Influence of discharge circuit parameters on the measurement of the minimum ignition energy of dust-air mixtures

In the measurement of the minimum ignition energy (MIE) of a dust-air mixture, an ignition spark is created by discharging the electric energy stored in a capacitor between two electrodes. In many cases, an inductance of 1 mH is added in the discharge circuit to improve the incendivity of the spark. In our study, a resistance (100 k Omega), instead of an inductance, was inserted and 15 powder samples were tested to investigate the influence of the circuit conditions. In the case of sensitive powders with MIEs that are smaller than 10 RI measured with 1 mH, the MIEs with no additional circuit element and those with inductance were almost identical : however, the resistance increased the MIEs. In the case of insensitive powders, however, the MIEs became smaller in this order : with no additional element, with the inductance, and with the resistance. Visual observation with a high-speed video camera revealed that the blast of air caused by the spark greatly affected the ignition mechanism of a dust-air mixture.