乙醇氧化基态OH浓度时程吸收光谱诊断

Laser Absorption Spectrum Measurement of OH Concentration Time-histories inEthanol Oxidation

为了提供宽温度、压力和当量比范围下乙醇燃烧反应动力学模型的微观验证数据,利用反射激波结合紫外吸收光谱诊断技术,分别以OH的A-X(0,0)跃迁中306.6868 nm和306.47 nm为低压和高压诊断中心波长,在1200~1700 K工况下对当量比为0.5和1.0的两种乙醇/氧气/氩气混合气进行了OH浓度时程定量测量,有效拓展了乙醇动力学模型微观验证数据的工况,低压实验拓宽了温度边界;高压实验是国际上率先公开发表的OH浓度时程数据,且具有很好的重复性。结果表明,在所研究工况的下,乙醇氧化过程中OH浓度演化存在温度依赖效应,所选的4个代表性乙醇动力学模型仅能预测OH浓度曲线形态,无法同时预测各阶段OH浓度和浓度爬升时刻。虽然在不确定度范围内调整反应速率常数可有效地改善模型对点火延迟期的预测,但无法兼顾对OH峰值浓度的高精度预测,通过动力学分析对反应群进行分析筛选,给出乙醇动力学模型优化的建议。

To provide micro-dimensional validation data for kinetic models of ethanol combustion reactions over a wide range of temperatures,pressures and equivalence ratios,OH time histories concentrations of two ethanol diluted mixtures(equivalent ratio of 0.5 and 1.0)were measured using a kinetic shock tube combined with a diagnostic technique of UV absorption spectroscopy in the temperature range of 1200∼1700 K.In order to target various pressures,diagnostic wavelengths in the OH A-X(0,0)transition at 306.6868 nm and 306.47 nm were chosen.The experiments effectively expanded the working conditions of the microscopic verification data of the ethanol kinetic model:low-pressure experiments expanded the temperature boundary;high-pressure experiments data were the first published OH time-history data with good repeatability.Results revealed the temperaturedependence on the evolution of OH concentration during the ethanol oxidation.The selected four representative ethanol kinetic models can only predict the shape of the OH profiles,but failed to predict the concentration value and ignition delay time.While adjusting the reaction rate constant within the experimental uncertainty can effectively improve the model’s prediction of the ignition delay time,it cannot simultaneously guarantee a high-accuracy prediction of the OH peak value.Therefore,the reaction groups are screened by kinetic analysis to give suggestions on the direction of further optimization of the ethanol combustion reaction kinetic model.