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Research Papers: Gas Turbines: Controls, Diagnostics, and Instrumentation

Assessment of Unsteady Pressure Measurement Uncertainty—Part II: Virtual Three-Hole Probe

[+] Author and Article Information
Giulia Dell'Era

Turbomachinery and Propulsion Department,
von Kármán Institute for Fluid Dynamics,
72, Chaussée de Waterloo,
Rhode-Saint-Genèse B-1640, Belgium
e-mail: dellera@vki.ac.be

Mehmet Mersinligil

Turbomachinery and Propulsion Department,
von Kármán Institute for Fluid Dynamics,
72, Chaussée de Waterloo,
Rhode-Saint-Genèse B-1640, Belgium
e-mail: mersinli@vki.ac.be

Jean-François Brouckaert

Turbomachinery and Propulsion Department,
von Kármán Institute for Fluid Dynamics,
72, Chaussée de Waterloo,
Rhode-Saint-Genèse B-1640, Belgium
e-mail: jean-francois.brouckaert@cleansky.eu

1Corresponding author.

Contributed by the Controls, Diagnostics and Instrumentation Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received July 15, 2015; final manuscript received August 10, 2015; published online October 13, 2015. Editor: David Wisler.

J. Eng. Gas Turbines Power 138(4), 041602 (Oct 13, 2015) (10 pages) Paper No: GTP-15-1325; doi: 10.1115/1.4031373 History: Received July 15, 2015; Revised August 10, 2015

With the advancements in miniaturization and temperature capabilities of piezoresistive pressure sensors, pneumatic probes—which are the long established standard for flow-path pressure measurements in gas turbine environments—are being replaced with unsteady pressure probes. On the other hand, any measured quantity is by definition inherently different from the “true” value, requiring the estimation of the associated errors for determining the validity of the results and establishing respective confidence intervals. In the context of pressure measurements, the calibration uncertainty values, which differ from measurement uncertainties, are typically provided. Even then, the lack of a standard methodology is evident as uncertainties are often reported without appropriate confidence intervals. Moreover, no time-resolved measurement uncertainty analysis has come to the attention of the authors. The objective of this paper is to present a standard method for the estimation of the uncertainties related to measurements performed using single sensor unsteady pressure probes, with the help of measurements obtained in a one and a half stage low pressure high speed axial compressor test rig as an example. The methodology presented is also valid for similar applications involving the use of steady or unsteady sensors and instruments. The static calibration uncertainty, steady measurement uncertainties, and unsteady measurement uncertainties based on phase-locked average (PLA) and ensemble average are presented by the authors in Dell'Era et al. (2016, “Assessment of Unsteady Pressure Measurement Uncertainty—Part 1: Single Sensor Probe,” ASME J. Eng. Gas Turbines Power, 138(4), p. 041601). Depending on the number of points used for the averaging, different values for uncertainty have been observed, underlining the importance of having greater number of samples. For unsteady flows, higher uncertainties have been observed at regions of higher unsteadiness such as tip leakage vortices, hub-corner vortices, and blade wakes. Unfortunately, the state of the art in single sensor miniature unsteady pressure probes is comparable to multihole pneumatic probes in size, preventing the use of multihole unsteady probes in turbomachinery environments. However, the angular calibration properties of a single sensor probe obtained via an aerodynamic calibration may further be exploited as if a three-hole directional probe is employed, yielding corrected total pressure, unsteady yaw angle, static pressure and Mach number distributions based on the PLAs with the expense of losing the time-correlation between the virtual ports. The aerodynamic calibration and derivation process are presented together with the assessment of the uncertainties associated to these derived quantities in this contribution. In the virtual three-hole mode, similar to that of a single sensor probe, higher uncertainty values are observed at regions of higher unsteadiness.

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References

Mersinligil, M. , Brouckaert, J.-F. , and Desset, J. , 2011, “ Unsteady Pressure Measurements With a Fast Response Cooled Probe in High Temperature Environments,” ASME J. Eng. Gas Turbines Power, 133(8), p. 081603. [CrossRef]
Mersinligil, M. , 2014, “ Development of a High Temperature Cooled Fast Response Probe for Gas Turbine Applications,” Ph.D., thesis, von Karman Institute for Fluid Dynamics, St. Genesius-Rode, Belgium.
Pfau, A. , Schlienger, J. , Kalfas, A. , and Abhari, R. , 2002, “ Virtual Four Sensor Fast Response Aerodynamic Probe (frap®),” 16th Symposium on Measuring Techniques in Transonic and Supersonic Flows in Cascades and Turbomachines.
Schlienger, J. , Pfau, A. , Kalfas, A. , and Abhari, R. , 2002, “ Single Pressure Transducer Probe for 3d Flow Measurements,” 16th Symposium on Measuring Techniques in Transonic and Supersonic Flows in Cascades and Turbomachines.
Dieck, R. H. , 2007, Measurement Uncertainty: Methods and Applications, 4th ed. ISA, Research Triangle Park, NC.
Dieck, R. H. , 1997, “ Measurement Uncertainty Models,” ISA Trans., 36(1), pp. 29–35. [CrossRef]
Treiber, M. , Kupferschmied, P. , and Gyarmathy, G. , 1998, “ Analysis of the Error Propagation Arising From the Measurements With a Miniature Pneumatic 5-Hole Probe,” 14th Symposium on Measuring Techniques for Transonic and Supersonic Flows in Cascade and Turbomachines.
Luck, R. , and Stevens, J. , 2004, “ A Simple Numerical Procedure for Estimating Nonlinear Uncertainty Propagation,” ISA Trans., 43(4), pp. 491–497. [CrossRef] [PubMed]
Dell'Era, G. , Mersinligil, M. , and Brouckaert, J.-F. , 2016, “ Assessment of Unsteady Pressure Measurement Uncertainty—Part I: Single Sensor Probe,” ASME J. Eng. Gas Turbines Power.

Figures

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Fig. 1

Illustration of yaw and pitch axes of a pressure probe

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Fig. 2

Pressure recovery coefficient of the AP1-FL3 at M = 0.7

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Fig. 3

Pressure recovery coefficient of the AP1-FL3 at M = 0.7 together with expanded calibration uncertainties

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Fig. 4

The derived aerodynamic calibration curve of the virtual three-hole mode probe at M = 0.7

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Fig. 5

Flow angle with respect to yaw coefficient and Mach number for a probe setting angle of 35 deg

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Fig. 6

Corrected total pressure coefficient with respect to yaw angle and Mach number for a probe setting angle of 35 deg

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Fig. 7

Static pressure coefficient with respect to yaw angle and Mach number for a probe setting angle of 35 deg

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Fig. 8

PLA (left) and expanded uncertainty (right) map of the center hole over two blade passages

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Fig. 9

PLA (left) and expanded uncertainty (right) map of the left hole over two blade passages

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Fig. 10

PLA (left) and expanded uncertainty (right) map of the right hole over two blade passages

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Fig. 11

The corrected total pressure (left) and expanded uncertainty for 95% confidence interval (right) maps presented over two blade passages

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Fig. 12

The static pressure (left) and expanded uncertainty for 95% confidence interval (right) maps presented over two blade passages

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Fig. 13

The Mach number (left) and expanded uncertainty for 95% confidence interval (right) maps presented over two blade passages

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Fig. 14

The yaw angle (left) and related expanded uncertainty for 95% confidence interval (right) maps presented over two blade passages

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