Experimental and numerical investigation on suppressing end-clearance leakage flow for variable nozzle turbine guide vane

Variable geometry turbine (VGT) exists in turbocharged gas engines to solve the problems of insufficient low-speed torque and poor transient response. However, there is a performance penalty associated with the end-wall clearance required for the movement of the guide vanes. Aiming at suppressing the end-wall clearance leakage flow loss to improve turbine performance, a novel scheme of end-clearance sealed guide vane (ESGV) is proposed and the effect assessment of this configuration is studied numerically and experimentally in a real variable geometry turbine. The numerical predictions reveal the three-dimensional leakage flow characteristics associated with the sealed end-wall clearance that optimizes the mixing process between the clearance leakage flow and the main flow and further improve the design and off-design performance of the turbine. Results exhibit that the relative leakage flow in the ESGV turbine is reduced by 26.81%, 7.33%, and 0.99% for 10%, 50%, and 90% nozzle openings, respectively, compared to that of the original turbine. Moreover, most of the leakage loss is concentrated in the groove clearance of the disk. The efficiency advantage of 20% and 4.4% points for the ESGV turbine at the peak efficiency point under 10% and 50% opening conditions, respectively. Besides, an experimental investigation is carried out to further verify the ESGV turbine performance predictions and analytical assumptions. Overall, the ESGV is found to be the best choice for the variable turbine guide vanes. The present results can provide valuable references for the vane-end clearance design of variable geometry turbines.