Gas Injection System Research Articles

Tokamak Fusion Test Reactor gas injection control system design and operation

Magnetic fusion devices require fast‐responding, versatile, and accurate gas injection systems in order to initiate and modulate the plasma density. We describe the gas injection control system (GICS), which regulates the gas injected into the torus of Princeton’s Tokamak Fusion Test Reactor (TFTR). Synchronized with each TFTR discharge, a PDP 11/23 microcomputer provides real‐time control for one to six fast injection valves, each allocated to feedback or open loop operation. Up to four feedback sources, including torus pressure gauges and plasma density measurements, are checked once each cycle for 1000 cycles; the cycle duration can be set to any multiple of 2 ms up to 16 ms. Detection of various fault conditions can cause automatic shutdown or modification of GICS operation. Data is archived after each TFTR discharge, and subsequently used for particle fueling studies and analysis of system drifts. A steady state mode of operation is used for vacuum vessel discharge cleaning. The system also provides for valve calibration and torus pumping speed measurements.

Neutral pressure and gas flow instrumentation for TFTR

The design and operation of instrumentation included in the gas injection system of the Tokamak Fusion Test Reactor (TFTR) for torus pressure and gas flow measurements are described. Magnetically shielded ion gauges, located on the torus boundary, are used for fast (1 kHz) torus pressure measurements over the range 10−7–10−3 Torr. Gas injection assemblies comprising an array of piezoelectric gas injection valves are situated at three toroidal locations. The gas injection valves are programmed for various discharge conditions including feedback control from the torus pressure gauges and plasma density measurement. Gas flow through the injection valves is monitored by strain-gauge-type pressure transducers on each injection valve. The resulting gas flow measurements are used for gas fueling, particle balance, and recycling studies.

1-millimeter wave interferometer for the measurement of line integral electron density on TFTR

A two-pass interferometer at 285 GHz has been developed to measure the line-integrated electron density on the horizontal midplane of the toroidal fusion test reactor (TFTR). Presently, the interferometer employs a 2-mW solid-state source to supply the launch wave and a 2-mm klystron oscillator and, a harmonic mixer to provide a superheterodyne front end. The transmission system consists of 25 m of C-band rectangular waveguide, adjustable miter bends, and a spherical mirror in the vacuum vessel with a total round trip transmission loss of 21 dB. The interferometer signal to noise is ≳50 dB. Utilization of a feed forward tracking system provides long-term stable operation. The interferometer routinely provides real-time feedback control for the gas injection system and a permissive for neutral beam operation.

Fast gas injection system for plasma physics experiments

A system has been developed for fast, feedback controlled injection of hydrogen and various other gases into a vacuum system. Gas flow is through short (about 30-mm length), submillimeter diameter tubing at pressures in the fluid flow regime. The flow is controlled by a piezoelectric valve and measured by a miniature pressure sensor mounted in the body of the valve. Flow rates from a single valve of up to 500 Torr liter/s for hydrogen have been obtained. Response time of the flow is a rise time of 0.5 ms (with a 3-ms ringing decay time) and a fall time of 0.3 ms. The flow rate is basically a linear function of the measured pressure. A model has been developed to explain the observed functional dependence of flow rate on pressure, gas type, and tube radius.

Hydrodynamics of gas stirred melts: Part I. Gas/liquid coupling

A hydrodynamic model of submerged gas injection systems and their effects on liquid metal stirring is presented. It is argued that hydrodynamic conditions at the nozzle, tuyere, or plug are not critical to flow recirculation produced in large cylindrical vessels(i.e., furnaces or ladles). An analysis of a buoyancy driven plume generated through gas injection shows that gas voidages are usually quite low (less than 10 pct). By equating the energy supplied by rising bubbles to turbulent energy losses within the bath, it is shown that mean plume velocities can be predicted using the relationship,Up α (Q1/3L1/3)/R1/3 whereUp equals mean plume velocity,Q is gas flow rate (at mean height and temperature),L is depth of liquid, andR is radius of the vessel. Associated rates of liquid turnover as a function of vessel dimensions and gas flow rate can also be predicted and these are similarly presented.

3885. Fast hydrogen gas injection system for plasma physics experiments. (USA)

3885. Fast hydrogen gas injection system for plasma physics experiments. (USA)

Fast hydrogen gas injection system for plasma physics experiments

A system has been developed for fast injection of hydrogen gas into a vacuum system, which can produce feedback controlled flows in the range 0.1-10 Torr l/s. The unit uses a fast pressure transducer as a flow sensor. The flow will respond to an external programming voltage whose time variation is as short as several milliseconds.

Reduction of nitric oxide in automobile engine exhaust by ethane-air injection

Previous work has shown that hydrocarbon-oxygen mixtures can be effective reductants for NO in simulated combustion exhaust gases. Specifically, this work suggests that hydrocarbon-oxygen mixtures might prove to be effective NO reductants in the exhaust gases from automotive engines. To investigate this possibility, a 1970 Ford 302 V8 engine was equipped with a suitable exhaust gas injection system and exhaust manifold reactor which made it possible to investigate this reduction chemistry in the exhaust gas. The results of these engine tests, in which NO, CO, CO/sub 2/, O/sub 2/, and hydrocarbons and sometimes HCN were measured, are reported in this paper. They show that such hydrocarbon-air injection can indeed significantly reduce exhaust gas NO concentration under some engine operating conditions.

Abstract: Growth morphology and surface‐acoustic‐wave measurements of AlN films on sapphire

Aluminum nitride epitaxial films have been grown on R‐plane sapphire substrates and studied for its piezoelectric properties as applied to surface‐acoustic‐wave device applications. The films reported here are grown by a chemical vapor deposition process involving the reaction of trimethyl aluminum gas with ammonia in the presence of hydrogen at temperatures of approximately 1200 °C. Using a modified epireactor as the growth furnace with a gas injection system that directs gas flow onto the substrate, growth rates of 500 Å/min are achieved producing films over 10 μm in thickness which exhibit excellent mechanical and chemical stability.The R‐plane, (011̄2), of sapphire consists of alternate layers of Al and O with a repetitive sequence of O–Al–O–Al–O. In the two different layers of atoms, the Al atoms occur in a close‐packed configuration while the O atoms are aligned into columns along the [01̄11] direction. The hexagonal wurtzite structure of AlN has the (112̄0) plane consisting of coplanar atoms of Al and N in a close‐packed configuration but segregated into columns aligning with the [0001] direction. A good fit of these two planes is obtained when the columns of atoms are aligned with the sapphire [01̄11] and AlN [0001] directions colinear (i.e., with the AlN c axis pointing in the same direction as the projection of sapphire c axis upon the R plane), giving lattice mismatches of 2.7% along and 11.9% across the [01̄11] direction. A reversal of the AlN [0001] axis however, places the AlN atoms in the interstitial sites of sapphire indicating poor lattice matching.The as‐grown surface morphology of the AlN films, as examined under a scanning electron microscope, can be divided into two categories. Category I features very distinctive scale‐like facets that are all aligned in one direction while category II includes the scale‐like facets aligned but pointing in opposing directions along with some spurious nucleations. X‐ray analysis of the sapphire substrate shows the facets to be that of the AlN [0001] axis aligning with the [01̄11] direction of the R plane.Surface‐acoustic‐wave measurements of the AlN films are made by reflective impedance measurements from Al interdigital transducers fabricated upon polished surfaces. There is a definite correlation between the quality of the results and the category of the surface morphology. Results obtained from films of category I were consistently better than those obtained from films of category II leading to the confirmation of the theory that there is a preferred direction of growth of AlN [0001] axis upon the R plane for minimum stress with maximum lattice matching. Surface‐acoustic‐wave coupling constant K2 and propagation velocity Vs are measured out to an AlN thickness to transducer wavelength ratio t/λ of 0.75 with typical K2 values of 0.8% and Vs of 6.1 km/s.Preliminary results obtained from a study of the dependence of the K2 versus t/λ curve upon transducer wavelength indicate that the AlN–sapphire interfacial strain extends about 1 μm into the AlN film.

Land Disposal of Waste Gases: I. Flow Analysis of Gas Injection Systems

AbstractThe steady‐state flow of gases in soils is analyzed mathematically from the view of land disposal of waste gases. Gas injection systems considered include ditches, buried pipes, and wells. The systems are compared on the basis of two criteria (i) how effectively the power is used (power efficiency), and (ii) how uniformly is the gas distributed through soils (uniformity). Often the two criteria are in conflict, and systems giving a high power efficiency result in low uniformity. Gas injection by buried porous pipe appears advantageous over ditch or well systems.

Quadrupole mass filter: circular rods and peak shapes: P H Dawson and N R Whetten, J Vac Sci Technol, 7 (3), May/June 1970, 440–441

A gaseous ion source has been designed at Dongguk University accelerator mass spectrometer facility, Korea. Radiocarbon dating is conducted at this facility with a mini carbon dating system and a prototype ion source has been developed for a gas injection system for high-level 14C samples, which can decrease the precision of sample measurements for carbon dating. To improve the efficiency of carbon counting of gas samples, a gaseous ion source called a duoplasmatron has been installed in the prototype ion source test stand with low cost, easy maintenance, and direct gas discharge. It is necessary to verify the operation characteristics of the duoplasmatron of the ion source test stand with the beam characteristics to measure the beam current with various ion source parameters. The effects of the arc current, ion source magnet field, and extraction voltage on the beam current are presented in this paper.

Operational Problems with 8,000-psig Injection Compressors

High-speed compressors can be used successfully in high-pressure gas injection service. To achieve satisfactory results, however, closer than usual attention must be given to the gas properties at the high pressures and to the over-all design of the unit. pressures and to the over-all design of the unit. The Field Situation The Cheniere Cadeville Unit is located in Ouachita Parish, La., about 15 miles west of Monroe. The Parish, La., about 15 miles west of Monroe. The field was unitized in 1966 for the purpose of conducting cycling operations, with Pan American Petroleum Corp. (now Amoco Production Co.) as the Petroleum Corp. (now Amoco Production Co.) as the operator. Because of the configuration of the field14 miles long by about a mile wideit was necessary to install a rather unusual gas gathering and injection system. A long header was installed through the center of the field with each of the producing wells tied into the header by means of laterals. The injection compressors were located at the injection well sites, two on the east end of the field and three on the west. Gas is supplied to the compressors through the production header. High-Speed Machinery During the studies of the cycling project, it became apparent that the injection pressure would be extremely high, approaching 8,000 psig; consequently, bids for the compressor were solicited using this as a design discharge pressure. The design suction pressure was 1,500 psig, and the required injection volume was about 4,200 Mcf/D/well. An analysis of the quotations received showed that the cost of five highspeed (1,000 rpm), direct-connected, skid-mounted compressors was considerably less than comparable low-speed (300 to 400 rpm) integral machinery. Although there were no machines of this type running in such high-pressure service, the difference in cost made it attractive to use the high-speed machinery. The compressors selected were equipped with 4 two-stage "tandem" cylinders each. In this arrangement, the compressor piston rod and the pistons are constructed in one piece. The first stage pistons are constructed in one piece. The first stage of compression is performed on the crank end of the cylinder. A "dead space" between the two pistons is subjected to firststage suction pressure (Fig. 1). The first compressor was ready for start-up Feb. 9, 1967. Almost immediately upon loading, a problem developed with one of the compressor crossheads. problem developed with one of the compressor crossheads. Upon disassembly, it was determined that the crosshead pin bearing had failed. A second machine was ready to pin bearing had failed. A second machine was ready to start up and operations were shifted to that unit while repairs to Number One was undertaken. However, upon start-up of the second machine, the same problem appeared on a crosshead on this machine. Operations were suspended until rod loads could be recalculated, compressor loading procedures reviewed, and a revised design for the procedures reviewed, and a revised design for the crosshead pin bearing developed. Rod Loads Upon further consultation with the manufacturer, it was determined that the calculated rod loads of about 12,000 lb in compression and 3,000 lb in tension did not take into account the inertial effect of the weight of the connecting rod, crosshead, piston, and rod. As a consequence, thens was actually a nonreversing rod load; that is, the rod was always in compression. P. 424

Mechanical Design of Compressor Test Apparatus for Electron Ring Accelerator Research

The mechanical and vacuum features of the Compressor II apparatus used in the Fall 1968 Electron Ring Accelerator (ERA) experiment are described. Included are the injection beam transport system, the coils and their support structure, the ceramic vacuum chamber and its pumping system, the gas injection system, and diagnostic probes. The coil arrangement for the upcoming Compressor III experimental apparatus is briefly presented.

Selective Pumping of Light and Heavy Gases with a Molecular Pump

For some plasma experiments high purity hydrogen or deuterium at pressures of 10−3 Torr or less is required. It is shown that a molecular pump can be used as a combination pumping, gas injection, and gas purification system. The gas is admitted to the fore vacuum side and streams back to the high vacuum side. This does not materially affect the pumping of heavy impurities. Performance data for this mode of operation are given for the Pfeiffer pump TVP-500.

Mobility Ratio - Its Influence on Flood Patterns During Water Encroachment

Abstract The results of potentiometric model studies and numerical computations are described. The purpose of these studies was to determine the influence of the mobility ratio on flooding efficiencies during water encroachment in petroleum reservoirs, in systems of regular well geometry. The direct line drive well pattern having relative spacing distances of one and one-half to one was investigated for water to oil mobility ratios of 10, 1, and 0.1. The results of these studies indicate that the pattern sweep efficiency is very dependent upon the mobility ratio. Introduction The almost universal occurrence of water in the immediate neighborhood of oil-bearing sands lends considerable emphasis to the desirability of having a rational analysis of water encroachment into petroleum reservoirs. This problem has become increasingly important with the accelerated use of water injection for secondary recovery operations. The water encroachment problem has been studied from both the theoretical and experimental viewpoints by Muskat. He has formulated, in a precise manner, differential equations to express flow in a water encroachment system, and rigorous analytical solutions have been developed for the linear, radial, and spherical cases. However, it becomes exceedingly difficult to solve the encroachment problem rigorously for any general two-dimensional system in which the shape of the two-fluid interface is not immediately evident from the geometry of the system. The difficulty lies in the fact that a rigorous analytical solution requires that the shape of the two-fluid interface be known simultaneously with its instantaneous position and with the pressure distribution on both sides of the interface. Although this paper concerns the study of the two-fluid system of oil and water, the methods described in the paper are generally applicable to other systems of incompressible and immiscible fluids in which the displacing fluid sweeps the displaced fluid down to a residual value. In each region it is assumed there is only one mobile fluid and its mobility is constant throughout the region. The same procedure, with minor alterations, is applicable for gas injection systems provided the assumption can be made that both the displaced and displacing gases can be described by steady state formulas.