The control of the tip vortex, generated by a rectangular NACA 0012 wing, via tip-mounted half-delta wings (HDWs), of different slendernesses Λ, root chords cr, and deflections δ, was investigated experimentally at Re = 2.45 × 105. The results show that regardless of Λ, cr, and δ, the addition of HDWs consistently led to a diffused tip vortex. The degree of diffusion was, however, found to increase with decreasing Λ and cr. HDWs with cr ≤ 50% of the baseline-wing chord c caused a rapid diffusion of vorticity and rendered a weak circulation flowlike tip vortex, suggesting an enhanced wake-vortex decay and alleviation. The cr = 0.5c HDW also produced an improved lift-to-drag ratio. A unique double-vortex pattern also exhibited downstream of the cr ≤ 50%c HDW wings. The interaction and merging of the double vortex were expedited by upward HDW deflection.

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The appropriate coolant mass flow of turbine blade rim seal has become an important issue as turbine blades are exposed to increasingly higher thermal load owing to increased turbine inlet temperature. If the coolant is deficient, hot gas ingresses to the rim seal, or if sufficient, the efficiency of turbine decreases. Therefore, we analyzed sealing effectiveness of rim seal derive appropriate coolant mass flow rate at various conditions. The experimental facility was modified from one designed for an aero-engine gas turbine. Rotational Reynolds number varied from 3 × 105 to 5 × 105 based on rotational speed. Pressure was measured at various locations in the shroud, endwall, and rim seal. CO2 concentration was measured at various rim seal locations to analyze sealing effectiveness. Measured results showed that 1.35% coolant mass flow rate of rim seal exhibited a little ingress effect, whereas lower coolant mass flow rates exhibited higher ingress effect. A predicted correlation for sealing effectiveness of rim seal was derived at various rotational Reynolds number and coolant mass flow rate. The correlation will be useful for turbine cooling design, helping to predict sealing effectiveness of rim seals during preliminary design processes for new gas turbines.

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