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     

入流条件对同轴射流旋流燃烧室内湍流流动模拟的影响

应用一种新的代数Reynolds应力模型对同轴射流旋流燃烧室内两股射流为同向旋转和反向旋转条件下的湍流旋流流动进行了数值模拟。为得到合理的流场分布结果，研究了入流条件对同轴射流旋流燃烧室内湍流流动模拟结果的影响。计算中对旋流燃烧室进口处两股旋转射流的轴向与切向速度采用了均匀分布和实验测量分布两种方式来给定。将两种进口速度分布条件下得到的燃烧室内气体轴向与切向速度分布计算结果与实验数据进行了比较。     

涡旋燃烧炉正反切向进风气固流动的数值模拟

涡旋燃烧炉是最近研制的一种新型固体燃料旋风燃烧炉，它采用了多级切向进风的结构。本文应用气固两相流的多连续介质模型及其数值计算方法，针对分级供入炉内的空气采用正反切向进风的条件，对涡旋燃烧炉内的气固两相湍流旋流流动进行了数值模拟。通过模拟结果的分析及其与分级同向切向进风情况的比较，探讨了在涡旋燃烧炉中采用多级正反切向进风方式的可能性。     

Modeling of lean premixed combustion in stationary gas turbines

Lean premixed combustion (LPC) of natural gas is of considerable interest in land-based gas turbines for power generation. However, modeling such combustors and adequately addressing the concerns of LPC, which include emissions of nitrogen oxides, carbon monoxide and unburned hydrocarbons, remains a significant challenge. In this paper, characteristics of published simulations of gas turbine combustion are summarized and methods of modeling turbulent combustion are reviewed. The velocity–composition PDF method is selected for implementation in a new comprehensive model that uses an unstructured-grid flow solver. Reduced mechanisms for methane combustion are evaluated in a partially stirred reactor model. Comprehensive model predictions of swirl-stabilized LPC of natural gas are compared with detailed measurements obtained in a laboratory-scale combustor. The model is also applied to industrial combustor geometries.     

LDA在燃气轮机燃烧室流场测量中的应用

介绍了激光多普勒测速技术在燃气轮机燃烧室内部流场测试的应用，阐述了LDA的基本原理和模型燃烧室内光学路径的实现方法，同时作者利用双相位多普勒分析仪DualPDA (Cual Phase Doppler Anemometer)对模型燃烧室内部流场进行了二维冷态测试，获得了大量的原始数据，为深入研究燃烧室内部气流特性提供了实验基础。     

Simulation of Swirling Turbulent Flow and Combustion in a Combustor

An algebraic concentration moment (ACM)-PDF turbulent combustion model is proposed. It is formulated by jointly utilizing the explicit algebraic expressions for the second-order-moment of concentration fluctuation and the presumed probability density function (PDF) of gas instantaneous temperature. A set of analytical expressions for the time-averaged temperature relevant quantity is obtained for the closure of the time-averaged reaction rate. The model is applied to the simulation of turbulent flow and combustion in a swirl combustor. The calculated gas velocity, temperature, species concentrations, and turbulent fluctuating velocity are in agreement with the measured data. They are much improved over those obtained by the EBU-Arrhenius model.     

Optimization of Gas Turbine Combustor Mixing for Improved Exit Temperature Profile

In this article, a design optimization technique for mixing in a gas turbine combustor is presented. The technique entails the use of computational fluid dynamics and mathematical optimization to optimize the combustor exit temperature profile. Combustor geometric parameters were used as optimization design variables. This work does not intend to suggest that combustor exit temperature profile is the only performance parameter important for the design of gas turbine combustors. However, it is a key parameter of an optimized combustor that is related to the power output and durability of the turbine. The combustor in this study is an experimental liquid-fuelled atmospheric combustor with a turbulent diffusion flame. The computational fluid dynamics simulations use a standard k-? model. The optimization is carried out with the Dynamic-Q algorithm, which is specifically designed to handle constrained problems where the objective and constraint functions are expensive to evaluate. The optimization leads to a more uniform combustor exit temperature profile than with the original one.     

APPLICATION OF SCALAR MONTE CARLO PROBABILITY DENSITY FUNCTION METHOD FOR TURBULENT SPRAY FLAMES

Abstract

The objective of the present work is twofold: (1) extend the coupled Monte Carlo probability density function (PDF)/computational fluid dynamics (CFD) computations to the modeling of turbulent spray flames, and (2) extend the PDF/SPRAY/CFD module to parallel computing in order to facilitate large-scale combustor computations. In this approach, the mean gas phase velocity and turbulence fields are determined from a standard turbulence model, the joint composition of species and enthalpy from the solution of a modeled PDF transport equation, and a Lagrangian-based dilute spray model is used for the liquid-phase representation. The PDF transport equation is solved by a Monte Carlo method, and the mean gas phase velocity and turbulence fields together with the liquid phase equations are solved by existing state-of-the-art numerical representations. The application of the method to both open as well as confined axisymmetric swirl-stabilized spray flames shows good agreement with the measured data. Preliminary estimates indicate that it is well within reach of today's modern parallel computer to do a realistic gas turbine combustor simulation within a reasonable turnaround time. The article provides complete details of the overall algorithm, parallelization, and other numerical issues related to coupling between the three solvers.     

Influences of spray and operating parameters on penetration of vaporizing fuel droplets in a gas turbine combustor

The effects of inlet spray and operating parameters on penetration and vaporization histories of fuel droplets of a liquid fuel spray injected into a turbulent swirling flow of air through a typical can type gas turbine combustor, have been evaluated from numerical solutions of the conservation equations in gas and droplet phases. The computational scheme is based on the typical stochastic separated flow model of the gas-droplet flow within the combustor. A κ–ε model with wall function treatment for near wall region has been adopted for the solution of conservative equations in gas phase. The initial spray parameters are specified by a suitable PDF size distribution and a given spray cone angle. It has been recognized that the penetration of vaporizing droplets is reduced with an increase in inlet air swirl and spray cone angle. An increase in inlet air pressure or a decrease in inlet air temperature also results in a reduction in droplet penetration. The inlet air pressure and spray cone angle are found to be the most influencing parameters in this regard.     

Modelling of combustion performances and emission characteristics of coal gases in a model gas turbine combustor

In recent years, gas mixtures are being used as alternative fuels in combustors. These gas mixtures are obtained by different methods. For instance, coal gasification and carbonization as coal have the largest reserves among fossil fuels. Gas mixtures obtained via coal gasification and carbonization are called water gas, generator gas, town gas and coke oven gas. These fuels contain various gases. As a result of this, heating values of fuels are also different. Therefore, combustion performances and emission characteristics of these fuels need to be investigated. In this study, combustion performances and emissions including CO, CO₂ and NO_X of water gas, generator gas, town gases, coke oven gas and methane were numerically investigated in a model gas turbine combustor. The numerical modelling of turbulent nonpremixed diffusion flames has been performed in this combustor. Mathematical models used in this study involved the k–ε model of turbulent flow, the PDF/mixture fraction model of nonpremixed combustion and P‐1 radiation model. A CFD code ANSYS Fluent was used for all numerical investigations. Temperature distributions of axial and radial directions were determined. A NO_X post‐processor was used for the prediction of NO_X emissions from the gas turbine combustor. Modelling was performed for 60 kW thermal power and different equivalance ratios (i.e. Ф = 0.91, Ф = 0.77 and Ф = 0.67). The studied type 1 model gas turbine combustor was modelled for Ф = 0.91 equivalance ratio. Then, Other equivalance ratios were analysed for type 2 model gas turbine combustor. The effect of dilution air on combustion performances and emission characteristics was also investigated. It is concluded that the coke oven gas, the town gas I, town gas II and the water gas are appropriate for usage as alternative fuel, whereas the generator gas is not suitable for gas turbine combustors. Copyright © 2013 John Wiley & Sons, Ltd.     

A NEW ALGEBRAIC MASS FLUX MODEL FOR SIMULATING TURBULENT MIXING IN SWIRLING FLOW

A new algebraic turbulent mass flux model (AFM), which properly accounts for swirl–turbulence interactions, is proposed and formulated in the present article. A simplified explicit form of this new AFM is derived. By incorporating this model with the new algebraic Reynolds stress model proposed previously, a new algebraic stress/flux model (ASM/AFM) is obtained. The new ASM/AFM is applied to the simulation of swirling turbulent flow and mixing in a combustor with helium/air jet and swirling air stream. The calculated gas axial and tangential velocities, gas axial and tangential fluctuating velocities, and helium concentration are in agreement with the measured test data. Comparing with the k–? model for turbulent mass transport, the helium concentration predicted by the new ASM/AFM is much improved.     

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。     

旋流燃烧室内甲烷湍流燃烧的数值模拟

为合理考虑湍流-复杂化学反应的相互作用,建立了甲烷湍流四步反应的温度脉动简化概率密度函数(PDF)模型.应用该模型对TECFLAM燃烧室内的甲烷湍流旋流燃烧进行了数值模拟,得到了与实验相符合的气体轴向、径向与切向速度、温度、温度脉动均方根值及甲烷、氧气、二氧化碳与水蒸气质量分数分布.得到的一氧化碳和氢气质量分数分布与实验基本符合.     

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。     

湿度对HAT循环燃烧室旋流扩散燃烧特性的影响

为研究湿度对燃烧特性的影响,采用湍流雷诺应力模型和层流小火焰模型,对湿空气透平(HAT)循环燃气轮机带有旋流器的燃烧室内甲烷扩散燃烧过程进行了数值模拟对比了在4种不同空气含湿量(0、100、200、300g／kg(DA))情况下的燃烧室内部温度场、速度场以及NO组分分布的情况,分析了湿度对HAT循环燃烧室扩散燃烧特性的影响结果表明,加湿降低了整个燃烧室的温度,并使其内部温度分布更加均匀;加湿使燃烧室的NO浓度大大降低;加湿减小了回流区长度。     

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     

On characteristics of a non-reacting and a reacting turbulent flow over a backward facing step (BFS)

The turbulent reacting flow over a backward facing step shares some essential characteristics of premixed combustion occurring in a typical gas turbine combustor, while it is a simpler configuration to observe and model. For this reason and to explore the characteristics of the turbulent flow, in this study the combustion and flow dynamics in a backward facing step as a most elementary part of a combustor is studied numerically in atmospheric conditions. Two different configurations representing two laboratory devices are considered. As a first necessary step, the accuracy of predicted results is validated through the detailed comparison of numerical predictions and experimental measurements for a non-reacting flow. First, based on these non-reacting calculations, the turbulent model is selected and then the reacting simulations are done using a standard combustion model (available in CFX). Calculations are well supported with experimental data available from literature. Among the investigated turbulence models (k − ω, SST and SAS–SST), SAS–SST model showed the best agreement with the experimental data. The chosen turbulence model was used for the calculation of well documented case of turbulent flow over a backward facing step with the heated wall, showing satisfactory results compared to experimental data. For modeling of the reacting flow, the BVM combustion model was used. The predicted results using this model showed accurate results with an error about 2% on prediction of reattachment length.     

Turbulent mixing of a passive scalar in confined multiple jet flows of a micro combustor

The turbulent mixing characteristics of multiple jet flows in a micro can type combustor are investigated by means of large eddy simulation (LES). The micro combustor can be used for a micro gas turbine which is hybridized with solid oxide fuel cell. Attention is paid for a micro combustor having a circular disk baffle plate with a fuel injection nozzle in the center and oxidant injection holes allocated annularly. Downstream the baffle plate, a complex flow is produced from the interaction of multiple jet flows and study is made for three different configurations of the baffle plates resulting in different mixing pattern. From the results, it is substantiated that the turbulent mixing is promoted by complex flow fields caused by the jet flows and large vortical flow regions in the micro combustor. This is effective to accelerate the slow mixing between fuel and oxidant suffering from low Reynolds number in such a small combustor. In particular, the vortical flow region formed downstream the fuel jet core region plays an important role for rapid mixing coupled with another flow recirculation region. Discussion is made for the instantaneous and time and space averaged flow and passive scalar quantities which show peculiar turbulent flow and mixing characteristics corresponding to the different flow structures for each baffle plate shapes, respectively.     

湍流旋流扩散性燃烧温度脉动的数值模拟

气体温度的脉动直接影响到湍流中的化学反应,基于气体焓脉动均方值输运方程,给出了一种计算气体温度脉动均方值的方法.采用此方法对旋流燃烧室内湍流扩散燃烧的温度脉动特性进行了数值模拟,并将模拟结果与实验测量数据进行了对比.