Study On Dynamic Response And Pressure Relief Characteristics Of Explosion-proof Door In Vertical Shaft And Fan Blades Under The Action Of Gas Explosion Shock Waves

As the main energy source in China,coal has made an important contribution to the rapid development of the national economy.Gas explosion accidents occur from time to time,which seriously threaten the mine safety production.The main ventilation fan is the "lungs" of the mine.The continuous,safe and reliable operation of the mine’s main ventilator in the event of a gas disaster is of great importance to rescue and relief and to ensure the safety of all underground mine personnel.In response to the failure of the vertical shaft explosion-proof door and the destruction of the main ventilation fan in the mine during the disaster,this paper conducts a study on the dynamic response and pressure relief characteristics of explosion-proof door in vertical shaft and fan blades under the action of gas explosion shock waves.In this paper,a small-scale gas explosion experimental platform is built,experimental and numerical simulation studies of gas explosion propagation are conducted,and the mathematical model used for the numerical study of gas explosion propagation law is determined by comparing the results of small-scale and prototype mine scale numerical simulations with the experimental results.Taking No.2return wind shaft of Yangchangwan coal mine as the research object,the method of segmental succession simulation is proposed to realize the numerical calculation of the gas explosion shock wave propagation process of the return wind network from the digging face to the return wind shaft,and the propagation law of the gas explosion wave along the return wind network is obtained.Numerical simulation was conducted to study the evolution process of impact loads on fan blades and explosion-proof doors under different explosion equivalent operating conditions under the closed conditions of explosion-proof doors.The evolution law of explosion impact loads on fan blades and explosion-proof doors under the closed conditions of explosion-proof doors are obtained,and the opening conditions of explosion-proof doors is also obtained;By studying the passive opening process of explosion-proof doors with different opening structure forms,the optimal opening structure form of explosion-proof doors is determined,Taking this opening structure as the research object,the influence of gas explosion intensity and counterweight quality on the opening process of explosion-proof doors was studied.The evolution law of impact load on explosion-proof doors and fan blades under the passive opening mode and the pressure relief effect after opening are obtained,revealing the relationship between gas explosion strength,counterweight,and pressure relief effect.By studying the effects of blast intensity and the active early opening height of the blast door on the active opening process,the evolution of the shock load on the turbine blades and the pressure relief effect of the explosion-proof door after opening are obtained for the active opening method.Based on the summary of the research results,a new type of explosion-proof door is designed and applied to the production mine to improve the disaster resistance of the main ventilation fan.The main research results obtained in this paper are as follows:(1)By comparing the experimental results of the constructed experimental system for gas explosion propagation and the experimental results in the prototype scale tunnel of the mine in the literature,the large eddy simulation(LES)turbulence model and the eddy dissipation(EDM)combustion model were identified as the mathematical models to describe the numerical simulation of gas explosion propagation.The relative errors of the numerical simulation results with the experimental results of the constructed experimental system and the experimental results in the prototype scale tunnel of the mine were 3.60%-7.18%,and2.40%-10.77% errors,respectively.(2)The simplification method of branch tunnel propagation of gas explosion shock wave along the return wind network is determined,the segmented succession simulation method is proposed,and the geometric model for numerical simulation of gas explosion shock wave propagation along the return wind network is determined.When the branch lane retention length is greater than 8 times the equivalent diameter of the lane,the branch lane retention length has basically no effect on the numerical simulation results of the blast shock wave parameters on the main return air route.The return air network from the digging face to the blast door of the return air shaft is divided into three sections for numerical simulation,and the three sections are: 80 m from the head of the digging face(the first section),20 m from the main return air alley to 50 m from the blast door of the return air shaft(the second section),and 50 m below the blast door of the return air shaft(the third section).The distribution of blast shock wave parameters at the intersection of the zones and their variation with time are used as the inlet boundary conditions for the next zone.(3)The numerical simulation studied the gas explosion shock wave propagation process in the return wind network,and obtained the attenuation law of gas explosion shock wave propagation in the dug-in working face,return wind alley and return wind shaft.Excavation work face roadway explosion shock wave decay along the decay trend in line with the power function form;back to the wind alley and back to the wind shaft in various points of overpressure with the explosion equivalent into a power function form of the relationship,the greater the gas equivalent of the gas explosion,the faster the gas explosion shock wave propagation speed,the faster the decay speed of overpressure;with the propagation distance increases the decay speed of overpressure more and more slowly.(4)The propagation process of gas explosion shock waves in the wellbore-blast door-air cave-fan structure with different explosion equivalents under closed blast door conditions is studied,and the distribution and dynamic evolution of impact loads on the blast door and fan blades under closed blast door conditions are obtained.The impact loads on the wind turbine blades showed a wavy distribution along the radial direction,and the high overpressure zone on the blast doors expanded from the far wind refuge side to the near wind refuge side,and the distribution of the impact loads on the blast doors tended to be uniform as time increased.With the increase of gas explosion equivalent acting on the fan blade root bending moment peak,explosion-proof door on the peak overpressure are increased but the magnitude of the increase is getting smaller.Acting on the fan blade shock wave overpressure peak and explosion-proof door overpressure peak time difference is very small,when the gas explosion equivalent small,fan blade shock load peak arrival time slightly earlier than the explosion-proof door shock load peak arrival time,when the gas explosion equivalent larger,fan blade shock load peak arrival time slightly later than the explosion-proof door shock load peak arrival time.The fan blade root bending damage conditions is derived,and the opening pressure of the explosion-proof door is determined when the blade root bending moment reached the allowable bending moment under different safety factors.(5)The study determined the optimal opening structure of the blast door and obtained the load and pressure relief effect on the explosion-proof door and ventilator blades under different counterweight conditions during the passive opening of the up and down moving blast door.Numerical simulations of the opening process of the three opening configurations:up and down moving,internal rotating and external rotating,showed that the impact load on the up and down moving door is minimal,the pressure relief is fast,and the opening structure is simple,so the up and down moving door is the optimal opening structure.During the passive opening of the up-and-down moving door,the counterweight mass has little effect on the opening height and lifting speed of the door,the impact load on the door and the fan blades,and the pressure relief effect;as the gas explosion equivalent increases,the pressure relief effect of the fan blades decreases during the opening of the door.(6)A new idea of active advance opening of explosion-proof doors was proposed,revealing the law of change of impact load and pressure relief effect of ventilator blades under the conditions of active advance opening of explosion-proof doors,and determining the location of early warning sensors and early warning pressure in explosion-proof doors.The pressure relief effect is better than the passive opening of the explosion-proof door active early opening,with the explosion-proof door active early opening height increase pressure relief effect increases,but the increase is smaller and smaller,open the height of 1.5m pressure relief effect reaches the maximum(explosion-proof door fully open state)pressure relief effect of more than 90%;with the increase of gas explosion intensity,the fan blade pressure relief effect is getting worse.A theoretical calculation model for the location of the early warning sensors was constructed;the early warning pressure at the blast door opening at the location of the sensors was determined under different safety factors.(7)The structure and main parameters of the new explosion-proof door were designed by combining the obtained research results on the optimal opening structure of the explosion-proof door,the relationship between the counterweight and the opening pressure relief effect of the explosion-proof door.It was applied in the production mines,and the designed explosion-proof door operates smoothly and could be applied in mines with significant explosion hazard.There are 87 pairs of figures,29 tables and 134 references in this thesis.