The active flow control technique of vortex-generator jet (VGJ) was used to control the turbulent separation of a highly loaded compressor cascade at a high incidence. VGJ schemes on suction surface with different jet locations, skewed angles, pitch angles were numerically performed and the control mechanism of VGJ parameters on the flow field of the cascade was revealed. For avoiding the effect of endwall boundary layer, both endwall surfaces of the cascade were set to translational periodicity boundary (TPB). Results show that VGJ significantly eliminates the turbulent separation and improves the performance of cascade. The overall loss coefficient of cascade is reduced by 52.3% at most. The optimal VGJ location in this study is not separation location but 7% axial chord downstream of it, which is probably due to the ultra-high loading of the cascade. The spanwise location and intensity of jet vortices are mainly affected by skewed angle, and will increase with the skewed angle. The VGJ case with a higher pitch angle features better control effect on suction surface but increases the pitchwise scale of the low-velocity region. In addition, as pitch angle increases, the mixing loss between mainstream and jet flow increases, which brings a negative effect on cascade performance. In order to enhance the momentum transporting between mainstream flow and separation flow, counter vortex-generator jet (CVGJ) schemes were designed and studied. Though CVGJ strengthens the jet vortices near the trailing edge and achieves minimum loss near TPB sections at 150% axial chord section, the interaction of jet vortices with opposite rotating direction brings extra loss, which leads to the control effect of CVGJ is weaker than that of VGJ.
Counter-rotating (CR) compressor is a potential configuration to increase the thrust-to-weight ratio of aero-engines. The present study numerically investigated a dual-stage CR compressor by solving unsteady Reynolds-averaged Naiver–Stokes equations. The unsteady flow mechanisms were analyzed and compared for swept and baseline (radially stacked) CR rotors. Both of these rotor configurations were numerically simulated for the entire design speed line. The unsteady flow field near the mid-span and blade tip characterized by tip leakage vortex (TLV) was analyzed in detail for both near peak efficiency (NPE) and near stall (NS) conditions. According to the results, blade loading of the second rotor (R2) was much higher than that of the first rotor (R1). Moreover, the blade loading was higher in the swept rotors in comparison with the baseline CR rotors. In both baseline and swept CR compressors, the potential effect of R2 on the static pressure distribution of R1 was more significant compared to the opposite effect. Under the NS condition, the potential effect was confined in the rear zone of R1 where the potential flow of R2 passed. Despite the obvious impact of wake-induced negative jet on the flow field of R2 blade passage, the static pressure of R2 blade exhibited no evident variation except at 90% spanwise position. Although the blade loading of the swept CR compressor was increased, the potential effect of R2 on R1 was considerably reduced due to growth of axial gap between R1 and R2. Since the blade sweep improved the flow field, the wake passing effect on R2 was more moderate compared to that of the baseline CR compressor. The perturbation velocity magnitude of the swept CR compressor was approximately half of that of the baseline CR compressor. The TLV of R2 was periodically disturbed, and therefore, low axial velocity patches were observed on the TLV trajectory of R2. In addition, the swept CR compressor exhibited smaller low axial velocity patches of TLV due to weaker aerodynamic interaction between R1 and R2.
Upstream vortex has a significant effect on the secondary flow structure of the downstream turbine in the stage environment. This study investigates the secondary flow structure with non-axisymmetric endwall profiling (NAEW) under the interaction of co-rotating incoming vortex (Vic). A half-delta wing vortex generator is utilized to model Vic. The turbine cascade case which exhibited maximum reduction of the cascade loss with NAEW under no incoming vortex is studied. The mechanism of loss reduction with NAEW under the interaction of Vic is analysed. Vic could decrease the secondary flow near the endwall region by affecting the horseshoe vortex transport in the cascade. However, its loss reduction was lower than the loss increments of Vic itself. The arrival of Vic at the leading edge of the cascade increased the strength of the horseshoe vortex, resulting in a significant increase in loss. Under the interaction of Vic, NAEW decreased the blade loading near endwall region, which resulted in the reduction of cascade loss.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.