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通过数值模拟对燃料射流环绕空气射流的五喷口高温空气燃烧的燃烧特性进行了研究.详细阐述了燃烧室内燃烧温度和燃烧组分的分布情况,并对NOx生成及其影响因素进行了分析.结果表明:燃烧室出口可燃物浓度低于0.1%,燃烧反应完全;燃烧反应主要发生在燃料射流包围的圆柱体内,沿射流方向,燃烧逐渐向空气射流方向扩大,燃烧过程缓慢,并在燃烧室后半段稳定燃烧;NOx主要在燃烧室的高温区域形成,降低燃烧室内高温区域的氧气浓度是抑制燃烧过程NOx生成的关键,在燃烧室入口附近,NOx的生成受燃料射流的入口温度影响较大. 相似文献
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以工业炉的高温空气燃烧技术应用为背景,对一个新型轴向旋流式单烧嘴燃烧室内天然气的高温空气燃烧特性进行了数值研究。采用数值模拟的方法研究了同心式轴向旋流燃烧器(HCASbumer)中螺旋肋片的旋转角度对燃烧特性的影响,其中湍流采用Reynolds应力模型,气相燃烧模拟采用β函数形式的PDF燃烧模型,采用离散坐标法模拟辐射换热过程,NOx模型为热力型与快速型。计算结果表明,对预热空气采用旋转射流时,能明显降低NOx生成量。对于HCAS型燃烧器,随着空气射流旋转角度的增大,燃烧室内的回流区域增大增强,降低了局部的氧体积分数分布,燃烧室中平均温度和最高温度都有所增加,且燃烬程度大幅度提高,而局部高温区缩小,只在靠近入口处出现。总的NOx排放量随着空气射流旋转角度的增大先减小,后增大。因此,适当调整肋片的旋转角度可以降低NOx生成量。 相似文献
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《节能技术》2015,(5)
为了减少管式加热炉燃烧NOx的排放和提高加热炉的燃烧效率,实现加热炉的高效低氮燃烧,以某石化公司的F1001常压炉为研究对象,建立了常压炉物理模型,选用标准k-ε模型、非预混合湍流扩散燃烧PDF模型、P-1辐射模型、NOx生成模型对加热炉内的燃烧过程进行了数值模拟研究。研究结果表明:提高空气预热温度可以扩大炉内的高温区域,有利于炉管内原油的加热;燃烧NOx生成量和炉管出口油温随空气预热温度的升高而增大,当空气预热温度超过240℃时,NOx生成量急剧增大,所以空气预热温度以240℃为宜,此时NOx生成量为137 mg/m3,低于国家标准200 mg/m3。炉膛温度和出口油温测量值与模拟值进行了比较,二者吻合较好。研究结果为某企业常压炉的运行监控提供了参考依据。 相似文献
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空气分级燃烧降低NOX排放技术的研究 总被引:2,自引:0,他引:2
利用Fluent数值模拟软件分析了空气分级对高温低氧空气燃烧污染物排放的影响.应用空气分级燃烧技术的燃烧器不仅使燃烧室内具有较高的温度水平,温度场均匀,燃烧效率高,而且NOx的生成量也较低,可以达到节约燃料和降低污染物的综合效果.计算结果分析表明:分级燃烧的二次空气配比对燃烧室内的NOx排放有较大影响.当一次空气占40%左右时,NOx排放最少. 相似文献
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射流间距对高温空气燃烧影响的数值研究 总被引:1,自引:0,他引:1
以高温空气燃烧技术为应用背景,对多股射流燃烧器的燃烧特性进行了数值模拟,讨论了燃料与空气射流喷口间距对燃烧特性的影响.采用标准的k-ε双方程模型计算流场,采用β函数的PDF燃烧模型计算气体燃料的燃烧,采用离散坐标法模拟辐射换热过程.NOx模型为热力型NOx,炉膛尺寸为800mm×800mm×1400mm,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,在炉膛后面存在回流区.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浓度分布,从而影响燃烧强度和NOx的局部生成.当燃料射流喷口与空气射流喷口的间距增大时,能有效地延缓燃料和空气的混合,烟气回流将会增加燃烧室内气体的混合程度,降低燃烧室内局部氧浓度,有利于扩大低氧区域,扩大燃烧区域,并且使炉膛温度变得均匀,减少局部高温区,降低NOx的生成.I=2.5时的NOx排放浓度为45×10-6. 相似文献
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燃气轮机低热值合成气燃烧室内三维湍流流动的数值模拟研究 总被引:3,自引:0,他引:3
对GE-F101型工业燃气轮机环形燃烧室燃用甲烷和低热值合成气的燃烧性能进行了数值研究,采用标准κ-ε湍流模型和涡耗散湍流燃烧模型对燃烧室在不同燃料条件下的流场特性进行了数值模拟,并对燃烧室内的流场结构、温度分布、火焰结构及NOx分布进行了分析与比较;在此基础上对原燃烧室进行了一些改造.结果表明:随着燃料热值的降低,燃料射流速度增大,燃料和空气的混合程度减弱,燃烧稳定性降低,燃烧室内最高温度降低,NOx排放量减少;通过增大燃料喷嘴口径和增加旋流器的旋流数,可在一定程度上改善燃烧室内流动结构,增强燃料和空气的混合程度,因而提高了燃烧稳定性. 相似文献
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This study describes the performance and stability characteristics of a parallel jet MILD (Moderate or Intense Low-oxygen Dilution) combustion burner system in a laboratory-scale furnace, in which the reactants and exhaust ports are all mounted on the same wall. Thermal field measurements are presented for cases with and without combustion air preheat, in addition to global temperature and emission measurements for a range of equivalence ratio, heat extraction, air preheat and fuel dilution levels. The present furnace/burner configuration proved to operate without the need for external air preheating, and achieved a high degree of temperature uniformity. Based on an analysis of the temperature distribution and emissions, PSR model predictions, and equilibrium calculations, the CO formation was found to be related to the mixing patterns and furnace temperature rather than reaction quenching by the heat exchanger. The critical equivalence ratio, or excess air level, which maintains low CO emissions is reported for different heat exchanger positions, and an optimum operating condition is identified. Results of CO and NOx emissions, together with visual observations and a simplified two-dimensional analysis of the furnace aerodynamics, demonstrate that fuel jet momentum controls the stability of this multiple jet system. A stability diagram showing the threshold for stable operation is reported, which is not explained by previous stability criteria. 相似文献
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无焰燃烧具有降低氮氧化物(NO_x)排放的优点.采用耦合骨架化学反应机理的涡耗散概念(EDC)模型,对某常温进气无焰燃烧锅炉的NO_x生成过程进行了三维数值模拟,并进行了实验验证.分析表明,该模型模拟结果与实验测试结果符合较好;无焰燃烧可以实现超低NOx排放,其摩尔分数低于20×10~(-6);NO_x主要在射流下游周围一个较宽广的空间生成;由于反应区加宽,燃烧室最高温度低于1 700 K,热力型NO相对于有焰燃烧锐减;快速型NO极低;N_2O转化型NO成为主要的NO_x生成途径. 相似文献
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设计合理的烧嘴可以控制空气和燃气的混合,从而控制Nox的排放.对6种不同几何结构烧嘴在不同的燃气流速、过量空气系数、燃气流量以及不同燃气与空气喷口间距下的Nox排放量进行了试验研究.结果表明,燃气射流速度的提高可以减少Nox的排放;在空气射流速度大致相等的各个试验工况中,空气喷口为矩形且矩形短轴指向烧嘴中心的燃气喷口时,Nox排放量最高,空气喷口为圆形时次之,空气喷口为矩形且矩形长轴指向燃气喷口时Nox排放量较低.在试验范围内,过量空气系数提高,Nox的排放增加. 相似文献
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M. Ayoub C. Rottier S. Carpentier C. Villermaux A.M. Boukhalfa D. Honoré 《International Journal of Hydrogen Energy》2012
This paper presents an experimental study of mild flameless combustion regime applied to methane/hydrogen mixtures in a laboratory-scale pilot furnace with or without air preheating. Results show that mild flameless combustion regime is achieved from pure methane to pure hydrogen whatever the CH4/H2 proportion. The main reaction zone remains lifted from the burner exit, in the mixing layer of fuel and air jets ensuring a large dilution correlated to low NOx emissions whereas CO2 concentrations obviously decrease with hydrogen proportion. A decrease of NOx emissions is measured for larger quantity of hydrogen due mainly to the decrease of prompt NO formation. Without air preheating, a slight increase of the excess air ratio is required to control CO emissions. For pure hydrogen fuel without air preheating, mild flameless combustion regime leads to operating conditions close to a "zero emission furnace", with ultra-low NOx emissions and without any carbonated species emissions. 相似文献
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《热科学学报(英文版)》2021,(4)
The large consumption of coal in cement industry leads to a significant nitrogen oxide (NO_x) emission,which has caused severe atmospheric pollution due to the existing low-efficiency denitration technologies.In this research,a fuel pretreatment method on the concept of coal preheating was proposed to reduce NO_x emission from cement kilns.A special bench-scale experiment was designed to verify the feasibility of the proposed method.Experimental results showed that the proposed method could achieve high combustion efficiency,steady operation and low NO_x emission.The maximum reduction efficiency of primary NO in kiln gas reached 91.4%while the lowest NO_x emission was 145 mg/m~3 (@10%O_2) during the experiment.The effects of key parameters on NO_x emission and primary NO_x reduction efficiency were comprehensively investigated.It was found that primary and secondary air ratios determined the oxygen content in the flue gas and the reaction temperature,which multiply affected the fuel-NO_x formation and activity of reductants.Increasing the length of the reducing zone could not only enhance the primary NO_x reduction efficiency,but also lower the combustion efficiency.In addition,cement raw material could greatly accelerate the formation of fuel-NO_x while its catalytic action on NO_(x )reduction was limited. 相似文献