Research Papers

Experimental Investigation of Tip Clearance Flow in a Transonic Compressor With and Without Plasma Actuators

[+] Author and Article Information
S. Saddoughi

GE Global Research,
Niskayuna, NY 12309
e-mail: saddoughi@ge.com

G. Bennett

GE Global Research,
Niskayuna, NY 12309
e-mail: grover.bennett@ge.com

M. Boespflug

GE Global Research,
Niskayuna, NY 12309
e-mail: boespflu@ge.com

S. L. Puterbaugh

Wright-Patterson AFB, OH 45433
e-mail: steven.puterbaugh@us.af.mil

A. R. Wadia

Fellow ASME
GE Aviation,
Cincinnati, OH 45215
e-mail: aspi.wadia@ge.com

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the JOURNAL OF TURBOMACHINERY. Manuscript received August 12, 2014; final manuscript received August 18, 2014; published online October 28, 2014. Editor: Ronald Bunker. This material is declared a work of the US Government and is not subject to copyright protection in the United States. Approved for public release; distribution is unlimited.

J. Turbomach 137(4), 041008 (Oct 28, 2014) (10 pages) Paper No: TURBO-14-1207; doi: 10.1115/1.4028444 History: Received August 12, 2014; Revised August 18, 2014

Blade tip losses represent a major performance penalty in low aspect ratio transonic compressors. This paper reports on the experimental evaluation of the impact of tip clearance with and without plasma actuator flow control on performance of an U.S. Air Force-designed low aspect ratio, high radius ratio single-stage transonic compressor rig. The detailed stage performance measurements without flow control at three clearance levels, classified as small, medium, and large, are presented. At design-speed, increasing the clearance from small to medium resulted in a stage peak efficiency drop of almost six points with another four point drop in efficiency with the large clearance (LC). Comparison of the speed lines at high-speed show significantly lower pressure rise with increasing tip clearance, the compressor losing 8% stall margin (SM) with medium clearance (MC) and an additional 1% with the LC. Comparison of the stage exit radial profiles of total pressure and adiabatic efficiency at both part-speed and design-speed and with throttling are presented. Tip clearance flow-control was investigated using dielectric barrier discharge (DBD) type plasma actuators. The plasma actuators were placed on the casing wall upstream of the rotor leading edge and the compressor mapped from part-speed to high-speed at three clearances with both axial and skewed configurations at six different frequency levels. The plasma actuators did not impact steady state performance. A maximum SM improvement of 4% was recorded in this test series. The LC configuration benefited the most with the plasma actuators. Increased voltage provided more SM improvement. Plasma actuator power requirements were almost halved going from continuous operation to pulsed plasma. Most of the improvement with the plasma actuators is attributed to the reduction in unsteadiness of the tip clearance vortex near-stall resulting in additional reduction in flow prior to stall.

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Fig. 1

Flow-path showing the location of the plasma actuators upstream of the rotor leading edge

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Fig. 2

Comparison of measured stage performance for the three clearance configurations

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Fig. 3

Distribution of peak stage adiabatic efficiency (PEAK EFF) with percent corrected speed at small, medium, and large clearance levels

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Fig. 4

Distribution of the stage adiabatic efficiency with SM for small, medium, and large clearances at 100% design-speed

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Fig. 5

Comparison of the radial (IMM, 0 = tip, 1 = hub) profiles of stage exit total pressure ratio and adiabatic efficiency on the O/L at 80 and 100% speeds

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Fig. 6

Comparison of the effect of throttling from peak efficiency to stall on the radial profiles of total pressure and efficiency at design-speed

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Fig. 7

Comparison of the effect of throttling from peak efficiency to stall on the radial profiles of total pressure and efficiency at 80% speed

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Fig. 8

Comparison of the radial profiles of efficiency at compressor peak efficiency operating condition at 80 and 100% speeds

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Fig. 9

Comparison of the loss in peak efficiency and SM with tip clearance

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Fig. 10

Surface DBD used as an aerodynamic actuator. (a) Actuator schematic. (b) Starting vortex created by a DBD.

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Fig. 11

Dynamic shadowgraph picture of three starting vortices using a multiple DBD device

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Fig. 12

Tip leakage flow control cascade. (a) Schematic of the cascade. (b) Tip leakage with plasma inactive. (c) Tip leakage with plasma active.

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Fig. 13

Plasma actuators installed in the compressor rig. (a) Multiple actuators configuration to generate greater axial body force. (b) Plasma actuators in operation at stationary condition with the flow barrel open.

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Fig. 14

Skewed plasma actuators installed in the compressor rig. (a) Multiple skewed actuators are perpendicular to the blade stagger angle. (b) Skewed plasma actuators in operation at stationary condition with the flow barrel open.

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Fig. 15

Percent improvement in SM achieved with different plasma actuator configurations with the three clearance configurations. The clearance level, corrected speed, and plasma actuator configuration is shown on the x-axis for each case. The numerical values of percent stall margin (%SM) improvements shown are relative to the same clearance configurations with the plasma actuators inactive.

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Fig. 16

Comparison of measured steady state stage performance with and without plasma actuators at 80% corrected speed with the LC configuration

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Fig. 17

Calculated static pressure contours [18] at the tip of a transonic blade near peak efficiency and near-stall




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