| Summary: | 碩士 === 國立成功大學 === 航空太空工程學系碩博士班 === 101 === In recent years, hybrid rocket attracts intensive research and application attentions in space propulsion in the new era. It is used not only for civil and atmospherical survey, but also for verifying scientific and technical payloads in sounding rocket programs. Hybrid rockets combine the advantages of solid and liquid rockets and avoid their shortcomings of un-throttlable and store problems of solid and liquid problems respectively so that it becomes a cost-effective, and safe alternative to the traditional rockets. Upon these advantages, hybrid rockets still suffer from the problems of low regression rate and lower specific impulse (Isp). There are some solutions to these problems, including adopting swirling injector, changing the fuel ingredient, modifying the port geometry and mixing with energetic additives.
In this research, the micro aluminum powder is added into the 50P (containing 50% HTPB and 50% paraffin) fuel grain, and surfactant is utilized to disperse the powder in the fuel grain. Also, the swirling injector for liquid oxidizer (N2O) is used to increase the regression rate. In the experiment, a small metal case of 35mm x 27mm is used to prime the fuel grain, and the fuel grain is cut into five equal parts in longitudinal and three equal parts in circumferential directions to examine the uniformity of the powder dispersion in the fuel grain. And then, by measuring the density, the dispersion uniformity can be estimated and the optimal Al/surfactant (span-85) ratio is found to be 5:1 in the cases of current study. The performance of the hybrid rocket propellant grains with optimal ratio of alumina powder is then compared with that without alumina powder. In order to acquire the chamber pressure and thrust for the performance, the fuel grains are integrated into the motor for hot fire tests. The Isp (specific impulse), equivalent ratio, oxidizer flux and the regression rate are measured and calculated. Between 250kg/m2-sec and 400kg/m2-sec of the oxidizer flux, the regression rate of metalized fuel and non-metallized fuel are and , respectively. According to the results, when the oxidizer flux is 370 kg/m2-s, the regression rate of metalized fuel grain increases about 40% comparing with the plain 50P fuel grain. Also, the equivalent ratio is increased and the erosion in the nozzle is reduced. The characteristic curve for the thrust with respect to oxidizer flux reduced from the experimental results will become a useful database and reference for the future development of metalized hybrid rocket.
|
|---|
