Conventional Propeller Research Articles

Hydrodynamic characteristics of bio-inspired marine propeller with various blade sections

ABSTRACT Not only economic pressures but also environmental demands and regulatory requirements bring a great interest in improving marine propeller efficiency. The design of a bio-inspired marine propeller with various blade sections is a novel field of investigation in marine hydrodynamics. The difference between the conventional propeller and bio-inspired propellers is the profile of the blade section, and the other geometric characteristics of bio-inspired propellers are the same as those of conventional propeller. In this present investigation, the geometrical features of the seagull, merganser, teal and owl wings are applied to the blade sections of marine propellers for study. The hydrodynamic characteristics, pressure distribution, tip vortex and blade strength are investigated. The numerical results indicate that the thrust and torque coefficients of the four bio-inspired propellers are almost higher than those of conventional propeller under the condition of constant advance coefficient. The bio-inspired propellers can improve the efficiency of the marine propeller. In addition, a smaller pressure difference is produced by the bio-inspired propellers in the vicinity of the leading edge, and therefore the strength of tip vortex is weakened.

Новый способ увеличения тяги воздушного винта путем применения дополнительной несущей поверхности

Air propellers used in small scale unmanned aircraft operate at low Reynolds numbers. The aerody-namic force occurring on the blade when the air propeller is in operation is of variable nature. It is observed that for Reynold numbers below 5⋅105 flow separation can occur on some sections of the propeller surface. To deal with the problem, increase the lift on the blade and therefore, reduce the turbulence boundary level, a new design called bi-blade propeller is developed and patented. This design features an additional blade above the main one. Using ANSYS Fluent, samples of the bi-blade propellers were investigated to determine the positions where the inductive resistence and the turbulence boundary level decreased, and the lift increased when the air propeller was in operation. A comparison study was conducted in laboratory conditions to investigate static thrust of the bi-blade propeller on a test bench at 2000–4500 мин–1. The bi-blade propeller was compared with a conventional propeller.

An innovative propeller with experimental and sea trial verifications

An end plate propeller (ENDP) shaped by a diffused endplate bent to the pressure side is proposed in the paper. The ENDP differs from a contracted and loaded tip (CLT) propeller, and possess remarkable performance in terms of cavitation, efficiency, vibration, and noise comparing with that of CLT and conventional propeller, particularly operating at inclined shaft condition. According to experiments conducted in the cavitation tunnel of National Taiwan Ocean University, it is observed that the diffused endplate can effectively restrain tip vortex cavitation, and eliminate tip-plate cavitation typically found on the outer surface of the tip-plate of a CLT propeller. The optimal diameter of the ENDP is smaller than that of a conventional propeller; thus, the ENDP is more suitable for ships with small stern space. Besides, the thrust of the ENDP is contributed much more from its pressure side, therefore, the cavitation on the back is reduced, and the efficiency is increased. Sea trials using a yacht with the ENDP were carried out and the results show that vibrations due to the sheet cavitation at blade-rate frequencies by the ENDP are significantly decreased in comparison with those of conventional propeller, and overall broad-band amplitude caused by the tip vortex cavitation by the ENDP at high frequencies are nearly disappeared.

Wake Analysis of an Aerodynamically Optimized Boxprop High-Speed Propeller

The Boxprop is a novel, double-bladed, tip-joined propeller for high-speed flight. The concept draws inspiration from the box wing concept and could potentially decrease tip vortex strength compared with conventional propeller blades. Early Boxprop designs experienced significant amounts of blade interference. By performing a wake analysis and quantifying the various losses of the flow, it could be seen that these Boxprop designs produced 45% more swirl than a conventional reference blade. The reason for this was the proximity of the Boxprop blade halves to each other, which prevented the Boxprop from achieving the required aerodynamic loading on the outer parts of the blade. This paper presents an aerodynamic optimization of a 6-bladed Boxprop aiming at maximizing efficiency and thrust at cruise. A geometric parametrization has been adopted which decreases interference by allowing the blade halves to be swept in opposite directions. Compared with an earlier equal-thrust Boxprop design, the optimized design features a 7% percentage point increase in propeller efficiency and a lower amount of swirl and entropy generation. A vortex-like structure has also appeared downstream of the optimized Boxprop, but with two key differences relative to conventional propellers. (1) Its formation differs from a traditional tip vortex and (2) it is 46% weaker than the tip vortex of an optimized 12-bladed conventional propeller.

Numerical and experimental investigation of the fluid flow on a full-scale pump jet thruster

In the present study, a post-swirl pump jet system was designed for an axisymmetric underwater vehicle. In order to evaluate the design procedure, several experiments such as bollard pull, self-propulsion point (SPP) and bare hull resistance tests were conducted in a towing tank on a full-scale model. Further conditions were performed numerically at higher velocities to determine the characteristic chart and flow pattern analysis. Both open-water and behind-hull conditions were simulated. The Realizable k-ε turbulence model and the Mixing-Plane Method (MPM) were utilized in a periodic domain for numerical simulations. The obtained results showed that the variations of hydrodynamic coefficients, especially the torque coefficient, against advance coefficient were much smaller than conventional propellers. Moreover, the net imbalance roll moment was quite small in all conditions suggestive of accurate stator design. The stator also created additional thrust and hence increased the overall performance up to 82 percent in the behind-hull condition.

Energy saving performance analysis of contra-rotating azimuth propulsor. Part 2: Optimal matching investigation in model scale

The propulsive efficiency maximization of contra-rotating azimuth propulsor (CRAP) at model scale is investigated through searching the optimal matching rotational speeds of the forward propeller (FP) and rear propeller (RP) of CRAP based on the potential-based panel method. The hydrodynamic performance of CRAP with changing rotational speeds (FP and RP may have different rotational speeds) are calculated. When the inflow velocity is certain, the cubic spline interpolation method is used to get the equal thrust points at which CRAP has the same thrust with the corresponding conventional propeller (CP). Then, the delivered powers at these equal thrust points are further obtained through cubic spline interpolation method. The rotational speeds of FP and RP at the equal thrust point corresponding to the minimal delivered power are the optimal matching rotational speeds of CRAP. The optimal matching calculations are carried out at different inflow velocities. The results of the optimal matching investigation show that CRAP has the lowest delivered powers when FP and RP have the optimal matching rotational speeds and that the energy saving level decreases with the increase of inflow velocity. The optimal matching rotational speed ratio decreases with the increase of inflow velocity. In general, the delivered powers of CRAP having optimal matching rotational speeds at different inflow velocities are obviously smaller than those of CP.

Effect of various winglets on the performance of marine propeller

The tip vortex cavitation (TVC) is an issue of increasing interest, because the TVC plays an important role in propeller radiated noise and cavitation erosion. The marine propeller with winglets, which is inspired by the winglets of airfoil, is numerically investigated in the present paper. The blade tip of newly designed propeller tilts toward the pressure side. The difference between six propellers is the change of the rake angle at r/R = 1.0. The pressure coefficient, TVC, axial velocity field and helicity are analyzed. The numerical results show that the winglets of newly designed propeller scarcely affect the efficiency of propeller. The thrust coefficient gradually decreases with the increase in rake angle. As for the suction side, the pressure coefficient (Cp) of winglets propellers is higher than the conventional propeller in general. In addition, the winglets are beneficial to generate less cavitation behavior when the rake angle is small. However, as the rake angle is further increased, the cavitation behavior of winglets propeller is also increased, even larger than the conventional propeller. Therefore, it can be deduced that the winglets can be used to effectively improve the TVC characteristics to some extent.

Hydropod: An Onboard Deployed Acoustic–Visual Device for Propeller Cavitation and Noise Investigations

Conducting noise trials with big merchant vessels could constitute serious economic and time losses for the ship operators. This study aims to introduce an experimental acoustic–visual device enabling economical and cost-effective noise trials in full scale. Noise emission and dynamics of propeller cavitation are investigated on a research vessel equipped with a customized submerged device called “Hydropod” that consists of hydrophones and a high definition, wide-angle underwater camera. Previously conducted noise trials following the international standards with an off-board hydrophone array are utilized for the validation of the adopted approach. The comparisons between the Hydropod measurements and conventional noise trial measurement results have shown promising correlations, except for a self-noise hump present in the noise spectra of the Hydropod measurements. Furthermore, by taking advantage of the replacement of the conventional propellers of the catamaran with a set of new profile technology (NPT) propellers, additional trials were conducted using the Hydropod. This enabled interpretation of the relative performance of both sets of propellers in terms of acoustics and cavitation extent. The NPT propellers were superior compared to the conventional propellers over the cavitation extent and resulting acoustic emissions.

Wingtip-Mounted Propellers: Aerodynamic Analysis of Interaction Effects and Comparison with Conventional Layout

Wingtip-mounted propellers installed in a tractor configuration can decrease the wing induced drag by attenuating the wingtip vortex by the propeller slipstream. This paper presents an aerodynamic analysis of the propeller–wing interaction effects for the wingtip-mounted propeller configuration, including a comparison with a conventional configuration with the propeller mounted on the inboard part of the wing. Measurements were taken in a low-speed wind tunnel at Delft University of Technology, with two wing models and a low-speed propeller. Particle-image-velocimetry measurements downstream of a symmetric wing with integrated flap highlighted the swirl reductions characteristic of the wingtip-mounted propeller due to wingtip-vortex attenuation and swirl recovery. External-balance and surface-pressure measurements confirmed that this led to an induced-drag reduction with inboard-up propeller rotation. In a direct comparison with a conventional propeller–wing layout, the wingtip-mounted configuration showed a drag reduction of around 15% at a lift coefficient of 0.5 and a thrust coefficient of 0.12. This aerodynamic benefit increased upon increasing the wing lift coefficient and propeller thrust setting. An analysis of the wing performance showed that the aerodynamic benefit of the wingtip-mounted propeller was due to an increase of the wing’s effective span-efficiency parameter.

Numerical study on variation characteristics of the unsteady bearing forces of a propeller with an external transverse excitation

The unsteady bearing forces of a propeller can be significantly affected by external transverse excitations. This paper numerically studies the unsteady variation characteristics of the bearing forces of a three-blade conventional propeller with external transverse excitations or without excitations. The dynamic mesh method combined with the RANS turbulence model is employed. The numerical simulation shows the frequency response in the frequency domain of KT, KQ under external transverse excitations. The frequency of the response is found always equal to twice of the excitation frequency. If the amplitude of the external transverse excitation keeps constant, the amplitude of the response increases with the increase of the excitation frequency. If the excitation frequency keeps constant, the amplitude of the response increases with the increase of the excitation amplitude, in a power-law relationship. The pressure distribution can be significantly affected by the external transverse excitation, leading to a high irregularity of the flow field.

Prediction of Noise and Acoustical Spectrum of Counter-Rotating Propellers

The acoustical performance of a counter-rotating marine propeller system is computed using the Ffowcs, Williams and Hawkings (FWH) algorithm. The solution procedures, where finite volume computational fluid dynamics calculations were exploited, was validated with a conventional propeller having experimental results (namely David Taylor Model Basin [DTMB] 4119). The large eddy simulation formulation and the sliding mesh technique are employed to build thrust and torque curves. Mesh dependency, turbulence model, and discretization schemes were all assessed to have repeatable and accurate results. Because the application under consideration involved inhomogeneous flow and blade interactions, DTMB 3684 and 3685 counterrotating propeller (CRP) models were used for comparisons. In terms of validation of numerical acoustics, the acoustical model evaluation study was first performed on a flow over a cylinder and a rain gutter model. The FWH approach produced good results for the spectrum at near-field and far-field locations. The performance of an inclined propeller, namely VP1304, in a noncavitating condition was investigated and the results were compared with the experiments conducted at the Potsdam Model Basin. Pressure pulses of this propeller in the cavitation tunnel were also attained and compared with experimental results. The amplitudes of the pressure fluctuations were in good agreement with the experimental data except for the weak third harmonics. Last, the generic form of the CRP system attached to an underwater vehicle body was considered to investigate the acoustic spectrum in terms of blade passing frequencies, interacted harmonics and radiated noise. 1. Introduction Propellers are used to drive marine systems including underwater vehicles. To boost their performance and fuel efficiency, they were designed mainly by experimentations. Recent studies (Denny 1968; Liu & Hong 2011), however, show that useful information about the characteristics of different conventional propellers can be extracted with the computational fluid dynamics (CFD) methodology which generally produces results supporting the experimental findings. As, for example, Subhas et al. (2012) succeeded to reproduce the blade characteristics of the INSEAN E779a propeller-designed and manufactured by Marine Technology Research Institute in the field of naval architecture and marine engineering in Italy-using the CFD. Similar finite volume calculations (Güngör & Özdemir 2015b) of the performance of propeller P4382 agreed well with the available experimental data. Embedding a model (Xia et al. 2012) for cavitation occurring on blade surfaces has been shown to improve the numerical performance in comparison with the calculations that neglect the cavitation effects. In the present analyses, we take into account the single-phase nature of the flow, and the cavitation effects are neglected with the emphasis placed in the noncavitating regions where reliable test results are available. Thus, to produce meaningful results, propeller hydrodynamics needs be considered especially under inhomogeneous flow conditions. Experiments (Potsdam Experimental Team 2015) on propellers subjected to the inhomogeneous flow reveal a variable wake in front of the propeller, which can be conveniently modeled numerically although unsteady interactions make the convergence difficult. On the other hand, the counter-rotating propeller (CRP) tests might be necessary to understand the interactions between the blades and hubs. To observe the axial distance effect, the CRP tests were handled in a cavitation tunnel (Hecker & McDonald 1960) where thrust and torque comparison assists in validations of numerical computing for each propeller's performance.

Water vortex hydropower technology: a state-of-the-art review of developmental trends

With the explosive growth of global energy demand coupled with effects of climate change, there is a significant shift towards green energy generation in recent years. Of the various renewable energy resources available, micro-hydro-power and pico-hydro-power remain very popular in both developed and developing countries. Since 2006, significant growth has spurted in the use of artificial free-surface vortices to generate low and ultra-low-head hydropower following the development of the so-called gravitational water vortex hydropower plant. The technology works on the principle of harnessing hydroelectric power from the high angular velocity experienced in the core of a whirlpool generated in a vortex chamber. In this article, a state-of-the-art review is undertaken on the vortex hydropower technology including a historical review of the technology, the underlying hydraulic principles of such devices, overview of research and technologies that have been deployed to date together with an evaluation of their performance and key findings. Currently, there are 19–22 known live vortex hydropower technologies operating internationally with key academic and commercial research activity in Europe and Asia. The average efficiency from these sites was found to be in the region of 53% which is lower than conventional propeller turbines but higher than waterwheel systems. It was found that the vortex plant, due to its ability to sustain relatively high efficiencies at low heads and small to medium flow rates, addresses a gap in the current turbine application chart. Its key advantage lies in the high-power densities produced compared with conventional technologies. The system also demonstrates potential to be able to function as a fish passage; however, stronger validation is required to prove this for a range of turbine systems. Finally, the authors propose a number of areas that should be investigated that should provide immediate improvements to the turbine in terms of performance.

Waterjet Modeling to Calculate High Speed Vessels’ Performance

Similar to the matching process between the main engine and propeller in a conventional vessel, there is a basic necessity to match main engine and waterjet in a high speed craft. Unlike the ability of the naval architect to review the overall impact of the engine and propeller selection in terms of thrust, delivered power, fuel consumption and vessel range, when coming to match a waterjet to a particular vessel, the performance data presented by the waterjet manufacturers is in some ways simplistic and does not contribute to the naval architect's effort to assess the complete performance picture of the propulsion system. In this article, a simple parametric modeling of the waterjet is presented which is common to all waterjets and enables the naval architect to match and assess the interaction between main engine and waterjet much like the process when matching main engine to a propeller. It will be shown that the constant power lines for thrust and rotational speed of a waterjet can in fact be consolidated into a single nondimensional set of curves similar to the nondimensional KT/KQ/ηo of a conventional propeller. This process will allow in fact the overall assessment of the matching problem between the main engine and the waterjet. Some waterjet manufacturers provide data for different impeller designs in which case this process can provide the naval architect a tool to choose the optimal impeller. Unlike the graphical nature of the performance assessment of the conventional data presented by the waterjet manufacturers, this method of modeling allows the digital/analytical solution in any intermediate speed and power setting. For the sake of simplicity, this article does not deal with the cavitation phenomena and the loss of thrust when the waterjet is cavitating although these are important issues that should be considered when assessing waterjet performance.

Numerical Investigation of a Marine Propeller Blade for Material Effect and Stress Behaviour

The process of designing a marine propeller for under water applications involves various complex analyses. Analysis is of iterative in nature which makes it cumbersome and inefficient to understand. A part of the research work entitled in this paper is concerned with the material effect and stress behavioural characteristics of a marine propeller blade subjected to cantilever condition. Designing and analysing the behaviour of an anisotropic composite material is one of the most important technologies in the area of marine propulsion. Based on FEM the conventional and composite material marine propeller blades are analysed. To simulate the blade layup and to determine the stress characteristics, ANSYS software with shell 181 elements is taken for reference. A study has also been carried out for determining the stress and deformation pattern arising due to varying ply layup and material. The obtained numerical results are then compared and summarised in. Computational efficiency and integrity of the presently adapted method in this work are determined by several case studies.

Numerical design of contra-rotating azimuth propulsor using vortex theory coupled with panel method

A design procedure of contra-rotating azimuth propulsor (CRAP) is developed based on vortex theory coupled with low order potential-based panel method. The forward propeller (FP) and rear propeller (RP) are designed using the written computer code with the pod unit (PU) which includes the pod body and the strut being given first. The hydrodynamic interactions among FP, RP and PU are considered through induced velocities which are calculated using panel method. A conventional propeller (CP) supplying the same thrust with CRAP at the same inflow velocity is designed to analyze the energy saving performance of CRAP. The case study shows that, at design condition, CRAP has a decrease in delivered power by approximately 8% compared with CP. The tangential induced velocities in the slipstream indicate that CRAP recovers the rotational energy of slipstream effectively. The open water characteristics of CRAP are also analyzed systematically.

Energy saving performance analysis of contra-rotating azimuth propulsor

The energy saving performance of contra-rotating azimuth propulsor (CRAP) is investigated based on low order potential-based panel method. The hydrodynamic interactions among the forward propeller (FP), rear propeller (RP) and the pod unit (PU) which includes the pod body and the strut are considered through induced velocities which are obtained by panel method. In order to have a better understanding about the energy saving performance of CRAP, the hydrodynamic performance of a conventional propeller (CP) supplying the same thrust with CRAP at design condition is also calculated. At design condition, CRAP has a decrease in delivered power by approximately 8% comparing with CP, and the tangential induced velocities in slipstream show that CRAP recovers the rotational energy of slipstream effectively. At off-design conditions, the rotational speed of CRAP is adjusted to supply the same thrust with CP. In general, the delivered power of CRAP is significantly smaller than that of CP, and the energy saving performance of CRAP increases with the decrease of inflow velocity.

Technical Analysis of Kort Nozzle Application for SPOB Ship 4990 DWT on River

Propeller is a locomotor shaped vanes are used to drive ships, and also propellers which serves to move tehaga by changing the turning force of the propeller thrust menggerakakan into the vessel. In increasing the value of the thrust to be generated that is by applying the kort nozzle propeller. The method used in this study using CFD (Computional Fluid Dynamic), and the variation is from the conventional propeller models, with a kort nozzle propeller type kort nozzle type 19A and 37. Based on the findings that the kort nozzle propeller with the addition of the value of the thrust , propeller efficiency and torque generated. The driving force value is by using kort nozzle propeller type 37 amounted to 349.27 kN.

Review on Numerical and Experimental Research on Conventional and Unconventional Propeller Blade Design

This paper reviews the research conducted on propeller blades based on the performance evaluation method and available design. The review includes the propeller blades used for aircrafts, unmanned aerial vehicles, marine vehicles and wind turbines, as the working principle remain the same, differing only in operating conditions. Both experimental and numerical methods were discussed to provide a reliable procedure to investigate the performance of propeller blades. In addition, the propeller blades design was discussed, including conventional and unconventional blade designs. Blade shape, chord length and twist angle are the basic parameters for optimization method on conventional design. Optimization managed to improve propeller performance at an impressive rate. Many designs are currently being developed allowing more possibilities for blade design advancement.

제원 및 날개 끝 형상 변화에 따른 비대칭 전류고정날개 성능연구

This paper reports a numerical method for determining the resistance and self-propulsion performance of an asymmetric pre-swirl stator used as an energy saving device by cancelling a propeller's rotational energy. The present asymmetric pre-swirl stator propulsion system consists of three blades at the port and one blade at the starboard, which can effectively recover the biased rotating flow. This paper provides the design concept for the present asymmetric stator, which produces more efficient results than a conventional propeller.

Hyperecho PROPELLER-MRI: Application to rapid high-resolution motion-insensitiveT2-weighted black-blood imaging of the carotid arterial vessel wall and plaque

To demonstrate the usefulness of hyperecho and PROPELLER (HEP) for carotid arterial vessel wall imaging by using a quantitative comparison with conventional methods. PROPELLER is a motion-insensitive turbo spin-echo (TSE) sequence and has recently been utilized in magnetic resonance (MR) plaque imaging instead of double inversion recovery TSE (DIR-TSE). Wider blade-width, higher k-space density, and an improved blood suppression effect result in better image quality. In this study we introduce a new combination of HEP. A total of 17 subjects were examined on a 3.0T system. We conducted quantitative comparisons for signal-to-noise ratio (SNR), contrast-to-noise-ratio, and image sharpness among HEP, DIR-TSE, and conventional PROPELLER (c-PROPELLER). Subsequently, images obtained with DIR-TSE, c-PROPELLER, and HEP were visually evaluated using a three-point scale by two board-certified radiologists. HEP showed high SNR similar to c-PROPELLER, good T2 contrast approximating DIR-TSE, and better blood suppression compared with the other two methods (P < 0.05). The image sharpness of HEP (2.55 ± 0.53) was higher than that of DIR-TSE (1.89 ± 0.33) and the absence of ghost or streak artifacts in HEP (2.89 ± 0.33) was better than that in both other methods (2.22 ± 0.83 for DIR-TSE and 2.00 ± 0.50 for c-PROPELLER) (P < 0.05). Furthermore, the degree of blood suppression, particularly in cases of slow or turbulent flow close to the atherosclerotic plaque, was identical for HEP (2.80 ± 0.45) and DIR-TSE (2.80 ± 0.45) but was significantly better than for c-PROPELLER (1.60 ± 0.55) (P < 0.05). This study demonstrates the usefulness of HEP in the carotid arteries. HEP can provide higher-resolution T2 -weighted black-blood imaging without flow- and/or motion-related artifacts, compared to conventional techniques. 3 J. Magn. Reson. Imaging 2017;45:515-524.