Shock-tube study of dimethyl ether ignition by high-voltage nanosecond discharge
Shock-tube study of dimethyl ether ignition by high-voltage nanosecond discharge
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DOI：
10.1016/j.combustflame.2019.02.001
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发表时间：
2019-05
影响因子：
4.4
通讯作者：
I. Kosarev;S. Kindysheva;I. Kochetov;A. Starikovskiy;N. Aleksandrov
中科院分区：
文献类型：
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作者：
I. Kosarev;S. Kindysheva;I. Kochetov;A. Starikovskiy;N. Aleksandrov
利用带放电单元的激波管，在1075 ~ 1860 K温度范围内，对二甲醚（DME）在DME：O2：Ar和DME：O2：Ar：He混合气体中的点火动力学进行了实验研究。我们测量点火延迟时间后，反射冲击波在贫和化学计量比的混合物。测量是在由高压纳秒放电和无放电等离子体激活的混合物中进行的。通过对二甲醚（DME）的放电和着火过程的数值模拟，研究了DME着火的主要机理。我们计算了在放电中产生的化学活性物质的密度，并使用这些数据来模拟点火。对于自燃和等离子体辅助点火，计算的点火延迟时间与实测数据吻合较好。通过灵敏度分析，给出了放电和点火过程中的极限过程。结果表明，部分替代Ar与他在研究的混合物中允许相同的值的等离子体辅助点火延迟时间在低得多的气体温度是相反的点火没有等离子体的延迟时间是不敏感的替代Ar与他。计算结果表明，这是由于DME，O2和Ar的激发比放电能量增加，而He的激发可以忽略不计。从计算结果可以看出，DME分子的电子碰撞电离对放电阶段活性物质的产生以及等离子体点火具有重要意义。二甲醚的电子碰撞电离截面知之甚少，其变化影响计算的点火延迟时间。此外，在降低的气体温度下，等离子体不均匀性的影响对于激波管研究是重要的。
A shock tube with a discharge cell was used to experimentally analyze the kinetics of dimethil ether (DME) ignition in DME:O2:Ar and DME:O2:Ar:He mixtures at temperatures from 1075 to 1860 K. We measured ignition delay time in lean and stoichiometric mixtures after a reflected shock wave. Measurements were made in the mixtures activated by a high-voltage nanosecond discharge and without discharge plasma. The dominant mechanisms of DME ignition were studied on the basis of a numerical simulation of the discharge and ignition stages. We calculated the densities of chemically active species generated in the discharge and used these data to model ignition. The calculated ignition delay times agreed reasonably with the measured data for autoignition and plasma-assisted ignition. The limiting processes during the discharge and ignition were shown using sensitivity analysis. It was demonstrated that the partial replacement of Ar with He in the mixtures studied allowed the same values of plasma-assisted ignition delay times at much lower gas temperatures being opposite to ignition without plasma where the delay time was not sensitive to the replacement of Ar with He. Calculations showed that this is explained by an increased specific discharge energy spent on the excitation of DME, O2and Ar, whereas the excitation of He was negligible. It followed from the calculations that electron-impact ionization of DME molecules is of great importance for the production of active species in the discharge phase and consequently for ignition with plasma. The electron-impact ionization cross section of DME is poorly known and its variation influences the calculated ignition delay time. In addition, at reduced gas temperatures, the effect of plasma nonuniformity is important for shock-tube studies.