An effect of constant volume combustion (CVC) in gas turbines are pressure waves propagating upstream the main flow into the compressor system. Numerical and experimental investigations of stator vanes have shown that an adaptive blade geometry can be exploited for Active Flow Control (AFC) to mitigate the occurrence of periodical incidence variations. Experimental investigations on such an AFC method with simultaneous application of a closed-loop control are missing to demonstrate the potential.

This work investigates a linear compressor cascade that was equipped with a 3D-manufactured piezoadaptive blade structure. The utilized actuators are piezoelectric Macro-Fiber-Composites (MFC). A throttling device is positioned at downstream the trailing edge plane to emulates an unsteady combustion process. Periodical transient throttling events with a frequency of up to 20 Hz causes incidence change to the blade’s leading edge. Consequently, pressure fluctuations on the blades’ suction surface occur. Having a significant impact on the pressure recovery downstream of the stator cascade.

Experimental results of harmonically actuating the piezoadaptive blade with the corresponding disturbance frequency show, that the unsteady effects can be reduced to approx. 50%. This is only implemented effectively, when the phase shift of the harmonic actuation is adjusted correctly. Using the wrong phase shift, any positive effect on the flow can be reversed, leading to a stall, choke or significant losses. In order to ensure convergence to the optimum, even under varying, possibly unpredictable operating conditions, an Extremum-Seeking Control (ESC) algorithm is presented. This gradient based approach is minimizing the pressure variance over time by carefully adjusting the phase shift of the harmonic actuation of the AFC system.


Active Flow Control Utilizing an Adaptive Blade Geometry and an Extremum Seeking Algorithm at Periodically Transient Boundary Conditions

Division / Sponsor:
International Gas Turbine Institute (IGTI)

Paper Proceedings: https://asmedigitalcollection.asme.org/GT/GT2020/volume/84058

Turbo Expo - Virtual Conference

Supporting the need among researchers worldwide for additional online and multimedia content, ASME now offers the ASME Conference Video Collection. This platform will collect and provide long-term access to conference presentation videos, encompassing all technology areas within ASME's technical conference and events program. About 30,000-40,000 engineers across all mechanical engineering and related disciplines participate in ASME conferences each year. This includes authors of approximately 6,000 to 8,000 technical papers published by ASME, the majority of whom also submit video presentations for our virtual conferences. The video collection will be available as an add-on to existing product packages or as a separate subscription.