Showing papers on "Dynamic pressure published in 2011"

The wall pressure signature of transonic shock/boundary layer interaction

Abstract: The structure of wall pressure fluctuations beneath a turbulent boundary layer interacting with a normal shock wave at Mach number M∞ = 1.3 is studied exploiting a direct numerical simulation database. Upstream of the interaction, in the zero-pressure-gradient region, pressure statistics compare well with canonical low-speed boundary layers in terms of fluctuation intensities, space–time correlations, convection velocities and frequency spectra. Across the interaction zone, the root-mean-square wall pressure fluctuations attain very large values (in excess of 162 dB), with a maximum increase of about 7 dB from the upstream level. The two-point wall pressure correlations become more elongated in the spanwise direction, indicating an increase of the pressure-integral length scales, and the convection velocities (determined from space–time correlations) are reduced. The interaction qualitatively modifies the shape of the frequency spectra, causing enhancement of the low-frequency Fourier modes and inhibition of the higher ones. In the recovery region past the interaction, the pressure spectra collapse very accurately when scaled with either the free-stream dynamic pressure or the maximum Reynolds shear stress, and exhibit distinct power-law regions with exponent −7/3 at intermediate frequencies and −5 at high frequencies. An analysis of the pressure sources in the Lighthill's equation for the instantaneous pressure has been performed to understand their contributions to the wall pressure signature. Upstream of the interaction the sources are mainly located in the proximity of the wall, whereas past the shock, important contributions to low-frequency pressure fluctuations are associated with long-lived eddies developing far from the wall.

Studies of a high-sensitive surface acoustic wave sensor for passive wireless blood pressure measurement

Abstract: This paper develops a novel, high-sensitive surface acoustic wave (SAW) blood pressure sensor based on a 434.5 MHz resonator fabricated on an ST-cut quartz beam. First, 50 types of resonators with different layouts were designed, and then the sensitivity of the pressure sensors with different structures and sizes was simulated and calculated by using COMSOL Multiphysics software. Finally, a resonator with good performance was selected to fabricate a set of blood pressure sensors in different sizes, and these sensors were tested and evaluated through the use of both static and dynamic pressure measurements as well as animal experiments. For the sensor with a beam size of 10 mm × 1.3 mm × 0.3 mm, the results showed that in the range of 0–300 mmHg the pressure sensitivity was about 1.9 kHz/mmHg with good linearity, which matched well with the simulation results, additionally, the maximum non-linear curve fitting error was found to be less than ±1 mmHg. Moreover, it could detect a pressure change as small as 0.1 mmHg. This sensor can be used to monitor blood pressure passively and wirelessly, and it will hopefully be applied in implantable devices for body pressure measurements in further research.

Numerical Analysis of a Spiral-groove Dry-gas Seal Considering Micro-scale Effects

Abstract: A dry-gas seal system is a non-contact seal technology that is widely used in different industrial applications.Spiral-groove dry-gas seal utilizes fluid dynamic pressure effects to realize the seal and lubrication processes,while forming a high pressure gas film between two sealing faces due to the deceleration of the gas pumped in or out.There is little research into the effects and the influence on seal performance,if the grooves and the gas film are at the micro-scale.This paper investigates the micro-scale effects on spiral-groove dry-gas seal performance in a numerical solution of a corrected Reynolds equation.The Reynolds equation is discretized by means of the finite difference method with the second order scheme and solved by the successive-over-relaxation(SOR) iterative method.The Knudsen number of the flow in the sealing gas film is changed from 0.005 to 0.120 with a variation of film depth and sealing pressure.The numerical results show that the average pressure in the gas film and the sealed gas leakage increase due to micro-scale effects.The open force is enlarged,while the gas film stiffness is significantly decreased due to micro-scale effects.The friction torque and power consumption remain constant,even in low sealing pressure and spin speed conditions.In this paper,the seal performance at different rotor face spin speeds is also described.The proposed research clarifies the micro-scale effects in a spiral-groove dry-gas seal and their influence on seal performance,which is expected to be useful for the improvement of the design of dry-gas seal systems operating in the slip flow regime.

Dual feedback vacuum fluidics for a flow-type particle analyzer

Abstract: The present invention relates to a vacuum-driven fluidic system for a flow-type particle analyzer. The system includes a vacuum pump which creates a pressure drop downstream of the flow cell, which pulls sheath fluid and sample fluid through the flow cell. A variable-resistance fluidic resistor is configured to control the ratio of sample fluid flow to sheath fluid flow. Dual feedback circuits, one configured to modulate the vacuum pump power in response to the pressure drop across the flow cell, referred to as the dynamic pressure drop, and a second configured to modulate the vacuum pump power in response to the pressure drop created by the vacuum pump relative to ambient pressure, referred to as the static pressure drop, are used to automatically control the system. The present invention enables adjustment of the sample fluid flow rate while maintaining a constant total fluid flow through the flow cell, and further, enables pausing the system without significant fluctuations in the vacuum.

Multiple responses of magnetotail to the enhancement and fluctuation of solar wind dynamic pressure and the southward turning of interplanetary magnetic field

Abstract: During the interval from 06:15 to 07:30 UT on 24 August 2005, the Chinese Tan-Ce 1 (TC1) satellite observed the multiple responses of the near-Earth magnetotail to the combined changes in solar wind dynamic pressure and interplanetary magnetic field (IMF). The magnetotail was highly compressed by a strong interplanetary shock because of the dynamic pressure enhancement (similar to 15 nPa), and the large shrinkage of magnetotail made a northern lobe and plasma mantle move inward to the position of the inbound TC1 that was initially in the plasma sheet. Meanwhile, the dynamic pressure fluctuations (similar to 0.5-3 nPa) behind the shock drove the quasi-periodic oscillations of the magnetopause, lobe-mantle boundary, and geomagnetic field at the same frequencies: one dominant frequency was around 3 mHz and the other was around 5 mHz. The quasi-periodic oscillations of the lobe-mantle boundary caused the alternate entries of TC1 into the northern lobe and the plasma mantle. In contrast to a single squeezed or deformed magnetotail by a solar wind discontinuity moving tailward, the compressed and oscillating magnetotail can better indicate the dynamic evolution of magnetotail when solar wind dynamic pressure increases and fluctuates remarkably, and the near-Earth magnetotail is quite sensitive even to some small changes in the solar wind dynamic pressure when it is highly compressed. Furthermore, it is found that a considerable amount of oxygen ions (O(+)) appeared in the lobe after the southward turning of IMF.

Launch Vehicle Base Buffeting - Recent Experimental and Numerical Investigations

Abstract: During atmospheric ascent of launcher configurations, a massively separated flow environment in the base region of the launcher can generate strong low frequency wall pressure fluctuations. The nozzle structure can be subjected to dynamic loads resulting from these pressure fluctuations. The loads are usually most severe during the high dynamic pressure phase of flight at transonic speeds and the aerodynamic excitation can induce a response of the structural modes called buffeting. In order to obtain a deeper insight into base buffeting related to the Ariane 5 launch vehicle, a set of experiments was performed in the DNW HST wind tunnel in close cooperation with the utilization of modern CFD tools (hybrid RANS/LES). During the test campaign a 1/60 scale Ariane 5 launcher test article was utilized, and detailed unsteady pressure measurements in the base region of the model were for the first time performed in conjunction with time resolved velocity field measurements using PIV. The work was performed in the framework of the ESA TRP “Unsteady Subscale Force Measurements within a Launch Vehicle Base Buffeting Environment”.

Evaluation of intrinsic velocity—pressure trends from low-pressure P-wave velocity measurements in rocks containing microcracks

Abstract: Dependent on the ‘intrinsic’ effects on the crystal lattice of the rock constituents and the diminishing ‘extrinsic’ effects of pores and microcracks, elastic wave velocity versus pressure trends in cracked rocks are characterized by non-linear velocity increase at low pressure. At high pressure the ‘extrinsic’ influence vanishes and the velocity increase becomes approximately linear. Usually, the transition between non-linear and linear behaviour, the ‘crack closure pressure’, is not accessible in an experiment, because actual equipment is limited to lower pressure. For this reason, several model functions for describing velocity—pressure trends were proposed in the literature to extrapolate low-pressure P-wave velocity measurements to high pressures and, in part, to evaluate the ‘intrinsic’ velocity—pressure trend from low-pressure data. Knowing the ‘intrinsic’ velocity trend is of particular importance for the quantification of the crack influence at low pressure, at high pressure, the ‘intrinsic’ trend describes the velocity trend as a whole sufficiently well. Checking frequently used model functions for suitability led to the conclusion that all relations are unsuitable for the extrapolation and, if applicable, the estimation of the ‘intrinsic’ velocity trend. However, it can be shown that the ‘intrinsic’ parameters determined by means of a suitable model function, the zero pressure velocity and the pressure gradient depend on maximum experimental pressure in a non-linear way. Our approach intends to obtain better estimates of particular parameters from observed non-linear behaviour. A converging exponential function is used to approximate particular trends, assuming that the point of convergence of the function represents a better estimate of the zero pressure velocity and the pressure gradient, respectively. Whether the refined ‘intrinsic’ velocity trend meets the ‘true intrinsic’ velocity trend within acceptable errors cannot be proven directly due to missing experimental data at very high pressure. We, therefore, conclude that our approach cannot ensure absolutely certain ‘intrinsic’ velocity trends, however, it can be shown that the optimized trends approximate the ‘true intrinsic’ velocity trend better as all the other relations do.

Theoretical and Experimental Identification of Acoustic Spinning Mode in a Cylindrical Combustor

Abstract: The analytical solution for the eigenmodes of a cylindrical combustor allows for several realizations of the first tangential mode. The limiting cases of standing and spinning first tangential modes are well known. The general solution for a first tangential mode, however, allows for a large variety of realizations. In this study the analytical solution of the acoustic problem and a numerical time-resolved simulation of the acoustic pressure field are compared with experimental data from hot-fire tests. The experimentally observed pressure data are in excellent agreement with the simulation for all possible theoretical solutions. The approach enables detailed insight into the dynamics of the pressure field and thus constitutes a tool for the characterization of acoustic pressure waves in a cylindrical combustor even when the amplitude of the investigated eigenmode is small as compared with the mean pressure fluctuation.

Real-Time Dynamics Simulation of Unmanned Sea Surface Vehicle for Virtual Environments

Abstract: The role of virtual environments (VEs) is crucial in efficient design and operation of unmanned vehicles. VEs are extensively used in operator training for tele-operation, planning using programming by demonstration, and hardware and software designs. VE for unmanned sea surface vehicles (USSV) requires a 6 degree of freedom dynamics simulation in the time domain. In order to be interactive, the VE requires real-time performance of the underlying dynamics simulator. In general, the dynamics simulation of USSVs involves the following four main operations: (1) computation of dynamic pressure head due to fluid flow around the hull under the ocean wave, (2) computation of wet surface, (3) computing the surface integral of the dynamic pressure head over the wet surface, and (4) solving the rigid body dynamics equation. The first three operations depend upon the boat geometry complexity and need to be performed at each time step, making the simulation run very slow. In this paper, we address the problem of physics preserving model simplification for real-time potential flow based simulator for a USSV in the time domain, with an arbitrary hull geometry. This paper reports model simplification algorithms based on clustering, temporal coherence, and hardware acceleration using parallel computing on multiple cores to obtain real time simulation performance for the developed VE.

Different response of dayside auroras to increases in solar wind dynamic pressure

Abstract: Variations in the solar wind dynamic pressure can create changes in the auroral brightness, especially in the dayside region. In this study, mainly using Polar Ultraviolet Imager auroral images and NASA OMNI magnetic field and plasma data, we investigate the relationship between interplanetary parameters and dayside aurora intensification. We first identify the dayside aurora cases caused by the solar wind dynamic pressure increases from 1997 through 1999 and divide these cases into two types: one with intensification and the other without significant intensification following the increase in the solar wind dynamic pressure. Then, case by case, we examine the separate roles of the solar wind density and velocity on auroral brightness. Our result demonstrates that the dayside aurora intensification requires the contributions of both the density and solar wind velocity increases. The solar wind density increase alone (without velocity increase) could not create the dayside aurora intensification.

Experimental Investigation of the Pressure Distribution beneath a Floating Ice Block

Abstract: Discrete ice floes approaching an ice cover from upstream will contribute to the lengthening of the cover or will become entrained in the flow. Currently, ice process models rely on empirical relationships to predict the behavior of ice floes at the leading edge of an intact ice cover. Knowledge of the hydrodynamic forces acting on individual ice floes is an important component of any model attempting to predict ice-cover progression. Experimental studies were conducted in a recirculating flume in the T. Blench Hydraulics Laboratory at the University of Alberta to increase the knowledge of the physical behavior of ice floes in water and the hydrodynamic forces that act on them. A hollow Plexiglas acrylic ice block outfitted with pressure taps was constructed to facilitate measurements of the pressure distribution beneath an ice block. The dynamic pressure was measured under the block for various block thickness-to-depth ratios and flow velocities. The dynamic pressure was found to decrease for increasing block thickness-to-approach flow depth ratios and increasing flow rates. A block with a rounded leading edge was also tested, and it showed a significantly reduced leading-edge pressure effect. The rectangular ice block results were categorized into separate effects: a pressure reduction attributable to Venturi effects and a pressure reduction attributable to leading-edge effects. A predictive relationship was developed for the pressure distribution beneath a floating ice block and the subsequent submerging force and underturning moment.

Estimation of Velocity Pressure Exposure Coefficient using GIS

Abstract: As an urbanization is in progress, the change of the planimetric features and topography including high-rise residential buildings commonly occur. The change of the planimetric features and topography causes occurrence of the strong wind and wind speed increase or decrease due to the effect of planimetric features and topography on the windward side even though the wind blows with the same speed. In the design standard, this change by wind speed is defined as the velocity pressure exposure coefficient, the value of coefficient is estimated and reflected by ground surface roughness, but in a reality, ground surface roughness is determined in accordance with the subjective judgement of designer and then the velocity pressure exposure coefficient is estimated, moreover the research and data for classification of ground surface roughness are insufficient. In this paper, we will estimate the velocity pressure exposure coefficient by the quantified method for classifying ground surface roughness by using GIS according to the height of a building targeting area where high-rise residential buildings are built lately. When the structure subjected to wind load is designed, reasonability of design and safety of structure will be more improved by using the estimation method of velocity pressure exposure coefficient presented in this study.

Dynamic and static pressure composite gas bearing with internal pi shaped air wedge groove

Abstract: The invention provides a dynamic and static pressure composite gas bearing with an internal pi shaped air wedge groove, which relates to bearing technology, and belongs to a gas bearing with a novel structural form for supporting an ultrahigh speed rotary machine The gas bearing is structurally characterized in that the inner surface of the bearing adopts pi shaped air wedge groove design, dynamic and static pressure composite design, and dynamic and static pressure design of a thrust surface; the thrust surface adopts spiral pressurizing groove design; and the inner surface and the thrust surface are provided with a static pressure gas supply hole respectively The gas bearing overcomes the defects of the coupling and mutual interference between static pressure and dynamic pressure, overcomes the defect that the dynamic pressure effects at two ends of the bearing are inconsistent, not only remarkably improves the bearing capacity and rotating speed of the bearing, but also greatly reduces the axial and transverse vibration of a rotor journal, and improves the stability and reliability of a rotor system Therefore, the gas bearing has the advantages of simple structure, high bearing capacity, stable operation and high reliability, and further widens the application range of the gas bearing

Enhanced static-dynamic pressure transducer suitable for use in gas turbines and other compressor applications

Abstract: A filter assembly for use with a static-dynamic piezoresistive pressure transducer that measures low amplitude, dynamic pressure perturbations superimposed on top of a high static pressure through the implementation of a low-pass mechanical filter assembly is disclosed. The filter assembly may comprise a dual lumen reference tube and a removable filter subassembly further comprising a porous metal filter and narrow diameter tube. The transducer, which may be capable of operating at ultra-high temperatures and in harsh environments, may comprise of a static piezoresistive pressure sensor, which measures the large pressures on the order of 200 psi and greater, and an ultrasensitive, dynamic piezoresistive pressure sensor which may capture small, high frequency pressure oscillations on the order of a few psi or less. The filter assembly may transmit static pressure to the back of the dynamic pressure sensor to cancel out the static pressure present at the front of the sensor while keeping dynamic pressure from reaching the back of the sensor. In this manner, the filter assembly enables the transducer to accurately read dynamic pressure in the presence of high static pressure without rupturing the thin diaphragm of the dynamic pressure sensor.

Dynamic Response to Global Oscillation of Propulsion Systems with Cavitating Pumps

Abstract: A time-domain model was developed to evaluate the dynamic response of pumping systems in the accelerating environment of rockets with a focus on cavitation. The model was first verified by comparing the results with measurements in ground-based tests of an LE-7A rocket engine. In these tests, various resonances occurred and levels of pump cavitation or incorporation of an accumulator altered them. The model results simulated the test data well, matching both the frequency and the amplitude. The test and model results also demonstrated the stability of the LE-7A propulsion system within nonaccelerating environments. Then, the model was used to examine the response of the propulsion system in accelerating frames; sinusoidal vehicle oscillations over a range of frequencies were explored. Under noncavitating conditions, the pressure amplitudes within the propulsion system did not substantially exceed the quasi-static acceleration head response ρah. However, under cavitating conditions (σ = 0.02), the same accelerations produced violent responses with pressure and flow amplitudes about 2 orders of magnitude greater than in noncavitating conditions. The obvious conclusion is that vehicle oscillations can cause substantial pressure and flow amplitudes, particularly when the pump is cavitating, even if the ground-based tests and the calculations in static frames indicate stable and well-behaved responses.

Short-time pressure response during the start-up of a constant-rate production of a high pressure gas well

Abstract: The start-up flow of a constant-rate production of a high pressure gas well is studied, with emphasis on the effect of gas acceleration. Gas acceleration is important in the near wellbore region for a high pressure gas in a high permeability formation. It is shown that when gas acceleration is important, the system of governing equations for the porous media flow becomes hyperbolic. In response to an impulsively imposed mass flow-rate, a steep pressure front is created at the wellbore and it propagates into the formation. This steep pressure front is trailed by large amplitude pressure waves. As they travel away from the wellbore, the pressure front becomes less steep and the amplitude of the trailing waves decreases due to viscous damping. It is found that the pressure drawdown experiences a rapid increase followed by an oscillatory behavior in short times before approaching the classical logarithmic rise regime. The pressure gradient at the wellbore wall can grow to a large magnitude in the early times,...

Prediction of total pressure characteristics in the settling chamber of a supersonic blowdown wind tunnel

Abstract: In the design of control system of a wind tunnel, it is important to understand the importance of operations of mechanical systems in order to ensure that any emergencies that may arise during the running of the wind tunnel are properly handled by the system. In the NAL 0.6m blowdown wind tunnel, it is proposed to incorporate a Variable Mach number Flexible Nozzle (VMFN), using which the tunnel13; can be started at a low Mach number and the required test Mach number (up to 4) can be reached by continuously (on-line) changing the nozzle contour using an Electroservohydraulic drive. Before stopping the tunnel, the VMFN would be reverted to the initial low Mach number condition. During the entire operation of the tunnel in such a scenario, it is essential that the Pressure Regulating Valve (PRV) maintains the specified or minimum stagnation pressure in the test section by following a safe trajectory. In order to determine a safe trajectory, a basic understanding of the variation of stagnation pressure in the settling chamber is called for, before the PRV control system is designed. In this paper, the problem is13; formulated based on quasi-steady isentropic equations and programmed in C language to predict the timehistories13; of settling chamber pressure and storage tank pressure for a given trajectory of the opening of PRV, as the VMFN throat is changed from Mach 1 to Mach 4 condition and vice versa. In order to validate the present methodology, the PRV trajectory measured during an experiment in the NAL 0.6m13; wind tunnel was used as input to the program and the measured time-histories of settling chamber pressure and storage tank pressure are compared with the predicted values. Predictions of settling chamber pressure and the storage tank pressure relevant to VMFN operation indicate that settling chamber pressure rapidly builds up towards the storage tank pressure, apparently due to the constriction offered at the VMFN throat as VMFN throat is changed from M=1 contour to M=4 contour during the13; start of the run. Minimum PRV opening area has been predicted to maintain the settling chamber pressure13; higher than the estimated minimum value at high Mach numbers. For smaller openings of the PRV (lt;0.065m2), the predicted pressure falls below the minimum and is hence unsafe. From the predicted time history of free-stream dynamic pressure (q), it is noted that alarming increase in q can occur during starting and stopping transients, which can damage a test model in the tunnel, balance and such other components. Therefore, the design of test object and support system need to be adequately designed.

Dynamic effects in a clearance-sealed piston prover for gas flow measurements

Abstract: A piston prover determines the gas flow rate by measuring the time interval that a movable piston inside a cylinder needs to pass a known volume of gas at a defined pressure and temperature. This paper deals with the dynamic effects related to the operation of a high-speed, clearance-sealed realization of the piston prover concept. Its dynamic characteristics are analysed by means of pressure-response measurements and lumped-element mathematical modelling. The experimental results show that the pressure oscillations during the timing cycle increase significantly above a certain flow rate and have multiple frequency components. They could be related to the resonance effects of the piston oscillator, which is excited by the flow instabilities of the gas flowing in the cylinder below the piston. The simulations show that the sensitivity to the dynamic pressure effects depends on the properties of the thermodynamic gas processes being adiabatic, polytropic or isothermal. A new, modified flow equation of the piston prover, which considers the polytropic index as an input variable, is proposed.

Characteristics of a dynamic pressure generator based on loudspeakers

Abstract: The dynamic pressure generator under discussion consists of two, face-to-face-orientated electrodynamic loudspeakers and the air chamber between. The aim of this paper is to investigate the static and dynamic characteristics of this pressure generator. Physical modelling and an experimental analysis were employed to demonstrate its capabilities and limitations. The generator's static sensitivity, which was defined by the ratio between the generated pressure and the excitation electric current, mainly depends on the ratio between the force factor and the effective area of the loudspeakers. The presented system has relatively good precision and stability, and a small sensitivity to changes in the internal volume. Its dynamic characteristics are defined by the properties of the loudspeaker diaphragm, the air chamber between the loudspeakers and the connection of the device under test to the pressure generator.

High-speed permanent magnet motor/generator

Abstract: The utility model discloses a high speed permanent magnet motor/generator. Bearing pedestals on the two ends of a housing are provided with a dynamic pressure gas radial bearing respectively, wherein an outer end of the dynamic pressure gas radial bearing of one bearing pedestal is provided with a dynamic pressure gas footstep bearing. A rotary shaft of a rotor is fixedly arranged in shaft holes of the dynamic pressure gas radial bearing and the dynamic pressure gas footstep bearing. An inner sleeve of the dynamic pressure gas radial bearing and an inner disc of the dynamic pressure gas footstep bearing generate an air wedge in a fit clearance between a corresponding outer sleeve and a corresponding outer disc, so a high pressure air film is formed to support the high speed rotation of the inner sleeve and the inner disc, and through utilizing the centrifugal impeller principle, more air is pressed into an air clearance to form a higher pressure air film. The high speed permanent magnet motor/generator has the advantages of high rotating speed, big power density, small inertia, fast response, reliable performance, long service lifetime, low noise, simple structure, small volume, and the like. Besides, the high speed permanent magnet motor/generator can save a large amount of manufacturing materials, and has a wide application prospect.

Aeroacoustic Noise Source Identification Using Irregularly Sampled LDV Measurements Coupled with Beamforming (AIAA-2011-2719)

Abstract: This paper develops a technique which relates dynamic pressure measurements taken outside the hydrodynamic field of a low speed jet to single point, one component velocity measurements taken within the jet using a Laser Doppler Velocimetry (LDV) system. To improve the signal to noise ratio of the pressure measurement, a coherence based acoustic beamforming technique is applied and focussed on the LDV measurement volume in order to evaluate its contribution to the measured sound. As the pressure samples are acquired at regular time steps whereas the velocity at irregular time intervals dependent on the particle seeding, the calculation of the autoand cross-spectra of the pressure and velocity measurements require special treatment. The signal processing procedures required to calculate these are described and implemented in the paper. To validate the proposed technique real experimental data was analysed. Laser Doppler Velocimetry measured velocity fluctuations created by rods placed in a jet. Synchronously, a planar random array focused on the same plane as the LDV measurement, measured pressure fluctuation outside the hydrodynamic field. The same set of data was then analysed using conventional and coherence based beamforming algorithms. The results from both techniques were compared. While conventional beamforming identified the contribution from the main sources within the flow, the coherence based method was able to single out the source related to the local measurement. The results shown demonstrated how coherence based beamforming, combined with LDV, can be a useful tool for aeroacoustic noise source investigations.

Real-time measuring device for air supply flow of boiler

Abstract: The utility model discloses a real-time measuring device for air supply flow of a boiler, belonging to the field of process parameter measurement. The real-time measuring device comprises a measuring pipe section, a sensor component, a micro-differential pressure transmitter, a pressure transmitter, a temperature transmitter, an I/V converter, an A/D converter, a programmable control sampling switch and a microcomputer signal processing system, wherein the air supply flow measuring pipe section is hermetically connected with an air supply pipeline by upstream and downstream flanges; and a plurality of double-stage dynamic pressure venturi tubes are arranged on different measuring points of the cross section of the air supply flow measuring pipe section to form the sensor component of the measuring device, and air velocity of the output dynamic pressure of each double-stage venturi tube is measured by the matched micro-differential pressure transmitter, thus calculating the air supply flow. Compared with the prior art, the device has higher sensitivity and larger output differential pressure signals even at low velocity, and the effectiveness and accuracy of the measurement flow are obviously improved.

Pressure sensor and pressure difference sensor

Abstract: A pressure sensor includes a hydraulic path filled with a pressure transfer liquid and a pressure transducer having a pressure sensitive deformation body. The hydraulic path includes a channel which extends from a pressure input opening at least to the deformation body, wherein the pressure input opening is spaced a separation distance from the deformation body, and wherein pressure on the deformation body deviates from pressure at the pressure input opening by the difference of the hydrostatic pressure of the pressure transfer liquid between the pressure input opening and the deformation body. The pressure sensor further includes an inclination sensor for determining at least one inclination value dependent on the inclination of the hydraulic path, and a processing circuit, which is suitable to determine the difference of the hydrostatic pressure of the pressure transfer liquid between the pressure input opening and the deformation body as a function of inclination value, a density value of the pressure transfer liquid and a separation distance.

Comparison of Sampling Methods for a Dynamic Pressure Regulator

Abstract: Concepts for complex products are often developed using computer models, introducing uncertainties both in design and model accuracy. There exist several methods for approximating these uncertainties and this paper presents and compares some of them. The focus is on sampling based methods including or excluding response surfaces, and they are compared by accuracy and computation time, using a Monte Carlo sampling as reference. The application is a simplified system model of a dynamic pressure regulator that controls the air supply in the environmental control system of an aircraft. Nomenclature A2 = piston area for output flow Am = maximum opening area of main valve As = piston area for support flow Av = maximum opening area of vent valve �� i = the i th coefficient for a response surface d = average distance between two vectors kij = the normalized sensitivity for the i th system characteristic to the j th system parameter mp = mass of piston n = number of samples p2 = pressure in the environmental control system pe = end pressure in the environmental control system

Development of a General Dynamic Pressure Based Single-Phase Spray Cooling Heat Transfer Correlation

Abstract: One of the main challenges of spray cooling technology is the prediction of local and average heat transfer coefficients on the heater surface. It is hypothesized that the local heat transfer coefficient can be predicted from the local normal pressure produced by the spray. In this study, hollow cone, full cone, and flat fan sprays, operated at three standoff distances, five spray pressures, and two nozzle orientations, were used to identify the relation between the impingement pressure and the heat transfer coefficient in the single-phase regime. PF-5060, PAO-2, and PSF-3 were used as test fluids, resulting in Prandtl number variation between 12 and 76. A microheater array operated at constant temperature was used to measure the local heat flux. A separate test rig was used to make impingement pressure measurements for the same geometry and spray pressure. The heat flux data were then compared with the corresponding impingement pressure data to develop a pressure-based correlation for spray cooling heat transfer. The maximum deviation between the experimental data and prediction was within ±25%.