The entrainment phenomenon in paraffin-based fuel represents a suitable option for improving the regression rate in Hybrid Rocket Engines (HREs). During the combustion of the solid fuel with an atomized (or gaseous) oxidizer, a thin layer of melted fuel is formed on the condensed phase surface. The stresses produced by the oxidizer flow may destabilized the liquid layer, prompting the detachment of liquid fuel droplets from the solid grain surface. This effect promotes increased solid fuel regression rates, limiting the main disadvantage of HRE configuration application to high-thrust systems. However, the mechanistic behavior of the factors which prompt the droplet entrainment is not well known yet. In the open literature, some experiments in cold flow environment are available and the size of the entrained droplets is determined based on an optical measurement technique (i.e., analysis of high-speed video-recorded images). This thesis presents the development of a code to perform a semi-automated processing of high-speed visualization videos of melted paraffin entrainment in a cold flow stream. Such code is capable of detect the moving particles, recognizing them from the background. This approach makes the video processing easier and prepares it for the measuring process in a very effective manner. In addition, this tool has into account the time relation between the frames of the videos. As consequence, besides measuring the droplet size, the script can measure the droplet velocity. In addition to this, the works presents the conceptual design of a test-bench for the visualization of the entrainment during the solid fuel combustion.The entrainment phenomenon in paraffin-based fuel represents a suitable option for improving the regression rate in Hybrid Rocket Engines (HREs). During the combustion of the solid fuel with an atomized (or gaseous) oxidizer, a thin layer of melted fuel is formed on the condensed phase surface. The stresses produced by the oxidizer flow may destabilized the liquid layer, prompting the detachment of liquid fuel droplets from the solid grain surface. This effect promotes increased solid fuel regression rates, limiting the main disadvantage of HRE configuration application to high-thrust systems. However, the mechanistic behavior of the factors which prompt the droplet entrainment is not well known yet. In the open literature, some experiments in cold flow environment are available and the size of the entrained droplets is determined based on an optical measurement technique (i.e., analysis of high-speed video-recorded images). This thesis presents the development of a code to perform a semi-automated processing of high-speed visualization videos of melted paraffin entrainment in a cold flow stream. Such code is capable of detect the moving particles, recognizing them from the background. This approach makes the video processing easier and prepares it for the measuring process in a very effective manner. In addition, this tool has into account the time relation between the frames of the videos. As consequence, besides measuring the droplet size, the script can measure the droplet velocity. In addition to this, the works presents the conceptual design of a test-bench for the visualization of the entrainment during the solid fuel combustion.
L'entrainment nei combustibili a base di paraffina rappresenta un'alternativa adatta al miglioramento del regression rate nei motori ibridi (HRE). Durante la reazione del combustibile con un ossidante atomizzato (o gassoso), sulla superficie della fase condensata si forma un sottile strato di combustibile fuso. Gli sforzi applicati dal flusso dell'ossidante possono destabilizzare lo strato liquido provocando il destacco delle goccioline di combustibile liquido dalla superficie del combustibile solido. Questo effeto promuove un aumento deo tassi di regressione dei combustibile solidi, limitando il principale svantaggio dell'applicazione di configurazione ibrida ai sistema ad alta spinta. Tuttavia, il comportamento dei fattori che provocano l'entrainment non è ancora ben noto. Nella letteratura aperta sono disponibili alcuni esperimenti in ambiente a flusso freddo e la dimensione delle goccioline trascinate è determinata sulla base di una tecnica di misurazione ottica (ad esempio, analisi di immagini video registrate ad alta velocità). Questa tesi presenta lo sviluppo di un codice per eseguire un'elaborazione semiautomatica di video di visualizzazione ad alta velocità di trascinamento di paraffina fuso in un flusso di flusso freddo. Tale codice è in grado di rilevare le particelle in movimento, riconoscendole dallo sfondo. Questo approccio facilita l'elaborazione del video e lo prepara in modo molto efficace per il processo di misurazione. Inoltre, questo strumento tiene conto della relazione temporale tra i frame dei video. Di conseguenza, oltre a misurare la dimensione della gocciolina, lo script può misurare la velocità della gocciolina. Oltre a questo, i lavori presentano la progettazione concettuale di un banco di prova per la visualizzazione del trascinamento durante la combustione del combustibile solido.
Size measurement of entrained droplets in melted paraffin-based fuel formulations
GOMEZ ROSSO, OSCAR IVAN
2016/2017
Abstract
The entrainment phenomenon in paraffin-based fuel represents a suitable option for improving the regression rate in Hybrid Rocket Engines (HREs). During the combustion of the solid fuel with an atomized (or gaseous) oxidizer, a thin layer of melted fuel is formed on the condensed phase surface. The stresses produced by the oxidizer flow may destabilized the liquid layer, prompting the detachment of liquid fuel droplets from the solid grain surface. This effect promotes increased solid fuel regression rates, limiting the main disadvantage of HRE configuration application to high-thrust systems. However, the mechanistic behavior of the factors which prompt the droplet entrainment is not well known yet. In the open literature, some experiments in cold flow environment are available and the size of the entrained droplets is determined based on an optical measurement technique (i.e., analysis of high-speed video-recorded images). This thesis presents the development of a code to perform a semi-automated processing of high-speed visualization videos of melted paraffin entrainment in a cold flow stream. Such code is capable of detect the moving particles, recognizing them from the background. This approach makes the video processing easier and prepares it for the measuring process in a very effective manner. In addition, this tool has into account the time relation between the frames of the videos. As consequence, besides measuring the droplet size, the script can measure the droplet velocity. In addition to this, the works presents the conceptual design of a test-bench for the visualization of the entrainment during the solid fuel combustion.The entrainment phenomenon in paraffin-based fuel represents a suitable option for improving the regression rate in Hybrid Rocket Engines (HREs). During the combustion of the solid fuel with an atomized (or gaseous) oxidizer, a thin layer of melted fuel is formed on the condensed phase surface. The stresses produced by the oxidizer flow may destabilized the liquid layer, prompting the detachment of liquid fuel droplets from the solid grain surface. This effect promotes increased solid fuel regression rates, limiting the main disadvantage of HRE configuration application to high-thrust systems. However, the mechanistic behavior of the factors which prompt the droplet entrainment is not well known yet. In the open literature, some experiments in cold flow environment are available and the size of the entrained droplets is determined based on an optical measurement technique (i.e., analysis of high-speed video-recorded images). This thesis presents the development of a code to perform a semi-automated processing of high-speed visualization videos of melted paraffin entrainment in a cold flow stream. Such code is capable of detect the moving particles, recognizing them from the background. This approach makes the video processing easier and prepares it for the measuring process in a very effective manner. In addition, this tool has into account the time relation between the frames of the videos. As consequence, besides measuring the droplet size, the script can measure the droplet velocity. In addition to this, the works presents the conceptual design of a test-bench for the visualization of the entrainment during the solid fuel combustion.| File | Dimensione | Formato | |
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https://hdl.handle.net/10589/137342