Numerical Simulation of Emitter Geometry Impact on Electrospray Properties and Its Potential Applications in Electrospray Thruster Systems
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| Publicado en: | PQDT - Global (2025) |
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ProQuest Dissertations & Theses
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| Acceso en línea: | Citation/Abstract Full Text - PDF |
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| Resumen: | Electrospray (ES) thrusters have emerged as promising propulsion systems for small satellites, particularly CubeSats, due to their high efficiency and precise thrust control, although further performance improvements remain possible. The charge-to-mass ratio is a key factor dependent on the electrospray current and directly influences thrust and efficiency. This current is significantly affected by various physical and electrical parameters, including volumetric flow rate, electric potential, and fluid properties. This study investigates the impact of emitter geometry on electrospray current production using heptane-based numerical simulations, with findings relevant to ES thruster applications.To address the complexity and time constraints of experimentally manufacturing emitters with specific geometric variations, a two-dimensional (2D) axisymmetric computational model was developed in OpenFOAM. The model employs the Volume-of-Fluid (VOF) method in conjunction with the leaky-dielectric model to simulate fluid-electric interactions. Numerical simulations enable the visualisation of electric field distributions, which are challenging to measure experimentally. This model captures both pulsating and stable cone-jet modes, offering a more complete representation of jet behaviour. Additionally, this study analyses multiple emitter geometries within a unified simulation framework.The custom numerical model developed was validated through various tests. Simulation variations in flow rates closely matched experimental data using heptane + 0.1% Stadis fluid. Based on the experimental data points, the simulated current and flow rate followed a power law with an exponent within 7% of the experimental value, demonstrating high accuracy in the model’s predictions. A linear relationship was observed for the non-dimensional current, I/I0, as a function of dimensionless flow rate, (Q/Q0)1/4. The model’s gradient varied by 0.45% and the y-intercept by 3% from experimental data. Additionally, as the flow rate increased, the current component ratio, Iconv/Icond, decreased, a trend that is challenging to capture experimentally. The non-dimensional droplet diameter, dd/d0, also followed the expected scaling law. The model captured the jet breakup into droplet formation, providing better insight into the ES process and predictive capability. Further investigation was conducted on the effect of relative humidity through adjustments in air electrical conductivity. Results showed that increasing the surrounding medium’s electrical conductivity led to higher current production. Comparisons of different domain sizes indicated that the smaller domain setup closely matched experimental data, except in the electric potential analyses, where the larger domain showed better agreement. Variations in electric potential were found to influence cone-jet shape and current production.Alternative emitter geometries, including fillet rectangle, tapered, hole, and fillet hole emitters, were analysed using the rectangle emitter as a benchmark to observe the impact of geometric properties. Tapered emitters demonstrated the highest current, which is attributed to their sharp taper angles. Fillet radius was found to positively affect current in both fillet rectangle and fillet hole designs. This is the first known study of the current production using hole emitter geometry for the ES process in the OpenFOAM framework. Furthermore, the influence of three dielectric materials, PEEK, Polyimide, and Teflon, was assessed by applying them along the flat plate of the hole emitter to evaluate their impact. PEEK retained the highest electric potential along the radial distance and produced the highest current, followed by Polyimide and Teflon.The findings of this research contribute to the advancement of ES thruster technology and, more broadly, to ES technology by providing a deeper understanding of the effects of emitter configurations. The results offer insights into how more efficient ES propulsion systems can be designed, enabling improved thrust-to-power ratios and enhanced emission control for space applications. |
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| ISBN: | 9798297673007 |
| Fuente: | ProQuest Dissertations & Theses Global |