Showing papers on "Dynamic pressure published in 1996"

Generation of dynamic pressure pulses downstream of the bow shock by variations in the interplanetary magnetic field orientation

Abstract: One-dimensional resistive MHD and hybrid simulations are carried out to study the manner by which variations of the interplanetary magnetic field (IMF) direction generate dynamic pressure pulses in the magnetosheath. The reaction of the magnetosheath to the temporal IMF variation is modeled as the interaction between the bow shock (BS) and an interplanetary rotational discontinuity (RD), an Alfven wave pulse (AW), or an Alfven wave train. The resistive MHD simulation indicates that the arrival of an RD produces two time-dependent intermediate shocks (TDISs) and two slow shocks downstream of the bow shock, which propagate through the magnetosheath toward the Earth's magnetopause. An enhancement of plasma density is present throughout the TDISs and slow shocks. A plasma dynamic pressure pulse is formed in this region. In the hybrid simulation, the two TDISs are replaced by rotational discontinuities. For a bow shock with a shock normal angle θBn > 45°, the pulse in the dynamic pressure ρV2 causes the total pressure (P + B2/2μ0 + ρV2) in the magnetosheath to increases by about 0–100% of the background value. The strength of the pressure pulse increases with the field rotation angle across the incident rotational discontinuity, while it decreases with the Mach number or upstream plasma beta of the bow shock. The pressure pulse propagates toward the magnetopause with nearly a constant amplitude. On the other hand, the BS/AW interaction leads to the generation of Alfven waves downstream of the bow shock, and large-amplitude dynamic pressure pulses are generated in the downstream Alfven wave. Pressure pulses impinging on the magnetopause may produce magnetic impulse events (MIEs) observed in the high-latitude ionosphere.

Simulation of pressure pulses in the bow shock and magnetosheath driven by variations in interplanetary magnetic field direction

Abstract: Two-dimensional (2-D) hybrid simulations are carried out to study the effects of the variation in the interplanetary magnetic field (IMF) direction on the bow shock, magnetosheath, and magnetosphere. A curvilinear coordinate system is used in the simulation. The 2-D simulation is also compared with our one-dimensional simulation results. It is found that pressure pulses are generated as a result of the interaction between the bow shock (BS) and an interplanetary rotational discontinuity (RD). First, a structure consisting of a rotational discontinuity and two slow shocks are present downstream of the bow shock after the BS/RD interaction. The magnetic field and plasma density are anticorrelated in this structure. The dynamic pressure increases in the structure, leading to a pressure pulse in the magnetosheath. Second, a pressure pulse associated with reflected ions at the bow shock may be generated in the foreshock when the IMF changes its direction, especially when a local quasi-parallel bow shock becomes a quasi-perpendicular shock. The magnetic field, plasma density, and dynamic pressure are positively correlated in the upstream pressure pulse. This pressure pulse convects through and interacts with the bow shock, producing a pressure pulse in the downstream region. The downstream pressure pulses propagate to the magnetopause. The amplitude of the downstream pressure pulses can be up to 100% of the background magnetosheath value. It is suggested that the pressure pulses impinging on the magnetopause may lead to the magnetic impulse events observed in the high-latitude ionosphere.

A Pressure Projection Method for Nearly Incompressible Rubber Hyperelasticity, Part I: Theory

Abstract: A least-squares-based pressure projection method is proposed for the nonlinear analysis of nearly incompressible hyperelastic materials. The strain energy density function is separated into distortional and dilatational parts by the use of Penn's invariants such that the hydrostatic pressure is solely determined from the dilatational strain energy density. The hydrostatic pressure and hydrostatic pressure increment calculated from displacements are projected onto appropriate pressure fields through the least-squares method. The method is applicable to lower and higher order elements and the projection procedures can be implemented into the displacement based nonlinear finite element program. By the use of certain pressure interpolation functions and reduced integration rules in the pressure projection equations, this method can be degenerated to a nonlinear version of the selective reduced integration method.

Head slider and recording-and-reproducing apparatus

Abstract: A head slider supporting a read/write head for recording and reproducing information is disposed above a disk, i.e., an information recording medium. The head slider has on its surface facing the disk at least two transversely elongate dynamic pressure generating parts formed with their longer sides extended substantially perpendicularly to the rotating direction of the disk and arranged one behind the other in the rotating direction. The front dynamic pressure generating part is provided with a land of a length in the rotating direction of the disk greater than 10% and smaller than 50%. The land protrudes toward the disk and has a shoulder.

High-latitude ground-based response to sudden changes in solar wind dynamic pressure

Abstract: Sudden changes in the solar wind dynamic pressure have been linked, both theoretically and observationally, to the formation of a number of transient ionospheric phenomena. Still, the precise role that these pressure changes play in the formation of these phenomena remains uncertain. By using a combination of ground-based magnetic measurements from arrays of magnetometers located in Greenland and IMP 8 satellite measurements of the solar wind velocity and density, we have been able to better study the effect that pressure changes have on the high-latitude ionosphere. Our study is based on approximately 2500 hours of solar wind plasma data collected during 1991 and 1992 by the IMP 8 satellite and focuses on step changes of |Δp | > 2 nPa occurring on a timescale of Δt < 15 min. We have found that the ground response does not consistently conform to existing theoretical models of field-aligned currents generated by changes in dynamic pressure. We also do not find any explicit dependence on interplanetary magnetic field orientation. These results lead us to believe that the nature of the ground response is due to a more complicated combination of external controls.

Fluid dynamic pressure bearing and motor and magnetic disk apparatus using fluid dynamic pressure bearing

Abstract: A fluid dynamic pressure bearing has a shaft member, a sleeve member which is relatively rotatable to this shaft member and radial and thrust fluid dynamic pressure bearings. A lubricating oil retaining channel is provided to retain lubricating oil by the capillarity, a part of the retaining channel is open to the atmosphere and the other part is communicated with the fluid dynamic pressure bearings. The retaining channel can be formed on the shaft member. Further, a fluid dynamic pressure bearing in such the construction is favorably used in a motor and a disk driving apparatus.

Dynamic pressure fluid bearing device

Abstract: PROBLEM TO BE SOLVED: To provide a dynamic pressure fluid bearing device to effect distribution and holding of lubrication fluid to a pair of radial dynamic pressure grooves and a pair of thrust dynamic pressure groove as desired and perform stable use for a long period hereby. SOLUTION: A dynamic pressure fluid bearing device comprises a shaft member 20 having a shaft part 24 and a disc-form flange part 26; a sleeve member 22 sleeve-fitted-in the shaft part 24 and surrounding the flange part 26 and rotatable around the shaft member 20; and lubrication fluid with which a gap between the sleeve member 22 and the shaft member 20 is filled. A pair of radial dynamic pressure grooves are formed in the shaft part 24 of the shaft member 20, a pair of thrust dynamic pressure grooves are formed in the two surfaces of the flange part 26 of the shaft member 20. A fluid regulating means to substantially block fluid of lubrication fluid by residing air bubbles to reduce an amount of lubrication fluid is arranged between the radial dynamic pressure groove and the thrust dynamic pressure groove.

Dynamic wind pressure testing device for building side wall

Abstract: PURPOSE: To perform a test in a condition close to a natural phenomenon by applying dynamic wind pressure having wind speed in addition to a static wind load. CONSTITUTION: A dynamic wind pressure testing device is provided with wind load loading devices 4, 5, 6 and 10 capable of adjusting pressure to apply a static wind load to a pressure chamber 2 on which a specimen 1 is installed and dynamic pressure testing devices 12, 13, 14, 17 and 18 capable of applying dynamic wind pressure by a blower 12 of a system separate from the pressure chamber 2 from a blowoff port 14 on the tip of a flexible air pipe 13 at an optional angle to an optional place of the specimen in the pressure chamber 2.

Motor having dynamic pressure bearing device

Abstract: A motor having a dynamic pressure bearing device equipped with a rotor having a driving coil or a driving magnet, and a stator having the other of the driving coil or the driving magnet, the dynamic pressure bearing device comprising a shaft fixed to the rotor or the stator and having a dynamic pressure surface on its outer surface, a bearing body fixed to the other of the rotor or stator and having a dynamic pressure surface on its inner surface which is positioned to circumferentially confront the outer surface of the shaft body, a dynamic pressure generating groove formed on at least one side of both the dynamic pressure surfaces, and a lubricating fluid in which magnetic particles are dispersed in a base oil solvent containing an amine anti-gelling agent interposed between both of the dynamic pressure surfaces.

The shape and field of the magnetopause as determined from pressure balance

Abstract: This article presents a theoretical study of the dependence of the magnetopause shape and field on the dynamic pressure of the solar wind. The magnetopause surface (assumed to be axisymmetric) is determined by requiring the plasma pressure outside, estimated by the “Newtonian approximation,” to be balanced by the magnetic pressure inside. The magnetic field inside is given by the sum of (1) the Earth's internal field, (2) the field from various magnetospheric current systems (cross-tail current, ring current, etc.) as given by an empirical model, and (3) the field due to magnetopause currents. The magnetopause field is a function of the magnetopause shape and is updated each time this shape is adjusted toward pressure balance. In previous studies of this kind, only dipole and magnetopause fields were incorporated. This is the first three-dimensional solution of the problem to include the cross-tail current and thus to obtain a realistic magnetotail configuration. The results of this study are twofold. First, the shape of the magnetopause surface is computed under a variety of conditions. The resulting shapes are compared with fits to observed magnetopause crossings, and the scaling of magnetopause position on solar wind dynamic pressure is determined. Second, the model that results can be viewed as an improved version of the empirical model that was used as input, in that the magnetic field in the vicinity of the magnetopause (where empirical models have less guidance from data) is made more realistic.

Measurements in the Dynamic Pressure Field of the Volute of a Centrifugal Pump

Abstract: This paper presents an experimental investigation into the dynamic pressure field existing in the volute of an industrial centrifugal pump in order to characterize the interaction phenomena between impeller and volute. For that purpose, pressure signals were obtained simultaneously at different points of the volute casing by means of two miniature fast-response pressure transducers. Particular attention was paid to the pressure fluctuations at the passing blade frequency, regarding both amplitude and phase delay relative to a reference point. The analysis of the dependence of the pressure fluctuations on both flow-rate and position along the volute clearly indicates the leading role played by the tongue in the impeller-volute interaction and the increase of the amplitude of the dynamic forces in off-design conditions.

Pressure sensor for vehicle door

Abstract: The sensor dynamically measures force in the millisecond region. The sensor measures the sudden increase in pressure deltap relative to the previous absolute pressure po. The ratio deltap/po is needed because the measured signal delta p is approximately proportional to the absolute pressure po. A lower threshold frequency is determined. The measuring region only needs to match the dynamic pressure changes because pressure equilibrium occurs over time. The sensor includes a diaphragm.

Pressure measuring sensor and apparatus having a seal between a housing and a pressure measuring cell

Abstract: The invention relates to pressure measurement apparatuses and pressure or force measurement devices for static or dynamic pressure measurement, in particular for high pressures or forces, whose housing contains among other things, a pressure or force measuring cell, e.g. a piezoresistive or capacitive measuring cell. In devices like this, service life and chemical resistance are problematic. The pressure measurement device according to the invention is essentially comprised of a housing (2), a seal (4) between the pressure medium and the inner chamber (2d) of the housing (2), a pressure measuring cell (3), whose first main face (3e) is exposed to the pressure medium and which has a deflection when pressure loaded, which deflection leads to a relative movement between pressure measuring cell (3) and housing (2) in the region of the seal (4). In the region of the seal (4), the housing (2) is embodied so that it has spring-elastic properties. The pressure measurement apparatus according to the invention is comprised of a flange (7) with a conical sealing rib (7b) in the through opening (7f) and a pressure measurement device (9) with a housing (2) that is rotationally symmetrical in the region of the flange (7). The sealing rib (7b) is embodied as an elastic sealing rib.

Exhaust device for static pressure supercharging type internal combustion engine

Abstract: PURPOSE: To reduce fuel specific consumption by enhancing a utilization factor of exhaust energy in the whole operation area of a static pressure supercharging type internal combustion engine CONSTITUTION: The inside of an exhaust pipe 30 is partitioned into an exhaust gas chamber 31 and a pressure gas chamber 32 by a flexible film 11 At low load time, a regulating valve 13 is opened, and pressure gas is introduced into the pressure gas chamber 32, and the flexible film 11 is bent, and the volume of the exhaust gas chamber 31 is reduced, and dynamic pressure energy is increased At high load time, the pressure gas in the pressure gas chamber 32 is discharged, and the volume of the exhaust gas chamber 31 is made large, and static pressure energy is increased

Dynamic pressure bearing structure of small-sized motor

Abstract: PROBLEM TO BE SOLVED: To sufficiently supply oil to dynamic pressure generating grooves, so as to achieve the long life, by devising the arrangement of the dynamic pressure generating grooves, exhibiting the equal dynamic pressure functions in both normal and reversal rotations, and making an oil reservoir face a part of the dynamic pressure generating grooves. SOLUTION: A sleeve bearing 4 is pressed in a bearing holder 1a. In a shaft 5, many dynamic pressure generating grooves 5a, 5b formed into V and reversal V shapes in the radial direction are formed on the upper and lower parts of the sleeve bearing 4, and the whole is symmetric into a W shape with respect to the axial direction. Therefore, fluid (oil) of the dynamic pressure generating grooves 5a, 5b is allowed to flow to the opposite direction to a rotary shaft and functions as dynamic pressure in both normal and reversal rotations. At this time, one of respective dynamic pressure generating grooves 5a, 5b functions as dynamic pressure, the other one functions as an oil reservoir. COPYRIGHT: (C)1997,JPO

Brake control device

Abstract: PURPOSE: To invariably set the relation between the leg power, stroke, and deceleration to a proper relation or a desired optional relation by properly selecting the relation between a dynamic piston and a push rod. CONSTITUTION: The action quantity of a brake pedal 1 is detected by a sensor 2, a pressure regulating valve 4 is operated by the control command of an electronic control unit 3 based on the signal, the liaison with an auxiliary power hydraulic source 5 is adjusted, and the output pressure is controlled. When the dynamic pressure is fed to a booster unit 6, static pressure is generated in a static pressure chamber 10, operation reaction is applied to a pedal, and brake cylinders of front and rear wheels are braked by the dynamic pressure and static pressure.

Two phase flow model for the close-coupled atomization of metals

Abstract: The use of the nozzle tip static (aspiration) pressure during the flow of atomizing gas in close-coupled atomization geometries is employed widely to characterize the operable atomization regime, and, in some cases, the expected metal flow rate. A single phase flow calculation of metal flow rate using this pressure shows that the actual metal flow during atomization is not determined simply by the aspiration pressure. An improved model has been developed by applying a force balance and momentum conservation at the metal/gas interface. Combined with numerical and experimental gas flow data, the model provides a rational interpretation of the relationship between aspiration pressure and metal flow during atomization. The model also provides a physical basis for some of the commonly observed limits on the operating envelope of close-coupled atomizers and establishes a rational basis for non-metal fluid modeling of the atomization process. A variety of metal and water flow test data and local static and dynamic pressure measurements are presented which demonstrate the validity and limitations of the model.

Performance Characteristics of R-11, R-123 and R-245CA in Direct Drive Low Pressure Chillers

Abstract: R-11 was for many years the low pressure centrifugal refrigerant of choice. For environmental reasons, R-123 is now the low pressure centrifugal refrigerant of choice. Under current legislation, R-123 will be phased out by 2030. R-245ca has been proposed as a replacement for both R-11 and R-123 in new product and retrofit. This study compares measured performance of these three refrigerants in a 200 ton direct drive centrifugal chiller. The focus is on theoretical head requirements, measured onset of surge, adiabatic efficiency, impeller diameter effects and overall chiller performance. Conclusions include that R-245ca is not a suitable drop-in replacement for R-11 or R-123 due to surge concerns, but that it would be suitable in new product if the cost, availability and flammability issues can be resolved favorably. INTRODUCTION Federal regulations ban the production of CFC-11 after January 1, 1996. Distribution of HCFC-123 will be limited to service applications after January 1, 2020 and eliminated from production on January 1, 2030. HFC-245ca has been identified as a potential replacement for CFC-11 in retrofit applications and for HCFC-123 in new chillers. This report compares these three refrigerants based on their properties and their measured performance in a centrifugal chiller. Centrifugal Compressors Centrifugal compressors are not positive displacement devices but rather momentum devices, essentially high pressure fans. They raise pressure by means of accelerating a gas to high speed and then converting velocity pressure to static pressure. At the upper limit of pressure rise capability, centrifugal compressors will enter surge and suffer from oscillating backflow at the impeller outlet, a noisy and inefficient operating point. The pressure rise capability of a centrifugal compressor is a function of a number of variables, only two of which are relevant here: impeller tip speed (expressed as impeller diameter since rotational speed is constant) and the properties of the refrigerant. In this study a three stage compressor designed for CFC-11 was tested, the focus being on how the refrigerant properties and impeller diameters affect the predicted and actual performance. Typical design conditions for a centrifugal compressor in water cooled air conditioning service are 40F (4.44C) saturated evaporator and 100F (37.77C) saturated condenser, a constant eOF (33.3C) lift. Table 1 below shows ideal cycle properties for three low pressure refrigerants to demonstrate the effect of the refrigerant.

Dynamic pressure bearing

Abstract: PURPOSE: To reduce the static electricity generated at sliding time while ensuring stable performance by forming a dynamic pressure bearing of sintered material with specified Young's modulus and a volumetric specific resistance value, to increase rigidity and to reduce deformation. CONSTITUTION: A bearing device comprises a shaft 1, dynamic pressure thrust bearing 2 and a sleeve 3, to rotate the sleeve 3 with the shaft 1 serving as the fixed axis. A herringbone-shaped groove 4a is formed in a surface of the shaft 1 mutually opposed to an internal periphery of the sleeve 3. The dynamic pressure thrust bearing 2 is formed of sintered material having 300GPa or higher Young's modulus and a 10 Ω.cm or less volumetric specific resistance value, to use a metal of stainless steel or the like in the shaft 1. Further, the sintered material is preferable mainly composed of Al2 O3 , to use Al2 O3 -TiC system ceramics containing 20wt.% or more TiC. In this way, a stable dynamic pressure characteristic is obtained by decreasing deflection, in a dynamic pressure bearing, and further since static electricity can be released, reliability can be improved.

Dynamic pressure bearing made of ceramics and manufacture thereof

Abstract: PURPOSE:To reduce a wear amount, improve the reliability and prolong the service life by forming a dynamic pressure bearing made of ceramics by using ceramics having a specified Young's modulus and average crystal particle size and specifying surface coarseness of the bottom of a dynamic pressure generating groove CONSTITUTION:A dynamic pressure bearing made of ceramic is formed of ceramics 1 having a Young's modulus of 300GPa and an average crystal particle size of 05mum or more and surface coarseness of the bottom of a dynamic pressure generating groove is set to 1mum or less When the Young's modulus is 300GPa or less, a dynamic pressure effect by the high-precise dynamic pressure generating groove 2 is not stably produced occasioned by deformation due to an applying load When the average crystal particle size is 05mum or less, the edge of the dynamic pressure generating groove 2 is formed in a too acute state and cutting wear of a mating material is increased When surface coarseness of the bottom of the dynamic pressure generating groove 2 exceeds 1mum, a holding force for a fluid film, such as lubricant, between a dynamic pressure bearing and a mating material is decreased, contact between the dynamic pressure bearing and the mating material is apt to make and wear is progresses High reliability and a lengthened life can be brought

Dynamic pressure bearing

Abstract: PURPOSE: To reduce abrasion of a slidingly movable mating member, enhance rigidity, and improve reliability by using ceramics having a specific Young's modulus as a constitutive member of a dynamic pressure bearing, and covering the surface with an amorphous hard carbon film. CONSTITUTION: The tip of a shaft used in a spindle motor or the like slidingly moves with a dynamic pressure thrust bearing 2 at start and stop time and low speed rotation time. At this time, the whole load of a rotary body is applied as a load to the tip of the shaft and the dynamic pressure thrust bearing 2. Therefore, the dynamic pressure thrust bearing 2 has a groove 21 on a surface 24 of a ceramics body 22 having a Young's modulus not less than 300GPa, and this surface 24 is covered with an amorphous hard carbon film 23. Center line average roughness (Ra) of a surface of the ceramics body 22 is set in a range of 0.05 to 0.06m, and a thickness (t) of the amorphous hard carbon film 23 is set in a range of 0.3 to 1.5m. Therefore, abrasion of the dynamic pressure thrust bearing 2 itself and the shaft is reduced, and they can be excellently used over a long period of time.

Flow-rate measuring probe

Abstract: PURPOSE: To measure flow at a part having no curvature by disposing a plurality of static pressure taps in a direction different from dynamic pressure tap faced to flow direction in a probe body and connecting the respective static pressure taps to one input of differential transmitters and connecting the common dynamic pressure tap to the other input of the transmitter. CONSTITUTION: A common dynamic pressure taps 24 are disposed in cooling water flow direction in a periphery wall of a probe body and connect them with a dynamic pressure hole 26 and static pressure taps 30a-30c are disposed at right angle to water flow and they are connected with static pressure holes 32a-32c respectively. The static pressure holes 32a-32c are connected with first inputs 34a-34c of differential transmitters 36a-36c and second inputs 48a-48c are connected with the dynamic pressure hole 26. Whereby, the respective transmitters 36a-36c detect differential pressure which is proportional to square of size of flow of nuclear reactor cooling water and transmit this signal to a processor 62. The differential signal is converted into a flow signal which is proportional to the flow by the processor 62.

High-pressure gas wiping nozzle in hot dip coating line

Abstract: PURPOSE: To provide a high-pressure gas wiping nozzle which ejects gas free from a disturbance in dynamic pressure in the transverse direction of the gas wiping nozzle from a slit under a high pressure. CONSTITUTION: This high-pressure gas wiping nozzle for the hot dip coating line is constituted to introduce the gas flowing into a first pressure equalizing chamber 2 through flow regulating grooves 4, which are arranged zigzag in two upper and lower stages, and are formed to be in proximity to each other and to incline in a range of 0 deg.<θ<90 deg. from the axial direction of the slits, into a second pressure equalizing chamber 3 and to eject the gas from a slit 5 formed in front of the second pressure equalizing chamber with the excellent uniformity of the gas pressure.