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1 Journal of the Combustion Society of Japan Vol.51 No.156 (2009) ORIGINAL PAPER 逆火限界付近における層流火炎基部の局所燃焼速度に与えるバーナ温度の影響 Influence of Burner Temperature on Local Burning Velocity at Laminar Flame Base just before Flashback 1 * 2 SOGO, Sakurako 1 * and YUASA, Saburo Tokyo Gas Co., Ltd., Minamisenju, Arakawa-ku, Tokyo , Japan Tokyo Metropolitan University, 6-6 Asahigaoka, Hino, Tokyo , Japan ; Received 7 October, 2008; Accepted 18 January, 2009 Abstract : Various factors that influence flame flashback of a laminar flame were studied. We focused on a stationary laminar flame base just before flame flashback to apply concepts of stationary conditions. In our experiments the flame stretch rate and the heat release rate in the vicinity of a lean methane/air premixed flame base were quantitatively measured using a single, rectangular port burner that controlled the surface temperature. The variations of the flame temperature and the mass flux were led from the analytical equations, that the previous study had shown, and our experimental results. In order to examine the mechanism of a flashback occurrence, it was explained that the equilibrium position between the fluid velocity and the burning velocity was located near the maximum position of the flame stretch rate along the flame. At this position, the local burning velocity estimated from the analytical equations increased in the maximum by 9% from the laminar burning velocity because the contribution of the flame curvature is the largest between factors that relate to the variations of the the local burning velocity. This result shows that the flame curvature according to the flame shape at the equilibrium position between the fluid velocity and the burning velocity becomes the main factor to occur the flashback. Key Words : Flashback, Flame stretch, Heat release rate, Burner temperature, Local burning velocity 1. 緒言 NOx [ 1-3] [4] * Corresponding author. sakurako@tokyo-gas.co.jp [5-9] [10,11] [12] (50)

2 135 [9] 2. 実験装置 1 14 mm 3 K 100 mm #100 4 ( 160 mm) 50 mm Fig.1 Schematic of the experimental apparatus. 1 CH 4 tank; 2 air compressor; 3 dryer; 4,5 mass flow controller; 6 mixing tube; 7 flashback arrester; 8 flow straightener; 9 water-cooled wall; 10 heater; 11 quartz window; 12 burner port; 13 temperature controller. Fig.2 Schematic diagram of the optical system. 3. 実験方法 3.1. 逆火限界測定 ±5 K (50 mm ) (51)

136 51 156 2009 3.2. 火炎基部における流速および温度分布測定 (PIV = Particle Image Velocimetry) 2 PIV Nd:YAG ( : 532 nm, : 20 mj@532 nm, 3 5 ns) ( : 25 (w) 0.6 (t) mm) ( : 1.1 μm) CCD ( : 1300 (H) 1030 (V) : 6.7 (H) 6.

3 火炎基部における流速および温度分布測定 (PIV = Particle Image Velocimetry) 2 PIV Nd:YAG ( : 532 nm, : 20 mj@532 nm, 3 5 ns) ( : 25 (w) 0.6 (t) mm) ( : 1.1 μm) CCD ( : 1300 (H) 1030 (V) : 6.7 (H) 6.7 (V) μm PIV :34 34 (0.22 mm 0.22 mm) : 100 μs) K PIV 3 % 0.05 mm R ( ±5 ) 0.5 mm K ( ±4 ) Fig.3 Direct photograph of a methane/air flame (without heating, V m = 0.5 m/s, f = 0.71) 火炎基部における測定範囲 3 4 A [4] x y x = 7 mm A A A A 4.5 A 4. 実験結果および考察 Fig.4 Schematic illustration of burning velocity and fluid velocity above the burner rim and measurement range along the flame 逆火限界 T w 323, 373, 473 K 5(a) (293 K 1 ) V m φ 323 K 323 K (52)

4 137 (a) Flashback and blow-off limits (b) Flashback limit near V m =0.5 m/s Fig.5 Influence of burner temperature on flashback limit. 5(a) 5(b) V m = 0.5 m/s 5(b) V m = 0.5 m/s T w = 323, 373, 473 K ffb = 0.68, 0.67, (a) 6 T w V m = 0.5 m/s 1 mm x = 7 mm -7 mm x = 7 mm T u 6 T w = 323, 373, 473 K T u = 320, 360, 440 K 4.2. 火炎伸長 7 PIV T w = 373 K V m = 0.5 m/s ffb = 0.67 T w T w T w k [13] (1) Fig.6 Temperature profiles of unburned gas at the burner port without flame at V m =0.5 m/s. Fig.7 One of the velocity vector distribution using the PIV (V m =0.5 m/ s, ffb =0.67 at T w =373 K). (53)

138 51 156 2009 Fig.8 Flame stretch rate k along the flame (V m =0.5 m/s, ffb = 0.68, 0.67 and 0.

A = 0 y = f (x) (1) k f (x) [14] 4 7 k k 7 2 x y 8 x = 7 mm 8 k x = 7.5 mm k T w k 4.3.

5 Fig.8 Flame stretch rate k along the flame (V m =0.5 m/s, ffb = 0.68, 0.67 and 0.65 at T w = 323, 373 and 473 K respectively). A = 0 y = f (x) (1) k f (x) [14] 4 7 k k 7 2 x y 8 x = 7 mm 8 k x = 7.5 mm k T w k 4.3. 火炎からバーナへの熱流束 q L q L mm x = 7 9 mm T w = 373 K PIV 0.25 m/s T a 0.05 mm R T w = K T a K [16] (2) T w = K q L W/m 2 T w q L 4.4. 局所火炎温度および局所燃焼速度 9 d T A f A T,st A T,f A T,st d M A M,st A M,f (3) (4) (5) T Y u C p r l D u (2) h(= Re 1/2 Pr 1/3 l/l) [15] Re Pr l T a L (x = 7 9 mm) (2 mm) Re 0.5 Fig.9 Schematic showing definitions of the various surfaces of a curved flame in a nonuniform flow. (54)

6 139 b T u M u q q L C.J.Sun [9] q (6) (8) (11) (10) (11) (12) (6) (7) = d T 0 /S u 0 S u 0 a 0 S 0 u T u CHEMKIN II PREMIX [17] GRI-Mech. 3.0[18] T w Su , 0.32,0.45 m/s a 0 Sun [9] T b T ad a 0 = 1 + ln[t u /T ad +(1- T u /T ad ) -1 ] T w a (6) Sun [9] q Ze (8) (9) (9) c (8) (9) (10) (12) k Q c (12) (9) (6) (9) (12) u (9) (12) S u 10 10(a)(b) T w = K x = 7.5 mm Su u 4 A 8 T w 4 A 8 10 S u u S u (12) T w = 473 K S u u A (a) T w = 323 K, ffb = 0.68 (b) T w = 373 K, ffb = 0.67 Fig.10 Normal element of fluid velocity and local burning velocity along the flame. (55)

140 51 156 2009 Fig.11 Ratio of influence factors on local flame temperature. Fig.12 Ratio of influence factors on local burning velocity.

5 % T w T b (6) T w = 323 373 473 K 1854 1879 1924 K 1 [11] S 0 u 1 12 (12) 12 c 12 T w = 323 373 K 1 9 % T w T w = 473K 0 S u (9) (12)

7 Fig.11 Ratio of influence factors on local flame temperature. Fig.12 Ratio of influence factors on local burning velocity 熱流束および火炎伸長の寄与率 (6) 11 [19,20] T w % 2.5 % T w T b (6) T w = K K 1 [11] S 0 u 1 12 (12) 12 c 12 T w = K 1 9 % T w T w = 473K 0 S u (9) (12) T w = K m/s u T u = K T w = 323 K (T u = 320 K) 1 T w = K T w = 323 K (S u = 0.27 m/s) 1 T w = K T w T w 12 T w 5 5. 結言 / (56)

8 % 2.5 % 9 % 1) 2) 3) References 1. D. Thibaut and S. Candel, Combust. Flame, 113: (1998). 2. Kröner, M., Fritz, J. and Sattelmayer, T., Proceedings of ASME TURBO EXPO 2002: GT (2002). 3. Kato, S., Fujimori, T. and Kobayashi, H., J. Combust. Soc. Japan, 50, 151: (2008) 4. Lewis, B. and von Elbe, G., Combustion, Flames and Explosions of Gases (3rd Ed.), Academic Press, New York (1987). 5. Matalon, M., Combust. Sci. and Tech. 31: (1983). 6. Law, C. K., Zhu, D. L. and Yu, G., Proc. Combust. Inst., 21: (1986). 7. Chung, S. H. and Law, C. K., Combust. Flame, 72: (1988). 8. Sun, C. J., Sung, C. J., He. L. and Law, C. K., Combust. Flame, 118: (1999). 9. Sun, C. J. and Law, C. K., Combust. Flame, 121: (2000). 10. Kim, N. I., Lee, U. D. and Shin, H. D., Proc. Combust. Inst., 28: (2000). 11. Kurdumov, V. N., Fernández, E. and Liñán, A., Proc. Combust. Inst., 28: (2000). 12. Mallens, R. M. M. and DE Goey, L. P. H., Combust. Sci. and Tech., 136: (1998). 13. Chung, S. H. and Law, C. K., Combust. Flame, 55: (1984). 14. Yokomori, T. and Mizomoto, M., JSME Trans. B., 67, 664: (2001), (in Japanese). 15. Incropera, F. P. and Dewitt, D. P., Fundamentals of Heat and Mass Transfer (3rd Ed.), John Wiley & Sons, New York (1990). 16. Koizumi, H., Iwai, K., Yang, X., Dobashi, R. and Hirano, T., Nensho-no-Kagaku-to-Gijutsu, 6: (1999), (in Japanese). 17. Kee, R. J., et. al., Sandia Report, SAND (1985). 18. Smith, G. P., Golden, D. M., Frenklach, M., Moriarty, N. W., Eiteneer, B., Goldenberg, M., Bowman, C. T., Hanson, R. K., Song, S., Gardiner Jr., W. C., Lissianski, V. V., and Qin, Z., (1999) 19. Law, C. K., Proc. Combust. Inst., 22: (1988). 20. Mizomoto, M., Ueda, T. and Uchino, Y., JSME Trans. B., 57, 534: (1991), (in Japanese). (57)

Journal of the Combustion Society of Japan Vol.58 No.185 (2016) ORIGINAL PAPER 火災旋風近傍の流れに関する研究 Flow Around a Fire Whirl *

58 185 2016 167-171 Journal of the Combustion Society of Japan Vol.58 No.185 (2016) 167-171 ORIGINAL PAPER 火災旋風近傍の流れに関する研究 Flow Around a Fire Whirl * ONISHI, Hiroyuki and KUWANA, Kazunori 992-8510 4-3-16