分级进风旋流燃烧室内湍流燃烧的数值模拟

应用考虑湍流-化学反应相互作用的代数二阶矩-概率密度函数(PDF)湍流燃烧模型,对分级进风旋流燃烧室内两组工况下的甲烷湍流燃烧进行了数值模拟,得到的二氧化碳浓度和气体轴向脉动速度均方根值分布与实验数据相符合,得到的气体轴向和切向速度、轴向一切向脉动速度关联量、温度和氧气浓度分布与实验数据基本相符合.研究结果表明,选取适当的二次风率可以起到优化燃烧过程的作用.     

用ASOM和PDF方程模型模拟湍流射流燃烧

分别用代数二阶矩(ASOM)湍流燃烧模型和概率密度函数(PDF)输运方程模型模拟了美国Sandia国家实验室测量的甲烷-空气湍流射流燃烧,并将模拟结果与实验结果对比.结果表明,在大多数区域内,两种模型预报的平均温度、平均组分质量分数都与实验结果符合很好,考虑到ASOM模型的计算量约为PDF方程模拟计算量的1/100,因而认为ASOM模型更适合工程应用.用PDF模拟结果统计的温度和质量分数脉动的自关联,以及反应速率系数脉动和质量分数脉动的互关联,在大多数区域内与对应的时均量的梯度乘积有相似的变化趋势,因此验证了ASOM模型封闭假设的合理性。     

旋流燃烧室内丙烷湍流燃烧的数值模拟

提出并建立了丙烷湍流四步反应的温度脉动简化概率密度函数模型．应用该模型对旋流燃烧室内的丙烷湍流燃烧进行了数值模拟．计算中分别采用了Kiehne和Jones的两种丙烷四步反应机理．结果表明，基于Kiehne机理可得到与实验相符合的气体轴向与切向速度，轴向脉动速度均方根值和温度，以及氧气、二氧化碳、丙烷、一氧化碳与氢气体积分数的分布．     

二阶矩亚网格燃烧模型对射流火焰的大涡模拟

用二阶矩亚网格燃烧模型对美国Sandia国家实验室测量甲烷／空气射流火焰进行了大涡模拟(LES),与实验数据和用二阶矩输运方程湍流燃烧模型的雷诺平均(RANS)模拟结果进行了对比．LES得到时间平均的温度, 甲烷浓度以及温度脉动均方根值和实验值符合很好．LES时均值和RANS模拟结果接近,LES脉动均方根值优于 RANS模拟结果．LES瞬态结果显示了有燃烧时的拟序结构比无燃烧时的强,同时拟序结构强化了燃烧,湍流射流火焰呈皱折火焰面的状态．     

稳态湍流非预混燃烧的小火焰模拟

以甲烷/空气的湍流射流非预混燃烧为对象,建立二维稳态湍流非预混火焰的小火焰模型.利用湍流流动模型和小火焰模型耦合求解,计算出速度、混合分数、温度以及反应标量的摩尔分数在燃烧室内的分布,模拟结果表明小火焰模型能够用来描述燃烧室内燃烧机理.     

用二阶矩亚网格尺度燃烧模型对丙烷-空气旋流扩散燃烧的大涡模拟

用二阶矩(SOM)亚网格尺度燃烧模型对环缝进燃料的丙烷-空气旋流湍流扩散燃烧进行了大涡模拟(LES).模拟得到统计平均的热态3个方向的速度、湍流度、温度、丙烷、氧和CO2浓度分布,其值与实验数据符合很好.结果表明,二阶矩(SOM)亚网格尺度燃烧模型适用于大涡模拟.环缝进气使湍流脉动强度、各向异性程度和温度分布趋于均匀.     

旋流燃烧室内煤粉多相湍流流动与燃烧的数值模拟

提出了考虑湍流-颗粒反应相互作用的颗粒随机轨道模型,以此为基础建立煤粉燃烧综合理论模型并应用于旋流燃烧室内煤粉多相湍流流动与燃烧的数值模拟.模拟结果给出了气相温度场、速度场与温度脉动均方根值分布、颗粒相温度场、速度场与表观密度场以及颗粒瞬时温度与质量随时间的变化.研究表明,考虑湍流-颗粒反应相互作用对气相与颗粒相温度场的模拟结果有一定的影响,使气相温度分布与实验数据更为接近.     

甲烷/空气湍流扩散燃烧的小火焰模拟

以甲烷/空气的湍流射流扩散燃烧为基础,对通用的反应标量方程在火焰面上进行坐标变换,建立二维稳态湍流扩散火焰的小火焰模型。利用湍流流动模型、甲烷/空气半详细化学反应机理和小火焰模型耦合求解,分别计算出过量空气系数为1.2和1.4的速度在燃烧室内的分布状况以及混合分数、温度和组分的径向分布,模拟结果表明小火焰模型能够用来描述燃烧室内燃烧机理。     

湍流预混燃烧的小火焰模型

由Level set方法确定湍流预混燃烧火焰面的位置,考虑CHEMKIN库详细化学反应机理,通过PDF方法建立湍流预混燃烧数学模型,计算组分浓度和温度在火焰内部分布。以矩形突扩燃烧室为例,模拟甲烷/空气预混燃烧的平均火焰位置和火焰内部温度、浓度分布,计算结果与实验结果吻合良好,表明此模型能较好模拟湍流预混燃烧。     

浮力对湍流旋流火焰影响的数值模拟

采用浮力修正的k-ε湍流模型和涡团耗散（EDC）湍流燃烧模型,对旋流燃烧室内具有不同初始切向动量或旋流数的受浮力作用的甲烷湍流火焰进行了数值模拟,得到三组工况下的气体温度场、组分体积分数场、速度场和湍流脉动特性的分布,并与试验测量数据进行了比较.结果表明：浮力对初始切向动量或旋流数较高的湍流火焰有更强的影响.     

Simulation of swirl-stabilized turbulent partially premixed combustion

Properly describing turbulence-complex reaction interactions is crucial for predicting turbulent combustion and pollutant emission. A presumed probability density function model for temperature fluctuation is adopted in the present paper. It incorporates a 25-step skeletal mechanism for methane combustion. The gas turbulent transport is simulated with the algebraic Reynolds stress model for turbulence-swirl interactions. These models are applied to the simulation of swirl-stabilized turbulent partially premixed jet flame. The calculated gas velocities, fluctuating velocities, Reynolds shear stresses, temperature, and species mass fractions are in agreement with the measured test data.     

Numerical study on supersonic combustion of hydrogen and its mixture with Ethylene and methane with strut injection

In this paper, supersonic combustion and flow field of hydrogen and its mixture with ethylene and methane from strut injections in a Mach 2 supersonic flow are studied numerically. The fuel mixture of hydrogen, methane and ethylene represents the major products of pyrolysis of hydrocarbon fuels with large molecules such as kerosene as it acts as coolant and flows through cooling channels and absorbs heat. Detached Eddy Simulation with a reduced kinetic mechanism and steady flamelet model are applied to simulate turbulent combustion. The calculated temperature profiles of hydrogen are compared to the experimental results of DLR supersonic combustor for validation of the present numerical method. The supersonic combustion flows associated with shock waves, turbulent vortices and flame structures are studied. With addition of methane and ethylene, the flame zone moves further downstream of the strut and the maximum flow temperature at chamber exit decreases by 200 K. With analysis of total temperature ratios, it is found that combustion efficiency for hydrogen combustion is 0.91 and it decreases to 0.78 for the fuel mixture. The calculation of ignition delay time and flame speed reveals that fuel mixture of hydrogen and hydrocarbons has considerably larger delay time and smaller flame speed, that contributes to the weakened flame zone and lower combustion efficiency.     

Experimental analysis of the effects of hydrogen addition on methane combustion

This paper presents gas emissions from turbulent chemical flow inside a model combustor, for different blending ratios of hydrogen–methane composite fuels. Gas emissions such as CO and O₂ from the combustion reaction were obtained using a gas analyzer. NOx emissions were measured with a NOx analyzer. The previously obtained flame temperature distributions were also presented. As the amount of hydrogen in the mixture increases, more hydrogen is involved in the combustion reaction, and more heat is released, and the higher temperature levels are resulted. The results have shown that the combustion efficiency increases and CO emission decreases when the hydrogen content is increased in blending fuel. It is also shown that the hydrogen–methane blending fuels are efficiently used without any important modification in the natural gas burner. Copyright © 2011 John Wiley & Sons, Ltd.     

钝体燃烧的数值模拟

钝体燃烧模拟考虑湍流和燃烧相互耦合。在标准κ-ε两方程模型下分别采用非预混燃烧模型中化学平衡、稳态小火焰和瞬态小火焰模型,研究不同燃烧模型对组分、温度场以及流场分布的影响。数值模拟结果表明,上述燃烧模型模拟的结果与前人研究成果存在不同程度的差异,稳态小火焰模型优于其它模型,但模拟该燃烧器的燃烧模型尚需进一步完善。     

钝体驻定湍流扩散火焰局部熄火的PDF模拟

用标量联合的概率密度函数(PDF)方法对钝体驻定的湍流射流扩散Sydney火焰HM3进行数值模拟,速度场用一个修正的LRR-IP雷诺应力模型求解.采用3种不同层次的甲烷反应动力学机理对火焰的宏观结构和熄火特征进行比较研究,并结合当地自适应建表方法加速化学反应计算.结果表明,计算值和实验数据吻合较好,在回流区内,不同反应机理的预测值差别不大,但在"颈部"区域,C2机理相对C1机理可以更准确地模拟标量场的变化和局部熄火现象.     

Numerical simulation of turbulent combustion in porous materials

This paper presents one-dimensional simulations of combustion of an air/methane mixture in porous materials using a model that explicitly considers the intra-pore levels of turbulent kinetic energy. Transport equations are written in their time-and-volume-averaged form and a volume-based statistical turbulence model is applied to simulate turbulence generation due to the porous matrix. Four different thermo-mechanical models are compared, namely Laminar, Laminar with Radiation Transport, Turbulent, Turbulent with Radiation Transport. Combustion is modeled via a unique simple closure. Preliminary testing results indicate that a substantially different temperature distribution is obtained depending on the model used. In addition, for high excess air peak gas temperature is reduced and the flame front moves towards the exit of the burner. Also, increasing the inlet flow rate for stoichiometric mixture pushes the flame out of the porous material.     

Numerical study on high-temperature diluted air combustion for the turbulent jet flame in crossflow using an unsteady flamelet model

The turbulent jet flame in a crossflow with highly preheated diluted air has been numerically investigated. The Favre-averaged Navier–Stokes equations are solved by a finite volume method of SIMPLE type that incorporates the flamelet concept coupled with the standard k–ε turbulence model. The NO formation is estimated by using the Eulerian particle transport equations in a postprocessing mode. For methane and propane with various conditions of inlet air temperature and oxygen concentration, the three-dimensional characteristics of the flame are successfully captured. The jet-flame trajectory is in remarkably good agreement with the existing cold-flow correlations. When the oxygen concentration is high, the maximum flame temperature becomes high and the two fuels show quite different characteristics in the downstream region. On the other hand, for low oxygen concentrations, the temperature difference between the two fuels is relatively small and remains fairly constant throughout the combustion chamber. The propane gives a higher NO formation compared to the methane especially when the oxygen concentration is high. A higher temperature, longer residence time of the combustion gases may be responsible for the higher thermal NO formation.