Effects of a sweeping jet actuator on aerodynamic performance in a linear turbine cascade with tip clearance

Abstract

Sweeping jet actuator as a fresh attempt has been applied in controlling flow separations and improving aerodynamic performances in a linear turbine cascade with tip clearance. In the present study, the oscillating jet process of sweeping jet actuator in the tip clearance was illustrated and a potential advantage from a system integration perspective was validated by an unsteady numerical study. The excitation frequencies and excitation modes were also investigated for achieving the further understanding of the mechanism of sweeping jet actuator for controlling flow separations. By using sweeping jet actuator, the flow separation near the upper endwall was delayed and the flow loss at the outlet of the cascade was reduced. For the optimal case, the time-averaged total pressure loss decreased by about 11.7% with the jet flow rate of only 0.35% of the inlet flow rate. In addition, it was found that there exists an optimum frequency to achieve the optimum controlling effects on the flow separations. Because of the blockage of tip leakage flow at the local gap by the high-momentum fluid from sweeping jet actuator, the controlling effects on the tip leakage vortex loss were better than that on the passage vortex loss. Through the use of four excitation modes in this study, the total pressure losses at the outlet were all reduced in different degrees. Under the present boundary conditions and working parameters, the unsteady controlling mode of sweeping jet actuator was found to perform much better than the other steady modes.

Flow Control in Wings and Discovery of Novel Approaches via Deep Reinforcement Learning

“…Other works involving the use of sweeping jets can be found in Refs. [47,48]. The effectiveness of microjets in drag reduction was experimentally studied by Aley et al [49] in a simplified 2D wing; a significant wake velocity deficit reduction and, thus, drag, was observed when using the microjets actuation.…”

Flow Control in Wings and Discovery of Novel Approaches via Deep Reinforcement Learning

“…Other works involving the use of sweeping jets can be found in Refs. [47,48]. The effectiveness of microjets at drag reduction was experimentally studied by Aley et al [49] in a simplified 2D wing; a significant wake velocity deficit reduction and thus, drag was observed when using the microjets actuation.…”

Characteristics of a Fluidic Oscillator with Low Frequency and Low Speed and Its Application to Stall Margin Improvement

“…In recent years, wall-attachment oscillators have been widely studied in airfoil lift augmentation [28], cavity noise suppression [29], and heat conduction enhancement [30,31]. In the field of aero-engines, wall-attachment oscillators have been applied to adjust the thrust vector [32]; control flow separation at the s-shaped inlet [33], corner of compressor stator [34,35], and outlet guide vane of high-load turbine [36]; and reduce loss caused by turbine tip clearance leakage vortex [37].…”