基于数值模拟的旋流燃烧室热利用率分析

以某种新型的带直流孔的旋流器为研究对象,运用商用CFD软件Fluent对旋流燃烧器冷态/热态流场进行模拟,探索新型的带直流孔的旋流器对燃烧室性能的影响。对传统旋流燃烧室和新型旋流燃烧室进行热平衡分析和比较,并在此基础上研究旋流器结构对燃烧室整体热利用率的影响。热力学分析的结果表明带直流孔的旋流燃烧室的燃油燃烧效率比传统的旋流燃烧室要高,为证明带直流孔的旋流器的优势提供了很好的理论支撑。     

旋流燃烧器螺旋伸展长度对高温空气燃烧特性的影响

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数值研究.燃烧室尺寸为600 mm×600 mm×1000 mm,燃烧器烧嘴由位于中心的圆形直射流燃气喷口和其外围的同心轴向旋流高温预热空气射流喷口构成.湍流输运方程采用RSM模型,气相燃烧模型采用β函数的PD...     

旋流强度对F级燃气轮机燃烧稳定性影响分析

旋流器是目前燃烧室中常用的稳定火焰的结构,主要通过气体经过旋流器后在下游形成的回流区来稳定火焰。一般采用旋流数表征旋流器的旋流强度。旋流数一方面会影响空气和燃料的掺混,另一方面会影响回流区的尺寸,从而对火焰的长度和稳定性产生影响。针对某重型燃气轮机的燃烧器,采用数值模拟的方法分析了旋流数变化对热态温度场的影响,同时采用三维有限元方法分析了旋流数对燃烧稳定性的影响。结果表明:旋流数增加,会使得火焰更加紧凑,长度缩短,同时使得燃烧室二阶周向模态稳定性恶化,不稳定的风险增加;降低旋流数会使得火焰长度增加,轴向模态稳定性恶化。该研究结果可为类似机组的相关设计研究提供参考和借鉴。     

MGT6100/6200燃气轮机的燃烧系统

正据《Gas Turbine World》2014~2015年年度手册报道,MGT6100/6200燃气轮机配置6个燃烧室,用法兰连接到中间整体机匣上,形成逆流式管形部件,与轴中心线呈35°角布置。燃烧室配备旋流燃烧器,以便在燃烧室出口和涡轮第一级喷嘴入口处取得均匀温度场。配套有燃料喷嘴、火焰筒、过渡段和冷却套筒,易于折卸并在现场可更换。     

有旋燃烧器的数值模拟

采用κ-ε双方程模型模拟计算了冷态燃气在轴对称渐扩燃烧器内的有旋流动状态;分析了不同旋流强度对速度分布、回流区形状大小的影响及旋流强度与出口速度之间的相互关系;预报了有旋流和无旋流下燃烧器内的流场分布;给出了燃烧器出口速度随旋流强度的变化趋势,为燃烧器设计提供理论依据。     

旋流片开槽深度对低热值煤层气燃烧特性的影响

为提高低热值煤层气的燃烧效率,设计了3种由不同开槽深度的旋流片组合成的低热值煤层气燃烧器,并进行燃烧特性实验研究,分析了不同流量下,开槽深度对燃烧室内速度、温度及火焰结构特性的影响。研究表明,火焰温度在燃烧器轴线方向分布与流速分布相似,均存在一个温度和速度峰值。相同轴向距离处,甲烷流量减小,3种旋流片的火焰中心流速和温度峰值逐渐下降,且中心流速峰值、温度峰值位置逐渐前移,但温度峰值位置始终是大于速度峰值位置。开槽深度对燃烧特性的影响主要是由于燃气通流截面改变引起的入口流速和射流直径变化导致的。采用3 mm开槽深度的旋流片时,火焰长度和直径增加最快,燃烧室内轴向速度分布和温度场最为理想,射流刚性和火焰充满度最好。     

旋流角度对燃料掺混特性影响研究

为了研究工业燃气轮机燃烧室旋流器旋流角度对燃料/空气混合均匀度以及NOx排放的影响,针对某型燃烧室的中心分级双级轴向旋流器,应用Fluent软件,选择Realizable k-ε和Species Transport模型,在燃气轮机的设计工况下对不同旋流角度回流区形态、甲烷的体积分数分布、温度场和污染物的排放进行了数值模拟。研究表明：随着内旋流角度从30°增加到50°,燃烧室内流场形成的回流区尺寸有减小的趋势,燃料的分布趋于均匀,主燃区最高温度从2 304 K降低到2 180 K, NOx排放呈先增大后减少的趋势,旋流角度为50°时NOx排放质量浓度为501.045 mg/m3。     

中心分级燃烧室旋流角变化对燃烧特性的影响

实验研究了一种中心分级燃烧室值班级旋流角变化对燃烧性能的影响。采用了单头部单管式燃烧室,值班级一级旋流器旋流数分别为0. 63、0. 72和0. 93,实验研究了采用不同旋流数时燃烧室的点火、慢车贫油熄火、污染物排放和燃烧效率等燃烧特性。实验结果表明:旋流数变化对燃烧室的点火、慢车贫油熄火、污染物排放及燃烧效率等有很大影响;旋流数及一级旋流器和二级旋流器的旋流数差值增加后燃烧室的点火和慢车贫油熄火特性得到改善。一级旋流器旋流数的增加会导致污染物排放的增加及燃烧效率的下降。     

采用旋流拱顶燃烧器的W型锅炉炉内流动特性

采用旋流燃烧器,可以强化燃烧器出口煤粉气流的着火,配合采用燃烧器内部分级燃烧方式后,也有利于降低污染气体的排放。但采用旋流燃烧器后,由于W型锅炉燃烧的特殊性,给锅炉的设计和运行带来了新的情况,如对旋流燃烧器在W型锅炉拱顶采用旋流燃烧器后炉内的空气动力特性不能很好得到掌握,不但得不到旋流燃烧器所带来的优点,还会引起很多问题。本文对采用旋流燃烧器的W型锅炉的炉内多相流动特性进行分析,并与相应的采用直流燃烧器的W型锅炉进行对比,指出在采用直流燃烧器的W型锅炉设计中常采用的参数在采用旋流燃烧器时可能会出现的问题,并提出了改进的方法。     

低NO_x旋流燃烧器的研究进展

随着分级燃烧和高浓度煤粉燃烧技术的不断进步,低NOx旋流燃烧器得到了不断发展和完善。本文对国内外典型的低NOx旋流燃烧器的研究进展做了总体回顾,总结了低NOx旋流燃烧器的发展趋势。     

生物乙醇喷雾蒸发和预混过程的数值模拟研究

基于生物乙醇燃料的贫燃预混、预蒸发燃烧技术(Lean Premixed Pervaporation,LPP),采用数值模拟方法,研究了预混室内生物乙醇雾化蒸发流场,分析了预热空气温度为500、600和1 000 K以及旋流数为0.47、0.8和1.41时的生物乙醇蒸发和气体混合特性的规律。研究表明:在LPP预混室旋流流场中,中心回流区宽度随预混室距离的增加先增大后减小,并且会受喷雾射流的影响拉伸变长,中心回流区随旋流强度的增大更贴近喷雾出口,角回流区的长度随旋流强度增大而缩短直至消失,旋流强度对液雾整体蒸发速率影响不大,但会影响液雾分布;进气温度增加会增大进气速度,提高液滴蒸发速率,缩短液雾炬长度;液滴蒸发过程存在一定程度上的压力振荡,会对LPP不稳定燃烧过程产生一定影响。     

Numerical and Experimental Studies of Mixing Enhancement and Flame Stabilization in a Meso-Scale TPV Combustor With a Porous-Medium Injector and a Heat-Regeneration Reverse Tube

Understanding the flow dynamics, chemical kinetics, and heat transfer mechanism within a miniature thermophotovoltaic (TPV) combustor is essential for the development of devices for combustion-based power microelectromechanical systems, which may have a much higher energy density than that of conventional batteries. In this study, methods for enhancing the intensity and uniformity of the combustion chamber wall (emitter) illumination through the design of combustion and thermal management of the combustor in a miniature TPV system are proposed, discussed, and demonstrated. The proposed miniature TPV system consists of a swirling combustor with the combustion chamber wall acting as the emitter, a heat-regeneration reverse tube, and mixing-enhancing porous-medium fuel injection, which improves the low nonuniform illumination or incomplete combustion problems associated with conventional miniature TPV systems. Experiments and numerical simulations are performed to analyze the details of the flame structure and flame stabilization mechanism inside the meso-scale combustor with and without a reverse tube. Results indicate that the proposed swirling combustor with a heat-regeneration reverse tube and porous medium can improve the intensity and uniformity of the combustion chamber (emitter) illumination and can increase the surface temperature of the chamber wall. From the systematic numerical and experimental analysis, suitable operational parameters for the meso-scale TPV combustor are suggested, which may be used as a guideline for meso-scale TPV combustor design.     

可控烟气回流量型低NOx燃烧器流场特性的试验研究

设计了一种预混式可控烟气回流量型低NOx燃烧器,以适应双气头多联产系统中燃料组分、成分变化时燃气轮机发电系统稳定工作的需要.在常压条件下,利用TSI热线风速仪对燃烧室内的速度分布特性进行了直接测量,并利用温度场比拟浓度场的方法,对燃烧室内气流混合特性进行了间接测量.结果表明:燃烧室内的速度分布及回流等特性可满足设计要求,气流之间的混合效果则需作进一步增强.同时,对燃烧器二次风分配器的结构提出了改进方案.     

火焰筒扩张角与旋流匹配对燃烧特性的影响

为研究旋流器流量分配对干式低排放(Dry Low Emission,DLE)燃烧室燃烧特性的影响规律,针对单头部中心分级旋流燃烧室,以天然气作为燃料,在保持旋流数不变的前提下开展两级旋流器不同空气分配比例下的试验测试和数值模拟,获得不同结构参数条件下燃烧室的综合燃烧性能以及污染物排放等变化规律。研究表明：随主燃级/预燃级旋流器流量比增大,燃烧室中心回流区变小、回流区长度变短;预燃级局部当量比的增大造成燃烧室出口CO排放增加,主燃区燃烧加剧,热力型NOx排放也增加;同时,燃烧室中心高温区域向燃烧室出口方向扩张,出口温度分布均匀性变差。     

济钢顶燃式热风炉烟气分布研究

运用CFD软件对卡鲁金热风炉和ZSD热风炉的气体燃烧和流动进行了数值模拟,得到燃烧室出口烟气速度的分布,并对卡鲁金热风炉燃烧室出口烟气的压力和温度分布进行了测试,分析了两种炉型燃烧室的结构特点。结果表明,卡鲁金热风炉燃烧室出口烟气分布的均匀程度大大高于传统的ZSD热风炉,其结构特点对ZSD热风炉的改造有很大的参考价值。     

Experimental Studies on Swirling Gas—Particle Flows in a Spouting —Cyclone Combustor

The gas and particle time-averaged velocity rand RMS fluctuation velocity of swirling gas-particle flows in a spouting-cyclone combustor were measured by a hot-ball probe and a conventional LDV system. The results show large velocity slip between the two phases both in tangential and axial directions and high nonisotropic turbulence of the two phases were also observed which is favorable to coal combustion. The particle RMS fluctuation velocity is higher than the gas RMS fluctuation velocity only in some regions of the flow field.     

Flame stability and emission characteristics of propane-fueled flat-flame miniature combustor for ultra-micro gas turbines

An engineering model of a propane-fueled miniature combustor was developed for ultra-micro gas turbines. The combustion chamber had a diameter of 20 mm, height of 4 mm, and volume of 1.26 cm³. The flat-flame burning method was applied for lean-premixed propane–air combustion. To create the stagnation flow field for a specific flat-flame formation, a flat plate was set over the porous plate in the combustion chamber. A burning experiment was performed to evaluate the combustion characteristics. The flame stability limit was sufficiently wide to include the design operation conditions of an equivalence ratio of 0.55 and air mass flow rate of 0.15 g/s, and the dominant factors affecting the limit were clarified as the heat loss and velocity balance between the burning velocity and the premixture flow velocity at the porous plate. CO, total hydrocarbons (THC), and NO_x emission characteristics were established based on the burned gas temperatures in the combustion chamber and the temperature distribution in the combustor. At an air mass flow rate of less than 0.10 g/s, CO and THC emissions were more than 1000 ppm due to large heat loss. As the air mass flow rate increased, the heat loss decreased, but CO emissions remained large due to the short residence time in the combustion chamber. NO_x emission depended mainly on the burned gas temperature in the combustion chamber as well as on the residence time. To reduce emissions despite the short residence time, a platinum mesh was placed after the combustion chamber, which drastically decreased the CO emissions. The combustor performance was compared with that of other miniature combustors, and the results verified that the present combustor has suitable combustion characteristics for a UMGT, although the overall combustor size and heat loss need to be reduced.     

Investigation on combustion characteristics and NO formation of methane with swirling and non-swirling high temperature air

Combustion characteristics of methane jet flames in an industrial burner working in high temperature combustion regime were investigated experimentally and numerically to clarify the effects of swirling high temperature air on combustion.Speziale-Sarkar-Gatski（SSG） Reynolds stress model,Eddy-Dissipation Model（EDM）,Discrete Ordinates Method（DTM） combined with Weighted-Sum-of-Grey Gases Model（WSGG） were employed for the numerical simulation.Both Thermal-NO and Prompt-NO mechanism were considered to evaluate the NO formation.Temperature distribution,NO emissions by experiment and computation in swirling and non-swirling patterns show combustion characteristics of methane jet flames are totally different.Non-swirling high temperature air made high NO formation while significant NO prohibition were achieved by swirling high temperature air.Furthermore,velocity fields,dimensionless major species mole fraction distributions and Thermal-NO molar reaction rate profiles by computation interpret an inner exhaust gas recirculation formed in the combustion zone in swirling case.     

燃烧室压力对燃油喷雾和燃烧的影响研究

采用CHAMKIN模拟分析燃烧过程,基于自行设计的可视化定压燃烧系统试验研究燃烧室压力对燃油喷雾和燃烧的影响。结果表明:随着压力的升高雾化效果逐渐变差;进气旋流可以改善雾化效果;如果进气旋流是高温气体,则改善情况更明显。压力的增加仅加快了反应速率,缩短了着火延迟时间,并没有引起着火过程中温度的很大变化。随着燃烧压力的增加,火焰逐步向燃油喷嘴处移动,可通过提高烟气卷吸率增强气旋效果,使火焰更长,燃烧更均匀,避免烧坏油头及燃烧室内部分温度过高等不良后果。