methane and a hydrogen-rich fuel on distributed regime in a combustor with high internal recirculation as distributed regime can achieve with highly internal entrainment. The model validation was first taken place with the existing experimental results under non-reacting conditions, and it is demonstrated that the mean velocity profiles predicted are in satisfactorily good agreement with the existing data in the combustor. Then, the methane and the hydrogen-rich fuel were consumed at an equivalence ratio of 0.8 and a thermal power of 10 kW under distributed conditions which means that oxygen concentration in the oxidizer is reduced from 21% to 15% along with internal entrainment for each fuel used. The results showed that the velocity magnitudes increased in the combustor with decrease in oxygen concentration because of diluent introduction. Moreover, distributed regime enabled uniformly temperature field inside the combustor together with the ultra-low NO X values with introducing the diluent. In addition, one can say that the maximum temperature and the outlet NO X values (1800 K and 27.60 ppm at 21% O 2 – 1450 K and 0.05 ppm at 15% O 2 for methane, 2000 K and 32.47 ppm at 21% O 2 – 1700 K and 0.19 ppm at 15% O 2 for the hydrogen-rich fuel) were relatively higher while combusting the hydrogen-rich fuel compared to those of methane due to the presence of hydrogen. However, It is concluded that distributed regime provided uniformly temperature fields and ultra-low NO X levels even the hydrogen-rich fuel is used. • Colorless distributed combustion was investigated using a recirculative combustor. • External/internal recirculation zones were obtained in the combustor. • Velocity profiles were highly affected with highly internal recirculation. • More uniform thermal fields and ultra-low NO X emissions were achieved.