Combustion Characteristics of Aluminum-Water Gelled Composite Propellant

摘要

An experimental investigation was conducted to study the combustion characteristics of aluminum and water,gelled using polyacrylamide as gelling agent. These propellants were tested for burn rates and residue in a Crawfordbomb. The present study used flakelike aluminum particles with large specific surface area (~22.5 m2/g ) calledpyral. Burn rates and residue were measured for oxidizer-to-fuel ratios (O/F) of 0.8,1,and 1.2. Gelled propellantsprepared with pyral had a maximum burn rate of 7.5 nim /s at 60 bar pressure at an O/F of 0.8. However,thesepropellants had a very large residue of 70-80% of the initial mass. To overcome this,propellants were prepared withpyral,which was mechanically activated with polytetrafluoroethylene. The reduction in residue was mainlyattributed to smaller thermal profile depth associated with mechanically activated aluminum and to the higher heat ofcombustion observed with such propellants. Through careful experimentation,the reason for the residue has beenestablished to be due to heat loss from the sides of the propellant strand. The thermal conductivity and propellantdiameter play a vital role in determining the heat loss from the condensed phase and in turn determining burn ratesand residue.