Numerical investigation of the effects of turbulence intensity and turbulence length scale on the flow field of high-pressure turbine blade cascades

Functioning as a turbine positioned immediately after the combustion chamber outlet, the high-pressure turbine experiences a profound impact on its internal flow field quality and development from the characteristics of the airflow at the combustion chamber exit. This study aims to explore the influence and mechanisms of turbulent length scales (TLS) on the internal flow field characteristics of the high-pressure turbine stator under varying turbulent features at the combustion chamber exit. Investigating two turbulent intensities (Tu) of 1% and 25%, the study assesses the effects of 17 turbulent length scales on the turbine's internal flow field characteristics. Several representative scales are selected for analysis to understand their impact on the turbine's secondary flow patterns and boundary layers in the endwall, along with the mechanisms. The findings reveal a notable influence of the TLS on the endwall secondary flow. At Tu = 1%, TLS has minimal impact on the secondary flow and the suction side boundary layer. However, at Tu = 25%, increasing TLS significantly diminishes the strength of the endwall secondary flow, with a rise in TLS leading to a substantial reduction of up to 89.5% in the peak intensity of secondary flow. Nonetheless, this increase in TLS also accelerates boundary layer thickening, resulting in pronounced profile loss. Furthermore, TLS restricts the migration of secondary vortices towards the blades due to the rapid boundary layer thickening, which becomes particularly significant in profile loss under heightened Tu.