Experimental observation of pulsating instability under acoustic field in downward-propagating flames at large Lewis number
KAUST DepartmentClean Combustion Research Center
Permanent link to this recordhttp://hdl.handle.net/10754/626037
MetadataShow full item record
AbstractAccording to previous theory, pulsating propagation in a premixed flame only appears when the reduced Lewis number, β(Le-1), is larger than a critical value (Sivashinsky criterion: 4(1 +3) ≈ 11), where β represents the Zel'dovich number (for general premixed flames, β ≈ 10), which requires Lewis number Le > 2.1. However, few experimental observation have been reported because the critical reduced Lewis number for the onset of pulsating instability is beyond what can be reached in experiments. Furthermore, the coupling with the unavoidable hydrodynamic instability limits the observation of pure pulsating instabilities in flames. Here, we describe a novel method to observe the pulsating instability. We utilize a thermoacoustic field caused by interaction between heat release and acoustic pressure fluctuations of the downward-propagating premixed flames in a tube to enhance conductive heat loss at the tube wall and radiative heat loss at the open end of the tube due to extended flame residence time by diminished flame surface area, i.e., flat flame. The thermoacoustic field allowed pure observation of the pulsating motion since the primary acoustic force suppressed the intrinsic hydrodynamic instability resulting from thermal expansion. By employing this method, we have provided new experimental observations of the pulsating instability for premixed flames. The Lewis number (i.e., Le ≈ 1.86) was less than the critical value suggested previously.
CitationYoon SH, Hu L, Fujita O (2018) Experimental observation of pulsating instability under acoustic field in downward-propagating flames at large Lewis number. Combustion and Flame 188: 1–4. Available: http://dx.doi.org/10.1016/j.combustflame.2017.09.026.
SponsorsThe author would like to acknowledge the support from these projects: A Grant-in-Aid for Scientific Research (KIBAN (B) No. 26289042) from MEXT Japan, Key project of National Natural Science Foundation of China (NSFC) under Grant No. 51636008 and Key Research Program of Frontier Sciences, Chinese Academy of Science (CAS) under Grant No. QYZDB-SSW-JSC029. The authors thank Dr. M. S. Cha for his valuable assistance.
JournalCombustion and Flame
Showing items related by title, author, creator and subject.
Stability analysis of non-autonomous reaction-diffusion systems: the effects of growing domainsMadzvamuse, Anotida; Gaffney, Eamonn A.; Maini, Philip K. (Journal of Mathematical Biology, Springer Nature, 2009-08-29) [Article]By using asymptotic theory, we generalise the Turing diffusively-driven instability conditions for reaction-diffusion systems with slow, isotropic domain growth. There are two fundamental biological differences between the Turing conditions on fixed and growing domains, namely: (i) we need not enforce cross nor pure kinetic conditions and (ii) the restriction to activator-inhibitor kinetics to induce pattern formation on a growing biological system is no longer a requirement. Our theoretical findings are confirmed and reinforced by numerical simulations for the special cases of isotropic linear, exponential and logistic growth profiles. In particular we illustrate an example of a reaction-diffusion system which cannot exhibit a diffusively-driven instability on a fixed domain but is unstable in the presence of slow growth. © Springer-Verlag 2009.
Linear Simulations of the Cylindrical Richtmyer-Meshkov Instability in Hydrodynamics and MHDGao, Song (2013-05) [Thesis]
Advisor: Samtaney, Ravi
Committee members: Samtaney, Ravi; Stenchikov, Georgiy L.; Thoroddsen, Sigurdur TThe Richtmyer-Meshkov instability occurs when density-stratified interfaces are impulsively accelerated, typically by a shock wave. We present a numerical method to simulate the Richtmyer-Meshkov instability in cylindrical geometry. The ideal MHD equations are linearized about a time-dependent base state to yield linear partial differential equations governing the perturbed quantities. Convergence tests demonstrate that second order accuracy is achieved for smooth flows, and the order of accuracy is between first and second order for flows with discontinuities. Numerical results are presented for cases of interfaces with positive Atwood number and purely azimuthal perturbations. In hydrodynamics, the Richtmyer-Meshkov instability growth of perturbations is followed by a Rayleigh-Taylor growth phase. In MHD, numerical results indicate that the perturbations can be suppressed for sufficiently large perturbation wavenumbers and magnetic fields.
Localization in inelastic rate dependent shearing deformationsKatsaounis, Theodoros; Lee, Min-Gi; Tzavaras, Athanasios (Journal of the Mechanics and Physics of Solids, Elsevier BV, 2016-09-18) [Article]Metals deformed at high strain rates can exhibit failure through formation of shear bands, a phenomenon often attributed to Hadamard instability and localization of the strain into an emerging coherent structure. We verify formation of shear bands for a nonlinear model exhibiting strain softening and strain rate sensitivity. The effects of strain softening and strain rate sensitivity are first assessed by linearized analysis, indicating that the combined effect leads to Turing instability. For the nonlinear model a class of self-similar solutions is constructed, that depicts a coherent localizing structure and the formation of a shear band. This solution is associated to a heteroclinic orbit of a dynamical system. The orbit is constructed numerically and yields explicit shear localizing solutions. © 2016 Elsevier Ltd