Effect of Winglet-Shroud Tip With Labyrinth Seals on Aerodynamic Performance of a Linear Turbine Cascade

Abstract

This paper is a continuous study of a previously investigated novel winglet-shroud (WS) tip configuration. Two additional sealing fins are fixed on the WS tip to further reduce tip leakage. This configuration is referred to WS with seals (WSS) tip. Secondary flow structures and total pressure loss coefficients on a transverse plane downstream of the blade trailing edge are measured. Flow in a blade cascade is also numerically simulated to obtain more information of flow fields. Compared with the WS tip, both experimental and numerical results show that the WSS tip can further improve the aerodynamic performance as expected. Relative to the plain tip, the WSS and WS tips can reduce total pressure loss on one plane downstream of the blade trailing edge by 50% and 28%, respectively. This is mainly due to reduced intensity of tip leakage vortex (TLV). For the tip leakage mass flow rate, the WS tip decreases it by 33.6%, while the implement of two additional sealing fins contributes to an extremely high reduction of 88.7%. This demonstrates that the use of sealing fins is effective to control the tip leakage flow and improve flow fields. In addition, a deeper analysis by applying a normalized helicity scheme to identify the evolution of different vortices and by tracing trajectories of the fluid near the tip offers credible supports for results.

Numerical investigations on leakage performance and flow mechanism of spiral groove seal for shrouded blade in axial turbine

“…Harvey 9 designed a partial shroud structure with winglets for the high-pressure turbine, which can significantly reduce blade cooling requirements and tip leakage loss. Porreca et al, [10][11][12] Rebholz et al, 13 and Liu 14,15 studied shroud reduction on the turbine blade, by comparing the influences of full and partial shroud structure on leakage flow and turbine performance, improved and optimized partial shroud structures were brought up. Li 16 applied four configurations with or without labyrinth seal arranged on casing and rotor blade tip for computational simulations and found that the double-side labyrinth seal achieved the highest turbine stage efficiency.…”

Numerical Investigation on Flow Characteristics and Aerodynamic Performance of a 1.5-Stage SCO2 Axial-Inflow Turbine with Labyrinth Seals

“…The results agreed utterly with the test data. A new type of radial seal was proposed by Zhang [16], and the large flow resistance and low leakage were achieved compared with the traditional LS. Liu [17] concluded that the LS arranged on the top of the shroud can significantly reduce the total pressure loss.…”

Effects of leakage vortex on aerodynamic performance and loss mechanism of steam turbine

“…The mixing process between main flow and leakage flow was also studied. [10][11][12] The three-dimensional unsteady numerical simulation method was adopted by Cao et al 13,14 to study the flow field in the blade tip clearance and the spectral characteristics of leakage vortex in the seal cavity. The above researches only corrected the leakage loss, without considering that the leakage flow not only leads to the mixing loss, but also changes the downstream stator flow field and causes additional secondary flow loss.…”

“…The mixing process between main flow and leakage flow was also studied. 10–12 The three-dimensional unsteady numerical simulation method was adopted by Cao et al. 13,14 to study the flow field in the blade tip clearance and the spectral characteristics of leakage vortex in the seal cavity.…”