Droplet size and velocity distribution function in sprays based on maximum entropy principle
-
摘要: 应用最大熵原理和动量守恒定律, 从理论上建立了喷雾液滴尺寸和速度联合分布函数。应用该方程编制数值计算程序, 对纯柴油与质量掺混比为30%(L30)的柴油/液化石油气(LPG)混合燃料的喷雾液滴尺寸和速度联合分布进行了数值计算, 比较了两种燃料的雾化特性。比较结果表明: 由于L30闪急沸腾效应的影响, 其液滴尺寸分布曲线的峰值明显高于柴油的分布曲线峰值, 且峰值和曲线整体趋势都向小颗粒方向偏移, 说明喷射L30产生的液滴颗粒比柴油颗粒小; L30的速度分布曲线峰值较高, 且位于小速度范围, 说明小速度液滴所占的比例更大。液滴尺寸与速度(D-u)等高线图表明: 液滴颗粒越小, 其速度分布范围越广; 液滴速度越小, 其尺寸分布范围越大。L30液滴尺寸与速度联合分布的收敛速度较快, 说明L30喷雾所产生的小颗粒和小速度液滴更加密集, 雾化质量更佳。
-
关键词:
- 工程热物理 /
- 柴油 /
- 柴油与液化石油气混合燃料 /
- 最大熵原理 /
- 喷雾液滴尺寸和速度联合分布函数 /
- D-u等高线
Abstract: A droplet size and velocity distribution function was theoretically derived based on the maximum entropy principle and the momentum conservation law.The numerical calculations for the function on the droplet size and velocity distribution of pure diesel and L30(mixed liquefied petroleum gas(LPG)/diesel fuel in a mass ratio of 30 per cent LPG) were done, and a comparison analysis of the spray characteristics between diesel and L30 was conducted.The result shows that because of the influence of flash boiling injection, the peaks of the droplet size distribution curve of L30 are evidently higher than those of diesel, the curve and its peaks move toward smaller droplet diameters region, which indicates that the droplets produced by injecting L30 are smaller than those of diesel; the peaks of the velocity distribution curves of L30 are higher than those of diesel, and locate a lower velocity region, which shows that the droplet number of lower speed is more than that of higher speed for the L30.The size-velocity(D-u) contour maps of diesel and L30 obtained by the droplet size and velocity distribution curves shows that smaller drops occupy a wide velocity space, and lower speed droplets have a wide size space.The size and velocity distribution of L30 converges faster than that of diesel, which indicates that the smaller size and lower velocity drops of L30 are more than those of diesel, and the spray quality of L30 is better than that of diesel. -
表 1 Computational parameters
Table 1. Computational parameters
density/(kg·m-3) vaporization heat/(kJ·kg-1) specific heat of diesel-air mixture/[kJ·(kg·K)-1] heat conduct coefficient/[kW·(m·K)-1] injected duration/ms injected mass/mg spray core angle/(°) 845 251 1.005 1.28×10-4 9 5 19.3 
下载: 导出CSV
表 2 Computational parameters of LPG
Table 2. Computational parameters of LPG
density/(kg·m-3) vaporization heat/(kJ·kg-1) specific heat of L30-air mixture/[kJ·(kg·K)-1] heat conduct coefficient/[kW·(m·K)-1] 557 propane 426 2.480 1.511 9×10-5 butane 385 2.360 1.349 1×10-5 LPG 410 2.432 1.444 4×10-5
下载: 导出CSV
-
[1] 曹建明. 喷雾学[M]. 北京: 机械工业出版社, 2005. [2] CAO Jian-ming, BI AN Yao-zhang, QI Dong-hui, et al. Comparative investigation of diesel and mixed liquefied petroleum gas/diesel injection engines[J]. Journal of Automobile Engi-neering, 2004, 218(D5): 557-565. doi: 10.1243/095440704774061219 [3] ROSI N P, RAMMLER E. The laws governing the fineness of powdered coal[J]. Fuel, 1931, 7: 29-36. https://citeseerx.ist.psu.edu/showciting?cid=4699567 [4] RIZK N K, LEFEBVRE A H. Drop-size distribution characteristics of spill-return atomizers[J]. Journal of Propulsion and Power, 1985, 1(1): 16-22. doi: 10.2514/3.22753 [5] MUGELE R, EVANS H D. Droplet size distributions in sprays[J]. Industrial and Engineering Chemistry, 1951, 43: 1317-1324. doi: 10.1021/ie50498a023 [6] SELLENS R W, BRZUSTOWSKI T A. A prediction of thedrop size distribution in a spray from first principle[J]. Atomization and Spray Technology, 1985, 1(2): 89-102. [7] LI Xian-guo, TANKIN R S. Droplet size distribution: a derivation of a Nukiyama-Tanasawa type distribution function[J]. Combustion Science and Technology, 1987, 56: 65-76. doi: 10.1080/00102208708947081 [8] CAOJian-ming. On the theoretical prediction of fuel droplet size distribution in nonreactive diesel sprays[J]. Journal of Fluids Engineering, 2002, 124: 182-185. doi: 10.1115/1.1445140 [9] LEVY N, AMARA S, CHAMPOUSSI N J C, et al. Nonreactive diesel spray computations supported by PDA measurements[J]. SAE Paper: 970049. [10] LI Mei-sen. Initial droplet size and velocity distribution for liquid sprays based on maxi mization of entropy generation[D]. Waterloo: University of Waterloo, 2005. -
点击查看大图
图(8) / 表(2)
计量
- 文章访问数: 222
- HTML全文浏览量: 50
- PDF下载量: 297
- 被引次数: 0
