Analytical, Experimental and Mechanical Evaluation of Free Rotating Vaneless Diffusers

摘要

Experimental testing of a model free rotating vaneless diffuser rig to determine diffuser loss coefficients and static pressure recovery under braked and free rotating conditions was conducted. The rig was operated at entry Mach numbers up to unity with both vaned and vaneless diffusers installed downstream. Two rotating diffuser widths were tested. A significant improvement in diffuser performance was achieved under free rotating conditions, even though large wakes generated by upstream stationary swirl nozzles were present. Overall static pressure recovery for the complete diffusion system increased approximately 20%, at free rotating conditions corresponding to a tangential velocity ratio (diffuser/incident stream) of 0.43. The total pressure loss reduction between braked and rotating conditions correlated with theoretical studies. A mechanical design study to examine methods of integrating the rotating diffuser into a complete gas turbine was also conducted and a feasible preliminary design identified. (Author)