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This paper presents detailed flow-field measurements for a compressor cascade equipped with synthetic jet actuators for active flow control. The synthetic jets are mounted on the cascade sidewall and the suction side surface of the blade to reduce the total pressure loss caused by strong secondary flow structures developing in the passage. There are certain articles reporting that synthetic jets are well suited for flow control applications even in axial compressors and cascades. Most of them are focused on the parameter variation to optimize the efficiency of the control approach, still very little is known on the interaction of the synthetic jet actuators with the flow field. Detailed x-wire and pressure measurements were conducted to understand how synthetic jets influence the flow field and what causes the significant loss reduction in the cascade wake. It seems that the added momentum is not the key parameter for flow control with synthetic jets. In fact, the high mixing and the unsteadiness of the jets seem to amplify existing velocity fluctuations in the flow field. These increased fluctuations result in a shift of the shear layer between the flow separation and the surrounding flow, and thus in a dethrottling of the compressor cascade. Together with the increased mixing, loss reductions of approximately 10% can be reached using synthetic jet actuators. [ABSTRACT FROM PUBLISHER]

In this contribution the impact of active flow control by means of pulsed blowing in a critically loaded compressor cascade will be described. Because of the high loading of the blades, a fully three-dimensional and complex flowfield is developing. Experimental investigations with active flow control were undertaken to increase the turning and the pressure rise of the stator cascade, by suppressing separation phenomena in the passage flowfield. Two different concepts of actuators were used. First, pulsed blowing out of the endwalls was used to reduce the secondary flow structures. Second, the flow was excited with actuators flush-mounted on the blade's suction surface. The best performance was reached by using both actuator concepts in combination. A multivariable closed-loop control approach was used to control both separation phenomena simultaneously. Heavy disturbances could be compensated and a stabilization of the cascade operation point was achieved. [ABSTRACT FROM AUTHOR]