The research focuses on the high-load compressor cascade with a four-tooth straight-tooth labyrinth seal. Jet holes with varying air inlet and jet positions are designed to investigate the mechanism and principles underlying the impact of adaptive jets on the performance of compressor cascades. The results show that the jet flow from the labyrinth seal to the suction side has a good improvement effect on the performance of the compressor cascade, which can suppress the influence region of the concentrated separation vortex and the wall vortex, improve the flow field structure, reduce the total pressure loss, and enhance the expansion capacity. What is more, the improvement effect on the flow field structure and the performance is enhanced as the flow rate of the jet hole increases. The most significant improvement in the performance of the compressor cascade is achieved by introducing air from the second tooth cavity, which can reduce the total pressure loss coefficient by 3%, reduce the volume of low kinetic energy fluid clusters by 9.48%, and significantly enhance the performance of the compressor cascade.

In this paper, based on the airflow improvement mechanism of dragonfly wing veins, a vortex generator is designed at the leading edge of the suction surface to improve the flow condition of compressor cascades. The influence of the placement positions and geometric dimensions of the vortex generators on the flow field structure and aerodynamic performance is investigated by numerical simulation. The research reveals that vortex generators at the leading edge of the suction surface can generate induced vortices near the end wall, suppressing the accumulation of low-energy fluid in the corner region. This results in a backward shift of the separation initiation point, a reduction in the corner separation region along the pitch direction, and a reduction in flow loss. The vortex generators exhibit favorable characteristics with positive incidence angles. However, when the incidence angle is below the minimum loss incidence angle, the vortex generators increase the flow losses of the cascade. Optimum performance is achieved when the vortex generators are positioned at the start of the corner separation. The flow control influence initially increases and then decreases as the height of the vortex generators increases. Similarly, the control impact is enhanced and then weakened as the placement position moves away from the suction surface. The flow losses decrease by 10.3% when the vortex generators are placed at the junction between the end wall recirculation and the mainstream region at a height equal to 2% of the blade height.

This paper examines the effect of labyrinth seal structure on the evolution of vortex systems and the performance of the cascade. It is found that the labyrinth seal leakage leads to the circumferential development of the separation vortex, and the axial influence region of the concentrated shedding vortex also expands, which increases the flow loss and reduces the diffuser capacity. Among all the cases, the deteriorating effect of the cavity without a labyrinth seal is the most significant. This results in an 83% increase in total pressure loss compared to the prototype cascade. The straight tooth labyrinth and the straight tooth labyrinth with block structures can effectively reduce the leakage from the sealing cavity and weaken the deterioration caused by labyrinth seal leakage. Among these schemes, the straight tooth with block scheme has the most considerable effect, resulting in a 19% reduction in total pressure loss. As the incidence angle increases, the recirculation zone on the end wall of each scheme gradually shrinks toward the leading edge. Meanwhile, the static pressure rises, and the velocity decreases near the leading edge. Compared with the straight tooth scheme, the straight tooth with block scheme can reduce the high-loss zone by 14% at most. In addition, as the sealing clearance gradually increases, the inhibitory effect of the straight tooth with block scheme on the deterioration of cascade performance caused by the labyrinth sealing cavity is gradually enhanced compared to the straight tooth structure. The improvement effect is optimal under 0.5 mm sealing clearance.

This study investigates the effects of interstage seal structures with various inlet and outlet angles on the vortex structure and performance of high-load cascades. The analysis indicates that an increase in the angle between the interstage seal outlet and inlet and the incoming flow direction reduces total pressure loss and interstage leakage. As the inlet angle increases, the spanwise concentrated shedding vortex diminishes due to the suction effect generated by the interstage seal inlet. Concurrently, the passage vortex expands pitchwise, increasing root blockage and associated losses. However, the flow loss within the mid-span mainstream region is observed to be considerably reduced. As the outlet angle increases, the airflow aligns more closely with the flow direction. This results in the recirculation zone and the suction surface vortex shifting toward the leading edge root. Consequently, the pitchwise separation vortex expands while its height decreases, which reduces loss within the mid-span. The interstage seal outlet and inlet are oriented at 150° to the incoming airflow direction, effectively decreasing the corner separation height. This configuration minimizes flow loss in the mid-span and enhances the flow capacity. The reduction in total pressure loss demonstrates superior performance compared to single action, with a total pressure loss decrease of 2.29% relative to the original scheme. Furthermore, the enhancement of the passage vortex results in a deterioration of the vortex near the root. This change reduces the pressure difference between the interstage seal outlet and inlet, consequently decreasing interstage leakage.