平展流冷态湍流场的PIV测量

针对单烧嘴湍流预混平焰冷态实验模型,采用粒子激光测速(PIV)技术对烧嘴下方主要燃烧区的速度场(250mm×350mm)进行了测量,得出在旋流强度为1.76,空气量/煤气量为19.39下的速度场。速度场由回流区、附壁射流区和过渡区组成,同时进一步分析了三个区域内径向速度和轴向速度的变化规律。     

氧气顶吹转炉冶炼初期二次燃烧流场速度分布规律

采用先进的速度测试手段(PIV)测量了氧气顶吹转炉初期冷态二次燃烧二维流场,发现了在氧射流两侧形成两个强回流区.分析了不同截面上二次氧射流速度的分布特点及射流两侧回流区的速度分布规律.     

氧气顶吹转炉冶炼初期二次燃烧流场的PIV测试研究

采用粒子图像测速技术(PIV)测量了氧气顶吹转炉冶炼初期二次燃烧气相场,发现二次燃烧区域流场结构主要由内侧回流区、二次氧射流区和外侧回流区三部分组成;二次氧孔夹角增大,有利于氧气与CO的混合与燃烧,但夹角过大会加剧对转炉内衬的冲刷,降低热量传输效率;氧孔数目对二次燃烧流场也有一定的影响。     

旋流器叶片安装角对TAPS燃烧室性能影响

针对双环腔预混涡流器(TAPS)燃烧室头部对燃烧室流场和温度场的影响,建立了TAPS燃烧室数学模型,研究了三级旋流器叶片安装角的变化对燃烧室冷态流场、回流区形成、燃烧温度场分布的影响。结果表明:旋流器安装角的变化对燃烧室内的流动及燃烧特性会产生一定的影响。中旋流器安装角为40°时会导致回流区的变形,外旋流器叶片安装角对回流区的尺寸形状影响较大。另外,通过冷态和燃烧时从预燃级出发的流线可以看出冷态时预燃级的流场在径向尺寸上明显要大于燃烧时的尺寸。     

预燃室冷态流场的试验研究

本文介绍了一种带有中心射流、轴向旋流器的预燃室内冷态流场的试验研究结果，以及旋流数、风量、中心射流等对流场内轴向、切向、径向速度分布，回流区大小，压力场及回流率的影响，对预燃式烧嘴的设计有一定的参考价值。     

SL-Ⅱ型乙烯裂解炉冷态流动特性的数值模拟

对一台SL-Ⅱ型乙烯裂解炉炉膛辐射段冷态流场进行了数值模拟.通过模拟得出了该裂解炉膛辐射段冷态流场分布,进一步了解了裂解炉内的空气动力学特性,并对流场进行了定性分析.模拟结果表明,中部的高温烟气被卷吸到下部,在炉膛下部形成大的回流,有利于整个炉膛温度的均匀分布.侧壁烧嘴射流对炉膛流场影响不显著.     

套筒式陶瓷燃烧器流场边界条件测定

通过套筒式燃烧器两股有角度射流冷态实验模拟,对其入口速度边界条件做实验则定,为流场和燃烧场进行物理模拟和数值模拟提供了依据。     

天然气高速烧嘴试验研究

介绍关于限制空间旋转流场回流区特性、压力场、混合效果、浓度场及分段燃烧室各段风比的冷态模拟试验,确定烧嘴结构初型及主要部件筛选对象,热态燃烧试验,系列化扩型设计与试验,定型烧嘴的结构及烧嘴系列的燃烧性能等非预混式天然气高速燃烧器试验研究的概况及结果。此外,文章还讨论了限制空间的回流特性等问题。     

空燃比对平焰燃烧特性影响的冷态实验

 为研究加热炉内平焰烧嘴下方燃烧速度场的主要机理,采用相似和模化理论建立了冷态实验模型。应用粒子激光测速(PIV)技术对旋流强度为176、空燃比分别为1368、1939、2167的烧嘴下方的湍流速度场进行了测量,得到了主燃烧区域速度场的分布特性,并分析了空燃比对速度场的影响规律,得到了回流区顶部宽度、径向速度最大值出现的位置随空燃比的变化趋势,同时也得知径向速度最大值、轴向速度最大值均随着空燃比的增大而增大。首次得出不同空燃比下速度分量的最大值沿射流长度衰减的无因次曲线。     

金属矿山掘进工作面有限空间附壁射流技术应用研究

掘进工作面局部通风机压入式通风实际上是有限空间附壁射流,该技术已在各类金属矿山工程实践中得到广泛应用。以平泉小寺沟矿业有限公司铜钼矿615 m中段为工程背景,利用CFD技术对掘进工作面有限空间附壁射流流场进行模拟,根据流场模拟结果对现有有限空间附壁射流流场结构理论进行分析,将参数模拟计算结果与经验公式计算结果进行对比验证。研究表明,模拟结果与流场结构、经验公式计算结果一致,现有经验计算公式可以满足掘进工作面有限空间附壁射流通风计算的要求。同时,压入式通风风筒口与工作面距离不超过10 m的规程要求满足通风安全需要。     

Mathematical Model of Combustion in Blunt Annular Ceramic Burner

Symbol L ist　　A—— oxidant flow;　　c1 ,c2 —— constant of the k- ε urbulent model;　　 cg1 ,cg2 —— constant of the turbulent combustion model;　　f—— mixture fraction;　　 f,- f—— value of mixture fraction;　　 fu— fuel;　　F—— fuel flow;　　g—— concentration fluctuation;　　 H—— enthalpy,J;　　k—— kinertic energy for turbulent,m2 / s2 ;　　ma—— mass fraction of material a;　　 ox—— oxidant;　　 r,θ,z—— coordinate axis for cylinder coordinatesystem;　　 s—— equ…     

聚合射流流场的仿真模拟

 为研究有低密度伴随的聚合射流氧枪射流流场,利用氧枪射流检测系统,对常温下(冷态)以空气模拟的射流进行了物理模拟。结合数值模拟结果,分析了传统无伴随流射流以及带有副孔氦气低密度伴随情况下射流流场的流动状态,讨论了在不同的滞止压力和环境温度时有、无伴随射流流场特性。结果表明,修正的k ε双方程模型能较好地预测实验结果,伴随流的存在减缓了中心射流的沿程衰减,环境温度的变化影响射流在径向和轴向的流动状态。     

首钢京唐BSK顶燃式热风炉的燃烧技术

 为开发5500m3高炉BSK顶燃式热风炉技术,对顶燃式热风炉的燃烧机制和燃烧特性进行了研究。采用CFD数学仿真模拟研究了BSK顶燃式热风炉环形陶瓷燃烧器的燃烧机制,解析了顶燃式热风炉燃烧室内气体的混合、流动以及燃烧过程,计算分析了顶燃式热风炉燃烧过程的速度场、温度场以及浓度场分布。通过对实体热风炉的冷态测试,验证了CFD数学仿真计算的结果。研究结果表明,BSK顶燃式热风炉采用旋流扩散燃烧技术使燃烧过程速度场、温度场和浓度场分布均匀对称,并可以有效控制火焰长度和火焰形状,使煤气在拱顶空间内充分燃烧。速度场、温度场和浓度场的分布与煤气和助燃空气的初始分布有直接关系。通过燃烧器喷嘴结构优化设计可以显著提高空气与煤气混合的均匀性,改善燃烧室内浓度、温度分布以及火焰形状。     

CFD for Simulation of Crosswind on the Efficiency of High Momentum Jet Turbulent Combustion Flames

Industrial flares have been identified as a potential major source of hydrocarbon emissions from chemical and petrochemical plants in the Gulf Coast area. Several studies have shown that crosswind may compromise the expected 98% efficiency level of these units. In order to understand the key variables in flare operation, a 3D simulation has been performed to predict the effect of crosswind on the efficiency of high momentum, turbulent combustion flames by using the commercial software Fluent 6.2. First, a CH4+ air flame was simulated for quiescent conditions and temperature and concentration profiles were compared to experimental data. Simulations were then performed to study how combustion efficiency may be affected by increasing the crosswind velocity. We have also analyzed the effect of crosswind at higher jet velocities. Our results show that high momentum flames are more sensitive to the crosswind problem as the jet velocity increases. The ultimate goal of this model is to obtain a quantitative understanding of how crosswind may affect the operation of industrial flares, a major source of highly reactive volatile organic compound emissions from chemical and petrochemical plants.     

Velocity Profile and Flow Resistance Models for Developing Chute Flow

A developing boundary layer starts at the spillway crest until it reaches the free surface at the so-called inception point, where the natural air entrainment is initiated. A detailed reanalysis of the turbulent velocity profiles on steep chutes is made herein, including mean values for the parameters of the complete turbulent velocity profile in the turbulent rough flow regime, given by the log-wake law. Accounting both for the laws of the wall and the wake, a new rational approach is proposed for a power-law velocity profile within the boundary layer of turbulent rough chute flow. This novel approach directly includes the power-law parameters and does not require for a profile matching, as is currently required. The results obtained for the turbulent velocity profiles were applied to analytically determine the resistance characteristics for chute flows. The results apply to the developing flow zone upstream of air inception in chute spillways.     

大型蓄热式环形加热炉冷态流场试验分析

 根据模化理论,针对某大型高炉煤气双蓄热式环形加热炉,按照10∶1的比例建立了实物模型。根据二维PIV测试技术的原理,用高速摄像仪对各加热段炉膛进行示踪粒子拍摄和速度分布测量。研究发现从烧嘴喷出的气流,一般不会从正对的第一个吸风口吸出,越靠近均热段的喷口气流越不容易被最近的排烟口排出,从而延长了炉气在炉内的停留时间,避免了烟气短路;炉膛截面速度变化较大,距离烧嘴口越远,截面上速度越平缓;在一定的气流喷射角度下,喷嘴口两侧有气流旋涡产生;流量越大,气流越容易到达对侧炉墙。     

Large Eddy Simulation for Unsteady Turbulent Field in Thin Slab Continuous Casting Mold

The unsteady turbulent flow during the continuous casting of steel is important, because it influences critical phenomena that affect steel quality. Unsteady three-dimensional flow in the mold region of the liquid pool during continuous casting of steel slabs has been computed using realistic geometries starting from the submerged inlet nozzle to the mold. The cassette filter function was used to deal with unsteady Navier-Stokes equation, and then the turbulent flow in the thin slab CCM was simulated with the large eddy simulation method combined with the Smagorinsky sub-grid scale model in this paper. And the model was verified by the Particle Image Velocimetry (PIV) experimental results which was got from a relate scientific literature. In this thesis, by means of LES, the flow characteristics in the thin slab CCM were acquired, such as the vortex distribution, the formation of the large eddy coherent structures, development, shedding and fracture process. In the same time, the turbulent asymmetric distribution was revealed even the nozzle in the centre position. Interactions between the two halves cause large velocity fluctuations near the meniscus. And the vortex is located at the low velocity side adjacent to the SEN. Along with the unsteady time development, the unsteady turbulent large vortex structures of the liquid steel in the CCM presented periodic bias flow distribution, and the period is about 20 seconds.     

Turbulent Boundary Layer Flows Above a Porous Surface Subject to Flow Injection

A new analytical expression for velocity profile in a fully developed turbulent boundary layer above a porous surface subject to flow injection is derived by solving the coupled Reynolds equations and turbulent kinetic energy equation. The advection of turbulent kinetic energy is considered during the derivation, whereas the earlier studies have neglected it. The new solution reduces to the universal logarithmic law in the case of no flow injection. For the small injection, the solution can be expanded into a series form in terms of the normalized injection velocity. The leading order terms are found to be equivalent to those in the earlier works in which the advection of turbulent kinetic energy has been neglected in the derivation. The new solution can provide more accurate prediction of bed shear stress for a wide range of flow injection rate, fluid type (e.g., from air to water), and surface roughness. On the other hand, the earlier theories may significantly underestimate bed shear stress under high injection rates.     

Aspects of Inlet Boundary Prescription for a Turbulent Flow Field

In the literature on turbulent flow various combinations of velocity, turbulence kinetic energy, and eddy viscosity models have been proposed for the inlet boundary to a flow field. There appears to be no rational criterion for specifying inlet boundary conditions. The present study proposes a criterion to select the inlet boundary conditions by treating the inlet boundary as a part of the flow field. Using this criterion, any prescribed variation of velocity, turbulence kinetic energy k, and rate of dissipation of kinetic energy ε, must satisfy the governing flow field equations at the inlet boundary. Analysis of previously used profiles of velocity, kinetic energy, and dissipation of kinetic energy in the literature indicates that most of these do not satisfy the flow field equations. To substantiate the importance of inlet boundary conditions, several reported numerical simulations using k-ε turbulence models are reconsidered to determine if there is any linkage between the residual errors at the inlet boundary and the errors in the flow field simulation. Based on such an analysis, it is both logical and practical to hypothesize the inlet boundary as a part of flow field.