Innovative Approach for Design and Development of Annular Sector Cascade Tunnel using Numerical Analysis

The aerodynamic and aeroelastic study of flow through turbomachine blade passage is the most essential requirement for the development of fuel-efficient gas turbine engines. The use of various cascade tunnels is very common to predict the flow behaviour within the blade passage and at the exit of cascade blades. The present work focuses on the innovative method for the development of annular sector cascade wind tunnel of exit Mach number 0.62 for such applications, using the computational study. The flow behaviour within the tunnel was numerically analysed using commercial software, ANSYS CFX®. To meet the special requirements/constraints like available laboratory space and height of the test section, the numerical study was explored for various design iterations. The use of a wide-angle diffuser with inclination was one of the challenges which were addressed using a porous screen. The modelling for the screens and honeycomb section are the most challenging aspects, which were resolved using porous media option with porosity and permeability as an input. The numerical method discusses to define the outlet flow domain as a half-spherical shape with opening boundary condition to simulate the actual exhaust flow condition. The cost-effective honeycomb section, with square-shaped cells, which are easy to manufacture and clean, worked effectively to straighten the flow by reducing velocity fluctuations in the lateral and longitudinal direction. The settling chamber screens reduced the streamwise velocity fluctuations, and accelerating flow in the contraction duct reduced the spatial variation. Near about less than 7% RMS change in the contraction duct exit velocity was achieved as it is the need to test the turbine blades. It is strongly believed that the various design aspects will help future designers for selecting various geometrical parameters for the design and development of such cascade tunnels.