An Investigation of the Performance and Internal Flow of Variable Nozzle Turbines with Split Sliding Guide Vanes

Abstract

In order to effectively weaken the leakage flow and shock intensity of traditional “swing” type guide vanes in a variable nozzle turbine, a new flow control device named the “split sliding guide vane” (SSGV) is studied in the present work. Steady and unsteady calculations were carried out on both the SSGV and base model at 10%, 40%, and 100% open positions. The shock test was performed to verify the accuracy of the numerical method. The results showed that at 10%, 40%, and 100% open positions, the leakage flow of the SSGV was 43%, 51%, and 40% of that of the base model, respectively. When 10% open, the turbine efficiency increased by 12%, compared with the base model, since the SSGV could effectively inhibit the clearance leakage flow. Due to the increased distance between the rotor and guide vane, the shock intensity of the SSGV was only 52% of that of the base model when 40% was open. The SSGV could reduce the static pressure loss on the guide vane pressure surface, but for the guide vane suction surface, the static pressure distribution appeared in a “W” shape due to the influence of the vane profile. Finally, the flow in the rotor was studied, which showed that the weakening of the shock and reduction of the clearance leakage flow in the guide vane were also beneficial for the strength of downstream rotor blades.

Numerical Analysis of the Effects of Grooved Stator Vanes in a Radial Turbine Operating at High Pressure Ratios Reaching Choked Flow

“…These shock waves can be weakened by small changes in the stator geometry, as was reported in the work of Sonoda et al [22] by a locally high concave curvature and a small groove on the pressure surface (PS) near the TE, which lead to a double shock structure and reduce the TE loss and shock loss. Yang et al [23]analyzed the used "split sliding guide vane" (SSGV) to weaken the leakage flow and shock intensity of the traditional stator vanes. Thus, the global performance of the turbine was improved, especially at small guide vane openings, reporting and increase of 12% and a decrease of 57% of the vanes clearance leakages flow.…”