Multivariable Closed-Loop Active Flow Control of a Compressor Stator Cascade

This paper presents a multivariable closed-loop active flow control strategy to control the pressure rise and the wake size of a compressor stator cascade. For flow control, a combination of two actuator concepts, trailing-edge and sidewall blowing, was applied to a linear stator cascade. Detailed five-hole probe measurements of the downstream flowfield at a Reynolds number of were carried out to reveal the effect of the actuation on the cascade flow. An increase in the pressure rise coefficient by 5% and a significant reduction of the wake size could be achieved with the investigated actuation amplitudes of values up to 2.5%. Principal component analysis was used to find coherent structures in the full measurement data set. Based on this analysis, a real-time estimation of the complex downstream flowfield with only three pressure sensors was realized. With this estimation, linear dynamic black-box models for the pressure rise coefficient and the wake size were identified. Variable reference signals with a Strouhal number of 0.03, specified by a later application in a pressure gain combustion system, were successfully tracked, leading to small experimental control errors.