scholarly journals Flutter Spectral Measurements Using Stationary Pressure Transducers

1981 ◽  
Vol 103 (2) ◽  
pp. 461-467 ◽  
Author(s):  
A. P. Kurkov
Keyword(s):  
Pressure Transducer ◽  
Static Pressure ◽  
Spectral Measurements ◽  
Pressure Data ◽  
Difference Spectra ◽  
Blade Vibration ◽  
Pressure Transducers ◽  
Displacement Spectra ◽  
Optical Displacement ◽  
Engine Order

Engine-order sampling was used to eliminate the integral harmonics from the flutter spectra corresponding to a case-mounted static pressure transducer. From the optical displacement data it was demonstrated that blade-order sampling of pressure data can yield erroneous results because of the interference caused by blade vibration. Two methods are presented that effectively eliminate this interference and yield the blade-pressure-difference spectra. The phase difference between the differential-pressure and displacement spectra was evaluated.

Measurement of Two-Dimensional Periodic Flow With a Cobra Probe

1973 ◽  
Vol 95 (2) ◽  
pp. 295-299 ◽  
Author(s):  
Y. Senoo ◽  
Y. Kita ◽  
K. Ookuma
Keyword(s):  
Pressure Transducer ◽  
Static Pressure ◽  
Flow Characteristics ◽  
Periodic Flow ◽  
Two Dimensional ◽  
Unsteady State ◽  
Pump Impeller ◽  
Pressure Transducers ◽  
Probe System ◽  
Similarity Law

Three semiconductor pressure transducers were inserted into a cobra probe to measure instantaneous condition of flow at the exit of a pump impeller. As it was difficult to calibrate a probe in a two-dimensional periodic flow which was similar to the periodic flow to be measured, the authors used the probe assuming that the steady flow characteristics were valid and examined the results in several ways. The results at different pump speeds satisfied the similarity law of flow from the impeller, and it was concluded that the time response of the probe and pressure transducer system was satisfactory. Almost identical results were obtained regardless of the orientation of the probe, and it was concluded that the calibration curve at steady state was applicable to the unsteady state. Finally, the static pressure calculated from the probe output agreed with the wall pressure which was directly measured with a semiconductor pressure transducer. The authors believe that the three steps are sufficient to prove that the results obtained with the probe are reliable and the probe system is suitable for measurement of periodic flow at the exit of impeller of a pump.

scholarly journals Does temperature affect the accuracy of vented pressure transducer in fine-scale water level measurement?

2015 ◽  
Vol 4 (1) ◽  
pp. 65-73 ◽  
Author(s):  
Z. Liu ◽  
C. W. Higgins
Keyword(s):  
Water Level ◽  
Pressure Transducer ◽  
Performance Test ◽  
Thermal Fluctuations ◽  
Field Conditions ◽  
Digital Data ◽  
Water Level Fluctuations ◽  
Fine Scale ◽  
Data Logger ◽  
Pressure Transducers

Abstract. Submersible pressure transducers have been utilized for collecting water level data since the early 1960s. Together with a digital data logger, it is a convenient way to record water level fluctuations for long-term monitoring. Despite the wide use of pressure transducers for water level monitoring, little has been reported regarding their accuracy and performance under field conditions. The effects of temperature fluctuations on the output of vented pressure transducers were considered in this study. The pressure transducers were tested under both laboratory and field conditions. The results of this study indicate that temperature fluctuation has a strong effect on the transducer output. Rapid changes in temperature introduce noise and fluctuations in the water level readings under a constant hydraulic head while the absolute temperature is also related to sensor errors. The former is attributed to venting and the latter is attributed to temperature compensation effects in the strain gauges. Individual pressure transducers responded differently to the thermal fluctuations in the same testing environment. In the field of surface hydrology, especially when monitoring fine-scale water level fluctuations, ignoring or failing to compensate for the temperature effect can introduce considerable error into pressure transducer readings. It is recommended that a performance test for the pressure transducer is conducted before field deployment.

scholarly journals Friction Damper Optimisation: Simulation of Rainbow Tests

1999 ◽  
Author(s):  
Kenan Y. Sanliturk ◽  
David J. Ewins ◽  
Robert Elliott ◽  
Jeff S. Green
Keyword(s):  
Harmonic Balance Method ◽  
Lumped Parameter Model ◽  
Friction Damper ◽  
Blade Vibration ◽  
Friction Dampers ◽  
Lumped Parameter ◽  
Engine Order ◽  
Resonance Response ◽  
Theoretical Predictions ◽  
Different Characteristics

Friction dampers have been used to reduce turbine blade vibration levels for a considerable period of time. However, optimal design of these dampers has been quite difficult due both to a lack of adequate theoretical predictions and to difficulties in conducting reliable experiments. One of the difficulties of damper weight optimisation via the experimental route has been the inevitable effects of mistuning. Also, conducting separate experiments for different damper weights involves excessive cost. Therefore, current practice in the turbomachinery industry has been to conduct so-called ‘rainbow tests’ where friction dampers with different weights are placed between blades with a predefined configuration. However, it has been observed that some rainbow test results have been difficult to interpret and have been inconclusive for determining the optimum damper weight for a given bladed-disc assembly. A new method of analysis — a combination of Harmonic Balance Method and structural modification approaches — is presented in this paper for the analysis of structures with friction interfaces and the method is applied to search for qualitative answers about the so-called ‘rainbow tests’ in turbomachinery applications. A simple lumped-parameter model of a bladed-disc model was used and different damper weights were modelled using friction elements with different characteristics. Resonance response levels were obtained for bladed discs with various numbers of blades under various engine-order excitations. It was found that rainbow tests, where friction dampers with different weights are used on the same bladed-disc assembly, can be used to find the optimum damper weight if the mode of vibration concerned has weak blade-to-blade coupling (the case where the disc is almost rigid and blades vibrate almost independently from each other). Otherwise, it is very difficult to draw any reliable conclusion from such expensive experiments.

scholarly journals Assessment of Conformational Changes in Low-Sulphur S-Carboxymethylkerateine from Wool

1967 ◽  
Vol 20 (4) ◽  
pp. 827 ◽  
Author(s):  
GM Bhatnagar ◽  
WG Crewther
Keyword(s):  
Absorption Spectrum ◽  
Conformational Changes ◽  
Guanidine Hydrochloride ◽  
Ultraviolet Absorption Spectrum ◽  
Spectral Measurements ◽  
Characteristic Difference ◽  
Concentrated Solutions ◽  
Difference Spectra ◽  
The Difference ◽  
Negative Difference

The effects of urea and guanidine hydrochloride on the ultraviolet absorption spectrum of the low-sulphur S-carboxymethylkerateine fraction of wool have been measured. In concentrated solutions of urea characteristic difference spectra were obtained with maxima of negative absorbance at 288, 280, and 240 miL. The addition of guanidine hydrochloride or an increase in temperature gave similar negative difference maxima at the higher wavelengths. Calculation of the extent of unfolding of the protein chains from the difference in absorbance at all three maxima showed that the unfolding was 50% complete at a urea concentration of about 1� 8M whereas a urea concep.tration of about 4� 3M was required to decrease the helix content by 50%. Similar measurements on components 7 and 8, the two major constituents of SCMKA, showed that a 50% decrease in helix content was obtained with 2�8M and O� 8M urea respectively whereas the corresponding values for 50 % unfolding assessed from difference spectral measurements were 2� 2M and 1� 2M urea respectively. It is suggested that the helical regions of components 7 and 8 aggregate specifically and that spectral measurements relate largely to non-helical portions of the chains.

A Novel Approach to Surge Control: High-Frequency Pressure Variance As an Indicator of Impending Surge in Centrifugal Compressors

2018 ◽  
Author(s):  
Meera Day Towler ◽  
Tim Allison ◽  
Paul Krueger ◽  
Karl Wygant
Keyword(s):  
High Speed ◽  
Fast Response ◽  
Time Signal ◽  
Multiple Time ◽  
Pressure Data ◽  
Pressure Transducers ◽  
Surge Margin ◽  
Novel Approach ◽  
Surge Control ◽  
Response Pressure

This investigation studies fast-response pressure measurements as an indicator of the onset of surge in a single-stage centrifugal compressor. The objective is to determine an online monitoring approach for surge control that does not rely on surge margin relative to maps from predictions or factory testing. Fast-response pressure transducers are installed in the suction piping, inducer, diffuser, and discharge piping. A speed line is mapped, and high-speed pressure data are collected across the compressor map. The compressor is driven into surge several times to collect pressure data between during surge and between surge events. Following testing, these data are post-processed via filtration and statistical analyses. It is determined that, when taken together, the mean and range of the standard deviation of the time signal for multiple time steps can be used to determine whether the compressor’s operating point is approaching surge for the conditions tested.

On the Use of Fast-Response Pressure Transducers in a Common-Rail Diesel Injection System

2006 ◽  
Author(s):  
R. Amirante ◽  
L. A. Catalano ◽  
A. Dadone ◽  
V. Lombardo
Keyword(s):  
Pressure Transducer ◽  
Single Injection ◽  
Electric Circuit ◽  
Fast Response ◽  
Common Rail ◽  
Injection System ◽  
Pressure Transducers ◽  
Multiple Injections ◽  
Diesel Injection ◽  
Response Pressure

The aim of this paper is to investigate the use of fast-response pressure transducers for measuring the instantaneous pressure in different sections of a common-rail diesel injection system, both for a single injection and for multiple injections. The influence of the pressure transducer onto the measured pressure is evaluated numerically by comparing the pressure history computed without the pressure transducer and that computed with the presence, and thus with the disturbance, of this sensor. A new electric circuit is proposed in substitution of the standard electronic central unit, which allows to modify the injection parameters and to perform injections on a test rig, as done in the automotive applications. Experimental results are provided both for a single injection and for multiple injections, to demonstrate the capabilities of the proposed test bench for the unijet injectors.

Experimental Investigation of Surge Phenomena in a Transonic Centrifugal Compressor

2019 ◽  
Author(s):  
Sasuga Ito ◽  
Masato Furukawa ◽  
Satoshi Gunjishima ◽  
Hiroki Usuki ◽  
Takafumi Ota ◽  
...  
Keyword(s):  
Unsteady Flow ◽  
Centrifugal Compressor ◽  
Static Pressure ◽  
High Response ◽  
Low Flow ◽  
Pipeline System ◽  
Flow Phenomenon ◽  
Pressure Transducers ◽  
Transonic Centrifugal Compressor ◽  
Response Pressure

Abstract Surge is an unsteady flow phenomenon occurring at low flow rates in the pipeline system including compressors. The surge is a phenomenon that must be avoided because of the danger in the operation: the pipeline equipment can be damaged or the operation cannot be continued. Experimental work is required not only to understand the unsteady behavior but to also validate the CFD used for more localized analysis and development of the understanding of the flow phenomena when operating near surge. Nevertheless, there are still many unclear points not only about the flow phenomenon at the inception of the surge which is important for the prediction of the surge but also about the surge behavior itself. Especially, as for the surge occurring in transonic centrifugal compressors, there are currently few experimental research cases due to the difficulty of the unsteady measurement. In this research, we measured the time variations in pressure and flow rate in a transonic centrifugal compressor for a vehicle turbocharger which consists of an impeller, vaneless diffuser and scroll. In the experiments, the measurement pipes were set upstream and downstream of the compressor and the velocity and the wall static pressure were measured with an I-type hot wire probe and high response pressure transducers, respectively. In addition, to investigate the process and the occurrence point of the back flow in surge, the wall static pressure was measured by means of high response pressure transducers which were mounted on the shroud upstream of the impeller and the diffuser hub at the two-circumferential positions, respectively. As the result of the experiments, the unsteady flow process during the mild and deep surges was measured and the inception of deep surge was clarified.

Pressure-Probe Interference in a Vortex Flow

1978 ◽  
Vol 5 (2) ◽  
pp. 106-110
Author(s):  
O.O. Mojola
Keyword(s):  
Vortex Flow ◽  
Static Pressure ◽  
Vertical Wall ◽  
Three Dimensional ◽  
Flow Region ◽  
Pressure Probe ◽  
Pressure Data ◽  
Pressure Sensing ◽  
Recirculation Flow ◽  
Made In

This paper examines the sensitivity of vortex-flows to disturbances arising from the insertion of conventional pressure-sensing probes into the flows. With a wide variety of pitot-tubes, static-pressure probes, and transverse-cylinder yawmeters, measurements were made in the vortex (recirculation) flow region of a separated, three-dimensional, turbulent boundary layer upstream of a vertical wall. The measurements, which included both local and surface pressure data, have been analysed to reveal how the shape, size, and alignment of probes independently and collectively contribute to the probe interference.

Dynamic characterisation of pressure transducers using shock tube methods

2019 ◽  
Vol 42 (4) ◽  
pp. 743-748
Author(s):  
Andy J Knott ◽  
Ian A Robinson
Keyword(s):  
Dynamic Response ◽  
Shock Tube ◽  
Significant Variation ◽  
Pressure Transducer ◽  
Ideal Gas ◽  
Pressure Transducers ◽  
Pressure Step ◽  
Instantaneous Pressure

This paper describes the characterisation of the dynamic response of a range of pressure transducer systems. The transducers were subjected to virtually instantaneous pressure step inputs in the National Physical Laboratory’s shock tube facilities. The magnitudes of these pressure steps were derived from ideal gas theory, with prior commissioning tests having been performed to demonstrate the theory’s validity in this application. The results demonstrate a significant variation in response obtained from various combinations of transducer, instrumentation settings, and mounting arrangement.

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