Bench-scale tests on PMMA fires with water mist

摘要

The effects of water mist on solid fires are more complicated than on liquid pool fires. Both the smoke and heat release rates would be very different. In this paper, the action of water mist on bench-scale solid fuel polymethylmethacrylate (PMMA) fires in a confined space under different external radiant heat fluxes has been studied. Small-scale PMMA fire tests with water mist application were developed in a cone calorimeter. Extinguishing mechanisms including oxygen displacement and cooling of the gas phase and fuel surface were studied. Water mist was generated by a single pressure nozzle in a cone calorimeter. Physical characteristics of the water mist were measured by Laser Doppler Velocimetry or the Adaptive Phase Doppler Velocimetry system (LDV/APV system). The heat release rate, oxygen, carbon dioxide, and carbon monoxide concentrations and other important parameters of the interaction under various conditions were measured. The results illustrated that water mist would suppress the diffusion flames induced by burning PMMA in a confined space by oxygen displacement, evaporation cooling and radiant heat attenuation. Combustion might be enhanced through expansion of the mixture and chain reaction. Suppression plays a dominating role when water mist of sufficient volumetric flow rate is applied. The flame can be suppressed more easily under poorer ventilation. Although only small-scale solid fuel PMMA fires were taken as examples to demonstrate the test, similar working principles also apply to other polymers.