Experimental Studies of the Interaction of Liquid Rocket Fuel Droplets with Detonation Waves

The key determinant of continuous, steady propagating detonations is the heat release rate from the multi-phase fuel-air mixture, which must be rapid enough to sustain the propagating DW. The overall combustion timescale of the droplets depends in a complicated way on the timescale of droplet vaporization, air/fuel mixing, and reaction/ignition/heat release. There are significant knowledge gaps at the scale of individual droplets or small clusters of droplets interacting with DW, which currently impede the construction of realistic and accurate models of multi-phase detonations. In addition, models of droplet-DW interactions are not available, even for single droplets. This places severe limitations on understanding DW-droplet interactions and on developing physically correct models for aerodynamic drag, deformation, breakup, vaporization, and combustion. The current study investigated the effects of a sustained DW on a nitromethane fuel droplet in a detonation tube environment. The DWs were initiated using a methane-oxygen mixture at an initial temperature of 293 K and a pressure of 1 atm. The current investigation of DW-droplet interaction is the first of its kind in recent times. This study highlights many similarities with literature studies (non-reacting experiments with water droplets and shock waves) and validates the fundamental information currently available regarding interactions between shock waves and droplets while contributing more information regarding the impact of reacting droplets by DWs.