Showing papers on "Chamber pressure published in 1992"

Pressure regulating composite cartridge

Abstract: A plastic cased metal headed ammunition casing for high powered rifle and cannon cartridges is described in which the plastic case has a pressure regulating baffle or wall in the forward and thereof to regulate and control the development of chamber pressure and directs pressure into a space around the bore of the projectile prior to movement of the projectile. The cartridge is charged with a given charge of powder and the cap or head securely fastened to the rearward portion of the plastic casing. An expandable sleeve may be used to stabilize the head-casing interfit. The head provides sufficient resistance to the residual pressure after firing so that the cartridge can be used in rapid fire automatic weapons.

Flux Chamber Design and Operation for the Measurement of Municipal Solid Waste Landfill Gas Emission Rates

Abstract: This paper describes a hybrid Flux Chamber-Soil Gas Probe methodology for measuring municipal solid waste (MSW) gas emission rates. Following the design of the flux chamber, the chamber was laboratory tested to define its mixing characteristics and optimum operating parameter values. Flux chamber operating parameters included: chamber pressure, sweep air flow rate, landfill surface insertion depth, and sweep air velocity. Optimum operating parameter values were determined by operating the flux chamber on a simulated subsurface emission source and varying the operating parameters. The laboratory tests indicated that the flux chamber could be operated to provide zero biasing of gas emission rates, resulting in accurate measurement of gas emission rates.

Principal Component Analysis of Optical Emission Spectroscopy and Mass Spectrometry: Application to Reactive Ion Etch Process Parameter Estimation Using Neural Networks

Abstract: We report on a simple technique that characterizes the effect of process parameters (i.e., pressure, RF power, and gas mixture) on the optical emission and mass spectra of CHFJO2 plasma. This technique is sensitive to changes in chamber contamination levels (e.g., formation of Teflon-like thin-film), and appears to be a promising tool for real-time monitoring and control of reactive ion etching. Through principal component analysis, we observe that 99% of the variance in the more than 1100 optical and mass spectra channels are accounted for by the first four principal components of each sensor. Projection of the mass spectrum on its principal components suggests a strong linear relationship with respect to chamber pressure. This representation also shows that the effect of changes in thin-film levels, gas mixture, and RF power on the mass spectrum is complicated, but predictable. To model the nonlinear relationship between these process parameters and the principal component projections, a feedforward, multi-layered neural network is trained and is shown to be able to predict all process parameters from either the mass or the optical spectrum. The projections of the optical emission spectrum on its principal components suggest that optical emission spectroscopy is much more sensitive to changes in RF power than the mass spectrum, as measured by the residual gas analyzer. Model performance can be significantly improved if both the optical and mass spectrum projections are used (so called sensor fusion). Our analysis indicates that accurate estimates of process parameters and chamber conditions can be made with relatively simple neural network models which fuse the principal components of the measured optical emission and mass spectra. In the reactive ion etching (RIE) process, plasma characteristics depend on many parameters; some of these parameter values are set by the tool operator, e.g., chamber pressure, RF power, and gas flow, while others are internal to the condition of the chamber, e.g., thin-film thickness on the chamber walls, or the amount of material etched. Plasma characteristics can be observed using in situ measurements, e.g., via optical emission spectroscopy (OES) or residual gas analysis (RGA). How these measurements can be used to estimate the process parameters is the question

Hybrid gas generator for air bag inflatable restraint systems

Abstract: A gas generator includes a chamber in which inert gas under high pressure is stored, a diffuser chamber, and a chamber containing a pyrotechnic heater and initiator. Upon receiving an electrical signal the initiator fires igniting the pyrotechnic charge. As pressure in the combustion chamber of the pyrotechnic heater rises and exceeds the storage chamber pressure, a plug in a shoulder covering the pyrotechnic nozzle orifice is unseated, subsequently rupturing a thin metal sealing diaphragm since the latter is unsupported for a pressure differential in this direction. Hot gas and particles from the burning pyrotechnic heat the stored gas causing a rapid pressure rise in the storage chamber. When the storage chamber pressure exceeds the structural capability of a thin metal disc between the diffuser and storage chambers, it ruptures allowing the heated gas to vent through the diffuser orifices into the air bag assembly.

Numerical study of solid-fuel combustion under supersonic crossflows

Abstract: The combustion of solid fuels under supersonic crossflows has been studied using a comprehensive numerical analysis. The formulation is based on the time-dependent multidimensional compressible Navier-Stokes equations and species transport equations. Features of this approach include consideration of finite-rate chemical kinetics and variable properties. Turbulence closure is achieved using the Baldwin-Lomax algebraic model. The governing equations are solved numerically using a flux-vector splitting lower-upper symmetric successive overrelaxation technique that treats source terms implicitly. The effects of various operating conditions on the combustion behavior of the hydroxyl-terminated polybutadiene-based solid-fuel samples are treated in detail. Results indicate that both inlet temperature and pressure have strong influences on the burning rate of the fuel sample. For the operating range considered, an optimum pressure is required to maximize the burning rate. The sample burns increasingly faster with pressure from 1 to 4 atm. However, at a higher pressure, the energy released by combustion is not sufficient to further raise the temperature of the crossflow. This results in a decrease in heat feedback to the fuel sample, consequently causing a slight reversal of the burning rate trend with pressure.

Slant plate type compressor with variable displacement mechanism

Abstract: A variable capacity type slant plate compressor including a crank chamber a suction chamber and a discharge chamber is disclosed. The crank chamber is linked by a first communication path to the suction chamber, and is linked by a second communication path to the discharge chamber. A first valve control mechanism is disposed within the first communication path. A second valve control mechanism is disposed within the second communication path. The first valve control mechanism controls the opening and closing of the first communication path so that the suction chamber pressure is maintained at a predetermined constant value. The second communication path is compulsorily opened by operation of the second valve control mechanism in response to an external signal so as to compulsorily minimize the capacity of the compressor. A throttling device is disposed within the second communication path between the discharge chamber and the second valve control mechanism so that the capacity of the compressor is compulsorily quickly minimized without damage of the internal component parts of the compressor.

Seal leakage monitoring device and method

Abstract: A device for monitoring for fluid leakage in a double stem seal valve (24). The valve housing (25), stem (28), primary stem seal (30), and secondary stem seal (34) define a chamber (36) bounded therebetween. A pressure gauge (44) having a pointer (48) for registering and retaining a maximum pressure reading is mounted on the valve (24) and via a port (38) is in fluid communication with the chamber (36). Fluid leakage into the chamber (36) sufficient to increase the chamber pressure can be registered and retained by the pointer (48), indicating the failure of the primary stem seal (30) and the occurrence of a leak.

Pressurized diaphragm pump and directional flow controller therefor

Abstract: A diaphragm pump is provided comprising a pump chamber, a diaphragm, an enclosure, a diaphragm reciprocator, and an enclosure pressure regulator. A valve which may be used with the diaphragm pump is also provided. The valve comprises a chamber, a chamber pressure regulator, and a timer motor for rotating a rotor to control fluid communication between the chamber and a fluid outlet.

Emission spectroscopic study of a low pressure supersonic Ar-H2 DC plasma jet

Abstract: An emission spectroscopic study is reported of the temperature and the electron density distributions in a DC plasma jet at atmospheric and low pressure conditions. A standard DC plasma spraying torch is used with an Ar-H2 mixture as the plasma gas (17% H2 by volume) at a power level of 30 kW (current=600 A, voltage=50 V). Results were obtained for chamber pressures of 100 kPa, 52 kPa and 20 kPa. Electron density measurements were carried out by the Stark broadening of the Hbeta line and from the continuum recombination of the Ar+ and H+ ions. The temperature is obtained by using a Boltzmann plot of the neutral argon lines and the absolute intensity measurements of the argon lines. The results confirm that local thermodynamic equilibrium (LTE) conditions prevail throughout most of the temperature field at pressures of 100 and 53 kPa. Important deviations from LTE conditions are noted at a chamber pressure of 20 kPa. The results at the lowest pressure condition (20 kPa) show important axial variations of the electron density which coincide with the observed diamond shock wave in the plasma jet.

Isolated heart perfusion appts. - has closed vessel with fluid and adjustable gas vol. to give timed aorta pressure

Abstract: The appts. has a feed channel (16b, 16c) interrupted by a closed vessel (31) partially filled with fluid and partially with gas. The gas vol. is adjustable in the vessel (31). Pref. the vessel (31) has a passage drilling (38) near the liq. filler, with a closure held against its outlet at a defined pressure so that, when the pressure is exceeded, liq. can move out of the vessel (31). Fluid moving out of the vessel (31) passes through a return channel (45) back to the reservoir. The drilling (38) outlet is covered by an elastic membrane against a chamber with a defined inner pressure, and the edges of the membrane are sealed against a plate with a second drilling (38) to the other (39) within the membrane cover and out to the return channel (45). The chamber at the outer side of the membrane is connected (55) to a spindle injection (56) piston/cylinder (58,57) system to set the chamber pressure. A manometer (61) shows the chamber pressure at the rubber membrane. The plate for the drillings (38,39) is identical to a vessel (31) wall. USE/ADVANTAGE - The appts. is for the perfusion of a heart, to keep it working, such as before transplanation. The assembly gives an adjustable timed operation of the aorta pressure.

Spring-loaded pressure regulating valve including rolling diaphragm and compensation for variation of spring force with diaphragm displacement

Abstract: A chamber (24) is filled with a fluid whose pressure is to be regulated to a predetermined value. A valve (30) is disposed between the chamber (24) and a high pressure source of the fluid. A rolling diaphragm (18) has a face (18c) exposed to the fluid in the chamber (24), and actuates the valve (30) to connect the chamber (24) to the source when the chamber pressure drops below the predetermined value and to disconnect the chamber (24) from the source when the chamber pressure rises to substantially the predetermined value. A spring (26) urges the diaphragm (18) against the chamber pressure with a force corresponding to the predetermined pressure value. A piston (14) is connected between the spring (26) and the diaphragm (18) and is formed with a ramp portion (14b) over which a rolling portion (18b) of the diaphragm (18) extends and varies the effective diameter of the diaphragm (18) as a predetermined function of the longitudinal position of the diaphragm such that the force exerted on the diaphragm (18) by the chamber pressure is maintained substantially equal to the force exerted on the diaphragm (18) by the spring (26). This compensates for variation of the spring force as the fluid flow rate through the valve (30) and thereby the position of the diaphragm (18) change and maintains the regulated pressure constant. A bistable element (42) may be provided to urge the diaphragm (18) toward first and second longitudinal positions in which the valve (30) is open and closed respectively.

A study of defects induced in GaAs by plasma etching

Abstract: The effect of plasma dry etching on GaAs has been studied by photoreflectance (PR) and deep-level transient spectroscopy (DLTS). GaAs samples were etched by CF4 plasma under different conditions to study the influence of sputtering chamber pressure and power on surface properties. Rapid thermal annealing (RTA) was conducted to remove plasma-induced damage. Schottky diodes were fabricated on the plasma etched wafers for electrical characterization. A 10 mTorr/50 W plasma etched sample showed two new peaks with energies lower than the bandgap energy which may imply defect introduction. Plasma processing at 50 mTorr/100 W and 100 mTorr/150 W also showed damage with a reduced PR signal and one lower energy peak. Franz-Keldysh oscillation (FKO) was observed in most samples. The FKO period was used to characterize sample surface quality. DLTS measurement showed plasma-induced deep levels on every plasma etched sample. The higher chamber pressure and power gave increased activation energy. Activation energies of 0.38, 0.57 and 0.67 eV were found for 10, 50 and 100 mTorr chamber pressure etching conditions, respectively. The 450°C/10 s RTA showed very good recovery on all plasma-induced damage.

Operation between valve points of a partial-arc admission turbine

Abstract: A method for improving operational efficiency of a partial-arc steam turbine power plant during power output variations by dynamically adjusting valve point values during turbine operation Impulse chamber pressure at each of a plurality of valve points is first determined during operation of the steam turbine at constant pressure For each adjacent pair of valve points, an optimum constant pressure transition point pressure for transitioning from one to the other of the sliding pressure mode and constant pressure mode is then computed The optimum constant pressure transition point pressure for each pair of valve points is converted to a corresponding percentage of the pressure difference between the adjacent pairs of valve points The impulse chamber pressure at each valve point is then used to calculate a corresponding impulse chamber pressure for transitioning from the one mode to the other mode based upon the percentage pressure difference During the transition, the control valve associated with the transition point and valve point is gradually closed

Advanced tube-bundle rocket thrust chambers

Abstract: An advanced rocket thrust chamber for future space application is described along with an improved method of fabrication. Potential benefits of the concept are improved cyclic life, reusability, and performance. Performance improvements are anticipated because of the enhanced heat transfer into the coolant which will enable higher chamber pressure in expander cycle engines. Cyclic life, reusability and reliability improvements are anticipated because of the enhanced structural compliance inherent in the construction. The method of construction involves the forming of the combustion chamber with a tube-bundle of high conductivity copper or copper alloy tubes, and the bonding of these tubes by an electroforming operation. Further, the method of fabrication reduces chamber complexity by incorporating manifolds, jackets, and structural stiffeners while having the potential for thrust chamber cost and weight reduction.

Hot fire fatigue testing results for the compliant combustion chamber

Abstract: A hydrogen-oxygen subscale rocket combustion chamber was designed incorporating an advanced design concept to reduce strain and increase life. The design permits unrestrained thermal expansion of a circumferential direction and, thereby, provides structural compliance during the thermal cycling of hot-fire testing. The chamber was built and test fired at a chamber pressure of 4137 kN/sq m (600 psia) and a hydrogen-oxygen mixture ratio of 6.0. Compared with a conventional milled-channel configuration, the new structurally compliant chamber had a 134 or 287 percent increase in fatigue life, depending on the life predicted for the conventional configuration.

Numerical study of low pressure nuclear thermal rockets

Abstract: The flowfields and performance of low pressure nuclear thermal rockets, which use hydrogen as a propellant, are studied by solving the Navier-Stokes equations and the species equations. A finite-rate chemistry model is used in the species equations, and the turbulence is simulated by the Baldwin-Lomax turbulence model with a modified van Driest's damping constant. The calculated results for the chamber temperatures of 3200 K and 4000 K with a chamber pressure range of 0.1 atm to 6 atm are presented as contours, centerline variations, and exit profiles. The performance values from the present calculations, such as the vacuum specific impulse and thrust, are compared with those from the 1D, inviscid equilibrium and frozen flow code.

The neck chamber technique.

Abstract: Since the first description of the neck chamber technique for stimulating carotid baroreceptors by Ernsting and Parry in 1957, a number of different neck collars have been realized, among which the simplified version devised by Eckberg and coworkers in 1975 and the neck chamber described by Ludbrook and coworkers in our Institute in 1977. At variance with Eckberg's type, the "Milan neck chamber" completely surrounds the neck and allows the application of both positive and negative pressures to the neck by means of a system of double rubber valves that prevents air leakage from the chamber. The main advantage of this technique, as compared to infusion of vasoactive drugs, is the possibility it offers to study baroreflex control not only of heart rate, but also of peripheral resistance and blood pressure through neck chamber induced changes in carotid transmural pressure. In recent years a systematic evaluation of the neck chamber technique has allowed to clarify the following issues: 1) application of positive pressure to the neck, although increasing internal jugular venous pressure and thereby reducing the pressure gradient from the arterial versus the venous side of head circulation, does not reduce cerebral blood flow; 2) changes in pressure within the neck chamber do not seem to reduce blood flow to the carotid bodies, at least to a degree which might lead to chemoreceptor stimulation; 3) there is a linear relation between changes in neck chamber pressure and changes in tissue pressure adjacent to the carotid sinus. The transmission of pressure to pericarotid tissues is complex, however.(ABSTRACT TRUNCATED AT 250 WORDS)

Hydraulic safety coupling with flexible-walled pressure chamber - has chamber pressure release outlet covered by protective shield, fitted with fluid absorbing and retaining material

Abstract: A hydraulic safety coupling has a flexible-walled pressure chamber (16) pressurised to lock two components (2,12) together. Relative rotational movement between the two components, occurring at excessive torque levels, releases the pressure allowing the components to then rotate freely. The chamber outlet (32) has a protective shield (60), with fluid absorbing and retaining material (64) fitted to the shield opposite the outlet. ADVANTAGE - The high pressure fluid release is effectively captured.t

Theoretical modeling of the interior ballistic processes in an electrothermal chemical gun

Abstract: A comprehensive theoretical model has been developed to describe the interior ballistic processes in an electrothermal chemical (ETC) gun. The model, which takes into account the plasma/working fluid interaction, predicts transient and spatial variations of the gun chamber pressure, instantaneous projectile motion, and gun muzzle velocity. A complete set of governing equations is derived from first principles of physics, and the governing system is solved by an implicit finite difference scheme. Two sets of pulse-forming network (PFN) discharge curves, with various peak power times and total discharge times; are employed to study the ETC gun performance. The numerical results show that a ballistic efficiency of more than 13% can be achieved for an exothermic working fluid (C8H18/H2O2). The breech pressure and projectile-base pressure exhibit double peaks during the ballistic cycle. The first peak is due to the initial discharge of a plasma jet into the gun chamber, whereas the second peak is the result of vigorous interactions between the plasma jet and the working fluid. The calculated maximum breech pressure is on the order of 400 MPa, and a typical muzzle velocity is on the order of 2 km/s. Comparison of present numerical results with limited available experimental data is made and found to be good.

Handling process for magnesium and magnesium alloy melts - with contamination free charging and melting in protective atmosphere, constant melt feed by differential pressure and controlled furnace pressure

Abstract: Handling process for magnesium and magnesium alloy melts, comprises (a) contamination-free charging and melting under protective gas atmos., (b) constant melt feed with controlled differential pressure and (c) control of furnace chamber pressure for accurate metering and for compensation of low pressure equipment to be fed. Process equipment is also claimed. Pref. before charging all media conducting parts are evacuated, purged with protective gas and supplied with protective gas atmosphere. Differential pressure is produced by pressurisation and evacuation of the furnace chamber. The melt is treated by homogenisng agitation and/or gassing or by charging premelted material from a holder. Process equipment comprising metering melting furnace with charging equipment, from which melt is fed by differential pressure to subsequent process unit is covered by other claims. USE/ADVANTAGE - Provides improved process and equipment for handling magnesium alloy melts by the differential pressure metering principle, with virtually contamination-free and safe melting, melt metering and holding.

A study of metal‐oxide‐semiconductor capacitors fabricated on SF6 and SF6+Cl2 reactive‐ion‐etched Si

Abstract: Metal‐oxide‐semiconductor capacitors have been fabricated on SF6 and SF6+Cl2 reactive‐ion‐etched silicon in order to study the resulting defects at the Si‐SiO2 interface and in the bulk of the silicon substrate. The reactive‐ion‐etching (RIE) induced damage reveals itself by the presence of positive charge in the oxide, by interfacial states, and by two deep levels in the silicon bulk located at 300 and 335 meV above the valence band and probably related to fluorine atoms. We have studied the effect of the chamber pressure and the plasma composition on the resulting damage. This damage is more important when the chamber pressure is low because of the higher free‐mean path of the plasma ions. On the other hand, when the Cl2 concentration in the plasma is raised the densities of interface states and of the deep levels decrease while the positive charge in the oxide increases. Finally, we have shown that a post‐RIE thermal annealing can be used to restore the electrical properties of the RIE‐damaged silicon surfaces.

Pressure diecasting machine feed

Abstract: The proposal is for a metering and loading device for pressure casting machines which is used in a cold chamber pressure casting machine to transport the metal melt between a heat retention device and the casting chamber of the machine. In order to determine the precise weight or the volume determinable therefrom of the metal melt to be taken to the casting chamber, there is an additional weighing device (22, 22') which is either allocated directly to the metering ladle (9) or finds the weight of the metal melt via a separate intermediate or preliminary container (23).

Hydraulic operation circuit

Abstract: PURPOSE: To relax impact at the time when an actuator is stopped by providing a compound control valve in which a pressure compensated flow control valve loaded with a spring load and a variable throttle valve which corresponds to the pressure of a change-over valve operation oil pressure chamber are arranged in parallel, in a space between a pilot valve and a change-over valve operation oil pressure chamber, and discharging the pressurized oil in the operation oil pressure chamber through the compound control valve. CONSTITUTION: When a pilot valve 10 is quick-operated to a neutral position in order to stop an actuator 18, a signal oil in the operation oil pressure chamber of a change- over valve 30 is discharged through a compound control valve 60 into a signal line 12 by the action of a spool 36 returning to the neutral position. In a pressure compensated flow control valve 40, the discharge is set to a reduced constant, since the oil is discharged from a flow control valve 42 loaded with a spring load through the reduced operation oil pressure chamber pressure. However, in a variable throttle valve unit 50, the discharge is changed to be reduced, since the throttle spool 52 opening is controlled in the direction 'open' in response to the operation oil pressure chamber pressure. Thus, the response time of the change-over valve is shortened, a sense of incongruity in operation is eliminated, and the impact due to the stopping of the actuator is relaxed.

Propellant production from the Martian atmosphere

Abstract: Results are presented from a calculation of the specific impulses that can be generated through the combustion of cryogenic CO and O2 over a range of fuel/oxidizer ratios, chamber pressures, nozzle expansion ratios, freestream pressures representative of Mars, and the limiting conditions of equilibrium and frozen nozzle flow. For an expansion ratio of 80 and 100-atm. chamber pressure, a specific impulse of 298 sec was obtained; this is comparable to the best solid rocket propellants.

Turbopump options for nuclear thermal rockets

Abstract: Several turbopump options for delivering liquid nitrogen to nuclear thermal rocket (NTR) engines were evaluated and compared. Axial and centrifugal flow pumps were optimized, with and without boost pumps, utilizing current design criteria within the latest turbopump technology limits. Two possible NTR design points were used, a modest pump pressure rise of 1,743 psia and a relatively higher pump pressure rise of 4,480 psia. Both engines utilized the expander cycle to maximize engine performance for the long duration mission. Pump suction performance was evaluated. Turbopumps with conventional cavitating inducers were compared with zero NPSH (saturated liquid in the tanks) pumps over a range of tank saturation pressures, with and without boost pumps. Results indicate that zero NSPH pumps at high tank vapor pressures, 60 psia, are very similar to those with the finite NPSHs. At low vapor pressures efficiencies fall and turbine pressure ratios increase leading to decreased engine chamber pressures and or increased pump pressure discharges and attendant high-pressure component weights. It may be concluded that zero tank NSPH capabilities can be obtained with little penalty to the engine systems but boost pumps are needed if tank vapor pressure drops below 30 psia. Axial pumps have slight advantages inmore » weight and chamber pressure capability while centrifugal pumps have a greater operating range. 10 refs.« less

Improved device for bed-sore prevention and cure

Abstract: The utility model relates to an improved device for bedsore prevention and treatment, which comprises multiple sets of air cushions with multiple chambers, an air supply controller and a plurality of guiding pipes communicating the former two, wherein, a main chamber cavity on the cushion is made of a cushion body and an upper layer film via the adhesive joint, hot pressing or tailoring process, while a communicating passage between the chambers is made of the cushion body, an upper layer film and a lower side film through the same process as a double-layer printed-circuit board into a flat communicating air hole. A distributing valve at the n position in the controller is provided with blind holes in the number of n minus two, so as to maintain and stabilize the chamber pressure of the chamber set corresponding to the blind hole. In the controller, a heating pipe coupling can be connected in series in the intake channel of an air feed pump. The intake channel of the heating pipe coupling is connected inside with a three-way pipe for recovering waste heat.

Glow plug mounted on cylinder head of IC engine having auxiliary chamber - has heating rod extending into latter for cold start and withdrawing as running heats up

Abstract: The glow plug assembly has a heater rod and temp. controlled medium for contact so that, when the engine starts, the rod is forced deep into the ancillary chamber by a load spring. In engine operating conditions, however combustion heat and chamber pressure force the rod back out. The heater rod (5) is enclosed by an insulating sleeve (6) fixed to the rod and with a back stop in the form of a collar (15) to divide the main (14a) and ancillary (14b) chambers with the result that, as combustion heat increases, the medium is forced over through a transfer section from the main to the ancillary chamber. USE/ADVANTAGE - Compact design providing self-controlled movement from start to steady running positions.