Correlation between the electrical power of a slow contact break discharge and the ignition of an H2/air mixture. (January 2022)

• Record Type: Journal Article
• Authors: Uber, Carsten; Franke, Steffen; Barbu, Bogdan; Hilbert, Michael; Berger, Frank; Uhrlandt, Dirk; Lienesch, Frank
• Is Part Of: Journal of loss prevention in the process industries. Volume 74(2021)
• Publication Date: 2022-01
• Subjects: Contact break discharges -- Ignition limit -- Electrode quenching -- Metal vapor discharge -- Contact opening-discharge; Chemical industries -- Safety measures -- Periodicals; 660.2804
• DOI: 10.1016/j.jlp.2021.104620
• Languages: English
• ISSNs: 0950-4230

Abstract

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 approaches 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. Highlights: Simplified considerations on quenching due to geometrical constraints of the ignition process due to slow contact break discharges. Simplified estimation of the power loss due to the heat balance of the ignition process due to slow contact break discharges. Quenching effect of different electrode sizes on the temperature of the hot gas kernel.