Research On The Structure Design And Release Performance Of The Hanging Crown Type Forest Fire Extinguishing Aerial Bomb

Canopy fire is the most harmful among forest fires,and it is also the most difficult to extinguish.The forest fire extinguishing aerial bomb is a brand new remote fire fighting equipment developed for the forest canopy fire problem.Most of the existing aerial bombs use temperature control to detonate,but their response time is long and the temperature of the fire field is complex and changeable,causing the aerial bomb to detonate in the non-canopy layer.This will affect the fire extinguishing effectiveness of aerial bombs.Therefore,this paper designs a forest fire-fighting aerial bomb with the characteristics of hanging crown and temperature composite detonation;and optimizes the structure of its central blast tube to improve its extinguishing agent utilization rate;at the same time,the stability of the launching device and the safety of the launching separation of the aerial bomb are optimized.As well as the density of aerial bomb landing points,a launch strategy was proposed to ensure safe and accurate delivery of aerial bombs,and to further improve the fire-fighting effectiveness.This article mainly completes the following contents:(1)Designed a forest fire extinguishing aerial bomb with the characteristics of hanging crown and temperature composite detonation,and completed the structural optimization of its gradient center burst tube.The overall structure of the aerial bomb was designed;the extinguishing agent dispersion process was analyzed based on the explosion dispersion theory,and the extinguishing agent dispersion finite element analysis model was established through HyperMesh and LSDYNA software.The extinguishing agent dispersion cloud map and the dispersion radius were used as indicators to explore the shell The influence law of body material,detonation method,specific charge,length-diameter ratio and gradient structure on the dispersion effect of fire extinguishing agent.The optimal parameters f the gradient burst tube and the warhead structure of the aerial bomb were optimized,and the fire extinguishing area was increased by 92.3%compared with the unoptimized before.(2)The flow field characteristics of the helicopter suspended flight are studied,and the quality and size of the launching device are determined.Based on the momentum source method,a simulation model of the flow field of the helicopter rotor/fuselage/dropping device was established.Using the vortex distribution of the flow field and the aerodynamic force of the launching device as indicators,the Fluent software was used to explore the different forward flight speeds,launching device attitudes and windward area pairs.According to the law of influence on the stability of the device,the mass of the feeding device is 2052kg and the size is 1.86m× 1.86m×1.86m.(3)The separation characteristics of aerial bomb launch were studied,and the safety of helicopter bomb launch was analyzed.Ansys software was used to simulate and analyze the feasibility of the aerial bomb leaving the launching device.A simulation model of the separated flow field of the aerial projectile was established,and the Fluent software was used to investigate the traj ectory of the aerial projectile,the displacement of the center of mass and the attitude change laws of the aerial projectile under different incoming flow velocity,initial velocity,altitude and attitude angle of the launching device after it was separated from the launching device.,The analysis determined that it is safe for the helicopter to drop bombs in stable flight.(4)The influence of different initial conditions on the density of the aerial bombs’ drop points was studied,and the launch strategy of the aerial bombs was determined.Based on the theory of exterior ballistics,a six-degree-of-freedom dynamics equation and a Simulink simulation model of the impact point dynamics of the aerial bomb were established.The influence of forward flight speed,initial velocity and launch height on the concentration of ballistic impact points was compared and the corresponding height was calculated.Based on the average coordinates,intermediate error and circular probability error of the bomb landing point at the incoming flow velocity,the bomb delivery strategy is proposed to ensure the safe and accurate delivery of the bomb while improving its fire-fighting effectiveness.