Study On The Explosion And Venting Characteristics Of Dried Maize Starch At High Vent Opening Pressure

Dust explosions can bring enormous threat to the safe production of dust explosion enterprise.In order to reduce the damage caused by explosions,venting measures have always been one of the easiest and most effective ways.Therefore,based on the existing research on dust venting,research on the dust venting characteristics under the condition of high vent opening pressure can provide guidance for the explosion prevention and control work in the production process of explosives enterprises.In this paper,we uses the 20L spherical explosion and venting experimental system and professional dust explosion simulation software FLACS,study the dried maize starch explosion and venting process in spherical containers.Focusing on different dust concentrations and vent open pressure.Under different dust concentration and vent open pressure,the characteristic changes of pressure and flame propagation during the whole dust venting process were analyzed.The results show that the peak pressure of dried maize starch explosion increases first and then decreases with the increase of dust concentration,the maximum explosion pressure is 6.28bar at the optimum mass concentration of 600g/m3.After the venting measures are taken,the maximum explosion overpressure and maximum explosion temperature inside the vessel are significantly reduced.Along the venting direction,as the displacement from the venting port increases,the overpressure peak outside the vessel first increases and then decreases,and there is a displacement interval,so that the peak of venting overpressure is the largest within the range of the displacement interval.When the dust concentration is low(less than 400g/m3),as the concentration increases,the peak of overpressure inside the vessel gradually increases;when the dust concentration is high(greater than 900g/m3),the peak of overpressure increases tend to be stable;when the concentration range of dust is between 400g/m3 and 900g/m3,the peak of overpressure rises only slightly with the increase of concentration.The greater the vent open pressure of the venting device,the greater the peak of the overpressure inside the vessel.The temperature of the outer space of the vessel is lower than the internal temperature,and the high temperature can last for a short time.At the end of the vented flame,the peak of the flame temperature shows a rapid decline with the increase of the displacement from the venting port.The temperature inside the vessel increases rapidly with the increase of the dust concentration,and then slowly decreases,the peak temperature is the highest when the concentration is 600g/m3.As the vent open pressure increases,the peak of the inside combustion temperature of the vessel gradually increases.Along the venting direction,the peak velocity of the airflow at the vent port is the largest,The peak velocity of the airflow gradually increases as the open vent pressure increases,As the dust concentration increases,the peak velocity of the airflow increases first and then decreases,and the peak velocity of the airflow is maximized when the dust concentration is 500g/m3.The propagation of the vented flame can be divided into two phases:a first propagation phase in which the pressure and the flame are collectively vented,and a second propagation phase in which the venting flame is discharged after the pressure venting is completed.The second propagation phase of the flame takes longer than the first phase.Due to the interaction of the dust concentration and the vent open pressure,a secondary flame occurs during the second propagation phase.The appearance of the secondary flame will significantly lengthen the time of the entire flame venting process,shortening the length of the vented flame,and having a major impact on the entire dust venting process.The increase in dust concentration also tends to increase the time of the flame venting process.The flame propagation rate within the vessel is much lower than the rate at which the vented flame.When the flame is released from the venting port,its propagation rate increases rapidly and peaks in a short time.