Showing papers on "Dynamic pressure published in 2001"

Analysis of temperature and pressure fields in molten carbonate fuel cell stacks

Abstract: A mathematical model based on fluid dynamics and heat-transfer theories was applied to predict gas dynamic pressure and temperature distribution in a coflow molten carbonate fuel cell (MCFC) stack. The mass balance was simplified to obtain exact solutions with an assumption of uniform current density in the cell. The simulations were compared with data from a pilot-scale MCFC stack. The effect of internal geometry of gas channels was simulated to accurately predict the gas-pressure drop. A close prediction of pressure drop was possible from a partially blocked gas channel model that approximates the significant flow resistance. The effect of external boundary conditions on stack temperature profile was also analyzed. Temperatures were accurately predicted from a boundary heat conduction model with a reasonable assumption of wet seal temperatures. The 2-D boundary conditions could be extended to 3-D simulations to predict temperature distribution with the same accuracy. The model was applied to see the effect of scale-up on the maximum temperature rise and average cell potential. The result verified a significant effect of cell size on the maximum stack temperature.

Construction and Validation of a Dense Gas Shock Tube

Abstract: Results from initial tests of a shock tube designed to verify the nonclassical dynamics of Bethe-Zel'dovich-Thompson (BZT) fluids are presented. These tests employed nitrogen at pressures and temperatures required for shock-tube initial conditions that will produce nonclassical phenomena in a BZT fluid. A single-diaphragm, stainless steel shock tube is enclosed in a resistance-heated tube furnace. Each of the 16 segments of the furnace is controlled by a proportional integral differential loop to sustain a uniform temperature along the tube. Water-cooled static and dynamic pressure transducers and thermocouples are used to monitor the static initial conditions and the dynamic wave field. The nitrogen test cases are compared to the ideal gas Riemann problem. The pressure differential of the incident expansion wave matches the theoretical magnitude to within 2%, whereas the average wave speed agrees within 7%

Combustion chamber dynamic pressure transducer tee probe holder and related method

Abstract: A dynamic pressure probe includes a holder body having a first passage therein adapted to receive a pressure signal, a pressure sensor including at least a pressure sensing portion located within a sleeve seated within a pressure sensor housing portion, the sleeve engaged with a wall of the housing portion; the pressure sensor including a diaphragm having one face exposed to a pressure chamber within the sleeve between the pressure sensor and the wall; wherein an aperture in the wall of the housing connects the pressure chamber to the first passage; and wherein the first passage continues axially beyond the aperture in a flow direction an acoustic damping coil wound about a vertical axis.

A procedure for the treatment of the velocity-pressure coupling problem in incompressible fluid flow

Abstract: A new block implicit procedure (BID) is introduced which utilizes a simple incomplete decomposition of the matrix resulting from the discretization of the momentum and mass conservation equations for incompressible fluid flow problems. In contrast to the conventional methods, the new method is not of the segregated type, and does not require an explicit equation for pressure. The complete, coupled block system is solved in its primitive form. In this way, mass and momentum conservation are satisfied simultaneously at all grid points, while pressure is calculated implicitly. Only a couple of overall iterations are required for the treatment of the nonlinearities of the problem. Tests show that the new procedure converges fast for any E value (in an E-factor formulation), and therefore virtually the E-factor formulation is not necessary.

Dynamic pressure bearing spindle motor

Abstract: PROBLEM TO BE SOLVED: To reduce the number of constituting components and provide a fluid dynamic pressure bearing excellent in deflection, in a spindle motor having an H-shaped dynamic pressure bearing SOLUTION: In the spindle motor having the H-shaped dynamic pressure bearing, the H-shaped fluid dynamic pressure bearing is constituted of a sleeve 4, a shaft 1 having a flange 3 wherein the flange 3 is formed in the lower end, a rotor frame 6 which is fixed by forcible insertion in an upper end of the shaft 1, lubricating oil with which fine gaps between the constituting members are filled, a radial dynamic pressure generating trench G1 which is formed on an outer peripheral surface of the shaft 1 constituting a radial gap, a first thrust dynamic pressure generating trench G2 which is formed on an upper end surface of the sleeve 4 which forms an upper thrust gap to a lower surface of the rotor frame 6, and a second thrust dynamic pressure generating trench G2 which is formed on a lower end surface of the sleeve 4 which forms a lower thrust gap to an upper surface of the flange 3

Tester for pressure sensors

Abstract: The invention relates to a tester for pressure sensors in the wafer compound or isolated pressure sensors having a recess for the pressure sensors as well as means for electrical contacting of the electrical connections of at least one of the pressure sensors. The invention is intended to make it possible to test pressure sensors still in a wafer compound for their function. According to the invention, a pressure head is provided which has an interior space open on one side, the open face of which is capable of being mounted on the pressure sensor in such a way that the interior space is tightly sealed by the latter. In this way a static or dynamic pressure of specified amount and duration can be exerted on the sensor element at least so that the sensor element is moved out of its resting position. At the same time, the electrical connections of the selected pressure sensor are connected with an electrical evaluation unit.

Design, fabrication, and testing of scaled wind tunnel model for the Smart Wing Phase 2 program

Abstract: Building on the research performed during the DARPA / AFRL Smart Wing Phase 1 program to improve vehicle aerodynamic efficiency using control surfaces actuated by smart materials, the goal of the Phase 2, Test 1 effort was to increase the size of the model and the control surfaces and conduct wind tunnel tests at higher dynamic pressure and Mach number. This paper describes 1) model design for required safety and increased aileron effectiveness at high dynamic pressure; 2) model instrumentation; 3) SMA actuator control system design and implementation and 4) wind tunnel test results. Pictured below (Figure 1) is the model installed in the NASA Langley's Transonic Dynamic Tunnel (TDT).

Flow transients in the postnoon ionosphere: The role of solar wind dynamic pressure

Abstract: Super Dual Auroral Radar Network (SuperDARN) HF radar, magnetometer, and satellite data are used to study ionospheric convection flow bursts in the sunward return flow in the 1200–1500 MLT auroral region. A comparison between the latitudinal position of the flow bursts and the position of the open/closed field line boundary shows that the sunward bursts occur on closed field lines. The bursts occur simultaneously with poleward motions of the convection reversal boundary. Decreases in the solar wind dynamic pressure are shown to correlate well with the flow bursts. Comparison of radar arid magnetometer data shows that these observations can be explained in terms of the global current model proposed for sudden expansions of the rnagnetosphere [Araki and Nagano, 1988]. The sunward flow bursts are shown to be consistent with the high-latitude dusk to dawn electric field predicted by the model during pressure decreases.

Linear fluid dynamic channel upstream pumping machine seal

Abstract: The utility model relates to a novel mechanical sealing method using a single-row fluid dynamic pressure groove upstream pumping way. A sealing movable ring or a stationary ring is provided with a single-row fluid dynamic pressure groove with a specific groove shape and the middle of the fluid dynamic pressure groove is provided with annular groove to form upstream and downstream pumping section dynamic pressure grooves, so that a non-contact type mechanical seal with fluid lubrication is obtained.

Development of Fiber Optic Aerodynamic Sensors for High Reynolds Number Supersonic Flows

Abstract: Recent developments in advanced system and process controls have increased the need for sensors capable of acquiring measurements in extreme environments with accompanying high temperatures and heat fluxes, causing temperature-induced errors in electrical-based instrumentation. In an effort to improve such measurements, instrumentation is moving to micromachining and fiber optics, which when combined will greatly improve accuracy, repeatability, and resolution while reducing sensitivity to electromagnetic interference (EMI) and temperature. Interferometric-based, fiber optic pressure and skin friction sensors were developed for measurements in these environments. They were tested in laminar, incompressible flow, and supersonic flow up to Mach 3.0, in which the sensors operated with varying success. The accurate operation of these sensors was found to be tied to the flow conditions and the fiber optic, signalprocessing system, specifically a broadband interferometric system. A high correlation was found to exist between the energy of the flow, either through its dynamic pressure or through external disturbances such as shocks or separation, and the noise in the signals for the sensors in these flows. This correlation imposes a limit on the accurate operation of these sensor systems, which has been thoroughly explored, as have the necessary improvements of the systems for future development.

Pressure housing for in-water pressure based systems

Abstract: The present invention relates to a pressure housing for in-water pressure based systems and to a method for improving the life of the transducers and electronics of underwater systems by maintaining a humidity-free and clean environment around them by avoiding the entry of humidity, dust, or any suspended particles in the air during occasional data offloading and battery replacement in a humid and dust-laden field station; improving the ease of closing and opening of the pressure housing by the use of a novel arrangement thereby avoiding the use of conventionally employed cumbersome protruding and corrosion-prone locking devices such as screws, bolts, or clamps; and implementing reliable transmission of water pressure to the pressure port of the transducer, simultaneously minimizing the errors arising from dynamic pressure effects, preventing its chemical corrosion from saline water, and arresting bio-fouling in the vicinity of the pressure inlet.

Pressure probe designs for dynamic pressure measurements in a supersonic flow field

Abstract: A series of dynamic flow field pressure probes were developed for use in large-scale supersonic wind tunnels at NASA Glenn Research Center. These flow field probes include pitot, static, and five-hole conical pressure probes that are capable of capturing fast acting flow field pressure transients that occur on a millisecond time scale. The pitot and static probes can be used to determine local Mach number time histories during a transient event. The five-hole conical pressure probes are used primarily to determine local flow angularity, but can also determine local Mach number. These probes were designed, developed, and tested at the NASA Glenn Research Center. They were also used in a 10- by 10-foot supersonic wind tunnel test program where they successfully acquired flow field pressure data in the vicinity of a propulsion system during an engine compressor stall and inlet unstart transient event. Details of the design, development, and subsequent use of these probes are discussed.

Dynamic pressure bearing motor

Abstract: PROBLEM TO BE SOLVED: To provide a dynamic pressure bearing motor which can easily fill the lubricating oil of a dynamic pressure bearing means and in a short time, by the mass production property into consideration. SOLUTION: This dynamic pressure bearing motor is provided with a fixing member 102, a rotor hub 104, and a dynamic pressure bearing means 106 placed between them. The dynamic pressure bearing means 106 has a shaft member 120, a bearing sleeve body 122, a pair of radial dynamic pressure fluid bearing means 150 and 152, and a pair of thrust dynamic pressure fluid bearing means 158 and 160, a shaft hole 176 is formed to the shaft member 120, a large inner diameter part 19 is provided at one end part of the shaft hole 176, the lubricating fluid of the radial and thrust dynamic pressure fluid bearing means 152, 158, and 160 is poured to the large inner diameter part 190 through the shaft hole 176, and the poured lubricating oil is permeated by the capillary phenomenon, so as to be filled to those dynamic pressure fluid bearing means.

Fluid bearing device and grinding wheel spindle device for grinder using fluid bearing device

Abstract: PROBLEM TO BE SOLVED: To prevent a bearing from heating while holding the rigidity of the bearing in a fluid bearing device 10 journaling a rotary shaft 20 by a fluid pressure. SOLUTION: A bearing member 2 of this fluid bearing device 10 is provided with a U-shaped static pressure pocket 4 generating a dynamic pressure in the direction acting a loading force to the rotary shaft 20 and requiring the high rigidity and rectangular static pressure pockets 6 in the other directions. The U-shaped static pocket 4 can hold the necessary rigidity and support the loading force acting on the rotary shaft 20. On the other hand, the rectangular static pressure pockets 6 have large areas so that chances of the rotary shaft 20 being in contact with the cooled lubricating oil are increased so as to prevent it from heating.

Dynamic pressure bearing apparatus

Abstract: To provide a dynamic pressure bearing apparatus having high performance and excellent stability without hindering operations of appliances due to a leaked oil, the dynamic pressure bearing apparatus of the present invention comprises; a rotating shaft inclined in a predetermined direction from a vertical direction; a sleeve rotatably supporting the rotating shaft; an operating fluid for generating a dynamic pressure, the operating fluid being filled in a gap formed between the sleeve and the rotating shaft; and capturing means for capturing the operating fluid leaked from the gap, the capturing means being disposed on an outside surface of the sleeve in the predetermined direction.

Theoretical study of a molten carbonate fuel cell stack for pressurized operation

Abstract: A mathematical stack model of a molten carbonate fuel cell was numerically solved for temperature, gas dynamic pressure, and cell performance. The model assumed a steady state, constant load operation for a co-flow stack with an external reformer. The numerical computation was done for a two-dimensional domain with a real size of cell specifications. The effect of two stack operation variables, gas utilization and system pressure, was thoroughly analysed. The computation results were demonstrated in the form of flow fields, temperature contours, axial profiles, and plots of characteristic values. Our analysis began with an underlying fact that a high cathode gas flow is necessary for stack temperature control. The analysis result verified the effect of stack cooling by the cathode gas, and showed various aspects of stack operation and performance under pressurization. The pressurization effect is most significant in a moderate pressure range of 1–5 atm. The gas dynamic pressure, as it inevitably increases at a high gas flow rate, is regulated by pressurization. All the pressurization effects can generally be represented using a dimensionless parameter, named a pressurization factor. The relation between gas dynamic pressure and total system pressure was clarified from the related flow equations. Copyright © 2001 John Wiley & Sons, Ltd.

Dynamic pressure measurements using silicon carbide transducers

Abstract: Pressure sensors capable of operating at higher temperatures have long been sought for testing of aircraft engines, since each improvement in sensor durability opens new areas of the engine to the straightforward measurement of rapidly varying pressures. A silicon carbide pressure sensor has been developed which can operate at 500/spl deg/C, a temperature at which the mechanical properties of silicon, the most commonly used pressure sensor material, are severely degraded. The prototype SiC pressure transducer was successfully tested on a gas turbine engine, thereby demonstrating its ability to survive the hostile engine environment. Testing in a shock tube showed the packaged sensor to have a natural frequency of 30 kHz, which is adequate for many dynamic pressure measurement applications. It is expected that the frequency response could be increased by a simple modification of the package to reduce the setback of the SiC die.

Lubricant fluid for dynamic pressure fluid bearing

Abstract: PROBLEM TO BE SOLVED: To provide a lubricant fluid for a dynamic pressure fluid bearing, enabling a high speed rotation of >=10,000 rpm, and hardly causing a problem such as corrosion of the shaft. SOLUTION: This lubricant fluid for a dynamic pressure fluid bearing is obtained by mixing 5-25 pts.wt. poloefin oil with 100 pts.wt. polyol ester oil, and has 8-12 cP viscosity at 40 deg.C.

Factors controlling the diamagnetic pressure in the polar cusp

Abstract: The solar wind has direct access to the polar cusps although the plasma may be processed first by reconnection. The energy density of the polar cusp plasma is expected to be controlled by the component of the unshocked solar wind dynamic pressure along the normal to the cusp/magnetosheath interface. The factors controlling this angle are the local time of the observation and the dipole tilt angle. We use Polar observations of the magnetic field and plasma to identify the polar cusp, and the change in magnetic pressure in the cusp to calculate the peak diamagnetic pressure of the plasma. As expected this pressure is directly proportional to the solar wind dynamic pressure in quantitative agreement with expectations. When the dipole tilts more toward the Sun, the angle between the solar wind flow and the magnetopause normal is smaller, and the pressure is higher, and when it tilts away from the Sun, the pressure is less. For large tilts away from the Sun, for local times far away from noon and for low solar wind dynamic pressure the diamagnetic depression marking the polar cusp is too weak to be resolved by the magnetometer.

The angle of attack

Abstract: The author considers the angle-of-attack compensator and the static pressure sensor. A true angle of attack is required to correct static and dynamic pressures. Static pressure is necessary to calculate altitude. Dynamic pressure is necessary to calculate speed. Sensing the angle of attack is crucial to correcting all sensed parameters. As an aircraft flies at an angle of attack, static pressure is increased by a total pressure component. Similarly, total pressure can be reduced. Both pressures require correction according to the angle of attack.

Double row fluid dynamic pressure groove self lubrication non-contact type mechanical seal

Abstract: The utility model relates to a novel fluid dynamic pressure groove self-lubrication non-contact type mechanical sealing device. The main structure of the utility model is that a sealing moving ring or a stationary ring is provided with two rows of specific groove-shaped fluid dynamic pressure grooves and a downstream side formed by the two rows of dynamic pressure grooves is provided with an annular grooves, etc. Thus, the utility model has favorable sealing performance, excellent self-lubrication function, better operating stability and reliability, favorable solid particle resistant performance and trolley starting and stopping function.

Ceramic dynamic pressure bearing, motor provided with the same, hard disk device, and polygon scanner

Abstract: PROBLEM TO BE SOLVED: To provide a ceramic dynamic pressure bearing capable of preventing the occurrence of wear when starting and stopping and realizing favorable rotation of the dynamic pressure bearing. SOLUTION: A dynamic pressure clearance 17 is formed between a first member 14 and a second member 15 rotating relatively around a predetermined rotary axial line, and a fluid dynamic pressure is generated in the dynamic pressure clearance 17 in accordance with the relative rotation of the first member 14 and the second member 15. A part including a surface (dynamic pressure clearance forming face) facing the dynamic pressure clearance 17 is constituted by at least ceramic in at least either of the first member 14 and the second member 15, and an average dimension of a surface hole existing on the dynamic pressure clearance forming face made of ceramic is adjusted to 2 to 20 μm. Furthermore, at least any dynamic pressure clearance forming face of the first member 14 and the second member 15 is covered with a hard carbon film DR having an average film thickness smaller than the average dimension of the surface hole and made of amorphous carbon mainly.

Gas pipe pressure measuring device

Abstract: PROBLEM TO BE SOLVED: To provide a device detecting a pressure in a gas meter inflow side during operating the gas meter in spite of being installed in an outflow side pipe of the gas meter. SOLUTION: Pitot tube formed of a static pressure tube 2 and a dynamic pressure tube 3 is provided in a gas pipe 1, or the outflow pipe of the gas meter and its differential pressure is measured by a differential pressure sensor 4. A front rectification grid 7 and a rear rectification grid 8 are provided in front and back of the Pitot tube. The differential pressure signal is converted into a digital signal by a communication controller 5 and transmitted to a centralized control room via a telephone line or PHS. A computer in the centralized control room receiving the signal from a snap device 6 applies the received differential signal to a calibration curve to calculate the flow rate and then calculates the pressure loss in the gas meter based thereto. The computer adds the pressure loss in the gas meter to the received pressure signal to find the pressure in the gas meter inlet.