Propeller Design Research Articles

Влияние неравномерности потока за корпусом модели одновального судна на гидродинамические и кавитационные характеристики отдельной лопасти в составе гребного винта

Object and purpose of research. This paper investigates wake non-uniformity effect of single-shafter model upon local and integral hydrodynamic and cavitation parameters of separate blade of its propeller. The study was performed on propeller models KP505 and containership models KCS. Materials and methods. Local and integral hydrodynamic parameters of propeller and container ship were obtained as per CFD methods. Viscous flow parameters are obtained through finite volume (FVM) solution of unsteady Reynolds equations (URANS) closed by biparametric semi-empirical turbulence model. Main results. The paper demonstrates that local and integral parameters of separate blade in “hull-propeller” system are considerably different from those determined in the uniform wake at the speeds obtained for the nominal wake field in behindhull conditions. Conclusion. Krylov State Research Centre experience of numerical calculations shows that 1) in many aspects of marine hydrodynamics numerical techniques are more informative than model tests and 2) in a number of cases, conventional propeller design approach based on the nominal wake field data (calculated or experimental) might lead to somewhat incorrect technical solutions.

Multi-objective optimum design of propellers using the blade element theory and evolutionary algorithms

Multi-objective optimum design of propellers using the blade element theory and evolutionary algorithms

Design and analysis of marine propeller with new blade sections

The main purpose of this study is to propose a new method for designing two-dimensional blade sections. In this work, two marine propellers are investigated. The blade section of the newly designed propeller, as compared with that of the MAU5-80 propeller, has a certain angle of attack. Except for the ordinate of the two-dimensional blade section, other parameters of the modified propeller, such as the blade section thickness and the area ratio of the propeller, are the same as those of the MAU5-80 propeller. When designing the new propeller model, the two-dimensional blade section, which has the highest efficiency among all blade sections at the same radius, is used as the blade section of the modified propeller. The numerical result indicates that when the thrust loading coefficient is greater than 1, the propulsive efficiency of the modified propeller is comparable to that of the MAU5-80 propeller. However, when the thrust loading coefficient is less than 1, the propulsive efficiency of the modified propeller is significantly higher than that of the MAU5-80 propeller.

Combining Optimum Propeller Design on Roro Ship Re-engine

Combining Optimum Propeller Design on Roro Ship Re-engine

Tri-Rotor Propeller Design Concept, Optimization and Analysis of the Lift Efficiency During Hovering

This study introduces the simulation of a tri-rotor contra-rotating propeller for thrust force and hover lift efficiency during vertical take-off. Vertical take-off or landing is a method used by many aircraft and makes the vehicle more convenient and easier to use. The second rotor revolved in the opposite direction of the first and third rotors. The proposed multi-rotor system has NACA 0012 untwisted and symmetric airfoil and includes three rotors with two blades for each. The airflow analysis was optimized with computational fluid dynamics simulation by using different pitch combinations to achieve the highest hover lift efficiency with sufficient overall thrust value. The critical angle of attack for the chosen airfoil gave the boundary conditions for the pitch of rotors. The results showed us that the most efficient combinations for three rotors work better with an increase of pitch angle from top to bottom so that there is a difference of at least two degrees between propellers. Experiments with angles of attack within the boundary conditions showed that the blade combinations starting from three degrees and increasing values gave positive and adequate results in many cases. In addition, the results showed that a regular increase in the angle of attack does not relate to a regular increment in thrust force.

A computational iterative design method for bend-twist deformation in composite ship propeller blades for thrusters

Abstract This study investigates the feasibility of utilising common composite material layup techniques in ship propeller blade design to achieve an automatic pitch adjustment through bending-induced twist deformation. A comprehensive design approach, including various reinforcement materials and arrangements, was employed to attain the desired foil pitching, while minimising other undesirable deformation modes. The design process involved iterative computational analysis using finite element analysis and a deformation mode analysis based on foil shape parameters. The research showed that the proposed design approach effectively found options to improve the desired foil parameter pitch, while minimising undesirable deformation modes such as blade deflection and foil shape change. Furthermore, the proposed blade design was tested in thruster steering operational conditions and was found to have a pitch change well matched, potentially countering some changes in fluid flow. When compared to Kumar and Wurm’s design, which only focused on the angular orientation of glass reinforcement, the proposed design was found to outperform the twisting by achieving the same twist for a blade half the length. This study provides valuable insights into the utilisation of composite materials in ship propeller design and highlights the potential for further improvement through a composite engineering design approach.

Large eddy simulation of turbulent wake flow around a marine propeller under the influence of incident waves

In practical applications, propellers often operate beneath incident waves. To investigate the effects of waves on turbulent propeller wakes, a comparative study of the instantaneous flow fields and turbulent statistics of propeller wakes under open-water condition and with incident waves is conducted through the large-eddy simulation framework. The simulations are performed on a Cartesian grid, with the air–water interface captured using a coupled level-set and volume-of-fluid method. The complex geometry of the propeller is captured using an immersed boundary method. The results show that, near the water surface, the existence of incident waves accelerates the wake flow in the axial direction. Both the mean axial velocity and turbulent kinetic energy exhibit phase-lag behavior in the presence of incident waves. Waves increase the instability of the flow in the far-wake region, resulting in the rising of turbulent kinetic energy. Further analysis of the power spectral density shows that the velocity fluctuations gain energy from the waves at low frequencies, and nonlinear interactions between wave-induced motion and turbulent fluctuations transport energy from low to high frequencies as the wake flows downstream. The present study shows the potential of the large-eddy simulation framework to provide engineering guidance and a theoretical basis for the design and operation of propellers in wave environments.

Experimental investigation of propeller noise in ground effect

The aerodynamic propeller performance and aeroacoustic characteristics of a single two-bladed propeller subjected to Ground Effect are investigated using experiments in an anechoic chamber. A strong increase in thrust, torque and power coefficients when a propeller operates in Ground Effect is demonstrated, consistent with previous studies. A low-fidelity Blade Element Momentum Theory model adapted for Ground Effect is implemented to cross-validate the aerodynamic results. The near-field and far-field spectra and their coherence are studied for various propeller distances from the ground plane and compared with the isolated case. The far-field noise measurements indicate that additional tonal peaks appear with the introduction of the ground plane when compared to isolated configuration. While in-Ground Effect, additional high-frequency broadband humps are observed at some polar angles not seen in isolated configuration. Two discrete regions, a shielded and reflection zone, with respective reduction and enhancement of the Overall Sound Pressure levels are observed. The primary reason for noise increase within the reflection zone is a result of pure acoustic reflection from the ground surface. The near-field measurements from an array of embedded high-response microphones in the ground plane indicate that the main source of the propeller noise is in the tip region. Near-field measurements reconfirm flow results from literature with near-field and far-field acoustic results. The present study may find important practical applications within Urban Air Mobility (UAM), especially in the design of vertiport landing pads and propellers for effective noise mitigation, aerodynamic performance, and prediction during the vertical take-off and landing phases of flight.

A Study on Combustion Characteristics of Insensitive Triple-Base Propellant

Research on combustion characteristics can provide basic information and theoretical support for the design of insensitive propellant. This work aims to investigate the combustion characteristics of insensitive triple-base propellant. All propellants were prepared based on same triple-base propellant, but they were desensitized with the same desensitizer in different ways. The high-speed camera, spontaneous luminescence, NO, NH chemiluminescence, and OH-planar laser induction fluorescence (PLIF) methods were employed to capture the combustion flame and derive the distributions of important intermediates. Results show that ignition delay times of insensitive propellants are obviously longer. This indicated that the application of the desensitizer has a partly hindering effect on the early ignition stage. The combustion time of insensitive propellants is mostly similar, which means that the desensitizer has little influence on the intensity of actual combustion. The change in flame height and area of insensitive propellants over time indicated that the combustion progressivity of some insensitive propellants was more prominent, which means that the desensitizer concentration and desensitizing methods all affect the performance of insensitive propellant. The signal intensities of NO and NH show a negative correlation, indicating that a competitive relationship probably exists between the formation of NO and NH radicals during the reaction process. The high concentration of OH mainly locates outside NO, suggesting that there may be a transformation between NO and OH. The maximum signal intensity of NO and NH of different insensitive propellants confirmed that both the concentration of desensitizers and the desensitizing methods exhibit important effect on the reaction process.

Reliability based design of propeller and Rushton impellers for maximizing the overall heat transfer coefficient in coal gasification

The present study aims to identify the optimal process parameters to maximize the Overall Heat Transfer Coefficient for preparation of coal-water slurry used for gasifier in power plants. For this purpose, a jacketed vessel is designed with radial flow (rushton) and axial flow (propeller) impellers to prepare the coal-water slurry. Experiments have been conducted using L9 orthogonal array for Impeller speed (N), ratio of clearance height with diameter of tank (C/T) and ratio of slurry height with tank diameter (Z/T) parameters at three different levels for designed jacketed vessel. The best ranking is arranged in ascending order for propeller Z/T ratio, impeller speed and C/T ratio, for rushton impeller speed, Z/T ratio and C/T ratio. Statistical analysis reveals the percentage contribution of parameters for maximize of heat transfer coefficient in descending order in propeller Z/T ratio (64%), impeller speed (34.92%) and C/T ratio (1.07%), for rushton impeller speed (60.08%), Z/T ratio (36.86%) and C/T ratio (2.48%).

Computational investigation of quiet propeller designs for small unmanned aerial vehicles

The noise produced by the propellers of micro Unmanned Air Vehicles (UAVs) could be counterproductive to their mission, since adversaries can often hear them from a distance. This study investigates new quiet propeller designs that have different twist angle distributions that vary the lift generated along the span of the propeller blade to reduce the thrust loading near the tip. In addition, nine co-rotating dual propellers with different phase angle and spacing are considered. All propellers were tested at the USAFA subsonic wind tunnel at an assumed UAV cruise velocity of 44 ft/s while measuring thrust, torque, sound pressure level, and rotational speed over a range of power settings. These propellers are modeled using the DoD HPCMP CREATETM-AV Kestrel simulation tools. The thrust and torque were extracted from these simulations and compared with experimental data. Pressure tap points were defined one inch behind the propeller. The instantaneous pressure data were measured at these locations for 20 spinning cycles. Sound pressure level values were then estimated from these data. Predictions are then compared with experimental data measured from a traversing microphone.

An experimental study of the aerodynamic performance of a maple wing model at low Reynolds numbers

Maple seeds are widely known for their autorotation and may achieve remarkably long-distance flights owing to their unique wing morphology. These features suggest the adaptability of the blades to wind turbines and air vehicles. However, the effects of these morphological features on aerodynamic force generation are still poorly understood. An enlarged replica of a sample 3D maple wing was produced using additive manufacturing. Direct force experiments were conducted in a low-speed wind tunnel using a two-component force balance to obtain the lift and drag coefficients of the model wing. The polar curves of the wing were obtained for three different Re numbers by repeating the experiments over a wide angle of attack range of -50 to 50°. The best aerodynamic performance is obtained at 18° and -12° attack angles for positive and negative angles, respectively, regardless of the Re number. This preliminary study shows that maple seed can be mimicked in the design of propellers and wind-turbine blades.

High-altitude airship variable-pitch propeller performance analysis at multiple altitudes

To achieve better propulsion performance for high-altitude airships, this paper proposes a variable-pitch propeller design and performance analysis. Propeller surrogate models were constructed based on an in-house fluid–structure solver and validated by a wind tunnel experiment. Based on the surrogate model, this paper studied propeller performance under the common influence of propeller pitch variation and rotational speed, and proved the positive effect of the variable-pitch propeller on maintaining relatively high efficiency in large rotational speed range. This paper compared the performance of variable-pitch propellers and fixed-pitch propellers under the constraints of the motor. The results show that introducing variable-pitch propellers to high-altitude airships can significantly improve propeller performance at multiple altitudes and laminar wind speeds. And the potential of airship weight reduction brought by the variable-pitch technique is discussed as well.

Construction and application of numerical diagram for high-skew propeller based on machine learning

The field of machine learning has experienced rapid growth, and it has introduced a new methodology for constructing propeller diagrams. To meet the high demand for designing high-skew propellers, a series of high-skew propeller schemes are generated, utilizing the INSEAN E1619 as the parent propeller. The Computational Fluid Dynamics (CFD) method was validated using the E1619 test results and was subsequently employed to perform virtual open water tests for all the series schemes. This effort produced 819 open water performance data of 42 propellers. The study trained and validated the traditional multivariate polynomial regression model and five conventional machine learning regression models based on the CFD calculation data. The analysis of the model prediction accuracy indicated that the Support Vector Machine (SVM) model had the least error among them for the digital expression of diagram hydrodynamic data. The prediction error of KT, KQ, and η decreased by over 20% compared to the LM model. The study subsequently developed a high-skew propeller diagram design program using the SVM regression model and applied it to a specific underwater vehicle's propeller design. The design results demonstrated that, compared to the B-series propeller, the design scheme provided by this numerical diagram had a comparable efficiency and a 6% smaller optimum diameter under unlimited diameter and a 7% higher efficiency under limited diameter for this case. Consequently, the developed numerical diagram in this paper provides a new tool for the propulsion performance evaluation and parameter selection of the propulsion system in the preliminary design stage for the high-skew propeller.

Retrofit-induced changes in the radiated noise and monopole source levels of container ships.

The container shipping line Maersk undertook a Radical Retrofit to improve the energy efficiency of twelve sister container ships. Noise reduction, identified as a potential added benefit of the retrofitting effort, was investigated in this study. A passive acoustic recording dataset from the Santa Barbara Channel off Southern California was used to compile over 100 opportunistic vessel transits of the twelve G-Class container ships, pre- and post-retrofit. Post-retrofit, the G-Class vessels' capacity was increased from ~9,000 twenty-foot equivalent units (TEUs) to ~11,000 TEUs, which required a draft increase of the vessel by 1.5 m on average. The increased vessel draft resulted in higher radiated noise levels (<2 dB) in the mid- and high-frequency bands. Accounting for the Lloyd's mirror (dipole source) effect, the monopole source levels of the post-retrofit ships were found to be significantly lower (>5 dB) than the pre-retrofit ships in the low-frequency band and the reduction was greatest at low speed. Although multiple design changes occurred during retrofitting, the reduction in the low-frequency band most likely results from a reduction in cavitation due to changes in propeller and bow design.

Multidisciplinary Optimization Design of Low-Noise Propellers

In this paper, a multidisciplinary optimization design method and its verification of low-noise aircraft propellers considering aerodynamics, noise, and structural strength were carried out to further reduce the aerodynamic noise of the aircraft propellers. The Vortex Lattice Method-based Lift Surface Method and the Frequency-Domain-based Hanson Method were deployed to evaluate the aerodynamic performance and far-field noise of the propeller with validation by benchmark test result comparison, respectively. Integrating both of the aforementioned methods, the constraints, and a genetic algorithm with coding, a joint program was successfully proposed so that the aircraft propeller performance could be optimized comprehensively. In this program, the design variables contain blade structural strength-constrained distribution patterns of the chord length, twist angle, and dihedral angle along the blade radius. A maximum amount of noise reduction was settled as an optimization target. Meanwhile, it ensured no penalty for aerodynamic thrust and efficiency. The optimized propeller was successfully delivered by performing the developed program. Its structure examined strength tests such as static load and dynamic response, and its aerodynamic and aeroacoustic performances were tested at an aeroacoustic wind tunnel. As a result, the optimized propeller reduced its far-field noise emission peak by 2.7 dB at the first BPF under typical conditions and performed a maximum noise reduction of 4 dB for lower-thrust operations compared with the baseline propeller. For the latter operation, noise reduction at the second BPF was also obviously observed.

Multi-fidelity aerodynamic design and analysis of propellers for a heavy-lift eVTOL

This paper presents a multi-fidelity propeller design and analysis process, and demonstrates it for the preliminary design of a heavy-lift eVTOL vehicle proposed by GKN aerospace, known as Skybus. The multi-fidelity framework integrates tools and results of variable fidelity levels. A global scan of the design space was first carried out at the low-fidelity stage. The low-fidelity output was converted to 3D shapes and grids through an automatic meshing tool, and high-fidelity CFD simulations and gradient-based optimisation were launched to deliver further improved designs. The method was first verified using a benchmark multi-modal test function. The framework was then demonstrated for the propeller design of the Skybus vehicle. Rectangular blade designs with linear twist were first derived through the Blade Element Momentum Theory and used as the input to the low-fidelity stage for simplicity. Upon the baseline design, the low-fidelity stage managed to find an improved shape with 3% reduced power, while the high-fidelity optimisation further reduced the power by 2.2% under the equality thrust constraint. In addition, this work also reports the propeller pitch-RPM performance map tool that has effectively supported the Skybus development through fast performance predictions and operating condition determination. For propellers with both pitch and RPM regulation, the performance map explicitly correlates various performance scopes and to aid optimisation. The multi-fidelity construction of the performance map and demonstrations of its usage are then presented.

The effect of different endplate geometries on the hydrodynamic and acoustic performance of the tip-loaded propeller

The tip-loaded propeller design is one of the new methods for improving propellers' hydrodynamic and acoustic performance. This study investigates the effects of different endplate geometries on the performance of a 5-blade B-series propeller with normal skew and rake using the RANSE numerical method. For each of the different geometries, hydrodynamic coefficients, cavitation volume, and propeller noise are calculated. Using an endplate, this research aims to reduce cavitation, tip vortex, and propeller noise. As a result of the research, propellers with a contraction of 0.95R and a flap angle of 60°, as well as propellers with a contraction of 0.9R and a flap angle of 60°, showed better acoustic performance than other propellers, resulting in approximately 7 dB and 5 dB reductions in overall noise for the initial propeller. In terms of hydrodynamic efficiency, these propellers have a reduction of 0.2 and 0.8%, respectively. It can be stated that both propellers are generally optimal both in terms of acoustics and hydrodynamics.

Numerical prediction of ducted propeller performance based on a BEM–RANS coupling method

This paper presents a coupling method that combines the boundary element method (BEM) and the Reynolds-averaged Navier–Stokes (RANS) method to calculate the ducted propeller performance. The software ANSYS CFX is primarily used to calculate the viscous flow around the duct considering the action of the propeller through the distribution of body forces, and the performance of the propeller is evaluated using the BEM in the effective inflow field. A conservative interpolation scheme that converts the pressure obtained from the BEM into the body force of the RANS solver is described. Then, a Kriging interpolation method is used to determine the effective wake by combining the total viscous field and induced velocities from the BEM. Compared with a full RANS approach, this coupling method allows for investigation of the interaction between the duct and propeller with a significantly reduced computational effort and ensures accuracy with a smaller number of meshes. In addition, the coupling method provides a significant effective wake field for propeller design. The proposed coupling method is first applied to the case of an open propeller and is then assessed for the case of a ducted propeller under uniform flow. The results show that the proposed coupling method provides similar prediction results as those obtained using the full RANS approach, with a 79.6% reduction in computational time.

Tombo Propeller: Bioinspired Deformable Structure Toward Collision-Accommodated Control for Drones

There is a growing need for vertical takeoff and landing vehicles, including drones, which are safe to use and can adapt to collisions. The risks of damage by collision, to humans, obstacles in the environment, and drones themselves, are significant. This has prompted a search into nature for a highly resilient structure that can inform a design of propellers to reduce those risks and enhance safety. Inspired by the flexibility and resilience of dragonfly wings, we propose a novel design for a biomimetic drone propeller called Tombo propeller. Here, we report on the design and fabrication process of this biomimetic propeller that can accommodate collisions and recover quickly, while maintaining sufficient thrust force to hover and fly. We describe the development of an aerodynamic model and experiments conducted to investigate performance characteristics for various configurations of the propeller morphology and related properties, such as generated thrust force, thrust force deviation, collision force, recovery time, lift-to-drag ratio, and noise. Finally, we design and showcase a control strategy for a drone equipped with Tombo propellers that collides in midair with an obstacle and recovers from collision continuing flying. The results show that the maximum collision force generated by the proposed Tombo propeller is less than two-thirds that of a traditional rigid propeller, which suggests the concrete possibility to employ deformable propellers for drones flying in a cluttered environment. This research can contribute to the morphological design of flying vehicles for agile and resilient performance.