Showing papers on "Dynamic pressure published in 1989"

Dynamic pressure method for kla measurement in large-scale bioreactors.

Abstract: A dynamic method is proposed for kla measurement in aerated and agitated reactors, in which a change in the total pressure in the reactor by approximately 20% leads to a simultaneous change in the oxygen concentration in all the bubbles in the dispersion. This procedure suppresses the influence of nonideal mixing of the gas phase on the kla value. Other dynamic methods so far used do not possess this advantage. They are based on a step change in oxygen concentration in the entering gas, where the interfacial nitrogen transport and the finite rate of the concentration change propagation into the individual bubbles in the dispersion can cause an error in the reported kla values of more than hundreds of percent. The reliability of the pressure method is tested by comparison both with the standard dynamic method, in which pure oxygen is absorbed in a liquid from which all other gas components were previously removed, and with the steady-state sulphite method. The signal of the oxygen probe used in the experiments must be independent of the pressure. A test for this in dependence is described. The pressure method is also suitable for large-scale reactors since the necessary pressure changes are sufficiently small and, morever, air can be used.

Apparatus and process for determining systolic blood pressure, diastolic blood pressure, mean arterial blood pressure, pulse rate, pulse wave shape, respiratory pattern, and respiratory rate

Abstract: An apparatus and process for automatically measuring systolic, diastolic and mean arterial blood pressure. Two cuffs, one located closer to the heart (proximal) than the second (distal), are provided. Each cuff is attached to a small manifold which has three ports. One port is connected to the cuff, one port is connected to a pressure sensor, and the last port is connected to a valve to a high pressure air source. Throughout blood pressure monitoring, a constant mass of air is maintained within the cuff by inflating the cuff and closing the cuff valve. The sensors are connected to a microcomputer so that the static pressure component and the dynamic pressure component of cuff pressure can be stored and plotted. Mean arterial pressure is read from both distal and proximal cuff sensors. Diastolic blood pressure is determined by recording the proximal static cuff pressure at which a maximum dynamic distal amplitude is observed. Systolic blood pressure is determined by recording the proximal static pressure at which a minimum dynamic distal amplitude is observed.

Method for experimental determination of flutter speed by parameter identification

Abstract: A method for flight flutter testing is proposed which enables one to determine the flutter dynamic pressure from flights flown far below the flutter dynamic pressure. The method is based on the identification of the coefficients of the equations of motion at low dynamic pressures, followed by the solution of these equations to compute the flutter dynamic pressure. The initial results of simulated data reported in the present work indicate that the method can accurately predict the flutter dynamic pressure, as described. If no insurmountable difficulties arise in the implementation of this method, it may significantly improve the procedures for flight flutter testing.

Coaxial plasma accelerator with compressor coil and radial gas injection

Abstract: A recently modified coaxial plasma accelerator with compressor coil is described. This plasma dynamic launcher is capable of accelerating particles in the mass range of 10/sup -10/ to 10/sup -4/ g to velocities up to 20 km/s and probably even higher. The test range, its energy storage system, its operating parameters, and the various electric and photographic diagnostic techniques are described. In addition, a description is given of a novel gas injection system and its diagnostics and operating characteristics. A recently developed dynamic pressure measurement technique which is used to determine the dynamic plasma pressure inside the accelerator is discussed. Transient pressures of the order of 10 kbar can be measured in an environment of currents of up to 50 kA and magnetic fields of up to 1 T, the time scale being of the order of 10 mu s. >

Closed-form approach to rocket-vehicles aeroelastic divergence

Abstract: The aeroelastic divergence of a class of rocket-vehicl e configurations is studied in closed form. The class is characterized by having the lateral aerodynamic loads distributed mainly about the vehicle nose and tail. The purpose is to demonstrate the feasibility of a closed-form approach and its usefulness in pinpointing the essentials of, and lending insight into, the phenomenon. The equations of motion are first derived; then, a dynamic frequency-domain stability analysis is carried out, yielding simple formulae for the divergence dynamic pressure and generalized static margin. The predivergence short-period roots behavior is also found. Expressions are derived for the steady-state angle of attack, accelerations, aerodynamic loads, and elastic bending of a perfectly aligned vehicle at divergence and of a misaligned vehicle at predivergence . For application to actual cases, a method is developed by which actual aerodynamic distributions may be converted into a form admissible to the theory. Validity is confirmed by comparison of results with those of a more exact theory and with available experimental data.

Signal sensor insensitive to static pressure variations

Abstract: A signal sensor automatically compensates for the variations of the static pressure of the medium in which it is placed. The signal sensor comprises one or two assemblies each formed of a piezoelectric sensitive element applied against one face of a flexible plate. The other face of the plate is shielded from the variations of the dynamic pressure to be measured by a material absorbing the vibrations but fairly flexible so as to transmit any variation of the ambient static pressure. This material which may be a porous foam or a fibrous substance impregnated with liquid, fills a tubular apertured sleeve.

Wind Effect on Measured Atmospheric Pressure

Abstract: Wind generated Pressure inside buildings, normally referred to as “internal pressure” in engineering literature, has a profound effect on the atmospheric pressure measured with indoor barometers during severe storms. The magnitude of the internal pressure is proportional to the dynamic pressure (stagnation pressure) which in turn increases with the square of the wind speed. Normally, this pressure is negative, and it has a magnitude in the neighborhood of 50% of the stagnation pressure. Its value changes drastically when an opening such as a door or window is opened or broken in high winds. The internal pressure also fluctuates readily with the fluctuations of the external pressure when a large opening exists. Surface pressure measurements taken in severe storms may contain serious errors if this internal pressure effect is not corrected. The paper summarizes latest research findings on internal pressure reported in the literature, and explores their implications to meteorology—especially to the ...

Dynamic Wall Pressure Measurements

Abstract: The quest for information on the dynamics of wall pressure fluctuations has been motivated by two principle objectives. The first is to gain more fundamental understanding of the turbulent boundary layer, in particular, the mechanism by which it continually regenerates itself. The wall pressure measurement has the advantage of being, for the most part, non-invasive. On the other hand, it is a weighted integral of the velocity fluctuations in the boundary layer, hence, its picture of boundary layer activity must of necessity be somewhat diffuse. Pressure measurements have been combined with other measurements, in particular, fluctuating velocity and fluctuating wall shear stress. These have taken the form of long-time averages, such as in cross-correlation and cross-spectral density measurements. Short time conditional average measurements have also been taken wherein one or the other of the physical quantities has served as the trigger. A blend of the two techniques has been employed in measuring wall pressure fluctuations in the transition zone between laminar and turbulent flow. The pressure measurement is today an integral part of any serious experimental study of boundary layer dynamics.

Trajectory optimization and guidance law development for transatmospheric vehicles

Abstract: The problems of on-board trajectory optimization and real-time guidance law synthesis are addressed for an air-breathing, single-stage-to-orbit vehicle. The particular objective of fuel-optimal ascent is examined in the hypersonic regime using a simple vehicle model representative of the aerospace plane concept. This model includes a dual-mode propulsion system composed of SCRAMJET and rocket engines. An energy state approximation is applied to a four-state dynamic model for flight of a point mass in a vertical plane over a spherical non-rotating Earth. Optimal climb profiles for the unconstrained and dynamic pressure constrained cases result from further reduction in model order. An analytic switching condition is derived for optimal transition to rocket powered flight as orbital velocity is approached. Simple feedback guidance laws for both the unconstrained and dynamic pressure constrained cases are derived via a combination of singular perturbation and feedback linearization techniques. Lastly, the performance of the resulting nonlinear feedback guidance laws is presented in a numerical simulation of ascent to orbit.

Gas rotary machine using dynamic pressure gas bearing together with static pressure used

Abstract: PURPOSE:To prolong the life of a dynamic pressure gas bearing by introducing static pressure of a process gas to the bearing CONSTITUTION:A pair of thrust dynamic pressure gas bearings 12 are provided in the gaps between the two sides of a thrust runner 11 protruding near a compressor 1 and the mating inner surface 4b of a housing 4, while a pair of journal dynamic pressure gas bearings 13 are formed between the journal and the housing inner surface 4a of the outside surface A static pressure communication path consisting of a supply hole 14, hollow distribution chamber 15, and exhaust hole 16 is furnished in the bearing housing 4, and the static pressure of 8 process gas is introduced to the dynamic pressure gas bearings with the process gas as a pressure source Thereby the contact pressure between the rotor and bearing at the time of start and stop is reduced, which prolongs the life of the bearing

Dynamic Pressure Measurement Using Two-Frequency Ultrasound

Abstract: To perform non-invasive pressure measurement by ultrasound, we examined the acoustic characteristics of microcapsules which are dependent on the surrounding pressure The linear amplitude change of frequency spectrum by pressure was used to develop a fast pressure measurement method To determine the correspondence of the spectrum amplitude with pressure, we defined a twin frequency attenuation ratio (TAR) as a new pressure parameter measured by two-frequency ultrasound Dynamic change of pressure was experimentally detected by TAR, whose sensitivity for ultrasonic pressure measurement was thus indicated

Thrust vector control flap with a merging convex, concave inner contour, for jet aircraft and method for operating the same

Abstract: A thrust vector control for a jet engine is accomplished by controllable flaps which have an inner, jet flow facing contour with a double curvature. One curvature section is convex and extends between the leading edge of the flap and a transition point. The other curvature section is concave and extends between the transition point and the trailing edge of the flap. The flap or flaps are arranged downstream of the propulsion jet nozzle and are tilted into the jet stream as required for the vector control. A pressure sensor is arranged so as to measure or pick-up a pressure value, preferably near the trailing edge of the flap, which pressure value depends on the dynamic pressure head in that area. The respective pressure value is used in a closed loop control circuit for operating the tilting drive of the respective flap.

Fluctuating pressures measured beneath a high-temperature, turbulent boundary layer on a flat plate at Mach number of 5

Abstract: Fluctuating pressures were measured beneath a Mach 5, turbulent boundary layer on a flat plate with an array of piezoresistive sensors. The data were obtained with a digital signal acquisition system during a test run of 4 seconds. Data sampling rate was such that frequency analysis up to 62.5 kHz could be performed. To assess in situ frequency response of the sensors, a specially designed waveguide calibration system was employed to measure transfer functions of all sensors and related instrumentation. Pressure time histories were approximated well by a Gaussian prohibiting distribution. Pressure spectra were very repeatable over the array span of 76 mm. Total rms pressures ranged from 0.0017 to 0.0046 of the freestream dynamic pressure. Streamwise, space-time correlations exhibited expected decaying behavior of a turbulence generated pressure field. Average convection speed was 0.87 of freestream velocity. The trendless behavior with sensor separation indicated possible systematic errors.

On the dynamic response of pressure transmission lines in the research of helium-charged free piston Stirling engines

Abstract: The signal distortion inherent to pressure transmission lines in free-piston Stirling engine research is discussed. Based on results from classical analysis, guidelines are formulated to describe the dynamic response properties of a volume-terminated transmission tube for applications involving the helium-charged free-piston Stirling engines. The underdamped flow regime is described, the preliminary resonance frequency is derived, and the pressure phase and amplitude distortion are discussed. The scope and limitation of the dynamic response analysis are considered. >

A Comparison of Scramjet Engine Performances of Various Cycles

Abstract: Assuming an airframe-integrated hydrogen fueled scramjet engine, we compared the performances of engines of various engine cycles : an expander cycle, a staged combustion cycle, a coolant bleed cycle, and a gas generator cycle. Each engine was regeneratively cooled by liquid hydrogen. Effects of flight Mach number, flight dynamic pressure, and fuel injection to air dynamic pressure ratio were examined as related to the power balance of the propellant feed line. It follows that the system pressure of the closed loop cycle increases and the specific impulse of the open loop cycle decreases with increasing flight Mach number, flight dynamic pressure, or fuel injection to air dynamic pressure ratio, i.e., with increasing fuel injector manifold pressure. Of the four cycles, the coolant bleed cycle shows well balanced engine performance, keeping the system pressure within a reasonable range.

Dynamic pressure fluid bearing

Abstract: PURPOSE:To prevent fluid from flowing out, thereby maintain high performance for a long time by providing a film the contact angle of which formed in 5min after fluid used for producing dynamic pressure has been dripped is equal to or more than 10 deg. for the end section of a micro gap wherein fluid exists to be used for producing dynamic pressure. CONSTITUTION:In a dynamic pressure fluid bearing composed of a shaft 2 including a housing 1 and a hallingbone groove 5, and a thrust bearing 3, silicon oil is used as fluid for producing dynamic pressure so that the end section of the micro gap of a section producing dynamic pressure is coated with fluid wherein poly fluoro ether containing isocyanate group is uniformly dispersed into high fluoride organic solvent such as flon R113. After coating has been over, solvent is evaporated so as to obtain a film 4. The contact angle of silicon oil is about 50 deg. against the face of the film 4, the provision of the film 4 enables the duration of current bearing function to be increased by a factor of about 4.

A study of the J = 2 collective modes of superfluid 3 He-B using a dynamic pressure sweeping technique

Abstract: We report measurements of the positions of theJ=2 collective modes in zero field using a new technique involving alternate pressure and temperature sweeps. Extensive measurements over a wide range of pressure, temperature, and frequency have been performed and are compared with previous data.

System to avoid icing in the discharge piping of a pressure relief valve

Abstract: Apparatus for deicing the discharge gas from a safety relief valve includes a high pressure probe and an injection probe extending into the flow path of the discharge gas. Inlet orifices in the high pressure probe include inlet orifices facing directly upstream relative to the gas for communication of the total pressure of the flowing gas to the inside of a reservoir containing the deicing agent. The injection probe connects with an outlet of the reservoir and includes outlet orifices facing directly downstream of the discharge gas flow so that the reservoir is subjected to a driving pressure derived from the difference between the total pressure of the flowing gas and its reverse dynamic pressure. An adjustable connector mounting the high pressure probe in the discharge flow path of the gas allows the inlet orifices to be selectively oriented between positions facing directly upstream and perpendicular thereto to selectively vary the driving pressure.

Saltation thresholds and entrainment of fine particles at Earth and Martian pressures

Abstract: An open circuit wind tunnel designed to operate in a large vacuum chamber was built at NASA-Ames to investigate saltation threshold, flux, deflation rates, and other aeolian phenomena on the planet Mars. The vacuum chamber will operate at pressures as low as 4 mbar, and the tunnel operates at windspeeds as high as 150 m/sec. Either air or CO2 can be used as a working fluid. It was found that, to a first order approximation, the same dynamic pressure was required at Martian pressure to entrain or saltate particles as was required on Earth, although wind and particle speed are considerably higher at Martian pressure. A 2nd wind tunnel, designed to operate aboard the NASA KC-135 0-g aircraft to obtain information on the effect of gravity on saltation threshold and the interparticle force at 0-g, is also described and test data presented. Some of the experiments are summarized and various aspects of low pressure aeolian entrainment for particles 12 to 100 micron in diameter are discussed, some of them unique to low pressure testing and some common in Earth pressure particle transport testing. The facility, the modes of operation, and the materials used are described.

The Practice of Dynamic Pressure Measurement

Abstract: Dynamic pressure measurement is practised over a wide range of applications extending from, for example, the assessment of blade performance in a gas-turbine to diagnosis of cardiovascular disease. However, the majority of applications falls broadly within the field of mechanical engineering. In the present context, the term dynamic refers to measurements in which there is interest in a time-varying pressure component which has a time-constant of one second or less. These measurements are made using a pressure transducer, of which many different types are in use (see Figure 1). The timeconstant of one second is an arbitrary division but will serve to distinguish between measurements of static or steady pressures and dynamic events. Dynamic pressure herein does not refer to the fluid mechanics quantity pv/2 (p = density, v =velocity). The purpose of this paper is to present the findings of a recent survey on dynamic pressure measurement practice. The objectives of the survey were as follows: (i) to assess the nature of representative dynamic pressure measurements as characterized by: frequency, amplitude, dc-bias levels; repetitive events and associated waveforms, intermittent events, or single events and associated tin1e-scale (ii) to identify the instrumentation and operating procedures, noting if fluid transmission lines are used between the point of measurement and the transducer (iii) to identify any calibration procedures used and their traceability (iv) to identify the adequacy of manufacturers' specifications for dynamic measurements.

Composite type slide guide device of machine tool

Abstract: PURPOSE:To compensate for a load acting on the inner surface of a base bed slide guide so that frictional slide force can be set, by controlling pressurized air supplied to a plurality of static pressure pads having gaps for pressurized air flow in no contact with a slide guide surface. CONSTITUTION:Air for a static pressure pad is supplied from an air pressure source 1 through a pressure controlling valve 12 to an air supply groove 13. A workpiece 14 is mounted on a slide 3, and the weight Wt of slide 3, weight Ww of workpiece 14 and cutting force F or the like acting on the workpiece 14 work on a dynamic pressure slide surface as surface pressure and a floating force Fp acting on the static pressure supplied to the static pressure pad crbitrary floating force is obtained, so that the share of dynamic pressure slide surface and static pressure pad can be set at will according to load requirements only by supplying air pressure to set optional frictional force.

Cold Flow Determination of the Internal Flow Environment Around the Submerged TVC Nozzle for the Space Shuttle SRM

Abstract: A series of subscale cold flow tests was performed to quantify the gas flow characteristics at the aft end of the Space Shuttle Solid Rocket Motor. This information was used to support the analyses of the redesigned nozzle/case joint. A portion of the thermal loads at the joint are due to the circumferential velocities and pressure gradients caused primarily by the gimbaling of the submerged nose TVC nozzle. When the nozzle centerline is vectored with respect to the motor centerline, asymmetries are set up in the flow field under the submerged nozzle and immediately adjacent to the nozzle/case joint. Specific program objectives included: determination of the effects of nozzle gimbal angle and propellant geometry on the circumferential flow field; measurement of the static pressure and gas velocities in the vicinity of the nozzle/case joint; use of scaling laws to apply the subscale cold flow data to the full scale SRM; and generation of data for use in validation of 3-D computational fluid dynamic, CFD, models of the SRM flow field. These tests were conducted in the NASA Marshall Space Flight Center Airflow Facility with a 7.5 percent scale model of the aft segment of the SRM. Static and dynamic pressures were measured in the model to quantify the flow field. Oil flow data was also acquired to obtain qualitative visual descriptions of the flow field. Nozzle gimbal angles of 0, 3.5, and 7 deg were used with propellant grain configurations corresponding to motor burn times of 0, 9, 19, and 114 seconds. This experimental program was successful in generating velocity and pressure gradient data for the flow field around the submerged nose nozzle of the Space Shuttle SRM at various burn times and gimbal angles. The nature of the flow field adjacent to the nozzle/case joint was determined with oil droplet streaks, and the velocity and pressure gradients were quantified with pitot probes and wall static pressure measurements. The data was applied to the full scale SRM thru a scaling analysis and the results compared well with the 3-D computational fluid dynamics computer model.

Static pressure slide

Abstract: PURPOSE:To provide a metal precision machine which provides high-precise dynamic precision and has excellent machining precision, by a method wherein, in a static pressure slide serving as a metal precision machine for precision machining, a pressure medium is water or a water soluble machining solution CONSTITUTION:With a pump 16 run, water in a water tank 15 is increased in a pressure for discharged, a fine particle in water is removed by means of a filter 14a to regulate a pressure by means of a pressure regulating valve 14b The water is branched from a flow passage 12 to flow passages 8 and 11 through a throttle 14d, and flows from pockets 7 and 9 to spaces between sip surfaces 3f and 5f, 3r and 5r, and 4u and 6u A table 1 is supported through slides 5 and 6 by means of a static pressure of water generated therebetween As noted above, by a fact that the pressure medium of a static pressure slide is water, the frequency of floating of the table 1 due to a dynamic pressure is reduced, high-precise dynamic precision can be provided, and a metal precision machine having excellent machining precision can be provided

Noninvasive automatic blood pressure monitor

Abstract: PURPOSE: To continuously compensate a target value and a gain without interrupting measurement of blood pressure by continuously monitoring vibration of the volume of a blood vessel, which is composed of a basic pressure waveform and pressure vibration superposed with the former, and by guiding a compensating signal, which is then delivered to a basic servo system. CONSTITUTION: In an adding element 19, a voltage-pressure converter 6 adds pressure vibration having a frequency higher than that of a maximum harmonic wave component of a blood pressure waveform and delivered from an oscillator 24, to an output voltage from a phase compensator 17 so as to deliver pressure variation. Pressure variation in a pressurizing cuff 1 generates vibration which is small in comparison with a volume of an artery but can be measured, and which is detected by a detector 11 and then amplified by an amplifier and a band width amplifier 25 before it is detected by a detector 26. An evaluation circuit 27 detects only a transient deviation of a dynamic pressure vessel compliance at the initiation of each pulsation, and derives an error signal, which is then delivered to an integrator 22 whose output power gives a target value of a servo-system through an adder 14. Thus, the degree of compression of the artery is automatically and continuously corrected so that the tension of the wall of the artery becomes minimum.

Device for generating wind speed following vehicle speed

Abstract: PURPOSE:To correct humidity at a speed corresponding to variation in vehicle speed by detecting dew-point temperature nearby a wind speed detection point, finding a corresponding correction coefficient for air specific gravity varying with humidity, and multiplying a dynamic pressure detection signal obtained by using a pipot tube by the coefficient. CONSTITUTION:A dew-point temperature detector 20 is provided nearby the wind speed detection point to detect the dew-point temperature, which is converted by a dew-point temperature transmitter into a dew-point detection signal 22 and sent to an optional function generator 23. A correction coefficient curve corresponding to the dew-point temperature is inputted to the generator 23 preliminarily and a signal 24 of the correction coefficient C for air specific gravity varying with humidity corresponding to the signal 22 is generated based upon the curve and sent to a multiplication computing element 25. Here, the dynamic pressure Pd detected by the pipot tube 12 is multiplied (CXPd') by a dynamic pressure Pd' detection signal after temperature and pressure correction to perform the humidity correction of the dynamic pressure detection signal. This processing is continuous processing by an analog circuit, so the response is fast and wind-speed control corresponding to variation in vehicle speed can be followed up. The output signal of the computing element 25 is sent to a wind speed indicating controller 03 through an opening/closing computing element 19 to obtain a corrected wind speed value.

Dynamic pressure wind sensor (anemometer) for speed and direction

Abstract: The dynamic pressure wind sensor for direction and speed permits measured values to be detected without the use of mechanically moving parts and without periodic maintenance, and guarantees a long service life. The sensor can be rendered submersible (immersible) by means of a suitable design. Self-calibration is possible with the aid of integrated controllable valves.