非线性拉伸对层流燃烧速度提取的影响

Effect of nonlinear stretch on extraction of laminar burning velocity

基于理论模型推导出一种非线性NLC层流燃烧速度外推方程,并采用定容燃烧弹获取甲烷/空气、正丁烷/空气和氢气/空气的火焰发展历程。基于文献常用和本文提出的4种线性和非线性外推方程研究4种典型火焰中非线性拉伸对层流燃烧速度提取的影响。研究结果表明:随着马克斯坦长度的增加,非线性拉伸的影响增加,不同方程测量的层流燃烧速度差异增加。其中,本文提出的非线性NLC模型得到的结果与实验结果吻合最好,测量层流燃烧速度精度最高;非线性LC和NLS模型表现居中,而线性LS模型明显高估层流燃烧速度。另外,可以采用高精度非线性模型并适当增加初始火焰半径的策略减小非线性拉伸的影响,从而提高层流燃烧速度的测量精度。

A nonlinear equation for extracting laminar burning velocity was deduced from a detailed theoretical model,and flame development history of methane/air,n-butane/air and hydrogen/air mixtures was obtained by using a constant-volume combustion bomb.Four linear and nonlinear extraction models form previous and present works were used to investigate the influence of nonlinear stretch on laminar burning velocity extraction for four typical flames.The results show that the influence of nonlinear stretch on flame increases with the increasing Markstein length,and consequently the difference in laminar burning velocity measured using four extraction methods increases.The nonlinear NLC model proposed in present work is in full best agreement with the experimental results,and thus it measures the most accurate laminar burning velocity.The performance of nonlinear LC and NLS models is good,while the linear LS model obviously over-estimates laminar burning velocity.In addition,a strategy of increasing initial flame radius properly and using a high-accuracy,nonlinear model can be applied to reduce the effect of nonlinear stretch on extraction and improve the accuracy in the measurements of laminar burning velocity.