Numerical Simulation of 3—D Turbulent Gas—Particle FLows In a Nonslagging Cyclone COmbustor

ＮｕｍｅｒｉｃａｌＳｉｍｕｌａｔｉｏｎｏｆ３－ＤＴｕｒｂｕｌｅｎｔＧａｓ－ＰａｒｔｉｃｌｅＦｌｏｗｓＩｎａＮｏｎｓｌａｇｇｉｎｇＣｙｃｌｏｎｅＣｏｍｂｕｓｔｏｒ￥ＢｉａｏＺｈｏｕ，ＷｅｎｙｉＬｉｎ，ＬｉｘｉｎｇＺｈｏｕ（ＤｅｐａｒｔｍｅｎｔｏｆＥｎｇ...     

Numerical Simulation of Microgravity Flame Spread Over Solid Combustibles

Ｎｕｍｅｒｉｃａｌ　Ｓｉｍｕｌａｔｉｏｎ　ｏｆ　Ｍｉｃｒｏｇｒａｖｉｔｙ　Ｆｌａｍｅ　Ｓｐｒｅａｄ　Ｏｖｅｒ　Ｓｏｌｉｄ　ＣｏｍｂｕｓｔｉｂｌｅｓＮｕｍｅｒｉｃａｌＳｉｍｕｌａｔｉｏｎｏｆＭｉｃｒｏｇｒａｖｉｔｙＦｌａｍｅＳｐｒｅａｄＯｖｅｒＳｏｌｉ...     

Numerical Simulation of Active Suppression of Rotating Stallin Axial Compression Systems

ＮｕｍｅｒｉｃａｌＳｉｍｕｌａｔｉｏｎｏｆＡｃｔｉｖｅＳｕｐｐｒｅｓｓｉｏｎｏｆＲｏｔａｔｉｎｇＳｔａｌｌｉｎＡｘｉａｌＣｏｍｐｒｅｓｓｉｏｎＳｙｓｔｅｍｓＮｕｍｅｒｉｃａｌＳｉｍｕｌａｔｉｏｎｏｆＡｃｔｉｖｅＳｕｐｐｒｅｓｓｉｏｎｏｆＲｏｔａｔｉｎ...     

Vortex Simulation of Axisymmetrical Flows in Cylindrical Geometries．PartI：Numerical Algorithm

ＶｏｒｔｅｘＳｉｍｕｌａｔｉｏｎｏｆＡｘｉｓｙｍｍｅｔｒｉｃａｌＦｌｏｗｓｉｎＣｙｌｉｎｄｒｉｃａｌＧｅｏｍｅｔｒｉｅｓ．ＰａｒｔＩ：ＮｕｍｅｒｉｃａｌＡｌｇｏｒｉｔｈｍ￥ＡｎｄｒＧｉｏｖａｎｎｉｎｉ（ＵｎｉｖｅｒｓｉｔｅＰａｕｌＳａｂａｔｉｅｒａｎ...     

Numerical Calculation of 3—D TUrbulent Flow in Curvilinear Coordinate Systems with Nostaggered Grids

ＮｕｍｅｒｉｃａｌＣａｌｃｕｌａｔｉｏｎｏｆ３－ＤＴｕｒｂｕｌｅｎｔＦｌｏｗｉｎＣｕｒｖｉｌｉｎｅａｒＣｏｏｒｄｉｎａｔｅＳｙｓｔｅｍｓｗｉｔｈＮｏｎｓｔａｇｇｅｒｅｄＧｒｉｄｓＺｈａｎｇＪｉｎｇｚｈｏｕ；ＬｉＬｉｇｕｏ；ＷｕＧｕｏｃｈｕａｎ（Ｎａｍ...     

Numerical Simulation of Multistory Building Fire with Zone-Modeling Method

ＮｕｍｅｒｉｃａｌＳｉｍｕｌａｔｉｏｎｏｆＭｕｌｔｉｓｔｏｒｙＢｕｉｌｄｉｎｇＦｉｒｅｗｉｔｈＺｏｎｅ－ＭｏｄｅｌｉｎｇＭｅｔｈｏｄＦｕＺｈｕｍａｎ；ＦａｎＷｅｉｃｈｅｎｇ（ＳｔａｔｅＫｅｙＬａｂｏｆＦｉｒｅＳｃｉｅｎｃｅ，ＵｎｉｖｅｒｓｉｔｙｏｆＳ...     

Comparison of a Reaction Front Model and a Finite Difference Model for the Simulation of Solid Absorption Process

ＣｏｍｐａｒｉｓｏｎｏｆａＲｅａｃｔｉｏｎＦｒｏｎｔＭｏｄｅｌａｎｄａＦｉｎｉｔｅＤｉｆｆｅｒｅｎｃｅＭｏｄｅｌｆｏｒｔｈｅＳｉｍｕｌａｔｉｏｎｏｆＳｏｌｉｄＡｂｓｏｒｐｔｉｏｎＰｒｏｃｅｓｓ￥ＺｉｋａｎｇＷｕ；ＡｒｎｅＪａｋｏｂｓｅｎ；Ｘｉｕｇａｎ...     

Vortex Simulation of Axisymmetrical Flows in Cylindrical Geometries．PartII：Application to Pipes Incorporating an Orifice Plate

ＶｏｒｔｅｘＳｉｍｕｌａｔｉｏｎｏｆＡｘｉｓｙｍｍｅｔｒｉｃａｌＦｌｏｗｓｉｎＣｙｌｉｎｄｒｉｃａｌＧｅｏｍｅｔｒｉｅｓ．ＰａｒｔＩＩ：ＡｐｐｌｉｃａｔｉｏｎｔｏＰｉｐｅｓＩｎｃｏｒｐｏｒａｔｉｎｇａｎＯｒｉｆｉｃｅＰｌａｔｅ￥ＡｎｄｒＧｉｏｖａｎｎ...     

Two－Phase Critical Discharge of Initially Saturated or Subcooled Water Flowing in Sharp－Edged Tubes at High Pressure

Ｔｗｏ－ＰｈａｓｅＣｒｉｔｉｃａｌＤｉｓｃｈａｒｇｅｏｆＩｎｉｔｉａｌｌｙＳａｔｕｒａｔｅｄｏｒＳｕｂｃｏｏｌｅｄＷａｔｅｒＦｌｏｗｉｎｇｉｎＳｈａｒｐ－ＥｄｇｅｄＴｕｂｅｓａｔＨｉｇｈＰｒｅｓｓｕｒｅＸｕＪｉｎｌｉａｎｇ（ＩｎｓｔｉｔｕｅｏｆＮｕｃ...     

Numerical Solution of Flow Field Diagnosis Problem in Multistage Axial Compressors

Ｎｕｍｅｒｉｃａｌ　Ｓｏｌｕｔｉｏｎ　ｏｆ　Ｆｌｏｗ　Ｆｉｅｌｄ　Ｄｉａｇｎｏｓｉｓ　Ｐｒｏｂｌｅｍ　ｉｎ　Ｍｕｌｔｉｓｔａｇｅ　Ａｘｉａｌ　ＣｏｍｐｒｅｓｓｏｒｓＮｕｍｅｒｉｃａｌＳｏｌｕｔｉｏｎｏｆＦｌｏｗＦｉｅｌｄＤｉａｇｎｏｓｉｓＰｒｏｂｌｅ...     

顶燃式热风炉燃烧过程的数值模拟研究

针对某公司的旋流顶燃式热风炉及其工艺参数,建立了气体流动、传热的数学模型,采用非预混燃烧方法处理煤气的燃烧,对其现有工况进行了数值模拟,分析了炉体内部的流场、温度场和浓度场.结果表明,燃烧室温度分布不均匀,出口温度较低;由（于）空气过剩系数较小,导致煤气燃烧不充分,有大量CO剩余;火焰长度较长,严重影响格子砖的寿命.通过调整空气过剩系数,（）的增加空气过剩系数,燃烧室出口CO体积分数明显降低,火焰长度明显变短,出口温度明显提高.     

辐射通道一维稳态温度场数值模拟

为得到辐射对流通道中的温度分布,依据能量守恒原理,建立了辐射、对流非线性边界条件下圆形管壁与管内空气的传热数学模型,提出了管壁温度、管内冷却空气温度一维稳态换热有限差分求解方法,其中辐射换热计算采用基于辐射传递系数的蒙特卡罗法。分析了相关参数对辐射通道温度分布的影响,所研究的参数包括辐射器表面温度、管道长度与半径比、管内冷却空气流速等。计算结果表明：辐射器表面温度是影响辐射通道最高温度的主要因素。此方法可为辐射通道精细的热工特性计算提供温度场数据。     

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。     

Experimental study on the small‐scale diffusion flame of ethanol and the wall temperature field

An experimental investigation was carried out on the diffusion flames of liquid ethanol burning in air. Ceramic tubes with different inner diameters were used as burners. Three different flame structures at different flow rates were identified and different combustion regions were divided based on the experimental results. Some relevant factors which may affect the flame height and width were discussed. The outer surface wall temperature field of the tubes was measured in the combustion process. The results showed that both flame height and flame width all increased proportionally with an increasing flow rate in the steady flame region. Both flame height and flame width decreased with a decreasing tube inner diameter at the same flow rate. By decreasing the tube inner diameter, the quenching flow rate was decreased, the flow rate according to the produced periodic explosive flame decreased, and the flow rate range of the steady flames decreased. The outer wall temperature field presented an exponential distribution, and the wall temperature reached the greatest value at the outlet of the ceramic tube. © 2009 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20282     

The effect of chemical energy release on heat transfer from flames in small channels

Stable combustion in a heated tube, with a radius on the order of the flame thickness, is investigated experimentally and numerically. The downstream portion of the tube is heated by an external heat source resulting in a steady, axially varying temperature gradient along the tube wall. Strongly burning, axisymmetric methane/air flames are stabilized inside this wall temperature profile which are observed to be “flat” for sufficiently small tube dimensions. The position of these flames is dictated by a competition between the energy required to preheat the reactants, that released by combustion, and the heat lost to the wall. To model such flames, an extension to the standard 1-D, volumetric flame formulation is proposed to solve for wall/gas heat transfer by employing a thermal boundary layer. The boundary layer utilizes a non-linear, radially-varying heat source to account for combustion and captures the effect of enhanced interfacial heat transfer inside the reaction zone. The proposed numerical model gives improved quantitative predictions for flame stabilization position than approaches which neglect the effect of heat release by modeling heat transfer with Newton’s law of cooling and a local Nusselt number.     

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.     

Numerical study of methane and air combustion inside a small tube with an axial temperature gradient at the wall

A numerical study on CH₄ and air premixed combustion inside a small tube with a temperature gradient at the wall was undertaken to investigate the effects of inlet velocity, equivalence ratio and combustor size on combustion characteristics. The simulation results show that the inlet velocity has a significant influence on the reaction zone, and the flame front shifts downstream as the inlet velocity increases. The results also show that, the inlet velocity has no obvious effects on the flame temperature. The highest flame temperature is obtained if the equivalence ratio is set to 1. It is disclosed that the combustor size strongly influences the combustion characteristics. The smaller the combustor size is, the more difficult it is to maintain the steady combustion. The smallest combustor size that the stable flame can be sustained is determined mainly by the wall temperature of the micro-combustor under the given conditions. The higher the wall temperature is, the smaller the smallest combustor size. Therefore increasing wall temperature is an effective way to realize flame stabilization for a given combustor size.     

Numerical simulation of the interaction between shock train and combustion in three-dimensional M12-02 scramjet model

The characteristics of combustion flow fields and performance for hypersonic M12-02 scramjet were numerically simulated and analyzed. The compressible two-equation k-w SST turbulence model was employed for the turbulence model and the 9-species, 27-reaction-step hydrogen-air reaction mechanism was used as the reaction kinetics model. The numerical method was verified and a good agreement was obtained between the results of the numerical simulations and the experimental data. The results showed that shock waves from the upper and lower walls respectively crossed with each other near the central axis, forming a ‘diamond’ shape in the high-temperature combustion region. Compared to the conventional scramjet engine, most of the fuel reaction was in pure supersonic combustion mode for this hypersonic scramjet engine. Changes in the distribution of fuel on the upper and lower walls could have an appreciable impact on the combustion flow field. Average fuel distribution between upper and lower walls is benefit for combustion enhancement while the heat transfer in the corner of the side wall is severe and should be avoided during operation. The flame investigation showed that it cannot automatically predict the flame surface temperature in advance only based on the equivalence ratio Φ according to diffusion combustion theory. Compared to Φ = 1.0 condition, the flame surface temperature for Φ = 0.8 condition is higher as the complicated interaction between shock waves and combustion, which makes the local air temperature and mixing extent in flame surface is more appropriate. However, in terms of the overall engine performance, the Φ = 1.0 condition has the better combustion efficiency along the whole flow path.     

柴油机喷雾夹角对缸内三维流场的影响

运用CFD软件对直喷柴油机燃烧室中的喷雾及燃烧过程进行数值计算,考察了不同喷雾夹角下缸内三维流场及NOx排放的差异,并将计算结果进行了对比分析。结果表明喷雾夹角的增加使凹坑内的空气利用率变差,并使得燃烧高温区域更加接近气缸壁面以及缸盖平面;喷雾夹角的减小使燃烧过程中生成的NOx排放增加并增加了喷油器的热负荷。     

负荷变化对900 MW超临界锅炉炉内燃烧影响的数值模拟

利用Fluent软件对1台900 MW四角切圆燃烧锅炉在不同负荷下炉内燃烧过程进行了数值模拟,分析了负荷变化对炉内流动和传热的影响规律.结果表明:在高负荷工况下运行时,炉内燃烧充分且稳定,但是炉内火焰更容易冲刷水冷壁,可能发生局部结渣现象;在低负荷工况下运行时,炉内火焰充满度较差,切圆燃烧的稳定性显著下降,炉膛水冷壁灰污表面温度也相应降低,水冷壁表面结渣的倾向弱化,沿高度方向水冷壁吸热不均匀性增大.由于该锅炉的低NOx燃烧器采用了分离燃尽风,使得高温区扩展,火焰中心高度比采用有关标准推荐的方法计算所得结果高4~5 m.