Influence of afterburning suppression on the combustion of solid propellants: Recent progress and outlook

Abstract

The exhaust gas, CO and H2, occupy about a half amount of combustion products, and they make the oxidative reaction with oxygen in the ambient air entraining into the plume during the combustion of solid propellants, producing shock wave, visible flash and increased infrared radiation. In order to inhibit the afterburning plume of solid rocket motors, one of the best ways is to utilize potassium salts as suppression in the propellant formulation. This review discussed and summarized the influence of a great number of potassium salts including inorganic (K2SO4, KHCO3, KCl, KNO3, KBF4, and K3Co(NO2)6 etc.) and organic (K2C2O4, Potassium biphthalate, KD, energetic K(NNMPA) and ADNPK) compounds on the decomposition kinetics, flame structures and temperature, burning rate, combustion wave structures, quenched surface of solid propellants, especially the plateau burning effect. The equipment of plume tests involves in the pressure differential scanning calorimetry, infrared (IR) radiation signature, afterburning flame length and nitrogen-filled pressure-regulating burner etc. The mechanism by which chemical inhibition occurs when certain powders are added to fuel-air flames was shown and discussed. Moreover, the exhaust properties and electron density of solid propellants were modeled and calculated. Finally, future research trends are suggested from different perspectives involving the KOH testing inside the solid rocket motors, plume signature testing and novel insoluble K compounds.