Winglet Geometries Applied in Rotor Blades of a Hydraulic Axial Turbine Used as Turbopump: A Parametric Analysis

Turbines are rotating machines that generate power by the expansion of a fluid; due to their characteristic these turbomachines are widely applied in the aerospace propulsion systems. Since due to the clearance between rotor blade tip and casing, there is a leakage flow from blade pressure to suction sides, which generates an energy loss. There are different strategies that can be applied to avoid part of this loss, one of them is by the application of the called desensitization techniques. The application of these techniques on gas turbines have been widely evaluated, however, there is a lack of these analyzes for hydraulic turbines. This work is a sequence of previous analyzes developed for the first stage of the hydraulic axial turbine used on the Space Shuttle Main Engine (SSME) Low Pressure Oxidizer Turbopump (LPOTP). The last work analyzed the application of squealer geometries at rotor tip. In the present paper, the winglet geometry techniques were investigated based on three-dimensional flowfield calculation. The commercial CFX v.19.2 and ICEM v.19.2 software were used, respectively, on the numerical simulations and computational meshes generation. Experimental results published by the National Aeronautics and Space Administration (NASA), and data from previous works, were used on the computational model validation. The parametric analysis was done by the variation in the winglet thickness and width. The results obtained shown that increasing the winglet thickness, the stage efficiency is also increased. However, its width geometrical dimension almost does not impact this result. It was verified an efficiency increase of 2.0%, over the entire turbine operational range. It was found that the proposed geometries application also changes the cavitation occurrence along the stage, which is a relevant result, since it can impact the turbine life cycle.