Influence of slashface leakage coupled with quasi-labyrinth seal technique on gas turbine endwall aerothermal performance and blade suction side surface phantom cooling

Abstract

<jats:p> Quasi-labyrinth seal technique was innovatively adopted to control the slashface flow, and the effect of slashface leakage on endwall aerothermal performance and blade suction side surface phantom cooling was numerically investigated. Simulations of five different labyrinth seal lengths ( L<jats:sub>s</jats:sub>) and three coolant momentum flux ratios ( I) were conducted by computationally solving the Reynolds-averaged Navier–Stokes equations coupled with the shear stress transport k-ω turbulence model. The results show that the slashface coolant can be accelerated and conveyed downstream inside the slashface carried by the ingested mainstream and passage vortex. By setting up the quasi-labyrinth seal composed of a series of aperture cavities along the slashface, the coolant downstream transportation can be largely weakened, and the labyrinth seal with various lengths all have the potential to move the endwall coolant coverage toward upstream. When I = 0.48, the coolant downstream migration is severest and it has the best coverage on the endwall with seal. The laterally averaged cooling effectiveness is elevated for the fore part endwall but decreased for the back part endwall after sealing, and the highest cooling effectiveness is increased by 5% for 0.6 L<jats:sub>s</jats:sub> seal. The 0.6–1.0 L<jats:sub>s</jats:sub> seal has the approximate effect and is better than 0.4 L<jats:sub>s</jats:sub> seal, and 0.6 L<jats:sub>s</jats:sub> seal has the best outcome considering the countering effects of structural strength and endwall cooling performance. For 0.6 L<jats:sub>s</jats:sub> sealed case, the high heat transfer level caused by coolant attachment is enhanced by 3.5% when I = 0.48 but decreased by 3.3% and 4.4% when I = 0.96 and 1.42 compared with baseline case. The low heat transfer caused by horseshoe vortex separation is enhanced when I = 1.42 for the sealed case. The quasi-labyrinth seal mainly weakens the back part suction side phantom cooling performance, and the well phantom cooling region moves upstream with the increase of I. The averaged phantom cooling effectiveness is decreased by 0.56%, 0.3%, and 1.44% when I = 0.48, 0.96, and 1.42 for the sealed cases. The results provide the gas turbine designers a better insight into improved slashface leakage control as well as its detailed surface cooling effects. </jats:p>

Turbine vane endwall aerothermal and film cooling performance considering realistic swirling inflow conditions

“…Introducing coolant from the inevitable slot between the combustor and the turbine NGV or the mid-passage gap between two neighboring vanes, can protect the endwall and prevent the ingestion of the hot main flow at the same time. 18 Moreover, compared with traditional gap structure, the leakage from the mid-passage gap with a Quasi-labyrinth seal was found to have a better endwall cooling effect by Zhang et al 19 Discrete film hole implemented on the endwall is an additional cooling method to protect some local area. The endwall cooling performance of the single row of the film holes was investigated by Xu et al 20 They emphasized that the vortex from the upstream step decreased the film cooling effectiveness obviously.…”

“…Although ideal uniform inflow conditions are often implemented in previous research, 17,19,20,22 the realistic vane inflow conditions with highly swirling flow and non-uniform temperature lead to a significant influence on vane endwall performance. 27 Thus, the endwall aerothermal characteristics and film cooling performance should be investigated considering the realistic swirling inflow effect.…”