脈衝式相向噴流擴散火焰研究

A Study on Impinging Diffusion Flame by Pulsation

鄭家俊(Chia-Chun Cheng)

指導教授 ： 蘇 艾

元智大學/工程學院/機械工程學系/碩士(2000年)

摘要

本實驗主要在研究脈衝式相向噴流擴散火焰燃燒結構，藉由控制燃料流速和燃料供應脈衝頻率來觀察脈衝式相向噴流擴散火焰之結構變化。本實驗是將電磁閥裝設於噴嘴上游的位置、並成一直線的排列方式裝設，並以從 2 Hz 到 17 Hz之間的開閉週期來控制甲烷燃料。開閉循環所導致的結果顯示明顯地的增加了甲烷燃料的波動。 因此脈衝相向噴流擴散火焰的發展得比連續的相向噴流擴散火焰更為快速，火焰也因此而矮化了。 由Re = 97至Re = 161之間的最有效的脈動頻率在 9 到 11 Hz附近。 在最有效的脈動頻率和全開條件(沒有脈衝)之下其噴流衝擊面中心線溫度差別範圍是從 100 到 150 度。脈衝影響對於低 Reynolds 數狀態下的擴散火焰燃燒更為重要。當燃料雷諾數為129時，相向噴流擴散火焰的焰尖在撞擊點上面的Y/Din=23處明顯地穿過。由於脈衝相向噴流擴散火焰的現象，所以不可能在所量測到的平均溫度等溫線圖中清楚地確定焰面或者焰尖。當雷諾數為129、燃氣脈衝頻率為11Hz時，結果顯示脈衝火相向噴流擴散火焰的平均溫度輪廓線末端出現在以撞擊點上面的 Y/Din=21 處。根據觀察和實驗, 脈衝相向噴流擴散火焰表現的比相向噴流擴散火焰來的更為穩定和有效率。

關鍵字

擴散火焰 ； 脈衝相向噴流 ； 相向噴流

並列摘要

Experimental investigations on the pulsating jet-impinging diffusion flame were executed. A solenoid valve was aligned upstream of the jet orifice and the methane fuel was controlled in open-closed cycles from 2 Hz to 17 Hz. Results show that the open-closed cycles indeed increase the fluctuations of the methane fuel obviously. The evolutions of pulsating flame therefore develop faster than the continuous impinging flame. The optimized pulsating frequencies are near 9 to 11 Hz from the Re = 97 to 161. The temperature differences between that under optimized pulsating rate and full open condition (no pulsation) are ranging from 100 to 150 degree. The pulsating effect is more significant at low Reynolds number. When Re=129, the tip of the impinging flame obviously crosses at Y/Din=23 above the impinging point. Because of the phenomenon of pulsation flame, the flame sheet or flame front may not be identified clearly in the averaged temperature contours. When Re=129, 11 Hz. Results show that the averaged end-contour of pulsation flame rears at Y/Din=21 above the impinging point. By observation and experiment, the pulsating flame behaves more stable and efficient than the continuous impinging flame.

並列關鍵字

Pulsation flame ； Jet-impingement ； Diffusion flame ； Pulsation

參考文獻

Bain, D. B. and Smith, C. E., 1995, “ Mixing Analysis of Axially Opposed Rows of Jet Injected into Confined Crossflow, “ Journal of Propulsion and Power, Vol. 11, No. 5, pp. 885 — 893

B. Lenze, M. E. Milano, and R. Gunther, 1975, “ The Mutial Influence of Multiple Jet Diffusion Flame, ” Combustion Science and Technology, Vol. 11, pp. 1 - 8

Kostiuk, L. W. and Cheng, R. K., 1992, “ Premixed Turbulent Combustion in Opposed Streams, “ De 92 — 016996.

Liu, T. M., Hwang, Y. H. and Wu, S. M., 1990, “ The Three — Dimensional Jet — Jet Impingement Flow in a Closed — End Cylindrical Duct,“ Journal of Fluids Engineering, Vol. 112, June, pp. 171 — 178.

Milson, A. and Chigier, N. A., 9173, “ Studies of Methane and Methane — Air Flames Impinging on a Cold Plate, “ Combustion and Flame, 21, pp. 295 — 305