Abstract Droplet entrainment offers paraffin fuels a regression rate of 3–4 times higher than classical polymer fuels, which is favorable for the hybrid rocket motor, however, the heterogeneous combustion reactions between droplets and oxidizer lead to a more complicated combustion mechanism. Combustion diagnosis was carried out for paraffin fuels combusted in a windowed 2D slab burner, and the boundary layer combustion was investigated by using high speed camera and schlieren in this study. The results showed that the presence of remarkable periodic flame and chamber pressure oscillation was due to the periodic accumulation and breakdown of liquid film layer; Kelvin−Helmholtz instability was a necessary but not the sufficient condition for droplet entrainment, and the critical oxidizer mass flux of Kelvin−Helmholtz instability and droplet entrainment was about 12.31 kg m−2 s−1 and 30.15 kg m−2 s−1; the thickness of turbulent boundary layer and the height of combustion flame were inversely correlated with the oxidizer mass flux, indicating the more efficient combustion under higher oxidizer mass flux; the entrainment droplets disappeared at elevated chamber pressures due to the inhibition of Kelvin−Helmholtz instability, meanwhile, the thickness of turbulent boundary layer was found to increase; entrainment droplets increased and the height of combustion flame decreased due to the acceleration of combustion reactions when the copper chromite was used as the combustion catalyst, which favored the enhancement of the regression rate of fuels and the combustion efficiency of hybrid rocket motors.
Highlights Remarkable periodic flame and chamber pressure oscillation during the combustion of paraffin fuels were found and analyzed. Combustion flame and boundary Layer Characteristics for the stable combustion of paraffin fuels were studied. Effect of oxygen mass flux, chamber pressure and catalysts on the combustion of paraffin fuels was investigated.
Boundary layer combustion of paraffin fuels for hybrid propulsion applications
Acta Astronautica ; 193 ; 338-345
2022-01-22
8 pages
Article (Journal)
Electronic Resource
English
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