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- Bejhed, Johan, et al.
(författare)
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Demonstration of a single use microsystem valve for high gas pressure applications
- 2007
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Ingår i: Journal of Micromechanics and Microengineering. - : IOP Publishing. - 0960-1317 .- 1361-6439. ; 17:3, s. 472-481
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Tidskriftsartikel (refereegranskat)abstract
- Demonstrated and characterized here is a single use valve developed for high-pressure applications. Incorporated within the single use valve is a particle filter. The filter serves to remove any particle debris created by the activation process. The valve is solder sealed to be leakage proof. The solder is remelted to obtain activation of the valve. Local heater elements are incorporated on the valve surface together with solder wetting pads. The gas mass flow through the device was evaluated prior to sealing and after activation. The valve was functional at pressures of 100 bar, and opened in less than 10 s with an applied power of 13 W.
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- Bejhed, Johan, 1973-
(författare)
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Fluidic Microsystems for Micropropulsion Applications in Space
- 2006
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Spacecraft on interplanetary missions or advanced satellites orbiting the Earth all require propulsion systems to complete their missions. Introducing microelectromechanical systems technology to the space industry will not only reduce size and weight of the propulsion system, but can also increase the performance of the mission.Fluid handling systems are used in chemical and electric propulsion. Some components incorporated in a fluidic handling system are presented and evaluated in this work.Microsystems are very sensitive to contamination. Reliable, robust, and easily integrated filters were modeled, manufactured, and experimentally verified.A fluid connector, designed to withstand large temperature variations and aggressive propellants was manufactured and characterized. Similar designs was also be used as a thermally activated minute valve.The feasibility of a cold gas system for precise attitude control has been demonstrated. Steps towards improving the performance (from specific im-pulse 45 s) have been taken, by the integration of suspended heater elements.For electric propulsion, two thermally regulated flow restrictors have been characterized. These devices can fine-tune the propellant flow to e.g. an ion engine.A single-use valve using a soldered seal has also been successfully dem-onstrated within a pressure range of 5 to 100 bar.The microsystem-based propulsion systems of tomorrow’s spacecraft need to be demonstrated in space, in order to gain necessary credibility.
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- Bejhed, Johan, et al.
(författare)
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Numerical modeling and verification of gas flow through a network of crossed narrow v-grooves
- 2006
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Ingår i: Journal of Micromechanics and Microengineering. - : IOP Publishing. - 0960-1317 .- 1361-6439. ; 16:10, s. 2006-2013
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Tidskriftsartikel (refereegranskat)abstract
- The gas flow through a network of crossing thin micro-machined channels has been successfully modeled and simulated. The crossings are formed by two sets of v-grooves that intersect as two silicon wafers are bonded together. The gas is distributed from inlets via a manifold of channels to the narrow v-grooves. The narrow v-grooves could work as a particle filter. The fluidic model is derived from the Navier–Stokes equation and assumes laminar isothermal flow and incorporates small Knudsen number corrections and Poiseuille number calculations. The simulations use the finite element method. Several elements of the full crossing network model are treated separately before lumping them together: the straight v-grooves, a single crossing in an infinite set and a set of exactly four crossings along the flow path. The introduction of a crossing effectively corresponds to a virtual reduction of the length of the flow path, thereby defining a new effective length. The first and last crossings of each flow path together contribute to a pressure drop equal to that from three ordinary crossings. The derived full network model has been compared to previous experimental results on several differently shaped crossed v-groove networks. Within the experimental errors, the model corresponds to the mass flow and pressure drop measurements. The main error source is the uncertainty in v-groove width which has a profound impact on the fluidic behavior.
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- Köhler, Johan, et al.
(författare)
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A hybrid cold gas microthruster system for spacecraft
- 2001
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Ingår i: Digest of Papers for the 11th Int Conf on Solid-State Sensors and Actuators - Transducers '01 and Eurosensors XV, Munich, Germany, June 10-14. ; , s. 886-889
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Konferensbidrag (refereegranskat)
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- Köhler, Johan, et al.
(författare)
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A Hybrid Cold Gas Microthruster System for Spacecraft
- 2002
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Ingår i: Sensors and Actuators A-Physical. - 0924-4247 .- 1873-3069. ; 97-98, s. 587-98
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Tidskriftsartikel (refereegranskat)abstract
- A hybrid cold gas microthruster system suitable for low Δv applications on spacecraft have been developed. Microelectromechanical system (MEMS) components together with fine-mechanics form the microthruster units, intergrating four independent thrusters. These are designed to deliver maximum thrusts in the range of 0.1–10 mN.The system includes three different micromachined subsystems: a nozzle unit comprising four nozzles generating supersonic gas velocity, i.e. 455 m/s, four independent piezoelectric proportional valves with leak rates at 10−6 scc/s He, and two particle filters. The performances of all these MEMS subsystems have been evaluated.The total system performance has been estimated in two parameters, the system-specific impulse and the mass ratio of the propulsion system to the spacecraft mass. These figures provide input for spacecraft design and manufacture.
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