双锥燃烧室冷态流场的实验研究

根据五孔球形探针的测试原理,对应用于高效煤粉工业锅炉的双锥燃烧室内部冷态流场进行了测量,得出燃烧室内部流场是顺时针旋转并呈对称分布,前锥的流场分布分为3层,即边缘区、夹层区和中央区,存在回流;后锥流场随着出口锥形半径的逐渐缩小,总速度不断增大,不存在回流。同时也分析了流场分布对燃烧室燃烧性能的影响,前锥流场的布局有利于实现煤粉的着火,后锥流场影响煤粉和空气的混合流在炉膛的分布,使其既能保持足够的射程,又能防止气流冲刷壁面,避免结焦。     

多射流锥形对撞流气流床流场特性实验及模拟研究

为了考察多射流锥形对撞煤加氢气流床内的冷态流场情况,以3 t/d的热态煤加氢气化炉为依据建立了气流床冷模装置。使用三维动态颗粒分析仪(3D-PDA)对气流床内的速度场进行了测量,同时使用Fluent软件,采用κ-ε模型对气流床内的流动情况进行了模拟研究,模拟结果与实验结果能较好地吻合。结果显示:多射流锥形对撞气流床内的流体流动分为对撞区、射流区、回流区和管流区,在考察范围内,随着进气速度的增加,回流区的体积占比先增大后减小;随中心喷嘴携带气速度的增加,射流区速度增大,且较进气速度的影响更为敏感;适当增加进气角度,则会降低射流区速度,增大回流区体积。     

三通道德士古气化炉冷态数值模拟

利用fluent软件对三通道简化喷嘴德士古气化炉进行冷态数值模拟,主要研究了中心配比对速度场分布、湍流混合、颗粒停留时间的影响。气相湍流采用Realizeable k-ε,颗粒离散相采用了DPM模型。结果表明,中心流体和外环流体通过喷嘴高速射速炉内,形成了明显的射流区、回流区及管流区。其中高速区集中在轴线处,射流区的速度衰减很大。最小颗粒停留时间受中心轴线最大速度的影响显著,回流区对最大停留时间的影响较大。     

辐射废锅内气固两相流场的冷态测试与数值模拟

采用冷态实验测量和数值模拟相结合的方法,对辐射废锅内的冷态气固两相流场进行了研究。搭建了辐射废锅冷模装置,利用恒温热线风速仪和皮托管对辐射废锅内的气相冷态流场进行测量。利用马尔文激光粒度分析仪对辐射废锅出口、底部渣池以及附壁颗粒的粒径进行了采样分析。运用Realizable k-ε湍流模型和随机轨道模型分别对气相流场和颗粒运动轨迹进行了数值模拟。研究发现:Realizable k-ε湍流模型计算得到的气相流场结果与实验值吻合较好,辐射废锅内筒顶部存在一入口射流,射流沿流向逐渐衰减,气相流场在内筒底部趋于稳定;大部分颗粒直接被辐射废锅渣池捕集,少量细小颗粒被气流携带进入辐射废锅环隙或从出口逃逸;颗粒粒径越大、密度越高,颗粒的跟随性越差,出口颗粒的停留时间越长。     

Texaco气化炉流场特性的模拟计算

采用CFD软件对Texaco气化炉进行建模,计算不同工况条件下的冷态流场特性,讨论了气体入口流速对流场影响的规律。模拟结果表明,Texaco气化炉燃烧室内存在射流区、管流区、回流区,回流区是影响气化炉内流场的主要因素,其面积随着入口速度增加而增大,而管流区面积随入口速度增加而减小;在径向流速分布图中,回流区气体流速具有明显拐点,管流区气体流速无明显拐点。     

带有非对称结构钝体燃烧器出口流场的冷态对比实验

在矩形风洞中放置钝体以模拟燃烧器的冷态出口流场,用靠背毕托管对非对称结构钝体后的回流流场进行了实验测定,同时也测定了带有对称结构钝体后的回流流场作为比较对象。实验得到了各个流场在主流方向上的速度分布,同时由流函数的定义求出了流场的流函数值的分布。对照分析得出:在非对称结构钝体后有较长的回流区长度和不对称的旋涡对结构,同时偏心放置时旋涡对的不对称性更为明显。     

Texaco气化炉冷态流场和湍流混合的数值模拟

在直径为1000mm,高4000mm的双通道射流喷嘴的气化炉上,以Texaco气化炉冷模试验为基准对象,将空气经环隙和中心射入气化炉,以氢气为示踪剂,预测环隙和中心射流的混合程度。结合流体质量与动量守恒方程和k-ε湍流模型,用SIMPLER算法计算,对气化炉内的冷态流场和湍流混合进行了模拟,模拟了炉内速度分布、量纲一浓度分布、混合分数分布和轴向衰减的情况。结果显示:气化炉内浓度分布极不均匀;炉内存在富氧和贫氧区;环隙和中心通道射流动量比加大,混合分数沿轴向衰减加快,达到充分混合的时间缩短。模拟结果与冷模试验结果的比较表明计算值与试验值吻合良好。     

循环流化床回流物料循环的特性

为了研究循环物料在流化床内回流并参与循环的过程,进一步揭示流化床内物料的循环特性,文中搭建了冷态循环流化床顶部回流试验台。利用激光多普勒粒子动态分析仪(PDA)对塔内颗粒回流时床内气固二相流场和颗粒浓度分布进行了测量。同时对物料回流量和床内表观气速等操作条件对回流过程的影响进行了考察。研究表明,回流颗粒在流化床内的返混可以分为3个区域:回流区、返混加速区和主流区,回流颗粒造成床内流场的不均匀性。回流长度主要受物料回流量和床内表观气速影响。     

五孔探针应用于下出风旋风筒流场的研究

下出风旋风筒具有低压损、利于布置的优点,在降低预热器压损方面具有较大应用前景。以五孔探针为测试工具,对下出风旋风筒内部流场进行了研究。结果表明,切向速度Vt由内壁向中心增大,到直径约等于直筒直径0.5倍的圆周上达最大值,再往中心就急剧减小。流动状态由边壁自由涡和中心区域强制涡组成;径向速度Vr在数值上比Vt小,在下出风旋风筒中心轴线附近呈现类汇流,旋风筒边壁区域呈现类源流;轴向速度Vz在旋风筒顶部以及排气管周围存在上升气流,其余位置都是下降气流,利于降低旋风筒阻力。经拟合得到下出风旋风筒的阻力系数ξ =3.90,属于阻力低的一类旋风分离器。采用K-ε湍流模型对下出风旋风筒内部的流场进行了研究,数值模拟得到的三维流场与五孔探针测试结果基本一致。     

气流床气化炉激冷环冷态流场数值模拟

针对气流床气化炉激冷室的工作特点,建立了一套激冷室激冷环的冷态流动数学模型,利用Fluent软件,对激冷环气相冷态流场进行数值模拟。通过模拟与实验对比,分析激冷环上不同位置喷嘴的流场分布;通过改变激冷环的进气方式,分析不同进气结构对激冷环上喷嘴速度的影响。结果表明:相比二进气道结构,四进气道结构使得激冷环喷嘴的速度分布相对均匀,能够达到激冷环对合成气强化换热的效果。     

预燃室对逆喷旋流煤粉燃烧器流场特性作用研究

煤粉高效低氮燃烧技术是煤炭高效利用领域持续关注的热点。煤粉燃烧器作为煤粉锅炉的核心设备,研究适合多煤种、宽负荷条件的煤粉燃烧器设计原理及技术至关重要。逆喷射流稳燃机理大都应用在航空发动机和燃气轮机领域,在煤粉燃烧领域应用极少。前人大量研究了预燃室对旋流燃烧器流场特性的影响,但鲜见预燃室对逆喷旋流燃烧器流场影响的相关研究。为了探究预燃室对逆喷旋流煤粉燃烧器流场特性的影响规律,笔者针对一款20 t/h逆喷旋流燃烧器,基于等温模化原理建立冷态燃烧器模型,利用热线风速仪和飘带法进行了流场测试和分析,结果表明:预燃室的存在不改变逆喷旋流煤粉燃烧器回流区环形的形状,但在逆喷旋流煤粉燃烧器内形成一个有利于煤粉着火的轴向速度低和湍流强度大的回流区。在X/D<1.3区域内,由于圆锥形预燃室对气流的挤压作用,预燃室的存在对回流区的面积起到抑制作用;在1.32.3区域内,预燃室对燃烧器内部流场的作用减弱,可忽略不计。在预燃室的作用下,回流区最宽处的直径从0.97D降至0.86D,最大相对回流率位置从截面X/D=1后移到截面X/D=1.6处,相对回流率从1.17减小至0.99。预燃室的存在对二次风区域内的轴向平均速度和湍流度分布规律影响较大。无预燃室工况下,在X/D<0.6区域内,速度和湍流度均出现峰值,在X/D>1.6区域内峰值消失,内外二次风完全混合;有预燃室工况下,在X/D<0.6区域速度沿着径向方向逐渐增大,湍流度沿着径向方向逐渐减小,在X/D>1.6区域,速度和湍流度沿着径向方向分布均匀。预燃室的存在有利于回流区煤粉的稳定燃烧,工程应用中起到煤粉迅速着火以及难燃煤稳定燃烧的作用。另外预燃室壁面气流速度较大,刚性强,避免预燃室壁面超温或结焦现象的发生,延长了煤粉燃烧器无故障运行时间和整体的使用寿命。     

Regimes of Unstable Expansion and Diffusion Combustion of a Hydrocarbon Fuel Jet

Results of an experimental study of hydrodynamics and diffusion combustion of hydrocarbon jets are presented. Various regimes of instability development both in the jet flame proper and inside the source of the fuel jet are considered. The experiments are performed for the case of subsonic gas jet expansion into the air from a long tube 3.2 mm in diameter in the range of Reynolds numbers from 200 to 13 500. The fuel is the propane–butane mixture in experiments with a cold jet (without combustion) and pure propane or propane mixed with an inert dilutant (CO₂ or He) for the jet flame. The mean velocity and velocity fluctuations in the near field of the jet without combustion are measured. Among four possible regimes of cold jet expansion (dissipative, laminar, transitional, and turbulent), three last regimes are investigated. The Hilbert visualization of the reacting flow is performed. The temperature profiles in the near field of the jet are measured by a Pt/Pt–Rh thermocouple. An attached laminar flame is observed in the transitional regime of propane jet expansion from the tube. In the case of combustion of C₃H₈ mixtures with CO₂ or with He in the range of Reynolds numbers from 1900 to 3500, the transitional regime is detected in the lifted flame. Turbulent spots formed in the tube in the transitional regime exert a significant effect on the flame front position: they can either initiate a transition to a turbulent flame or lead to its laminarization.     

Gas self-ignition in a plane vortex chamber

This paper describes the numerical modeling of gas flow in a plane vortex chamber by using the Navier–Stokes equations. The model is based on the laws of conservation of mass, momentum, and energy for nonstationary two-dimensional compressible gas flow in the case of axial symmetry with a tangential component of the gas velocity. The processes of viscosity, thermal conductivity, and turbulence are accounted for. It is shown that the transition of the kinetic energy of gas into thermal energy as a result of transfer processes leads to the formation of hot spots in the boundary layers near the walls of the chamber. The gas temperature at these hot spots can exceed the gas combustion temperature, while the gas remains rather cold in the neighboring regions. This could be the reason for the cold gas self-ignition observed in the experiments. The turbulence of the flow and the processes of mixing and diffusion of the components make a significant contribution to the capacity of gas self-ignition.     

蓄热式钢包烘烤过程中包内高温低氧特性的数值模拟

为了分析入炉气体的预热温度对高温空气燃烧过程的影响,综合考虑体系的质量、动量、能量守恒以及燃烧体系的组份平衡,建立了煤气-空气双预热的三维非稳态燃烧数学模型,并以CFX4.3为计算平台,耦合流体流动、燃烧和换热过程,首次对蓄热式燃烧过程中高温低氧特性进行了数值研究,得出了在不同预热温度时,燃烧室内气体温度场和氧气浓度场分布. 结果表明, 提高气体预热温度有利于加快燃烧进程,提高燃烧室内气体的整体温度及温度均匀性,降低局部氧浓度.     

旋转流中预混合火焰高速传播现象—II.点火位置与燃烧过程

在前期关于Vortex-bursting旋流式预混燃烧器的燃烧效率及其进口混合气速度分布对燃烧效率的影响实验基础上,围绕燃烧器的点火特性,对旋流场中的点火位置和稳定火焰形成进行了数值分析.结果表明,不适当的点火位置会影响稳定火焰的形成,在相同的燃烧工况下,在流场中点火位置不同,火焰的发展出现不同的趋势.在靠近中心轴附近的低速区点火时,火焰能够稳定;在靠近管壁的高速区点火时,撤离点火源后,火焰吹熄.本结果对于强化预混合燃烧的稳定性具有理论和工程指导意义.     

旋转流中预混合火焰高速传播现象-II. 点火位置与燃烧过程

在前期关于Vortex-bursting旋流式预混燃烧器的燃烧效率及其进口混合气速度分布对燃烧效率的影响实验基础上，围绕燃烧器的点火特性，对旋流场中的点火位置和稳定火焰形成进行了数值分析. 结果表明，不适当的点火位置会影响稳定火焰的形成，在相同的燃烧工况下，在流场中点火位置不同，火焰的发展出现不同的趋势. 在靠近中心轴附近的低速区点火时，火焰能够稳定；在靠近管壁的高速区点火时，撤离点火源后，火焰吹熄. 本结果对于强化预混合燃烧的稳定性具有理论和工程指导意义.     

Experimental Simulation on Chemical-looping Combustion of Cold Model（英文）

The pressure profiles, gas velocities, solid circulation rate, solids flux, residence time distribution of gas and particles in chemical-looping combustion reactors and gas leakage were studied in a cold flow model unit. And these parameters in both air and fuel reactors were measured in the experimental stage. The experimental results show that gas fluidization velocity in the air reactor is 1.8 m/s, gas fluidization velocity in the fuel reactor 0.5 m/s, and the bed materials inventory of the two reactors between 1.2 to 3.15 kg. The first cold flow model results show that the solid circulation rates are sufficient. The appropriate operating conditions are optimized and the summary of final changes is made the on cold model. The proposed design solutions are currently being verified in a cold flow model simulating the actual reactor(hot) system. This paper presents an overview of the research performed on a cold flow model and highlights the current status of the technology.     

Experimental Simulation on Chemical-looping Combustion of Cold Model

The pressure profiles, gas velocities, solid circulation rate, solids flux, residence time distribution of gas and particles in chemical-looping combustion reactors and gas leakage were studied in a cold flow model unit. And these parameters in both air and fuel reactors were measured in the experimental stage. The experimental results show that gas fluidization velocity in the air reactor is 1.8 m/s, gas fluidization velocity in the fuel reactor 0.5 m/s, and the bed materials inventory of the two reactors between 1.2 to 3.15 kg. The first cold flow model results show that the solid circulation rates are sufficient. The appropriate operating conditions are optimized and the summary of final changes is made the on cold model. The proposed design solutions are currently being verified in a cold flow model simulating the actual reactor (hot) system. This paper presents an overview of the research performed on a cold flow model and highlights the current status of the technology.     

通过技术创新提高气-气换热器的可靠性

介绍了Aker Solutions公司的最新技术创新——OPx~（TM）换热器及其在硫酸装置冷换热器、冷再热换热器和SO_3冷却器中的应用。该换热器采用带丝网垫的分离室捕集SO_2气体夹带的大颗粒酸雾,并采用热SO_3气体分流的逆/并流设计确保最低管壁温度始终高于酸蒸气露点。这些特点可有效减轻酸雾和酸蒸气冷凝腐蚀,提高气-气换热器的运行可靠性。     

Effects of pressure and inlet temperature on coaxial gaseous methane/liquid oxygen turbulent jet flame under transcritical conditions

This study has investigated numerically turbulent flames of cryogenic oxygen and methane under supercritical pressures relevant to liquid propellant rocket engines. A real-fluid version of the flamelet equations is employed to accommodate simultaneously non-equilibrium chemistry of hydrocarbon fuel and non-ideal thermodynamics in local flame structures while the effect of turbulent fluctuations is accounted for via a presumed probability density functions. The present model reproduced qualitatively well the experimentally observed unique feature of a transcritical flame of coaxial gaseous methane/liquid oxygen injector, which is characterized by sudden flame expansion, abruptly terminated flame tip, and expansion induced flow recirculation. Numerical results reveal that pseudo-boiling phenomena occurred in the transcritical mixing layer between the cryogenic oxygen core and the surrounding hot gas play a crucial role in mixing and combustion processes. It is also found that the transcritical flame structure is drastically affected by elevating the chamber pressure or increasing the oxygen inlet temperature in terms of flame length, sudden expansion angle, and reverse flow strength. Detailed discussions are made for effects of the real-fluid behaviors on the turbulent flame field as well as on the local flame structure in mixture fraction space.