利用激光诱导炽光法定量测量柴油机缸内燃烧过程碳烟体积分数

Quantitative Measurements of Soot Volume Fractions in Diesel Engine Using Laser-Induced Incandescence Method

激光诱导炽光(LII)法是一种用于测量火焰中碳烟体积分数的光学测试方法.本文介绍了LII的基本原理以及LII实现定量测量的常见标定方法,建立了一套基于双色法-激光诱导炽光法(2C-LII)的用于柴油机缸内燃烧过程碳烟体积分数定量测量的测试系统,该测试系统采用双成像原理,可以实现多点标定和全视场范围内的碳烟体积分数测量.在一台工作在1200 r?min-1、喷油量21 mg的光学单缸柴油机上,研究了60、100和140MPa三个不同喷油压力下,缸内燃烧过程碳烟的分布情况,结果表明,碳烟自发光出现在燃烧放热率峰值之后,且随着喷油压力提高,碳烟发光持续期缩短,碳烟发光强度降低.测试区域内火焰中的碳烟体积分数范围约为0-50×10-6.不同喷油压力下,碳烟生成初期、碳烟峰值和碳烟氧化三个阶段内平均碳烟体积分数的范围分别是:5×10-6-9×10-6,15×10-6-20×10-6和14×10-6-16×10-6.喷油压力提高后火焰中的碳烟分布区域面积增大,平均碳烟体积分数减小,碳烟体积分数的空间分布趋于均匀.

Laser-induced incandescence（LII） is an optical diagnostic method used to measure the soot volume fraction in a flame. In this paper, the principle of LII and the calibration methods normally used are introduced.Based on two-color LII theory, a quantitative test system for determining the in-cylinder soot volume fraction was established. A dual imaging setup was used, which can achieve multipoint calibration and full field-of-view quantification of soot in a diesel engine chamber. An investigation was carried out on an optical diesel engine with the conditions 1200 r·min^-1 and 21 mg fuel injection per cycle, with various injection pressures（60, 100,and 140 MPa）. The results show that the natural soot incandescence emerged after the peak rate of combustion heat release. With increasing injection pressure, the duration of natural soot incandescence shortened and the natural soot luminosity decreased. The range of soot volume fractions in the test zone was（0-50）×10^-6 The mean soot volume fraction at the initial soot stage, soot peak, and soot oxidation stage were in the ranges（5-9）×10^-6（15-20）×10^-6 and（14-16）×10^-6 respectively, depending on the injection pressure. With increasing injection pressure, the distribution area of the soot particles increased, the mean soot volume fraction decreased, and the distribution of the soot volume fraction in space tended to be more uniform in combustion flames.