基于反应特性的可变截面甲醇水蒸气重整反应器优化

研究了双套管式甲醇水蒸气重整(Methanol steam reforming,MSR)反应器在热空气加热条件下重整通道中的流场特征和催化床的温度分布特性,结果表明:催化床的温度沿流向迅速降低,最低温度在距催化床入口15 mm至20 mm处;然后,温度随流动方向逐渐升高至反应温度;此外,沿半径方向从中心到壁面催化床温度逐渐升高,热阻的存在使得催化床中心的温度低于周围的温度。根据这一反应特点,本文提出了一种变截面重整反应器,以充分利用供热能量,提高反应效率;然后利用响应面分析法(Response surface methodology,RSM)对变截面反应器的结构参数进行了优化。结果表明,在相同的边界条件下,加热通道重整入口处的外半径R_(1)=49.94 mm,最小横截面处的半径R_(2)=39.99 mm,最小横截面到催化床入口的距离D=98.44 mm,甲醇转化率显著提高。

双套管式甲醇水蒸气重整制氢反应器性能强化研究

以双套管式甲醇水蒸气重整制氢反应装置为研究对象,首先建立以热空气供热重整反应的反应器物理模型,探究在热空气供热条件下,空气温度、流速等参数对甲醇重整制氢的影响;其次,为充分利用供热能量,在供热通道中增加了强化换热的肋片(直肋和波浪肋),分析了3种构型反应器的甲醇转化率和得氢率;最后,为得到较优的反应器结构,采用响应面分析法对波浪肋的结构特性参数进行了优化设计。研究结果表明:甲醇的转化率随空气温度和流速增加而增加;无肋双套管重整反应器装置制氢效率较低,装置出口热空气温度较高,不利于能量优化利用;增加了强化换热肋片的反应器在相同边界条件下甲醇转化率和产氢率都更高,其中,带波浪肋的反应器的性能改善效果更加明显;在波浪肋的特征参数中,肋片高度、肋周期和肋圆半径对反应器传热及甲醇转化率影响较大,肋角的影响较小;当肋高度为10.46 mm,肋周期为5倍半径,肋角度为53.49°,肋圆半径为9.98 mm时,甲醇转化率可达到99%以上。

Application of WSGSA Model in Predicting Temperature and Soot in C_(2)H_(4)/Air Turbulent Diffusion Flame

Soot,a product of insufficient combustion,is usually in the form of aggregate. The multi-scattering of soot fractal aggregates has been proved to play an important role in studying the soot radiative properties,which is rarely considered in predicting the radiative heat transfer in combustion flame. In the present study,based on the weighted sum of gray soot fractal aggregate(WSGSA) model,which is used to predict the temperature field and soot aggregates in turbulent diffusion flame,the flame temperature distribution and soot volume fraction distribution under the conditions of the model without considering radiation,the default radiation model in Fluent software and the WSGSA model are calculated respectively. The results show that the flame temperature will be seriously overestimated without considering radiation and the maximum relative discrepancy of flame centerline temperature is about 64.5%. The accuracy will be improved by the default radiation model in the Fluent software,but the flame temperature is still overestimated and the maximum relative discrepancy of flame centerline temperature is about 42.1%. However,more satisfactory results can be obtained by the WSGSA model,and the maximum relative discrepancy of flame centerline temperature is no more than 15.3%. Similar conclusions can also be obtained in studying the temperature distribution along different flame heights. Moreover,the soot volume fraction can be predicted more accurately with the application of the WSGSA model. Both without considering radiation and using the default radiation model in the Fluent software will result in the underestimating of soot volume fraction. All the results reveal that the WSGSA model can be used to predict the temperature and soot aggregates in the CH/air turbulent diffusion flame.

Application of Light Reflectance-Transmittance Measurement Method to Reconstruct Geometrical Morphology of Particle Fractal Aggregates

Particles,including soot,aerosol and ash,usually exist as fractal aggregates.The radiative properties of the particle fractal aggregates have a great influence on studying the light or heat radiative transfer in the particle medium.In the present work,the performance of the single-layer inversion model and the double-layer inversion model in reconstructing the geometric structure of particle fractal aggregates is studied based on the light reflectancetransmittance measurement method.An improved artificial fish-swarm algorithm(IAFSA)is proposed to solve the inverse problem.The result reveals that the accuracy of double-layer inversion model is more satisfactory as it can provide more uncorrelated information than the single-layer inversion model.Moreover,the developed IAFSA show higher accuracy and better robustness than the original artificial fish swarm algorithm(AFSA)for avoiding local optimization problems effectively.As a whole,the present work supplies a useful kind of measurement technology for predicting geometrical morphology of particle fractal aggregates.