Ultrafine aluminium: Quench collection of agglomerates
Addition of micron-sized aluminum powder in solid propellant increases the specific impulse whereas it also contributes thrust loss due to two-phase flow. In this context, agglomeration feature of ultra-fine aluminum in solid propellant combustion is investigated using experimental study. The synthesized ultra-fine aluminium powder is used with the intensity weighted harmonic mean size of 438nm which is produced by Radio Frequency Induction Plasma technique. Quench particle collection technique is adopted to estimate the aluminum agglomerate measurement over the pressure ranges from 2MPa to 8MPa. The flame quenching distance from the propellant burning surface is varied from 5mm to 71mm to estimate the effect on agglomerate size. The XRD and XPS results of the agglomerates shows that the aluminium content decreases and alumina content increases far away from the burning surface, invariably represents the initiation of combustion process over the considered quenching distances. Ultra-fine aluminum powder exhibits significant agglomeration with the size ranging from 11 – 21 μm. This will substantially benefit from exhaust signature point of view and also reduction in two-phase flow losses to thrust in contrast to micron sized-aluminum particles.