Material combustion in oxidant flows: Self-similar solutions

Tyurenkova, V.V.; Смирнова, М.Н.

doi:10.1016/j.actaastro.2015.11.033

Cited by 85 publications

(8 citation statements)

References 19 publications

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“…In order to overcome gravity effects, the flow velocity would have to be so large that the radiant flux from the flame approximately balances surface re-radiation, and that there is not an external heat flux, and then the forcedflow flame spread is primarily determined by convective heat flux. Only in this case, it can be concluded [22] that an increase of mass transfer parameter brings to decrease of temperature gradient, and as a result, a decrease of heat flux. At very-low-flow speeds in microgravity, flame spread depends on the radiation flux downstream the leading edge, an important distinction compared to the case at high flow speed which normally depends only the forced flow velocity.…”

Section: Introductionmentioning

confidence: 84%

“…There is self-similar solution [22,23] to the problem of blowing in a reacting boundary layer without the consideration of radiative heat exchange. In order to overcome gravity effects, the flow velocity would have to be so large that the radiant flux from the flame approximately balances surface re-radiation, and that there is not an external heat flux, and then the forcedflow flame spread is primarily determined by convective heat flux.…”

Section: Introductionmentioning

confidence: 99%

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Impact of Fuel Type on Toxic Emissions from a Non-premixed Boundary Layer Laminar Flame in Microgravity – A Numerical Study

Wang

2022

Microgravity Sci. Technol.

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Examples from non-premixed boundary combustion representative of fire in microgravity environment are presented. A low forced flow of 0.25 m/s is present, which is typical of air circulation speeds in a spacecraft. The numerical simulations have been conducted to evaluate the modes of heat transfer with an emphasis on a discussion about the effects of various fuels on chemical emissions such as soot, CO, CO2 and unburnt hydrocarbons in reduced-gravity conditions. Typically, evaporation temperature is smaller for heptane than dodecane, and thus a lengthening of the heptane flame seems more pronounced as compared to that of dodecane flame with an increase in the visible flame zone by a factor of 2.3 times. A rapid regression rate of heptane due to the enhanced heat feedback contributes to an additional energy by a factor of 80% in heat release rate as compared to dodecane. In all the cases, only about 15% of the heat generated by an exothermic chemical reaction is supplied to the pyrolysis surface, and a large portion of energy is convected with the forward gas flow. The CO molar fraction reaches to a maximum of about 11% for dodecane and 8% for other fuels as ethylene, propane, propylene and heptane. The maximum mean value of CO concentration depends mainly on fuel injection rate, and appears practically insensitive to oxidizer flow velocity. Dodecane and heptane with a longer carbon chain produces more CO and less unburnt hydrocarbons than ethylene, propane and propylene. The existence of large unburnt toxic gas fuels even for a smaller flame size because of the absence of natural convection has important considerations for spacecraft fire safety due to smoke/gas incapacitation.

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Section: Introductionmentioning

confidence: 84%

Section: Introductionmentioning

confidence: 99%

Impact of Fuel Type on Toxic Emissions from a Non-premixed Boundary Layer Laminar Flame in Microgravity – A Numerical Study

Wang

2022

Microgravity Sci. Technol.

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“…CFD modelling of polymer pyrolysis is also extensively applied in hybrid rocket engines [ 21 ]. Tyurenkova et al [ 22 , 23 , 24 , 25 ] conducted a comprehensive series of numerical studies on solid fuel pyrolysis in hybrid rocket engines and investigated the regression behaviour in different flow regimes. It has been found that turbulent transfer coefficients, such as Prandtl number play an essential role to model the gas-solid surface interactions and the regression rate.…”

Section: Introductionmentioning

confidence: 99%

“…All the reviewed works demonstrated MD simulations as a viable tool for investigating the pyrolysis chemistry of polymer systems and highlights the capability to identify the detailed decomposition process from solid to gas phases, which could further act as the precursors of combustible fuel gases in CFD combustion models. Although it is suggested that the turbulent transfer coefficients also plays an essential role, surpassing the molecular transfer coefficients in the numerical investigations [ 22 , 23 , 24 , 25 ]. MD simulations are able to identify the pyrolysis behaviour and flame retardancy mechanism at the molecular level.…”

Section: Introductionmentioning

confidence: 99%

An Investigation towards Coupling Molecular Dynamics with Computational Fluid Dynamics for Modelling Polymer Pyrolysis

et al. 2022

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Building polymers implemented into building panels and exterior façades have been determined as the major contributor to severe fire incidents, including the 2017 Grenfell Tower fire incident. To gain a deeper understanding of the pyrolysis process of these polymer composites, this work proposes a multi-scale modelling framework comprising of applying the kinetics parameters and detailed pyrolysis gas volatiles (parent combustion fuel and key precursor species) extracted from Molecular Dynamics models to a macro-scale Computational Fluid Dynamics fire model. The modelling framework was tested for pure and flame-retardant polyethylene systems. Based on the modelling results, the chemical distribution of the fully decomposed chemical compounds was realised for the selected polymers. Subsequently, the identified gas volatiles from solid to gas phases were applied as the parent fuel in the detailed chemical kinetics combustion model for enhanced predictions of toxic gas, charring, and smoke particulate predictions. The results demonstrate the potential application of the developed model in the simulation of different polymer materials without substantial prior knowledge of the thermal degradation properties from costly experiments.

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“…Lee 14 thermodynamically analyzed the effect of inlet air temperature on the performance of SFRJs and showed that the higher inlet temperature leads higher combustion efficiencies but with lower performance efficiencies. Tyurenkova and Smirnova 15 introduced the exact solution for the solid fuel surface burning in an oxidizer cross flow for the steady diffusion flame and showed that the zone corresponding to chemical kinetics is very small and the main role is played by the diffusion process. They also demonstrated that the fuel regression rate increases with increasing external flow velocity.…”

Section: Introductionmentioning

confidence: 99%

Burning rate augmentation in solid fuel ramjets by swirling inlet air stream

Tahsini

2021

Proceedings of the Institution of Mechanical Engineers, Part G:

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The influence of the inlet swirling flow on the regression rate of the fuel in the combustion chamber of the solid fuel ramjet is investigated in this study using numerical simulations. The finite-volume solver of the compressible turbulent reacting flow is developed to study the flow field where the burning rate is computed using the conjugate heat transfer method for the solid fuel. The correlation is found for the maximum regression rate versus an imposed inlet swirl when the linear distribution of the circumferential velocity is applied at the inlet stream. Although the regression rate augmentation is considerable due to the swirling flow field in the combustor, it is shown that the swirl is effective if is applied near the shear layer of the backstep flow in the combustor. The modified swirler with short blades is suggested to be used in solid fuel ramjets to increase the regression rate of the fuel and improve the performance, but with lower pressure loss.

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Material combustion in oxidant flows: Self-similar solutions

Cited by 85 publications

References 19 publications

Impact of Fuel Type on Toxic Emissions from a Non-premixed Boundary Layer Laminar Flame in Microgravity – A Numerical Study

Impact of Fuel Type on Toxic Emissions from a Non-premixed Boundary Layer Laminar Flame in Microgravity – A Numerical Study

An Investigation towards Coupling Molecular Dynamics with Computational Fluid Dynamics for Modelling Polymer Pyrolysis

Burning rate augmentation in solid fuel ramjets by swirling inlet air stream

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