Showing papers on "Volumetric flow rate published in 1997"

High rate and selective etching of GaN, AlGaN, and AlN using an inductively coupled plasma

Abstract: The etching behavior of gallium nitride (GaN), aluminum gallium nitride (AlxGa1−xN), and aluminum nitride (AlN) has been systematically examined in an inductively coupled plasma (ICP) using Cl2 and Ar as the reagents Etch rates were strongly influenced by ICP power and dc bias, while relatively insensitive to pressure, flow rate, and gas composition Maximum etch rates of 9800 A/min for GaN, 9060 A/min for Al028Ga072N, and 7490 A/min for AlN were attained The etch profiles were highly anisotropic over the range of conditions studied The dc bias had to exceed certain voltages before significant etch rates were obtained These values were −50 V for AlN As such, increasing selectivity for GaN over Al028Ga072N and AlN was achieved at dc biases below −40 V At −20 V, the GaN etch rates were 38 times greater than AlN and a factor of 10 greater than Al028Ga072N These results demonstrate the importance of ion bombardment in the etching of these materials

Stratified scavenging two-cycle engine

Abstract: A stratified scavenging two-cycle engine, in which control of an air flow rate provides a favorable accelerating performance and can prevent deterioration of exhaust gas. The stratified scavenging two-cycle engine comprises a scavenging flow passage (3) for connection between a cylinder chamber (4a) and a crank chamber (1a), an air flow passage (2) connected to the scavenging flow passage (3), air flow rate control means (12) for controlling a flow rate of air fed to the scavenging flow passage (3) from the air flow passage (2), and mixture flow rate control means (11) for controlling a flow rate of mixture sucked into the crank chamber (1a) from a mixture flow passage (10). The air flow rate control means (12) throttles an air flow rate at the time of acceleration. Alternatively, the air flow rate control means (12) is opened later than the mixture flow rate control means (11) at the time of acceleration.

Electrokinetic Effects on Pressure-Driven Liquid Flows in Rectangular Microchannels

Abstract: The effects of the electrical double layer near the solid-liquid interface and the induced electrokinetic field on the pressure-driven liquid flow through a rectangular microchannel are analyzed in this work. A nonlinear, two-dimensional Poisson-Boltzmann equation governing the electrical double layer field in the cross section of rectangular channels is numerically solved with the use of a finite-difference scheme. A body force caused by the electrical double field and the flow-induced electrokinetic field is considered in the equation of motion. An exact solution to this equation of motion in rectangular microchannels is obtained by employing the Green function formulation. The effects of the ionic concentration of the liquid, the zeta potential of the solid surface, and the size and the shape of microchannels on the fluid velocity distribution, streaming potential, volumetric flow rate, friction coefficient, and apparent viscosity are discussed. The results clearly show that for a liquid solution of low ionic concentration and a solid surface of high zeta potential the liquid flow in rectangular microchannels is significantly influenced by the presence of the electrical double layer field and hence deviates from the flow characteristics described by classical fluid mechanics. Copyright 1997 Academic Press. Copyright 1997Academic Press

Three-dimensional flow and reaction in porous media: Implications for the Earth's mantle and sedimentary basins

Abstract: We present a theoretical and numerical study of the reorganization of a porous matrix due to fluid flow coupled with dissolution or precipitation processes. We find that under certain conditions, flow of corrosive fluids results in unstable growth of the permeability and increasing disequilibrium in fluid chemistry with time. High-permeability channels may form parallel to the direction of flow. In time, these channels cause the distribution of porosity to become increasingly correlated and anisotropic and cause flow rates to be increasingly variable. Flow coupled with crystallization has the opposite effect: With time, permeability reduction occurs at a decreasing rate. Mineral composition in the fluid approaches chemical equilibrium. Precipitation destroys existing preferred paths for flow and acts to homogenize and disperse the flow. Connectivity of the porous media is reduced. Implications of these results for two geological systems are discussed: (1) Modes of melt extraction from the Earth's mantle, where the expected different modes of flow and reaction may help explain different geochemical and geological observations at hot spots and mid-ocean ridges, and (2) Precipitation and formation of abnormal pressure zones in sedimentary basins.

Thermal mass flowmeter and mass flow controller, flowmetering system and method

Abstract: A flowmeter (100) or mass flow controller (101) used in a manufacturing process with toxic and reactive process fluids. A fluid flow sensor (114) sensesfluid flow. A set point is established based upon predetermined temperature and pressure conditions at which the fluid will be utilized in the process. A valve drive (124) operates a fluid flow valve (126) to the resulting fluid flow rate, this being based upon the sensed flow rate and the set point. A control unit (122) controls the valve drive. The control unit accesses a calibration data set to determine the amount of fluid to be delivered by the fluid flow valve based uponthe sensed flow rate and the set point. This calibration data set is created for the controller over its operational range using a calibration fluid having similar thermodynamic transport properties to a process fluid. The instrument is calibrated using the calibration fluid and the data set is produced by converting the calibration data using process fluid data stored in a data base (200). Accessing the data set stored in the instrument together with routing signals over a communication network (300) permits the instrument to precisely control process fluids without having to introduce external correction factors or other adjustments to the process.

Microchannels for applications in liquid dosing and flow-rate measurement

Abstract: To investigate the performance of microengineered fluid channels in liquid dosing applications, flow-rate measurements have been performed with various channel geometries in a range from 0.01 to 1000 μl min -1 . An optical flow-measurement technique has been developed to enhance the measurement range into the desired low flow range (10 -3 to 1 μl min -1 ), and is compared to a standard gravimetric method, which is preferably used for flow rates above 1 μl min -1 . In addition, influences of the temperture-dependent viscosity and effects arising from fluidmechanical characteristics are studied. These influences are also calculated from laminar flow theory and semi-emprical models to obtain a theoretical model. It is found that the theoretical model is able to describe the measurement results well in the whole flow range. The model is implemented on a PC-based system, which measures the pressure drop across the microchannel and the fluid temperature and calculates the flow. In a temperature range from 20 to 50°C excellent agreement is found.

Mathematical Modeling of Proton‐Exchange‐Membrane Fuel‐Cell Stacks

Abstract: A mathematical framework for the design of proton exchange membrane fuel-cell stacks has been established Sensitivity analysis on the steady-state model of a single fuel cell identified the inlet gas flow rates, the operating pressure, and the temperatures as the important operating parameters A performance model of a flow field is developed to describe the flow of the reactant gases across a single cell The reactant flow in the stack manifold is modeled to provide an engineering estimate of the variations in gas flow to the individual fuel cells in the stack The single-cell model is integrated with the performance model of the flow field and the stack-gas manifold to predict the operational characteristics of the fuel-cell stack

Semiconductor device and method for producing the same

Abstract: For example, in a plasma processing system, C 4 F 8 gas and C 2 H 4 gas are introduced as film-forming gases at flow rates of 60 sccm and 30 sccm, respectively, under the conditions of a pressure of 0.2 Pa, a microwave power of 2.7 kW, a radiofrequency power of 1.5 kW, and a wafer temperature of 350° C. At the same time, a plasma gas is also introduced at a flow rate of 150 sccm to form CF film 13 having an F content of, for example, 22% on silicon substrate 11. This CF film 13 has a relative dielectric constant of 2.4.

Silicon and germanium nanoparticle formation in an inductively coupled plasma reactor

Abstract: We have studied the formation of Si nanoparticles in a SiH4–Ar plasma discharge generated in a helical resonator type inductively coupled plasma reactor It is observed that Si particles vary in sizes from 5 to 15 nm under different conditions The particles were mostly spherical and made up of a crystalline core with a 1–2 nm thick amorphous shell The size distribution was narrow for particles formed at a pressure of 200 mTorr, plasma power of 400 W and silane flow rate of 20 sccm (+980 sccm Ar) The effect of a dc bias applied to the particle collecting grids has also been studied It is found that a negative bias (−25 to −100 V) applied to the grids used for particle collection results in a large increase in the number of Si nanoparticles collected, while a positive bias does not change the collection efficiency considerably, suggesting that the particles are positively charged Under very low flow rates and under high plasma powers, the Si particle density decreases considerably and a film like depos

Device for treating substrates in a fluid container

Abstract: In a device for treating substrates (5) in a fluid container (1), a particularly uniform, laminar flow pattern throughout the container is obtained even when a fluid is rapidly fed in at a high flow rate by means of a nozzle system with several nozzles (7) for introducing a fluid.

Instrument for measuring mass flow rate of powder, and electrostatic powder coating apparatus utilizing the same

Abstract: A miniaturized, inexpensive instrument for measuring the mass flow rate of powder, which is capable of directly outputting the mass flow rate of powder and whose characteristics are not influenced by the kind and physical properties of the powder. The instrument can be easily manufactured, installed, operated, and maintained, and the color can be easily changed. An apparatus for dispensing powder, which is constructed based on this mass flow rate measuring instrument and an electrostatic powder coating system utilizing this supply apparatus and having a high performance and a high effective operation factor are also provided. A gas to be measured, the flow rate of which is regulated, is turned into a thin-layer high-speed gas stream by a dispersion means, powder is cross-dispersed and introduced into a measuring conduit, the differential pressure occurring is measured, and a supply means is subjected to feedback control so that the output of the differential pressure agrees with a set level.

Control device for internal combustion engine

Abstract: PROBLEM TO BE SOLVED: To make it possible to be equipped with a new means instead of a bimetal gurd mechanism inexpensively, as a measure of an idle control system at the time when a water temperature sensor fails SOLUTION: The opening characteristics of a ISCV (idle control valve) are as follows: the opening is increased as the cooling water temperature THW is decreased, and the bypass air flow rate supplied to an engine is increased When a water temperature sensor fails, the duty value DOP for driving the ISCV is set to 50% to half-open the ISCV, and the bypass air flow rate supplied to the engine is switched to a neutral flow rate In this case, the neutral flow rate is the flow rate (duty value) which is above a lower limit guard, and below an upper limit guard in the full temperature range, and when the flow rate is within the range of these limits, the flow rate can be out of 50% Thus, by switching the bypass air flow rate to the neutral flow rate when the water temperature sensor fails, the worst states such as overrun, engine stop can be avoided, and the startability at low temperatures and the operability after warming can be ensured

Highly efficient supersonic chemical oxygen — iodine laser with a chlorine flow rate of 10 mmol s-1

Abstract: An experimental parametric investigation was made of a compact supersonic chemical oxygen — iodine laser. The output power of the laser was increased by displacing the point where iodine vapour was added to singlet oxygen from the subsonic to the transonic region of gas flow and by cooling of nitrogen. The output power was 200 W for a Mach number 1.5 in the cavity when the chlorine flow rate was 10 mmol s-1. An increase of the flow rates of all the gases and of the pressure in the singlet-oxygen generator by a factor of 1.6 resulted, when the other conditions were kept constant, in a proportional increase in the laser output power. An estimate of the chemical efficiency was in good agreement with the experimental value of 22%.

Experiments on electrostatic dispersion of air in water

Abstract: In many chemical and environmental applications, the use of bubble column reactors is common and often essential in such processes as absorption, coal liquefaction, catalytic slurry reactions, and bioreactions. The objective of this work is to investigate bubble generation of air in water through electrified metal capillaries. Many important factors that affect the formation of bubbles, including capillary size, capillary tip configuration, electrode distance, and flow rate, are studied. It is found that the bubble size decreases with increasing applied voltage and decreasing airflow rate. A dimensional analysis of the system parameters is also pursued. The dimensionless numbers are correlated into an empirical model that can be used for the prediction of the bubble size as a function of the applied voltage and airflow rate. It is found that the bubble size decreases with decreasing Reynolds number and increasing Weber number. Three different modes of bubble formation are observed: a spraying mode obtained at low airflow rate and high applied voltage, a dripping mode observed at high flow rate and low applied voltage, and a mixed spraying-dripping mode.

Growth mechanism of 3c-sic(111) films on si using tetramethylsilane by rapid thermal chemical vapor deposition

Abstract: We have used a rapid thermal chemical vapor deposition technique to grow epitaxial SiC thin films on Si wafers by pyrolyzing tetramethylsilane (TMS). The films were observed to grow along the (111) direction of 3C–SiC at temperatures above 1000 °C. The quality of the films was significantly influenced by the TMS flow rate in the gas mixture, the growth temperature, and the gas pressure in the reactor. Single-crystal SiC films were grown at TMS flow rates below 1.0 sccm with a H2 carrier gas flow rate of 100 sccm. The gas pressure in the reactor has a great influence on the crystallinity, morphology, and thickness of the SiC film grown. Gas phase analyses indicated that TMS dissociates into hydrogen, silicon atoms, and hydrocarbons such as CH4, C2H2, and C2H4 at the growth temperature. The chemical composition of the grown films was analyzed. The growth mechanism of the SiC film on the Si substrate without the carbonization process is discussed based on the experimental results.

Three‐Dimensional Experimental Testing of a Two‐Phase Flow‐Modeling Approach for Air Sparging

Abstract: Air sparging has been used for several years as an in situ technique for removing volatile compounds from contaminated ground water, but few studies have been completed to quantify the extent of remediation. To gain knowledge of the air flow and water behavior around air injection wells, laboratory tests and model simulations were completed at three injection flow rates (62, 187, and 283 lpm) in a cylindrical reactor (diameter - 1.2 m, depth = 0.65 m). Measurements of the air flux distribution were made across the surface of the reactor at 24 monitoring locations, six radial positions equally spaced along two orthogonal transects. Simulations using a multiphase flow model called T2VOC were completed for a homogeneous, axisymmetric configuration. Input parameters were independently measured soil properties. In all the experiments, about 75 percent of the flow injected exited the water table within 30 cm of the sparge well. Predictions with T2VOC showed the same. The averages of four flux measurements at a particular distance from the sparge well compare satisfactorily with T2VOC predictions. Measured flux values at a given radius varied by more than a factor of two, but the averages were consistent between experiments and agreed well with T2VOC simulations. The T2VOC prediction of the radial extent of sparging coincided with the distance out to which air flow from the sparge well could not be detected in the reactor. The sparging pattern was relatively unaffected by the air injection rate over the range of conditions studied. Changes in the injection rate resulted in nearly proportional changes in flux rates.