Dynamic evolution of soot particle growth in diesel engine cylinder
Yuanxin YU1,2(),Mingrui WEI1,2,Hongling JU1,2,*()
1. Hubei Provincial Key Laboratory of Modern Auto Parts Technology, Wuhan University of Technology, Wuhan 430070, China 2. Auto Parts Technology Hubei Provincial Collaborative Innovation Center, Wuhan University of Technology, Wuhan 430070, China
A three-dimensional simulation model was established by taking an in-cylinder direct-injection diesel engine as the prototype. A detailed soot model was coupled to analyze the mass distribution and number density variation of soot particles in the cylinder of the diesel engine under different load. The calculated results and airflow parameters were taken as the initial conditions for dynamic simulation, and the particle dynamics model was established by using the Lagrange method to track the motion of each particle in order to calculate the complete growth process of soot particles. Results showed that the nucleation rate of soot gradually approaches zero, the surface growth and condensation rate were lower than the oxidation rate, and the total mass of soot gradually decreased after combustion. The soot mass fraction at the top of the cylinder, cylinder wall, and piston was relatively low. The constructed particle dynamics model can simulate the growth process from basic particles of soot to aggregates. The particle dynamics model can be used to simulate the growth process from soot elementary particles to aggregates, and the morphology of the aggregates obtained under different loads was mainly branched and clustered structure, which was similar to the main morphologies obtained by experimental sampling. The fractal dimensions under different loads were similar to those measured by the experiments, with a maximum error of about 1.5%.
Tab.1Main parameter of diesel engine (YC4FA 116-40)
Fig.2Schematic of combustion chamber mesh
模拟类型
模型
湍流模型
RNG k-ε
蒸发模型
Frossling
碰撞模型
NTC collision
破碎模型
KH-RT
燃烧模型
SAGE
碳烟模型
Particle Size Mimic
NOx模型
Extended Zeldovich
Tab.2Mathematical model in three-dimensional simulation
Fig.3Comparison of simulation and experimental value of cylinder pressure and heat release rate
Fig.4Soot mass fraction in cylinder under different load
Fig.5Soot number density at top of cylinder
Fig.6Average number density and total mass of soot at 50% load
Fig.7Mass change in soot nucleation, surface growth, condensation and oxidation at 50% load
Fig.8Total mass fraction of soot in cylinder at different time under 50% load
p /MPa
vg/(m·s?1)
k/(m2·s?2)
?/ (m2·s?3)
0.18
4.41
0.757
206.71
0.38
4.40
0.766
153.75
0.63
5.17
1.082
275.89
0.88
6.40
1.089
260.02
1.13
9.22
1.501
294.43
Tab.3Airflow parameter at different load
参数
数值
ρp/(g·cm?3)
1.8
A/ J
1×10?19
e
0.4
${z_0}$/ m
4×10?10
${{{{{p}}}} _{\text{pl}}}$/ Pa
5×109
${u_{\text{f}}}$
0.4
Tab.4Particle property in turbulence
Fig.9Initial spatial distribution map of particles in computational domain
Fig.10Cross-sectional view of calculation domain at beginning of calculation under 50% load
Fig.11Cross-sectional view of calculation domain at end of calculation under 50% load
Fig.12Schematic diagram of soot particle accumulation at end of calculation
Fig.13Actual soot accumulation morphology [21]
Fig.14Changing trend of soot particle fractal dimension
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