The introduction of splitter blades (splitters) in the impeller represents a possible way to improve the head and efficiency of centrifugal turbopumps. Splitters decrease flow slip, deviation, blockage and losses at the impeller discharge by reducing the displacement flow and the adverse pressure gradient it induces on the boundary layers (BLs) developing on the pressure sides of the full blades. These benefits are to be balanced against the introduction of additional flow blockage and losses. It is therefore of interest to investigate which splitter blade geometry (position and length), if any, is most effective to best exploit the potential advantages of adding splitter blades to a centrifugal impeller. To this purpose a quasi-3D, reduced-order method, previously developed for preliminary prediction of the geometry and performance of centrifugal turbopumps, is extended to account for the introduction of splitter blades for the purpose of investigating their influence on the hydraulic performance of these machines. Splitters with radial leading edges and the same shape as the full blades are introduced in the six-bladed backswept impeller of the VAMPIRE turbopump, a high-efficiency machine previously used for experimental validation of the original version of the flow model. The results highlight the most relevant action mechanisms of splitter blades in affecting the turbopump performance and provide general indications on their most effective design for performance improvement. As a consequence of the evolution of the BLs in the blade channels, relatively longer splitters located closer to the pressure sides of the full blades are more efficient at and above design flow, while the reverse is the case at high blade loadings. The results also indicate that the introduction of splitter blades only marginally improves the performance of the already optimized VAMPIRE pump in view of its small residual margins for performance gains.
Theoretical Optimization of Splitter Blade Geometry in High-Efficiency Centrifugal Turbopumps
APOLLONIO, ALESSANDRO;Pasini A.;Valentini D.;d’Agostino L.
2019-01-01
Abstract
The introduction of splitter blades (splitters) in the impeller represents a possible way to improve the head and efficiency of centrifugal turbopumps. Splitters decrease flow slip, deviation, blockage and losses at the impeller discharge by reducing the displacement flow and the adverse pressure gradient it induces on the boundary layers (BLs) developing on the pressure sides of the full blades. These benefits are to be balanced against the introduction of additional flow blockage and losses. It is therefore of interest to investigate which splitter blade geometry (position and length), if any, is most effective to best exploit the potential advantages of adding splitter blades to a centrifugal impeller. To this purpose a quasi-3D, reduced-order method, previously developed for preliminary prediction of the geometry and performance of centrifugal turbopumps, is extended to account for the introduction of splitter blades for the purpose of investigating their influence on the hydraulic performance of these machines. Splitters with radial leading edges and the same shape as the full blades are introduced in the six-bladed backswept impeller of the VAMPIRE turbopump, a high-efficiency machine previously used for experimental validation of the original version of the flow model. The results highlight the most relevant action mechanisms of splitter blades in affecting the turbopump performance and provide general indications on their most effective design for performance improvement. As a consequence of the evolution of the BLs in the blade channels, relatively longer splitters located closer to the pressure sides of the full blades are more efficient at and above design flow, while the reverse is the case at high blade loadings. The results also indicate that the introduction of splitter blades only marginally improves the performance of the already optimized VAMPIRE pump in view of its small residual margins for performance gains.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
