Correlation between the electrical power of a slow contact break discharge and the ignition of an H2/air mixture

Abstract Contact break discharges generated by electrical equipment in potentially explosive atmospheres are typically obtained at low voltages below 30 V and low currents between 30 mA and 100 mA are a relevant ignition source. The electrical characteristics of these discharges, which are dominated by metal vapor, have been presented in previous works. However, the transition phase from a discharge to a thermochemical ignition has not yet been properly analyzed. This prevents a multiphysical model from being developed and evaluation criteria from being defined for the non-ignition or ignition of a discharge. Here, the correlation between the electrical power of the discharge and the ignition is analyzed and estimated with the aim of correcting this shortcoming. The development of the discharge and its ignition, which depend on the electrical power input and its temporal and spatial distribution, are monitored and data for the ignition limit is determined. Initial estimations are made for the ignition limit by considering two models. The first model computes the ignition limit in a simplified manner by using the measured power input and certain empirical coefficients, while the second appoaches regards the discharge in a more physical manner and implements a simplified but more detailed thermodynamic model. However, further investigations are necessary in order to ensure statistical significance for the results presented here.