Transient Pressure Measurements by Recess-Mounted Transducers

2003 ◽  
Author(s):  
Jim C. P. Liou ◽  
Guohua Li
Keyword(s):  
Measurement System ◽  
Rise Time ◽  
Pressure Measurements ◽  
Transient Pressure ◽  
Source Pressure ◽  
Pressure Transducers ◽  
Transient Source ◽  
Gaseous Media ◽  
Type Pressure ◽  
General Method

Recess-mounted diaphragm-type pressure transducers are often used in measuring transient pressures. When the rise time of the source pressure is very fast, ringing of the transducer may occur. This study investigates the ringing of such a transducer numerically and experimentally for the purpose of developing a general method to recover transient source pressures. The approach is based on modeling the transient hydraulics of the measurement system. Favorable comparisons between the recovered pressure traces with those measured by a flush-mounted transducer were obtained. The proposed method makes recess-mounted transducers viable for measuring rapidly changing pressures in both liquid and gaseous media.

Correcting for Response Lag in Unsteady Pressure Measurements in Water

1993 ◽  
Vol 115 (4) ◽  
pp. 676-679 ◽  
Author(s):  
Rand N. Conger ◽  
B. R. Ramaprian
Keyword(s):  
Dynamic Response ◽  
Pressure Transducer ◽  
Water Channel ◽  
Inadequate Response ◽  
Pressure Measurements ◽  
Pressure Transducers ◽  
Pitching Airfoil ◽  
Unsteady Pressure ◽  
Unsteady Pressure Measurements ◽  
Type Pressure

There is not much information available on the use of diaphragm-type pressure transducers for the measurement of unsteady pressures in liquids. A procedure for measuring the dynamic response of a pressure transducer in such applications and correcting for its inadequate response is discussed in this report. An example of the successful use of this method to determine unsteady surface pressures on a pitching airfoil in a water channel is presented.

A Study of Bulk Modulus, Entrained Air, and Dynamic Pressure Measurements in Liquids

2016 ◽  
Vol 138 (10) ◽  
Author(s):  
Adam M. Hurst ◽  
Joe VanDeWeert
Keyword(s):  
Bulk Modulus ◽  
Frequency Response ◽  
Measurement System ◽  
Pressure Transducer ◽  
Dynamic Pressure ◽  
Pressure Measurements ◽  
Liquid Media ◽  
Pressure Transducers ◽  
Dynamic Pressure Measurements ◽  
Dissolved Air

Accurate static and dynamic pressure measurements in liquids, such as fuel, oil, and hydraulic fluid, are critical to the control and health monitoring of turbomachinery and aerospace systems. This work presents a theoretical and experimental study of the frequency response of pressure transducers and pressure measurement systems in liquid media. First, we theoretically predict the frequency response of pressure transducers based upon a lumped-parameter model. We then present a liquid-based dynamic pressure calibration test apparatus that validates this model by performing several critical measurements. This system first uses a vibrating liquid column to dynamically calibrate and experimentally determine the frequency response of a test pressure transducer, measurement system or geometry. Second, this calibration system experimentally extracts the bulk modulus of the fluid and the percent of entrained and/or dissolved air by volume. Bulk modulus is determined by measuring the speed of sound within the liquid and through static pressure loading while measuring the deflection of the liquid column. Bulk modulus and the entrained/dissolved gas content within the liquid greatly impact the observed frequency response of a pressure transducer or geometry. Gases, such as air, mixed or dissolved into a fluid can add substantial damping to the dynamic response of the fluid measurement system, which makes measurement of the bulk modulus and entrained and/or dissolved air critical for accurate measurement of the frequency response of a system when operating with a liquid media. All experimental results are compared to theoretical predictions.

Measurement of the Air Pressure for a Rotary Vane Compressor

2003 ◽  
Author(s):  
Yuan Mao Huang ◽  
Sheng An Yang
Keyword(s):  
Frequency Converter ◽  
Air Pressure ◽  
Cover Plate ◽  
Rotary Compressor ◽  
Compression Phase ◽  
Pressure Transducers ◽  
Compressor Rotor ◽  
Two Phases ◽  
Rotary Vane Compressor ◽  
Type Pressure

This study introduces an experimental method that can measure air pressures in the vane segments when a sliding-vane rotary compressor performs suction and compression phases in stable or unstable rotational speeds. When the air pressures of these two phases can be measured, the intake effect of the compressor’s inlet and the seal effect of the vane segments can be evaluated, respectively. Because a frequency converter provides unstable rotational speeds when it controls rotational speeds of a motor with a compressor, an encoder mounted on the output shaft of the motor was applied to record the angular location of the compressor rotor. Two strain gauge type pressure transducers were inserted into the cover plate of the compressor to measure air pressures in the vane segments. Comparing the signals of the encoder with pressure transducers, the air pressures in completions of suction and compression phases could be determined in stable or unstable rotational speeds. The air pressures when the compressor performed suction and compression phases were 99.5 kPa and 153 kPa, respectively, in 1400 rpm. The air pressure when the compressor performed suction phase decreased with the rotational speed faster than 800 rpm. The size or shape of the inlet port of the compressor should be enlarged or modified to provide the suction air pressure without dropping too much. The designed air pressure when the compressor performed compression phase was 244 kPa in 140 rpm, the manufacture precision of the compressor should be increased to decrease leakage.

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.

Investigation of Squeeze Film Damper Forces Produced by Circular Centered Orbits

1978 ◽  
Vol 100 (1) ◽  
pp. 15-21 ◽  
Author(s):  
E. Feder ◽  
P. N. Bansal ◽  
A. Blanco
Keyword(s):  
Aircraft Engine ◽  
Analytical Investigation ◽  
Operating Conditions ◽  
Squeeze Film ◽  
Oil Viscosity ◽  
Pressure Transducers ◽  
Pressure Distributions ◽  
Pressure Profiles ◽  
Force Components ◽  
Type Pressure

This paper presents the results of an experimental and analytical investigation of the dynamic forces generated by a squeeze film bearing damper constrained to move in circular centered orbits. These orbits were mechanically produced in a specially designed, end sealed, test rig. Aircraft engine damper geometry and operating conditions were simulated. The effect of journal speed, oil viscosity, inlet pressure, and eccentricity ratio on the damper performance was studied. The pressure distributions about the journal were measured for each test condition by high-response diaphragm-type pressure transducers. These pressure profiles were numerically integrated to determine the force components of the squeeze film. Experimental results were compared to an analysis which is summarized in this paper and included the effects of inlet and cavitation pressures. The “long bearing theory” was found to be reasonably accurate in predicting the shape and magnitude of the pressure distribution. Considerable emphasis was directed to the study of the circumferential pressure distributions between 180 deg and 360 deg since aircraft engine dampers generally operate in this region. For the cavitated film (i.e., pressure distributions less than 360 deg), accurate prediction of the damper forces was found to be critically dependent on the effect of inlet and cavitation pressures.

Ventilatory modes and mechanics of the hedgehog skate (Leucoraja erinacea): testing the continuous flow model

2001 ◽  
Vol 204 (9) ◽  
pp. 1577-1587 ◽  
Author(s):  
A.P. Summers ◽  
L.A. Ferry-Graham
Keyword(s):  
System Design ◽  
Continuous Flow ◽  
Flow Model ◽  
Pressure Measurements ◽  
Suction Pump ◽  
Experimental Animals ◽  
Pressure Transducers ◽  
Oropharyngeal Cavity ◽  
Elasmobranch Fishes ◽  
System 1

The movement of water across the gills of non-ram-ventilating fishes involves the action of two pumps: a pressure pump that pushes water across the gills from the oropharyngeal to the parabranchial cavity, and a suction pump that draws water across the gills from the oropharyngeal into the parabranchial cavity. Together, the two are thought to keep water flowing continuously anteroposteriorly through the head of the respiring animal. However, there is evidence that the pressure and suction pumps do not always work in perfect phase in elasmobranch fishes, leading to periods of higher pressure in the parabranchial than in the oropharyngeal cavity. We investigated the existence and consequence of such pressure reversals in the hedgehog skate Leucoraja erinacea using pressure transducers, sonomicrometry and flow visualization including internal visualization using endoscopy. We noted four patterns of respiration in the experimental skates distinguished by the flow pattern at the three openings into the respiratory system: (1) in through the spiracle only, (2) in through the mouth + spiracle, (3) in through the mouth only, and (4) the mouth held open throughout the respiratory cycle. The first two were by far the dominant modes recorded from experimental animals. We determined that pressure reversals exist in the hedgehog skate, and that the gill bars adducted during such pressure reversals. Direct observation confirmed that these pressure reversals do correspond to pulsatile flow across the gills. During mouth+spiracle ventilation the flow completely reversed direction, flowing from the parabranchial chambers back across the gills and into the oropharyngeal cavity. Finally, we addressed the utility of sonomicrometry as a technique for determining kinematics in aquatic animals. Despite some problems involving errors inherent to the system design, we found the technique useful for complementing such techniques as pressure measurements and endoscopy.

scholarly journals An Investigation of Surge in a High-Speed Centrifugal Compressor Using Digital PIV

2000 ◽  
Vol 123 (2) ◽  
pp. 418-428 ◽  
Author(s):  
Mark P. Wernet ◽  
Michelle M. Bright ◽  
Gary J. Skoch
Keyword(s):  
Flow Field ◽  
Centrifugal Compressor ◽  
High Speed ◽  
Transient Flow ◽  
Dynamic Pressure ◽  
Rotating Stall ◽  
Transient Pressure ◽  
Pressure Transducers ◽  
Stable Operating ◽  
Particle Imaging

Compressor stall is a catastrophic breakdown of the flow in a compressor, which can lead to a loss of engine power, large pressure transients in the inlet/nacelle, and engine flameout. The implementation of active or passive strategies for controlling rotating stall and surge can significantly extend the stable operating range of a compressor without substantially sacrificing performance. It is crucial to identify the dynamic changes occurring in the flow field prior to rotating stall and surge in order to control these events successfully. Generally, pressure transducer measurements are made to capture the transient response of a compressor prior to rotating stall. In this investigation, Digital Particle Imaging Velocimetry (DPIV) is used in conjunction with dynamic pressure transducers to capture transient velocity and pressure measurements simultaneously in the nonstationary flow field during compressor surge. DPIV is an instantaneous, planar measurement technique that is ideally suited for studying transient flow phenomena in high-speed turbomachinery and has been used previously to map the stable operating point flow field in the diffuser of a high-speed centrifugal compressor. Through the acquisition of both DPIV images and transient pressure data, the time evolution of the unsteady flow during surge is revealed.

Measurement of rise times of seismic pulses in rock

Geophysics ◽  
1982 ◽  
Vol 47 (7) ◽  
pp. 1047-1058 ◽  
Author(s):  
D. P. Blair
Keyword(s):  
Measurement System ◽  
Rise Time ◽  
Broad Band ◽  
General System ◽  
Large Contribution ◽  
Measurement Systems ◽  
Numerical Assessment ◽  
The Given ◽  
Impulsive Source ◽  
System Transfer Function

Rise times for seismic pulses in rock are discussed for both nearly constant Q (NCQ) and constant Q (CQ) theories of pulse attenuation. The frequency content of the NCQ pulse is examined in detail. Frequencies close to the megahertz region are shown to have a significant contribution to the rise time of pulses a meter or so from an impulsive source. Hence, the measurement of such rise times is significantly influenced by the frequency response of the measurement system itself. In giving a numerical assessment of the system influence, I propose a model for a general system transfer function. The effect of such a system on the measurement of rise times of seismic pulses is then obtained by convolving the system impulse response with the given seismic pulse. For even the most broad‐band seismic measurement systems presently available, rise time measurements made especially within 10 m or so of an impulsive source show a large contribution dependent upon the rise time of the measurement system itself.

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