Analysis of the Electrospray Plume from the EMI-Im Propellant Externally Wetted on a Tungsten Needle

Chiu, Yu‐Hui; Gaeta, Geraldine; Heine, Thomas; Dressler, Rainer A.; Levandier, Dale J.

doi:10.2514/6.2006-5010

Cited by 16 publications

(12 citation statements)

References 12 publications

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“…The elevated baseline reading between ±15°, which has been observed previously in needle mass spectra, is attributed to large m/q species that are not completely filtered out by the mass filter and reach the detector. 22,23 It is possible to use the intensity trend of each species to approximate the location of origin of that species in the Taylor cone. Maximum n = 0 cation intensities are observed at high angle values.…”

Section: Resultsmentioning

confidence: 99%

Capillary Extraction of the Ionic Liquid [Bmim][DCA] for Variable Flow Rate Operations

Miller¹,

Prince²,

Rovey

2012

48th AIAA/ASME/SAE/ASEE Joint Propulsion Conference &Amp;amp; Exhibit

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The ionic liquid [Bmim][DCA] is a propellant candidate in a standalone electrospray thruster or in a dual-mode propulsion system consisting of a chemical system and an electrospray system. Since limited published data exists for [Bmim][DCA], the electrospray characteristics are relatively unknown. Emission testing of the ionic liquid has been conducted to characterize the [Bmim][DCA] electrospray plume for both an external flow titanium needle and internal flow capillary. Mass spectrometric, retarding potential, and angle distribution measurements were collected for the positive polarity ions emitted from [Bmim][DCA] wetted emitters with nominal extraction voltages between ~1 kV to ~2.5 kV. The titanium needle operated at a sizably reduced liquid flow rate in comparison to the capillary. As such, only the major species of Bmim + ([Bmim][DCA]) n with n=0,1 were identifiable in the quadrupole measurement range of 0-1000 amu and were formed at or near the needle potential. A typical needle angle distribution was found in these measurements. For the capillary emitter, flow rates from 0.27 nL/s to 2.18 nL/s were used to investigate corresponding alterations in the electrospray beam. The aim of the investigation was to ascertain the ability to "tune" or "dial-in" an electrospray thruster to specific ion or droplet sizes and thus specific performance levels. Unlike the limited species observed from the needle emission, the capillary measurements indicated the presence of n=0,1,2,3,4 cation species with large mass droplet contributions. The lowest flow rates indicated the highest levels of ions in the measurement range of 0-1000 amu with a mix of large mass droplets. For increasing flow rate, species < 500 amu ceased to exist leaving only the n=2,3,4 species mixed with large mass droplets in the electrospray beam. All ion species exceeded the quadrupole mass range at the upper flow rates. Ions emitted from the capillary were formed at levels below the emitter potential. Ohmic losses in the ionic liquid are likely the cause for the less energetic ions. Angular distribution measurements indicated broadening of the beam current and mass distribution for increasing flow rates. Nomenclature D c = transport capillary inner diameter (µm) D n = capillary needle emitter inner diameter (µm) K = ionic liquid electrical conductivity (S/m) L c = transport capillary length (cm) L n = capillary needle emitter length (cm) P 0 = reservoir pressure (Torr) P VC = vacuum chamber pressure (Torr) 2 P n = capillary needle emitter pressure (Torr) q/m = specific charge (C/kg) Q = ionic liquid volumetric flow rate (nL/s) V N = emitter voltage (V) V Ext = extractor plate voltage (V) β n = capillary length/diameter ratio coefficient γ = ionic liquid surface tension (N/m) ε = ionic liquid dielectric constant µ l = ionic liquid viscosity (cP) ρ = ionic liquid density (kg/m 3 )

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Section: Resultsmentioning

confidence: 99%

Capillary Extraction of the Ionic Liquid [Bmim][DCA] for Variable Flow Rate Operations

Miller¹,

Prince²,

Rovey

2012

48th AIAA/ASME/SAE/ASEE Joint Propulsion Conference &Amp;amp; Exhibit

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“…At lower field strengths, a range of cluster sizes can be produced. This is observed in the molecular-beam/mass-spectrometry measurements of Chiu et al [14], as described in the Introduction. …”

Section: Discussionmentioning

confidence: 66%

“…In recent work, Chiu et al [14] used molecular beam/mass spectrometry to analyze the plume of an electrospray with 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMI-Im) † as the propellant. They showed that for the operating conditions imposed, at least two positive ion cluster sizes and a background that is likely fragmented droplets are observed.…”

Section: Introductionmentioning

confidence: 99%

Molecular Dynamics Simulation of Ion Emission from Nanodroplets of Ionic Liquids

Daily

2008

Journal of Propulsion and Power

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The work reported here is motivated by a desire to fully understand the physics of colloidal thruster propulsion technology. Colloidal thruster technology is based on the electrostatic acceleration of small droplets and/or ions that are generated by feeding a conducting fluid through a small capillary and applying a large acceleration potential between the capillary and an extraction electrode. Maximum thrust is obtained when the device is operated in the droplet mode. However, by transitioning to an ion mode, the specific impulse can be greatly increased. Here, we use molecular modeling to study the dynamics of small droplets of ionic liquids (EMIM-BF4) in the presence of large external electric fields. Interatomic and molecular forces are described using a molecular mechanics force field, and the whole ion structure is included. Before an electric field is applied, minimization methods are used to determine the equilibrium structure of the droplet. An electric field is then applied and the resulting motions of droplets and individual ions are observed. In addition, the surface tension of the droplets is calculated from the dynamic simulations. Surface tensions calculated from the simulations agree with macroscopic experimental values within uncertainty. Thus, the results indicate that the Taylor expression for the critical electric field for droplet ionization is order-of-magnitude-correct.

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“…Also, since most metals have very high melting points, the choice of propellant is limited to a few low melting metals and alloys. For these reasons, in recent years, ionic liquids have been described as ideal propellants for electrospray thrusters due to their negligible vapor pressures, high electrical conductivities, low melting temperatures, and wide liquid temperature range . Furthermore, because the physical properties can be tuned, key properties affecting the hydrodynamics, such as viscosity and surface tension, can be also optimized for this application.…”

Section: Space Propulsionmentioning

confidence: 99%

“…Although, in this particular study, the specific impulse ( I sp = 292 s, for a mass flow rate

\overset{\cdot}{m}

= 2.1 × 10 −10 kg s −1 and an acceleration voltage V A = 5000 V) was found to be too low to be considered in electrospray thrusters, the authors indicated their expectation that, with future optimization in terms of the choice of IL and operating conditions, ionic liquids should prove to be excellent electrospray propellants. [C 2 mim][NTf 2 ] was later investigated by NASA for the Space Technology 7 – Disturbance Reduction System Mission (ST7‐DRS) and passed the space environment tests .…”

Section: Space Propulsionmentioning

confidence: 99%

Ionic Liquids in Space Technology – Current and Future Trends

Nancarrow

Mohammed

2017

ChemBioEng Reviews

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The space technology industry has been at the forefront of technological innovation since the late 1950s. In recent years, ionic liquids (ILs) have gained increasing attention in a wide range of space‐related applications, due to their advantageous properties such as non‐volatility and wide liquid temperature range. In particular, the ability to design ILs with optimal physical and chemical properties for a given application has allowed them to be employed in a wide range of studies. In this review paper, an overview of ionic liquids and their properties in the context of space technology applications is given. Recent studies into the use of ionic liquids in space propulsion, space lubrication, thermal control, composite materials, space telescopes, and life support systems are reviewed and discussed. Furthermore, where applicable, the potential future trends for ILs in space applications are highlighted.

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Analysis of the Electrospray Plume from the EMI-Im Propellant Externally Wetted on a Tungsten Needle

Cited by 16 publications

References 12 publications

Capillary Extraction of the Ionic Liquid [Bmim][DCA] for Variable Flow Rate Operations

Capillary Extraction of the Ionic Liquid [Bmim][DCA] for Variable Flow Rate Operations

Molecular Dynamics Simulation of Ion Emission from Nanodroplets of Ionic Liquids

Ionic Liquids in Space Technology – Current and Future Trends

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