Experimental and numerical study on the quenching limits and mechanism of small-scale H2 diffusion flames

Abstract

The quenching limits of small-scale H2 diffusion flame achieved by microtubes were studied experimentally and numerically. The experimental observation shows that the luminosity of small-scale H2 diffusion flame becomes ambiguous with decreasing fuel jet velocity. However, the OH radical in the flame can be detected clearly by using the planar laser-induced fluorescence (PLIF) measurement. The quenching limits of small-scale H2 diffusion flames at different inner tube diameters were obtained by OH-PLIF measurement and numerical computation with a detailed chemical mechanism. The computed and measured quenching limits show good agreement. The results show that the quenching mass flow rate decreases gradually with decreasing inner tube diameter. A power function relationship exists between the quenching mass flow rate and the inner tube diameter. The analysis of the computational results reveals that the quenching mass flow rate depends on the ratio between heat generation and heat loss, net fuel consumption ratio, the lower heating value of the fuel and total heat loss from the reaction-part of the flame. The decrease in the diameter of the reaction-part of the flame with decreasing inner tube diameter leads to a smaller quenching mass flow rate.