Analysis of C2HF5 concentration and calculation of characteristic mixing time behind obstacle

• Published in: Aerospace science and technology Vol. 146; p. 108949
• Main Authors: Zhou, Qiyong, Lu, Song, Shi, Hui, Ma, Weitong, Zhang, Heping, Gu, Junming
• Format: Journal Article
• Language: English
• Published: Elsevier Masson SAS 01.03.2024
• Subjects: C2HF5; Characteristic mixing time; Extinguishing agent concentration; Obstacle; Obstacle; Extinguishing agent concentration; Characteristic mixing time; C2HF5
• ISSN: 1270-9638; 1626-3219
• DOI: 10.1016/j.ast.2024.108949

C2HF5 is not only a refrigerant but also a highly efficient fire extinguishing agent. The effect of obstacle on the concentration distribution of extinguishing agent is important in the design for a firefighting strategy. Based on the extinguishing agent concentration analyzer using the differential pressure principle, the fire extinguishing agent concentration under the influence of different wind speeds, blockage ratios, and obstacle types is measured. The fire extinguishing agent is brought into the recirculation zone by the mutual entrainment of the primary eddy and the secondary eddy. The concentration of fire extinguishing agent decreases with the increase of wind speed. The increase of blocking ratio makes the concentration of extinguishing agent decrease in the recirculation zone. In the recirculation zone, when the blockage ratio is small, the concentration of fire extinguishing agent in the baffle and the 45° backward facing step at different wind speeds is approximately equal. With the increase of blockage ratio, the concentration of fire extinguishing agent in the baffle is greater than 45° backward facing step in the recirculation zone. Through experimental analysis, the feasibility of discrete calculation of characteristic mixing time is proved. The characteristic mixing time of different obstacles is not equal under cold spraying condition. The calculation formula of characteristic mixing time of the baffle and 45° backward facing step is obtained by fitting analysis, the characteristic mixing time coefficients are 34.4 for the baffle and 30.7 for the 45° backward facing step.