Shock Wave and Flow Velocity Measurements in a High Speed Fan Rotor Using the Laser Velocimeter

1977 ◽  
Vol 99 (2) ◽  
pp. 181-187 ◽  
Author(s):  
D. C. Wisler
Keyword(s):  
Shock Wave ◽  
Flow Velocity ◽  
High Speed ◽  
Fluid Dynamic ◽  
Equations Of Motion ◽  
Seed Particle ◽  
Gas Velocity ◽  
Velocity Measurements ◽  
Rotating Blade ◽  
Finite Difference Solution

The laser velocimeter, an instrument capable of making nondisturbing gas velocity measurements, was used to determine shock wave locations and to make gas velocity measurements within the rotating blade row of a 550-m/s (1800-ft/s)-tip speed fan rotor. The velocimeter measures the transit time of a seed particle across interference fringes produced at the intersection of a split and crossed laser beam. The rotor flowfields were obtained at several radial immersions for operating-line and near-stall throttle settings. The results show the change in shock pattern and flow velocity as the compressor is throttled toward stall. Analytical predictions of the flowfield were also obtained using both the method of characteristics and a time-dependent, finite-difference solution of the fluid dynamic equations of motion. The analytical results and the flowfield measurements are considered to be in good agreement.

Gas Velocity Measurements Within a Compressor Rotor Passage Using the Laser Doppler Velocimeter

1973 ◽  
Vol 95 (2) ◽  
pp. 91-96 ◽  
Author(s):  
D. C. Wisler ◽  
P. W. Mossey
Keyword(s):  
High Speed ◽  
Axial Compressor ◽  
Laser Doppler ◽  
Laser Doppler Velocimeter ◽  
Seed Particle ◽  
Gas Velocity ◽  
Velocity Measurements ◽  
Flow Measurements ◽  
Velocity Magnitude ◽  
New Instrument

The laser Doppler velocimeter, a new instrument capable of making nondisturbing gas velocity measurements, was used to investigate the flowfield within the rotating blade row of a low speed axial compressor. The velocimeter operates by measuring the transit time of a seed particle across interference fringes produced at the intersection of a split and crossed laser beam. The velocity (magnitude and direction) measurements made with the laser at the rotor inlet and discharge generally agreed within 2 to 3 per cent with measurements made with a hot film anemometer, pitot-static probe and wedge and tuft angle probes. Detailed flowfield measurements within the rotor passage were then obtained and compared with the analytical results from a potential flow model. This technique shows promise in making detailed flow measurements within high speed fans, compressors, turbines and nozzles, including the mapping of shock structures.

An Experimental Study of Spark Anemometry for In-Cylinder Velocity Measurements

2008 ◽  
Vol 130 (4) ◽  
Author(s):  
D. P. Gardiner ◽  
G. Wang ◽  
M. F. Bardon ◽  
M. LaViolette ◽  
W. D. Allan
Keyword(s):  
Experimental Study ◽  
Flow Velocity ◽  
High Speed ◽  
Spark Ignition Engine ◽  
Constant Current ◽  
Velocity Measurements ◽  
Lower Velocity ◽  
Freestream Velocity ◽  
Channel Shape ◽  
Spark Channel

It has been demonstrated by previous researchers that an approximate value of the bulk flow velocity through the spark plug gap of a running spark ignition engine may be deduced from the voltage and current wave forms of the spark. The technique has become known as spark anemometry and offers a robust means of velocity sensing for engine combustion chambers and other high temperature environments. This paper describes an experimental study aimed at improving performance of spark anemometry as an engine research tool. Bench tests were conducted using flow provided by a calibrated nozzle apparatus discharging to atmospheric pressure. While earlier studies had relied upon assumptions about the shape of the stretching spark channel to relate the spark voltage to the flow velocity, the actual spark channel shape was documented using high-speed video in the present study. A programmable ignition system was used to generate well-controlled constant current discharges. The spark anemometry apparatus was then tested in a light duty automotive engine. Results from the image analysis of the spark channel shape undertaken in the present study have shown that the spark kernel moves at a velocity of less than that of the freestream gas velocity. A lower velocity threshold exists below, which there is no response from the spark. It is possible to obtain a consistent, nearly linear relationship between the first derivative of the sustaining voltage of a constant current spark and the freestream velocity if the velocity falls within certain limits. The engine tests revealed a great deal of cycle-to-cycle variation in the in-cylinder velocity measurements. Instances where the spark restrikes occur during the cycle must also be recognized in order to avoid false velocity indications.

Dynamics of a Radial Electrorheological Clutch

1999 ◽  
Vol 13 (14n16) ◽  
pp. 2119-2126 ◽  
Author(s):  
M. Whittle ◽  
R. J. Atkin ◽  
W. A. Bullough
Keyword(s):  
Yield Stress ◽  
High Speed ◽  
Fluid Dynamic ◽  
Equations Of Motion ◽  
Time Dependent ◽  
Maximum Acceleration ◽  
Bingham Plastic ◽  
Viscous Component ◽  
Output Load ◽  
Dynamic Restriction

Time dependent solutions to the equations of motion for flow in an enclosed radial electro-rheological clutch are developed and discussed in relation to the speed of operation. The method follows a procedure previously developed for cylindrical clutch geometry but in this case analytical solutions are obtained. The fluid is treated as a homogeneous continuum obeying the Bingham plastic constitutive equation incorporating a yield stress and viscous component. The results show that the acceleration expected from a consideration of yield stress and inertia is not always achieved. The viscous component places fluid dynamic restriction on the maximum acceleration of the output rotor. However, this limit is only approached if the output load inertia is very low. The results have a bearing on the choice of fluid for high speed operation.

A study of the collapse of arrays of cavities

1988 ◽  
Vol 190 ◽  
pp. 409-425 ◽  
Author(s):  
J. P. Dear ◽  
J. E. Field
Keyword(s):  
Shock Wave ◽  
High Speed ◽  
High Speed Photography ◽  
Cavitation Damage ◽  
Major Mechanism ◽  
Collapse Mechanisms ◽  
Multiple Jets ◽  
Circular Holes ◽  
Schlieren Photography ◽  
Thick Glass

This paper describes a method for examining the collapse of arrays of cavities using high-speed photography and the results show a variety of different collapse mechanisms. A two-dimensional impact geometry is used to enable processes occurring inside the cavities such as jet motion, as well as the movement of the liquid around the cavities, to be observed. The cavity arrangements are produced by first casting water/gelatine sheets and then forming circular holes, or other desired shapes, in the gelatine layer. The gelatine layer is placed between two thick glass blocks and the array of cavities is then collapsed by a shock wave, visualized using schlieren photography and produced from an impacting projectile. A major advantage of the technique is that cavity size, shape, spacing and number can be accurately controlled. Furthermore, the shape of the shock wave and also its orientation relative to the cavities can be varied. The results are compared with proposed interaction mechanisms for the collapse of pairs of cavities, rows of cavities and clusters of cavities. Shocks of kbar (0.1 GPa) strength produced jets of c. 400 m s−1 velocity in millimetre-sized cavities. In closely-spaced cavities multiple jets were observed. With cavity clusters, the collapse proceeded step by step with pressure waves from one collapsed row then collapsing the next row of cavities. With some geometries this leads to pressure amplification. Jet production by the shock collapse of cavities is suggested as a major mechanism for cavitation damage.

scholarly journals Measurement of flow velocity profiles in tank structures using the prototype device OCM Pro LR

2011 ◽  
Vol 64 (1) ◽  
pp. 263-270 ◽  
Author(s):  
K. Klepiszewski ◽  
M. Teufel ◽  
S. Seiffert ◽  
E. Henry
Keyword(s):  
Flow Velocity ◽  
Large Scale ◽  
Fluid Dynamic ◽  
Waste Water Treatment ◽  
Transport Processes ◽  
Treatment Efficiency ◽  
Cleaning Efficiency ◽  
Cfd Modelling ◽  
Ultrasonic Signals ◽  
Cfd Models

Generally, studies investigating the treatment efficiency of tank structures for storm water or waste water treatment observe pollutant flows in connection with conditions of hydraulic loading. Further investigations evaluate internal processes in tank structures using computational fluid dynamic (CFD) modelling or lab scale tests. As flow paths inside of tank structures have a considerable influence on the treatment efficiency, flow velocity profile (FVP) measurements can provide a possibility to calibrate CFD models and contribute to a better understanding of pollutant transport processes in these structures. This study focuses on tests carried out with the prototype FVP measurement device OCM Pro LR by NIVUS in a sedimentation tank with combined sewer overflow (CSO) situated in Petange, Luxembourg. The OCM Pro LR measurement system analyses the echo of ultrasonic signals of different flow depths to get a detailed FVP. A comparison of flow velocity measured by OCM Pro LR with a vane measurement showed good conformity. The FVPs measured by OCM Pro LR point out shortcut flows within the tank structure during CSO events, which could cause a reduction of the cleaning efficiency of the structure. The results prove the applicability of FVP measurements in large-scale structures.

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