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燃烧空气散布角对高温空气燃烧影响的数值研究

注意:本论文已在《工业加热》2008,37(3):36–40发表
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苏亚欣, 赵丹, 胡 峰
(东华大学环境学院,上海201620)

摘 要:以高温空气燃烧技术为应用背景,对多股射流对炉内燃烧特性的影响进行了数值模拟,讨论了燃烧空气散布角对燃烧特性的影响。采用标准的k-eg2方程模型计算流场,气相燃烧模型采用 函数的PDF燃烧模型,采用离散坐标法模拟辐射换热过程,NOx模型为热力型NOx,燃烧室尺寸为800mm×800mm×l 400mm,燃料喷口为圆形,直径为10mm,位于中心。空气喷口设计为5个等面积的圆形置于燃气喷口周围。计算结果表明, 由于射流之间的相互作用,在炉膛内存在回流区。烟气的回流一方面加强了燃料和空气的混合,使温度分布更为均匀,同时改变了炉膛空间内的燃料和氧的分布,从而影响燃烧强度和NOx的局部生成。燃烧空气散布角 小,燃料、氧以及燃烧后的高温烟气等的混合越充分,燃烧越稳定,低氧区域扩大,温度分布均匀,局部高温受到抑制,局部NOx的生成减少。 较大时,喷嘴布置接近于同轴射流,高温烟气的回流主要起到稳定燃烧的作用,而周向的低氧条件将不复存在,低氧燃烧将转化为强化燃烧。在l5%的氧条件下, =120。时与 =360。相比,NOx排放量可减少65%。研究结果对高温空气燃烧喷嘴结构设计及运行管理具有参考价值。
关键词: 高温空气燃烧;多股射流喷嘴;空气散布角;流场;温度场;NOx排放
中图分类号:TQ 127.1 1 文章编号: 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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