The effect of an N-alkyl substituent R on the characteristics of ignition of hypergolic ionic liquids (ILs) upon contact with white fuming nitric acid (WFNA) is examined by a modified drop test method that simultaneously combines high-speed shadow imaging with high-speed two-color pyrometry. The number of carbon atoms in the synthesized N-alkylated propargyl-imidazolium dicyanamide with alkyl substituents varied from 1 to 7. The ILs under study can be grouped in two categories depending on the initial location of the flame zone. When R has 1 to 3 carbon atoms, ignition is visualized as a glow inside a bubble (formed after droplet fall) and above the liquid surface. When the number n of carbon atoms in R is 4 to 6, no glow is recorded inside the bubble. In the case of a heptyl substituent, ignition does not occur since no flame is observed during approximately one minute. It is shown that the value of ignition delay can be interpreted as an Arrhenius-type function where the exponent depends linearly on n. An analysis of high-speed video records shows that the evaporation starting time of WFNA measured from the first IL–WFNA contact is also an Arrhenius-type function of n. Furthermore, it is found that the time for a bubble to reach its maximum diameter is independent of n. A possible mechanism of reaction between ILs of this class and WFNA is suggested and discussed.

通过改进的跌落试验方法研究了N-烷基取代基R对与白色发烟硝酸（WFNA）接触的高离子性离子液体（ILs）着火特性的影响，该方法同时将高速阴影成像与高光谱成像相结合。速度两色高温法。合成的具有烷基取代基的N-烷基化炔丙基-咪唑鎓二氰胺中的碳原子数为1至7。根据火焰区域的初始位置，所研究的IL可以分为两类。当R具有1至3个碳原子时，点火在气泡内（液滴滴落后形成）和液面上方会以辉光的形式显现出来。当数nR中的碳原子数为4至6，气泡内未记录辉光。在庚基取代基的情况下，由于在大约一分钟内未观察到火焰，因此不会发生着火。结果表明，点火延迟的值可以解释为一个Arrhenius型函数，其中指数线性地取决于n。高速视频记录的分析表明，从第一次IL–WFNA接触开始测量的WFNA的蒸发开始时间也是n的Arrhenius型函数。此外，发现气泡达到其最大直径的时间与n无关。建议并讨论了此类IL与WFNA之间可能的反应机制。