scholarly journals Cavitation Inception in Spool Valves

1981 ◽  
Vol 103 (4) ◽  
pp. 564-575 ◽  
Author(s):  
C. Samuel Martin ◽  
H. Medlarz ◽  
D. C. Wiggert ◽  
C. Brennen
Keyword(s):  
Reynolds Number ◽  
Hydraulic Systems ◽  
Cavitation Inception ◽  
Pressure Transducers ◽  
High Frequency Response ◽  
Annular Jet ◽  
Directional Control ◽  
Valve Opening ◽  
Response Pressure ◽  
Spool Valves

Cavitation has been investigated in directional control valves in order to identify damage mechanisms characteristic of components of aircraft hydraulic systems. Tests have been conducted in a representative metal spool valve and in a model three times larger. Data taken under noncavitating conditions with both valves showed that the position of the high-velocity annular jet shifts orientation, depending upon valve opening and Reynolds number. By means of high-frequency response pressure transducers strategically placed in the valve chamber cavitation could be sensed by the correlation of noise with a cavitation index. The onset of cavitation can be detected by comparing energy spectra for a fixed valve opening and a constant discharge. Another sensitive indicator of cavitation inception is the ratio of cavitating to noncavitating spectral densities. The incipient cavitation number as defined in this investigation is correlated with the Reynolds number for both valves.

Experimental Study of Interactions of Shock Wave With Free-Stream Turbulence

1994 ◽  
Vol 116 (4) ◽  
pp. 763-769 ◽  
Author(s):  
A. Honkan ◽  
C. B. Watkins ◽  
J. Andreopoulos
Keyword(s):  
Shock Wave ◽  
Free Stream ◽  
Length Scale ◽  
Pressure Transducers ◽  
Free Stream Turbulence ◽  
High Frequency Response ◽  
Reflected Shock ◽  
Response Pressure ◽  
Decaying Turbulence ◽  
Large Eddies

Phenomena related to turbulence interactions with shock waves have been studied in detail. The present investigation is focused on interactions of a normal shock wave with homogeneous/grid-generated turbulence. When a shock wave formed in a shock-tube is passed through a grid, the induced flow behind the shock has the features of a compressible flow with free-stream turbulence. The decaying turbulence is subjected to an interaction with the reflected shock traveling in the opposite direction. Data were sampled simultaneously from four channels of high frequency response pressure transducers and dual hot-wires probes. A cold-wire was used to provide instantaneous total temperature measurements while a single hot-wire provided instantaneous mass flux measurements. Amplification of velocity and temperature fluctuations and dissipative length scales has been found in all experiments. Velocity fluctuations of large eddies are amplified more than the fluctuations of small eddies. The dissipative length scale, however, of the large eddies is amplified less than the length scale of the small eddies.

Wall-vorticity flux dynamics in a two-dimensional turbulent boundary layer

1996 ◽  
Vol 309 ◽  
pp. 45-84 ◽  
Author(s):  
J. Andreopoulos ◽  
J. H. Agui
Keyword(s):  
Boundary Layer ◽  
Viscous Force ◽  
Flux Dynamics ◽  
Pressure Transducers ◽  
High Frequency Response ◽  
Wall Structures ◽  
Response Pressure ◽  
Vorticity Flux ◽  
Low Amplitude ◽  
Physical Phenomena

Four high-frequency-response pressure transducers with 10 viscous units resolution each have been used to obtain simultaneously the fluctuating pressure gradients at the wall of a zero-pressure-gradient boundary layer and then to compute the vorticity flux away from the wall. Since the viscous force on an element of incompressible fluid is determined by the local vorticity gradients, understanding of their dynamical characteristics is essential in identifying the turbulent structure. Extremely high and low amplitudes of both vorticity gradients have been observed which contribute significantly to their statistics although they have low probability of appearance. The r.m.s. of the vorticity flux when scaled with inner wall variables depends very strongly on the Reynolds number, indicating a breakdown of this type of scaling. The application of a small threshold to the data indicated two preferential directions of the vorticity flux vector. An attempt has been made to identify these high- and low-amplitude signals with physical phenomena associated with bursting-sweep processes. Vortical structures carrying bipolar vorticity are the dominant wall structures which are associated with the violent events characterized by large fluctuations of vorticity flux.

scholarly journals Effect of Wind Tunnel Acoustic Modes on Linear Oscillating Cascade Aerodynamics

1993 ◽  
Author(s):  
Daniel H. Buffum ◽  
Sanford Fleeter
Keyword(s):  
Wind Tunnel ◽  
Unsteady Aerodynamics ◽  
Wave Mode ◽  
Influence Coefficient ◽  
Airfoil Surface ◽  
Pressure Transducers ◽  
Acoustic Modes ◽  
High Frequency Response ◽  
Response Pressure ◽  
Acoustic Treatment

The aerodynamics of a biconvex airfoil cascade oscillating in torsion is investigated using the unsteady aerodynamic influence coefficient technique. For subsonic flow and reduced frequencies as large as 0.9, airfoil surface unsteady pressures resulting from oscillation of one of the airfoils are measured using flush-mounted high-frequency-response pressure transducers. The influence coefficient data are examined in detail and then used to predict the unsteady aerodynamics of a cascade oscillating at various interblade phase angles. These results are correlated with experimental data obtained in the traveling-wave mode of oscillation and linearized analysis predictions. It is found that the unsteady pressure disturbances created by an oscillating airfoil excite wind tunnel acoustic modes which have detrimental effects on the experimental results. Acoustic treatment is proposed to rectify this problem.

scholarly journals Experimental Methods Applied in a Study of Stall Flutter in an Axial Flow Fan

2004 ◽  
Vol 11 (5-6) ◽  
pp. 597-613 ◽  
Author(s):  
John D. Gill ◽  
Vincent R. Capece ◽  
Ronald B. Fost
Keyword(s):  
Experimental Data ◽  
Dynamic Pressure ◽  
Axial Flow ◽  
Leading Edge ◽  
Axial Flow Fan ◽  
Pressure Transducers ◽  
High Frequency Response ◽  
Stall Flutter ◽  
Response Pressure ◽  
Flutter Testing

Flutter testing is an integral part of aircraft gas turbine engine development. In typical flutter testing blade mounted sensors in the form of strain gages and casing mounted sensors in the form of light probes (NSMS) are used. Casing mounted sensors have the advantage of being non-intrusive and can detect the vibratory response of each rotating blade. Other types of casing mounted sensors can also be used to detect flutter of rotating blades. In this investigation casing mounted high frequency response pressure transducers are used to characterize the part-speed stall flutter response of a single stage unshrouded axial-flow fan. These dynamic pressure transducers are evenly spaced around the circumference at a constant axial location upstream of the fan blade leading edge plane. The pre-recorded experimental data at 70% corrected speed is analyzed for the case where the fan is back-pressured into the stall flutter zone. The experimental data is analyzed using two probe and multi-probe techniques. The analysis techniques for each method are presented. Results from these two analysis methods indicate that flutter occurred at a frequency of 411 Hz with a dominant nodal diameter of 2. The multi-probe analysis technique is a valuable method that can be used to investigate the initiation of flutter in turbomachines.

Spatial Correlation Based Stall Inception Analysis

2007 ◽  
Author(s):  
Joshua D. Cameron ◽  
Scott C. Morris
Keyword(s):  
Spatial Correlation ◽  
High Speed ◽  
Axial Compressor ◽  
Rotating Stall ◽  
Fourier Decomposition ◽  
Stall Inception ◽  
Pressure Transducers ◽  
High Frequency Response ◽  
Wide Range ◽  
Response Pressure

Investigations of stall inception and compressor pre-stall behavior have used a variety of techniques to make inferences about the mechanisms of rotating stall inception. Many of these techniques utilized data from arrays of circumferentially spaced hot-wires or high frequency response pressure transducers. This paper presents results from the application of several typical analysis techniques to the interpretation of unsteady casing pressure measurements recorded during two representative stall event in a high-speed axial compressor stage. Results from visual pressure trace inspection, spatial Fourier decomposition, wavelet filtering, and traveling wave energy techniques are presented and compared. The effects of measurement and analysis parameters are also briefly discussed. A new analysis technique based on windowed two-point spatial correlation between adjacent stall inception sensors is described. The method was found to provide both spatial and temporal information about rotating features in the compressor flow and is insensitive to low pass filtering and parameter selection over a wide range of values. It was also found to be valuable for analysis of both pre-stall and stall inception behavior.

Compressibility Effects in Turbulent Subsonic Jets

2003 ◽  
Author(s):  
Zhexuan Wang ◽  
Yiannis Andreopoulos
Keyword(s):  
Mach Number ◽  
Pressure Fluctuations ◽  
Turbulent Jets ◽  
Spreading Rate ◽  
Jet Flows ◽  
Mean Velocity ◽  
Pressure Transducers ◽  
High Frequency Response ◽  
Mach Numbers ◽  
Response Pressure

The behavior of compressible turbulent jets issuing in still air in the absence of shock waves has been investigated at three different subsonic Mach numbers, 0.3, 0.6 and 0.9. Helium, nitrogen and krypton gases were used to generate the jet flows and investigate the density effects on the structure of turbulence. Particle Image Velocimetry and high-frequency response pressure transducers were used to obtain velocity, Mach number inside the flow field. The decay of the Mach number at the centerline of the axisymmetric jets increases with increasing the initial Mach number at the exit of the flow for all jets. The decay of mean velocity at the centerline of the jets is also higher at higher exit Mach numbers. However, the velocity non-dimensionalized by the exit velocity seems to decrease faster at low exit Mach numbers suggesting a reduced mixing with increasing the exit flow Mach numbers. Helium jets were found to have the largest spreading rate among the three different gas jets used in the present investigation, while krypton had the lowest spreading rate. Total pressure fluctuations appear to decrease with increasing exit flow Mach numbers. Unusually high turbulence intensities were measured in helium jets issuing in still air.

Influence of Flow Coefficient, Stagger Angle, and Tip Clearance on Tip Vortex in Axial Compressors

2006 ◽  
Vol 128 (6) ◽  
pp. 1274-1280 ◽  
Author(s):  
Yong Sang Yoon ◽  
Seung Jin Song ◽  
Hyoun-Woo Shin
Keyword(s):  
Pressure Fluctuations ◽  
Tip Clearance ◽  
Flow Coefficient ◽  
Tip Vortex ◽  
Time Resolved ◽  
Pressure Transducers ◽  
High Frequency Response ◽  
Response Pressure ◽  
Casing Pressure ◽  
Stagger Angle

Experiments have been performed on the low speed research compressor (LSRC) at General Electric Aircraft Engines to investigate the effects of flow coefficient, stagger angle, and tip clearance on tip vortex. Time resolved casing pressure distributions over the third stage rotor have been acquired with high-frequency-response pressure transducers. Also, tip vortex strength and trajectory have been estimated from the casing pressure fluctuations which have been obtained simultaneously from various axial locations. As flow coefficient decreases, tip vortex gets strengthened and migrates upstream. The stagger angle increase weakens the tip vortex and moves it downstream slightly because the blade loading is decreased. However, tip leakage vortex is influenced mainly by tip clearance, and there exists a “critical” tip clearance which determines the type of tip vortex trajectory (“straight” or “kinked”). As predicted by others, tip vortex gets strengthened with increasing tip clearance. However, unlike the predictions, the tip vortex trajectory moves upstream with increasing tip clearance. Furthermore, with tip clearance above a “critical” value, the tip vortex trajectory is no longer straight but shows a kink in the passage.

Development of a New Generation of Independent Metering Valve Circuit for Hydraulic Boom Cylinder Control

2015 ◽  
Vol 9 (2) ◽  
pp. 143-152
Author(s):  
Mashruk Ahamad ◽  
◽  
Quang-Truong Dinh ◽  
Syed Abu Nahian ◽  
Kyoung-Kwan Ahn ◽  
...  
Keyword(s):  
Degrees Of Freedom ◽  
Control Valve ◽  
Hydraulic Systems ◽  
Large Power ◽  
Directional Control ◽  
Hydraulic Equipment ◽  
Pressure Compensation ◽  
Primary Focus ◽  
Spool Valves ◽  
New Generation

Recent research on hydraulic systems has mainly focused on energy saving. This is because the efficiency of hydraulic systems is very low even though they have large power-to-size ratios. In mobile hydraulic equipment, conventional hydraulic spool valves with pressure compensators have already been replaced by valve assemblies with four-valve independent metering with electronically controlled pressure compensation. The independent metering concept and microprocessor control have much more potential to save more energy than conventional proportional valve control because of the increased controllability of the system. The primary focus of this study is to reduce the number of Independent Metering Valves (IMV) by introducing one directional control valve. This new model offers two degrees of freedom, i.e., controlling velocity and pressure, just as in conventional IMVs. In the system described here, two of the three independent valves are active during metering. In this paper, the theory behind a new method of flow control based upon load feedback is presented for two of the five distinct metering modes, and its performance is investigated and compared to that of a conventional IMV configuration.

scholarly journals Effect of Wind Tunnel Acoustic Modes on Linear Oscillating Cascade Aerodynamics

1994 ◽  
Vol 116 (3) ◽  
pp. 513-524 ◽  
Author(s):  
D. H. Buffum ◽  
S. Fleeter
Keyword(s):  
Wind Tunnel ◽  
Unsteady Aerodynamics ◽  
Wave Mode ◽  
Influence Coefficient ◽  
Airfoil Surface ◽  
Pressure Transducers ◽  
Acoustic Modes ◽  
High Frequency Response ◽  
Response Pressure ◽  
Acoustic Treatment

The aerodynamics of a biconvex airfoil cascade oscillating in torsion is investigated using the unsteady aerodynamic influence coefficient technique. For subsonic flow and reduced frequencies as large as 0.9, airfoil surface unsteady pressures resulting from oscillation of one of the airfoils are measured using flush-mounted high-frequency-response pressure transducers. The influence coefficient data are examined in detail and then used to predict the unsteady aerodynamics of a cascade oscillating at various interblade phase angles. These results are correlated with experimental data obtained in the traveling-wave mode of oscillation and linearized analysis predictions. It is found that the unsteady pressure disturbances created by an oscillating airfoil excite wind tunnel acoustic modes, which have detrimental effects on the experimental results. Acoustic treatment is proposed to rectify this problem.

scholarly journals Characterization of Cavitation Fields From Measured Pressure Signals of Cavitating Jets and Ultrasonic Horns

2013 ◽  
Vol 135 (9) ◽  
Author(s):  
Sowmitra Singh ◽  
Jin-Keun Choi ◽  
Georges L. Chahine
Keyword(s):  
Peak Amplitude ◽  
Peak Width ◽  
Pressure Transducers ◽  
High Frequency Response ◽  
Statistical Representation ◽  
Cavitation Field ◽  
Cavitation Pressure ◽  
Response Pressure ◽  
Ultrasonic Horns

Cavitation pressure fields under a cavitating jet and an ultrasonic horn were recorded for different conditions using high frequency response pressure transducers. This was aimed at characterizing the impulsive pressures generated by cavitation at different intensities. The pressure signals were analyzed and statistics of the amplitudes and widths of the impulsive pressure peaks were extracted. Plots of number densities and cumulative numbers of peaks as functions of peak amplitude, peak width, and the power of the ultrasonic horn or the jet were generated. The analysis revealed the dominance of pulses with smaller amplitudes and larger durations at lower cavitation intensities and the increase of the amplitudes and reduction of the pulse widths at higher intensities. The ratio of the most probable peak amplitude to peak width was computed. A representative Gaussian curve was then generated for each signal using a characteristic peak amplitude and the corresponding most probable peak duration/width. This resulted in a proposed statistical representation of a cavitation field, useful to characterize cavitation fields of various intensities.

Sign in / Sign up

Export Citation Format

Share Document