Experimental and model investigation on agglomeration of aluminized fuel-rich propellant in solid fuel ramjet

Abstract

In order to gain insight into aluminum agglomeration behaviors and agglomeration processes, the aluminized fuel-rich propellants in solid fuel ramjet are investigated by using sampling method followed by scanning electron microscopy and laser scattering experimental technique on the small-scale combustion experimental system and connected-pipe experimental system. It is observed that the aluminum particles would break away from the burning surface after agglomeration, and interpocket agglomeration occurred. Under different ambient pressures, the microstructure of the combustion products and the aggregation behavior of aluminum particles are further analyzed. Based on the classical pocket theory and particle size analysis experiments, a new agglomeration size prediction model is established. It can be used to predict the agglomeration size on the burning surface. Compared with the empirical model and the typical pocket model, this model is in good agreement with the experimental results. A connected-pipe experimental system for solid fuel ramjet is established. The effects of inlet air temperatures on the combustion performance of ramjet, the microstructure and agglomeration size are studied. With the increase of inlet air temperature, the agglomeration size decreases, the pressure, temperature and thrust in the combustion chamber increase, which makes the propellant burn more fully. The characteristic velocity, specific impulse and combustion efficiency of the solid fuel ramjet increase.