Pulsating detonative combustion in n-heptane/air mixtures under off-stoichiometric conditions

Zhao, Majie; Ren, Zhuyin; Zhang, Huangwei

doi:10.1016/j.combustflame.2020.12.012

Cited by 36 publications

(14 citation statements)

References 54 publications

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“…17b), the EI's of the radical species and temperature alternate behind the SF. This is also observed in the chemical propensity within the induction zone of the pulsating n-heptane detonations [72]. Specifically, at 𝑥 > 𝑥 𝑇𝑅1 = 254.08 mm and x < 𝑥 𝑇𝑅2 = 253.96 mm, thermal runaway occurs (temperature EI is largest).…”

Section: Chemical Explosion Mode In Gaseous Detonationmentioning

confidence: 71%

“…12) in the induction zone, further development of these AI spots into reaction front propagation towards the leading SF is not observed. This is different from the evolutions of the local explosions ahead of the travelling RF in one-dimensional n-heptane/air detonations, which induces periodic coupling of the SF and RF and hence pulsating detonations [72]. Beyond 160 μs, the AI spots are further extended along the spanwise direction before the RF, which may further weaken the RF propagation due to partial reaction of the mixture before the SF.…”

Section: Chemical Explosion Mode In Gaseous Detonationmentioning

confidence: 82%

“…In this section, CEMA [20,21] is used to quantify the critical gas phase chemical feature in detonations. It is inspired by the Computational Singular Perturbation (CSP) method developed by Lam et al [68][69][70][71] and has been proven a reliable tool to identify the critical combustion phenomena [20,21,72]. The differential equations for a spatially homogeneous reaction system read…”

Section: Chemical Explosion Mode In Gaseous Detonationmentioning

confidence: 99%

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Extinction of incident hydrogen/air detonation in fine water sprays

Zhao

Zhang

2021

Physics of Fluids

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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.

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Section: Chemical Explosion Mode In Gaseous Detonationmentioning

confidence: 71%

Section: Chemical Explosion Mode In Gaseous Detonationmentioning

confidence: 82%

Section: Chemical Explosion Mode In Gaseous Detonationmentioning

confidence: 99%

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Extinction of incident hydrogen/air detonation in fine water sprays

Zhao

Zhang

2021

Physics of Fluids

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“…Only a smaller subset of positive Ω R+T regions are considered truly explosive. Hence, the diagostics solely based on Λ e, f may lead to an erroneous interpretation of the explosion characteristics, thereby rendering the drawn conclusions, in the best case, questionable [115][116][117][118][119][120][121][122]. This is in agreement with earlier work in turbulent and MILD combustion that reached the same conclusion and highlighted that Λ e, f can compete with dissipative modes which become more active (i.e., faster in terms of their timescales and stronger in terms of their amplitudes), hence the a priori use of solely Λ e, f for the characterisation of the system's dynamics is inappropriate [109,110,123,124].…”

Section: Computational Singular Perturbation (Csp) Analysismentioning

confidence: 99%

Asymptotic Analysis of Detonation Development at SI Engine Conditions Using Computational Singular Perturbation

Dimitrova¹,

Sanal²,

Luong³

et al. 2022

Preprint

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The occurrence and intensity of the detonation phenomenon at spark-ignition (SI) engine conditions is investigated, with the objective to successfully predict super-knock and to elucidate the effect of kinetics and transport at the ignition front. The computational singular perturbation (CSP) framework is employed in order to investigate the chemical and transport mechanisms of deflagration and detonation cases in the context of 2D high-fidelity numerical simulations. The analysis revealed that the detonation development is characterized by: (i) stronger explosive dynamics and (ii) enhanced role of convection. The role of chemistry was also found to be pivotal to the detonation development which explained the stronger explosive character of the system, the latter being an indication of the system's reactivity. The role of convection was found to be enhanced at the edge of the detonating front, thereby suggesting that it is the result and not the cause of the detonation onset. Moreover, the increased contribution of convection was found to be related mainly to heat convection. Remarkably, the detonation front was mainly characterized by dissipative and not explosive dynamics. Finally, diffusion was found to have negligible role to both examined cases.

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“…Romick et al [36] proposed that the viscous effects have a dramatic effect on the long time behaviour of the detonation. However, to the best of our knowledge, most previous studies with NS solvers have focused on the 1D/2D detonations [35,37,38,39,40]. The role of viscosity in 3D detonations has not been systematically investigated, due to significantly increased computational cost compared with that for inviscid simulaions.…”

Section: Introductionmentioning

confidence: 99%