Determination of the Speed of Flame Front Propagation during Emergency Deflagration Explosions


Annotation:

In the territory of the facilities where combustible gases are handled or stored, the combustible gas-air mixture may be formed as a result of the equipment depressurization. Mixture ignition leads to fires, explosions and destruction of buildings and structures. Most often, the combustion of such mixtures occurs in the deflagration mode. Main factor affecting the values of explosion parameters is the speed of flame front propagation.

The methodologies presented in the normative documents and in various sources of literature are considered, which are related to the determination of the speed of flame front propagation. The analysis showed that for the same emergency the considered methodology gives significantly different values of the speed of flame front propagation, this causes discussion among the design engineers. The considered methodology is developed based on the experimental data. Thus, the definition of the speed of flame front propagation in the methodology presented in the normative documents is based on the mixture of energy potential. Proprietary methodology considers the physical and chemical properties of gas-air mixtures, but there is no mentioning about the boundaries of their application.

The methodology proposed in the article is related to determining the speed of flame front propagation. It is developed based on the theories of hydrodynamics and flame propagation. It is assumed that flame propagation in a gas mixture is similar to a fluid flow in the smooth round pipes. The movement of gas follows the laws of hydrodynamics,  the coefficient of thermal conductivity of the gas mixture is proportional to the coefficient of hydraulic friction, since the physical meaning of the kinematic viscosity coefficient, the diffusion coefficient, and the thermal conductivity coefficient of gases is the same. Among others, they have the same dimension.

Verification of the developed methodology for predicting the speed of flame front propagation during gas-air mixture combustion was carried out based on the comparative analysis of the calculation results with the consequences of real emergency explosions. The analysis of the considered accidents led to the conclusion that the proposed methodology realistically describes the process of flame front propagation during gas-air cloud explosion.

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DOI: 10.24000/0409-2961-2020-7-7-13
Year: 2020
Issue num: July
Keywords : gas-air mixtures emergency explosions gas cloud explosion vapor-air mixtures deflagration explosion turbulent combustion calculation of the speed of the flame front propagation
Authors:
  • Komarov A.A.
    Dr. Sci. (Eng.), Prof., Head of the Explosion Safety Research Center NRU MGSU, Moscow, Russia
  • Grokhotov M.A.
    Cand. Sci. (Eng.), Assoc. Prof. Academy of GPS of the Ministry of Emergency Situations of Russia, Moscow, Russia