Three-dimensional flow of a turbine nozzle at low Reynolds numbers (effect of Reynolds number on loss and flow mechanisms)

摘要

Blade Reynolds numbers for the turbine stage of small and micro gas turbine engines can drop below 10{sup}5. At these low Reynolds number conditions, the boundary layer is dominated by laminar flow and is susceptible to flow separation, which is associated with increased loss and reduced performance. The characteristics such as boundary layer separation, reattachment and secondary flow can not be easily predicted by computational analyses, therefore quantitative experimental data will make an important contribution to establish theoretical works. In this study, detailed experiments under low Reynolds number conditions, Re{sub}(out)=4.5 × 1O{sup}4～27.1 × 1O{sup}4, have been conducted to evaluate the performance of an annular nozzle of axial-flow turbine. The nozzle wake and secondary vortices were measured using a miniature five-hole pressure probe and a single element hot-wire anemometry. The Reynolds number has a significant effect on the total pressure loss and the aerodynamic mechanisms of turbine nozzle at low Reynolds numbers. The total pressure loss and turbulence intensity increase rapidly and the nozzle exit flow velocity and flow angle decrease as Reynolds number falls.