The diffusive-thermal instability of premixed flames with low unburned-gas temperature under the adiabatic and non-adiabatic conditions

Aung, Thwe Thwe; Kadowaki, Shigenori

doi:10.1299/mej.14-00460

Cited by 2 publications

(1 citation statement)

References 18 publications

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“…This approach successfully combines the DLI 27 – 29 with the Markstein effect which reflects the thermal and mass diffusivities 30 – 32 . The numerical study to understand the dynamics of a flame front has been performed for cellular and non-cellular fronts 33 , 34 and for cellular front with heat loss 35 – 37 . Despite of many works on the instability of a flame front, the influence of heat release and viscosity on the stability boundaries of cellular and oscillatory instabilities has not ever been declared clearly.…”

Section: Introductionmentioning

confidence: 99%

Effect of small heat release and viscosity on thermal-diffusive instability

Wada

2021

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The linear stability of a thermal reaction front has been investigated based on the thermal-diffusive model proposed by Zel’dovich and Frank-Kamenetskii, which is called ZFK model. In the framework of ZFK model, heat-conduction and mass-diffusion equations are treated without the effect of hydrodynamic flow. Then, two types of instability appear: cellular and oscillatory instabilities. The cellular instability has only positive real part of growth rate, while the oscillatory instability is accompanied with non-zero imaginary part. In this study, the effect of heat release and viscosity on both instabilities is investigated asymptotically and numerically. This is achieved by coupling mass-conservation and Navier–Stokes equations with the ZFK model for small heat release. Then, the stable range of Lewis number, where the real part of growth rate is negative, is widened by non-zero values of heat release for any wavenumber. The increase of Prandtl number also brings the stabilization effect on the oscillatory instability. However, as for the cellular instability, the viscosity leads to the destabilization effect for small wavenumbers, opposed to its stabilization effect for moderate values of wavenumber. Under the limit of small wavenumber, the property of viscosity becomes clear in view of cut-off wavenumber, which makes the real part of growth rate zero.

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Section: Introductionmentioning

confidence: 99%

Effect of small heat release and viscosity on thermal-diffusive instability

Wada

2021

Sci Rep

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The effects of unburned-gas temperature on intrinsic instability of premixed flames at high Lewis numbers under the adiabatic and non-adiabatic conditions

Aung

Katsumi

Kadowaki

2017

Mechanical Engineering Journal

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We treated numerically premixed flames at high Lewis numbers under the adiabatic and non-adiabatic conditions to elucidate the effects of unburned-gas temperature on intrinsic instability. Numerical calculations of two-dimensional unsteady reactive flow were performed, based on the compressible Navier-Stokes equation including one-step chemical reaction. Lewis numbers higher than unity were adopted, and radiative heat loss was employed. Superimposing a sinusoidal disturbance with sufficiently small amplitude on a stationary planar flame, we obtained the relation between the growth rate and wave number, so-called dispersion relation. When the Lewis number was higher than unity, the growth rate was small and the unstable range was narrow, compared with premixed flames at Lewis number of unity, which was because of the weakness of intrinsic instability due to diffusive-thermal effects. As the unburned-gas temperature became higher, the growth rate increased and the unstable range widened. This was because of the increase of the burning velocity of a planar flame. Taking account of radiative heat loss, we obtained small growth rates and narrow unstable range. To study the characteristics of cellular flames generated by intrinsic instability, we superimposed a disturbance with the critical wave number corresponding to the maximum growth rate. The superimposed disturbance evolved, and a cellular flame formed. The burning velocity of a cellular flame normalized by that of a planar flame decreased as the unburned-gas temperature became higher. As the heat loss became larger, the normalized burning velocity of a cellular flame decreased. This indicated that the heat loss inhibited the instability of premixed flames at high Lewis numbers.

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The diffusive-thermal instability of premixed flames with low unburned-gas temperature under the adiabatic and non-adiabatic conditions

Cited by 2 publications

References 18 publications

Effect of small heat release and viscosity on thermal-diffusive instability

Effect of small heat release and viscosity on thermal-diffusive instability

The effects of unburned-gas temperature on intrinsic instability of premixed flames at high Lewis numbers under the adiabatic and non-adiabatic conditions

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