Explosion behavior of nonuniform hydrogen/methane/air mixtures in the presence of copper foam

Abstract

The effect of copper foam on the explosion characteristics of nonuniform hydrogen/methane/air mixtures with different hydrogen volume fractions (φ) and diffusion times (DT) was investigated in a closed duct. Copper foams with different PPIs (pores per inch): 0 PPI, 20 PPI, 40 PPI, and 60 PPI were used, where 0 PPI refers to the case where there is no copper foam in the duct. The results show that a triple flame is observed in nonuniformly mixed hydrogen/methane/air mixtures after the hemispherical flame and finger flame stage, rather than the traditional plane flame and successive tulip flames. Upstream of the copper foam, the presence of the copper foam has no effect on the flame evolution process in uniformly mixed hydrogen/methane/air mixtures but affects the shape of the triple flame in nonuniformly mixed gas. The flame front develops numerous folds and cellular structures after it through the copper foam, and the flame velocity and overpressure increase rapidly. When the PPI of the copper foam is increased, the flame downstream of the copper foam becomes more disordered and irregular, and the maximum flame velocity and maximum overpressure initially increase and then decrease with increasing PPI. The maximum flame velocity and maximum overpressure are obtained in uniform and nonuniform hydrogen/methane/air mixtures when copper foams with 20 PPI and 40 PPI are used, respectively. The results provide experimental evidence for preventing and controlling hydrogen/methane fuel explosions.