Conventional three-hole wedge probes fail to measure the correct static pressure when operating in close proximity to a wall or boundary through which the probe is inserted. The free-stream pressure near the outer wall of a turbomachine may be overindicated by up to 20 percent dynamic head. This paper reports a series of experiments aimed at quantifying this so-called “wall proximity effect.” It is shown from a factorial experiment that probe wedge angle, stem design, and free-stream Mach number all have a significant influence. The yaw angle sensitivity of wedge probes is also found to depend on the proximity of the probe to the wall of introduction. Flow visualization studies on large-scale probe models are described, and a qualitative model of the probe local flow structures is developed. This model is used to explain the near-wall characteristics of the actual size wedge probes. In Part 2 of this paper, the experimental data are used to validate CFD calculations of the flow field around a wedge probe. A simple analytical model of the probe/flow interaction is developed from the CFD solutions.

Issue Section:
Gas Turbines: Control and Dynamics
Topics:
Probes, Wedges, Flow (Dynamics), Computational fluid dynamics, Pressure, Design, Exterior walls, Flow visualization, Mach number, Turbomachinery, Yaw
1.
Bubeck, H., and Wachter, Y., 1987, “Development and Application of a High Frequency Wedge Probe,” ASME Paper No. 87-GT-216.
2.
Cook, S. C. P., 1988, “Measurement Techniques for Unsteady Turbomachinery Flows,” PhD Thesis, Cranfield University, Bedford, England.
3.
Davies, O. L., 1978, The Design and Analysis of Industrial Experiments, 2nd ed., Longman Group Ltd., London, England.
4.
Ferguson, T. B., and Al-Shamma, K. A., 1967, “Wedge Type Pitot-Static Probes,” BHRA SP919, 9th Members Conference, British Hydromechanics Research Association, Cranfield, England.
5.
Fransson, T., 1983, “Aerodynamic Probe Calibrations—Results From the Workshop on Probe Calibrations, 1981–1983,” Proc. 7th Symp. on Measuring Techniques for Transonic and Supersonic Flows in Cascades and Turbomachines, Aachen, Germany.
6.
Howard
M.
, et al.,
1994
, “
Endwall Effects at Two Tip Clearances in a Multistage Axial Flow Compressor With Controlled Diffusion Blading
,”
ASME JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER
, Vol.
116
, pp.
635
–
647
.
7.
Humm
H. J.
, et al.,
1995
, “
On Fast-Response Probes: Part 2—Aerodynamic Probe Design Studies
,”
ASME JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER
, Vol.
117
, pp.
618
–
624
.
8.
Morris, R. E., 1961, “Multiple Head Instrument for Aerodynamic Measurements,” The Engineer.
9.
Mueller, T. J., 1983, “Smoke Visualisation in Wind Tunnels,” Astronautics and Aeronautics, January ed.
10.
Shreeve, R. P., 1976, “Calibration and Application of Multiple Sensor Pneumatic Probes for Velocity Determination, With Corrections for Boundary Effects,” AIAA Paper No. 76-373.
11.
Smout, P. D., 1990, “The Problem of Static Pressure Measurement in Turbomachinery Annuli Using Traversable Instrumentation,” Proc. 10th Symp. Measuring Techniques for Transonic and Supersonic Flow in Cascades and Turbomachines, VKI, Brussels, Belgium.
12.
Smout, P. D., and Ivey, P. C., 1994, “Wall Proximity Effects in Pneumatic Measurement of Turbomachinery Flows,” ASME Paper No. 94-GT-116.
13.
Smout
P. D.
, and
Ivey
P. C.
,
1997
, “
Investigation of Wedge Probe Wall Proximity Effects: Part 2—Numerical and Analytical Modeling
,”
ASME JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER
, Vol.
119
, this issue, pp.
605
–
611
.
This content is only available via PDF.
Copyright © 1997
 by The American Society of Mechanical Engineers
You do not currently have access to this content.