Reduction of agglomeration effect by aluminum trihydride in solid propellant combustion

Abstract

Aluminum trihydride (AlH₃) has gained considerable attention as a substitute fuel for aluminum in solid propellants. In this study, we conducted a systematic investigation to evaluate the effects of AlH₃ content, ranging from 0 % to 18 %, on propellant ignition, combustion, and agglomeration. Experimental methods such as thermogravimetry−differential scanning calorimetry (TG-DSC), laser ignition, high-speed photography, and collecting condensed combustion products (CCPs) were employed. The results indicate that AlH₃ significantly promotes the high-temperature decomposition of ammonium perchlorate (AP). Meanwhile, the addition of cyclotetramethylene tetranitramine (HMX) in propellant does not affect the hydrogen release reaction of AlH₃. As the AlH₃ content increases from 0 % to 18 %, the spectral emission intensity of the propellants decreases, and the ignition delay time initially increases from 253 ms to 321 ms, and then decreases to 258 ms. Furthermore, the burning rate increases with increasing the AlH₃ content, while the pressure exponent is reduced from 0.551 to 0.460. The inclusion of AlH₃ in propellants significantly inhibits aluminum agglomeration near the burning surface. Additionally, as the AlH₃ content increases, the mean particle size D₄₃ of the CCPs decreases from 50.95 μm to 8.28 μm at 1 MPa. The agglomeration degree of aluminum is very weak at 7 MPa, especially when the AlH₃ content exceeds 9 %. The conclusions drawn from this study can serve as valuable guidance for optimizing propellant formulations.