Revisiting the Combustion Kinetics of Di-Isopropyl Ketone: New Insights from Elevated Temperature LBV Measurements

This study focuses on measuring the laminar burning velocity (LBV) of the second-generation biofuel di-isopropyl ketone (DIPK) + air mixtures using an externally heated diverging channel method at elevated mixture temperatures. Experiments were conducted at elevated mixture temperatures of up to 639 K across a range of equivalence ratios varying from 0.7 to 1.3 under atmospheric pressure conditions. The obtained LBV measurements were compared with existing experimental data and predictions from a recently developed comprehensive chemical kinetic model of DIPK. The results demonstrated good agreement between the present LBV measurements and existing data, and the predictions from the Lin model also showed a good trend of LBV values at lower mixture temperatures (up to 393 K). However, the Lin model exhibited significant underpredictions at elevated temperatures when compared to the present measurements. From the sensitivity analysis, key reactions were identified, and the rate coefficients of reaction R84 were updated from the recent mechanism of NUIGMech1.3. Notably, the updated rate coefficients for reaction R84: CH2 + O2 => CO2 + 2H showed an increase in the rate constant with temperature (∼293% at 2500 K, ∼220% at 750 K, and ∼174% at 500 K), enhancing the LBV of DIPK + air mixtures. The updated DIPK model demonstrated improved agreement with LBV measurements from existing literature across various mixture temperatures and equivalence ratios, as well as with the present experimental data at elevated temperatures. The modification of R84 improves LBV, with a negligible impact on ignition delay times and species mole fraction profiles.

本研究聚焦于采用外加热扩通道法，在升高的混合气温度条件下，测量第二代生物燃料二异丙基酮（di-isopropyl ketone, DIPK）与空气混合气的层流燃烧速度（laminar burning velocity, LBV）。实验在大气压条件下开展，混合气温度最高可达639 K，当量比覆盖0.7至1.3的范围。将获取的LBV测量数据与现有实验数据，以及新近开发的DIPK综合化学动力学模型的预测结果进行对比后发现：本次测得的LBV与已有实验数据吻合良好；林模型（Lin model）的预测结果在较低混合气温度（最高393 K）下也能较好匹配LBV的变化趋势，但在高温工况下，该模型对LBV的预测值显著低于本次实验测量结果。通过敏感性分析识别出关键反应，并基于NUIGMech1.3最新机理更新了反应R84的速率系数。值得注意的是，更新后的反应R84（CH2 + O2 => CO2 + 2H）的速率常数随温度升高而增大（2500 K时提升约293%，750 K时约220%，500 K时约174%），这一调整提升了DIPK+空气混合气的层流燃烧速度。更新后的DIPK化学动力学模型，在不同混合气温度和当量比条件下，与现有文献中的LBV测量数据以及本次高温工况下的实验数据均展现出更优的吻合度。对反应R84的修改可有效提升LBV，且对点火延迟时间和物种摩尔分数分布的影响可忽略不计。