The Influence of Construction Features of a Thin-Layer Sensor on Pressure Distributions Recorded in an Elastohydrodynamic Contact

2012 ◽  
Vol 134 (1) ◽  
Author(s):  
Adam Wilczek
Keyword(s):  
Thin Layer ◽  
Piezoelectric Properties ◽  
Active Part ◽  
Pressure Measurements ◽  
Rotation Direction ◽  
Pressure Distributions ◽  
Measurement Signal ◽  
Piezoelectric Effects ◽  
Signal Distortions ◽  
Different Shapes

This paper presents the experimental study of the construction features of a thin-layer sensor on the accuracy of pressure measurements in an EHD contact. Two common types of transducer shapes and isolating layers of the sensor, made of SiO are considered. The measurements were carried out on a two-disc machine, with the use of two mating lubricated steel cylindrical disks. On the outside surface of one of the discs, a pressure sensor was deposited with two transducers of different shapes, symmetric and asymmetric, located close to each other. The pressure transducer has an active part in the form of a layer contraction, and two wider parts of the layer serves as electrical leads (connections). In the symmetric transducer, the active part is located in the middle of the connections width and in the asymmetric transducer the active part is located along the edge of connections. In case of no current supply for the measurement bridge, the measurement signals from the sensor were observed. The occurrence of these signals indicated piezoelectric properties of the insulation layers of the sensor. The investigations showed that the shape of the transducer has a significant influence on the accuracy of pressure measurements. In the case of the asymmetric transducer, the measurement signal distortions caused by the piezoelectric effects and changes in the electric capacitance of the sensor were much larger than in the case of the symmetric transducer. Measurement signal courses coming from the asymmetric transducer were significantly influenced by the transition velocity of the sensor trough the contact, by the value of the current supplying the measurement bridge and by the rotation direction of the disc with the sensor.

Influence of Electrical Parameters of a Thin-Layer Sensor on the Accuracy of Pressure Measurement in an EHD Contact

2011 ◽  
Vol 133 (3) ◽  
Author(s):  
Adam Wilczek
Keyword(s):  
Thin Layer ◽  
Measurement System ◽  
Pressure Measurement ◽  
Piezoelectric Properties ◽  
Current Source ◽  
Circuit Model ◽  
Active Part ◽  
Model Study ◽  
Measurement Signal ◽  
Piezoelectric Effects

This paper presents a model study of inductive, capacitive, and piezoelectric effects on the accuracy of pressure measurements in an EHD contact. Circuit and mathematical models of a thin-layer sensor and a measurement system were developed. It has been assumed that isolation layers of the sensor, deposited as SiOx (1 ≤ x ≤ 2) layers, have piezoelectric properties. The circuit model of the sensor contains a resistance, an electric capacitance, an inductance of a sensor’s circuit, and an ideal current source representing piezoelectric properties of isolating layers of the sensor. The circuit model of the measurement system forms a full measuring bridge with the thin-layer sensor in one of its branches. A derived equation for output voltage of the measurement bridge was used as a mathematical model of the measurement system. The investigations show that at inappropriate electric parameters of the measurement system, inappropriate shape of the sensor’s transducer and short transition time of the sensor through the contact zone, the capacitive, and piezoelectric effects have a significant impact on the accuracy of pressure measurement in the EHD contact. The transducer with an active part located along its connection edges (asymmetric transducer) and a transducer with the active part located in the middle of connections width (symmetric transducer) was tested. It was shown that in the case of the symmetric transducer, the pressure measurement signal change caused by the capacitive and piezoelectric effects, is much smaller than in the case of the asymmetric transducer.

Relationship Between Unsteady Flow, Pressure Fluctuations, and Noise in a Centrifugal Pump—Part B: Effects of Blade-Tongue Interactions

1995 ◽  
Vol 117 (1) ◽  
pp. 30-35 ◽  
Author(s):  
S. Chu ◽  
R. Dong ◽  
J. Katz
Keyword(s):  
Unsteady Flow ◽  
Centrifugal Pump ◽  
Pressure Difference ◽  
Pressure Fluctuations ◽  
Primary Sources ◽  
Pressure Measurements ◽  
Local Pressure ◽  
Pressure Distributions ◽  
Flow Pressure ◽  
Tip Of The Tongue

Maps of pressure distributions computed using PDV data, combined with noise and local pressure measurements, are used for identifying primary sources of noise in a centrifugal pump. In the vicinity of the impeller pressure minima occur around the blade and near a vortex train generated as a result of non-uniform outflux from the impeller. The pressure everywhere also varies depending on the orientation of the impeller relative to the tongue. Noise peaks are generated when the pressure difference across the tongue is maximum, probably due to tongue oscillations, and when the wake impinges on the tip of the tongue.

Time-Averaged Heat Transfer and Pressure Measurements and Comparison With Prediction for a Two-Stage Turbine

1994 ◽  
Vol 116 (1) ◽  
pp. 14-22 ◽  
Author(s):  
M. G. Dunn ◽  
J. Kim ◽  
K. C. Civinskas ◽  
R. J. Boyle
Keyword(s):  
Surface Pressure ◽  
Space Shuttle ◽  
Three Dimensional ◽  
Stanton Number ◽  
Navier Stokes ◽  
Pressure Measurements ◽  
Two Stage ◽  
Pressure Transducers ◽  
Pressure Distributions ◽  
Main Engine

Time-averaged Stanton number and surface-pressure distributions are reported for the first-stage vane row and the first-stage blade row of the Rocketdyne Space Shuttle Main Engine two-stage fuel-side turbine. These measurements were made at 10, 50, and 90 percent span on both the pressure and suction surfaces of the component. Stanton-number distributions are also reported for the second-stage vane at 50 percent span. A shock tube is used as a short-duration source of heated and pressurized air to which the turbine is subjected. Platinum thin-film gages are used to obtain the heat-flux measurements and miniature silicone-diaphragm pressure transducers are used to obtain the surface pressure measurements. The first-stage vane Stanton number distributions are compared with predictions obtained using a quasi-three dimensional Navier–Stokes solution and a version of STAN5. This same N–S technique was also used to obtain predictions for the first blade and the second vane.

scholarly journals Piezoelectric Properties of GaN Self-Organized Quantum Dots

1999 ◽  
Vol 4 (S1) ◽  
pp. 846-851 ◽  
Author(s):  
B. Daudin ◽  
F. Widmann ◽  
J. Simon ◽  
G. Feuillet ◽  
J. L. Rouvière ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Molecular Beam ◽  
Piezoelectric Properties ◽  
Radiative Lifetime ◽  
Average Height ◽  
Self Organized ◽  
Piezoelectric Effects ◽  
Bulk Gan ◽  
Piezoelectric Field ◽  
Large Quantum

It is demonstrated that GaN quantum dots with the wurtzite structure grown by molecular beam epitaxy on AlN exhibit optical properties which, depending on the size of the dots, may be dominated by piezoelectric effects. In "large" quantum dots with an average height and diameter of 4.1 and 17 nm, respectively, the photoluminescence peak is centered at 2.95 eV, nearly 0.5 eV below the bulk GaN bandgap, which is assigned to a piezoelectric field of 5.5 MV/cm present in the dots. The decay time of the photoluminescence was also measured. A comparison is carried out with theoretical calculation of the radiative lifetime.

Experiments and Modeling of the Hydraulic Resistance of In-Line Square Pin Fin Heat Sinks With Top By-Pass Flow

2003 ◽  
Author(s):  
Mario Urdaneta ◽  
Alfonso Ortega ◽  
Russel V. Westphal
Keyword(s):  
Static Pressure ◽  
Heat Sinks ◽  
Pressure Measurements ◽  
Pin Fin ◽  
Pressure Distributions ◽  
Full Development ◽  
Background Data ◽  
Physical Insight ◽  
Loss Coefficients ◽  
Insight Into

Extensive experiments were performed aimed at obtaining physical insight into the behavior of in-line pin fin heat sinks with pins of square cross-section. Detailed pressure measurements were made inside an array of square pins in order to isolate the inlet, developing, fully developed, and exit static pressure distributions as a function of row number. With this as background data, overall pressure drop was measured for a self-consistent set of aluminum heat sinks in side inlet side exit flow, with top clearance only. Pin heights of 12.5 mm, 17.5 mm, and 22.5 mm, pin pitch of 3.4 mm to 6.33 mm, and pin thickness of 1.5 mm, 2 mm and 2.5mm were evaluated. Base dimensions were kept fixed at 25 × 25 mm. In total, 20 aluminum heat sinks were evaluated. A “two-branch by-pass model” was developed, by allowing inviscid acceleration of the flow in the bypass section, and using pressure loss coefficients obtained under no bypass conditions in the heat sink section. The experimental data compared well to the proposed hydraulic models. Measurements in the array of pins showed that full development of the flow occurs after nine rows, thus indicating that none of the heat sinks tested could be characterized as fully-developed.

Flowfield and Pressure Measurements in a Rotating Two-Pass Duct With Staggered Rounded Ribs Skewed 45Degrees to the Flow

2004 ◽  
Vol 128 (2) ◽  
pp. 340-348 ◽  
Author(s):  
Tong-Miin Liou ◽  
Y. Sian Hwang ◽  
Yi-Chen Li
Keyword(s):  
Friction Factor ◽  
Pressure Coefficient ◽  
Operating Conditions ◽  
Friction Loss ◽  
Main Stream ◽  
Pressure Measurements ◽  
Height Ratio ◽  
Mean Velocity ◽  
Square Duct ◽  
Pressure Distributions

Laser-Doppler velocimetry and pressure measurements are presented of the local velocity and wall pressure distributions in a rotating two-pass square duct with staggered ribs placed on the leading and trailing walls at an angle of 45deg to the main stream. The ribs were square in cross section with the radii of rounds and fillets to rib height ratios of 0.33. The rib-height/duct-height ratio and the pitch/rib-height ratio were 0.136 and 10, respectively. The duct Reynolds number was 1×104 and rotation number Ro ranged from 0 to 0.2. Results are documented in terms of the evolutions of both main flow and cross-stream secondary flow, the distributions of the pressure coefficient, and the variation of friction factor with Ro. For CFD reference, the periodic fully developed flow condition is absent for the present length of the rotating passage roughened with staggered 45deg ribs. In addition, the relationships between the regional averaged Nusselt number, transverse and convective mean velocity component, and turbulent kinetic energy are addressed. Using these relationships the general superiority of heat transfer enhancement of the staggered 45deg ribs arrangement over the in-line one can be reasonably illustrated. Simple expressions are obtained to correlate the friction factor with Ro, which are lacking in the published literature for passages ribbed with staggered 45deg ribs. The staggered 45deg ribs are found to reduce the friction loss to about 88%±1% of the in-line 45deg ribs for the rotating passage under the same operating conditions. The respective contributions of the angled ribs and passage rotation on the passage friction loss are identified.

Pyroelectric and Piezoelectric Properties of Gan-Based Materials

1998 ◽  
Vol 537 ◽  
Author(s):  
M. S. Shur ◽  
A. D. Bykhovski ◽  
R. Gaska
Keyword(s):  
High Temperature ◽  
Piezoelectric Properties ◽  
Pyroelectric Coefficient ◽  
Heating Regime ◽  
Light Emitting ◽  
Polarization Effects ◽  
Light Emitting Devices ◽  
Uniform Sample ◽  
Piezoelectric Effects ◽  
Pyroelectric Detectors

AbstractWe review pyroelectric and piezoelectric properties of GaN-based materials. Pyroelectric effects in GaN have been studied in two different regimes: (i) uniform sample heating regime and (ii) under applied temperature gradient along the sample. The modeling results show that the pyroelectric coefficient, Pv, in GaN (for c-axis along the contacts) can reach 7x105 V/m-K (compared to Pv = 5x105 V/m-K for the best-known high temperature pyroelectric/piezoelectric material LiTaO3). This points to a high potential of GaN-based sensors for high temperature pyroelectronics. Piezoelectric effects strongly affect the performance of electronic and light-emitting devices based on III-N materials. Piezoelectrically induced charge in heterostructures can be as large as 3 to 4x1013 cm-2. Hence, strong lattice polarization effects provide unique possibilities for utilizing GaN-based materials in high temperature piezoelectronics and for their applications in pyroelectric detectors.

Physics of unsteady blunt-fin-induced shock wave/turbulent boundary layer interactions

1994 ◽  
Vol 273 ◽  
pp. 375-409 ◽  
Author(s):  
Leon Brusniak ◽  
David S. Dolling
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Time History ◽  
Separated Flow ◽  
Flow Region ◽  
Horseshoe Vortex ◽  
Wall Pressure ◽  
Pressure Measurements ◽  
Separation Shock ◽  
Pressure Distributions

Fluctuating wall-pressure measurements have been made on the centreline upstream of a blunt fin in a Mach 5 turbulent boundary layer. By examining the ensemble-averaged wall-pressure distributions for different separation shock foot positions, it has been shown that local fluctuating wall-pressure measurements are due to a distinct pressure distribution, [weierp ]i, which undergoes a stretching and flattening effect as its upstream boundary translates aperiodically between the upstream-influence and separation lines. The locations of the maxima and minima in the wall-pressure standard deviation can be accurately predicted using this distribution, providing quantitative confirmation of the model. This model also explains the observed cross-correlations and ensemble-average measurements within the interaction. Using the [weierp ]i model, wall-pressure signals from under the separated flow region were used to reproduce the position–time history of the separation shock foot. The unsteady behaviour of the primary horseshoe vortex and its relation to the unsteady separation shock is also described. The practical implications are that it may be possible to predict some of the unsteady aspects of the flowfield using mean wall-pressure distributions obtained from either computations or experiments; also, to minimize the fluctuating loads caused by the unsteadiness, flow control methods should focus on reducing the magnitude of the [weierp ]i gradient (∂[weierp ]i/∂x).

Steady and Unsteady Surface Pressure Distributions Around Rectangular Prisms With Sharp Edges at Reynolds Number Up to 2.5×106

2006 ◽  
Author(s):  
Annick D’Auteuil ◽  
Guy L. Larose
Keyword(s):  
Reynolds Number ◽  
Turbulent Flow ◽  
Surface Pressure ◽  
Angle Of Attack ◽  
Pressure Measurements ◽  
Oncoming Flow ◽  
Pressure Distributions ◽  
Unsteady Surface Pressure ◽  
Sharp Edges ◽  
Flow Reattachment

The commonly-held assumption that the aerodynamics of rectangular prisms with sharp edges are insensitive to Reynolds number is shown to have limitations. Flow reattachment on the top and/or bottom of the prisms can be related to Reynolds number, Re. Steady and unsteady surface pressure measurements were carried out on nine different rectangular prisms for Re from 0.3×106 to 2.5×106 at several angles of attack, in smooth and turbulent flow. It was observed that the reattachment was dependent on parameters such as fineness ratio, edge treatment, angle of attack, turbulence of the oncoming flow and Reynolds number. Permanent reattachment occurred for prisms with fineness ratio of 4 and fluctuating reattachment took place for rectangular prisms with fineness ratio as low as 2.

Pressure Measurements at the Tie-Ballast Interface in Railroad Tracks Using Granular Material Pressure Cells

2017 ◽  
Author(s):  
Qingjie Liu ◽  
Xiaoyan Lei ◽  
Jerry G. Rose ◽  
Macy L. Purcell
Keyword(s):  
Granular Material ◽  
Test Sequence ◽  
Test Machine ◽  
Pressure Measurements ◽  
Average Pressure ◽  
Tests And Measurements ◽  
Railroad Tracks ◽  
Pressure Distributions ◽  
Testing Sequence ◽  
Complete Revolution

It has been desirable for years to develop a reasonably simple, direct, accurate, and reliable method to measure pressure distributions in railroad trackbeds, especially the pressure magnitudes and distributions at the tie-ballast interface. In this study, specially-designed granular material pressure cells were used to measure pressure magnitudes and distributions. The cells were placed directly under the rail-tie intersection at the tie-ballast interface. Initially, a MTS test machine was used to conduct a series of laboratory tie-ballast box tests for a wide variation of ballast types and loading configurations. The adequacy of the cells for in-track measurements was verified with a series of very controlled laboratory tests and measurements using simulated trackbed sections and loading conditions. Excellent correlations were obtained comparing applied machine pressures and measured transferred cell pressures indicating that this type of pressure cell is suitable for in-track tie-ballast pressure measurements. This preliminary testing sequence is briefly described. A series of in-track wood tie tests were conducted on a yard lead track on a shortline railroad, Transkentucky Transportation, to optimize the in-track installation procedures and to obtain pressure measurements using repeated passes of low-speed locomotives and cars. A normalized pressure distribution was obtained by using metal shims when necessary to fill voids between the ties and pressure cells to insure continuous tie-ballast contact. This test sequence is presented and described. Additional in-track tests were conducted on Norfolk Southern Railway’s heavy tonnage concrete tie Class 4 mainline with train speeds of up to 64 km/h. Data was obtained for numerous passages of revenue trains over a period of several months for variable weights and types of locomotives and freight cars at typical train speeds. The average pressure intensities at the tie-ballast interface were acquired for six consecutive ties comprising a complete revolution of the wheels. This data is presented and the results discussed.

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