ABSTRACT Paraffin waxes are evolving to be an important unique solid fuel in the field of hybrid propulsion. This is because of their ability in enhancing the regression rate, nearly three times more than that of the classical fuels for hybrid propulsion. Paraffin waxes melt when exposed to temperature and they form a thin, hydrodynamically unstable liquid layer on the surface of the fuel. As the fuel regresses, this liquid layer forms liquid droplets making it easy to be entrained. This results in the increase of mass of fuel entrainment which, in turn, results in the increase of regression rate. But, paraffin waxes, having known for their poor mechanical properties, it cannot be used as such as a solid fuel. In order to have a trade-off between the mechanical and the ballistic properties, addition of polymer with paraffin wax is a better option as of now to improve their mechanical property. This work is focused on a particular polymer, Styrene Ethylene Butylene Styrene, known as SEBS. The kind of SEBS used for this work is Polystyrene-block-Polyethylene-Polybutylene-block-Polystyrene grafted with a small proportion of Maleic Anhydride (SEBS-MA). SEBS is also an evolving polymer that is currently being used for its non-toxic and better mechanical properties along with its tolerance to high temperature. Combining Gel Wax (GW) and SEBS, five compositions have been formulated with 2.5%, 5%, 7.5%, 10% and 20% of SEBS. Since density is an important parameter, density for each formulation has been measured. These compositions were tested categorized by pre-burning and burning characterization in order to have a better trade-off between the mechanical and ballistic properties. Tensile tests were carried out to find about the mechanical properties by a stress-strain curve illustrating the toughness of the fuel. Rheometer and Tensiometer tests were done in order to find viscosity and surface tension values, respectively. The mass of entrainment is related viscosity and surface tension and thus, these tests were important. And, Differential Scanning Calorimetry tests were performed to have an idea about the temperature trend of each composition. These tests are grouped under the pre-burning characterization tests. Finally, for the burning characterization, as the name indicates, firing tests were performed in order to find the ballistic properties of the fuel. The results for each formulation were then compared with their mechanical properties and were discussed about the best suitable formulation with a reasonable trade-off between the mechanical and ballistic properties of the fuel.
SOMMARIO I combustibili solidi a base paraffinica in applicazioni di propulsione spaziale, tipicamente negli endoreattori ibridi, sono oggetto di un crescente interesse in virtù della loro elevata velocità di regressione. Questi combustibili sono caratterizzati dalla proprietà di formare un sottile strato liquido alla superficie del combustibile solido che, instabilizzato dal flusso di ossidante, porta alla formazione di uno spray di gocce; questa rimozione meccanica di combustibile è responsabile del significativo incremento della velocità di regressione rispetto ai combustibili tradizionali. I combustibili a base paraffinica hanno tuttavia scarse proprietà meccaniche e questo rende necessaria l’additivazione delle paraffine con opportuni ingredienti, in grado di consentirne l’utilizzo. Il lavoro di tesi è focalizzato su un particolare polimero, stirene etilene butilene stirene, in acronimo SEBS. Il tipo di SEBS utilizzato per questo lavoro è innestato con una piccola percentuale di anidride maleica (SEBS-MA). Miscelando una paraffina commerciale, denominata GellyWax (GW) con SEBS, sono state prodotte ed indagate cinque composizioni con il 2,5%, 5%, 7,5%, 10% e 20% di SEBS. Le composizioni sono state testate mediante una caratterizzazione di pre-combustione e una caratterizzazione balistica al fine di ottenere il migliore compromesso tra le proprietà meccaniche e balistiche. Sono state effettuate prove di trazione per dimostrare la robustezza del combustibile. Prove condotte al reometro e al tensiometro hanno consentito di trovare rispettivamente i valori di viscosità e tensione superficiale. Inoltre, sono state eseguite prove di calorimetria a scansione differenziale per avere un'idea dell'andamento della temperatura di ciascuna composizione. Queste prove sono presentate nella tesi nella sezione relativa alla caratterizzazione pre-combustione. Infine, per la caratterizzazione balistica sono state eseguite prove di combustione al fine di misurare le proprietà balistiche del combustibile. I risultati per ciascuna formulazione sono stati confrontati con le loro proprietà meccaniche al fine di individuare le formulazioni con il miglior compromesso tra le proprietà meccaniche e le proprietà balistiche del combustibile.
Manufacturing, pre-burning and burning characterization of paraffin-based fuels for hybrid rockets in-space propulsion applications
BALASUBRAMANYAM, LEELA
2017/2018
Abstract
ABSTRACT Paraffin waxes are evolving to be an important unique solid fuel in the field of hybrid propulsion. This is because of their ability in enhancing the regression rate, nearly three times more than that of the classical fuels for hybrid propulsion. Paraffin waxes melt when exposed to temperature and they form a thin, hydrodynamically unstable liquid layer on the surface of the fuel. As the fuel regresses, this liquid layer forms liquid droplets making it easy to be entrained. This results in the increase of mass of fuel entrainment which, in turn, results in the increase of regression rate. But, paraffin waxes, having known for their poor mechanical properties, it cannot be used as such as a solid fuel. In order to have a trade-off between the mechanical and the ballistic properties, addition of polymer with paraffin wax is a better option as of now to improve their mechanical property. This work is focused on a particular polymer, Styrene Ethylene Butylene Styrene, known as SEBS. The kind of SEBS used for this work is Polystyrene-block-Polyethylene-Polybutylene-block-Polystyrene grafted with a small proportion of Maleic Anhydride (SEBS-MA). SEBS is also an evolving polymer that is currently being used for its non-toxic and better mechanical properties along with its tolerance to high temperature. Combining Gel Wax (GW) and SEBS, five compositions have been formulated with 2.5%, 5%, 7.5%, 10% and 20% of SEBS. Since density is an important parameter, density for each formulation has been measured. These compositions were tested categorized by pre-burning and burning characterization in order to have a better trade-off between the mechanical and ballistic properties. Tensile tests were carried out to find about the mechanical properties by a stress-strain curve illustrating the toughness of the fuel. Rheometer and Tensiometer tests were done in order to find viscosity and surface tension values, respectively. The mass of entrainment is related viscosity and surface tension and thus, these tests were important. And, Differential Scanning Calorimetry tests were performed to have an idea about the temperature trend of each composition. These tests are grouped under the pre-burning characterization tests. Finally, for the burning characterization, as the name indicates, firing tests were performed in order to find the ballistic properties of the fuel. The results for each formulation were then compared with their mechanical properties and were discussed about the best suitable formulation with a reasonable trade-off between the mechanical and ballistic properties of the fuel.| File | Dimensione | Formato | |
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Thesis Report_Leela Balasubramanyam_819880.pdf
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https://hdl.handle.net/10589/140439