Experimental investigation on the scale effects on diffusion H2/air flames in Y-shaped micro-combustors

In the present study, characteristics of diffusion H-2-air flame in three Y-shaped cylindrical micro-combustors with a diameter of d = 1, 2 and 3 mm were investigated experimentally. The mixture was ignited near the exit of a 200-mm long horizontal channel. First, it is found that more flame propagation modes appear in the combustor with d = 2 mm. Moreover, noise emission commences earlier in larger combustors. Two stages of noise emission are detected in the combustors with d = 2 and 3 mm, whereas only one stage appears under d =1 mm. In addition, the mean flame propagation speed is the minimum in the combustor with d = 2 mm. Furthermore, the results show that the length of edge flame becomes longer in the combustor with a larger diameter. Interestingly, traveling isolated flame cells, which is also termed traveling flame street, is observed in the micro combustors with d = 1 mm. Finally, the regime diagrams of flame propagation modes are drawn for the three micro-combustors. In conclusion, the present study not only reveals the relationship between flame characteristics and physical and geometrical parameters, but also provides useful guidance for the design of micro -combustors. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.