Showing papers on "Chamber pressure published in 2011"

Experimental research on the rotating detonation in gaseous fuels–oxygen mixtures

Abstract: An experimental study on rotating detonation is presented in this paper. The study was focused on the possibility of using rotating detonation in a rocket engine. The research was divided into two parts: the first part was devoted to obtaining the initiation of rotating detonation in fuel–oxygen mixture; the second was aimed at determination of the range of propagation stability as a function of chamber pressure, composition, and geometry. Additionally, thrust and specific impulse were determined in the latter stage. In the paper, only rich mixture is described, because using such a composition in rocket combustion chambers maximizes the specific impulse and thrust. In the experiments, two kinds of geometry were examined: cylindrical and cylindrical-conic, the latter can be simulated by a simple aerospike nozzle. Methane, ethane, and propane were used as fuel. The pressure–time courses in the manifolds and in the chamber are presented. The thrust–time profile and detonation velocity calculated from measured pressure peaks are shown. To confirm the performance of a rocket engine with rotating detonation as a high energy gas generator, a model of a simple engine was designed, built, and tested. In the tests, the model of the engine was connected to the dump tank. This solution enables different environmental conditions from a range of flight from 16 km altitude to sea level to be simulated. The obtained specific impulse for pressure in the chamber of max. 1.2 bar and a small nozzle expansion ratio of about 3.5 was close to 1,500 m/s.

Physics‐based models of ground deformation and extrusion rate at effusively erupting volcanoes

Abstract: [1] We present a model of effusive silicic volcanic eruptions which relates magma chamber and conduit physics to time-dependent data sets, including ground deformation and extrusion rate. The model involves a deflating chamber which supplies Newtonian magma through a cylindrical conduit. Solidification is approximated as occurring at fixed depth, producing a solid plug that slips along its margins with rate-dependent friction. Changes in tractions acting on the chamber and conduit walls are used to compute surface deformations. Given appropriate material properties and initial conditions, the model predicts the full evolution of an eruption, allowing us to examine the dependence of observables on initial chamber volume, overpressure, and volatile content. Employing multiple data sets in combination with a physics-based model allows for better constraints on these parameters than is possible using kinematic idealizations. Modeling posteruptive deformation provides an improved constraint on the rate of influx into the magma chamber from deeper sources. We compare numerical results to analytical approximations and to data from the 2004–2008 eruption of Mount St. Helens. For nominal parameters the balance between magma chamber pressure and frictional resistance of the solid plug controls the evolution of the eruption, with little contribution from the fluid magma below the idealized crystallization depth. While rate-dependent plug friction influences the time-dependent evolution of the eruption, it has no control on the final chamber pressure or extruded volume.

Heat Transfer in Freeze-Drying Apparatus

Abstract: Freeze-drying is a process used to remove water (or another solvent) from a frozen product, thus increasing its shelf-life. It is extensively used in pharmaceuticals manufacturing, to recover the active pharmaceutical ingredient (and the excipients) from an aqueous solution, as well as in some food processes, because of the low operating temperatures that allow preserving product quality. Moreover, the freeze-dried product has a high surface area and can be easily re-hydrated. In this chapter we focus on pharmaceuticals manufacturing, where the solution containing the product is generally processed in vials, placed over the shelves in a drying chamber. However, it is worth stating that, in industrial practice, other loading configurations can be used to carry out the process, thus this study will be extended also to the case where vials are loaded on trays, or the solution is directly poured in trays. The process consists of three consecutive steps, namely: 1. Freezing: product temperature is lowered below the freezing point and, thus, most of the solvent freezes, forming ice crystals. Part of the solvent can remain bounded to the product, and must be desorbed. Also the product often forms an amorphous glass which can retain a high amount of water. 2. Primary drying: in this step the pressure in the drying chamber is lowered, thus causing ice sublimation. This phase is usually carried out at low temperature (ranging, in most cases, from -40°C to -10°C) and, as sublimation requires energy, heat is transferred to the product through the shelf, by acting on the temperature of the fluid flowing in the coil inserted in the shelf. 3. Secondary drying: when the sublimation of the ice has been completed, shelf temperature is raised (e.g. to 20-40°C) and chamber pressure is further decreased to allow the desorption of the water bounded to the product, thus getting the target moisture in the product. The freeze-dryer comprises the drying chamber and a condenser where the water vapour is sublimated on some cold surfaces in order to decrease the volumetric flow-rate arriving to the vacuum pump. The pressure in the chamber can be modified either by acting on a valve placed on pump discharge, or using the so called “controlled leakage”, i.e. manipulating the flow rate of nitrogen (or another gas) introduced in the chamber. The drying chamber can be isolated from the condenser by means of a valve that is usually placed in the duct connecting the chamber to the condenser (Mellor, 1978; Jennings, 1999; Oetjen & Haseley, 2004; Franks, 2007).

Supersonic Nozzle Flow Simulations for Particle Coating Applications: Effects of Shockwaves, Nozzle Geometry, Ambient Pressure, and Substrate Location upon Flow Characteristics

Abstract: Characteristics of supersonic flow are examined with specific regard to nano-particle thin-film coating. Effects of shockwaves, nozzle geometry, chamber pressure, and substrate location were studied computationally. Shockwaves are minimized to reduce fluctuations in flow properties at the discontinuities across diamond shock structures. Nozzle geometry was adjusted to ensure optimal expansion (i.e., Pexit = Pambient), where shock formation was significantly reduced and flow kinetic energy maximized. When the ambient pressure was reduced from 1 to 0.01316 bar, the nozzle’s diverging angle must be increased to yield the optimum condition of minimized adversed effects. Beyond some critical distance, substrate location did not seem to be a sensitive parameter on flow characteristics when Pamb = 0.01316 bar; however, overly close proximity to the nozzle exit caused flow disturbances inside the nozzle, thereby adversely affecting coating gas flow.

Chugging Instability of H2O2 Monopropellant Thrusters with Reactor Aspect Ratio and Pressures

Abstract: Among the three types of instabilities, the low-frequency instability (chugging instability) was experimentally investigated with respect to the chamber pressure and aspect ratio (L=D) of catalytic reactors in a monopropellant thruster. ThreeH2O2 thrusterswere used, and two parameters were found to be the dominant factors that generated a chugging instability of the order of several tens of hertz. Ahigh chamber pressure and lowL=D values (lowpressure drop across the catalyst bed) were preferable for reducing pressure oscillation inside the reaction chamber. In addition, it was found that these two parameters were not independent but coupled; therefore, the point where chugging instability occurred varied slightly depending on the interaction between these parameters.

Theoretical and Experimental Identification of Acoustic Spinning Mode in a Cylindrical Combustor

Abstract: The analytical solution for the eigenmodes of a cylindrical combustor allows for several realizations of the first tangential mode. The limiting cases of standing and spinning first tangential modes are well known. The general solution for a first tangential mode, however, allows for a large variety of realizations. In this study the analytical solution of the acoustic problem and a numerical time-resolved simulation of the acoustic pressure field are compared with experimental data from hot-fire tests. The experimentally observed pressure data are in excellent agreement with the simulation for all possible theoretical solutions. The approach enables detailed insight into the dynamics of the pressure field and thus constitutes a tool for the characterization of acoustic pressure waves in a cylindrical combustor even when the amplitude of the investigated eigenmode is small as compared with the mean pressure fluctuation.

Multilayer membrane actuators

Abstract: An IOP control device for implantation in an eye of a patient is disclosed. The device includes a housing and a multilayer membrane. The housing is sized for implantation into the eye and includes an entrance port and an exit port. The membrane is anchored within the housing to form a flow control chamber on a first side and a fluid flow passageway on a second opposing side of the membrane. The chamber is arranged to contain a gas creating a chamber pressure, and the membrane is configured to affect flow through the passageway from the entrance port to the exit port by deflecting in response to changes in the chamber pressure. The membrane comprises a first layer having a higher permeability and a higher flexibility than the second layer, which is disposed adjacent the first layer and restricts the diffusion of gas in the chamber through the membrane.

Effect of chamber pressure on spreading and splashing of liquid drops upon impact on a dry smooth stationary surface

Abstract: Liquid drop impacts on a smooth surface were studied at elevated chamber pressures to characterize the effect of gas pressure on drop spreading and splashing. Five common liquids were tested at impact speeds between 1.0 and 3.5 m/s and pressure up to 12 bars. Based on experiments at atmospheric pressure, a modification to the “free spreading” model (Scheller and Bousfield in AIChE Paper 41(6):1357–1367, 1995) has been proposed that improves the prediction accuracy of maximum spread factors from an error of 15–5%. At high chamber pressures, drop spreading and maximum spread factor were found to be independent of pressure. The splash ratio (Xu et al. in Phys Rev Lett 94:184505, 2005) showed a non-constant behavior, and a power-law model was demonstrated to predict the increase in splash ratio with decreasing impact speed in the low impact speed regime. Also, drop shape was found to affect splash promotion or suppression for an asymmetry greater than 7–8% of the equivalent drop diameter. The observations of the current work could be especially useful for the study of formation of deposits and wall combustion in engine cylinders.

Numerical and Experimental Investigation on Vortex Injection in Hybrid Rocket Motors

Abstract: A study on vortex injection in hybrid rocket motors with nitrous oxide as the oxidizer and paraffin as the fuel has been performed. The investigation followed two paths: first of all, the flow field was simulated with a CFD code, and then burn tests were performed on a lab-scale rocket. The CFD analysis had the dual purpose to help the design of the lab motor and to understand the physics underlying the vortex flow coupled with the combustion process. Numerical analysis was focused on the comparison with axial injection. Vortex injection produces a more diffuse flame in the combustion chamber and improves the mixing process of the reactants, both aspects concurring to increase the efficiency of the motor. A helical streamline develops downstream the injection region, and the pitch is highly influenced by combustion, that tends to straighten the flow due to the acceleration imposed by the temperature rise to the axial velocity component. The tangential velocity, on the contrary, is far less influenced by this effect. Experimental tests with the same chamber geometry have been performed with both pressurized and self-pressurized oxidizer. Measured performances showed an increase in regression rate up to 51% and a combustion efficiency that rises from values lower than 80% in the axial injection configuration up to more than 90% with vortex. Moreover, a reduction of the instabilities in the chamber pressure has been measured. Issues requiring further investigation concern the motor exhausts: both experimental and numerical analyses showed that there is a residual tangential velocity component in the plume; this, coupled with a noise suppressor system downstream the nozzle in the test apparatus, showed severe instabilities in the vortex configuration thrust measurements, not reported in chamber pressure burn data and not affecting axial injection.

Compact Permanent Magnet Microwave‐Driven Neutron Generator

Abstract: Permanent magnet microwave-driven neutron generators have been developed at Lawrence Berkeley National Laboratory. The 2.45 GHz microwave signal is directly coupled into the plasma chamber via a microwave window. Plasma is confined in an axial magnetic field produced by the permanent magnets surrounding the plasma chamber. The source chamber is made of aluminum with a diameter of 4 cm and length of 5 cm. A stack of five alumina discs, which are 3 cm in diameter and total length of 3 cm, works as microwave window. Three permanent ring magnets are used to generate the axial magnetic field required for the microwave ion source. Both hydrogen and deuterium plasma have been successfully ignited. With 330W of microwave power, source chamber pressure of 5 mTorr, and an extraction aperture of 2 mm in diameter, the deuterium ion beam measured on the target was approximately 2.5 mA. Over 90% of the ions are atomic. With the ion source at ground potential and titanium target at -40 kV, the analysis of the activated gold foil and calibrated neutron dose monitor both indicated that roughly 10{sup 7} n/s of D-D neutrons have been produced. The D-D neutron yield can be easily scaled up tomore » 10{sup 8} n/s when the titanium target is biased at -100 kV.« less

Theoretical Investigation on the Dynamics of a Gas-Liquid Coaxial Swirl Injector

Abstract: the injector into two parts: the recessed chamber and the section before the recessed chamber. The gaseous injector flow before the recessed chamber is considered to be steady; only the response of the mass flow rate at the exit of coaxial injector to the pressure fluctuation at the liquid injector inlet has been investigated. The dynamic characteristics of the coaxial swirl injector can now be considered as two processes: the dynamics of the liquid swirl injector and the dynamics of the recessed chamber. The transfer function of the whole injector is obtained by combining the transfer functions of these two processes. The influence of the injector configuration and working condition on the injector dynamic characteristics was also studied. A smaller mixing ratio, larger mass flow rate, higher ambient pressure, smaller ratio of recess length to diameter, and larger geometry parameter would decrease theamplituderesponse ofthemass flowratepulsation, buttheseparametershavelittleeffectonthephasefrequency of the coaxial swirl injector.

Biodegradable poly(glycolic acid) nanofiber prepared by CO2 laser supersonic drawing

Abstract: Biodegradable Poly(glycolic acid) (PGA) nanofibers were prepared by irradiating a PGA fiber with radiation from a carbon dioxide (CO2) laser while drawing it at supersonic velocities and was collected as a nonwoven. A supersonic jet was generated by blowing air into a vacuum chamber through the fiber injection orifice. The flow velocity from the orifice was estimated by computer simulation; the fastest flow velocity was calculated to be 401 m s−1 at a chamber pressure of 6 kPa. A nanofiber obtained using a laser power of 10 W and a chamber pressure of 6 kPa had an average diameter of 359 nm and a draw ratio of about 77,600. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

PULSION® HP: Tunable, High Productivity Plasma Doping

Abstract: Plasma doping has been explored for many implant applications for over two decades and is now being used in semiconductor manufacturing for two applications: DRAM polysilicon counter‐doping and contact doping. The PULSION HP is a new plasma doping tool developed by Ion Beam Services for high‐volume production that enables customer control of the dominant mechanism—deposition, implant, or etch. The key features of this tool are a proprietary, remote RF plasma source that enables a high density plasma with low chamber pressure, resulting in a wide process space, and special chamber and wafer electrode designs that optimize doping uniformity.

Intense Tangential Pressure Oscillations Inside a Cylindrical Chamber

Abstract: Intense tangential pressure oscillations due to oscillatory combustion are generated experimentally inside a cylindrical chamber and are analyzed to understand their characteristic features. To generate the tangential mode, a coaxial injector is installed offcenter on the closed side of the chamber. Hydrogen and nitrogen-diluted oxygen are used as working gases under atmospheric conditions. The features of the side-wall pressure in the first tangential mode (1T mode) at high amplitude, whose amplitude is over 30% of the chamber pressure, differ from those of the side-wall pressure in the 1Tmode at low amplitude in the followingmanner: 1) The positive half-wave of the pressure oscillation has twin sharp peaks. 2) The amplitude of the positive half-wave (zero to positive peak) of the pressure oscillations is larger than that of the negative half-wave (negative peak to zero). The acoustical features of the signals are reproduced and investigated by conducting an analysis and anumerical simulation under similar configurations. It is found that the characteristic feature of the intense signal is originated in the nonlinearity due to the large amplitude of the pressure oscillation.

Fuel-Rich Combustion Characteristics of Biswirl Coaxial Injectors

Abstract: An experimental study was performed to investigate the combustion characteristics of liquid–liquid swirl coaxial injectors in fuel-rich conditions. Liquid oxygen and kerosene (Jet A-1) were burned in a range of mixture ratios (0.29–0.41) and chamber pressures (46–65 bar) in a gas generator for a liquid rocket engine. An injector head was connected to a water-cooled chamber and a short nozzle with or without an extension pipe between the chamber and the nozzle. The extension pipe acoustically simulated a turbine inlet manifold. The injector head had 37 identical swirl coaxial injectors. It is found that the characteristic velocity and combustion gas temperature are seldom influencedby the extension pipe, but are only functions of themixture ratio. The dynamic pressure data show that the combustion instability in the fuel-rich gas generator equipped with biswirl coaxial injectors can be significantly affected by themixture ratio and also by the extension pipe, which influences the resonant frequency in the chamber.

Study of the effect of the deposition parameters on the structural, electric and optical characteristics of polymorphous silicon films prepared by low frequency PECVD

Abstract: In this work we present our results on the deposition and characterization of polymorphous silicon (pm-Si:H) films prepared by low frequency plasma enhanced chemical vapor deposition (LF-PECVD). We have studied the effect of the plasma deposition parameters (as the chamber pressure and gas flow rates of SiH4 and H2) on the structural, electric, and optical characteristics of the films. The temperature dependence of conductivity (σ(T)), activation energy (Ea), optical band gap (Eg) and deposition rate (Vd) were extracted for pm-Si:H films deposited at different pressure values and different gas flow rates. We observed that the chamber pressure is an important parameter that has a significant effect on the electric characteristics, and as well on the morphology of the pm-Si:H films (deduced from atomic force microscopy). It was found an optimal pressure range, in order to produce pm-Si:H films with high Ea and room temperature conductivity, σRT, which are key parameters for thermal detection applications.

Rotary-type filling machine and method for calculating filling quantity for rotary-type filling machine

Abstract: A rotary-type filling machine includes a rotary body, a liquid distribution chamber, a plurality of filling flow path configuration units, each of which has a fluid path constituted by a liquid path connected to the liquid distribution chamber and a liquid valve and configured to individually introduce a liquid into a container, a filling control device, a liquid supply unit, a pressure difference information detection unit configured to detect pressure difference information between a liquid distribution chamber pressure, which is a pressure of the liquid in the liquid distribution chamber, and a filling atmospheric pressure detected as a pressure of a flow release unit in a filling flow path configuration unit at an arbitrary radial direction position of the rotary body, and a rotation information detection unit configured to detect rotation information of the rotary body.

Boundary-Layer Suction System Design for Laminar-Flying-Wing Aircraft

Abstract: DOI: 10.2514/1.C031283 The present study aims to provide insight into the parameters affecting practical laminar-flow-control suction power requirements for a commercial laminar-flying-wing transport aircraft. It is shown that there is a minimum power requirement independent of the suction system design, associated with the stagnation pressure loss in the boundary layer. This requirement increases with aerofoil section thickness, but depends only weakly on Mach number and (for a thick, lightly loaded laminar flying wing) lift coefficient. Deviation from the optimal suction distribution, due to a practical chamber-based architecture, is found to have very little effect on the overall suction coefficient;hence,toagoodapproximation,thepowerpenaltyisgivenbytheproductoftheoptimalsuction flowrate coefficient and the average skin pressure drop. In the spanwise direction, through suitable choice of chamber depth, the pressure drop due to frictional and inertial effects may be rendered negligible. Finally, if there are fewer pumps than chambers, the average pressure drop from the aerofoil surface to the pump collector ducts, rather than to the chambers,determinesthepowerpenalty.Fortherepresentativelaminar-flying-wingaircraftparametersconsidered here, the minimum power associated with boundary-layer losses alone contributes some 80–90% of the total power requirement.

Effects of pre-bulging on 2024 aluminum alloy complex-shaped components

Abstract: To improve the poor plasticity of 2024 aluminum alloy sheet, which causes wrinkle and fracture in conventional deep drawing of complexshaped components, hydromechanical deep drawing (HDD) with pre-bulging was investigated. The loading paths of chamber pressure and pre-bulging pressure were designed and optimized by numerical simulations and experiments, and effects of loading paths were obtained and analyzed for thickness, stress and defects. A reasonable loading path was determined. Thickness is more uniform when pre-bulging pressure is 2 MPa and chamber pressure is 15 MPa. The suspending area of a blank wrinkles easily between the punch and the die when pre-bulging pressure is smaller than 1.5 MPa; fracture occurs for the suspending area of blank between the punch and the die when pre-bulging pressure is larger than 8 MPa. The results show that a helpful friction can be generated, the stress state can be improved, and fracture and wrinkle can be avoided by a reasonable pre-bulging in the suspending area of the blank for a complex-shaped component. The uniformity of thickness and forming limit can be enhanced.

DBD Plasma Actuators for Flow Control in Air Vehicles and Jet Engines - Simulation of Flight Conditions in Test Chambers by Density Matching

Abstract: Dielectric Barrier Discharge (DBD) Plasma actuators for active flow control in aircraft and jet engines need to be tested in the laboratory to characterize their performance at flight operating conditions. DBD plasma actuators generate a wall-jet electronically by creating weakly ionized plasma, therefore their performance is affected by gas discharge properties, which, in turn, depend on the pressure and temperature at the actuator placement location. Characterization of actuators is initially performed in a laboratory chamber without external flow. The pressure and temperature at the actuator flight operation conditions need to be simultaneously set in the chamber. A simplified approach is desired. It is assumed that the plasma discharge depends only on the gas density, while other temperature effects are assumed to be negligible. Therefore, tests can be performed at room temperature with chamber pressure set to yield the same density as in operating flight conditions. The needed chamber pressures are shown for altitude flight of an air vehicle and for jet engines at sea-level takeoff and altitude cruise conditions. Atmospheric flight conditions are calculated from standard atmosphere with and without shock waves. The engine data was obtained from four generic engine models; 300-, 150-, and 50-passenger (PAX) aircraft engines, and a military jet-fighter engine. The static and total pressure, temperature, and density distributions along the engine were calculated for sea-level takeoff and for altitude cruise conditions. The corresponding chamber pressures needed to test the actuators were calculated. The results show that, to simulate engine component flows at in-flight conditions, plasma actuator should be tested over a wide range of pressures. For the four model engines the range is from 12.4 to 0.03 atm, depending on the placement of the actuator in the engine. For example, if a DBD plasma actuator is to be placed at the compressor exit of a 300 PAX engine, it has to be tested at 12.4 atm for takeoff, and 6 atm for cruise conditions. If it is to be placed at the low-pressure turbine, it has to be tested at 0.5 and 0.2 atm, respectively. These results have implications for the feasibility and design of DBD plasma actuators for jet engine flow control applications. In addition, the distributions of unit Reynolds number, Mach number, and velocity along the engine are provided. The engine models are non-proprietary and this information can be used for evaluation of other types of actuators and for other purposes.

Effect of Pressure and Oil Mist on Windage Power Loss of a Shrouded Spiral Bevel Gear

Abstract: In many aeroengines the accessory power offtake is achieved using a spiral bevel gear set running off one of the main shafts. The crown and bevel gears are housed in an internal gearbox and there is significant heat generation within this chamber, some of which is attributed to windage power loss (WPL) generated by the gear. Over the past few years the University of Nottingham Technology Centre (UTC) in Gas Turbine Transmissions has been researching spiral bevel gear windage power loss both computationally and experimentally using a purpose-built test rig at the UTC. In this study the test rig has been adapted such that chamber pressures up to 8 bar can be generated. Test data has been obtained that shows the effect on WPL of chamber pressure, advancing understanding of the relationship between data obtained at ambient and pressurised conditions. Three configurations have been studied: unshrouded gear, gear with 360° shroud and shrouded, crown and pinion meshing pair. Further, the effect of oil mist within the chamber on WPL has been studied. An oil mist generation system was developed for introducing a fine mist into the chamber and results are presented for varying mist flowrates. A mist measurement system was developed to sample mist mass fraction within the chamber and the data obtained is used to calculate an effective (oil/gas mixture) chamber density. Increasing chamber pressure increases Reynolds number, moving the system behavior further along the Moment coefficient-Reynolds number correlation. The Cm -Re correlation is similar in form to that for a shrouded cone, showing transitional behavior around Re = 2×106 . Beyond transition Cm decreases with increasing Re. Introducing an oil spray has two effects: reduction in chamber temperature and increase in effective density of chamber fluid. Both effects can be accounted for by calculating Re and Cm based on mixture properties but it seems highly likely that the properties of the fluid under the shroud differ from those of the fluid in the external chamber.© 2011 ASME

The effects of low temperature and pressure on the fracture behaviors of organosilicate thin films

Abstract: A novel load–displacement sensing instrument has been designed and fabricated to characterize the fracture properties of brittle thin films at low temperature (approximately −30 °C) and pressure (1.6e-4 Pa) environments. In this study, the instrument was used to investigate the effects of harsh environments on the fracture behaviors of organosilicate glass (OSG) and silicon carbonitride (SiCN) thin films under four-point bend loading. Experimental results showed that the fracture strengths of film stacks are the highest when the environment contains a very low water molecule concentration. This condition can be achieved by purging the testing chamber with pure nitrogen or reducing the chamber pressure to less than 1 Pa. In contrast, cracks propagated readily along OSG/SiCN interfaces when experiments were performed in deionized water. The effects of low temperature (approximately −30 °C) and pressure on thin film fracture were also studied, and the results demonstrated that there is no observed degradation of the OSG fracture properties. X-ray photoelectron spectroscopy (XPS) technique was used to identify the chemical composition of the fracture surfaces.

Systems and methods for measuring, monitoring and controlling ozone concentration

Abstract: Systems and methods to determine ozone concentration in a gas mixture of ozone and oxygen, based on measurements of a total mass flow and a corresponding change in a chamber pressure accepting the mixture flow, can enable the measurements of ozone concentration at low pressure settings. The ozone concentration determination can be applied to a vacuum processing chamber, enabling precision semiconductor processing.

Closed-loop pressure control of an adaptive single chamber membrane lens with integrated actuation

Abstract: We introduce a closed-loop pressure control of a single chamber adaptive fluidic membrane lens with an integrated piezoelectric bending actuator. For this purpose a pressure sensor is integrated into the lens and allows for a measurement of the chamber pressure as a function of the refractive power. The linear relation between pressure and refractive power allows to eliminate the typical hysteresis effects of piezo actuators.

Analytical model of electrostatic actuators for micro gas pumps

Abstract: We analytically predict the performance of electrostatic actuators for diaphragm micro gas pumps by combining energy minimization and the analytical solution for membrane deformation under uniform pressure. The tangential strain of the membrane is considered in the calculation of membrane deflection. Models for both single- and double-cavity pumps are established to define the restriction of the upper cavity on the membrane during actuation. The shape lines of the membrane in a double-cavity structure are demonstrated under different voltages. The influence of dielectric thickness and cavity geometry on pumping consequence is also discussed. In accordance with other simulation results on diaphragm displacement and chamber pressure rise, an electrostatic diaphragm micro gas pump with a relatively thin dielectric layer and a cavity of comparatively small depth and radius suitably generates high pressure rise. Furthermore, a double-cavity structure enhances pressure rise for the restriction of the upper cavity on the membrane during deformation.

A finite element model for efficiency of a moored floating OWC device in regular waves

Abstract: Hydrodynamic characteristics of floating OWC can be quite difficult to predict especially when a strong coupling is present between the chamber pressure and the device movements. Mooring properties, and air pressure inside the chamber can also considerably influence the motion of the device and therefore the energy output. A newly developed 3D finite element model based on the linear wave theory has been applied to a cylindrical type OWC device. The study focused principally on the effects of the mooring restoring force and pressure pneumatic damping in the chamber total volume flux and energy conversion of the device. Results show that properly chosen parameters could effectively increase the efficiency band width of such devices. Copyright © 2011 by ASME.