Implementation of Flow Control Methods for Design of Connecting Duct of Annular Sector Cascade Tunnel

The present study discusses the effect of various flow control methods implemented to develop an intermediate turbine duct (ITD), providing a continuous flow path between the contraction duct of the wind tunnel and the annular sector cascade (ASC) test section to deliver the required flow. The S-shaped diverging passage of the ITD with continuously increasing mean radius imposes a major challenge to achieving the required inlet flow angle with periodicity at the entry of the ASC. The numerical study was performed in ansyscfx to analyze the effect of active and passive flow control methods on the ITD exit flow delivered to the ASC test section. It was found that inlet guide vanes (IGVs), incorporated within the ITD as a passive flow control method, direct the flow through ITD, and approximately required inlet flow condition with reasonable periodicity was achieved at the entry of the ASC test section. However, the opening slot on the casing endwall, an active flow control method, shows the adverse effect on the flow angle distribution at the entry of the ASC test section. The change in axial spacing between IGVs and the test vane cascade shows a negligible effect on the cascade entry flow field. The experimental flow field measurement performed using a five-hole pressure probe showed that IGVs successfully directed the flow through the ITD, precisely meeting the requirements at the test section. The surface oil flow visualization confirms the formation of various flow features captured in the computational study.