Suppression effects of PA@SH-SiC porous materials on hydrogen-air deflagration

To achieve effective suppression of hydrogen-air deflagration, a new deflagration-suppressing material PA@SH-SiC is formed by grafting a phosphorus-containing compound, phytic acid (PA), onto the surface of porous silicon carbide (SiC) using a self-assembly technique. Scanning Electron Microscope (SEM) and Fourier Transform Infrared (FTIR) results show that PA is successfully and uniformly grafted onto the SiC substrate. In a semi-open duct with dimensions of 130∗130∗820 mm, the effects of two deflagration-suppressing materials, SiC and PA@SH-SiC, are being investigated under three pore sizes (30, 40, 50 PPI) and two thicknesses (20, 40 mm), in response to hydrogen-air deflagration at different equivalence ratios (0.3, 0.4, 0.5). Experimental results show that PA@SH-SiC exhibits superior performance in hydrogen-air deflagration compared to using porous SiC alone, reducing explosion overpressure and flame propagation velocity while minimizing flame distortion. PA coating enhances the chemical suppression effect of SiC by generating HOPO and other groups through endothermic decomposition, which absorb critical radicals like H, O, and OH, thereby weakening chain reactions. Under equivalence ratios of 0.3 and 0.4, porous SiC with 50 PPI effectively blocks most of the flame, reducing explosion overpressure and flame propagation velocity. However, 30 and 40 PPI porous SiC exacerbate deflagration. With a pore size smaller than hydrogen's MESG, 50 PPI porous SiC predominantly exhibits quenching effects, thus suppressing deflagration under equivalence ratios of 0.3 and 0.4. At 30 and 40 PPI, the pore size of porous SiC is too large, resulting in insufficient quenching capability. Instead, the disturbance caused by this leads to elongation and wrinkling of the flame, thereby intensifying the downstream gas deflagration. Taking the 0.4 equivalence ratio conditions as an example, increasing the thickness of 50 PPI porous SiC enhances deflagration suppression. Conversely, increasing the thickness of 30 PPI SiC from 20 mm to 40 mm increases Flame propagation velocity peak (V max ) by 6.3 m/s and overpressure peak (P max ) by 2.82 kPa. This is due to under the conditions of 30 and 40 PPI, increasing the thickness is equivalent to increasing the volume blocking ratio of obstacles, thereby exacerbating the deflagration effect. In addition, under different equivalence ratios, there are differences in the energy release and reaction rates of combustion, which directly affect the deflagration suppression performance of the porous materials.