一种新型平焰烧嘴在空气和氧气助燃条件下燃烧特性对比研究

为了研究新型平焰烧嘴的纯氧燃烧特性,通过空气与纯氧助燃对比实验,对新型平焰烧嘴在不同工况下的火焰分布、火焰面上方50 mm处温度分布及CO体积分数分布进行分析。助燃管至烧嘴中心轴线距离变化范围为0～60 mm,燃气流量为0.5 m~3/h,空气(氧气)过量系数为1.06。研究表明:空气(氧气)旋流造成的负压区使回流的阻力减小,高温炉气回流到焰心挤压在旋流的中心,促进气流附壁,使燃烧稳定;在相同的助燃管距离下,纯氧助燃旋流强度总低于空气助燃,燃烧区域较小,燃烧温度提高,CO排放量低于空气助燃;燃气和助燃气混合流股的旋流强度与CO峰值体积分数成反比,随着助燃管至烧嘴中心轴线距离增大,两种助燃条件的旋流强度随之增加,燃烧范围扩大,火焰峰值温度和CO体积分数总体降低;当助燃管距离为60 mm时,纯氧助燃旋流强度和燃烧面积达到最大,火焰峰值温度和CO体积分数降至最低,混合程度最好,燃烧效果最佳。     

高温低热值煤气燃烧器结构优化的实验研究

对一种高温低热值煤气燃烧器进行了改进和优化设计,在低热值煤气管内增加了中心管,并将原燃烧器空气管的渐缩喷口改成渐扩喷口,去掉煤气管的渐缩喷口。对比优化前后燃烧器的热态实验数据,结果表明:改进后燃烧器能持续稳定燃烧以CH4和N2配制的热值为3.9 MJ/m3和以CO和N2配制的热值为4.0 MJ/m3且预热温度均为660℃的低热值煤气,火焰稳定不脱火;而原燃烧器仅能燃烧热值大于16.31 MJ/m3、预热温度为660℃的低热值煤气,且火焰不稳定根部出现严重的脱火现象。     

生物质燃油燃烧CO和NO排放特性试验研究

以小桐子油、地沟油、小桐子生物柴油、地沟油生物柴油和0号柴油为燃油,研究了其在炉窑内的燃烧排放特性。结果表明:随着油压的增大,燃烧生物质燃油和柴油时,烟气中CO浓度逐渐降低,NO浓度逐渐升高;随着过量空气系数的增大,烟气中CO浓度呈现先减小后增大的趋势,NO浓度变化趋势则相反;在最佳过量空气系数下,烟气中CO浓度最低、NO浓度最高,生物柴油能明显降低CO的浓度,从最高970 mg/m~3 降低到181 mg/m~3 ,但提高了NO的浓度;随着生物柴油混合比例的增大,烟气中CO的浓度逐渐降低。     

O_2/CO_2/水蒸气气氛下煤的燃烧对石灰石分解行为的影响

钙基CO_2吸收剂再生过程中,石灰石的分解需要大量能量.本文提出用煤的燃烧为石灰石分解提供能量,并研究了O_2/CO_2/水蒸气气氛下煤的燃烧对石灰石分解行为的影响.实验结果表明,过量氧气系数增大可以抑制CO和H_2的生成,促进硫化反应,从而降低SO_2的排放,然而也会促进NO的排放.煤的燃烧会使分解产物CaO活性降低,但水蒸气的添加又提升了产物的活性.水蒸气的添加还会促进硫化反应,使SO_2排放得到控制.     

主动预燃室式直喷汽油机稀薄燃烧性能研究

为明晰不同点火方式对汽油机稀薄燃烧特性的影响规律,在一款排量为0.5L的研究型单缸机上试验研究了传统火花塞和主动预燃室两种不同点火方式下发动机燃烧及排放特性,探索主动预燃室拓展稀薄燃烧极限的多种影响因素。研究结果表明,稀薄燃烧可有效降低油耗,提高发动机热效率。传统点火线圈的稀燃极限处于过量空气系数1.5附近,最高指示热效率为45.0%,而采用主动预燃室系统后,稀燃极限可进一步拓展,过量空气系数可达2.0,指示热效率提升至46.5%,氮氧化物排放比采用传统火花塞点火技术时降低约88%;主动预燃室匹配高压缩比14.80的燃烧系统,可进一步拓展稀燃极限至过量空气系数2.1,指示热效率可达48.0%,氮氧化物排放继续降低,在过量空气系数采用2.1时NOx排放最低可达58×10-6。     

循环流化床锅炉炉膛低氧燃烧加尾部补燃降低NOx排放的试验研究

在1台70 MW循环流化床工业热水锅炉上,应用炉膛低氧燃烧加尾部烟道补燃技术,降低锅炉的NO_x原始排放浓度。通过降低炉膛内过量空气系数,使炉膛和旋风分离器内呈低氧燃烧状态。由于高温烟气中有残炭和CO的存在,抑制了NO_x生成,同时能够促进NO_x向N_2转化,从而降低了高温烟气中NO_x含量。从旋风分离器中心筒喷入补燃风,可将由于炉膛低氧而未完全燃烧的残炭和CO燃尽,保证了锅炉燃烧效率。采用炉膛低氧燃烧加尾部补燃技术,锅炉的NO_x原始排放浓度从393 mg/m~3降低至115 mg/m~3(@6%O_2),CO的排放浓度控制在4×10~(-6)。     

600MW超临界对冲燃烧锅炉CO和NOx排放特性的研究

采用现场试验研究和数值模拟的方法对布置前后墙对冲燃烧器的某600Mw超临界锅炉CO和NO,的排放特性进行了研究．结果表明：锅炉尾部烟气中CO质量浓度为500～2500mg／m3,当主燃烧区过量空气系数a,为0．86～0．90时,高于该锅炉低NO。排放的设计过量空气系数（0．80）,对应的燃尽风占二次风的比例约为27％～32％,NOx排放质量浓度出现拐点;锅炉的NOx排放特性与HT—NR3燃烧器的低NOx设计有关,并与该锅炉的CO排放特性呈负相关关系;在负荷为600Mw和总风量一定的工况下,当燃尽风比例从32％提高至49％时,CO排放质量浓度显著下降,飞灰可燃物浓度降低,氧气量对CO和NOx排放的影响明显减弱,但NOx排放质量浓度升高,主燃烧区侧墙高温腐蚀的风险增大．     

旋流对高温空气燃烧影响的模拟研究

以工业炉的高温空气燃烧技术应用为背景,对一个同心式轴向旋流高温空气燃烧器单烧嘴燃烧室内的高温空气燃烧特性进行了模拟研究。湍流输运方程采用RSM模型,气相燃烧模型采用函数的PDF燃烧模型,辐射换热过程采用离散坐标法模拟,NOx模型为热力型。以天然气为燃料,在预热空气温度为1 273 K,空气含氧量为8%。燃烧总过量空气系数为1.1的条件下,进行了数值模拟计算,讨论了旋流角度和燃烧器的螺旋伸展长度等参数对NOx排放、局部温度、氧浓度和CO浓度分布等的影响。结果表明,旋流燃烧器能进一步降低NO排放,使燃烧更加完全。当螺旋肋片伸展因子R=2,燃料/空气速度比a=1.09,旋流角度θ=180°时,NO排放浓度最小,出口NO的摩尔分数为12.9×10-6,出口CO的摩尔分数为29×10-6。而当旋流角度θ=0°时(直射流),出口NO的摩尔分数为31.7×10-6,出口CO的摩尔分数为372×10-6。     

燃烧参数影响高温空气燃烧特性的数值分析

高温空气燃烧技术具有高效节能和低NOx排放等多重优越性，是一种新型燃烧技术。为了深入研究高温空气燃烧机理和低氮氧化物排放特性，将湍流N—S方程与扩散燃烧模型和热力型NO生成模型相结合，研究了低氧浓度条件下，燃烧参数，如燃气供应量，过量空气系数，进口空气预热温度以及进口空气氧含量对燃烧的影响，为发展高温空气燃烧技术提供了理论依据。     

甜高粱茎秆发酵后残渣的燃烧和NOx排放特性研究

利用TG-DTG-DTA联用方法对不同升温速率下的甜高粱茎秆发酵后残渣进行燃烧特性试验,并在燃烧试验平台上开展未完全燃烧物测试,研究颗粒化利用的可行性。试验表明,甜高粱茎秆发酵后残渣燃烧主要集中在挥发分燃烧阶段;空气气氛下,升温速率在40℃/min条件下,燃烧效果最好,挥发分释放特性和综合燃烧特性指数最大。甜高粱茎秆发酵残渣的颗粒化燃烧试验中,过量空气系数在1.7和2.2之间时,NO_x最大排放浓度为348.4 mg/m~3;当过量空气系数小于1.95时,NO_x小于300 mg/m3。建议使用高效燃烧器使甜高粱酵渣颗粒在过量空气系数小于1.72的条件下燃烧,降低NO_x排放。     

燃煤工业锅炉使用布朗气复燃法的研究

利用布朗气燃烧速度快、着火范围宽、最低点火能量低等特点,首次提出将布朗气复合燃料燃烧法应用于燃煤工业锅炉,使锅炉的燃烧状态发生明显变化,降低尾气中CO的含量,使得锅炉在相同排放水平条件下,可以采用更低的过量空气系数,提高燃烧效率.     

反馈系统在池炉燃气热值调节中的应用研究

为了提高超白玻璃的生产质量并降低能耗,要求对玻璃炉窑燃用的天然气的热值进行精确控制。利用对空气流加热的方法在线测量燃气的热值,通过给燃气加入空气调整燃气热值,设计了燃气热值反馈调节系统。系统采用前馈和双闭环的调整方法,有效地保障了池炉燃气供应系统良好的热值调节质量。试验表明:反馈控制系统控制精度为1.0%,重复性为0.3%,响应时间为6 s,采用热值反馈系统后燃气热值波动范围由原来的40.9~42.8MJ/m3减小为34.5~34.7MJ/m3,满足了玻璃熔化质量的要求,提高了窑炉燃烧效率。     

Development of high intensity CDC combustor for gas turbine engines

Colorless distributed combustion (CDC) has been demonstrated to provide ultra-low emission of NOx and CO, improved pattern factor and reduced combustion noise in high intensity gas turbine combustors. The key feature to achieve CDC is the controlled flow distribution, reduce ignition delay, and high speed injection of air and fuel jets and their controlled mixing to promote distributed reaction zone in the entire combustion volume without any flame stabilizer. Large gas recirculation and high turbulent mixing rates are desirable to achieve distributed reactions thus avoiding hot spot zones in the flame. The high temperature air combustion (HiTAC) technology has been successfully demonstrated in industrial furnaces which inherently possess low heat release intensity. However, gas turbine combustors operate at high heat release intensity and this result in many challenges for combustor design, which include lower residence time, high flow velocity and difficulty to contain the flame within a given volume. The focus here is on colorless distributed combustion for stationary gas turbine applications. In the first part of investigation effect of fuel injection diameter and air injection diameter is investigated in detail to elucidate the effect fuel/air mixing and gas recirculation on characteristics of CDC at relatively lower heat release intensity of 5 MW/m³ atm. Based on favorable conditions at lower heat release intensity the effect of confinement size (reduction in combustor volume at same heat load) is investigated to examine heat release intensity up to 40 MW/m³ atm. Three confinement sizes with same length and different diameters resulting in heat release intensity of 20 MW/m³ atm, 30 MW/m³ atm and 40 MW/m³ atm have been investigated. Both non-premixed and premixed modes were examined for the range of heat release intensities. The heat load for the combustor was 25 kW with methane fuel. The air and fuel injection temperature was at normal 300 K. The combustor was operated at 1 atm pressure. The results were evaluated for flow field, fuel/air mixing and gas recirculation from numerical simulations and global flame images, and emissions of NO, CO from experiments. It was observed that the larger air injection diameter resulted in significantly higher levels of NO and CO whereas increase in fuel injection diameter had minimal effect on the NO and resulted in small increase of CO emissions. Increase in heat release intensity had minimal effect on NO emissions, however it resulted in significantly higher CO emissions. The premixed combustion mode resulted in ultra-low NO levels (<1 ppm) and NO emission as low as 5 ppm was obtained with the non-premixed flame mode.     

Experimental study on combustion and emission characteristics of a hydrogen-enriched compressed natural gas engine under idling condition

This paper investigates the effect of various hydrogen ratios in HCNG (hydrogen enriched compressed natural gas) fuels on combustion and emission characteristics of a turbocharged spark ignition natural gas engine at idling conditions. The experiments were taken at hydrogen fractions of 0%, 30%, 55% and 75% by volume and were conducted under various operating conditions including different excess air ratio λ and spark timing θ_ig. It is found that under various λ and θ_ig, the addition of hydrogen can significantly reduce CH₄ emission and CO emission, although NO_x emission increased with the hydrogen addition, it was relatively low at idle conditions compared to other emissions. Meanwhile the addition of hydrogen can significantly reduce COV_imep (coefficient of variation of the indicated mean effective pressure), extend the lean burn limit, decrease the combustion duration, achieve higher thermal efficiency and reduce fuel consumption.     

Experimental study on Egyptian biomass combustion in circulating fluidized bed

The present study investigates the combustion of four kinds of biomass in a circulating fluidized bed. The combustion chamber is a steel cylinder with 145 mm inner diameter and 2 m height. Tests were conducted on wheat straw, sawdust-wood, cottonseed burs, and corncobs. Excess air was varied for each fuel. Temperature, heat flux and gas emissions were measured along the combustion chamber and at the chimney inlet. Results showed that sawdust-wood produces the highest values of CO emissions (about 3000 mg/Nm³). On the other hand, cottonseed burs produce the lowest values of CO emissions (about 250 mg/Nm³). The SO₂ emissions were very low in all tests (less than 20 mg/Nm³). The lowest emission value occurred at an excess air ratio (EA) of 1.24 except for cottonseed burs where it was 1.4.     

A comparative study on effects of homogeneous or stratified hydrogen on combustion and emissions of a gasoline/hydrogen SI engine

A comparative study on effects of homogeneous or stratified hydrogen on combustion and emissions was presented for a gasoline/hydrogen SI engine. Three kinds of injection modes (gasoline, gasoline plus homogeneous hydrogen and gasoline plus stratified hydrogen) and five excess air ratios were applied at low speed and low load on a dual fuel SI engine with hydrogen direct injection (HDI) and gasoline port injection. The results showed that, with the increase of excess air ratio, the brake thermal efficiency increases firstly then decreases and reaches the highest when the excess air ratio is 1.1. In comparison with pure gasoline, hydrogen addition can make the ignition stable and speed up combustion rate to improve the brake thermal efficiency especially under lean burn condition. Furthermore, it can reduce the CO and HC emissions because of more complete combustion, but produce more NO_X emissions due to the higher combustion temperature. Since, in the gasoline plus stratified hydrogen mode, the hydrogen concentration near the sparking plug is denser than that of homogeneous hydrogen, the ignition is more stable and faster, which further speed up the combustion rate and improve the brake thermal efficiency. In the gasoline plus stratified hydrogen mode, the brake thermal efficiency increases by 0.55%, the flame development duration decreases by 1.0°CA, rapid combustion duration decreases by 1.3°CA and the coefficient of variation (COV) decreases by 9.8% on average than that of homogeneous hydrogen. However, in the gasoline plus stratified hydrogen mode, due to the denser hydrogen concentration near the sparking plug and leaner hydrogen concentration near the wall, the combustion temperature and the wall quenching distance increase, which make the NO_X and HC emissions increase by 14.3% and 12.8% on average than that of homogeneous hydrogen.     

Distributed swirl combustion for gas turbine application

Colorless distributed combustion (CDC) has been shown to provide significant improvement in gas turbine combustor performance. Colorless distributed combustion with swirl is investigated here to develop ultra-low emissions of NO and CO, and significantly improved pattern factor. Experimental investigations have been performed using a cylindrical geometry combustor with swirling air injection and axial hot gas exit stream from the combustor. Air was injected tangentially to impart swirl to the flow inside the combustor. The results obtained from the combustor have demonstrated very low levels of NO (∼3 PPM) and CO (∼70 PPM) emissions at an equivalence ratio of 0.7 and a high heat release intensity of 36 MW/m³-atm under non-premixed combustion. To further simulate gas turbine operating conditions, inlet air to the combustor was preheated to 600 K temperature and the combustor operated at 2 atm pressure. Results showed very low levels of CO (∼10 PPM) but the NO increased somewhat to ∼10 PPM at an equivalence ratio of 0.5 and heat release intensity of 22.5 MW/m³-atm under non-premixed combustion conditions. For premixed combustion, the combustor demonstrated low levels of both NO (5 PPM) and CO (8 PPM) at an equivalence ratio of 0.6 and a heat release intensity of 27 MW/m³-atm. Results are reported at different equivalence ratios on the emission of NO and CO, lean stability limit and OH^* chemiluminescence. These results suggest that further performance improvement can be achieved with improved fuel mixture preparation prior to the ignition of fuel at higher operational pressures using swirling combustor design for our quest to develop ultra low emission high intensity combustor for gas turbine application.     

天然气锅炉NOx及CO排放控制试验研究

为了响应政府业及民用天然气锅炉达到超低氮排放,要求绝大多数天然气锅炉采用低氮燃烧器+烟气再循环系统的技术路线,实施后普遍出现NO_x、CO含量偏高、炉膛振动较大等问题。借助116 MW天然气锅炉进行试验研究,研究了燃烧器燃料配比、燃烧火焰长度、助燃空气氧含量三个因素对NO_x及CO的影响,并对投入烟气再循环前后炉膛振动情况进行了检测。试验表明:燃烧器燃料内外配比对NO_x、CO生成影响较大,两者呈现相反趋势变化;燃烧火焰长度对NO_x生成影响较大,对CO含量影响较小;助燃空气氧含量对NO_x、CO生成以及锅炉振动影响较大。三种影响因素相比,助燃空气氧含量影响更为突出。     

Comparison of combustion characteristics of petroleum coke and coal in one-dimensional furnace

The effect of primary air fraction f₁, outer secondary air swirl strength and excess oxygen coefficient on the combustion characteristics of petroleum coke, Hejin lean coal and Shenmu soft coal are researched on a one-dimensional furnace using a dual channel swirl burner. The results show that with the increase in primary air fraction f₁, the NO_x emission concentrations of both Hejin lean coal and petroleum coke increase, and the combustion worsens in the earlier stage, but the burn-out rate of Shenmu soft coal is improved. The NO_x emission concentration obtains a minimum value with an increase in f₁. The ignition and burn-out rate of petroleum coke and Shenmu soft coal are optimal when Ω_dl is minimum and Ω_dl=0.87, respectively. However, both the NO_x emission concentration of petroleum coke and Shenmu soft coal are minimum when Ω_dl=1.08. The increase in excess oxygen coefficient delays the ignition of petroleum coke, worsens the combustion condition and increases the NO_x emission concentration, but it greatly decreases the NO_x emission concentration of Shenmu soft coal.     

下吸式生物质气化炉热力学平衡模型研究

建立下吸式生物质气化炉热力学平衡模型,该模型包括焦炭、焦油和气体,并用已公布的实验数据对模型进行验证,均方根（RMS）在1.304~3.814之间,结果表明该模型的预测值与实验数据吻合较好,可认为模型可靠。然后模拟棉秆在下吸式生物质气化炉中以空气和富氧气体2种气化氛围下,不同操作参数(当量比、预热温度和气化炉反应温度)下对棉秆气化的气体组分、热值和产率的影响。模拟结果表明：富氧气体为气化剂时,当量比从0.20增至0.35时,气体中N₂含量比空气显著下降,达10%以上,同时发现能提高气体中H₂和CO的含量和热值,热值比空气提高约20%。预热温度对气化成分变化影响有限,随预热温度从30 ℃变化到130 ℃,气体的平均热值从空气的5.2 MJ/m³提高到富氧气体的7.0 MJ/m³。随气化炉内反应温度从750 ℃升至1250 ℃,空气和富氧气体2种气化剂下的H₂和CO分别从20.94%、26.84%和21.77%、28.67%下降到4.06%、9.12%和10.49%、21.60%,导致气体的热值降低。