低排放分级燃烧器中CH4燃烧特性

烟气回流是实现柔和燃烧的手段,为精确控制回流比例,建立了分级燃烧器,实验研究了回流比例、当量比对CH4柔和燃烧火焰形态和NO、CO排放的影响。当量比为0.8,回流比例为0.6～0.7时实现柔和燃烧,反应区分散不分层,烟气中NO和CO体积分数分别小于1.2×10-5和4×10-5;回流比例过小时发生扩散燃烧,过大时燃烧不稳定;NO排放主要在烟气发生区产生。回流比例为0.6、当量比为0.6～0.8时,射流和主流有效掺混并伴有火焰抬升,实现柔和燃烧;相同当量比时,分级燃烧的NO排放较旋流扩散低,当量比0.8时,分级燃烧相对旋流扩散减排NO达44%。     

扩散燃烧流场测量的PIV应用研究

为了研究燃烧火焰结构及其内部流动状况，考察其在燃烧喷嘴前回流区冷态试验模拟中和实际燃烧状况下的差别，利用二维粒子成像速度仪(PIV)对带钝体燃烧器中的丙烷／空气扩散燃烧的流场进行了测量，实现了火焰内部流动的可视化．通过对热态流场与相应冷态流场的对比分析表明，在复杂燃烧中冷态流场模拟与实际燃烧过程中的流动存在较大差别，实际燃烧中的流动状况变得紊乱，回流区在长度和宽度上都明显增大．     

不同进口条件对微小尺度驻涡燃烧室性能的影响

为研究进气参数对含导流片及钝体的微小尺驻涡燃烧室性能的影响,对不同进口温度、进口速度以及当量比等参数影响下的燃烧流动进行了研究。结果表明:进气参数的变化对钝体回流区范围均有影响,当量比的增大使回流区范围减小,速度和温度的增大使回流区范围增大,但温度的影响较为明显。当量比对燃烧效率的影响较大,Φ≤1.0时,燃烧效率较高,Φ1.0时,燃烧效率迅速降低。进气速度对总压损失的影响较大,当v=50 m/s时,总压损失达到11.38%。     

一种低NOx旋流燃烧器流场特性的研究

介绍了国内某锅炉厂按引进日立-巴布科克公司技术制造的HT-NR3低NOx燃烧器的基本情况及其主要结构特点,并对这种燃烧器进行了试验研究.结果表明:该燃烧器的回流区为中间环状回流区,煤粉浓度分布为外浓内淡,与其回流区相匹配,具有良好的着火及燃烧特性.实际运行表明,该燃烧系统具有很好的低NOx特性,可以满足国内燃煤锅炉的低NOx排放要求.     

油罐火灾燃烧速度的实验研究

燃烧速度是油罐火灾中决定火焰温度和辐射热的重要参量，其变化规律也决定着火灾中灭火预案及战术的制定．通过对直径为1．0m、1．5m和2．7m的汽油和柴油储罐火灾的燃烧实验，获得了油品的瞬时燃烧速度和平均燃烧速度的变化规律．研究得出，油品的种类和油罐直径对平均燃烧速度影响较大，另外随着油初温的升高、风速的加大以及升高油位，都会增大油品的燃烧速度．在此基础上，拟合了相应条件下的实验关联式，并简要分析了各种影响因素的燃烧学机理．     

大气温度对某型燃气轮机燃烧稳定性和 NOx排放影响的数值研究

为了对比扩散和预混两种不同燃烧模式下大气温度对燃气轮机燃烧稳定性和NO_x排放的影响规律,针对某重型燃气轮机燃烧室,对多旋流喷嘴燃烧室的燃烧稳定性和NO_x排放进行了数值研究。结果表明:对于扩散燃烧,大气温度升高,燃烧室内高频脉动增强,燃烧稳定性变差;对于预混燃烧,大气温度升高,有利于提高燃烧的稳定性;在扩散燃烧模式下燃烧室燃料喷嘴下游回流区的温度最高,NO_x生成量最大;预混燃烧下燃烧室头部温度分布较均匀,燃烧室NO_x生成主要集中在驻涡回流区和燃烧室中下游位置,燃料喷嘴下游回流区NO_x生成量很小;随着大气温度的升高,扩散燃烧和预混燃烧下燃烧室内NO_x的生成量均增加。研究结果可为指导燃气轮机运行提供参考。     

预热空气与高炉煤气的扩散燃烧混合特性研究

针对某钢铁企业高炉煤气回收水冷系统的特点,分析研究了低热值高炉煤气与不同预热温度空气的同轴扩散气流在绝热炉膛内混合和燃烧的特点,据此建立k-ε双方程燃烧数学模型,并对其燃烧混合特性进行模拟研究.研究结果表明:回流中心区的位置位于轴向0.1～0.22 m,但随着空气预热温度的升高,缩小到0.12～0.2 m,回流负压也有...     

火焰稳定和煤粉浓度连续可调的研究：气体动力特性连续可调

为了适应电站锅炉燃煤种类多变和低负荷燃烧稳定的要求，提出了一种新的浓淡偏差的燃烧方式——煤粉浓度连续可调的叶片式燃烧器。本文重点叙述了叶片角度从α＝０°～６０°变化时，气流平均速度分布从比较均匀，变成有较大的速度差，从而形成双峰式的速度分布，并形成一定的回流区；不仅如此，气流的湍流参数，如湍动能，也随着叶片角的增大，几乎成直线地增加，特别是α＝０°～３５°时比较明显。这些参数的变化，对于强化煤粉气流的热质交换和火焰稳定都是非常有利的。     

二次风旋流强度可调范围的数值模拟研究

利用Ansys12．0软件对实际电站锅炉的炉内流场进行了数值模拟,分别研究了内、外二次风旋流强度对炉内流场的影响．结果表明：随着旋流强度的增加,中心回流区开始远离燃烧器出口轴线位置,回流区长度增加,回流区面积增大,当旋流强度大于某一数值时,将不能形成较好的中心回流区,易发生飞边现象;外二次风旋流强度对回流区的影响较大,但调节范围却较小,而内二次风旋流强度的可调范围较大;内二次风和外二次风旋流强度的可调范围分别为0．58～2．74和0．58～1．00．     

乙醇微型燃烧室燃烧特性的数值模拟研究

为了解决化石燃料储备不足与环境污染问题，生物质燃料作为石油替代能源得到大力提倡，如何合理地将化石燃料替换为生物质燃料且维持设备正常运行成为工程上亟待解决的问题。本文采用CFD软件研究了车载5 kW生物乙醇微型燃烧室的燃烧特性，对比分析了不同功率（0.5~5 kW）和出口温度（840~960 K）时的回流区长度与宽度、回流量、出口温度分布系数（OTDF）、出口NO体积分数等特征参数。结果表明：随着出口温度升高，回流区长度逐渐缩短，回流量减少，出口温度均匀性逐渐变差，出口NO体积分数明显增加；随着燃烧室功率增大，回流区长度变长，回流量增加，OTDF先增大后减小，NO体积分数随着功率的降低而显著升高，最大值出现在1 kW时，达到满负荷时的7倍。因此，为了实现稳定燃烧和减少污染物排放，该乙醇微型燃烧室应在较高的空燃比（即较低的出口温度）和功率下运行。     

_水包油_型乳化重油燃烧与排放的实验研究

实验研究了含水30%"水包油"型乳化重油的燃烧与污染物排放特性。燃烧在一维卧式炉上进行,采用专门针对乳化油设计的喷嘴、燃烧器和乳化油加热系统。实验过程中观察了喷嘴雾化和火焰状态,并测量了炉膛内不同剖面的温度分布、氧气浓度分布和NO分布。"水包油"型乳化重油的燃烧实验表明,此类乳化重油完全可以在工业设备上代替柴油使用,对缓解我国的能源形势紧张和环境保护具有重要意义。     

一次风率及循环废气率变化对燃油锅炉运行中氮氧化物生成的影响

研究空气分级和废气循环燃烧等方式对油燃烧中NOx 生成的影响。实验发现 :分级燃烧对于燃料氮的转化有抑制作用 ,而且对含氮量较高的油燃料效果较明显 ,不论燃烧器功率如何 ,降低一次风率总使得NOx 的生成量减少 ;当一次风率占总过量空气系数的 50 %左右时 ,燃料氮的转化率存在一个最小值 ,而后随着一次风率的提高而增大并趋于一常数 ;增加废气循环率能降低油燃烧中NOx 的生成量 ,而且对于含氮量较低的油效果较明显 ,随着废气循环率增加 ,NOx 生成量的降幅趋缓并带来火焰稳定问题 ,因此存在有一个最佳废气循环率 ;废气循环燃烧会增大燃料氮的转化率 ,而且在一次风率较小情况下表现明显     

突扩燃烧室内回流区长度研究

讨论了热过程对圆管突扩回流流动的影响,数值计算的结果表明：圆管突扩流动中,加热使流动方向上的逆压梯度降低,从而使回流区长度减小,在此基础上,用均匀热源的方法来模拟热态的燃烧过程,对层流、湍流状况下分别拟合出回流区长度与燃烧温度的近似关系,以便能通过冷态的数据预测热态回流区长度     

几何结构对贫油直喷燃烧室流场特性影响的研究

基于现有单点贫油直喷燃烧室,采用数值模拟方法研究了头部几何角度对燃烧室流场特性的影响。分别对比了冷态与燃烧态条件下不同头部几何角对燃烧室轴向速度分布、燃烧效率、总压损失等特性的影响。研究表明:在所研究的几何角度范围内,冷态下头部几何角度对回流区的长度影响很小,对回流区内轴向速度分布具有较大影响。燃烧态下随着头部几何角度的增加,回流区轴向尺寸逐渐增加,中轴线上轴向速度值逐渐降低。燃烧室的出口平均温度、燃烧效率、总压恢复系数基本保持不变,60°结构产生的NO_x生成量最低,30°结构产生的NO_x生成量最高。     

初始条件对燃气轮机DLE燃烧室性能影响研究

以单头部中心分级旋流干式低排放(Dry Low Emission, DLE)燃烧室为研究对象,以天然气为燃料,针对不同的全局当量比、进口温度、进口压力条件开展试验测试和数值模拟,研究燃烧室的燃烧性能以及污染物排放的变化规律。研究发现：随全局当量比增大,中心回流区长度略有增大、宽度变窄、回流速度增大,燃料量的增加使得高温区面积明显扩大,燃烧室出口温升明显增大,出口温度分布系数变化不大,燃烧室出口CO和NO_x排放摩尔分数明显增大;随进口温度的增大,中心回流区长度先明显增大再减小、宽度变窄、回流速度先增大再减小,进口空气温度的升高使得反应速率加快从而导致燃烧室出口温度升高,但温升、出口温度分布系数变化不大,CO和NO_x排放摩尔分数增大;随进口压力的增大,中心回流区长度、宽度略有增大,回流速度增大,燃烧室内部和燃烧室出口温度无明显变化,出口温度分布系数减小,CO和NO_x排放摩尔分数受影响较小。     

HS-A柴油机燃料油技术研究

在柴油机燃料油各种节油和替代技术中，HS—A柴油机燃料油可以替代0号柴油应用在高、中、低速柴油机和各种柴油燃烧器上。文中介绍了该油的研制过程，如残炭值的变化，以及试验情况。该油料合成工艺简单，投资及合成成本低。     

Mixing and Recirculation Characteristics of A double COncentric Burner with Bluff—Body

The concentric bluff-body jet burner is widely used in industrial combustion systems. This kind of burner often generates a considerably complex recirculation zone behind the bluff body. As a result, the fuel often remains in the recirculation zone, achieving stability of flame. This study investigates, by means of experiments, the variations of the aerodynamics as the fluid is injected into a combustion chamber through a double concentric burner with a bluff-body. The observation and measurement of the aerodynamics in our experiment are conducted under a cold flow. The controlled parameters in our experiment are: variations in the blockage ratio of the center bluff body, the cone angle of the bluff body, and the velocity ratio (U _s/U_p) of the secondary jet and primary jet; the injection of helium bubbles into the primary and secondary jets to observe the recirculation zone behind the bluff body; using Tufts for observing the characteristics of corner recirculation zone in a combustion chamber, measuring the average velocity of each point within the aerodynamics by the 5-hole pitot tube; measuring the distribution of static pressure of the combustion chamber walls with a static pressure tap.     

Studies of the effect of a coal concentrator on NO formation in swirling coal combustion

To develop low-pollution burners, the effect of a coal concentrator on NO formation in swirling coal combustion is studied using both numerical simulation and experiments. The isothermal gas–particle two-phase velocities and particle concentration in a cold model of swirl burners with and without coal concentrators were measured using the phase Doppler particle anemometer (PDPA). A full two-fluid model of reacting gas–particle flows and coal combustion with an algebraic unified second-order moment (AUSM) turbulence-chemistry model for the turbulent reaction rate of NO formation are used to simulate swirling coal combustion and NO formation with different coal concentrators. The results give the turbulent kinetic energy, particle concentration, temperature and NO concentration in cases of with and without coal concentrators. The predicted results for cold two-phase flows are in good agreement with the PDPA measurement results, showing that the coal concentrator increases the turbulence and particle concentration in the recirculation zone. The combustion modeling results indicate that although the coal concentrator increases the turbulence and combustion temperature, but still can remarkably reduce the NO formation due to creating high coal concentration in the recirculation zone.     

Experimental investigation on the kinetics of biomass combustion in vertical tube reactor

The paper presents results of experimental investigation performed in order to examine kinetics of loose biomass combustion in vertical tube reactor. The investigation conducted included continuous measurement of the fuel mass loss rate, with two biomass combustion models (piston and batch model) proposed, each relying on appropriate theoretical postulates. Results obtained indicated that piston combustion model had shown better agreement between theoretical and experimental data and was therefore used to further analyse effects of excess-air on the combustion kinetics, as well as associated effects of flue gas recirculation. Recirculation of cold flue gases is used to lower peak temperature inside the furnace, as well as to reduce a zone where ash melting problems may potentially occur. During the investigation performed, effects of flue gas recirculation on the combustion process were simulated by simultaneously injecting nitrogen and air flows into the furnace. This was deemed appropriate to simulate real-life conditions prevailing in the furnace with gas recirculation. Experiments were conducted on specially designed and constructed apparatus that enabled kinetic parameters to be determined for the combustion of different types of biomass. Results obtained have indicated that quantity of air affects kinetics of biomass combustion and that increased recirculation leads to reduced biomass reaction rate. The same conclusion was reached based on the results of experiments conducted with two different types of agro-biomass, namely wheat straw and corn stalks, which are most commonly used for energy generation. Results achieved are deemed particularly important when it comes to design of new plants that utilize cigarette type combustion system, but also for development of numerical models used to simulate combustion of biomass bales, with special emphasis placed on the impact of recirculation gases on the combustion kinetics.     

Thermal management and catalytic combustion stability characteristics of premixed methane/air in heat recirculation meso‐combustors

In order to illuminate heat recirculation effect on catalytic combustion stability and further improve energy conversion efficiency in meso‐combustor, the catalytic combustion characteristics of the combustor with/without preheating channels are numerically studied at steady conditions. It is found that methane conversion rate and combustion efficiency increases by 2% to 3% and approximately 9% in the heat recirculation meso‐combustor, indicating that heat recirculation effect facilitates more complete combustion of methane and medium components. Preheating channels show positive effects on improving combustion stability in the heat recirculation meso‐combustor. On one hand, preheating channels facilitate heat recirculation effect, and heat recirculation rate exceeds 10% for all cases and reaches 31.8% with an inlet velocity of 0.5 m/s, leading to significant increment of methane‐specific enthalpy at the preheating channel outlet. On the other hand, Rh(s)/O(s) ratios of catalytic surface and catalytic surface temperature in main reaction zone are enlarged by the preheating channels, facilitating methane adsorption at catalytic surface. Specially, most of fuels are consumed in a shorter distance with higher methane conversion speed, which brings benefits to promote combustion efficiency and may be helpful to inhibit the combustion instability in heat recirculation meso‐combustors.