【作者】 蔡文祥；

【导师】 张靖周；

【作者基本信息】 南京航空航天大学 ， 工程热物理， 2007， 博士

【摘要】 本文在任意曲线坐标系下,发展了一套可选用不同数学模型的环形燃烧室三维两相化学反应流场的可视化计算程序。使用该程序分别对双级径向涡流器环形燃烧室火焰筒冷态流场,双圆筒头部火焰筒以及带扩压器、涡流杯、火焰筒和内外环冷却通道的回流环形燃烧室等两相燃烧流场与燃烧性能进行计算。采用型线定点与TTM相结合的方法对上述三种计算对象生成三维贴体网格,供燃烧室流场计算用。气相采用Euler方法处理,并分别用标准k-ε、RNG k-ε和代数应力(ASM)等三种紊流模型模拟紊流流动;用EBU-Arrhenius、二阶矩-EBU紊流燃烧(SOM-EBU)与扩展EBU-Arrhenius等三种紊流燃烧模型计算紊流燃烧速率;采用六通量法与离散坐标(DO)等两种辐射模型模拟燃烧室辐射传热过程。液相采用Lagrange法处理,分别用颗粒群轨道和随机颗粒轨道等两种两相流动模型描述油珠群运动轨迹及其变化历程。本文按简化四步反应与污染物生成模型预估燃烧室内污染物生成速率,并提出以回流区平均温度变化率为判断依据的燃油推进法来估算燃烧室的贫油熄火极限。本文导出在三维非正交曲线坐标系下代数应力紊流模型(ASM)以及离散坐标(DO)辐射模型的表达式。在非交错网格体系下,分别用混合差分与QUICK差分格式对气相控制方程进行离散,两相之间的耦合采用PSIC算法处理,并用SIMPLE与PISO两种算法对离散方程进行求解。最终将上述各种数学模型与数值方法集成到环形燃烧室两相反应流场数值模拟可视化计算程序。本文数值分析不同数学模型对环形燃烧室三维两相化学反应流场的影响,并把所得计算结果与实验数据进行比较。研究结果表明:虽然本文所用的各种数学模型都可用来预估燃烧室两相燃烧流场,但是不同的模型所得的燃烧室流场不全相同。其中RNG k-ε模型与ASM模型相比,虽然计算精度稍低些,但计算简单,工作量较小,故RNG k-ε模型更适合工程应用。扩展EBU-Arrhenius模型因考虑了紊流与反应尺度对化学反应速率的影响,更适合模拟两相反应流动。而SOM-EBU模型虽考虑脉动参数对反应速率的影响,但该模型计算工作量要比扩展EBU-Arrhenius模型稍大些。与热通量辐射模型相比,DO辐射模型可以考虑各种不同离散方向以及散射对辐射热交换的影响,故该模型可以更合理地估算辐射对燃烧室壁温和气流温度分布的影响。为了验证数学模型和计算方法,本文还采用激光多普勒测速仪(LDV)对双级径向涡流器直流环形燃烧室火焰筒冷态流场进行测量,并把所得的实验数据与用不同紊流模型所得的计算结果进行比较。此外,还把双圆筒头部火焰筒以及回流环形燃烧室的出口温度分布与熄火特性的计算值与实验数据进行对比,结果表明本文所用的数学模型与计算方法合理,编制相应的计算机程序可靠,可为环形燃烧室的研制和优化设计提供有用依据更多还原

【Abstract】 In this paper, a computer code with various mathematical models is developed to simulate three-dimensional two-phase reacting flowfield as well as combustion performance for three different annual combustors, including two-stage radial swirler annual combustor, two cylindrical head annual combustor and reverse-flow annual combustor with a diffuser, swirler cup, annular linner and two cooling passages and transition duct in arbitrary curvilinear coordinates. The integrated grids of combustor are generated by the method of TTM with the grid obstacle method for the complex geometric configuration. In order to model the complicated interactions between the gas and liquid phase, a Lagrangian-Eulerian two-phase flow prediction algorithm is adopted in which the gas phase is calculated in an Eulerian frame of reference whilst a separate calculation is performed for the liquid phase in a Lagrangian frame of reference. In this code, the k-ε, RNG k-εand ASM turbulent models are respectively used for turbulence modeling, EBU-Arrhenius, SOM-EBU and extended EBU-Arrhenius turbulent combustion models are adopted to determine the rate of reaction. The six-flux and discrete-ordinate (DO) radiation models are used to predict the radiant heat transfer in combustion chambers. The particle trajectory model and stochastic particle trajectory model are applied to simulation the droplet trajectories,size and temperature history. Four-step chemical reaction mechanisms combined with pollution formation models are used to estimate pollutant emission.In arbitrary curvilinear coordinates, the expressions of ASM turbulent model and DO radiation model are derivated here. A extended EBU-Arrhenius model,considering influence of the reaction scale and the turbulence scale on the reaction rate,is presented for more accurate calculation gas temperature distributions. Base temperature variation rate of recirculation zone, the fuel step-by-step method is presented to estimate the lean blowout of annular combustors.The Hybrid or QUICK difference schemes over the control volume are used to obtain the finite difference equaeions. On the non-staggered grid system, the discretization equations are solved with SIMPLE or PISO algorithm, and the couple of the gas and the liquid phase is carried out by the PSIC method. Above models and methods are integrated in the visualization program for researching reverse flow type conbustor.The influences of various mathematical models on two-phase combustion integrated flow fields in annular combustors are predicted. Predictions are in reasonable agreement with the measurements and it indicates that the k-εand RNG k-εturbulent models are more appropriate to engneering applications. Extended EBU-Arrhenius turbulent combustion model is more reasonable for modeling turbulent reacting flows. SOM-EBU combustion model taking account of the enflence of fluctuation parameters on the reaction rate,is better than EBU-Arrhenius model,and computing time and storge of SOM-EBU model is more than it. DO radiation models,which may be predicted the effect of the dicretion direction and scattering phase on the radiative transfer,is better than Six-flux model and is more applicable for two-phase reacting flows of the annual combustors.The cold flow fields in a sector annual combustor with dual-stage radial swirler are measured by Laser Doppler Velocimeter (LDV). The measured and calculated axial velocity profiles are in general agreement.The performance of the reverse-flow annual combustor is studied with numerical models to consider the distribution of the pollution production. Comparing with experiment data of profiles of outlet gas temperature and lean blowout limit for two cylindrical head annual combustor and the reverse-flow annual combustor,predictions are reasonable. So, it reveals that the numerical procedures are reliable and useable in the design of the annual combustor.更多还原