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) 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.
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.
[This abstract was generated with the help of AI]
Keywords
PBCF ; Propeller ; Propeller Boss Cap Fins ; CFD ; RANS ; Boss Cap Fins ; Optimisation ; Numerical ; 3D
Documents