Showing papers on "Chamber pressure published in 1985"

Use of laboratory data in freeze drying process design: heat and mass transfer coefficients and the computer simulation of freeze drying.

Abstract: Freeze drying process development normally proceeds via an empirical “trial and error” experimental approach which is both time consuming and uncertain in reliable extrapolation to production equipment. This research describes the use of phenomenological theory, with key parameters determined by laboratory experiments, to guide the experimental program to optimize the primary drying stage of the process for a given product/container combination. The theoretical description of primary drying is a problem in coupled heat and mass transfer which can be satisfactorily described using a steady-state model where the heat flow is given by the product of the mass flow and the heat of sublimation. Generally, mass transfer is impeded by three barriers or resistances: resistance of the dried product layer, resistance of the semi-stoppered vial, and resistance of the chamber. Resistance, defined as a ratio of pressure difference to mass flow, is experimentally determined for each barrier. The resistance of the dried product normally increases with time as the thickness of dried product increases and typically accounts for over 90% of the total resistance to mass transfer. Heat flow from the shelf surface to the subliming ice is impeded by three barriers: the interface between the shelf surface and the bottom of the tray used to contain the vials, the interface between the tray and the vial bottom, and the ice between the bottom of the vial and the sublimation surface. Heat flow is described in terms of heat transfer coefficients, defined as the ratio of the heat flux to temperature difference, where the heat transfer coefficients are experimentally determined for each vial and tray of interest. Vial and tray heat transfer coefficients increase with increasing pressure and are quite sensitive to variations in degree of flatness of the vial or tray bottom. Steady-state transport theory is used to define six equations with eight variables where the equations contain mass transfer resistances and heat transfer coefficients which are determined from laboratory experiments. The variables are the sublimation rate and the pressures and temperatures throughout the system. Our procedure is to fix two of the variables (i.e., chamber pressure and shelf temperature) and solve, via a computer program, for the other six variables. Solutions are obtained for 0, 20, 40, 60, 80. and 100% completion of primary drying, thereby providing sublimation rate and the relevant temperatures and pressures as a function of time during the freeze-drying cycle defined by the input parameters chosen (i.e., the chamber pressure and shelf temperature profile with time). Thus, computer-generated freeze-drying cycles may be generated for any combination of product, container, and process parameters desired. Agreement between theoretical and experimental cycles is satisfactory. Use of this approach is demonstrated with the following applications: (1) a study of the effect of changes in chamber pressure and shelf temperature on drying time and product temperature: (2) the effect of shelf temperature variability and vial heat transfer coefficient variability on uniformity of drying: and (3) cycle optimization.

Compressor capacity control

Abstract: The capacity of a refrigerant compressor comprising a wobble plate assembly (15, 16, 17) for reciprocating pistons 22 in cylinders (32) is varied by adjusting the slant angle of the wobble plate. The slant angle is controlled by variation of the pressure level in a chamber (13) in which the wobble plate is disposed. The chamber pressure is controlled by an intermittently operated electromagnetic valve (41) which controls communication between the chamber (13) and a suction chamber 35. The valve operates in response to pulsatory signals having a variable duty ratio. A comparator emits the signals in response to input signals from a delta wave oscillator and a micro computer.

Method and apparatus for improved ion dose accuracy

Abstract: The implant chamber pressure during ion implantation is controlled within a specified intermediate pressure range higher than the baseline pressure. Implanted dose errors resulting from neutralizing collisions of the beam with residual gas molecules are held constant and can be compensated. The pressure is maintained within the specified intermediate pressure range by a control system including a controllable vacuum valve associated with a vacuum pump, a chamber pressure sensor and a valve controller responsive to the pressure sensor. The valve controller opens and closes the valve to maintain the chamber pressure within the specified range after introduction of a wafer.

The Effect of Pressure Change Rate on the Eustachian Tube Function in Pressure Chamber Tests

Abstract: The capacity of the Eustachian tube to equilibrate pressure differences across the eardrum was tested repeatedly at different rates of pressure change with the aid of a quantitative impedance method in a pressure chamber. Three recordings of the active and passive pressure equilibration functions were made during chamber pressure changes of 0.3, 0.7 and 1.5 kPa-1s in 53 ears in 28 otologically healthy subjects. The middle ear pressures at which the active and passive equilibrations were achieved increased with increasing rates. The test-retest reliability was not rate dependent as regards the passive pressure equilibration functions, but tended to deteriorate with increasing rates for the active equilibration functions. Advantages and disadvantages of the different rates in such tests are discussed.

Induction period for ignition of fuel sprays at high temperatures and pressures

Abstract: An experimental study of the induction period for ignition of fuel sprays with particular consideration of its dependence upon temperature and pressure is reported. Emphasis in the study was placed upon conditions of thermodynamically supercritical state for the fuel. The tests were performed in a stainless steel cylindrical chamber located in an oven, both provided with quartz windows for optical insight in axial direction of the radially injected spray. Spray formation and igniton were observed by high-speed schlieren cinematography concomitantly with measurements of chamber pressure and the displacement of the injector needle. The induction period was evaluated as the time interval between the rise in the displacement transducer signal and the instant when pressure attained three percent of its peak value.

Cyclic speed control apparatus in variable stroke machines.

Abstract: A free piston engine includes speed control means which provide a wide range of engine speed control for selective connection and use of the engine with any one of a number of different types of energy absorbing devices. The desired control is achieved by use of two bounce chambers (18p and 18n) and a double-acting bounce piston unit (16) specifically located at an intermediate position along the axis of reciprocation of the piston rod assembly of such an engine, i.e. between a power piston (15) at one end of the piston rod and a connecting means at the other piston rod end for driving connection of the piston rod assembly with a movable member (e.g. reciprocating compressor piston (34) or reciprocating electric generator member) of the selected energy absorbing device. The control means further includes at least one pair of variably adjustable bounce chamber pressure control valves (23 and 24), one for each bounce chamber. Each control valve of such one pair provides for and controls a direct connection of its respective bounce chamber to ambient atmospheric air outside the bounce chamber. The controls further include sensing means (37) responsive to changes in demands on or operation of the selected energy absorbing device for variably and substantially simultaneously adjusting each control valve of such one pair and thereby similarly changing (i.e. both upwardly or both downwardly) the respective bounce chamber working pressures. Other bounce pressure control features are also described.

Pressure control device and method of making the same

Abstract: A pressure responsive control device having a pressure housing assembly defining a pressure chamber, an actuable control fixed to the housing assembly and, a pressure transducer module hermetically closing the pressure chamber. The module includes a snap acting pressure responsive diaphragm, a diaphragm control plate hermetically bonded to the diaphragm outer periphery, and a support member hermetically joined to and supporting the control plate and hermetically joined to the housing assembly. The control plate has a supporting region rigidly supporting the diaphragm and the diaphragm control regions are yielded and deformed relative to the supporting region to position the control regions for stressing the diaphragm to determine the chamber pressure levels at which the diaphragm moves.

Ignition characterization of LOX/hydrocarbon propellants

Abstract: The results of an evaluation of the ignition characteristics of the gaseous oxygen (Gox)/Ethanol propellant combination are summarized. Ignition characterization was accomplished through the analysis, fabrication and testing of a spark initiated torch igniter and prototype 620 1bF thruster/igniter assembly. The igniter was tested over a chamber pressure range of 3.3 to 262 psia and a mixture ratio range of 0.4 to 40. The prototype thruster/igniter assembly was tested over the chamber pressure range of 74 to 197 psia and mixture ratio range of 0.778 to 3.29. Cold (-92 to -165 F) and ambient (44 to 80 F) propellant temperatures were used. Spark igniter ignition limits and thruster steady state and pulse mode, performance, cooling and stability data are presented. Spark igniter ignition limits are presented in terms of cold flow pressure, ignition chamber diameter and mixture ratio. Thruster performance is presented in terms of vacuum specific impulse versus engine mixture ratio. Gox/Ethanol propellants were shown to be ignitable over a wide range of mixture ratios. Cold propellants were shown to have a minor effect on igniter ignition limits. Thruster pulse mode capability was demonstrated with multiple pulses of 0.08 sec duration and less.

Capacity controller for variable angle swing swash type variable capacity compressor

Abstract: PURPOSE: To improve the sealing property of a crank chamber by disposing a condenser, an expansion valve, an evaporator and an evaporation pressure regulating valve in a circulation pipe path from a discharge chamber to a suction chamber of a compressor and affording always communication between the crank chamber and a suction path before the regulating valve from the evaporator to the evaporation pressure regulating valve. CONSTITUTION: While an evaporation pressure regulating valve 27 is opened and total capacity running is carried out, cooling load is reduced and pressure in a suction path 36 before the regulating valve, i.e., evaporation pressure Pe is reduced so that the opening of said valve 27 is reduced to restrain the reduction of the evaporation pressure. Also, pressure Pc in a crank chamber 7 follows up said pressure Pe to be equalized thereto and restrained with respect to the reduction of crank chamber pressure Pc. Further, when the opening of said valve 27 is reduced, suction pressure Ps is reduced and the difference between pressures Pc and Ps is increased to that the piston stroke is reduced to provide small capacity running. Thus, the pressure in the crank chamber is maintained at the set pressure so that the surface pressure on a shaft seal is constant to improve the sealing property. COPYRIGHT: (C)1987,JPO&Japio

Low-thrust LO2/LH2 engine performance with a 300 - 1 nozzle

Abstract: Altitude simulation tests for a thrust chamber with a 300:1 area ratio nozzle were conducted to evaluate the performance potential of a hydrogen/oxygen propellant system with a 4200 N (943 Ibf) thrust level and a chamber pressure of 3.5 MPa (507 psia). The thrust chamber consisted of a channel wall combustion chamber with a brazed copper powder close out and a dump/film cooled nozzle extension. Measured specific impulses were compared with numerical predictions. There was reasonable agreement between observed and predicted performances. A specific impulse of 458 s was obtained at a chamber mixture ratio of 5.0 for an injector with 98% c* efficiency. An apparent effect of unburned propellant reaction in the nozzle for the less efficient injector was observed. A new method for fabrication of a combustion chamber and the effect of film cooling by the dumped hydrogen are also described briefly.

Rocket thrust chamber thermal barrier coatings

Abstract: Subscale rocket thrust chamber tests were conducted to evaluate the effectiveness and durability of thin yttria stabilized zirconium oxide coatings applied to the thrust chamber hot-gas side wall. The fabrication consisted of arc plasma spraying the ceramic coating and bond coat onto a mandrell and then electrodepositing the copper thrust chamber wall around the coating. Chambers were fabricated with coatings .008, and .005 and .003 inches thick. The chambers were thermally cycled at a chamber pressure of 600 psia using oxygen-hydrogen as propellants and liquid hydrogen as the coolant. The thicker coatings tended to delaminate, early in the cyclic testing, down to a uniform sublayer which remained well adhered during the remaining cycles. Two chambers with .003 inch coatings were subjected to 1500 thermal cycles with no coating loss in the throat region, which represents a tenfold increase in life over identical chambers having no coatings. An analysis is presented which shows that the heat lost to the coolant due to the coating, in a rocket thrust chamber design having a coating only in the throat region, can be recovered by adding only one inch to the combustion chamber length.

Braking pressure control unit

Abstract: A braking pressure control unit is of the kind in which the stepped pistons (14, 15) of the or each proportioning control valves (8, 9) has an effective surface (A1) exposed to the pressure of a control chamber (60, 61) which communicates with the inlet (4) of a brake circuit via a valve seat (32) engageable by an inertia element (33). The control chamber pressure acts on the effective surface (A1) in the control valve closing direction. The inertia element (33) is moved away from its associated valve seat (32) by a sufficient vehicle deceleration. One of the stepped pistons carries an extension (40) forming a stop (41) for the inertia element (33) so that, in the initial unpressurised state, the connection between the control chambers (60, 61) and the inlet (4) is held open, but is closed by the inertia element (33) as the stepped piston is displaced by increasing input pressure before closing of the control valve (8) and is opened again at the set deceleration. Depending on the pressurisation of the effective surface (A1) there will result an increased change-over pressure and a changed reduction ratio for the loaded vehicle and upon failure of the brake circuit. In Fig. 2 (not shown) the inertia value axis is perpendicular to the central valve axes.

Supply device of cooling water in multistage mechanical seal

Abstract: PURPOSE:To maintain a quantity of cooling water to a fixed level even if a pump causes a change of its suction pressure, by independently arranging a pressure reducing device in supply inlets of cooling water to a multistage mechanical seal and providing a channeling system which bypasses the mechanical seal from its cooling water outlet in a low pressure side to the cooling water inlet in a high pressure side. CONSTITUTION:A supply device of cooling water provides pressure reducing devices 8-11 in a cooling waterway system to mechanical seals 4, 5, provided in a rotary shaft 3, while a passage, which bypasses the mechanical seal through a check valve 12 and the pressure reducing device 11, between an inlet of the mechanical seal 4 and an outlet of the mechanical seal 5. Accordingly, a chamber pressure of the mechanical seals 4, 5 comes to be almost in a fixed level by opening the check valve 12 if the suction pressure of a pump decreases. As a result, the supply device can hold the cooling water to a fixed quantity even if the pump causes a change in its suction pressure.

Improved air weft insertion nozzle control system

Abstract: not available for EP0067994Abstract of corresponding document: GB2105377The actuation of a nozzle utilized for propelling the yarn in an air weft insertion weaving system is controlled be means of a single rotary servo valve (31) having an arrangement of ports (95, 103, 105, 107) adapted to be brought during valve rotation into registration alternately with an air pressure source and with the atmosphere for alternately pressurizing and venting a pilot chamber (170) for opening and closing the nozzle. Preferably, the rotary valve (31) includes a rotary spool (75) enclosed with a sleeve of air permeable material to provide an air bearing for the spool. The actuation of the nozzle is determined by the movement of a diaphragm valve (180) toward and away from the opening of a nozzle supply chamber (156) under the control of the pilot chamber pressure, and the diaphragm is deformed into two annularly separated generally U-shaped convolutions (212, 214) opening toward the interior of the air supply chamber of the nozzle so that the movement of the diaphragm during opening and closing follows a 'rolling' or progressively flexing action as the convoluting side walls telescope outwardly and inwardly relative to one another. Preferably, two substantially similar convoluted diaphragms (180, 210) are disposed in axially spaced oppositely directed relation, one exposed to the nozzle supply pressure and the other to the pilot chamberpressure. Advantageously, the interior space between such diaphragm is vented (224) to the atmosphere to maintain a pressure-free condition therein and clearances are provided to prevent entrapment of air resisting deflection of either diaphragm.

Outgassing of Photoresist During Ion Implantation

Abstract: Outgassing of HUNT HPR 204 photoresist during ion implantation has been characterized by means of quadrupole mass analysis. The influence of the various parameters (implantation energy, beam current, ion species) has been studied in order to point out the evolutions, in terms of time or implanted dose, of the target chamber pressure and the peaks at masses 26 and 28, characteristic of the photoresist outgassing. The pressure integral in the target chamber which is easily related to the integrated outgassing flux, has been found essentially dependent on the total energy deposited in the photo-resist layer and on the ion penetration depth.

Modifications to the nozzle test chamber to extend nozzle static-test capability

Abstract: The nozzle test chamber was modified to provide a high-pressure-ratio nozzle static-test capability. Experiments were conducted to determine the range of the ratio of nozzle total pressure to chamber pressure and to make direct nozzle thrust measurements using a three-component strain-gage force balance. Pressure ratios from 3 to 285 were measured with several axisymmetric nozzles at a nozzle total pressure of 15 to 190 psia. Devices for measuring system mass flow were calibrated using standard axisymmetric convergent choked nozzles. System mass-flow rates up to 10 lbm/sec are measured. The measured thrust results of these nozzles are in good agreement with one-dimensional theoretical predictions for convergent nozzles.

A high-precision automatic closed-circuit respirometer for small animals

Abstract: An automatic apparatus for the continuous measurement of O2 consumption of small laboratory animals is described. By use of a high-sensitivity pressure transducer with associated circuitry together with a peristaltic O2 delivery system, the closed respirometer chamber is maintained at atmospheric pressure +/- 0.5 mmH2O. O2 delivery is measured to within 0.25 ml by recording rotations of the peristaltic pump, following calibration by the withdrawal of a preset volume of air from the chamber. Static trials (with the chamber empty) indicate a high degree of reproducibility of data with the chamber pressure remaining at atmospheric pressure +/- 0.5 mmH2O as a result of the proportional, as opposed to fixed-volume, delivery of O2. Trials with mice and rats have likewise produced data with a high degree of reproducibility.

An atomic hydrogen propulsion system

Abstract: P ERFORMANCE characteristics of a space propulsion system utilizing atomic hydrogen as a propellant are calculated. This thruster could be utilized for missions which require reliable long life operation, such as attitude correction, stationkeeping, and orbit change. A schematic diagram of the atomic hydrogen space propulsion thruster is shown in Fig. 1. An important feature of the engine is that atomic H is used as soon as it is produced by the discharge, thus eliminating the difficult problem of storage.' A mathematical model which describes the reaction chamber is presented; however, details of the microwave discharge, connecting regions, and other parts of the propulsion system are not discussed. The H2 is assumed to be completely dissociated by the microwave discharge with no impurities. The mathematical model is formulated in terms of a derived set of coupled nonlinear, first-order, differential equations governing the rate of formation and collisional dissociation of H2 and various energy loss mechanisms. These, in addition to the rate equation governing the density of atomic hydrogen in the chamber, are solved using iterative procedures. Based upon a specified flow rate of atomic hydrogen into the reaction chamber, values are given for the thrust, specific impulse, reaction chamber pressure and gas temperature, and the densities of H and H2 inside the reaction chamber for a spherical reaction chamber geometry.

Automatic measurements of transport properties during freeze-drying of food.

Abstract: AN AUTOMATIC MEASUREMENT SYSTEM HAS BEEN DEVELOPED TO DETERMINE THE THERMAL CONDUCTIVITY AND PERMEABILITY FOR THE DRIED LAYER OF FOOD SAMPLE AND TO DISPLAY THE DRYING CHARACTERISTICS OF THE SAMPLE TESTED AS WELL AS CORRESPONDING OPERATING CONDITIONS, USING MICROCOMPUTER CONNECTED TO EXPERIMENTAL FREEZE-DRYER. UNDER THE CONDITIONS OF CHAMBER PRESSURE USED IN COMMERCIAL OPERATION, COFFEE SOLUTIONS OF 2-45% AND THE BEEF SAMPLES WERE FREEZE-DRIED AT CONSTANT SURFACE TEMPERATURES RANGING 266 TO 203 K (-7 TO -70 DEG C), 243 TO 173 K (-30 TO -100 DEG C), RESPECTIVELY. RELATIONSHIPS BETWEEN TRANSPORT PROPERTIES AND CONTROLLING FACTORS SUCH AS TEMPERATURE, PRESSURE AND SOLUTE CONCENTRATION WERE OBTAINED.

Pressure control device

Abstract: A pressure responsive control device (10) having a pressure housing assembly (12) defining a pressure chamber (24), an actuable control (14) fixed to the housing assembly (12) and, a pressure transducer module (16) hermetically closing the pressure chamber (24). The module (16) includes a snap acting pressure responsive diaphragm (60) a di- aphragm control plate (62) hermetically bonded to the diaphragm outer periphery (66), and a support member (64) hermetically joined to and supporting the control plate (62) and hermetically joined to the housing assembly (12). The control plate (62) has a supporting region (70) rigidly supporting the diaphragm (60) and the diaphragm control regions (74,76) are yielded and deformed relative to the supporting region (70) to position the control regions for stressing the diaphragm (60) to determine the chamber pressure levels at which the diaphragm (60) moves.

Fuel supply device in lpg engine

Abstract: PURPOSE:To aim at stabilizing the air-fuel ratio of an LPG engine, by providing such an arrangement that the mechanism of the secondary pressure reducing chamber in a two stage pressure reducing type vaporizer is made identical to that of the primary pressure reducing chamber with the secondary chamber pressure having a positive pressure value which is lower than the pressure of the primary chamber, and the opening area of a fuel passage between the intake-air system and the secondary chamber is controlled by an actuator. CONSTITUTION:Fuel from a fuel tanks 21 is reduced in its pressure in a primary diaphragm chamber 23 in a primary pressure reducing valve 26, and then is further reduced in its pressure in a secondary chamber 34 in a secondary pressure reducing valve 37. The stage constant pressures of the secondary pressure reducing valve 37 is set by the urging force of a pressure adjusting spring 36 which presses a diaphragm 35, and is set at a value lower than a pressure set by a primary pressure adjusting spring 25. An actuator driven shut-off valve 46 and a fuel amount control valve 51 are disposed between the secondary diaphragm chamber 34 and the intake-air system, and are controlled by an electrical control device 77 in accordance with detected values from an air-flow sensor 68, and exhaust sensor 74, etc.