Hypergolic Ignition Behaviors and Propulsive Performance of a Mixture of [AMIm][DCA] with Methanol, Ethanol, and n-Propanol Reacting with White Fuming Nitric Acid

In this article, we study the hypergolic ignition behaviors between a droplet of 1-allyl-3-methylimidazolium dicyanamide ([AMIm][DCA]) blended by methanol/ethanol/n-propanol and a deep white fuming nitric acid oxidizer pool, with an emphasis on the effects of different alcohol additions. Two high-speed cameras with/without a long-distance microscope and an infrared camera are used to capture the details of the ignition process. The main work of this article is listed as following: (1) The hypergolic process generally follows four steps: contact-microexplosion-massive protrusion-ignition, and the difference caused by alcohol addition is analyzed. (2) Average of microexplosion delay time (EDT) and ignition delay time (IDT) of 19 blended fuels is extracted from at least 10 repeat tests. (3) Temperature evolvement could be divided into three stages, and two reaction modes are proposed by characteristics in the temperature evolvement curve and phenomena in the “massive protrusion” stage. (4) The influence of alcohol addition on propulsive performance is predicted by NASA CEA software, and the result indicates that the fuel with a smaller proportion of alcohol and with fewer carbon atoms in added alcohol is less inclined to generate splashing droplets in the massive protrusion stage and has smaller EDT and IDT. When the volume proportion of alcohol is higher than 0.2, fuels blended by different kinds of alcohols exhibit almost the same hypergolic process, EDT, IDT, and temperature evolvement process. Adding all three kinds of alcohols will overall improve the propulsive performance like specific impulse (I_sp) slightly. However, considering the significant increase in IDT brought by alcohol addition, the best choice of alcohol addition is methanol to obtain the best reduction in viscosity and the smallest weakening in ignition performance while still slightly improving the propulsive performance.