| Forest fires have seriously endangered China’s forest ecology and caused serious damage to the natural environment.At present,the rapid spread of forest fires cannot be effectively curbed,and early suppression of forest fires is an important means of responding to forest fires.As a unique fire extinguishing tool to extinguish early forest fires in China,portable Airflow extinguishers are widely used and kept in Forest steppe fire extinguishing teams in China.However,there are still problems such as decreased outlet Airflow speed,increased outlet temperature,low fire extinguishing efficiency,and easily re ignited fires due to overheating of the engine after a long time of operation.This article optimizes the fire extinguishing performance of Airflow extinguishers by adding collaborative fire extinguishing media(gravel): Based on the existing 6MF-30 Airflow extinguisher design,a Airflow sand fire extinguishing test platform is built.Through experimental research,theoretical analysis,simulation optimization,and experimental verification,the number of blades and sand injection parameters of the Airflow sand extinguisher are optimized,and the Airflow sand collaborative fire extinguishing effect and fire extinguishing law are explored and summarized,Provide innovative new ideas for the performance optimization of Airflow powered fire extinguishers,and have important practical significance for the research and development of fire extinguishing equipment.The main methods and conclusions of this thesis are as follows:(1)The aerodynamic performance parameters of the original Airflow fire extinguisher and the Airflow sand fire extinguisher are measured respectively,and the jet velocity distribution along the way under different rotational speeds is compared.The study found that the jet velocity of the Airflow sand fire extinguisher is slightly smaller than that of the Airflow fire extinguisher when carrying sand,but it does not affect the aerodynamic performance effect.The sand dispersal experiment on a Airflow sand fire extinguisher found that the sand presents a non-uniform distribution during the sand dispersal process,and there is a core area of sand accumulation on the ground.The core area has the highest quality of sand accumulation,presenting a concentrated state.According to the location of the core area,the sand and gravel spreading distance is determined to be 1.5-2.34 m.(2)The effectiveness of the Airflow sand fire extinguisher was verified.By comparing the time required for the original Airflow sand fire extinguisher and the Airflow sand fire extinguisher to extinguish wood pile fires,it was found that the fire extinguishing performance of the fan was significantly improved after adding fire extinguishing media,but the fire extinguishing distance was short and it was unable to extinguish wood pile fire sources at a distance of 2.5m.(3)Based on the experimental results,the mechanism of Airflow sand coordinated fire extinguishing was analyzed.In areas where sand and gravel cannot be accumulated,a large amount of high-speed air flow blown out by the Airflow tunnel is mainly used to reduce the surface temperature of the wooden pile and disperse combustible gas to extinguish the fire,which takes a long time to extinguish;In areas where there is a suitable Airflow speed and sand can be accumulated,fire extinguishing mainly relies on Airflow sand coordination,where the Airflow serves as a power source to provide power for the sand.A suitable Airflow speed can fully disperse the combustion gas and reduce the temperature of the wood pile,while sand can cover and accumulate the wood pile,greatly reducing the fire extinguishing time;In areas where the Airflow speed has sharply decreased to less than 15 m/s,but sand and gravel can still be accumulated,fire extinguishing mainly relies on sand and gravel accumulation.(4)Through the coupling of FLUENT and EDEM,the sand injection parameters(sand discharge port shape,air duct length,sand discharge diameter)and the number of blades of the Airflow sand fire extinguisher were optimized,and the optimal parameters of the Airflow sand fire extinguisher were determined.According to the numerical simulation method,when the sand discharge port shape was set as a flat port,the air duct length was 79 cm,the sand discharge diameter was 8 cm,and the number of blades was 20,the sand discharge distance increased by 10.76-23.38% compared to the original installation,The effective fire extinguishing distance(at locations with Airflow speed>22m/s)has increased by 14.67% compared to the original installation.Field experiments were conducted to verify the optimized Airflow sand fire extinguisher,which confirmed that the optimized Airflow function significantly improved fire extinguishing efficiency and increased fire extinguishing range,and the use of Airflow sand synergy can reduce the risk of combustion support and reburning,providing important reference significance for the development of early forest fire extinguishing tools.The thesis includes 56 diagrams,10 tables,and 74 references... |
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