燃气轮机燃烧室内部两相流动数值模拟与结构优化

针对燃气轮机低污染燃烧室内部流动的特殊要求，基于燃烧室完整真实几何结构进行三维的冷态模拟和两相流动模拟，分析内部的流动规律以及原始设计中存在的问题。通过改进燃烧室几何结构，得出更加合理的流场分布，从而指导燃烧室的结构优化设计。改进后的数值模拟结果表明：所采取的改进措施的效果明显，所建立的流动分析系统可以进行燃气轮机燃烧室的优化设计。     

燃气轮机环形燃烧室内燃烧流动的数值模拟

对一个复杂的GE—F101型工业燃气轮机环形燃烧室，采用Reynolds应力湍流模型(RSM)、EBU—Arrhenius湍流燃烧模型和六通量热辐射模型描述其燃烧流动，应用FLUENT软件进行了三维化学反应流场的数值模拟研究。研究结果表明：旋流和燃料进口射流对燃烧室流内温度和流场分布有着重要的影响；利用数值手段得到燃烧室出口的温度分布以判断其能否满足透平叶片进口温度的要求是可行的；燃烧室工作压强对出口的NO分布有着重要影响。在燃用气体燃料时，燃气轮机的NO排放主要来自于热NO，瞬时NO只占很小一部分。图11参6     

数值模拟环形燃烧室两相反应流场

在任意曲线坐标系下,采用一种整体分区结合法,对包扩压器和火焰筒在在内的环形燃烧室三维两相反应流进行了数值模拟。所相采用Ｅｕｌｅｒ方法处理,并采用标准ｋ－ε双方程紊流模型、ＥＢＵ－Ａｒｒｈｅｎｉｕｓ紊流燃烧模型,六通量热辐射模型;液相采用Ｌａｇｒａｎｇｅ法处理。在非交错网格体系下,气相用ＳＩＭＰＬＥ法求解,液相采用颗粒群轨道模型,并用ＰＳＩＣ算法对其进行数值求解,计算结果表明这种新方法是可行的。     

旋风炉内气相燃烧及两相流动的数值模拟

在有反应两相流动及煤粉燃烧的全双流体模型（ＰＴＦ模型,ｐｕｒｅ ｔｗｏ－ｆｌｕｉｄ ｍｏｄｅｌ）基础上,采用修正的ｋ－ε－ｋｐ两相湍流模型,对旋风炉内的湍流气相燃烧（甲烷和一氧化碳的燃烧）及在气相燃烧条件下的两相流动进行了数值模拟研究,模拟结果表明,在有燃烧的情况下,在旋风炉的底部存在近壁回流区,该回流区有利于火焰稳定,气粒两相切向速度分布具有类似的Ｒａｎｋｉｎｅ涡结构,该研究为煤粉燃烧的数值模拟     

燃气轮机燃烧室流场数值计算研究及分析

对燃气轮机逆流式环形燃烧室,热态三维流场的数值模拟问题进行了研究,建立了三维计算模型,生成了数值计算网格。数值模拟研究表明,改变燃烧室的几个结构参数,可以得到更加合理的流场。通过对关键截面的流动分析,可以判断燃烧室设计的合理性,为进一步优化燃烧室结构设计、改善流场奠定了基础。     

缩放喷管内两相流动的数值模拟及喷管设计

本文建立了非平衡态相变时,计及两相相对滑移和流型转变的两流体分相流动的机理模型,对缩放喷管内汽液两相闪蒸临流进行了数值模拟,编制了计算程序,结果与实验数据吻良好,该喷管的设计方法成功地应用于湖南岳阳长岭炼油厂节能系统改进工程中。     

燃气轮机低热值合成气燃烧室内三维湍流流动的数值模拟研究

对GE-F101型工业燃气轮机环形燃烧室燃用甲烷和低热值合成气的燃烧性能进行了数值研究,采用标准κ-ε湍流模型和涡耗散湍流燃烧模型对燃烧室在不同燃料条件下的流场特性进行了数值模拟,并对燃烧室内的流场结构、温度分布、火焰结构及NOx分布进行了分析与比较;在此基础上对原燃烧室进行了一些改造.结果表明:随着燃料热值的降低,燃料射流速度增大,燃料和空气的混合程度减弱,燃烧稳定性降低,燃烧室内最高温度降低,NOx排放量减少;通过增大燃料喷嘴口径和增加旋流器的旋流数,可在一定程度上改善燃烧室内流动结构,增强燃料和空气的混合程度,因而提高了燃烧稳定性.     

喷油嘴喷孔内部空穴两相流动数值模拟分析

在柴油机喷油嘴喷孔内部空穴流动现象分析的基础上。建立了完全发展了的空穴流动的二维气液两相流空穴模型，并进行了喷孔内部气液两相流数值模拟。计算结果与国外已有实验数据的对比表明所建模型是正确的，在此计算模型框架下分析了喷孔上下游压差和喷孔入口圆角半径、喷孔直径和长度等几何特征参数对喷孔内空穴区域分布的影响，进而分析了对喷雾特性的影响。     

某型燃气轮机燃烧室性能数值模拟

应用CFD方法对航改QD128燃气轮机燃烧室性能进行了数值模拟。模拟结果表明:燃烧室流量分配设计基本合理,燃烧室内流场分布符合设计规律;燃烧室出口平均温度为1 298K,热点温度1 486K,径向温度分布曲线符合设计要求,OTDF=0.280,RTDF=0.086,略高于航机水平。模拟结果丰富了QD128燃机性能指标,为该机的运行、改进提供了可靠的参考依据。     

某重型燃气轮机燃烧室燃烧性能的数值模拟

对某重型燃气轮机的燃烧室分成火焰筒头部、全尺寸火焰筒、过渡段三部分进行了热态的数值模拟研究。对火焰筒头部采用轴向旋流器、不等间距喷燃孔等结构的燃烧室进行计算,得到了燃烧室的三维流场分布及温度分布。研究了旋流器安装角变化对燃烧性能的影响。计算结果很好地反映该重型燃气轮机燃烧室燃烧流动特点,为重型燃气轮机燃烧室的设计开发提供了重要参考。     

发酵罐内固液两相流的数值模拟

以大连市某污泥处理厂为研究背景,以其厌氧发酵罐为研究对象,利用Fluent软件,采用RNG湍流模型、多相流中的混合模型对发酵罐内侧进式搅拌器对污泥与水固液两相的三维流动的影响进行数值模拟。通过模拟得到罐内速度场、固相浓度场的分布情况,分析对固相污泥的均匀分布产生影响的因素,对厌氧发酵过程中搅拌器的运行参数及结构参数的优化提供理论依据。     

Numerical simulation of bubbly two-phase flow in a narrow channel

An advanced numerical simulation method on fluid dynamics - lattice-Boltzmann (LB) method is employed to simulate the movement of Taylor bubbles in a narrow channel, and to investigate the flow regimes of two-phase flow in narrow channels under adiabatic conditions. The calculated average thickness of the fluid film between the Taylor bubble and the channel wall agree well with the classical analytical correlation developed by Bretherton. The numerical simulation of the behavior of the flow regime transition in a narrow channel shows that the body force has significant effect on the movement of bubbles with different sizes. Smaller body force always leads to the later coalescence of the bubbles, and decreases the flow regime transition time. The calculations show that the surface tension of the fluid has little effect on the flow regime transition behavior within the assumed range of the surface tension. The bubbly flow with different bubble sizes will gradually change into the slug flow regime. However, the bubbly flow regime with the same bubble size may be maintained if no perturbations on the bubble movement occur. The slug flow regime will not change if no phase change occurs at the two-phase interface.     

高速热气流试验系统燃烧室温度性能数值仿真

给出了燃油在高速热气流试验系统燃烧的分布式数学模型,在GAMBIT软件中建立了系统燃烧室的几何模型,并进行了网格划分。为了了解燃油在燃烧室燃烧的性能以及系统燃烧室的出口温度分布,利用计算流体力学仿真软件FLUENT模拟了燃油在燃烧室中的燃烧,分别研究了不同油气比对燃烧室出口温度的影响和不同喷射角度对燃烧室出口温度的影响。仿真结果表明,油气比为理论油气比,喷射角度为30°左右时,燃烧室出口温度最均匀。     

Numerical simulation of 3D turbulent isothermal flow in a vortex combustor

Numerical simulations of strongly swirling turbulent flows in a vortex combustor (VC) are conducted. A comprehensive investigation of a three-dimensional isothermal VC flow using three first-order turbulence models: the standard k–ε turbulence model, Renormalized Group (RNG) k–ε model and shear stress transport (SST) k–ω model; and a second-order turbulence model, Reynolds stress model (RSM) together with a second-order numerical differencing scheme is conducted in the present work. The computation indicates that the RSM is superior to the other turbulence models in capturing the swirl flow effect in comparison with measurements. The numerical results for the VC flow provide the characteristics of the flow in terms of relevant parameters for the VC design and operation, composed of axial and tangential velocities, pressure fields, and turbulence kinetic energy.     

Numerical simulation of thermofluid characteristics of two-phase slug flow in microchannels

A fundamental study of heat transfer characteristics of two-phase slug flow in microchannels is carried out employing the Volume-of-Fluid (VOF) method. Despite of the fact that numerical simulations of two-phase flows in microchannels have been attempted by many investigators, most efforts seem to have failed in correctly capturing the flow physics, especially those pertaining to the slug flow regime characteristics. The presence of a thin liquid film in the order of 10 μm around the bubble is a contributing factor to the above difficulty. Typically, liquid films have a significant effect on the flow field and heat transfer characteristics. In the simulations reported in this paper, the film is successfully captured and a very high local convective heat transfer coefficient is observed in the film region. A strong coupling between the conductive heat transfer in the solid wall and the convective heat transfer in the flow field is observed and characterized. Results showed that unsteady heat transfer through the solid wall in the axial direction is comparable to that in the radial direction. Results also showed that a fully developed condition could be achieved fairly quickly compared to single-phase flows. The fully developed condition is defined based on the Peclet number (Pe) and a dimensionless length of the liquid slug. Local and time-averaged Nusselt numbers for slug flows are reported for the first time. It was found that significant improvements in the heat transfer coefficient could be achieved by short slugs where the Nusselt number was found to be 610% higher than in single-phase flows. The study revealed new findings related to slug flow heat transfer in microchannels with constant wall heat flux.     

低温脉动热管气液两相流数值模拟

为了研究液氦温区下脉动热管流型演化及运行特性,采用氦为工质,基于多相流VOF方法建立了闭式环路结构低温脉动热管的三维数值模型,并对该模型进行了数值求解。研究了初始充液后管内气液分布情况,获得了不同时刻管内流型变化及温度分布。模拟结果显示:低温下脉动热管与常温脉动热管相似,也存在着泡状流、柱状流、环状流等流型的演变。当低温脉动热管稳定运行时,管内温度会随着时间进行周期性的脉动。从脉管内截面温度脉动的波形上看,蒸发段温度波动与冷凝段温度波动相位相差180°左右,而绝热段温度波动相位更接近蒸发段。与常温热管相比,低温液氦脉动热管温度波动幅度远远小于常温工况下的波动幅度。     

Numerical simulation of gas-contaminated refrigerant two-phase flow through adiabatic capillary tubes

An unfavorable effect of gas impurities on the throttling process inside a small-diameter tube, i.e. a capillary tube, has been studied in detail. A special testing capillary tube equipped with precise temperature and pressure sensors has been used for an experimental investigation of the capillary flow of a saturated fluorocarbon refrigerant, R218, contaminated by dissolved nitrogen. The gas impurities significantly affected the throttling process, since the two-phase flow started notably earlier than in the case of pure refrigerant flow. Moreover, the gas contamination resulted in a decreased mass flow rate of refrigerant delivered through the capillary tube. A comprehensive numerical model has been developed to simulate the capillary flow of gas-contaminated refrigerant. The model takes into account two coincident thermodynamic events: the throttling process of the refrigerant (solvent) and the gradual release of the dissolved gas impurities (solute) from the refrigerant liquid phase. The gas release is in principle described by using the temperature correlation of the Henry’s law constant. The model considers adiabatic, thermodynamically equilibrated capillary flow with homogeneous two-phase flow. The numerical simulation is in good agreement with our experimental data measured for R218 contaminated by nitrogen.     

Numerical simulation of model scramjet combustor flowfield

A new concept has been raised and adopted in this paper to enlarge the scope of the two‐dimensional model particularly for the purpose of dealing with three‐dimensional normal injection cases. Meanwhile, the method has a very good performance for its short cyclic period. The new idea was realized through special resolution with continuity equations; i.e., mass flow was directly added in the source term of the continuity equation. To prove the robustness of this illuminating method, comparisons using calculations were carried out, and the results are satisfactory. A model scramjet combustor tested on the free‐jet scramjet test facility was illustrated and underwent numerical calculations with the two‐dimensional program, adopting the above simplified injecting method. To simulate the chemical reaction process in the scramjet tunnel, a five‐species, single‐step reaction model was introduced in the calculation process. This research presents the major aerodynamic parameters and components of mass fraction distribution within the model combustor channel, which made it easy to observe and analyze the flowfield. Finally, wall pressure comparisons between the numerical and experimental results were carried out to verify the accuracy of the calculation model. © 2007 Wiley Periodicals, Inc. Heat Trans Asian Res, 36(5): 295– 302, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20159     

Numerical analysis of two-phase flow in condensers and evaporators with special emphasis on single-phase/two-phase transition zones

A numerical study of the thermal and fluid-dynamic behaviour of the two-phase flow in ducts under condensation or evaporation phenomena is presented. The numerical simulation has been developed by means of the finite volume technique based on a one-dimensional and transient integration of the conservative equations (continuity, momentum and energy). The discretized governing equations are solved using the Semi-Implicit Method for Pressure-Linked Equations (SIMPLE) which allows back flow phenomena. Special emphasis is performed on the treatment of the transition zones between the single-phase and two-phase flow. The empirical inputs of single-phase and two-phase flow, including sub-cooled boiling and dry-out, have been adapted by means of adequate splines in the transition zones where the heat transfer correlations available in the literature are not suitable. Different numerical aspects have been evaluated with the aim of verifying the quality of the numerical solution. The mathematical model has been validated by comparison with experimental data obtained from literature considering condensation and evaporation processes. This comparison shown the improvements in the numerical solution not only in the transition zone but also in all condenser and evaporator ducts, when the special treatment for transitions is used. Illustrative results on double-pipe heat exchanger are also presented.