﻿ 超高压喷射条件下非常态燃油的缸内燃烧排放特性研究
 舰船科学技术  2016, Vol. 38 Issue (11): 80-83 PDF

Research on combustion and emission characteristics of non-normal fuel under super-high pressure injection condition
YANG Kun, OUYANG Guang-yao, AN Shi-jie, LIU Qi
Navy University of Engineering, Academy of Power Engineering, Wuhan 430033, China
Abstract: In order to improve the combustion and emission performance of high power diesel engine, the super-high fuel injection pressure more than 180MPa was proposed. The three-dimensional geometric model including combustion chamber and intake duct was established. The dynamic grid division of the simulation model was completed on the FIRE software. The calculation results of the internal flow field of the nozzle were used as the boundary to simulate the combustion process. The effects of the physical parameters of fuel and nozzle parameters on the combustion and emission characteristics of diesel engine were analyzed. The results show that when the physical parameters change, the cavitation effect of nozzle is enhanced, which is helpful to the oil beam to obtain good initial broken state. The atomization effect is improved, and the combustion process in the cylinder become more fully; When the nozzle diameter increases, the initial turbulent kinetic energy increases, the range of fuel becomes larger. The fuel injection duration is shorter, and the later emission concentration is small; With the fuel injection angle increases, the fuel and air mixture in the cylinder becomes more uniform, and the combustion performance is further enhanced.
Key words: super-high pressure injection     combustion and emission characteristics     FIRE     non-normal fuel
0 引言

1 燃油物性参数的变化

1.1 密度

 $\overline \rho = \frac{\rho }{{{\rho _0}}} = 1 + \frac{{0.6 \times {{10}^{ - 9}}p}}{{1 + 1.7 \times {{10}^{ - 9}}p}}\text{，}$ (1)

 $\rho = {\rho _0}\left[ {1 + \frac{{0.69 \times {{10}^{ - 9}}p}}{{1 + 3.23 \times {{10}^{ - 9}}p}} - {\lambda _T}\left( {t - {t_0}} \right)} \right]\text{。}$ (2)

 图 1 密度随压力的变化 Fig. 1 The density variation with pressure
1.2 音速

 $\begin{array}{l} a = {\left( {\displaystyle\frac{{{\rm d}p}}{{{\rm d}\rho }}} \right)^{\displaystyle\frac{1}{2}}} = \left\{ {{\rho _0}\left[ {\displaystyle\frac{{0.69 \times {{10}^{ - 9}}}}{{{{\left( {1 + 3.23 \times {{10}^{ - 9}}p} \right)}^2}}}} \right.} \right. + \\[15pt] \quad \quad {\left. {1.8 \times {{10}^{ - 4}} \cdot \zeta {{\left( {\displaystyle\frac{{t + 135.15}}{{{t_0} + 135.15}}} \right)}^{ - d}}\left( {t - {t_0}} \right)} \right\}^{ - \frac{1}{2}}}\text{。} \end{array}$ (3)

 图 2 音速随压力的变化 Fig. 2 The speed of sound variation with pressure
1.3 弹性模量

 $\begin{array}{l} \!\!B \!=\! \rho \displaystyle\frac{{{\rm d}p}}{{{\rm d}\rho }}\!=\!\quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \\ \!\! \displaystyle \frac{{1 \!\!+\! \!\displaystyle\frac{{0.69 \!\!\times\!\! {{10}^{ - 9}}p}}{{1 \!\!+\!\! 3.23 \!\!\times\!\! {{10}^{ - 9}}p}} \!-\! {\lambda _T}\left( {t - {t_0}} \right)}}{{\displaystyle\frac{{0.69 \!\!\times\!\! {{10}^{ - 9}}p}}{{{{\left( {1 \!\!+\!\! 3.23 \!\!\times\!\! {{10}^{ - 9}}p} \right)}^2}}} \!\!+\!\! 1.8 \!\!\times\!\! {{10}^{ - 4}}\zeta {{\left( {\displaystyle\frac{{t \!+\! 135.15}}{{{t_0} \!+\! 135.15}}} \right)}^{ - d}}\!\!\left( {t \!-\! {t_0}} \right)}}\text{。} \end{array}$ (4)

 图 3 弹性模量随压力的变化 Fig. 3 The bulk modulus variation with pressure
2 计算模型及验证

 图 4 计算网格 Fig. 4 Calculation grid

 图 5 试验与仿真结果对比 Fig. 5 Contrast of experimental and simulation results
3 结果分析 3.1 常态燃油和非常态燃油的燃烧排放特性比较

 图 6 常态燃油和非常态燃油的燃烧排放性能对比 Fig. 6 The contrast of combustion and emission performance of normal fuel and non-normal fuel
3.2 喷孔直径对非常态燃油燃烧排放特性的影响

 图 7 不同喷孔直径的燃烧排放性能对比 Fig. 7 The contrast of combustion and emission performance under different nozzle diameters
3.3 喷射夹角对非常态燃油燃烧排放特性的影响

 图 8 不同喷射夹角的燃烧排放性能对比 Fig. 8 The contrast of combustion and emission performance under different injection angles
4 结语

1）在超高压喷射条件下当燃油的物性参数变化时，燃油在喷孔出口处具有良好的初始破碎状态，在向前射流发展时雾化效果较好，促进了缸内燃烧的充分进行，显示出了较好的经济性和动力性。

2）当喷孔直径增大时喷油速率变大，燃油与空气之间的相互作用变得更加剧烈，油气混合效果改善，提高了整机的燃烧排放性能。

3）随着喷射夹角的增大，喷孔内部空化效应增强，燃油与空气混合得更加均匀，促进了燃烧过程的高效进行。但由于喷射夹角的改变受限于喷嘴的结构形式，故影响效果并不明显。

 [1] 许建昌, 李孟良, 李锦, 等. 满足欧Ⅳ/Ⅴ排放法规的柴油机排气后处理技术[J]. 现代车用动力 , 2006 (2) :12–16. [2] SU W H, LIU B, WANG H, et al. Effects of multi-injection mode on diesel homogeneous charge compression ignition combustion[J]. Journal of Engineering for Gas Turbines and Power , 2006, 129 (1) :230–238. [3] 唐开元, 欧阳光耀. 舰船大功率柴油机可控低温高强度燃烧技术及其实现[J]. 柴油机 , 2006, 28 (S) :29–32, 43. [4] 张鹏顺, 陆思聪. 弹性流体动力润滑及其应用[M]. 北京: 高等教育出版社, 1995 . [5] 孔珑. 工程流体力学(第2版)[M]. 北京: 水利电力出版社, 1992 . [6] NIKOLIĆ B D, KEGL B, MARKOVIĆ S D, et al. Determining the speed of sound, density and bulk modulus of rapeseed oil, biodiesel and diesel fuel[J]. Thermal Science , 2012, 16 (S2) :505–514. [7] GRAZ. AVL-fire reference manual, version 8.5[EB/OL]. (2006-12)[2011-09-20]. http://www.avl.com. (请核对作者与引用、更新日期) [8] PAYRI R, GARCÍA J M, SALVADOR F J, et al. Using spray momentum flux measurements to understand the influence of diesel nozzle geometry on spray characteristics[J]. Fuel , 2005, 84 (5) :551–561. DOI:10.1016/j.fuel.2004.10.009