Ionization in gaseous detonation waves

Schulz, Joseph; Gottiparthi, Kalyana C.; Menon, Suresh

doi:10.1007/s00193-012-0412-9

Cited by 23 publications

(8 citation statements)

References 26 publications

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“…The air plasma mechanism used in the first portion of the simulation [23][24][25][26] uses thermodynamic coefficients from NASA CEA [27]. To characterize the state of the initial plasma, the internal energy of the volume of air contained within the igniter cavity (Oð0:1 cm 3 Þ) at the desired temperature and pressure (T ¼ T i , p ¼ 1 atm; v N2 ¼ 0:79; and v O2 ¼ 0:21) was raised by deposition energy of the igniter (1.25 J) and allowed to expand to p ¼ 1 atm and equilibrate.…”

Section: Approachmentioning

confidence: 99%

Liquid Fuel Composition Effects on Forced, Nonpremixed Ignition

Sforzo

Dao

Wei

et al. 2016

Journal of Engineering for Gas Turbines and Power

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The effects of jet fuel composition on ignition probability have been studied in a flowfield that is relevant to turbine engine combustors, but also fundamental and conducive to modeling. In the experiments, a spark kernel is ejected from a wall and propagates transversely into a crossflow. The kernel first encounters an air-only stream before transiting into a second, flammable (premixed) stream. The two streams have matched velocities, as verified by hot-wire measurements. The liquid fuels span a range of physical and chemical kinetic properties. To focus on their chemical differences, the fuels are prevaporized in a carrier air flow before being injected into the experimental facility. Ignition probabilities at atmospheric pressure and elevated crossflow temperature were determined from optical measurements of a large number of spark events, and high-speed imaging was used to characterize the kernel evolution. Eight fuel blends were tested experimentally; all exhibited increasing ignition probability as equivalence ratio increased, at least up to the maximum value studied (∼0.8). Statistically significant differences between fuels were measured that have some correlation with fuel properties. To elucidate these trends, the forced ignition process was also studied with a reduced-order numerical model of an entraining kernel. The simulations suggest ignition is successful if sufficient heat release occurs before entrainment of colder crossflow fluid quenches the exothermic oxidation reactions. As the kernel is initialized in air, it remains extremely lean during the initial entrainment of the fuel–air mixture; thus, richer crossflows lead to quicker and higher exothermicity.

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Section: Approachmentioning

confidence: 99%

Liquid Fuel Composition Effects on Forced, Nonpremixed Ignition

Sforzo

Dao

Wei

et al. 2016

Journal of Engineering for Gas Turbines and Power

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“…Here, we define a material shell as a spherical shell (of finite thickness) of particles or dense gases surrounding a spherical charge. Past studies in dilute mixtures [14,15] have shown that the interface between the particles and the gases forms "bubble" and "spike" structures after interaction with the shock wave, similar to the structures observed in a pure gas-phase Richtmyer-Meshkov instability (RMI) [16]. We further investigate the role of these structures to disperse the relatively dense loading of particles in the flow behind the blast wave.…”

Section: Introductionmentioning

confidence: 64%

“…The 2D domain is discretized using a uniform 1000×1000 mesh. The grid resolutions used here are chosen based on past studies of shock-particle interaction [5,15] and particle dispersion in post-detonation flows [25].…”

Section: Materials Shell Dispersionmentioning

confidence: 99%

“…1) and compresses the material in the shell as it propagates through the shell. These structures are formed due to the vorticity deposition by the Baroclinic torque effect [14,15]. As the inner interface evolves, structures are also generated at the outer interface as the shock crosses the shell and propagates into the ambient gases.…”

Section: Shock-materials Shell Interactionmentioning

confidence: 99%

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Turbulent mixing and afterburn in post-detonation flow with dense particle clouds

Gottiparthi¹,

Menon²

2017

AIP Conference Proceedings

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Abstract. Augmentation of the impact of an explosive is routinely achieved by packing metal particles in the explosive charge. When detonated, the particles in the charge are ejected and dispersed. The ejecta influences the post-detonation combustion processes that bolster the blast wave and determines the total impact of the explosive. While the classical Eulerian-Lagrangian (EL) methods can accurately handle the post-detonation mixing zone in the dilute regime, the Eulerian-Eulerian (EE) method is preferred for the initial dense clustering. Here, we summarize the results obtained using both EL and EE methods as well as demonstrate a new hybrid EE-EL approach. The EL method, which is also developed to handle both dense and dilute flows using the discrete equation method, is used initially to study the dispersion of a relatively dense particle shell by blast waves. The results show distinct clustering of particles that later leads to the formation of jet-like structures as seen in experiments. Then, the hybrid EE-EL method is used to study the dispersion of dense clouds from explosives packed with aluminum (reactive) or steel (inert) particles. A transitioning criterion is used to smoothly transfer the initially dense Eulerian mass to Lagrangian particles when dilute. Results are presented to demonstrate that the approach is computationally efficient and accurate for certain ranges of particle sizes and loading. It is shown that mixing between the ambient and post-detonation products can be enhanced when particles are present in the flow. Furthermore, the afterburn of aluminum particles increases in the average gas-phase temperature by 100 K -200 K when compared to a case with non-reacting particles. More studies are still needed to establish a robust strategy for wider applications.

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“…The transport properties for each species are computed using curve-fits as a function of the gas temperature. 40,41 The interphase coupling terms,Ḟ p,i ,Ẇ p , andQ p , in the conservation equations are the rates of momentum, work, and heat transfers resulting from the presence of particles in the two-phase mixture. These terms are discussed further in Sec.…”

Section: A Gas Phasementioning

confidence: 99%

Richtmyer-Meshkov instability in dilute gas-particle mixtures with re-shock

2013

Self Cite

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The Richtmyer-Meshkov instability (RMI) is investigated in a dilute gas-particle mixture using three-dimensional numerical simulations. This work extends an earlier two-dimensional study [S. Ukai, K. Balakrishnan, and S. Menon, “On Richtmyer-Meshkov instability in dilute gas-particle mixtures,” Phys. Fluids 22, 104103 (2010)] to a larger parameter space consisting of variations in the mass loading and the particle size as well as considering both single-mode and multi-mode interface initializations. In addition, the effect of the presence of particles on re-shock RMI is also investigated. Single-phase numerical predictions of the mixing layer growth-rate are shown to compare well to both experimental and theoretical results. In a dilute gas-particle mixture, the initial growth-rate of RMI shows similar trends compared to previous work; however, the current numerical predictions show that there is an observable increase, not previously predicted, in the growth of the mixing layer at higher mass loadings. For the range of cases considered, an increase as much as 56% is observed. This increase is attributed to additional vorticity production in the mixing layer resulting from inter-phase momentum coupling. Moreover, the presence of particles introduces a continuous drag on the gas-phase resulting in a delay in the time at which re-shock occurs. This delay, which is observed to be as much as 6%, is largest for higher initial mass loadings and smaller particle radii and has a corresponding effect on both the growth-rate of the mixing-layer after re-shock and the final width of the mixing layer. A new semi-analytical correlation is developed and verified against the numerical data to predict the re-shocked RMI growth-rate in dilute gas-particle flows. The correlation shows that the re-shock RMI growth-rate is linearly proportional to the velocity jump at re-shock, the molecular mixing fraction, and the multi-phase Atwood number. Depending on the initial mass loading and particle radii, the re-shock RMI growth-rates were observed to be reduced by as much as 48% in some cases with variations of around 26% in the width of the mixing layer after re-shock.

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Ionization in gaseous detonation waves

Cited by 23 publications

References 26 publications

Liquid Fuel Composition Effects on Forced, Nonpremixed Ignition

Liquid Fuel Composition Effects on Forced, Nonpremixed Ignition

Turbulent mixing and afterburn in post-detonation flow with dense particle clouds

Richtmyer-Meshkov instability in dilute gas-particle mixtures with re-shock

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