ACTIVE FLOW CONTROL OF LOW PRESSURE TURBINE BLADE SEPARATION USING PLASMA ACTUATORS

• Main Author: Ramakumar, Karthik
• Format: Others
• Published: UKnowledge 2006
• Subjects: [none]; Mechanical Engineering
• Online Access: http://uknowledge.uky.edu/gradschool_theses/359; http://uknowledge.uky.edu/context/gradschool_theses/article/1362/type/native/viewcontent

The current study examines plasma actuators as flow control devices. The actuators are placed on a turbine blade profile in a 2D turbine cascade for separation flow control. The configuration involves copper strips separated by a layer of dielectric material, across which an AC electric potential in the range of 5 kHz and 5 kV is applied. The efficiency of the actuator is monitored by measuring power input and flow control effectiveness. Preliminary observations are performed for a quiescent case on a flat plate profile to analyze the average and instantaneous velocities generated by the actuator for varied input parameters, such as waveform shape and frequency. Observations include the generation of starting and standing vortices that may be leveraged for unsteady flow control applications. In the case of turbine flow control, the Pratt andamp; Whitney Pak-B blade profile is used to determine the actuator performance for separation reduction at Reynolds number O(104). The results are compared with flow control on and off states for varied actuator input frequency, power, duty cycle and freestream velocity. Pressure measurements are conducted for the actuated case that show reduced separation and increased main flow velocity. Experimental diagnostics include PIV, 7-hole probe, and smoke-wire flow visualization techniques. Phase locked PIV performed at different forcing frequencies reveals the generation of cross-stream vortices providing re-attachment of the separated flow. During the off periods of the cycle the region of separation is observed to creep back to its original separation point. Various fields-of-view show the structure of these cross-stream vortices at different phases. While the actuator is seen to accelerate the flow in the immediate region of the plasma, the generation of starting vortices demonstrates that unsteady actuation is a more effective form of flow control.