Modelling and Optimisation of Free Running Axial Turbine for Flow Measurements
Authors
Hansen, Nick Høy ; Villamar Cabezas, Daniel Esteban
Term
4. term
Education
Publication year
2017
Pages
94
Abstract
Dette speciale udvikler og validerer en CFD-baseret model for en friløbende aksial turbineflowmåler i en Grundfos CR 10 pumpe. Modellen forudsiger omdrejningstal og tryktab ved at balancere det væskedrevne moment mod skovl- og sensortræk samt en separat modelleret lejefriktion; herved undgås eksperimentel måling af omdrejningstal i designfasen. Modellen valideres mod laboratorieforsøg og følsomhedsanalyser af nøgleparametre; den rammer den målte rotationshastighed, men med stigende fejl ved højere volumenstrømme. Efter validering bruges modellen til geometrioptimering, hvor soliditeten reduceres ved at skære skovlantal fra 8 til 3; en 3-skovelet prototype 3D-printes og testes. Sammenlignet med 8 skovle giver 3 skovle lavere tryktab og reducerer i intervallet 4–17 m3/h effektivitetstabet med i gennemsnit 1,49%, svarende til ca. 57,7% af tabet for 8 skovle. Modellen viser dog strømningsseparation på skovlene; en ændring af skovlvinklen i simuleringer giver lovende forbedringer. Arbejdet udvider den eksisterende modelleringsramme for turbineflowmålere og demonstrerer modellen som et praktisk værktøj til geometrioptimering; fremtidigt arbejde bør finjustere skovlvinkler og afprøve modellen på hele CR-serien.
This thesis develops and validates a CFD-based model for a free-running axial turbine flow meter in a Grundfos CR 10 pump. The model predicts rotational speed and pressure drop by balancing the fluid-driven torque against blade and sensor drag and a separately modeled bearing friction, removing the need to measure speed experimentally during design. It is validated against laboratory tests and accompanied by sensitivity analyses of key parameters; it reproduces measured rotational speeds, with errors that grow at higher flow rates. After validation, the model is used to guide geometry changes by reducing solidity via a blade-count reduction from eight to three; a 3-bladed prototype is 3D-printed and tested. Compared with eight blades, three blades lower head loss and, over 4–17 m3/h, reduce the efficiency loss by an average of 1.49% (about 57.7% of the loss with eight blades). The model also indicates flow separation on the blades; adjusting blade angle in simulation shows promising improvements. The work extends the modelling framework for turbine flow meters and demonstrates a practical tool for geometry optimisation; future work should refine blade angles and broaden validation across the CR pump range.
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