Research And Numerical Analysis Of Flour Explosion Characteristics In 20L Closed Container

Flour is one of the essential food sources for human life.In recent years,many flour explosion accidents have occurred in China,bringing a large number of casualties and huge economic losses.In order to prevent flour explosions and effectively reduce the severity of the explosion consequences,studying the explosive characteristics of flour and clarifying the key factors that cause the violent dust explosion is of great help to preventing flour explosion accidents.In this paper,the pyrolysis process of flour was studied by using thermogravimetric analyzer and laser particle size distribution instrument,and the degree of particle fragmentation occurred during the dispersion process of flour particles was determined.Meanwhile,using 20 L spherical explosion tester,the variation law of flour explosion characteristic parameters under different dust concentration,different ignition delay time and different ignition energy were tested.Finally,using numerical simulation software,the flow pattern of high-pressure gas within the 20 L spherical explosion tester was also explored to clarify its effect on the delay time after flour ignition.The result shows that the flour thermogravimetric process is in accordance with the law of biomass dust pyrolysis,which can be divided into three main stages: the ignition stage,the intense combustion stage and the slow combustion stage.In the process of flour dispersion,some flour particles will undergo particle fragmentation,resulting in a dust particle size smaller than the pre-test particle size during the test.Dust concentration has a certain impact on the flour explosion test results as the concentration of flour increases.the maximum pressure of the flour explosion and the maximum explosion index shows a trend of change after rising.With the extension of the ignition delay,the maximum explosion pressure and maximum explosion index of the flour explosion show a trend of increasing and then decreasing.As the ignition energy increases and the ignition energy increases,the maximum net explosive pressure of the flour explosion and the maximum explosion index will gradually increase.Through the orthogonal test method of extreme difference analysis and variance analysis,the ignition delay time has a significant effect on the maximum explosion pressure,and the dust mass concentration has a significant effect on the maximum explosion index.Through numerical simulation,the airflow in the 20 L spherical explosion tester is not uniformly distributed inside,which will affect the distribution of dust inside the explosion chamber,resulting in the larger concentration.Therefore,combined with the experiment,it can be concluded that as the flour concentration increases,the optimal ignition delay time for the flour explosion test should be 80ms-100 ms.