Boss Cap Research Articles

Computational fluid dynamics driven surrogate model to predict hydrodynamic and acoustic properties of propeller boss cap fins

A novel method is proposed to predict the hydrodynamic and acoustic properties of propeller boss cap fins (PBCF) based on computational fluid dynamics (CFD) and surrogate models. The propulsive performance and radiated noise of the B-series propeller equipped with PBCF under open-water and hull-propeller coupling conditions are predicted and analyzed. The transient calculations are performed to generate accurate sample data for the surrogate model based on the Unsteady Reynolds Averaged Navier–Stokes and Ffowcs Williams–Hawkings equations. The response surface, polynomial, and Kriging models are used to learn sample data and output predictions. The relationship between inputs and outputs can be established from local data, which enables to obtain arbitrary response results in the global range. The hydrodynamic performance and radiated noise are compared for configurations with and without PBCF. PBCF improves the open-water efficiency by more than 1.5% at medium to high advance velocities. For the self-propulsion efficiency, over 5% improvement is achieved under ideal working conditions. In addition, PBCF has a directional effect on the radial and axial radiated noise, with better noise reduction in the axial direction. The difference between the axial and radial spectrums is significant, especially near the first blade passing frequency.

Effects of propeller boss cap fins on hydrodynamics and flow noise of a pump-jet propulsor

As an underwater thruster, the pump-jet propulsor (PJP) exhibits low radiation noise but generates significant line spectral noise in the low-frequency band. In this paper, we equipped the PJP hub with two types of propeller boss cap fins (PBCF): one fixed and the other rotating with the rotor. The hybrid large eddy simulation and Reynolds-averaged Navier–Stokes method, along with the Ffowcs Williams-Hawkings (FW-H) equation, are employed to systematically analyze the hydrodynamics, exciting force, flow noise, and flow field of PJPs. The results indicate that the fixed PBCF improves the hydrodynamic performance and reduces the exiting force, raising the rotor's thrust coefficient by 9.22%–14.99%. The fixed PBCF also modifies the characteristics of line spectrum noise but causes an increase in the flow noise. The rotating PBCF increases the rotor's thrust coefficient by 2.03%–3.15%, decreasing both exciting force and line spectrum noise. For instance, at the advance coefficient of 0.8, its sound pressure level at the rotor frequency drops to 49.6%. Additionally, the rotating PBCF increases the pressure of the hub wake and effectively reduces the hub vortices' strengths. This paper provides a theoretical foundation for designing PJPs that enhance concealment and minimize vibrations and noise.

Numerical Analysis into the Improvement Performance of Ducted Propeller by using Fins: Case Studies on Types B4-70 and Ka4-70

Numerical analysis was conducted to assess the impact of fins on the B4-70 and Ka4-70 propeller performance. The study explored different fin variations, specifically bare fins, Propeller Boss Cap Fins (PBCF), and propeller nozzles, using computational fluid dynamics (CFD) simulations. To obtain the best results, the researchers utilized the explicit algebraic stress model (EASM) based on Reynolds-Averaged Navier-Stokes (RANS) equations and turbulence modelling. The primary goal of this study was to improve the energy efficiency of ships by examining various propeller configurations, both open and ducted. The overall conclusions indicated that the B4-70 PBCF convergent and Ka4-70 PBCF divergent with the addition of nozzle 19A exhibited the highest efficiency based on the EASM analysis. The CFD simulation results for both B4-70 and Ka4-70 propellers, utilizing a nozzle 19A with added boss cap fins, revealed several noteworthy phenomena. Firstly, for the B4-70 propeller, efficiency (η0) at J = 0.6 to J = 0.8 showed an increase of 1% to 2%. Secondly, concerning the Ka4-70 propeller, efficiency (η0) at J = 0.6 to J = 0.8 increased by 2% to 10%. These findings clearly demonstrate that the use of an ESD, such as the nozzle 19A with added boss cap fins, enhances the propulsion performance of the ship. It is evident that the CFD approach remains suitable and reliable for overall simulations.

Influence Evaluation of Open Propellers with Boss Cap Fins: Case Studies on Types B4-70 and Ka4-70

Numerical analysis of fins effect on propeller performance was conducted, specifically using the B4-70 and Ka4-70 propellers. The study investigated different types of fins, including bare fins and PBCF (Propeller Boss Cap Fins) using computational fluid dynamics (CFD) simulations. The explicit algebraic stress model (EASM) based on Reynolds-Averaged Navier-Stokes (RANS) equations and turbulence modeling was employed to determine the optimal results. The main objective of this research was to enhance energy efficiency in ships by examining various open propeller configurations. The CFD simulation results for open propellers B4-70 and Ka4-70, with the addition of boss cap fins, revealed interesting phenomena. When the open propellers B4-70 and Ka4-70 were equipped with PBCF, they would experience an increase in efficiency (η0). This was because the performance of the fins functioned optimally when the advance ratio (J) is high, as evident from the high velocity values. Thus, with higher velocity and lower pressure in the boss cap region at high J values, there was an elevation in thrust force due to the reduction of hub vortex. In the case of open propeller B4-70 with added PBCF, there was an increase in the efficiency value (η0) ranging from 3% to 5% when J varied from 0 to 0.7. Similarly, for propeller Ka4-70 with the addition of PBCF, there was an increase in the efficiency value (η0) ranging from 1% to 3% when J varied from 0 to 0.7. Notably, the use of an Energy-Saving Device (ESD) in the form of PBCF can increase the efficiency of ship propeller, as reported in this paper. Consequently, these findings affirmed the reliability of the overall calculations using the CFD approach.

Energy‐Saving Optimization Design of Propeller Boss Cap Fin Based on BP Neural Network Coupled with Northern Goshawk Optimization Algorithm

Facing the escalating global energy demand and environmental pressures, efforts to enhance ship efficiency and reduce carbon emissions have become pivotal strategies in addressing energy challenges. This study focuses on optimizing propeller boss cap fin (PBCF), proposing a strategy that integrates a backpropagation neural network (BPNN) with an intelligent optimization algorithm. PBCF’s positions relative to the propeller are expressed parametrically, and the sample space for PBCF parameters is constructed using Latin hypercube sampling. Building upon this, a BPNN model is established, with design parameters as inputs and hydrodynamic performance calculated by computational fluid dynamics as outputs. Simultaneously, the approximate model trained by the neural network serves as the objective function for the northern goshawk optimization algorithm, significantly enhancing the iteration speed. After determining the PBCF’s position parameters, the optimal performance airfoil is chosen as the PBCF profile from seven airfoil types. Finally, visualization techniques were employed to compare the flow field distributions of the optimized fin and the original propeller. The results demonstrate that the optimized fins effectively absorb tangential kinetic energy from blade flow, reduce hub cap pressure differences, and suppress post‐hub vortices. Under specified design conditions, the optimized fins enhance the propulsion system’s efficiency by 1.5%. This study underscores the transformative potential of intelligent optimization techniques in shaping the future of maritime engineering, providing sustainable solutions to global energy challenges.

Propulsion Performance and Hub Vortex Reduction on Various Propeller Boss Cap Fins Designs

Propulsion Performance and Hub Vortex Reduction on Various Propeller Boss Cap Fins Designs

The Evaluation of Propeller Boss Cap Fins Effects for Different Pitches and Positions in Open Water Conditions

_ The operation of marine vessels with high efficiency provides a great contribution within the scope of the International Maritime Organization and the sustainable development goals. In terms of the propulsion system, selecting the appropriate propeller is critical to effectively use the engine power installed in marine vessels because the biggest energy losses during transmission occur on the propeller and ship hull. Increasing propeller efficiencies above a certain level is quite a challenge by simply changing the number of blades, pitch, or propeller type. Therefore, various energy-saving device applications, such as propeller boss cap fins (PBCFs), are performed on the ship propeller. The effects of National Advisory Committee for Aeronautics 4415 profile PBCFs which have a different position and pitch angle integrated into the E698 model propeller have been investigated to describe efficiency, vortex, and pressure distributions based on the KRISO very large crude carrier 2 designed hull in this study. The E698 model propeller has been created by the 3D software and the validation has been performed by the computational fluid dynamic solver software based on the reference values of the propeller. The effect of four PBCF applications which have different pitches and positions on the model propeller has been revealed in terms of the efficiency, pressure distributions, and vortexes. Although P45-R45 and P45-R90 PBCF applications are quite close to the E698 propeller in terms of efficiency, no significant efficiency increase has been observed. In addition, the efficiency has decreased considerably in P90-R45 and P90-R90 applications. PBCFs application with P45-R90 has provided superiority to the base model in terms of pressure distributions and vortex formation. However, any improvement has not been achieved in the remaining three designs. Therefore, PBCF applications should be applied quite elaborately based on propeller types. Keywords PBCFs; propulsive efficiency; pressure distribution; vortex

Characteristics Investigations of Ducted Ka4-70 Series Propeller with Boss Cap Fins Using Numerical and Experimental Method

Unconventional system that are generally adopted for ship propulsion are Ducted Propellers. These devices have recently been studied with medium-fidelity computational fluid dynamics code (based on the potential flow hypothesis) with promising results. Numerical and experimental comparison of ducted propeller with PBCF, case studies with Propeller Ka4-70 used combination ducted and PBCF Divergent. The study was done numerically using computational fluid dynamics (CFD) approach. The solver is based on the Reynolds-Averaged Navier-Stokes (RANS) solutions and turbulence modelling explicit algebraic stress model (EASM). The test data was obtained from CFD simulations consisting of the open propeller and combination Nozzle plus PBCF, but the experiment was done to Nozzle and PBCF only. All measurements were carried out from J = 0 to J = 1.0 with speeds from 0 m/s to 2.445 m/s. The results of the comparative investigation cases between numerical and experiment analysis from Ka4-70 propellers with Nozzle 19A and PBCF Divergent appears that between CFD and experiments, several phenomena are seen. (i) the Ka4-70 propeller without Nozzle 19A and PBCF divergent experienced large pressure at low-speed J = 0.1 to high-speed J = 0.7, but Ka4-70 propeller with Nozzle and PBCF divergent reach highest pressure at J = 0.1 to J = 0.5; (ii) the Ka4-70 propeller without 19A nozzle and PBCF divergent increases the flow velocity at the boss cap fins but does not increase the axial induce velocity, while Ka4-70 propeller using nozzle and PBCF divergent increases the axial induce velocity of the blade, but does not increase the flow velocity of the boss cap fins; (iii) Ka4-70 propeller without Nozzle and PBCF value increase of propeller η0 to 12% when ESD added in the form of Nozzle and PBCF when J is high, from J = 0.7 to J = 1.0. ; (iv) Ka4-70 propellers with Nozzle 19A and PBCF Divergent has very similar η0 from J=0 to J=1.0. CFD approach are still appropriate to be relied upon for the overall simulation.

Numerical and Experimental Investigations into the Characteristics of Wageningen B4-70 Series of Propeller with Boss Cap Fins

Applying propeller boss cap fins (PBCF) in open B-series has been studied. PBCF is able to decrease the wake effect behind the propeller which can influence the propeller’s thrust and torque. Open propeller using PBCF is analyzed using computational fluid dynamics (CFD) which generate convergent result compared to experimental data. The solver is based on the Reynolds Averaged Navier Stokes Equation (RANSE) solutions and turbulence modeling explicit algebraic stress model (EASM). The test data was obtained from CFD simulations consisting of the open propeller and PBCF despite the experiment was done to PBCF only. All measurements were carried out from J = 0 to J = 1.0 with speeds from 0 m/s to 2.445 m/s.The results of the investigation on the B4-70 propeller with Boss cap fins convergent showed thought-provoking phenomena both on CFD and experimental work. Test results at The B4-70 Propeller without using PBCF high Pressure at J = 0.1 - 0.9, but with boss cap fins can reduce pressure at high-speed J = 0.9, so further research is needed to low-speed J = 0.1 - 0.5; Then visualization of velocity on propeller B4-70 without PBCF shows an increase in flow velocity in the boss cap fins when J = 0 to J = 0.9. The induced axial velocity in the blade propeller is the same and propeller B4-70 with PBCF decreases in speed in the boss cap fins when J = 0 to J = 0.9. However, the induce axial velocity in the blade propeller is the same. Convergent PBCF can reduce the return flow velocity in the boss cap propeller area, inversely proportional to the open propeller. Comparison of open propeller and PBCF shows that using PBCF there is an increase in the KT value at high speed of 10% to24% and a decrease in the 10KQ value on PBCF from J = 0.8 to J = 1.0 of 7% to 14%, but η_0 value at J = 0.8 to J = 1.0 increased by 3% to 8%. This Explained that the use of PBCF when the higher the value of J, greater the increase in η_0 value. Mainly, B4-70 propeller with PBCF with a converging boss cap shape with 15-degree slope exhibits increased efficiency.

Investigation of the flow patterns and mixing efficiency in a stirred tank through particle image velocimetry

BackgroundFluid mixing is a complex process that can be significantly influenced by the impeller type and its geometry. Therefore, the selection of an appropriate impeller for effective mixing is crucial. MethodsA stirred tank setup incorporating various combinations of a lab-manufactured propulsion impeller, propeller boss cap fin (PBCF), and bottom impeller was proposed and experimentally investigated using particle image velocimetry (PIV). Significant findingsThe installation of the PBCF onto the propulsion impeller led to an increase in the radial velocity component and shear rate, along with an enhancement in the flow circulation. Combining the bottom impeller with the propulsion impeller resulted in improved axial recirculation of the fluid. In all experiments involving the bottom impeller, the locations with the highest shear rate and maximum radial velocity components coincided, indicating the dominance of the radial velocity component in determining the shear rate. The mixing efficiency was found to be the highest for the propulsion impeller combined with the PBCF, followed by the propulsion impeller alone and the combination of all three impellers. The use of the bottom impeller alone yielded the lowest mixing efficiency. Additionally, the installation of the propulsion impeller improved the mixing efficiency while causing only a marginal increase in power consumption.

Improve Ship Propeller Efficiency via Optimum Design of Propeller Boss Cap Fins

This paper aims to cost-effectively improve the energy efficiency of large vessels in shipping by the optimum design of propeller boss cap fins (PBCFs). First, a model propeller of the modern four-blade propeller in a Ro-Ro ship, with no boss cap fin in its original design, is experimentally and numerically investigated. The computational fluid dynamics (CFD) model reproduced all the experiments very well. Then, the CFD model is used to conduct a comprehensive optimum design of PBCFs for the down-scaled propeller. Besides the commonly used rectangular PBCFs, nine airfoils are investigated, due to their favorable lift-to-drag ratio and great potential of being effective PBCFs. The best performing profile, among the 10 shapes, is chosen as the PBCF for further optimization. Finally, the optimum design of the PBCFs for the propeller/rudder system is achieved. It was found to yield remarkable efficiency gains for the modern propeller/rudder system under both design and off-design operation conditions, mainly due to the suppressed hub vortex and partly due to the extra thrust. The yield strength analysis confirmed that the optimum design is feasible in practice and can be used in industrial vessels. The generalized criteria for the optimum design of PBCFs also benefit other propeller/rudder systems for cost-effective energy saving.

Effect of contra-rotating propeller boss cap fins (CRPBCF) on the performance of marine propellers

Based on the enlightenment of contra-rotating propellers (CRP) and propeller boss cap fins (PBCF), a numerical study of the contra-rotating propeller boss cap fins (CRPBCF) is carried out by using the STAR-CCM + software and the large eddy simulation (LES) model. The geometric model of the auxiliary propeller is obtained by transforming the blades of the propeller VP1304. To simulate the phenomenon of vortex cavitation as accurately as possible, local mesh refinement is performed in the region, where cavitation may occur. The effects of the CRPBCF on the open water characteristics and cavitation behaviors of marine propellers are analyzed. The numerical results show that the propulsive efficiency of the propeller can be significantly improved by setting an appropriate rotation rate of the auxiliary propeller. Another advantage of the CRPBCF is that it can suppress the generation of hub vortex cavitation (HVC). In addition, the reasons for the advantages of the CRPBCF are analyzed from the pressure distribution and velocity distribution in the wake of the hub.

CFD Analysis into the Effect of using Propeller Boss Cap Fins (PBCF) on Open and Ducted Propellers, Case Study with Propeller B-Series and Kaplan-Series

The use of propeller boss cap fins (PBCF) on open B-series propeller have been known to reduce wake effect behind the propeller thus increase torque and thrust of propeller, whilst the use of Kaplan-series propeller is successful to improve the quality of flow around the propeller blades hence increase the propeller efficiency. The current work is carried out to investigate the effect of combining PBCF and ducted on B-series and Kaplan-series propellers to discover further advantages of using the two types of energy saving device (ESD) tools. The study is carried out numerically using computational fluid dynamics (CFD) approach which is based on Reynolds-averaged Navier-Stokes Equations (RANSE) together with the use of k-epsilon turbulence modelling. Overall results show that the use of Kaplan-series with combination ducted and PBCF can even further improve the thrust, torque, and efficiency of propeller.

The effect of propeller cap angle and fin size of PBCF on propeller performance

The propeller was one of the main propulsors in ships that consumed a lot of fuel due to the viscous force acting in the ship. Therefore many studies have been carried out to increase the performance of ship propellers. One of the ways is using Energy Saving Device (ESD) to improve propeller performance. One of the ESD is Propeller Boss Cap Fins (PBCF). PBCF was used to improve the propeller performance by reducing the hub vortex during propeller rotation. In this study, we compare the propeller performance before and after PBCF installation without changing propeller dimensions. The variations of PBCF fins were made in 0,1D, 0,2D, and 0,3D with a combination of the angle of the propeller cap were 15° and 20°. The propeller performance is carried out with the computational fluid dynamics (CFD) method. It was made in the open water assumption to reduce of wall effect. B-series propeller is used in the present study. The validation of propeller performance is made using empirical results. This study aimed to determine the effect of the installation of PBCF on the performance of B-Series propellers on the Ro-Ro 1000 GT ship. The results show that variation with a fin diameter of 0,2D and a propeller cap of 20° can increase propeller efficiency by 0.03%. It can be concluded the addition of PBCF can improve propeller performance.

Investigate the Influence of Phase Angle on the Performance of Propeller Boss Cap Fins Using CFD Method

Investigate the Influence of Phase Angle on the Performance of Propeller Boss Cap Fins Using CFD Method

Open Water and Performance Analysis of Marine Propeller with PBCF Based CFD Method

Improving marine propeller performance can use ESD ( Energy Saving Devices ), especially located at zone 2 area installation ESD. Focus of this research using PBCF ( Propeller Boss Cap Fins ) as ESD and marine propeller from Japanese Bulk Carrier as object. This research studies marine propeller MP687 with and without PBCF. To obtain data solver, using single domain method and multi domain method. Simulation based on Advanced Ratio ( J ) = 0.30, 0.40 and 0.50. PBCF at multi domain can improve up to ± 4.174 % for thrust, -0.769 % reduce torque value and 1.114% for efficiency increase. Using DES-SST model turbulence, PBCF can imfluence propeller MP687 flow to prevent making hub vortex from trailing edge from each propeller blade.

Improve Energy Efficiency in Shipping Via Optimum Design of Propeller Boss Cap Fins

Improve Energy Efficiency in Shipping Via Optimum Design of Propeller Boss Cap Fins

Numerical Investigation of Significance of Duct Angle of Attack and Duct Position in a Ducted Propeller in the Presence of Propeller Boss Cap Fin

Numerical Investigation of Significance of Duct Angle of Attack and Duct Position in a Ducted Propeller in the Presence of Propeller Boss Cap Fin

Comparison of different propeller boss cap fins design for improved propeller performances

The performances of different Propeller Boss Cap Fins devices, designed with the aid of a Simulation Based Design Optimization approach, are analysed and compared. A novel configuration, i.e., a PBCF inside a nozzle, is investigated in an effort to mitigate possible side effects of conventional Propeller Boss Cap Fins, such as secondary vortical structures from the fins tip, increased pressure pulses and radiated noise, without excessive worsening of the beneficial effects (increased propulsive efficiency) provided by this energy saving device. Detailed analyses reveal, instead, the destabilizing effect of the hub vortical structures on the blade tip vortex evolution, determining a substantial increase of the radiated noise of this type of propulsors.

CFD Simulation for Estimating Efficiency of PBCF Installed on a 176K Bulk Carrier under Both POW and Self-Propulsion Conditions

In this paper, the efficiency of Propeller Boss Cap Fins (PBCF) installed at the bulk carrier was estimated under both Propeller Open Water (POW) and self-propulsion conditions. For this estimation, virtual model-basin tests (resistance, POW, and self-propulsion tests) were conducted through Computational Fluid Dynamics (CFDs) simulation. In the resistance test, the total resistance and the wake distribution according to ship speed were investigated. In the POW test, changes of thrust, torque coefficient, and open water efficiency on the propeller according to PBCF installation were investigated. Finally, the International Towing Tank Conference (ITTC) 1978 method was used to predict the effect of PBCF installation on self-propulsive coefficient and brake horsepower. For analyzing incompressible viscous flow field, the Reynolds-Averaged Navier–Stokes (RANS) equation with SST k-ω turbulence model was calculated using Star-CCM+ 11.06.010-R8. All simulation results were validated by comparing the results of model tests conducted at the Korea Research Institute of Ships and Ocean Engineering (KRISO). Consequently, for the self-propulsion test with the PBCF, a 1.5% reduction of brake horsepower was estimated in the simulation and a 0.5% reduction of the brake horsepower was estimated in the experiment.