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

2014 ◽  
Vol 137 (4) ◽  
Author(s):  
S. Saddoughi ◽  
G. Bennett ◽  
M. Boespflug ◽  
S. L. Puterbaugh ◽  
A. R. Wadia
Keyword(s):  
Flow Control ◽  
High Speed ◽  
Plasma Actuator ◽  
Tip Clearance ◽  
Plasma Actuators ◽  
Tip Clearance Flow ◽  
Transonic Compressor ◽  
Low Aspect Ratio ◽  
Clearance Flow ◽  
Design Speed

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.

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

2014 ◽  
Author(s):  
S. Saddoughi ◽  
G. Bennett ◽  
M. Boespflug ◽  
S. L. Puterbaugh ◽  
A. R. Wadia
Keyword(s):  
Flow Control ◽  
High Speed ◽  
Tip Clearance ◽  
Plasma Actuators ◽  
Stall Margin ◽  
Tip Clearance Flow ◽  
Transonic Compressor ◽  
Clearance Flow ◽  
Stall Margin Improvement ◽  
Design Speed

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 6 points with another 4 point drop in efficiency with the large clearance. Comparison of the speed lines at high-speed show significantly lower pressure rise with increasing tip clearance, the compressor losing 8 percent stall margin with medium clearance and an additional 1 percent with the large clearance. 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 stall margin improvement of 4 percent was recorded in this test series. The large clearance configuration benefited the most with the plasma actuators. Increased voltage provided more stall margin 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.

Tip Clearance Flow Visualization of a Turbine Blade Cascade With Active and Passive Flow Control

2008 ◽  
Author(s):  
Daniel K. Van Ness ◽  
Thomas C. Corke ◽  
Scott C. Morris
Keyword(s):  
Flow Control ◽  
Flow Visualization ◽  
Total Pressure ◽  
Plasma Actuator ◽  
Tip Clearance ◽  
Tip Clearance Flow ◽  
Tip Leakage ◽  
Blade Cascade ◽  
Clearance Flow ◽  
Blade Tip

The secondary flow in the tip clearance region of a stationary linear low pressure turbine blade cascade was studied using two types of surface flow visualization and documented using wake pressure measurements in order to identify the potential means and impact of flow control to reduce losses associated with the tip clearance flow. An evaporating fluid mixture was used for flow visualization on the casing surface of the tip clearance. An oil ink-dot tracing method was used on the blade tip. These measurements illustrate the important features of the near-casing flow physics, including the size and chordwise extent of the blade tip separation bubble, separation lines on the casing, the flow direction on the blade tip and casing, the size and exit trajectory of the tip leakage and passage vortices, as well as the total pressure loss and secondary velocity vectors downstream of the blade. The flow was visualized in this way for a plain, flat tip, a tip mounted plasma actuator, and a partial suction side squealer tip. Both flow control devices were observed to affect the flow in the clearance. The plasma actuator was shown to improve the total pressure loss in the tip leakage vortex by as much as 9% from the loss over the plain tip blade. The tests were performed over a Reynolds numbers range between 5.3 × 104 and 1.04 × 105 at a fixed tip clearance of 2% of axial chord.

Plasma Actuator Blade Tip Clearance Flow Control in a Linear Turbine Cascade

2012 ◽  
Vol 28 (3) ◽  
pp. 504-516 ◽  
Author(s):  
Daniel K. Van Ness ◽  
Thomas C. Corke ◽  
Scott C. Morris
Keyword(s):  
Flow Control ◽  
Plasma Actuator ◽  
Tip Clearance ◽  
Turbine Cascade ◽  
Tip Clearance Flow ◽  
Clearance Flow ◽  
Blade Tip ◽  
Blade Tip Clearance

Numerical Simulation of Tip Clearance Control in Axial Turbine Rotor: Part 2—Passive Control of Five Different Tip Platforms

2008 ◽  
Author(s):  
Wei Li ◽  
Wei-Yang Qiao ◽  
Kai-Fu Xu ◽  
Hua-Ling Luo
Keyword(s):  
Flow Control ◽  
Passive Control ◽  
Suction Side ◽  
Turbine Rotor ◽  
Tip Clearance ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Tip Clearance Flow ◽  
Tip Leakage ◽  
Clearance Flow

The tip leakage flow has significant effects on turbine in loss production, aerodynamic efficiency, etc. Then it’s important to minimize these effects for a better performance by adopting corresponding flow control. The active turbine tip clearance flow control with injection from the tip platform is given in Part-1 of this paper. This paper is Part-2 of the two-part papers focusing on the effect of five different passive turbine tip clearance flow control methods on the tip clearance flow physics, which consists of a partial suction side squealer tip (Partial SS Squealer), a double squealer tip (Double Side Squealer), a pressure side tip shelf with inclined squealer tip on a double squealer tip (Improved PS Squealer), a tip platform extension edge in pressure side (PS Extension) and in suction side (SS Extension) respectively. Combined with the turbine rotor and the numerical method mentioned in Part 1, the effects of passive turbine tip clearance flow controls on the tip clearance flow were sequentially simulated. The detailed tip clearance flow fields with different squealer rims were described with the streamline and the velocity vector in various planes parallel to the tip platform or normal to the tip leakage vortex core. Accordingly, the mechanisms of five passive controls were put in evidence; the effects of the passive controls on the turbine efficiency and the tip clearance flow field were highlighted. The results show that the secondary flow loss near the outer casing including the tip leakage flow and the casing boundary layer can be reduced in all the five passive control methods. Comparing the active control with the passive control, the effect brought by the active injection control on the tip leakage flow is evident. The turbine rotor efficiency could be increased via the rational passive turbine tip clearance flow control. The Improved PS Squealer had the best effect on turbine rotor efficiency, and it increased by 0.215%.

scholarly journals The Effect of Tip Clearance Gap Size and Wall Rotation on the Performance of a High-Speed Annular Compressor Cascade

1998 ◽  
Author(s):  
A. Doukelis ◽  
K. Mathioudakis ◽  
K. Papailiou
Keyword(s):  
High Speed ◽  
Static Pressure ◽  
Tip Clearance ◽  
Performance Characteristics ◽  
Compressor Cascade ◽  
Tip Clearance Flow ◽  
Pressure Distributions ◽  
Clearance Flow ◽  
Overall Performance ◽  
Probe Measurements

The performance of a high speed annular compressor cascade for different clearance gap sizes, with stationary or rotating hub wall is investigated. Five hole probe measurements, conducted at the inlet and outlet of the cascade, are used to derive blade performance characteristics, in the form of loss and turning distributions. Characteristics are presented in the form of circumferentially mass averaged profiles, while distributions on the exit plane provide information useful to interpret the performance of the blading. Static pressure distributions on the surface of the blades as well as inside the tip clearance gap have also been measured. A set of four clearance gap sizes, in addition to zero clearance data for the stationary wall, gives the possibility to observe the dependence of performance characteristics on clearance size, and establish the influence of rotating the hub. Overall performance is related to features of the tip clearance flow. Increasing the clearance size is found to increase losses in the clearance region, while it affects the flow in the entire passage. Wall rotation is found to improve the performance of the cascade.

Numerical Investigation of Tip Clearance Flow Induced Flutter in an Axial Research Compressor

2016 ◽  
Author(s):  
Daniel Möller ◽  
Maximilian Jüngst ◽  
Felix Holzinger ◽  
Christoph Brandstetter ◽  
Heinz-Peter Schiffer ◽  
...  
Keyword(s):  
Early Stage ◽  
Rotor Blades ◽  
Tip Clearance ◽  
Blade Vibration ◽  
Tip Clearance Flow ◽  
Transonic Compressor ◽  
Clearance Flow ◽  
Fluctuation Pattern ◽  
Blade Tip ◽  
Pass Through

A flutter phenomenon was observed in a 1.5-stage configuration at the Darmstadt transonic compressor. This phenomenon is investigated numerically for different compressor speeds. The flutter occurs for the second eigenmode of the rotor blades and is caused by tip clearance flow which is able to pass through multiple rotor gaps at highly throttled operating points. The vibration pattern during flutter is accompanied by a pressure fluctuation pattern of the tip clearance flow which is interacting with the blade motion causing the aeroelastic instability. The velocity of the tip clearance flow fluctuation is about 50% of the blade tip speed for simulation and experiment and also matches the mean convective velocity inside the rotor gap. This is consistent for all compressor speeds. From this investigations, general guidelines are drawn which can be applied at an early stage during compressor design to evaluate the susceptibility to this kind of blade vibration.

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