PG-EAM - Graduate Program in Aeronautical and Mechanical Engineering
PT EN
PhD Thesis 2022

Development and application of blade desensitization techniques in a hydraulic axial turbine used as a booster in a turbopump

Author

Daniel da Silva Tonon

Advisor

Concentration Area

Propulsão Aeroespacial e Energia

Defense Date

17/02/2022

Thesis Number

78296

Abstract

Tip leakage is an undesirable phenomenon that occurs in turbomachines. Over the years, different strategies have been developed to reduce this flow, including desensitization techniques. These techniques have been studied in gas turbines for years, but no work in the literature has evaluated these techniques in hydraulic axial turbines. This work presents a numerical solution and its analysis for different tip blade desensitization techniques, used in a hydraulic axial turbine used as a booster in a rocket turbopump engine. The turbomachine studied is the first stage of the hydraulic axial turbine used in the Low Pressure Oxidizer Turbopump (LPOTP) of the Space Shuttle Main Engine (SSME). The numerical simulations were performed using the commercial CFD solver CFX v.19.2. The computational meshes were generated using the ICEM v.19.2 software. Initially, the computational model was validated, using the experimental results published by the National Aeronautics and Space Administration (NASA). The flat tip model satisfactorily represents the studied turbine; comparing the experimental and numerical results, no errors greater than 4% were recorded, and at the design point the deviation was only 1.34%. Three different desensitization techniques were evaluated, being: squealer, winglet, and the combination of both, called squealer-winglet. Regarding the squealer technique, a parametric analysis was performed considering its cavity depth and rim thickness variation. It was found that the squealer cavity depth has more influence on the stage performance than its rim thickness, and there is a tendency that the greater the cavity depth, the greater the stage efficiency. One of the Squealer geometries analyzed allowed an average efficiency increase of 1.43% over the entire turbine operational range. Likewise, a parametric analysis of the winglet technique was also performed, varying its thickness and width. It was found that the element thickness has more influence on the stage efficiency than the Winglet width, and the greater the element thickness, the greater the stage efficiency. Some studied Winglet geometries allowed an average increase above 2.00% in the stage efficiency. The squealer-winglet parametric analyzes were developed varying only the squealer cavity depth and the winglet thickness, as these were shown to be the parameters with the greatest impact on the studied turbine efficiency. Unfortunately, the combination of the first two techniques did not add the benefits found in the Squealer and Winglet geometries separately. The best results found with the Squealer-Winglet geometries allowed an average increase of 1.26% in the stage efficiency, that is, lower than those found for the other techniques.

Keywords

Turbinas axiais Turbinas hidráulicas Lâminas de turbinas Dinâmica dos fluidos computacional Máquinas hidráulicas Engenharia mecânica