Flammability Limits of Hydrogen-Oxygen-Diluent Mixtures

Flammability limits of hydrogen-oxygen-diluent mixtures were determined in a 5-cm diameter, 1.8-m long tube, for upward, downward and horizontal prop agation of the flame. It was found that for fuel-lean mixtures, upward limits were nearly independent of the diluent type and concentration; downward limits showed a slight dependence on diluent type and concentration. Limits for fuel- rich mixtures were independent of the direction of propagation of the flame. In all cases, to a good approximation, horizontal limits lay midway between the upward and downward limits. It was also found that limits for fuel-rich mixtures were dependent on the oxygen volume fraction. Empirical correlations are presented to estimate the limits.