• KAUST Research Conference: Combustion in Extreme Conditions

KAUST Research Conference
Combustion in Extreme Conditions

March 5-8, 2018

AgendaTalk Details

General Correlations of High-Pressure, High-Temperature Turbulent Burning Velocities with the Consideration of Lewis Number Effect

11:15 - 11:45 KAUST

Level 0 lecture hall between Al-Jazri and Al-Kindi (buildings 4 and 5)

  • Shenqyang (Steven) Shy

    Shenqyang (Steven) Shy

​Abstract

Possible general correlations of high-pressure turbulent burning velocities (ST) are

discussed by using three different fuel/air mixtures with different effective Lewis number

(Le), i.e. pre-vaporized stoichiometric iso-octane with Le≈1.43 at T=423K, hydrogen at

the equivalence ratio φ=0.6 with Le≈0.58 and propane at φ=0.7 with Le≈1.62 at 298K.

Experiments were conducted in a large dual-chamber, constant-temperature/pressure,

fan-stirred 3D cruciform burner capable of generating near-isotropic turbulence.

Schlieren images of spherical expanding turbulent flames were recorded to obtain the

mean flame radii <R(t)> and the observed flame speeds, SF and/or d<R>/dt, where SF is

the slope of <R(t)> which equals the average of d<R>/dt within 25 mm ≤ <R(t)> ≤ 45

mm. Using the density correction and Bradley’s mean progress variable converting factor

for schlieren spherical flames from 𝑐 = 0.1 to 0.5, ST,c=0.5 ≈ (ρb/ρu)SF(<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 ST,c=0.5/SL than that of Le > 1 flames, where SL is the laminar

burning velocity. It is found that all scattering ST,c=0.5/SL data with Le < 1 and Le > 1

together with previous methane data at 300K/423K with Le ≈ 1 can be well collapsed

onto the following three general correlations, regardless of different fuel, T, p, u′, φ, and

Le. (1) ST,c=0.5/SL ≈ 2.54[(u′/SL)(p/p0)Le-1]0.42 where u′ is the rms turbulent fluctuating

velocity, p is pressure, and p0 = 1 atm; (2) ST,c=0.5/SL ≈ 0.26(ReT,flameLe-1)0.5 where ReT,flame

= (u'/SL)(<R>/δL) and δL is the laminar flame thickness; (3) ST,c=0.5/u' ≈ 0.09(DaLe-1)0.5

where the Damköhler number Da = (LI/u′)(SL/δL) and LI is the turbulent integral length

scale, suggesting the possibility of unified correlations when the separate scalings are

rescaling and grouping with Le-1.