1,721,004 research outputs found
Paraffin-Based Solid Fuels for Hybrid Propulsion Filled with Lithium Aluminum Hydride: Thermal, Mechanical and Ballistic Characterization
No full textA chemical, thermal, mechanical and ballistic investigation of paraffin-based solid fuels filled with Lithium Aluminum Hydride (LiAlH4, LAH) for hybrid propulsion is presented in this paper. Two different formulations containing 5% and 10% of a styrene-based thermoplastic elastomer (Polystyrene-block-poly(ethylene-ranbutylene)-block-polystyrene grafted with maleic anhydride, hereafter named SEBSMA) were investigated for the strengthening of paraffin waxes. Two LAH mass fractions were considered for each paraffin-based blend (5% and 10%), for a total of four fuel formulations. The paraffin-based blends filled with LiAlH4 were found to be stable when exposed to air. Rheological properties were investigated using a parallel plate giving evidence of the link between the elastic modulus (G’) evolution and the thermal behavior of LAH. Thermal properties were studied using a differential scanning calorimeter (DSC) leading to obtain data about the transitions typical of paraffin waxes (solid/solid and solid/liquid) and also about the thermal decomposition of the added energetic filler. A manufacturing technique for the production of homogeneous blends strengthened with SEBS-MA and filled with LAH is described. Firing tests were performed in a lab-scale hybrid motor using gaseous oxygen; the local and instantaneous regression rate was measured using a fiber optic technique. The behavior of paraffin waxes blended with the selected SEBS-MA thermoplastic elastomer and filled with LAH, is discussed
Experimental Visualizations of Entrainment Phenomena in Wax-Based Fuels for Hybrid Space Propulsion
No full textThe entrainment is a physical phenomenon that concerns the transport of bubbles, droplets and, in general, particles that are spread in a fluid stream. Studies on the entrainment are very important for hybrid rocket engines that use liquefying fuels. These materials form a thin liquid layer. If the liquid film is stressed by aerodynamic forces it becomes unstable and at the liquid-gas interface waves are formed. When the forces acting on the interface are large enough some waves detach from the liquid phase; the liquid structures, in the gas phase, brake up in many droplets. The physical properties of the fuel spray define the heat and mass transfer that occurs in hybrid motors during the combustion processes. “Physical properties” are basically the detach rate of the droplets, their size, and distribution speed. This paper describes the procedure to measure the diameters of the droplets. The entrainment is reproduced, in frozen conditions, in an experimental setup which allows the process recording thanks to a fast-digital-camera. Pure wax, wax added with 5% of Sebs and wax with 15% of Sebs are the investigated fuels. Oxygen is the gas used. The results obtained by a detailed analysis are reported
Preliminary kinetic characterization of lithium-aluminum based hydrides for airbreathing propulsion
Full text linkThe aim of this research is to present a preliminary experimental investigation on the behavior of lithium-aluminum complex hydrides when exposedtogaseous nitrogen in the range of 20-350°C for airbreathing propulsion applications. This specific task is part of the long-term project devoted to the use of lithium-aluminum hydrides in airbreathing propulsion applications.Itisknown that a launch system based on the airbreathing technology, byusing air as oxidizer, reduces the cost per kilogramof the launch;itistherefore much more profitable than common rocket engines (solid and liquid rockets). The effect of nitrogen gas on the thermal behavior and the kinetic parameters of lithium-aluminum hydride and trilithium-aluminum hydride has been investigated. Differential scanning calorimeter tests, performed using nitrogen gas, have shown the presence ofa strong exothermic peak that, when using heliumorargon gas,isbarely noticeable. A nitridation reaction has been suggested to explain the increase of the sample mass after each differential scanning calorimeter test, which supports the experimental data. The activation energy Ea and frequency factor A for the samples of lithium-aluminum hydride and trilithium-aluminum hydride have been calculated using two simplified kinetic methods: the Ozawa method and the Kissinger method
Paraffin-based Solid Fuels for Hybrid Propulsion Filled with Lithium Aluminum Hydride: Thermal, Mechanical and Ballistic Characterization
Full text linkA chemical, thermal, mechanical, and ballistic investigation of paraffin-based solid fuels filled with lithium aluminum hydride [(LAH) LiAlH4] for hybrid propulsion is presented in this paper. Two different formulations containing 5% and 10% of polystyrene-block-poly(ethylene-ran-butylene)-block- polystyrene, a styrene-based thermoplastic elastomer [i.e., styrene-ethylene-butylene-styrene grafted with maleic anhydride (SEBS-MA)], were investigated to strengthen paraffin waxes. Two LAH mass fractions were considered for each paraffin-based blend (5% and 10%), for a total of four fuel formulations. The paraffin-based blends filled with LiAlH4 were found to be stable when exposed to air. The rheological properties were investigated using a parallel-plate rheometer giving evidence of the link between the elastic modulus (G′) evolution and the thermal behavior of LAH. The thermal properties were studied using differential scanning calorimetry in order to obtain data on the typical transitions of paraffin waxes (solid/solid and solid/liquid) and also on the thermal decomposition of the added energetic filler. A manufacturing technique for the production of homogeneous blends strengthened with SEBS-MA and filled with LAH is described. Firing tests were performed in a laboratory-scale hybrid motor using gaseous oxygen; the local and instantaneous regression rates were measured using a fiber-optic technique. The behavior of paraffin waxes blended with the selected SEBS-MA thermoplastic elastomer and filled with LAH is discussed
Relative Comparison of Additives-Filled Solid Fuels and Grain Geometry Effects on Regression Rate in Hybrid Rocket Propulsion
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Effects of Metal Oxides on the Burning Rate of Ammonium Nitrate Based Solid Rocket Propellants
No full textPure Paraffin Waxes Analysis for Hybrid Rocket Solid Fuels: Rheological, Thermal and Mechanical Characterization
No full textA Wide Characterization of Paraffin-based Fuels Mixed with Styrene-based Thermoplastic Polymers for Hybrid Propulsion
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