The process of explosive mixture formation in the experimental chamber

Introduction. To prepare a high-quality gas-air mixture, fans are often used, which not only agitate the mixture, but also create flows with significant pulsation components. This leads to significant errors and poor repeatability of experiments.

Aim. The main purpose of this study was to determine the time required for high-quality mixing of combustible gas and air in the experimental chamber. The spatial uniformity of the gas concentration of the combustible mixture is crucial for the results of the experiments.

Research methods. The paper presents the results of calculations for programmes, the reliability of calculations of which is verified by the results of test calculations of problems with analytical solutions. The well-known diffusion equations were used as the initial equations describing the distribution of gas concentration over the space of the experimental chamber. The calculations used the coefficient of turbulent diffusion, the numerical value of which corresponds to the minimum value for enclosed spaces: D = 0.005 m2/s. The calculations were carried out according to an explicit difference scheme in the MatLab package.

Calculation results. The paper presents the results of calculations of the spatial distribution of the gas concentration in the experimental chamber for various time points. The minimum time required for the formation of a high-quality gas-air mixture in the chamber was obtained. The instantaneous photographs of the deflagration explosion shown in the paper show that a homogeneous mixture of good quality has been formed due to natural diffusion. The time intervals that were used to mix the combustible gas and air in the test chamber corresponded to the calculated values of the time required for high-quality preparation of the combustible mixture.

Conclusions. This paper shows that fans should not be used to prepare a high-quality gas-air mixture and that natural turbulent gas diffusion copes well with this problem. The minimum time intervals necessary for the formation of a high-quality gas-air mixture in a cubic chamber of arbitrary size were calculated.

1. Gromov N.V. Improving the technical system for ensuring the explosion resistance of buildings during explosions of gas-steam-air mixtures : dissertation for the degree of candidate of technical sciences. Moscow, MGSU, 2007; 134. (rus).

2. Schleg A.M. Determination of the parameters of easily removable structures : dissertation for the degree of candidate of technical sciences. Moscow, MGSU, 2002; 201. (rus).

3. Kazennov V.V. Dynamic processes of deflagration combustion in explosive buildings and rooms : dissertation for the degree of doctor of technical sciences. Moscow, MGSU, 1997; 445. (rus).

4. Azamov J.M. General principles for conducting experimental studies of internal deflagration explosions. Fire and emergencies: prevention, elimination. 2023; 4:79-86. DOI: 10.25257/FE.2023.4.79-86 (rus).

5. Shamsadin Saeid M.H., Khadem J., Emami S., Ghodrat M. Effect of diffusion time on the mechanism of deflagration to detonation transition in an inhomogeneous mixture of hydrogen-air. International Journal of Hydrogen Energy. 2022; 47(55):23411-23426. DOI: 10.1016/j.ijhydene.2022.05.116

6. Komarov A.A., Timokhin V.V. Experimental investigation and modeling of the formation of explosive concentrations. Occupational Safety in Industry. 2023; 1:84-88. DOI: 10.24000/0409-2961-2023-1-84-88 (rus).

7. Buzaev E.V., Zagumennikov R.A. An indirect method for determining the coefficient of turbulent diffusion in the formation of explosive clouds. Firefighting: problems, technologies, innovations : collection of materials of the III International Scientific and Practical Conference, at 2 p.m. Part 1. Moscow, Academy of GPS of the Mini­stry of Emergency Situations of Russia, 2014; 133-135. (rus).

8. Timokhin V.V. Pecilarities of the physical picture of the crash explosions development in isolated rooms. Fire and emergencies: prevention, elimination. 2022; 2:60-66. DOI: 10.25257/FE.2022.2.60-66 (rus).

9. Komarov A.A., Vasyukov G.V., Zagumennikov R.A., Buzaev E.V. Experimental study and numerical simulation of methane-air mixture formation process in premises. Pozharovzryvobezopasnost/Fire and Explosion Safety. 2015; 24(4):30-38. EDN TVFFRH. (rus).

10. Zagumennikov R.A. Parameters of formation of explosive methane-air mixtures in industrial premises : abstract of the dissertation for the degree of candidate of technical sciences. Moscow, Academy of the State Fire Service of the Ministry of Emergency Situations of Russia, 2016; 24. (rus).

11. Chengjun Yue, Li Chen, Zhan Li, Yuanchao Mao, Xiaohu Yao. Experimental study on gas explosions of methane-air mixtures in a full-scale residence building. Fuel. 2023; 353:129166. DOI: 10.1016/j.fuel.2023.129166

12. Buzaev E.V. Development of methods for predicting the parameters of explosive zones in case of accidental releases of combustible substances : dissertation for the degree of candidate of technical sciences. Moscow, MGSU, 2015; 124. (rus).

13. Komarov A., Korolchenko D., Gromov N., Korolchenko A., Jafari M., Gravit M. Specific Aspects of Modeling Gas Mixture Explosions in the Atmosphere. Fire. 2023; 6(5):201. DOI: 10.3390/fire6050201

14. Komarov A.A. Forecasting loads and estimating consequences of their impact on buildings and structures : dissertation for the degree of doctor of technical sciences. Moscow, MGSU, 2001; 460. (rus).

15. Komarov A.A., Korolchenko D.A., Gromov N.V. Experimental determination of glazing efficiency in case of in-door explosions caused by accidents. Pozharovzryvobezopasnost/Fire and Explosion Safety. 2022; 31(6):78-90. DOI: 10.22227/0869-7493.2022.31.06.78-90 (rus).

16. Zihao Xiu, Zhenyi Liu, Pengliang Li, Mingzhi Li, Jianbo Ma, Tao Fan et al. Research on the dynamics of flame propagation and overpressure evolution in full-scale residential gas deflagration. Case Studies in Thermal Engineering. 2024; 62(1):105204. DOI: 10.1016/j.csite.2024.105204

17. Polandov Yu.K., Korоlchenko D.A., Evich A.A. Conditions of occurrence of fire in the room with a gas explosion. Experimental data. Pozharovzryvobezopasnost/Fire and Explosion Safety. 2020; 29(1):9-21. DOI: 10.18322/PVB.2020.29.01.9-21. EDN CLTXYK. (rus).

18. Xu Ying, Yimiao Huang, Guowei Ma. A review on effects of different factors on gas explosions in underground structures. Underground Space. 2019; 5(4):298-314. DOI: 10.1016/j.undsp.2019.05.002

19. Cen K., Kang, Bin Song, Ruiqing Shen, Yidong Zhang, Wuge Yu, Qingsheng Wang. Dynamic Characteristics of Gas Explosion and Its Mitigation Measures inside Residential Buildings. Mathematical Problems in Engineering. 2019; 5:1-15. DOI: 10.1155/2019/2068958

20. Bao Q., Fang Q., Zhang Y., Chen L., Yang S., Li Z. Effects of gas concentration and venting pressure on overpressure transients during vented explosion of methane-air mixtures. Fuel. 2016; 175:40-48. DOI: 10.1016/j.fuel.2016.01.084

21. Korоlchenko D., Polandov Iu.K., Evich A. Dynamic effects at internal deflagration explosions. IOP Conference Series: Materials Science and Engineering. 2019; 603:052008. DOI: 10.1088/1757-899X/603/5/052008