Passive control of laminar separation bubble with spanwise groove on a low-speed highly loaded low-pressure turbine blade

Abstract

LES (Large-Eddy Simulation) computations were preformed to investigate the mechanisms of a kind of spanwise groove for the passive control of laminar separation bubble on the suction surface of a low-speed highly loaded low-pressure turbine blade at Re = 50,000 (Reynolds number, based on inlet velocity and axial chord length).Compared with the smooth suction surface, the numerical results indicate that: (1) the groove is effective to shorten and thin the separation bubble, which contributes the flow loss reduction on the groove surface, by thinning the boundary layer behind the groove and promoting earlier transition inception in the separation bubble; (2) upstream movement of the transition inception location on the grooved surface is suggested being the result of the lower frequency at which the highest amplification rate of instability waves occurs, and the larger initial amplitude of the disturbance at the most unstable frequency before transition; and (3) the viscous instability mode is promoted on the grooved surface, due to the thinning of the boundary layer behind the groove.

Influence of a groove-structured vortex generator on the drag reduction characteristics of a multiphase pump

“…Frontiers in Energy Research frontiersin.org gas content does not affect the pressure distribution law on the suction side of the blade, this figure represents the design conditions of IGVF = 40%, with the pressure coefficient distribution pattern of the suction surface at 0.5 times the blade height position. The pressure coefficient gradually increases after the position of X/L = 0.3, which is regarded as the position where the bubbles flow back into the separation zone (Luo et al, 2009). Obviously, the position of X/L = 0.5, where the rate of change of the pressure coefficient decreases, is the reattachment point of the mixed media, which is consistent with the separation area obtained numerically.…”

“…Hualing et al explored the control mechanism of the vortex generator on the separation of bubbles on the suction side of the turbine blade by numerical analysis under the condition of Reynolds number Re = 5×10 4 . Their obtained results showed that the vortex generator delayed the separation, which helped to reduce the loss of fluid energy on the groove surface (Luo et al, 2009). Shen et al arranged grooves in a pressurized water chamber of a centrifugal pump and found that the grooves reduced the flow resistance and improved the anti-cavitation performance of the pump (Shen and Chu, 2019).…”

Numerical Studies on the Effect of Leading Edge Tubercles on a Low-Pressure Turbine Cascade

“…The size of the separation bubble is suppressed and the loss of the blade is reduced. Passive flow control methods mainly include the introduction of rectangular bars [10], two-dimensional spanwise grooves [11,12], three-dimensional dimples [13], and surface roughness [14], which could induce the boundary layer to become turbulent and then achieve the purpose of separation suppression and loss reduction. Although the active control methods have the advantages of good adaptability and high controllability compared with the passive control methods, the cost is too high and the system is too complex to be realized, so it is not suitable for engineering practice for the time being.…”

Studies on Two-Dimensional Contouring of High-Lift Turbine Airfoil Suction Surface as Separation-Control Device: Separation Suppression Under Steady-State Flow Conditions

“…Also, surface roughness, tripping wire and surface special treatment like dimple, groove or 2D/3D protrusion are rather conventional but still attracting attention from researchers and designers [18]- [22]. Luo et al [21] carried out LES (Large-Eddy Simulation) analysis to examine how surface treatment with spanwise (2 dimensional) groove on a highly loaded LP turbine airfoil affected the separation bubble. They suggested that the groove can change the instability mechanism, which prompts transition inception of the separation bubble, although no experimental evidence was shown there.…”