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Số người truy cập: 29,587,727

 High-temperature, high-pressure burning velocities of expanding turbulent premixed flames and their comparison with Bunsen-type flames
Tác giả hoặc Nhóm tác giả: L.J. Jiang, S.S. Shy, W.Y. Li, H.M. Huang, M.T. Nguyen
Nơi đăng: Combustion and Flame; Số: 172;Từ->đến trang: 173-182;Năm: 2016
Lĩnh vực: Kỹ thuật; Loại: Bài báo khoa học; Thể loại: Quốc tế
TÓM TẮT
ABSTRACT
This paper reports high-temperature, high-pressure turbulent burning velocities and their correlation of expanding unity-Lewis-number methane/air turbulent flames, propagating in near-isotropic turbulence in a large dual-chamber, constant-pressure/temperature, fan-stirred 3D cruciform bomb. In it a novel heating method is used to ensure that the temperature variation in the domain of experimentation is less than 1oC. Schlieren images of statistically spherical expanding turbulent flames are recorded to evaluate the mean flame radius <R(t)> and the observed flame speeds, d<R>/dt and SF (the slope of <R(t)>), where SF is found to be equal to the average value of d<R>/dt within 25 mm ≤ <R(t)> ≤ 45 mm. Results show that the normalized turbulent flame speed scales as a turbulent flame Reynolds number ReT,flame = (u'/SL)(<R>/dL) roughly to the one-half power: (SLb)-1d<R>/dt ≈ (SLb)-1SF = 0.116ReT,flame0.54 at 300 K and 0.168ReT,flame0.46 at 423 K, where u′ is the rms turbulent fluctuating velocity, SL and SLb are laminar flame speeds with respect to the unburned and burned gas, and dL is the laminar flame thickness. The former at 300 K agrees well with Chaudhuri et al. (2012) except that the present pre-factor of 0.116 and ReT,flame up to 10,000 are respectively 14% and four-fold higher. But the latter at 423 K shows that values of (SLb)-1d<R>/dt bend down at larger ReT,flame. Using the density correction and Bradley’s mean progress variable <c> converting factor for Schlieren spherical flames, the turbulent burning velocity at <c>=0.5, ST,c=0.5 ≈ (rb/ru)SF(<R>c=0.1/<R>c=0.5)2, can be obtained, where the subscripts b and u indicate the burned and unburned gas. It is found that all scattering data at different temperatures for spherical flames can be better represented by ST,c=0.5/SL = 2.9[(u′/SL)(p/p0)]0.38, first proposed by Kobayashi for Bunsen flames. Comparison and discussion are offered.
[ 1-s2.0-s0010218016301857-main.pdf ]
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