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Abstract
This study measures highpressure turbulent burning velocities (S_{T}) of spherical expanding flames for various liquid and gaseous fuel/air mixtures with different effective Lewis number (Le), i.e. prevaporized stoichiometric isooctane with Le»1.43 at T=423K, hydrogen at the equivalence ratio φ=0.6 with Le»0.58 at 298K, and propane at φ=0.7 with Le»1.62 at 298K, using the same dualchamber, fanstirred cruciform burner capable of generating nearisotropic turbulence. Highspeed schlieren imaging is used to obtain the temporal growth of mean flame radii<R(t)>and the observed flame speeds, S_{F} and/or d<R>/dt, where S_{F} is the slope of<R(t)>which equals the average of d<R>/dt within 25mm≤<R(t)>≤45mm. Using the density correction and Bradley's mean progress variable converting factor for schlieren spherical flames from c=0.1 to 0.5, S_{T,c=0.5}»(ρ_{b}/ρ_{u})S_{F}(<R>_{c=0.1}/<R>_{c=0.5})^{2}, where the subscripts b and u indicate the burned and unburned gas. Results show that Le<1 flames have much higher S_{T,c=0.5} than that of Le>1 flames at any given rms turbulent fluctuating velocities (u′) and pressure (p). We find that these very scattering S_{T,c=0.5} data with Le<1 and Le>1 together with previous methane data at 300K/423K with Le»1 can be well represented by three modified general correlations originally proposed by Kobayashi et al. (2005), Chaudhuri et al. (2012), and Shy et al. (2012) when their scaling parameters are rescaling and grouping with Le^{1}, each representing a single curve with small data scattering. This suggests a possible selfsimilar propagation for turbulent spherical flames, regardless of different fuels, T, p, u′ used. Discussion and comparison with the Bradley's correlation (1992) are offered and future studies identified.
Original language  English 

Pages (fromto)  23912398 
Number of pages  8 
Journal  Proceedings of the Combustion Institute 
Volume  37 
Issue number  2 
DOIs  
State  Published  2019 
Keywords
 expanding turbulent flames
 general correlations
 Highpressure turbulent burning velocity
 Isooctane, hydrogen and propane
 Lewis, Reynolds, and Damköhler numbers
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 1 Finished

Advanced Experimental Studies on HighPressure, HighTemperature Premixed Turbulent Combustion(2/3)
1/08/18 → 31/07/19
Project: Research