A numerical model for aluminum cloud combustion which includes the effects of interphase heat transfer,phase change,heterogeneous surface reactions,homogeneous combustion,oxide cap growth and radiation within the Eule...A numerical model for aluminum cloud combustion which includes the effects of interphase heat transfer,phase change,heterogeneous surface reactions,homogeneous combustion,oxide cap growth and radiation within the Euler–Lagrange framework is proposed.The model is validated in single particle configurations with varying particle diameters.The combustion process of a single aluminum particle is analyzed in detail and the particle consumption rates as well as the heat release rates due to the various physical/chemical sub-models are presented.The combustion time of single aluminum particles predicted by the model are in very good agreement with empirical correlations for particles with diameters larger than 10μm.The prediction error for smaller particles is noticeably reduced when using a heat transfer model that is capable of capturing the transition regime between continuum mechanics and molecular dynamics.The predictive capabilities of the proposed model framework are further evaluated by simulating the aluminum/air Bunsen flames of Mc Gill University for the first time.Results show that the predicted temperature distribution of the flame is consistent with the experimental data and the double-front structure of the Bunsen flame is reproduced well.The burning rates of aluminum in both single particle and particle cloud configurations are calculated and compared with empirical correlations.Results show that the burning rates obtained from the present model are more reasonable,while the correlations,when embedded in the Euler–Lagrange context,tend to underestimate the burning rate in the combustion stage,particularly for the considered fuel-rich flames.展开更多
研究了基于层流小火焰概念和假定beta-PDF(probability density function)的湍流预混燃烧模型.该模型采用PREMIX程序来计算层流小火焰,将计算结果表示为进程变量的函数,并利用进程变量的be-ta-PDF积分生成了用于RANS(雷诺平均Navier-Sto...研究了基于层流小火焰概念和假定beta-PDF(probability density function)的湍流预混燃烧模型.该模型采用PREMIX程序来计算层流小火焰,将计算结果表示为进程变量的函数,并利用进程变量的be-ta-PDF积分生成了用于RANS(雷诺平均Navier-Stokes)计算的PDF表.以化学当量的甲烷湍流本生火焰为算例对模型进行了计算验证,并与Zimont模型的计算结果和实验结果做了对比.结果表明,平均速度分布与实验符合的较好,温度和湍动能计算结果有待改善.本模型高估了化学反应速率,导致计算火焰比实际瘦,这是因为模型中未能考虑湍流对火焰的拉伸和弯曲效应,考虑湍流拉伸和弯曲效应的预混燃烧模型是今后进一步研究的方向.展开更多
基金supported by the National Natural Science Foundation of China(No.51706241)Hunan Provincial Natural Science Foundation of China(Nos.2020JJ4665 and 2021JJ30775)+1 种基金Hunan Provincial Innovation Foundation for Postgraduate,China(No.CX2019-0050)support provided by China Scholarship Council(No.201903170201)。
文摘A numerical model for aluminum cloud combustion which includes the effects of interphase heat transfer,phase change,heterogeneous surface reactions,homogeneous combustion,oxide cap growth and radiation within the Euler–Lagrange framework is proposed.The model is validated in single particle configurations with varying particle diameters.The combustion process of a single aluminum particle is analyzed in detail and the particle consumption rates as well as the heat release rates due to the various physical/chemical sub-models are presented.The combustion time of single aluminum particles predicted by the model are in very good agreement with empirical correlations for particles with diameters larger than 10μm.The prediction error for smaller particles is noticeably reduced when using a heat transfer model that is capable of capturing the transition regime between continuum mechanics and molecular dynamics.The predictive capabilities of the proposed model framework are further evaluated by simulating the aluminum/air Bunsen flames of Mc Gill University for the first time.Results show that the predicted temperature distribution of the flame is consistent with the experimental data and the double-front structure of the Bunsen flame is reproduced well.The burning rates of aluminum in both single particle and particle cloud configurations are calculated and compared with empirical correlations.Results show that the burning rates obtained from the present model are more reasonable,while the correlations,when embedded in the Euler–Lagrange context,tend to underestimate the burning rate in the combustion stage,particularly for the considered fuel-rich flames.
文摘研究了基于层流小火焰概念和假定beta-PDF(probability density function)的湍流预混燃烧模型.该模型采用PREMIX程序来计算层流小火焰,将计算结果表示为进程变量的函数,并利用进程变量的be-ta-PDF积分生成了用于RANS(雷诺平均Navier-Stokes)计算的PDF表.以化学当量的甲烷湍流本生火焰为算例对模型进行了计算验证,并与Zimont模型的计算结果和实验结果做了对比.结果表明,平均速度分布与实验符合的较好,温度和湍动能计算结果有待改善.本模型高估了化学反应速率,导致计算火焰比实际瘦,这是因为模型中未能考虑湍流对火焰的拉伸和弯曲效应,考虑湍流拉伸和弯曲效应的预混燃烧模型是今后进一步研究的方向.
