Solid–gas surface effect on the performance of a MEMS-class nozzle for micropropulsion

Moríñigo, José A.; Hermida-Quesada, José

doi:10.1016/j.sna.2010.06.006

Cited by 18 publications

(5 citation statements)

References 11 publications

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“…Moreover, an optimized propulsion nozzle for high injection and ejection efficiency would result in superior performance. [17][18][19][20][21][22][23][24][25][26][27][28][29][30] The proposed micro-Ro-boat primarily requires wiring connections for power transmission. In this study, a thin gold wire (25 m diameter) is used for the power connection of the micro-Ro-boat, but it sometimes obstructed the movement because of the very light weight of the micro-Ro-boat and the large pulling force of the wire.…”

Section: Discussionmentioning

confidence: 99%

Micro-Electro-Mechanical-Systems-Based Micro-Ro-Boat Utilizing Steam as Propulsion Power

Choi

Lee

et al. 2012

Jpn. J. Appl. Phys.

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We report the design and fabrication of a micro-electro-mechanical-systems (MEMS)-based microactuator, that floats on the surface of water and is driven by steam. We named the actuator “micro-Ro-boat”, a compound word created from the words “robot” and “boat”. The MEMS-based micro-Ro-boat utilizes steam as the propulsion power, giving it a high speed and long lifetime. A hydrophobic surface has been utilized for the wing of the actuator to enhance the buoyancy. Instead of using gas or fuel, the proposed micro-Ro-boat utilizes steam form electrically heated water. The velocity of the micro-Ro-boat is in the range of 0.5–2 cm/s and the maximum loading capability for a device size of 10 ×10 mm2 is 0.4 g.

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Section: Discussionmentioning

confidence: 99%

Micro-Electro-Mechanical-Systems-Based Micro-Ro-Boat Utilizing Steam as Propulsion Power

Choi

Lee

et al. 2012

Jpn. J. Appl. Phys.

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“…The length of the diverging part is governed by the diverging angle and the throat-to-exit-area ratio. For a long diverging section with a small angle, there is a risk of increased viscous losses [30], whereas for a short diverging section with a large angle, the net thrust is reduced since the jet will have an increased radial momentum component [31]. This effect can partly be countered with a bell-shaped diverging section.…”

Section: Designmentioning

confidence: 99%

Investigation of exhausts from fabricated silicon micronozzles with rectangular and close to rotationally symmetric cross-sections

Palmer¹,

Catalán²,

Lekholm³

et al. 2013

J. Micromech. Microeng.

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Close to rotationally symmetric in-plane silicon micronozzles with throat and exit diameters of 45 and 260 µm, respectively, have been fabricated using semi-isotropic SF6 etching through an array mask utilizing microloading and reactive ion etching lag. Comparison with nozzles fabricated using deep reactive ion etching (DRIE) and having a rectangular cross-section but a similar hydraulic diameter in the throat, showed that the Reynolds numbers were almost equal even though the DRIE-etched nozzle had an almost five times larger cross-sectional area, hence implying less viscous losses and higher efficiency with the nearly symmetrical nozzles. The nozzle shapes have been studied using x-ray computed tomography. Comparison of the nozzles' exhaust jets using schlieren imaging, showed that the rectangular nozzles' jets deviate from the nozzle axis direction. It is believed that it is caused by the inclined side walls resulting from the DRIE etching. The results from intentionally misaligning the wafers, each containing half a nozzle, 50 µm parallel with or perpendicular to the nozzle axis, showed that the exhaust deviated and widened, respectively. The findings show that the nozzle symmetry affects both the shape and the pointing direction of the exhaust and that schlieren imaging is a powerful tool for determining nozzle thrust vector deviations.

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“…This slip-flow model comprises a 2 nd -order slip-velocity and jump-temperature boundary conditions (BCs) at the wall, which could be consulted in Refs. [9,10] for additional information and thus not repeated here for brevity. Albeit transitional regime is foreseeable to occur in the outer zone of the nozzle (where the slip-model prediction is not accurate), the massflow across the nozzle throat is correctly captured because the slip effect on increasing the passing massflow (and consequently on the reservoir pressurization) is well resolved.…”

Section: Numerical Approachmentioning

confidence: 99%

Multiphysics simulation of a novel concept of MEMS-based solid propellant thruster for space propulsion

Moríñigo

Hermida-Quesada

2011

J. Therm. Sci.

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This work analyzes a novel MEMS-based architecture of submillimeter size thruster for the propulsion of small spacecrafts, addressing its preliminary characterization of performance. The architecture of microthruster comprises a setup of miniaturized channels surrounding the solid-propellant reservoir filled up with a high-energetic polymer. These channels guide the hot gases from the combustion region towards the nozzle entrance located at the opposite side of the thruster. Numerical simulations of the transient response of the combustion gases and wafer heating in thruster firings have been conducted with FLUENT under a multiphysics modelling that fully couples the gas and solid parts involved. The approach includes the gas-wafer and gas-polymer thermal exchange, burnback of the polymer with a simplified non-reacting gas pyrolysis model at its front, and a slip-model inside the nozzle portion to incorporate the effect of gas-surface and rarefaction onto the gas expansion. Besides, accurate characterization of thruster operation requires the inclusion of the receding front of the polymer and heat transfer in the moving gas-solid interfaces. The study stresses the improvement attained in thermal management by the inclusion of lateral micro-channels in the device. In particular, the temperature maps reveal the significant dependence of the thermal loss on the instantaneous surface of the reservoir wall exposed to the heat flux of hot gases. Specifically, the simulations stress the benefit of implementing such a pattern of micro-channels connecting the exit of the combustion reservoir with the nozzle. The results prove that hot gases flowing along the micro-channels exert a sealing action upon the heat flux at the reservoir wall and partly mitigate the overall thermal loss at the inner-wall vicinity during the burnback. The analysis shows that propellant decomposition rate is accelerated due to surface preheating and it suggests that a delay of the flame extinction into the reservoir is possible. The simulated operation of the thruster concept shows encouraging performance.

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Solid–gas surface effect on the performance of a MEMS-class nozzle for micropropulsion

Cited by 18 publications

References 11 publications

Micro-Electro-Mechanical-Systems-Based Micro-Ro-Boat Utilizing Steam as Propulsion Power

Micro-Electro-Mechanical-Systems-Based Micro-Ro-Boat Utilizing Steam as Propulsion Power

Investigation of exhausts from fabricated silicon micronozzles with rectangular and close to rotationally symmetric cross-sections

Multiphysics simulation of a novel concept of MEMS-based solid propellant thruster for space propulsion

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