Ship Propeller Research Articles

Temporal development of unconfined propeller scour in waterways

A ship propeller jet causes bed scouring and deposition of sediments around the scoured area. Although the bed topography changes induced by the ship propeller are one of the main issues in a harbor, these effects are relevant in other contexts concerning the ship maneuvering zone. An unexplored problem is the scour induced by the propeller jet in waterways. In this case, the still water condition, commonly accepted in several research studies, is not justifiable owing to the effect of an additional flow to the propeller jet, which can induce alterations in the scouring process. Thus, in this paper, an experimental campaign on the combined effects of a propeller jet and a uniform flow on a mobile bed is presented. Specifically, different propeller submergence depths and water discharges were tested. Numerical simulations were performed to highlight the different behaviors observed in the experimental runs with and without a uniform flow in addition to the propeller swirling jet. Furthermore, the presence of the channel flow was investigated in terms of scoured longitudinal and transverse bed profiles, as well as of the entire scour hole bathymetry. A regression equation was obtained to compute the maximum scour depths and the scoured volume for the investigated conditions. Finally, a spectral analysis method is proposed to characterize the complex bed bathymetry induced by the propeller jet and the uniform flow.

Stability Improvement of Electric Ship Propulsion System Using Supercapacitor

Owing to the serious greenhouse gas emissions and inflexible control of traditional ship propulsion system, the electric ship propulsion system has been widely introduced into the ship’s power system. However, the variations of ship propellers will lead to the instability of electric propulsion system so this paper studied the transient characteristics of electric ship propulsion system by performing a series of experiments on a real electric ship propulsion system platform. Based on the experimental results, a detailed model of supercapacitor energy storage system (SCESS) is proposed to improve the voltage and frequency response for the electric ship propulsion system. To enhance the stability and reliability, a double closed-loop control method combined with Pulse-Width Modulation algorithm (PWM) is utilized to control the energy storage system for smoothing the power fluctuations caused by the electric propulsion system. The simulation results demonstrate the high efficiency of supercapacitor to improve the transient stability of the whole power system of the ship.

Прогнозирование объема каверн на вращающихся лопастях и масштабные эффекты

Object and purpose of research. Pressure pulsations induced by cavitating blades substantially contribute to flowinduced loads and amplify structural vibration. These pulsations depend on oscillation of the volume of cavities over blades. Prediction of them usually involves model tests and there are three kinds of scale effects influencing the cavity volumes. The first one is associated with the non-uniform inflows. The second one is associated with the combined influence of the blade boundary layer and surface tension on the cavity surface. The third one is associated with the cavity buoyancy. Materials and methods. Because of complexity of blade flows, a qualitative analysis of similar unsteady non-uniform flows around 3D hydrofoils is useful. This paper presents such an analysis for a hydrofoil with the sections copied from a marine propeller blade. The inflows correspond to the wakes of a ship and of her model. Computations carried out using an analysis of viscous-inviscid interaction. Main results. The qualitative explanation of observed trends and scale effects is obtained due to this analysis. In particular, the role of pressure side cavitation in full scale conditions is pointed out. Conclusion. The difference of model and ship wakes results in the substantial difference in blade section angles of attack at the same blade loading. Therefore, in model tests the suction side cavitation is more extensive, whereas the pressure side cavitation may not appear, though it exists on full-scale ship propeller blade. This substantial scale effect has been usually out of previous considerations.

Microstructure, mechanical properties, and brittle fracture of a cast nickel-aluminum-bronze (NAB) UNS C95800

Nickel aluminum bronzes (NAB) are corrosion resistant alloys used in seawater environments as parts of valves, fittings, ship propellers, pumps, pump shafts, and heat exchangers. As many other alloys, NAB can be cast or wrought. More recently, additive manufacture methods have been studied for this class of materials. Corrosion problems are reported in the literature, and are related to the presence of β phase, de-alloying and low aluminum content. In this work, the mechanical behaviour of a cast NAB alloy was investigated by tensile and impact tests. The material has been heat treated to eliminate the deleterious β′ phase. Brittle fractures were observed in the tensile and Charpy impact tests, and the micro-mechanisms of these fractures were investigated by fractography in the scanning electron microscope (SEM). The true stress–strain curve of the tensile test was successfully modelled by Hollomon’s and Ludwik’s equations. The results are useful to the application of cast NAB UNS C95800 alloy.

New Results of the Heat-Treated CuZn39Pb3 Brass Behavior and Resistance to Cavitation Erosion

The paper presents the results of the behavior and resistance to the erosion by vibrating cavitation of the CuZn39Pb3 brass, obtained by quenching the volume heat treatment from 800°C with water cooling, followed by the stress-relief to 250°C, with air cooling. Comparison with both the delivery status and the naval brass (used for ship propellers), based on the characteristic parameters values, recommended by the ASTM G32 standards and used in the Cavitation Laboratory of the Polytechnic University of Timisoara, shows that the hardness increase resulted from the heat treatment led to a significant increase of resistance to vibrating cavitation.

Practical numerical method for erosion risk prediction on ship propellers

It is important to make predictions of cavitation-induced erosion risk on ship propellers in the design phase. Since a cavitation tunnel test on a propeller model coated by soft paint, that is, a standard experimental method for evaluating erosion risk, is costly and time-consuming, numerical methods are necessary for erosion risk predictions. DES is made for cavitating flows around the propeller with a numerically modelled hull wake at the inflow. After achieving a converged solution, an erosion risk index is computed in each cell connecting to the blade surface and accumulated over a propeller rotation. Cavitation simulations are made for two propellers designed for a single-screw ship, of which one showed an erosion indication and the other showed no indication after cavitation tunnel tests with soft paint coating. Three index formulations are compared with the experiment result. The high value region of Index 1 based on the potential energy density of collapsing bubbles corresponds better with the eroded spot indicated by partial and complete paint removals in the experiment than those of the other indices. The maximum value of Index 1 for the non-eroded propeller is lower by more than an order of magnitude than that for the eroded one, whereas the maximum values of the other indices are of the same order of magnitude for both propellers. The validation of Index 1 is in agreement with the criterion that the maximum index needs to be below 1,000 J/m3 for erosion-free propeller designs. The design evolution based on the erosion risk index and propulsive efficiency from CFD shows that it can be a practical tool for a quantitative evaluation of blade surface erosion risk in the propeller design phase.

РАЗРАБОТКА БЛОКА ОБРАБОТКИ ИНФОРМАЦИИ ДЛЯ ПРОГРАММНО-АППАРАТНОГО КОМПЛЕКСА СИСТЕМЫ МОНИТОРИНГА КРУТИЛЬНЫХ КОЛЕБАНИЙ СУДОВОГО ВАЛОПРОВОДА

The article considers torsional vibrations in combination with other technical factors, which remain a cause of damages and breakdowns of the ship's propeller shafts, intermediate shafts and crankshafts. Torsional vibrations inevitably occur in the ship plants. It can be explained by the uneven torque of the engine and the torque on the propeller (exposure of the propeller, uneven movement of the water flow, stormy weather, etc.), which leads to alternating twisting of the shaft. To reduce torsional vibrations, dampers are used, which require periodic performance testing by using the torsiography procedure. In contrast to the existing monitoring systems of the technical condition of the damper, it is planned to install an information processing unit for the software and hardware complex for monitoring torsional vibrations of the ship's shaft line and the parameters associated with them (vibration and temperature changes of the flexible elements of the connecting couplings). The unit under development will allow to constantly monitor the level of torsional vibrations and, if they increase, to signal the ship's mechanic to switch to another operational mode of the main engine, which will increase the reliability and automation of the ship power plants, the safety of navigation, and reduce the economic costs of ship operating

A Comparative Assessment on Cavitation Erosion Behavior of Typical Copper Alloys Used for Ship Propeller

A Comparative Assessment on Cavitation Erosion Behavior of Typical Copper Alloys Used for Ship Propeller

Investigation of the shape of the torpedo nose in supercavitation and numerical analysis of the effect of gas injection

Extensive studies on cavitation have been conducted for years as an undesirable phenomenon in marine engineering. The cavitation phenomenon causes severe damage to the body of torpedoes, ship's propellers, pump impellers and turbines. It also increases the frictional drag of submarine vessels and imposes many limitations on their design and construction. With increasing speed in submarines and increasing of the cavitation, supercavitation occurs which can be used to create a large bubble around the vessel. Because of drag in the water is mostly due to the friction of the body, by the supercavitation, the contact of water with the torpedo is reduced and as a result the friction drag is greatly reduced and the torpedo speed will increase significantly. In this regard, by artificially injecting air into the body in the state of cavitation, the process of creating supercavitation and reaching this stage can be accelerated.In this study, in order to investigate the effect of torpedo nose shape on supercavitation, different types of torpedo bodies have been modeled and studied different nose shapes. After modeling, meshing is performed with ANSYS Fluent software and the analysis of the model in cavitation numbers (0.2, 0.3 and 0.4) will be examined. Finally, the model will be analyzed in air injection mode (artificial supercavitation) with ANSYS CFX software and the results will be presented.

A Novel Shear Plate for Direct Measurements of Bottom Shear Stress Induced by a Model Ship Propeller

A Novel Shear Plate for Direct Measurements of Bottom Shear Stress Induced by a Model Ship Propeller

Numerical investigation of the ship propeller load under reversed propulsion condition

Stopping maneuver is an important research topic in ship maneuverability. The stopping ability of ship is not only related to the hydrodynamic characteristics of hull, rudder and propeller, but also related to the capacity of main engine. However, there are few researches on the capacity of main engine under reversed propulsion condition. In the paper, a numerical water tank is established to simulate the propeller loads using the computational fluid dynamics (CFD) software STAR CCM+. The numerical model is firstly validated by experimental data, and then is used to investigate the propeller loads on a full-scale model with different ship speed and propeller speed. By dimensionless, the relations between the advance coefficient and the load coefficients are shown as J - KT curves and J - KQ curves. Furtherly, the flow structures near the propeller and the pressure on the propeller with different J values are investigated. The simulations reveal that the flow velocities induced by the reversed propulsion of the propeller is similar to the wake flow by ship with J = -0.49. That is the reason for the minimum points of J - KT and J - KQ curve occurring in cases with J = -0.49. Subsequently, the capacity of the main engine and the output load of the propeller are considered comprehensively. The relations between the ship speeds and the maximum output loads on the propeller are discussed in details.

Introduction and Background - About Water: Novel Water Technologies in the New Millennium

A year ago, May 24, 2019 was the 500th anniversary of the death of Leonardo da Vinci. Visionary water projects on a grand scale were one of his lifelong passions. They were never fulfilled. Substantia offers this volume on new water technologies that work, in celebration of the life of da Vinci, the artist and genius of Florence.
 These technologies are simple and cheap. They embrace desalination, sterilization of wastewater, including killing of viruses, selective heavy metal ion removal and harvesting.
 And a simple solution to a major world economic problem. that of cavitation in ship propellers.
 Our claims are startling and apply to real world conditions, that is, in concentrated and complex environments. They are not restricted to ideal, dilute solutions. They are presently inexplicable within the confines and boundaries of classical physical and colloid chemistry. It has been increasingly apparent that this venerable enabling discipline that underpins chemical engineering and biology suffers from sins of omission and commission. Once those strictures are removed whole new opportunities open up. Examples of these we want to exhibit here.

Effect of the cross-flow wake on the hydrodynamic performance of the HSP propeller by the CFD solver

This paper numerically presented the effect of the cross-flow wake on the hydrodynamic performance of the ship propeller. The propeller is a typical high skewed propeller (HSP) of the training ship ‘Seiun-Maru’, whose experimental data have been frequently used by many researchers. The viscous flow is solved by an incompressible Reynolds Averaged Navier–Stokes (RANS) method using Ansys-CFX solver. The shear stress transport (SST) k–ω turbulence model is employed for the simulation of the propeller in a fully turbulent flow. The thrust and torque coefficients at 10 presented advance coefficients (between 0.1 and 1) showed good agreement comparing with experimental data. The numerical results are increased in the wake flows. The unsteady oscillating load of thrust and torque is presented and discussed for one blade and whole blades during one cycle at different cross-flow wakes and at advance coefficient (J = 0.85). Based on the numerical results, when the cross-flow wake is increased by 20% and 50%, the thrust at J = 0.85 are increased about 2.03% and 4.71% respectively and the torque at J = 0.85 is increased about 1.04% and 2.69%, respectively. Moreover, pressure distribution and streamlines are also presented and discussed.

Numerical modelling of freestream cavitating flow through ship propeller using OpenFOAM

In marine industry, cavitation has been a massive problem when dealing with ship propeller. One of the main effects caused by cavitation is thrust breakdown, which decreases the efficiency of propeller. It is difficult to completely avoid this phenomenon, but there are ways to reduce its occurrence. It is important to study the phenomenon in the process of designing propeller. For that reason, cavitation prediction on certain geometry is compulsory to give out the optimal ship propeller design. In this paper, the cavitation analysis on propeller VP1304 was conducted numerically utilizing OpenFOAM code. The motion of the propeller was represented by Arbitrary Mesh Interface (AMI) methodology with the aid of RANS turbulence models. The authors examined the differences between k-ε model and k-ω SST model in this case with the involvement of Schnerr-Saur, Merkle and Kunz cavitation model. The results achieved shows that the k-ω SST model performed more accurately in term of propeller thrust, torque and efficiency prediction. Furthermore, among the three employed cavitation models, Schnerr-Saur agrees best with empirical data, and hence, can be considered most suited for this analysis.

The capacity analysis of dynamic positioning for semi-submersible vessel

In this paper, the Dynamic Position model (DP) of semi-submersible vessel was established in Ariane system based on static analysis and standards, to obtain DP capability polar plot under different failure pattern. Through the time-domain simulation, PID control theory and Kalman filtering method were used in DP accuracy analysis. Analysis results, such as ship motion, DP accuracy and propeller variation, could be provided for safety and reliability check in engineering practice.

Failure criticality evaluation of ship propeller shaft system based on Fuzzy FMECA method

The propeller shaft system is the key system for power transmission on board. The components of the system are complex, the working environment is bad, the failure modes are numerous, and the failure consequences are serious. FMECA (Failure Modes, Effects and Criticality Analysis) is difficult to accurately and quantitatively carry out criticality assessment. Therefore, in view of the complex navigation environment, the fuzzy FMECA method is used to evaluate the failure mode criticality of propeller shaft system. On the basis of FMECA, the factor set with maintainability and testability is established, and the factor level set, fuzzy evaluation matrix and factor weight set are determined, and the consistency judgment is made. Finally, the fuzzy comprehensive evaluation is carried out to obtain the accurate and quantifiable failure mode criticality ranking. Compared with the traditional FMECA method, fuzzy FMECA can consider the limited maintenance conditions and test conditions on board, accurately quantify the criticality degree, and take into account more expert opinions, so as to improve the authenticity, accuracy and repeatability of criticality assessment. Therefore, the fuzzy FMECA method can better evaluate the criticality degree of propeller shaft system, and the results can effectively guide the improvement of propeller shaft design and maintenance work.

Оценка диаметра струй воды, воздействующих на поверхность лопастей гребных винтов при кавитационном изнашивании

The article analyses the structure of cavitated areas of the ship propeller blades made from aluminum bronzes with different composition. The most informative zones of cavitation wear are the cold-hardening zone and the peripheral one that help estimate the mechanical parameters causing the cavities to collapse. The dents formed on the metal surface in the process of hydrodynamic cavitation wear have spherical parts on their bottoms, in which it is possible to inscribe a circle of a definite diameter. There were conducted the experiments on forcing the ball indentors into the surface of different metal alloys. The first run of the experiments includes forcing of a steel ball with a diameter of 1.588 mm into the surface of 33 alloys with different hardness under the loads of 1 470, 980 and 588 N. The impression diameters were measured using Brinell magnifying glass. There has been found the power dependence between deformation of dents on the metals tested under hydrodynamic cavitation and hardness of the materials, which is similar to the dependence of deformation after forcing the ball indentors into the alloys of different hardness. The second run of the experiments included modeling the cold-hardening zone of the cavitation wear area by repeated forcing the ball indentors with the diameters of 1.588, 2.5, 3.175 and 5.0 mm into the bronze BrAZhNMts9-4-4-1 plates with area of 100 × 50 × 20 mm. Forcing was made into the side 100 × 50 mm previously ground and polished. The equal strain rate in impressions of different diameters was observed during forcing. A direct proportional relationship was obtained between the arithmetic mean deviation of the surface profile and the indenter diameter. The arithmetical mean deviation of the assessed profile of the side plotted against the ball indentor yields a direct proportional relationship. Using the dependence for the case of cavitation attack on the propeller blades helps to infer that the diameter of water jets striking against the propeller blade surface with diameter of 3 700 mm makes about 10 mm. The obtained value allows to choose reasonably the experimental equipment and the parameters of testing the ship propeller materials for cavitation wear.

Numerical Study of B-Screw Ship Propeller Performance: Effect of Tubercle Leading Edge

Various attempts to modify the ship's propeller have been made to improve performance as a propulsion component. This paper analyzes the effect of modification of the B-Series propeller by adopting a whale fin shape (Humpback Whale). Also, it analyzes the flow in the propeller before (standard) and after modification. Modifications are made to the leading edge, which is called the tubercle leading edge (TLE). It adds and subtracts sections with a wavelength of 0.2R and amplitude of 2.5% of the chord section length in the propeller leading edge. The numerical study is used using CFD on different J values (0.2, 0.4, and 0.6). It was found that the modification of TLE has a less significant effect on performance. Instead, it decreased at a low J value (0.2). Meanwhile, the largest decrease was at a high J value (0.6), namely up to 10.4% for thrust, 4.3% for torque, and 6.4% for efficiency. Whereas at J=0.4, the torque increases only 0.4%, and the torque and thrust decrease, although less significant. The flow analysis indicates that the shape of the TLE provides a decrease in pressure. However, on the positive side, this modification provides a reduction in noise on the propeller surface.

Friction-induced vibration and noise behaviors of a composite material modified by graphene nano-sheets

Due to the weak hydrodynamic lubrication effect under low speed and heavy load in the starting or stopping state of ship propeller stern shafts, it is very difficult to form the effective lubricating films between water-lubricated polymer stern tube bearings and shafts. Under these extreme conditions, friction and wear usually are severe problems, which can induce frictional vibration and noise. In this study, graphene nano-sheets (GNS) were chosen to modify the polymer which was often made into the ship water-lubricated stern tube bearing. The friction-induced vibration and noise behaviors of the modified polymer materials were carried out using a wear test apparatus with precision vibration and noise sensors under the water-lubricated condition. The results showed that friction-induced vibration and noise behaviors of modified polymer materials strongly depended on the content of graphene nano-sheets and wear processes. GNS endowed the modified polymers with a limited excellent self-lubricating to reduce the vibration and noise behaviors. The modified polymer materials with GNS exhibited good friction-induced vibration and noise reduction properties. The knowledge gained in this study aimed at further comprehensively understanding the friction-induced vibration and noise behaviors of the polymer materials and designing a composite material with good self-lubricating and vibration reduction properties.

High-Efficiency Ship Propeller Based on Electric Direct Drive Without Shaft Rim

The ship propeller is a key component of a ship, a device for energy conversion, and a device for converting the energy emitted by the main engine into ship power. The most popular types of shaft-driven propellers derived from propeller propellers are currently on the market, including ducted propellers, pod propellers, and flat-rotating propellers. This type of propeller has many disadvantages of the shaft-driven propeller (system). These shortcomings have caused most of the existing small and medium-sized ships to have problems such as low transportation efficiency, high operation and maintenance costs, noise pollution, and lubricant leakage pollution. Therefore, the shaftless rim electric direct drive has gradually become an important development direction in the field of high-end marine propulsion equipment.