火花点火天然气发动机混沌燃烧过程分析

Analysis of Chaos Combustion Process in Spark Ignition Natural Gas Engine

为了揭示边界条件对点燃式天然气发动机燃烧系统非线性动力学的影响规律,研究了不同点火正时下电控喷射点燃式天然气发动机燃烧系统的混沌特性.结果表明:在爆震限定范围内,随着点火提前角(spark advanceangle,SAA)的增加,平均指示压力(indicated mean effective pressure,IMEP)增加,循环变动系数(COVIMEP)降低;相空间中吸引子具有扭曲、相互交叉和折叠的复杂几何结构,但它也是一个有限范围内的运动,燃烧系统吸引子内的轨线表现出一定非周期的有序;吸引子的关联维(correlation dimension,CD)为小于2的分数,最大Lyapunov指数为正数,说明天然气发动机燃烧系统表现出明显的混沌特征;当SAA从30°CA增加到45°CA时,IMEP从0.798 MPa增加到0.854MPa,COVIMEP从4.4%降低到1.2%,CD从1.76降低到1.59,最大Lyapunov指数从0.1降低到0.04,因此燃烧系统复杂度及系统对初始条件的敏感性下降.

Chaos characteristics of the combustion process in an electronic controlled injection,spark ignition natural gas engine are studied using non-linear data analysis technology and chaos theory.The analysis of time series of multi-cycle in-cylinder pressure and reconstructed attractor in phase-space indicates that as spark advanced angle（SAA） increases,indicated mean effective pressure（IMEP） increases,coefficient of cyclic variation（COVIMEP） decreases.The attractor of the combustion system in phase space has a twist,intercrossed and folded structure,with nonperiodic order.The correlation dimension（CD） of the reconstructed attractor is a fractional less than 2,and largest Lyapunov exponent（LLE） is positive,which means that the combustion system of natural gas engine is a low-dimensional chaos system.When SAA increases from 30°CA to 45°CA,IMEP increases from 0.798 MPa to 0.854 MPa,COVIMEP decreases from 4.4% to 1.2%,CD decreases from 1.76 to1.59,and LLE decreases from 0.1 to 0.04;therefore both of the complexity of the combustion system and sensitivity of the system to initial conditions become smaller.