Experimental study on the flame extension and risk analysis of a diffusion impinging flame in confined compartment

In this work, an experimental investigation on a diffusion impinging flame in a confined compartment was performed. The objective was to study the influence of confinement on the behavior of a flame impinging the ceiling and to deduce the auto-ignition risk of the smoke produced in the confined compartment. For this, configurations with five confinement levels were constructed by the condition of windows and/or door in the compartment and the variation of the heat release rates was made between 0.5 and 18.6 kW. To evaluate the flame morphology and flame extension length, an image processing method based on the direct linear transformation algorithm and the fire segmentation algorithm was adopted. From the experimental data, it was shown that the heat release rate of 4.6 kW presents a critical value for the flame extension in confined configurations, which corresponds to the equivalence ratio of the enclosure greater than 1, highlighting an under-ventilated environment. In addition, an auto-ignition risk analysis of smoke with unburnt gas in the compartment was carried out. The concentration and temperature of these gases were compared to the lower flammability limits and the auto-ignition temperature. It was observed that there was auto-ignition risk of the smoke under the ceiling, especially in the confined compartment of equivalence ratio greater than 1. Under these conditions, it is possible to have a fire spread to another compartment.

Heat Transfer Characteristic for Premixed Flame Jet from Swirl Chamber

The objective of this research is to study flame structure and heat transfer characteristics for the premixed flame jet from the swirling chamber. In this study, LPG and air was utilized as gas fuel and oxidizer for a premixed flame. The equivalence ratios () of LPG and air were considered at 0.8, 1.0, and 1.2 under a Reynolds number Re = 4,000. The swirl flame was generated by double tangential inlets in cylindrical chamber. The diameter of chamber was fixed at D = 20 mm and the hydraulic diameter of the inlet was Dh = 5 mm. In this study, the effect of chamber geometry on flame structure was investigated by varying the chamber from H = 2.2Dh to 7.0Dh. The structures and temperature of the free flame jet was recorded with camera and measured with a thermocouple. The heat transfer rate of impinging flame jet was also measured at distance from chamber outlet to flame impingement surface varying from L = 4Dh to 10Dh. The results show that the maximum of flame temperature occurs at =1.2. Impinging flame jet for case of chamber height at H = 4.6Dh and impingement distance at L = 4Dh give the highest heat transfer for all equivalence ratios due to the reaction zone of combustion reached to approach near the heat transfer surface.