Abstract

Innovative, mechanically activated Al–polytetrafluoroethylene (PTFE) composites and ammonium perchlorate (AP) coated nano-sized aluminum (C-ALEX) were produced, characterized, and tested as solid fuel additives. The ballistics of fuel formulations based on hydroxylterminated polybutadiene (HTPB) was investigated in a microburner by a time-resolved technique for regression rate (rf) data reduction. Both Al-composites show promising results in terms of rf and mass burning rate enhancement. In particular, the C-ALEX showed a percent rf increase over the baseline (HTPB) of 27% at an oxidizer mass flux of 350 kg/(m2s), without requiring dedicated dispersion procedures. This performance enhancement was nearly constant over the whole investigated range.

Highlights

  • In a hybrid rocket engine (HRE), the fuel and the oxidizer are stored in different states of matter

  • The analysis focuses on the eects of the energetic additives on the solid fuel rf

  • The solid fuels are tested in gaseous oxygen (GOx), with pc = 1.0 MPa

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Summary

Introduction

In a hybrid rocket engine (HRE), the fuel and the oxidizer are stored in different states of matter. In the most commonly implemented and investigated con¦gurations (direct hybrid), the oxidizer is liquid (or gaseous) while the fuel is solid. The combustion can take place only when the oxidizer §ows over the solid fuel grain. When compared to mature liquid rocket engines and solid propellant motors, HREs oer interesting features as high operating §exibility and theoretical performance, increased safety, and reduced recurring costs [1]. The use of the hybrid con¦guration in operating missions is hampered by HREs low rf and combustion e©ciency. Both of these drawbacks of hybrid systems are related to the diusive nature of the §ame ruling the combustion process [1, 2]. The limits of low rf (and m‘ f ) and of the poor combustion e©ciency hinders HRE implementation in high-thrust applications (i. e., launch systems) and in-space missions (where high eective speci¦c impulse is required to minimize launched masses)

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