天然气发动机燃烧过程非线性动力学特性

摘要

利用非线性动力学数据分析技术对增压中冷天然气发动机燃烧过程的动力学特性进行了研究,结果表明:混合气浓度从当量比φ=1.00降低到稀燃极限时由缸压时间序列重构的二维相空间中,系统运动轨线都是有限范围内的非周期运动,轨线具有复杂、扭曲、重叠的几何结构;无论发动机是在当量混合气还是稀燃极限条件下运行,嵌入维m大于某一值以后,吸引子的关联维D均能达到饱和值且为分数,随着混合气变稀,燃烧循环变动增加,D逐渐增加,当φ=1.00、0.77、0.70和0.63时D分别为1.27、1.33、1.58和1.87,最大Lyapunov指数(LLE)大于零,分别为0.008 6、0.011、0.013和0.0157,因此天然气发动机燃烧系统是一个低维非线性混沌系统.%Combustion process of supercharged inter-cooled natural gas engine was studied using nonlinear dynamic data analysis technology under the conditions of equivalence ratio (Φ ) from 1. 00 to lean burn limit. Results showed that motion trajectories of combustion system in 2-D reconstructed state space fell into a finite range at different conditions, there were complex, twist and wrap geometric structures in reconstructed state space. Correlation dimension ( D) of attractors could reach saturation value after embedding dimension m was greater than a certain value when engine worked at both conditions of equivalence ratio mixture and lean burn limit, at the same time the values were fractional, with the decrease of mixture concentration, cycle-to-cycle combustion variations increased, D increased, the D of attractors were 1.27,1.33,1.58 and 1.87, Largest Lyapunov Exponent (LLE) were 0. 008 6, 0.011, 0. 013 and 0. 015 7 respectively at the conditions of equivalence ratio Φ = 1. 00,0. 77,0. 70 and 0. 63, therefore the combustion system of natural gas engine was a low-dimension chaos system.