Optimum Design of Propeller Boss Cap Fins (PBCF) by Model Scale Numerical Evaluation
Authors
Sandland, Marcus Pless ; Rosenvinge, Christian Kjær
Term
4. term
Education
Publication year
2021
Submitted on
2021-05-28
Pages
102
Abstract
Propeller Boss Cap Fins (PBCF) are small fins mounted on a propeller’s hub cap to weaken the strong hub vortex—the swirling flow behind the hub—and thus improve propeller efficiency. This project reports the design and optimization of PBCF for a specific controllable pitch propeller (CCP) using model-scale simulations: steady-state 3D RANS analyses (a standard CFD method for turbulent flow) in the software STAR-CCM+. The numerical model was validated against empirical data both with a rudder attached and in open-water conditions, and the agreement was sufficient to use the model for further analysis. Based on a literature review, a geometric basis for the PBCF was defined and tested in the model. Among several hydrofoil sections, NACA 4412 performed best. A separate optimization was carried out for each parameter; fin span height, circumferential position around the hub, and axial position along the shaft were the most influential. The resulting optimized PBCF delivered at least a 1.0% efficiency increase across a wide range of ship speeds. Across different advance ratios (a measure of ship speed relative to propeller rotation), the efficiency improvement was 0.59–1.19%. Pressure map comparisons showed that the induced hub vortex was completely eliminated.
Propeller Boss Cap Fins (PBCF) er små finner, der monteres på propellerens navhætte for at svække den kraftige navhvirvel – den roterende strømning bag navet – og dermed øge propellens virkningsgrad. Dette projekt beskriver design og optimering af PBCF til en bestemt kontrollerbar stigningspropel (CCP) ved hjælp af modelskal-simuleringer: stationære 3D RANS-beregninger (en standard CFD-metode til turbulent strømning) i softwaren STAR-CCM+. Den numeriske model blev valideret mod empiriske data både med ror monteret og i åbent vand, og overensstemmelsen var tilstrækkelig til at bruge modellen videre. På baggrund af litteraturstudier blev en geometrisk basis for PBCF fastlagt og analyseret i modellen. Ved at afprøve forskellige hydrofoil-profiler viste NACA 4412 sig bedst. For hver enkelt parameter blev der gennemført en separat optimering; finens højde (spænd), vinkelpositionen rundt om navet (omkredsposition) og længdepositionen langs aksen (akselposition) var de mest betydningsfulde. Den samlede, optimerede PBCF gav mindst 1,0 % højere virkningsgrad over et bredt spænd af skibshastigheder. For forskellige fremskydningsforhold (advance ratio, et mål for forholdet mellem skibets hastighed og propellerens omdrejninger) var forbedringen 0,59–1,19 %. Sammenligning af trykkort viste, at den inducerede navhvirvel blev fuldstændig elimineret.
[This apstract has been rewritten with the help of AI based on the project's original abstract]
Keywords
PBCF ; Propeller ; Propeller Boss Cap Fins ; CFD ; RANS ; Boss Cap Fins ; Optimisation ; Numerical ; 3D