直喷式柴油机缸内热辐射多区(多维)模型的研究

以准维现象学多区喷雾燃烧模型和碳粒生成预测了模型为基础,建立了缸内空间辐射多区（多维）模型,并以Ｇ４１３５直喷式柴油机为研究对象,用蒙特卡洛（Ｍｏｎｔｅ－Ｃａｒｌｏ）法计算和分析了燃烧室壁面辐射热量的分布,结果表明,热流量分布规律和数值与柴油机缸内燃烧过程,有关试验结果相符。     

研究直喷式柴油机碳粒排放及缸内辐射传热的一种数学方法

本文给出了预测直喷式柴油机碳粒排放及碳粒和气体辐射传热的实用化数学模型。该模型以多区燃烧模型为基础,通过补充各区的碳粒和气体浓度,碳粒和气体发射率等的计算子模型,使程序功能获得扩大。用这个模型对一台实际柴油机不同喷油正时下的碳粒排放作预测,结果与实测值相吻合。本文还给出了预测和部分实测的低散热柴油机碳粒排放及碳粒和气体辐射传热的变化结果。在低散热柴油机中,碳粒排放将下降,但辐射传热量与总传热量之比会增加。     

基于火焰辐射图像的温度分布与浓度分布联合重建

讨论了基于火焰辐射图像的截面温度分布和碳粒浓度分布的重建测试方法。分析并建立了测试系统理模型和优化模型，设计了相应的求解算法，针对电站锅炉燃煤火焰进行了实际测试。计算结果与实际测试结果进行比较和分析，温度分布和浓度分布与模型重建结果比较接近，表明重建结果合理、可信。     

预测柴油机气缸内火焰辐射传热的一个单区模型

建立了一个以压力示功图为基础来计算柴油机气缸内火焰辐射传热的一个单区模型,利用该模型对一台直喷柴油机气缸内火焰辐射热流量随曲轴转角变化情况进行了计算,并计算结果与实测结果进行了比较,表明该模型能较好预测所缸内火焰辐射传热量,在工程上有应用价值。     

用光导纤维多色法对柴油机燃烧室内火焰温度与碳粒生成的研究

本文介绍了作者研制的分叉光导纤维４色法测量装置和采用它对直喷式４１３５型柴油机燃烧室内火焰温度和碳烟浓度测量的结果。以双色法为基础的４色法，通过数学方法可优化试验结果，减小测量误差。测量结果表明：在燃烧过程中，碳粒生成时间落后于温度上升时间，持续高温产生碳粒高浓度，后燃烧使碳粒浓度增加。随着负荷的增加，燃烧火焰温度及碳粒浓度增加，它们持续的时间也延长。燃烧终了破粒浓度和排气烟度增大。在喷注区会产生很高的碳粒质量浓度值，稀混合气区火焰温度上升较早。过后燃烧或供油提前角减小，使燃烧终了碳粒浓度增大。     

用共轭梯度法与蒙特卡洛法求解三维系统的辐射热负荷反问题

采用蒙特卡洛法与共轭梯度法确定三维矩形炉膛中燃烧器或加热表面的温度分与热负荷分布。讨论了测量误差对计算结果的影响，结果表明：当测量值不含误差时，用共轭梯并法计算得到的加热表面的温度值和热流量值与其真实值吻合很好。实验测量误差对计算精度的影响与加热表面及受热表面之间的辐射热交换系数有关，辐射热交换系数越大，测量误差对计算结果的影响越大。     

CO火焰对碳粒燃烧影响的理论分析和实验研究

建立了球坐标系下传热、传质和化学反应全耦合的碳粒燃烧数值模拟程序．在详细理论计算的配合下，通过精密设计的实验研究，用FTIR透射-发射实验测温方法成功捕捉了持续时间极短的“CO在颗粒表面被点燃而引起的颗粒高温”现象．连续膜模型的计算结果和FTIR测温实验结果表明，CO的空间反应与碳粒表面反应的相互作用及其对碳粒表面温度、总体反应速率的影响是极其复杂的．而CO能否在颗粒表面附近被点燃及其所引起的颗粒表面温度差可高达数百度．在实际煤粉火焰条件下，单膜模型和严格的连续膜模型的预报结果相差比较大，特别是对着火点及着火后某段区间内的颗粒温度的预报，是仅考虑表面氧化反应C＋1／2 O2→CO的单膜模型所无法完成的，这说明单膜模型存在较大的应用局限性．     

三维离散传播辐射模型的理论及数值分析

本文比较详细地阐述了三维离散传播热辐射模型的理论，并且编制了相应的数值模拟程序，运用该程序对三维立方腔体中的两种辐射传热问题进行了数值模拟，所得模拟结果与精确解吻合较好，这表明三维离散传播热辐射模型是目前解决辐射问题中热流量和温度分布的一种较好的方法。     

柴油机缸内碳烟颗粒形成过程与尺寸分布特性

采用了唯象的半经验碳烟排放模型,考虑了碳粒成核、表面成长、凝结和氧化的基本过程,模拟计算了柴油机缸内燃烧条件下缸内碳烟形成过程中的活性基核、碳粒核的生成规律及碳粒尺寸分布规律,并对碳烟排放进行了分析。计算结果表明:燃烧温度和混合物当量比对初始碳核的生成有很重要的影响,碳核粒子首先在活塞凹坑底部的浓混合区域生成,随燃烧的扩散过程,燃烧室中心位置和凹坑唇边挤流区相继出现较高浓度的基核,但存在浓度相位差,缸内不同位置生成碳粒数量和尺寸分布是不同的,不同尺寸范围的碳粒数量和质量之间存在对应关系。     

强迫对流条件下碳粒燃烧速率的研究

本文对强迫对流条件下碳粒的烧过程提出了一个简化模型。在此基础上对碳粒的燃烧过程进行了数据模拟，求出了不同工况下碳粒的燃烧速率，并给出了碳粒边界层内的浓度分布和温度分布。与实验结果的对照表明，该模型在Ｒｅ＜２００时是合理的。     

Numerical investigation of combustion with non-gray thermal radiation and soot formation effect in a liquid rocket engine

A numerical analysis was carried out in order to investigate the combustion and heat transfer characteristics in a liquid rocket engine in terms of non-gray thermal radiation and soot formation. Governing gas and droplet phase equations with PSIC model, turbulent combustion model with liquid kerosene fuel, soot formation, and non-gray thermal radiative equations are introduced. A radiation model was implemented in a compressible flow solver in order to investigate the effects of thermal radiation. The finite-volume method (FVM) was employed to solve the radiative transfer equation, and the weighted-sum-of-gray-gases model (WSGGM) was applied to model the radiation effect by a mixture of non-gray gases and gray soot particulates. After confirming the two-phase combustion behavior with soot distribution, the effects of the O/F ratio, wall temperature, and wall emissivity on the wall heat flux were investigated. It was found that the effects of soot formation and radiation are significant; as the O/F ratio increases, the wall temperature decreases. In addition, as the wall emissivity increases, the radiative heat flux on the wall increases.     

处理辐射传热的一个新热流数学模型

本文从处理辐射传热的基本理论出发，给出了一个包含与辐射发射随机方向性有关的比热流参数的新热流模型。该模型克服了原热流模型在理论简化上的缺陷，能够更好地反映炉内的实际情况。同时给出了用Ｍｏｎｔｅ－Ｃａｒｌｏ方法求解比热流参数的计算程序。最后用该模型求解了实验室用马弗炉内的温度分布，同时用原热流法对该高温炉的温度分布进行了计算，与实验结果相比较，新热流方程明显优于原热流方程。     

Numerical Study of the Swirl Effect on a Coaxial Jet Combustor Flame Including Radiative Heat Transfer

A numerical study of the swirl effect on a coaxial jet combustor flame including radiative heat transfer is presented. In this work, the standard k-ε model is applied to investigate the turbulence effect, and the eddy dissipation model (EDM) is used to model combustion. The radiative heat transfer and the properties of gases and soot are considered using a coupled of the finite-volume method (FVM), and the narrow-band based weighted-sum-of-gray gases (WSGG-SNB) model. The results of this work are validated by experiment data. The results clearly show that radiation must be taken into account to obtain good accuracy for turbulent diffusion flame in combustor chamber. Flame is very influenced by the radiation of gases, soot, and combustor wall. However, swirl is an important controlling variable on the combustion characteristics and pollutant formation.     

Simulation of Combustion Space Heat Transfer of Glass Melting Furnace

Radiation plays a dominant role in combustion space heat transfer. It is composed of three components, namely gaseous species radiation, soot radiation and crown surface radiation. The basis for model validation and the subsequent study of furnace operation is the spatial variation of radiant heat flux. Hayes and colleagues carried out measurements of crown incident radiant heat flux along the furnace axial centerline and developed a numerical model. However, the effect of soot was not quantified. In the present work, a numerical model is developed which considers the effect of soot radiation and is simulated using Fluent. The proposed model fits the experimental data of Hayes and colleagues within an error band of –6% to +14%.     

Performance Evaluation of Two Heat Transfer Models of a Walking Beam Type Reheat Furnace

Two different heat transfer models for predicting the transient heat transfer characteristics of the slabs in a walking beam type reheat furnace are compared in this work. The prediction of heat flux on the slab surface and the temperature distribution inside the slab have been determined by considering thermal radiation in the furnace chamber and transient heat conduction in the slab. Both models have been compared for their accuracy and computational time. The furnace is modeled as an enclosure with a radiatively participating medium. In the first model, the three-dimensional (3D) transient heat conduction equation with a radiative heat flux boundary condition is solved using an in-house code. The radiative heat flux incident on the slab surface required in the boundary condition of the conduction code is calculated using the commercial software FLUENT. The second model uses entirely FLUENT along with a user-defined function, which has been developed to account for the movement of slabs. The results obtained from both models have a maximum temperature difference of 2.25%, whereas the computational time for the first model is 3 h and that for the second model is approximately 100 h.     

马蹄形火焰玻璃熔窑燃烧空间流动与传热的数值模拟

对马蹄形火焰玻璃窑炉燃烧空间内的流动、燃烧及辐射传热等过程进行了数值模拟研究,得到了炉内燃烧空间的速度场、温度场、组分浓度分布及燃烧空间向玻璃液面传递的热流分布。探讨了燃烧空间入口的进气角度对炉内温度场和向玻璃面传递的热流的影响,模拟结果表明,当入口的进气角度在5°～10°之间时,传热效果较好。     

Radiative and conductive transfer for a real gas in a cylindrical enclosure with gray walls

The purpose of this study is to examine the interaction of radiative and conductive transfer for a radiatively participating real gas stagnant in a cylindrical enclosure with gray diffuse walls. Consideration of reflecting boundaries represents an extension of previous black wall studies. Examination of radiative transfer was made by the zone method with gas radiative properties furnished by the weighted sum of gray gases model. Directed flux areas are expressed as the weighted sum of gray gas total exchange areas which are evaluated using the matrix formulation method from direct exchange areas. Axial and radial gas temperatures are examined along with wall heat flux or temperature for respective cases of either specified wall temperatures or heat fluxes. Emphasis is placed on examining results to show the effects of wall emittance and duct diameter. Results for heat generation within the gas are also presented.     

A Comparison of Angular Discretization Strategies for Modeling Radiative Transfer in Pool Fire Simulations

Decoupled radiative heat transfer calculations of 30-cm-diameter heptane pool fire are carried out employing the P1, discrete ordinates (DO), and finite-volume (FV) methods. The DO calculations are performed employing three different quadrature schemes (level symmetric hybrid [LSH], spherical surface symmetrical equal dividing angular quadrature [SSD], and TN). By scaling the soot field in the fire, the performances of the various methods are evaluated at different optical thicknesses by employing highly angularly resolved FV calculations (512 directions) as a reference. Twenty-four angular directions in the DO and FV methods are seen to be adequate to accurately predict the distributions of the divergence of the radiative flux within the fire. The corresponding accuracies of the P1 model are seen to decrease with increase in optical thickness. In the regions away from the fire, the P1 model performs poorly in predicting the axial as well as the radial radiative fluxes, whereas the errors associated with employing coarse angular resolutions in the DO method are seen to increase with soot concentrations and distance from the pool centre. Among the DO and FV models, the accuracies of the axial and radial incident radiative flux predictions outside the fire were more dependent on the angular resolution of the calculations rather than on the particular quadrature set employed in the calculations.     

Monte Carlo modeling of radiative transfer in a turbulent sooty flame

The calculation of radiative transfer within a sooty turbulent ethylene-air diffusion jet flame has been carried out by using a Monte Carlo method and an accurate CK model for the gases. The influence of the turbulence-radiation interaction (TRI) has been studied. In the TRI modeling, the radiative properties of the assumed homogeneous turbulent structures are randomly obtained from a multidimensional probability density function (PDF) of the reaction progress variable, of the mixture ratio and of the soot volume fraction. This joint PDF is obtained from an Eulerian-Lagrangian turbulent combustion model and the sizes of the turbulent structures are directly derived from a k-? model. In the considered flame, the TRI effect is an increase of the radiative heat loss by about 30%. The radiative heat loss becomes almost equal to one-third of the chemical heat release. Soot particles play the most important role in the global radiative heat loss but the influence of gaseous species like CO₂ and H₂O can be important in the local energy balance.