Numerical Simulation Of Premixed Gas Explosion And Explosion Venting In Tube

Accidental gas explosion is one of main disasters in process industries and life.To prevent and control the explosion accidents of combustible gas,in the present study,the CFD code AutoReaGas was used to simulate the characteristics of premixed gas/air mixtures explosion and venting in tube.The explosion characteristics were revealed in the case of different hydrogen blend ratios,initial temperatures,initial pressure,obstacles and explosion venting conditions.The results and main contributions of the thesis are briefly described below:The effects of hydrogen blend ratios in gases on the peak overpressure and temperature were investigated.The maximum overpressure increases with increasing hydrogen blend ratios.When the hydrogen blend ratios in gases is 75%,the maximum explosion static overpressure is 27.03 bar,up to 4.85 times of the maximum value of 5.571 bar obtained with the hydrogen blend ratios of 25%.The maximum temperatures increases obviously with increasing hydrogen blend ratios.When the hydrogen blend ratios increase ranging from 25%to 75%,the peak temperatures increase from 3170 K to 4791 K,and the increment is up to1621 K.The influences of initial pressure and initial temperature on the explosion overpressure of premixed gas/air mixtures in tube were investigated.The peak explosion overpressure always increases in linear relationship along with increasing initial pressure.More,the influence of initial pressure on explosion overpressure gradually diminishes with the increasing of initial temperature.For different initial temperature values of 25oC and 50oC,the increments of peak overpressures obtained in tube are 59 kPa and 53 kPa with the increment of 1bar for initial pressure,respectively.With increasing initial temperature,the maximum overpressure gradually decreases,and the influences of initial temperature on explosion overpressure gradually increases with the increasing of initial pressure.The influences of obstacles number and blockage ratio on the explosion overpressure of premixed gas/air mixtures in tube with built-in obstacle were investigated.The maximum overpressure increases along with the increase of obstacles number.When the number of obstacles is 13,the maximum explosion static overpressure in tube is 882.0kPa,up to 46.2times of the maximum value of 19.1kPa obtained without obstacles.With the increase of blockage ratio,the explosion overpressure gradually rises.Nevertheless,the maximum overpressure does not always increase along with increasing blockage ratio,but subsequently begins to decrease as the blockage ratio increases to some extend.With the blockage ratio of75%,the maximum explosion static overpressure in tube is 489.5kPa,up to 25.6 times of the maximum value obtained without obstacles.The influences of venting membrane position and pressure on the explosion overpressure and temperature of premixed gas/air mixtures in tube were investigated.The venting membrane position has great effect on explosion overpressure and temperature.When the position of venting membrane is in the centre of the tube,the explosion overpressure and temperature is least.The effects of explosion venting is best.The venting membrane pressure has great effect on pressure wave propagation.The higher the venting membrane pressure is,the slower the decay of the overpressure is in the process of pressure wave propagation along the tube.The influences of venting membrane pressure on the maximum temperature in tube are slight.