1 / 7

Assessing Mechanisms Responsible for Non-Homogenous Emitter Electrospray from Large Arrays of FEEP and Colloid Thruste

Assessing Mechanisms Responsible for Non-Homogenous Emitter Electrospray from Large Arrays of FEEP and Colloid Thrusters. Emitter Operation. liquid metal ion – FEEP Thruster atomic ions relatively large electric field high efficiency liquid metals do not wet Si.

eitan
Download Presentation

Assessing Mechanisms Responsible for Non-Homogenous Emitter Electrospray from Large Arrays of FEEP and Colloid Thruste

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Assessing Mechanisms Responsible for Non-Homogenous Emitter Electrospray from Large Arrays of FEEP and Colloid Thrusters

  2. Emitter Operation • liquid metal ion – FEEP Thruster • atomic ions • relatively large electric field • high efficiency • liquid metals do not wet Si • ionic liquid ion – Colloid Thruster • charged droplets • alternate droplet charge capillary feed concept • mN range for thrust – requires cluster of emitters • geometry not optimized • single emitter geometry (capillary, slit, ring, needle, …) • array spacing • unstable emitter operation • non-homogenous ion emission from arrays of emitters Lozanoand Martinez-Sanchez (2005)

  3. Non-Homogenous Emitter Electrospray • Mechanisms investigated: • internal and external liquid feed structures • charge depletion with ionic liquids (AC potential) • wetting characteristics • extrusion electrode geometry single emitter considerations • Mechanisms not yet investigated: • thin film stability • surface tension flows (Marangoni) • body & surface forces via charge • film rupture (dispersion forces) • capillary-driven flow (curvature) dependent upon: • single emitter geometry • single emitter operation • array geometry • array operation Goal is stable liquid feed with homogenous electrospray over emitter array.

  4. thin film stability • surface temperature variations drive Marangoni flow • body forces drive convective flows • (gravitational, ion drag, …) • charge accumulation on surface may perturb film • evaporation changes surface temperature • vapor (ion) recoil may perturb film • dispersion forces drive film rupture Film stabilizing/destabilizing mechanisms not understood. Pliq,needle = s/R(z) curvature-induced flow Pliq,base = s(1/r – 1/Rbase) • neglecting gas pressure: • liquid pressure decreases towards base of cone • liquid pressure increase at base due to 1/r • liquid pressure lowest in film Pliq,film = 0 Requires external force to stabilize liquid film.

  5. Technical Approach – Film Stability Surface Tension - Disjoining Pressure Surface Tension - Gravitational One-sided linear stability film evolution: • begin with 1D formulation to determine primary film destabilization mechanisms • conduct simple validation experiments • develop 3D formulation for assessing film stability for specific emitter geometries

  6. Technical Approach – Minimum Energy Film Morphology Surface Evolver – Energy Minimization Code Minimum energy morphology for fixed liquid volume in a flattened tube for various contact angles. Braun (2008) Minimum energy and linear stability map for liquid in a cylindrical tube. Allen, Son & Collicott (2009) • Use Surface Evolver to: • determine low energy liquid morphology for emitter array • determine linear stability limits of each morphology • optimize array geometry for stable liquid feed to emitter tips

  7. Anticipated Results • Establish stable liquid film: • define the coupling of mechanisms of which stabilize or destabilize thin liquid films – both metal and ionic liquids • validate stability model with planar film experiments • predict film destabilization modes for emitter geometries • optimize emitter geometry and array pattern for stable film morphology • Establish stable, homogenous elecrospray: • stable, uniform liquid feed to array of electrodes • define envelope for operating conditions

More Related