Extinction of incident hydrogen/air detonation in fine water sprays

Abstract

Two-dimensional numerical simulations with Eulerian-Lagrangian method are conducted to study propagation and extinction of stoichiometric hydrogen/air detonations in fine water sprays. Parameterized by water mass loading and initial droplet size, a detonation extinction map is developed. Detonation extinction would occur with larger mass loading and/or smaller droplet size. General features of gas phase and water droplets and local detonation frontal structures are well captured. Numerical soot foils are used to characterize the influence of mass loading and droplet size on the detonation wave. The results also show that the detonation cell size increases with increased mass loading or decreased droplet size. Analysis on unsteady detonation extinction process is performed with the evolutions of detonation frontal structure, spatial distribution of thermochemical variables and interphase transfer rates (mass, energy, and momentum). Moreover, the chemical explosive mode analysis reveals that for stable detonation, thermal runaway dominates behind the Mach stem, while chemical propensities of auto-ignition and thermal runaway appear alternately behind the incident wave. When the induction zone length increases as the reaction front (RF) and shock front (SF) are decoupled, localized burned pockets surrounded by the autoignition chemical explosive mode can be observed. In addition, the interactions between detonation wave and water droplets demonstrate that the energy and momentum transfer have more direct interaction with SF and RF than the mass transfer. The interphase transfer rates increase with the water mass loading. Under the same mass loading, the smaller the droplet size, the larger the interphase transfer rates. However, the size of fine water droplets has a limited influence on the interphase momentum exchange. Moreover, high energy and mass transfer rates are observed at the onset of detonation extinction, and they gradually decrease when the reaction and detonation fronts are decoupled.

Linear Theory of Hypersonic Shocks Interacting with Turbulence in Air

“…When moving through fuel-air sprays with large droplets, detonations exhibit a deficit in the propagation velocity compared to the gas-phase velocity [218]. Similar effects have been observed in detonations moving through reactive gaseous media with water clouds [219][220][221][222]. However, a clear correlation between the upstream properties of the heterogeneous mixture and the detonation propagation velocity has not been presented to date.…”

Direct detonation initiation in hydrogen/air mixture: effects of compositional gradient and hotspot condition

“…Furthermore, the corresponding evolutions of λ CEM , a chemically explosive mode (Lu et al 2010;Goussis et al 2021), along the monitoring line are shown in figure 14(a). Note that the chemical explosive mode (CEM) is a chemical property of local gaseous mixture and characterizes the chemical explosion propensity of the shocked gas, and hence has been extensively employed in transient detonation problems (Xu et al 2021;Guo et al 2022;Jin et al 2023). The value of λ CEM corresponds to the reciprocal time scale of the chemical explosion.…”

“…Note that the chemical explosive mode (CEM) is a chemical property of local gaseous mixture and characterizes the chemical explosion propensity of the shocked gas, and hence has been extensively employed in transient detonation problems (Xu et al. 2021; Guo et al. 2022; Jin et al.…”

“…The accuracies of RYrhoCentralFoam in detonation simulations have been extensively validated (Huang et al. 2021), and it has been used for various detonation problems (Huang & Zhang 2020; Huang, Cleary & Zhang 2020; Xu, Zhao & Zhang 2021). The details on code validation for cylindrical detonation are given in the supplementary material available at .…”

Effects of Dilution and Pressure on Detonation Propagation Across an Inert Layer

“…S a zero-carbon-emission fuel, hydrogen has recently drawn significant attention due to its promising applications in energy storage and energy conversion [1]. Great effort has been devoted to investigating the properties of hydrogen flames and detonations (e.g., [2][3][4][5][6][7][8]). However, there is still severe safety concern for hydrogen storage and utilization since hydrogen is easily to be ignited [9][10][11].…”