Numerical simulation research of aerodynamic performance of cantilevered variable geometry turbine

At present， the cantilevered variable nozzle vane （VNV） is already applied in practice. To explore the aerodynamic characteristics of cantilevered variable geometry turbine （VGT）， the aerodynamic performances of two kinds of VGTs are mainly compared and studied by numerical simulation approach. A conventional VGT and cantilevered VGT is modified from a turbine with constant outer flow path radius. Steady numerical simulation is applied to the aerodynamic calculations of the two VGTs. Then the influences of VNV spherical wall， end clearance and stagger angle change on the VGT performance are analyzed. The results showed that the spherical wall improved the turbine mass flow rate by approximately 1.16% and promoted efficiency by 0.003 9. Compared with the spherical wall turbine， the cantilevered VGT increased mass flow rate by approximately 1.47%， while reduced efficiency by 0.024 2. The conventional VGT increased mass flow rate by approximately 0.24%， while reduced efficiency by 0.007 0. When VNV opened by 1°， VGT mass flow rate improved by approximately 0.37 kg/s. The clearance of VNV could improve turbine mass flow rate and control radial secondary flows at end zones to some degree. The cantilevered VNV hub had large leakage loss， while vane end adjusting shaft could control leakage loss.