燃气镁合金熔化炉内气相燃烧过程的三维数值模拟

对燃气镁合金熔化炉内的三维湍流气相燃烧场特性进行了数值模拟,湍流模型采用了标准k-ε双方程模型,湍流燃烧采用有限速率/涡耗散模型,辐射换热P1模型,数值方法采用SIMPLE算法,实现了燃烧过程的数值再现,特别考察了烧嘴位置和入口流量速度因素对炉内温度场和流动场的影响,并为熔化炉的结构设计提供了一些合理化建议,为其实际运行提供了有益的参考价值。     

高温空气燃烧燃气热态试验炉非稳态数值模拟

采用双方程湍流模型、概率密度函数(PDF)燃烧模型和离散坐标(DO)辐射模型，对采用高温空气燃烧技术的燃气热态试验炉炉内工况进行了非稳态数值模拟，预测热态试验炉运行时的炉内温度场、组分场和速度场，由数值模拟结果分析比较了不同喷口间距五喷口燃烧器对炉内工况的影响，为采用高温空气燃烧技术的燃气燃烧器设计提供参考。     

步进式加热炉内热工过程的数值模拟

建立步进式加热炉内流动、燃烧和传热的数学模型.炉内流场的模拟采用κ-ε双方程模型,辐射换热计算采用P-1辐射模型,气相燃烧采用Species Transport模型,流场计算采用Simpler算法.采用上述模型与算法得到了炉内详细合理的温度、速度和浓度分布,并对其中影响板坯加热的温度场进行了试验验证.     

煤粉复合旋流火焰燃烧特性研究（2）：数值模拟

本文数值模拟了煤粉旋流火焰燃烧过程，燃烧数值计算包括理论物理模型建立，数值方法两个大部分，计算模型处理了气相湍流与燃烧、气固两相流动、煤颗粒燃烧过程和辐射传热等物理化学过程，以ｋ－ε模型模拟湍流流动；ＰＤＦ法模拟气相扩散火焰燃烧；颗粒运动计算颗粒运动少颗粒湍流浓度方程模拟颗粒湍流扩散；通量法计算火焰辐射传热，煤粉颗粒复杂燃烧模型计算了颗粒尺寸、形状变化和颗粒孔隙内部燃烧、表面平度对整个颗粒的燃烧过程影响。计算获得了气相速度分布场、气相ｋ和ε分布场、气相温度场、气相组份场和颗粒浓度场及运动过程，揭示了煤粉复合旋流燃烧特性。     

四角切向燃烧锅炉炉内流动过程数值模拟

本文介绍四角切向燃烧锅炉炉内流动过程的数值模拟方法,三维湍流气相流场通用计算方法、计算对象的进、出口边界条件、固体壁面条件及近壁面处理技巧.利用所开发的炉内三维湍流气相流场数值计算程序,对焦作电厂3号炉进行实例计算.计算结果较准确地预测了炉内实际流动情况.     

新型蓄热式镁还原炉内流场的数值模拟

用大型软件fluent,采用-双方程模型对新型炼镁炉内湍流流场进行数值模拟,分析了炉内气体扩散过程、流场分布以及炉内流场对燃烧过程的影响。结果表明,这种新型的镁还原炉可以获得很好的流场来满足镁还原工作要求。     

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.     

圆形铝熔炼炉内非稳态热工过程数值模拟

针对铝熔铸过程中常用的圆形铝熔炼炉,利用FLUENT软件,根据能量守恒方程、动量方程建立铝熔炼炉内热工过程数学模型,采用标准k-ε湍流模型、P-1辐射模型对铝熔炼炉内非稳态传热及流动过程进行数值模拟研究。考虑到铝料熔化过程会消耗一部分能量,采用等效比热法将铝料的熔化潜热转换为相应的比热值进行计算。通过数值模拟得到了炉内流场、炉膛及铝料温度场分布情况。模拟结果与实际情况相符,为铝熔炼炉的设计与优化研究提供了理论依据。     

600MW超临界W火焰锅炉燃烧特性及水冷壁分布参数混合模拟

以东方锅炉600MW超临界W火焰锅炉为研究对象,从非预混燃烧、气相湍流、颗粒相轨道模型、辐射传热、煤粉挥发分燃烧等模型入手,运用计算流体力学软件FLUENT进行了计算流体力学(CFD)模拟,同时建立了炉膛水冷壁一维分布参数模型,将其得到的水冷壁温度分布作为CFD模拟的边界条件,通过两种模型的混合模拟,得到了更为准确的基础工况和变负荷工况下炉膛内温度场、流场、组分浓度场的分布特性,并分析了炉内煤粉燃烧规律的变化。     

电弧等离子体点火器湍流燃烧流场传热与流动数值模拟

对燃气轮机燃烧室电弧等离子体点火器内湍流燃烧流场,进行了传热与流动数值模拟。采用了RNGk-ε湍流模型、扩散燃烧模型和离散传播辐射DTRM模型。计算域包括点火器内的等离子体发生器和点火器主体。将计算结果与未考虑辐射的温度场和流场进行了比较。结果表明辐射模型对其温度场有影响,对速度场影响不大;在点火器出口处的径向温度分布是均匀的。     

多流体模型在燃气轮机燃烧室三维反应流中的应用

对一种模型燃气轮机燃烧室中的三维反应流进行了数值模拟，模型燃烧室的燃料是CH4，燃烧类型是预混燃烧，在数值模拟过程中，采用了Spalding于1995年提出来的多流体模型来对燃烧室中的湍流预混燃烧进行了数值模拟，在数值模拟过程中考虑了辐射问题，采用了六通量辐射模型。通过数值模拟给出了速度，压力，湍流脉动动能，湍流动能耗散率，焓值，湍流粘度，温度，密度，燃烧产物质量分数，氧的质量分数，燃料/空气混合比，燃料质量分数，空间三个方向的辐射热通量以及各种流体的质量分数等变量的分布情况，此外，还采用传统的旋涡破碎模型对此燃烧室进行了数值模拟，并对两种方法的结果进行了分析比较，由分析可以看出多流体模型的结果接近于实际情况，对模型燃烧室进行三维反应流数值模拟的工作为今后对实际燃烧室反应流的数值模拟打下了一定的基础。     

Numerical study of radiative heat transfer effects on a complex configuration of rack storage fire

This work describes the application and the performance of a new radiation model in CFD calculations for the simulation of thermal radiation transfer effects on a fire scenario. A 3D Cartesian coordinates radiative heat transfer procedure based on coupling of the FTn finite volume method (FTnFVM) with the bounded high-order resolution CLAM scheme is developed. The narrow-band based weighted-sum-of-gray-gases (NB-WSGG) model is applied to take account of nongray effects by CO₂, H₂O and soot. To treat irregular boundaries, the present model used the blocked-off-region procedure. This radiation code is implemented in the Fire Dynamics Simulator (FDS), a Computational-Fluid-Dynamics-based fire model, where a the combustion is represented by means of the mixture fraction with a single step chemical reaction model and the Large Eddy Simulation (LES) is used to model the dissipative processes. Computational results with and without radiation effects are compared against available experimental data and quasi-steady state law correlations of in-rack storage fire, which consists a complex configuration of double tri-wall corrugated paper cartons placed onto a wood pallet. Sensibility analyses of spatial and angular grids demonstrate the improvements due to the FTnFVM and to the CLAM scheme in the configuration studied. Results show that the simulations of the flame height, the gas temperature and the gas velocity are strongly influenced by thermal radiation. Overall, simulations predicted closer profiles to the experimental results only when the nongray-sooting radiation model was incorporated and an over-prediction of the gas temperature and the flame height is found when radiation is neglected. A sensibility analysis has shown that the flame characteristics are strongly affected by the soot yield.     

气体热辐射机理的研究与热辐射特性的计算

从对气体热辐射的微观机理的研究出发，利用谐振子模型对气体燃烧产物的热辐射特性进行了研究与计算，结果表明：气体的热辐射波谱取决于气体分子的固有振动频率、等离子体频率、阻尼系数以及气层厚度，提高压力、气层厚度和降低温度可以有效地改善气体热辐射的选择性。     

A theoretical framework for calculating full-scale jet fires induced by high-pressure hydrogen/natural gas transient leakage

Previous experimental results on full-scale jet fires induced by high-pressure hydrogen/natural gas transient leakage can only be suitable for solving practical engineering problems, or testing the limitation of previous models. Thus, this paper presents a theoretical framework for the high-pressure hydrogen/natural gas leakage and the subsequent jet fire. The proposed framework consists of a transient leakage model, a notional nozzle model, a jet flame size model, a radiative fraction correlation and a line source radiation model. The framework is validated by comparing the model predictions and experimental measurements of mass flow rate, total flame height and thermal radiation field of hydrogen, natural gas, hydrogen/natural gas mixture jet fires with a flame height up to 100 m. The comparison shows that the theoretical framework can give considerable predictions to properties of full-scale jet fires induced by high-pressure hydrogen/natural gas transient leakage.     

槽式太阳能真空集热管的热损失研究

建立了真空集热管中吸收管与玻璃管之间热辐射和残余气体热对流、玻璃管与外界环境之间热对流和玻璃管对天空热辐射的数学模型,提出了模型的计算方法,并通过和实验数据的比较验证了模型的准确性。同时利用模型分析了几种影响热损失的主要因素,分析结果表明:吸收管温度越高,热损失越大;环境温度越低,风速越大,热损失越大,但影响很小;选择性吸收涂层的发射率是影响热损失的主要因素;真空度对热损失也有很大影响。     

灰气体加权和模型的发展综述

气体辐射特性的准确计算对辐射换热过程的分析有重要影响。国内外学者对气体辐射特性模型中的灰气体加权和模型(WSGG)和与k分布法相关的模型进行了大量研究,本文对WSGG模型发展现状以及存在的问题进行了总结分析。针对WSGG模型具有效率高、精度低的特点,而k分布法精度高可以弥补其不足,认为可以将k分布法引入WSGG模型,建立一种快速准确且能与任意辐射传递方程求解方法兼容的气体辐射特性计算模型。     

Mixed Convection and Non-Gray Radiation in a Horizontal Rectangular Duct

Numerical studies for fluid flow and heat transfer in a horizontal rectangular duct are carried out. The flow is considered to be laminar, hydrodynamically and thermally developing. Heat transfer by both forced and natural convection is taken into account. The radiation from the gas is modeled with weighted sum of gray gases (WSGG) model. While considering non-gray radiation with WSGG, the fluid is considered to be a mixture of CO₂ and H₂O. Simulations are carried out with lower wall temperature than the inlet temperature of the gas. The effect of buoyancy and radiation on bulk mean temperature and Nusselt number are studied. The effects of temperature dependent properties are discussed. Comparative studies are carried out among forced convection, mixed convection, gray and non-gray gas radiation. It is found from the simulations that the assumption of gray gas can produce an error of ±10% over a non-gray model with WSGG for the cases studied.     

Transient numerical analysis of a multi-layered porous heat exchanger including gas radiation effects

Thermal characteristics of a new type of multi-layered porous heat exchanger (PHE) are identified in the present study. This system works based on the energy conversion between gas enthalpy and thermal radiation. It has a five-layered structure consisting of two high temperature, two heat recovery and one low temperature sections. These sections are separated from each other by four quartz glass windows. In the two high temperature sections, the enthalpy of high temperature gas flow is converted to thermal radiation that is emitted toward the three adjacent layers where the low temperature air flows are effectively heated by the reverse conversion from thermal radiation into gas enthalpy. The gaseous radiation is also considered, such that in each section, a transient theoretical analysis is conducted for a one-dimensional system where convection, conduction and radiation take place simultaneously in both gas and solid phases. The coupled energy equations for the gas flows and porous layers based on the two-flux radiation model are solved numerically to identify the transient heat transfer characteristics of the system. It is shown that this type of porous heat exchanger has a very high efficiency especially when the porous layers have high optical thicknesses.     

Assessment of gas radiative property models in the presence of nongray particles

In this study, a radiation code based on the method of lines solution of the discrete ordinates method for the prediction of radiative heat transfer in nongray gaseous media is developed by incorporation of two different spectral gas radiative property models, banded spectral line-based weighted sum of gray gases (banded SLW) and gray wide band (GWB) approximation in the presence of nongray absorbing–emitting–scattering particles. The aim is to introduce an accurate and CPU efficient spectral gas radiation model, which is compatible with spectral fuel/ash particle property models. Input data required for the radiation code and its validation are provided from two combustion tests previously performed in a 300 kWt atmospheric bubbling fluidized bed combustor test rig burning low calorific value Turkish lignite with high volatile matter/fixed carbon (VM/FC) ratio in its own ash. The agreement between wall heat fluxes and source term predictions obtained by global and banded SLW models reveal that global SLW model can be converted to an accurate wide band gas model (banded SLW) which can directly be coupled with spectral particle radiation. Furthermore, assessment of GWB approximation by benchmarking its predictions against banded SLW model shows that GWB gives reasonable agreement with a higher CPU efficiency when the particle absorption coefficient is at least in the same order of magnitude with the gas absorption coefficient.     

箱带模型结合DOM在非灰气体辐射换热计算中的应用

在总结现有计算非灰气体辐射特性的各种模型与方法的基础上，利用箱带模型与离散坐标法(DOM)相结合的方法计算了一维无限大平行平板间气体介质在均匀型、边界层型及抛物型三种温度分布下的辐射换热。研究表明，箱带模型与常用的统计窄带模型或指数宽带模型的灰带近似计算结果相比具有较好的准确性，且由于箱带模型具有简单、易于编程、计算速度快等优点，对一些较为复杂的工程计算问题是一种较好的可供选择的模型。