异辛烷/空气对冲火焰实验与计算分析

Experiment and Numerical Investigation on Counterflow Twin-flame of Isooctane/Air

关键词:  异辛烷  对冲火焰  火焰传播速度  三维粒子动态分析仪PDPA 

Key words:  Isooctane  Counterflow twin-flame  Flame speed  Phase doppler particle analyzer (PDPA)

摘要:

为了解决汽油机清洁高效燃烧的难题,需要对汽油的基础燃烧特性进行深入研究。为此选取异辛烷单一组分作为表征燃料,对其预混层流火焰传播速度进行了实验与分析。设计并搭建了适宜液体燃料燃烧的对冲火焰试验台,通过对异辛烷对冲火焰的实验,获得了不同当量比下的无拉伸火焰传播速度,发现随着当量比的增大异辛烷火焰传播速度先增大后减小,在当量比1.1时火焰传播速度达到最大值。在标准大气压、初始温度为378K的工况下,异辛烷最大火焰传播速度为60.9cm/s。利用异辛烷、正庚烷、乙醇三组分燃料着火机理计算了异辛烷火焰传播速度,并针对火焰传播速度进行灵敏度分析,得到了控制异辛烷火焰传播速度的主要基元反应。通过实验结果与计算结果的对比,结合文献中给出的实验数据,对影响异辛烷火焰传播速度的主要因素进行分析,发现初始温度提高、环境压力降低能够使异辛烷燃烧火焰传播速度提高。 

Abstract:

In order to solve the problem of clean combustion of gasoline engine, it is necessary to carry out the in-depth study of combustion characteristics of gasoline. Isooctane was selected as single component alternative fuel to do the experiments and analysis on the premixed laminar flame speed. A counterflow twin-flame test-bed suitable for liquid fuel was designed and built. Based on the counterflow twin-flame experiments of isooctane/air mixture, the unstretched flame speed of different equivalent ratios was obtained.It is noted that with the increase of equivalent ratio the flame speed of isooctane increases firstly and then decreases. When equivalent ratio is 1.1, the speed reaches the maximum value. At the condition of standard atmospheric pressure and initial temperature 378K, the maximum flame speed of isooctane is 60.9cm/s. A mechanism in which the ignition mechanism of three-component fuel consisted of isooctane, n-heptane and ethanol reported in the literature was used to calculate the flame speed of isooctane/air mixture, and the sensitivity analysis of flame speed was implemented to get the main elementary reactions dominating combustion rate.Based on the comparison among experimental results, calculation results and experimental data collected from the literatures, this paper analyzes the main influence factors of flame speed of isooctane/air mixture, and finds that increase of initial temperature and decrease of pressure can increase the flame speed. 