Abstract
In the last decades, hybrid rocket engines have been increasingly studied and used in space vehicles. However, the low regression rates and specific impulses still represent major drawbacks to this technology. The objective of this study was to quantify the relative improvement of regression rate values with the use of a swirling flow injector in comparison to an axial injector. Seven tests were conducted with axial injection and seven with swirl injection. Regression rate results were compared, and it was found that swirl injection improved regression rates in 50% for mass fluxes higher than 45 kg∙s -1 ∙m -2 . It was possible to see radiation, kinetic and diffusion theory on the logarithmic plot of regression rate per oxidizer flux yielded by both injectors. A strong agreement with experimental findings of regression rates in the literature parameters is reported.
Highlights
In the quest for a novel propulsion technology, the hybrid rocket engine draws attention due to features such as thrust tailoring and lower investment costs in comparison to solid motors and liquid engines (Pastrone 2012)
Combustion inefficiencies and low regression rates are the major weaknesses of this technology
This research aims to contribute to the improvement of the regression rates with the use of swirl injectors
Summary
In the quest for a novel propulsion technology, the hybrid rocket engine draws attention due to features such as thrust tailoring and lower investment costs in comparison to solid motors and liquid engines (Pastrone 2012). Combustion inefficiencies and low regression rates are the major weaknesses of this technology. The flame zone is established within the boundary layer, in which the solid fuel has to melt and vaporize or pyrolyze as well as mix with the oxidizer in the flame zone as shown in Fig. 1 (Marxman and Gilbert 1963). In this way, hybrid combustion phenomena differ from what occurs in liquid and solid motors, where the flame is pre-mixed and no relevant energy is spent mixing fuel and oxidizer
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