Experimental Evaluation of a Nitrous-Oxide Axial-Injection, End-Burning Hybrid Rocket

• Published in: Journal of propulsion and power 2017-11, Vol.33 (6), p.1555-1560
• Main Authors: Hitt, Matthew A, Frederick, Robert A
• Format: Article
• Language: English
• Subjects: Burning rate; Flame structure; Flow velocity; Mathematical models; Nitrous oxide; Oxidizing agents; Polyethylenes; Qualitative analysis; Regression analysis; Solid fuels
• ISSN: 0748-4658; 1533-3876
• DOI: 10.2514/1.B36439

This experimental and theoretical work examines the effects of gaseous oxidizer flow rates and pressure on the regression rates of porous fuels for hybrid rocket applications using polyethylene as the porous fuel and gaseous nitrous oxide as the oxidizer as a continuation of previous work performed at the University of Alabama in Huntsville. Nominal test articles were tested using 100  μm nominal fuel pore sizes. Pressures tested ranged from 207 to 1054 kPa, and oxidizer injection velocities ranged from 7.5 to 16.8  m/s. Regression rates were determined using pretest and posttest length measurements of the solid fuel. Experimental results supported previous work demonstrating that the regression rate of the porous axial-injection, end-burning hybrid was a function of the chamber pressure as opposed to the oxidizer mass flux typical in conventional hybrids. Regression rates ranged from approximately 0.21  mm/s at 207 kPa to 1.44  mm/s at 1054 kPa. The experimental results were compared to an analytical model developed in previous work for qualitative agreement. The model showed qualitative agreement with the experimental results, indicating that it has potential for giving insight into the flame structure in this propellant combination.