| As one of the basic fire types faced by humans,electrical fires can cause huge economic losses and casualties.When the wire is overloaded,the fire hazard generated by the wire is often higher than that of other types of fires,which brings greater harm.To better understand the heating and combustion characteristics of the overloaded wire,the overloaded wire inclination device was designed and experiments were carried out in various working conditions.This paper uses a combination of theory,experiment,and numerical simulation to study the overloaded combustion characteristics of the wire,to provide a theoretical basis for the design of fire-resistant wire.The systemic in-depth research is mainly carried out from the following three aspects.The electrical fault simulation test benc.h and the wire inclination device are used to simulate the overloaded wire fault experiment with the inclination angle of 0°～90° under the current condition of 128A-192A.The real-time temperature of the wire is monitored by high-speed infrared,and the inclination angle is used to analyze the heating and combustion temperature rise of the wire.The influence of characteristics,phase stagnation time,and ignition time.The results show that the heating and combustion process of the wire can be divided into three stages:linear heating stage,secondary pyrolysis heating stage,and slow heating stage.The influence of the inclination angle on the stagnation time of the stage is mainly reflected in the slow heating and ignition stage.When the current is greater than 192A,the inclination angle has a small influence on the stagnation time of each stage of the wire.When the inclination angle is in the range of 0°～75°,the ignition time of the wire decreases as the inclination angle increases,while at 90°,the ignition time of the wire is the longest.When the current value is greater than 192A,the ignition time gradually stabilizes and is affected by the inclination.The impact is small.Through COMSOL,the heating model of PVC copper wire with equal proportion of overload was established to study the distribution of temperature field and surrounding flow field of overloaded wire.The results show that:under the condition of different current values,there is a temperature gradient in the process of heat conduction,and with the increase of wire length,the maximum temperature first decreases,then generally stabilizes,and then increases.The results show that the velocity of air region first increases,then decreases,and then increases slowly;At the end time of the first stage,with the increase of wire length,the velocity of flow field around the wire presents a "U" shape changeing trend.In the range of wire length from 0 to 280 mm,the air velocity decreases,and in the range of 280 to 540 mm,the air velocity increases.Finally,Polyvinyl chloride copper wire was selected as the research object,with different current values and different inclination angles as the influencing factors,the overloaded flame spread characteristic experiment was carried out,and the overload combustion process of the wire,the flame spread rate,the flame shape,and the position of the wire on fire were clarified.law.Experiments show that under the same current conditions,with the increase of the inclination angle,the width of the flame base first increases and then decreases,and the upward flame spread rate and the flame downward flame spread rate increase;the wire with the same inclination angle increases with the current As the current increases,the flame shape becomes more "low and narrow",the flame height also decreases,and the flame spread rate is decreasing;with the increase of the current,the probability of the middle of the wire fusing and catching fire is increasing,when the inclination angle is 0°～45°,When the probability of fire in the middle of the wire is continuously increased,and when it is 45°～90°,it shows a decreasing trend.The above research results have certain guiding significance for electrical fire safety research. |
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