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燃燒空氣散布角對高溫空氣燃燒影響的數值研究

注意:本論文已在《工業加熱》2008,37(3):36–40發表
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蘇亞欣, 趙丹, 胡 峰
(東華大學環境學院,上海201620)

摘 要:以高溫空氣燃燒技術為應用背景,對多股射流對爐內燃燒特性的影響進行了數值模擬,討論了燃燒空氣散布角對燃燒特性的影響。采用標準的k-eg2方程模型計算流場,氣相燃燒模型采用 函數的PDF燃燒模型,采用離散坐標法模擬輻射換熱過程,NOx模型為熱力型NOx,燃燒室尺寸為800mm×800mm×l 400mm,燃料噴口為圓形,直徑為10mm,位于中心。空氣噴口設計為5個等面積的圓形置于燃氣噴口周圍。計算結果表明, 由于射流之間的相互作用,在爐膛內存在回流區。煙氣的回流一方面加強了燃料和空氣的混合,使溫度分布更為均勻,同時改變了爐膛空間內的燃料和氧的分布,從而影響燃燒強度和NOx的局部生成。燃燒空氣散布角 小,燃料、氧以及燃燒后的高溫煙氣等的混合越充分,燃燒越穩定,低氧區域擴大,溫度分布均勻,局部高溫受到抑制,局部NOx的生成減少。 較大時,噴嘴布置接近于同軸射流,高溫煙氣的回流主要起到穩定燃燒的作用,而周向的低氧條件將不復存在,低氧燃燒將轉化為強化燃燒。在l5%的氧條件下, =120。時與 =360。相比,NOx排放量可減少65%。研究結果對高溫空氣燃燒噴嘴結構設計及運行管理具有參考價值。
關鍵詞: 高溫空氣燃燒;多股射流噴嘴;空氣散布角;流場;溫度場;NOx排放
中圖分類號:TQ 127.1 1 文章編號: 1007—8827(2005)0143058-05

Numerical Simulation of the Efect of the Straddle Angle of Preheated Air on the High Temperature Air Combustion

SU Ya-xin,ZHAO Dan,HU Feng
(School of Environmental Science and Engineering,Donghua University,Shanghai 20 1 620,China)

Abstract:A numerical simulation was carried out on the flow and combustion in an industrial furnace with a multi-jet burner for the application of High Temperature Air Combustion technology.The efect ofthe s~addle angle ofthe preheated air on the combustion characteristics in the furnace was discussed.The standard k-e model was used to calculate the flow field and PDF(Probability Density Function)combustion model based on a function was selected to simulate the gas combustion.The radiation was simulated by a Discrete Ordinates method.The NOx was simulated by thermal NOx mode1.Th e furnace was a rectangular chamber of 800 mm ×800 mm ×l 400 mm.A circular fuel jet of a
diameter of 1 0mm is at the center ofthe wal1.5 circular air{ets equably distributed around the fuel iet witll diferent straddle angles.The results showed that there was the recirculation zone in the furnace due to the interaction of the ets.Th e recirculation of the flue.gas strengthened the mixing ofthe air and fuel,leading to a more even temperature distribution.At the mean while,it chan ged the local distribution ofthe fuel and oxygen in the furnace and then influenced the local NOx generation and the final emission.The smaller the straddle an gle ofthe preheated air was,the beaer the mixing of the fuel,oxygen and the flue gas became,which resulted in a stable flame,an enlarged low·oxygen zone,an equable temperature distribution and a suppressed local high temperature.When the straddle angle of the preheated air increased,the burner disposal is more like thejets with the sarne axis.The recirculation ofthe high temperature flue gas in the fumace only played the role to stabilize the combustion and the local low oxygen region will disappear.At the 15% O2 condition,when the straddle angle ofthe preheated air is 120。 the final NOx emission can be reduced about 65% compared with that when the straddle angle ofthe preheated air is 360。.
Key words:hi temperature air combustion;multi-jet burner;s~addle angle of the preheated air;NOx emissio

 

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