Propeller Performance Research Articles

Predicting practical ship powering and speed loss in waves using added resistance test results

ABSTRACT This paper introduces a practical technique for accurately estimating ship propulsion and speed loss in the presence of waves. Utilising the previously established self-propulsion estimation framework, our approach enhances the method, which previously solely considered bare hull resistance, propeller performance, thrust deduction factor, and wake fraction, by incorporating added resistance test results. The full-scale DTC container ship is the focus of our investigation, providing a thorough examination of its performance in different sea states. The model's predictive abilities are enhanced by incorporating test data on added ship resistance, and it addresses a crucial aspect that is generally disregarded while estimating self-propulsion. This research is considered to be a contribution to the advancement of ship hydrodynamics, as it offers a practical and reliable tool for ship designers, operators, and researchers to accurately assess powering requirements and speed loss in harsh ocean conditions.

A Simplified Model for Propeller Thrust in Oblique Flow

New aircraft architectures are being proposed for unmanned aerial vehicles and air taxis, which include tilt-able motor and propellers. These propulsive units operate with a propeller axis at an angle oblique to the flight direction, and thus it is important to understand and model how thrust is produced by a propeller operating under these conditions. Propellers in oblique flow have been modeled using Blade Element Momentum Theory coupled to an inflow model, and the Vortex Lattice Method. In the present work, we develop a much simpler approach that neglects the crossflow component of the incoming air velocity. An advance ratio is developed based on the parallel inflow component, and is coupled to existing propeller data collected in axial flow conditions. The proposed model is evaluated using existing experimental data collected under oblique flow conditions, and is predicts thrust to within \(5\,\%\) of experimental values for most conditions. The greatest discrepancy between the model and experiments occurs in the pure crossflow case, which is of lesser importance in the application to unmanned aerial vehicles and air taxis.

Degradation Laws and Characteristic Parameters of Performance of Gun Propellant in Storage

Degradation Laws and Characteristic Parameters of Performance of Gun Propellant in Storage

Effects of propeller cavitation on ship propulsion performance in off-design operating conditions

The propeller cavitation is closely related with its hydrodynamic performance. When the propeller works in the cavitating flow, the propeller hydrodynamic performance, in terms of thrust and torque coefficients, is reduced due to the propeller cavitation. When the high-speed and high-power ship sails in adverse sea, the varying loads on propeller will cause severer cavitation on propeller. The reduction in propulsion performance caused by cavitation will further affect the propulsion system, impacting the ship sailing performance and safety. The VP1304 propeller cavitation CFD simulation are conducted to validate the CFD method. Furthermore, the influence of propeller advance ratio and cavitation numbers on the performance of low-speed high-power series propeller in cavitating flow are studied and illustrated. This influence of cavitation has also been transferred to the propulsion system and this process are calculated by the ship propulsion system numerical model. Additionally, the sailing performance of ship propulsion system under off-design conditions, where the cavitation is more likely to occur, has been investigated in this article. Under severe heavy load conditions, it can even result in a complete loss of propulsion capability, posing significant risks. Therefore, it is necessary to further optimize control strategies for the propulsion system to mitigate the hazards caused by cavitation.

Numerical study on effects of leading-edge manufacturing defects on cavitation performance of a full-scale propeller. II. Simulation for the full-scale propeller with defects

Paper II of this two-part paper investigated the effects of leading-edge (LE) manufacturing defects on the open-water cavitation performance of a full-scale propeller based on the geometry of David Taylor Model Basin propeller by using the three-dimensional (3D) steady Reynolds-Averaged Navier–Stokes solver. Various simulation parameters, including domain size, grid size, stretch ratio, first-grid spacing, y+, and turbulence model, were carefully examined for their effects on the solutions, leading to the development of the best modeling practices for the full-scale propeller with LE defects. Employing these recommended best-practice settings, simulations were conducted on the full-scale propellers with 0.10, 0.25, and 0.50 mm LE defects. Compared to the predictions from Paper I [Jin et al., “Numerical study on effects of leading-edge manufacturing defects on cavitation performance of a full-scale propeller—Paper I: Simulation for the model- and full-scale propellers without defect,” Phys. Fluids 36, 105179 (2024).], which did not account for LE defects, the results showed that the LE defects within International Standards Organization (ISO) 484 Class S tolerances narrow the cavitation buckets. As a consequence, such LE defects can result in more than 40% reduction in cavitation inception speed, which is similar to the conclusions drawn from earlier two-dimensional (2D) studies [Jin et al., “2D CFD studies on effects of leading-edge propeller manufacturing defects on cavitation performance,” in SNAME Maritime Convention (The Society of Naval Architects and Marine Engineers, 2020).]. Note that Paper I [Jin et al., “Numerical study on effects of leading-edge manufacturing defects on cavitation performance of a full-scale propeller—Paper I: Simulation for the model- and full-scale propellers without defect,” Phys. Fluids 36, 105179 (2024).] presents the simulations for the model- and full-scale propellers without LE defects.

Numerical and experimental study of the cavitation performance of a composite propeller

Cavitation, which is harmful and unavoidable, has troubled people for a long time and it is urgent to be solved. A composite propeller has the potential ability to improve the cavitation performance because of its distinctive hydro-elastic characteristic, but the related research is limited. In this paper, the cavitation performance of a composite propeller under uniform and non-uniform wake flow is investigated numerically and experimentally. A cavitation coupling simulation method is presented for predicting the cavitation performance of a composite propeller. Cavitation tests are conducted at a cavitation tunnel. The calculated and tested results of cavitation hydrodynamic performance and cavitation patterns are discussed and analyzed. The results show that they are quite consistent, more importantly, cavitation has a significant impact on the hydro-elastic response of a composite propeller.

Numerical study on effects of leading-edge manufacturing defects on cavitation performance of a full-scale propeller. I. Simulation for the model- and full-scale propellers without defect

Paper I of this two-part paper focuses on predicting the open-water cavitation performance of the model- and full-scale propellers based on the geometry of David Taylor model basin 5168 propeller without leading-edge (LE) defect. Simulations were conducted using the three-dimensional (3D) steady Reynolds-Averaged Navier–Stokes solver in the commercial software package Star-CCM+. Effects of simulation parameters, including domain size, grid size, stretch ratio, first-grid spacing, y+, and turbulence model on the solutions were carefully examined and the best-practice settings for the model propeller and the full-scale propeller with no LE defect were developed. Validation studies were carried out for the propeller model against the experimental data. Results for the full-scale propeller were compared with those of the model-scale propeller. The differences in model and full-scale predictions are generally insignificant. To further confirm this finding, the scale effect was investigated with four additional scale ratios, λ = 2, 3, 4, and 5. The results showed that the scale effect is in general minimal and, therefore, the developed best-practice settings can be applied to the open-water simulation of the full-scale propeller. Paper II presents the simulation for the full-scale propellers with LE defects.

Improved combustion performance of solid propellant with sliver nanoparticle decorated Al addition

Improved combustion performance of solid propellant with sliver nanoparticle decorated Al addition

Battery Condition Monitoring of Quadrotor UAV Using Machine Learning Classification Algorithm

Unmanned aerial vehicle flight performance and efficiency rely on various factors. Flight instabilities can happen due to malfunctions inside the system and disturbances from the external environment. Battery status plays a significant role in healthy flight conditions. A weak battery will affect the performance of propellers and motors, and the presence of wind disturbance can contribute towards inefficient flying capabilities. Therefore, investigation of fault at the early stage is crucial to maintain the great performance of the UAV. This paper aims to investigate the best prediction system from the existing machine learning algorithm such as Decision Tree (DT), Linear Discriminant (LD), Naïve Bayes (NB), Support Vector Machine (SVM), K-Nearest Neighbors (KNN) and Neural Network (NN) to classify the battery condition of the quadrotor by extracting the features from the displacement time series dataset. By using recorded flight data, it will be statistically analyzed to extract the flying condition features. The extracted features are the Euclidian distance (ED), speed, acceleration, Periodogram Power spectral density (PSD) and Fast Fourier Transform (FFT) of the signal. The result shows that the two best classifier algorithms are the Decision Tree and Neural Network models with training accuracy of 98% and 93% in Set A and B, respectively.

Analysis and prediction for dynamic migration behavior of NEPE propellant/liner interface layer full components

The migration behavior of nitrate ester-plasticized polyether (NEPE) propellant components significantly impacts safety. Experimentally observing the migration process is challenging and time-consuming. This study employed molecular dynamics (MD) methods to simulate a molecular model of the NEPE propellant/liner interface layer, enabling the prediction of component migration behavior. We visualized the migration process of all propellant components and studied the interface layer components' migration patterns, diffusion coefficients, and concentration gradient distributions. The contents of migrated components of the propellant and liner at different accelerated aging times at 70 °C were determined using high-performance liquid chromatography (HPLC), and the simulation patterns were compared with experimental observations. The results indicate that the migrated components in the propellant mainly consist of nitrate esters (Nitroglycerin, abbreviated as NG, and Butanetriol Trinitrate, abbreviated as BTTN), stabilizers (NMethylnitroaniline, abbreviated as MNA, and 2-Nitrodiphenylamine, abbreviated as 2-NDPA), and solid component (Hexahydro-1,3,5-trinitro-1,3,5-triazine, abbreviated as RDX). The migration process is primarily dominated by the substantial migration of nitrate esters, which is a key factor contributing to the degradation of propellant performance during storage. The migration process can be divided into three stages: swift migration, steady slow migration, and migration equilibrium. The diffusion coefficients are ranked from most significant to most minor as NG > BTTN > RDX > MNA > 2-NDPA. Three migration stages consistent with the simulation process were observed using HPLC, and the migration behavior of nitrate esters aligned with simulation patterns. Our designed full-component model can qualitatively predict component migration behavior. Additionally, a faster diffusion coefficient does not necessarily lead to a greater amount of migration. We employed MD simulations combined with density functional theory (DFT) calculations to explain this phenomenon and found that intermolecular interactions may influence the diffusion coefficient. At the same time, the migration amount is highly correlated with molecular polarity. Therefore, increasing the molecular polarity difference between easily migrating components and liner materials is a beneficial strategy for slowing the migration process and enhancing the storage safety of propellants.

Facile boosting catalytic thermal decomposition of ammonium perchlorate from 3D porous nano Co3O4@ZnO composites

The design of efficient catalysts for the pyrolysis of ammonium perchlorate (AP) is important for the performance of composite solid propellants. Co3O4@ZnO heterojunction composites were fabricated by hydrothermal and calcination treatments and used to promote the thermal decomposition of AP. The influences of the Co/Zn molar ratio on the catalytic performance and the content of decomposition products of AP were investigated by various techniques such as TEM, XPS, BET, EIS, and TG-IR. The results revealed that the Co/Zn = 3 sample exhibited excellent performance with the high-temperature decomposition (HTD) temperature of AP reduced from 410°C to 295 °C and the apparent activation energy decreased to 98.7 kJ/mol in the case of 2 wt% addition, attributed to the construction of a heterojunction with abundant active sites enhancing the charge transfer capability between the Co3O4 and ZnO. The decomposition pathway of AP is influenced by the catalyst components, and the Co/Zn = 3 nanostructures demonstrated outstanding catalytic performance by accelerating the decomposition of HClO4 and the conversion of NH3, and promoting the production of N2O, NO, and NO2. This work provides a feasible strategy for the development of Co3O4@ZnO catalysts with excellent catalytic activity towards AP.

Effect of pre-swirl stator angles on broadband noise considering hydrodynamic performance of pump-jet propeller

A pump-jet propeller is composed of a rotor, stator, and duct. A pre-swirl stator is employed to optimize flow into the rotor. The hydrodynamic and noise performances of pump-jet propellers vary with the stator angles. In this study, the hydrodynamic performance of a full-scale submarine and pump-jet propeller is assessed by conducting computational fluid dynamics simulations based on the Reynolds-averaged Navier–Stokes equation. Additionally, broadband noise, blade-passing frequency noise, and a significant factor, that is, underwater radiated noise are predicted using Lighthill’s equation, Green’s function, and wall pressure spectrum. Unsteady forces were extracted from the flow field to obtain the blade-passing frequency noise. Broadband noise could not be calculated directly from the flow field owing to the absence of small eddies, and wall pressure spectrum was used to obtain high-frequency broadband noise. The overall noise, including broadband noise and blade-passing frequency noise, was evaluated. The optimal stator angle for the rotor at the self-propulsion point was determined considering the propulsion efficiency and noise level of the pump-jet propeller.

A multivariate and wavelet-based analysis on the wall pressure fluctuations for propellers in ground effect

This study, conducted at the University of Bristol’s aeroacoustic facility, explores the aeroacoustic characteristics of a 10-inch APC propeller in pusher configuration within ground effect conditions. Tested at a rotational speed of 7000 r/min, the propeller’s performance was evaluated at varying distances from the ground. Wall pressure fluctuations near the propeller were measured at eight radial points, complemented by far-field acoustic measurements. Consistent with previous research, distinctive thrust and torque behaviours were observed when operating both in and out of ground effect. Notably, a significant noise increase of approximately 5 dB was observed on the ground’s reflected side, while a reduction of about 14 dB was detected on the shielded side. Higher-order statistical analysis such as skewness and kurtosis revealed substantial effects of tip vortex impingement in ground effect conditions. This study applies two-point statistics and the Corcos model to analyze propeller-induced wall pressure fluctuations. The coherence function effectively captures the intricate dynamics of pressure variations across different spatial locations and frequencies. This approach offers novel insights into the behaviour of boundary layers and flow-induced pressures in the context of propellers operating in the ground effect. Wavelet decomposition was utilized to differentiate the influences of the boundary layer and the acoustic field. This comprehensive analysis highlights the intricate dynamics of propeller operation in ground effect, contributing valuable insights to the field of aeroacoustic research.

Crystallization-Based Modification of Ammonium Perchlorate Heat Release.

Composite propellants use the decomposition of crystalline oxidizers, such as ammonium perchlorate (AP), to produce oxidizing species that can combust with fuels. Controlled crystal microstructure must be leveraged to tailor reactivity to minimize the use of exotic energetic materials. This work uses meniscus-guided coating (MGC) to fabricate films of AP with a high degree of control over the AP crystal microstructure. Exploring a wide range of crystallization parameters resulted in film thickness ranging from 200 nm to 14 μm, particle size ranging from 18 to 110 μm, variable preferential orientation with respect to the substrate, and relative defect density ranging from 2.74 × 105 to 6.78 × 105 μm-3. Increasing coating blade speed and substrate temperature within the MGC process shifts the preferential orientation of the AP crystals from predominantly exhibiting (002) and (210) crystal planes parallel to the substrate to (200)/(011) crystal planes parallel to the substrate. This shift in orientation is accompanied by an increase in defect density, which is shown to increase the heat release from the low-temperature decomposition regime and decrease the heat release from the high temperature regime. These results demonstrate the ability to use recrystallization, defect density control, and orientation control to tune the heat release profiles of energetic materials to augment propellant performance.

Study on hydrodynamic performance of multi-link cycloidal propeller

Cycloidal propellers are special propellers that can obtain a wide range of thrust in any direction without changing the propeller rotation speed or requiring the assistance of a rudder. They are typically installed on ships with high-mobility requirements. The implementation of pure cycloidal blade pitch control is complex, and there are a few control mechanisms capable of realizing these blade pitch motions. In this paper, a multi-link mechanism is designed to control the movement of the blades, and the relationships between blade pitch angle, linkage lengths, and their adjustment angles are established. The linkage lengths and their adjustment angles are solved using a genetic algorithm. The blade pitch angle controlled by the multi-link mechanism matches well with the pure cycloidal pitch angle after adjusting the linkage lengths and adjustment angles. The layout of linkages for the six-blade cycloidal propeller is designed to ensure that there is no motion interference between the linkages and their supporting shafts during operation. The open water hydrodynamic performance of the cycloidal propeller controlled by the multi-link mechanism and pure cycloidal pitch motion is analyzed using computational fluid dynamics. The simulation results indicate that the cycloidal propeller can achieve similar performance with different control mechanisms.

Numerical investigation on the ventilated supercavitating model with propeller

To achieve stable and continuous supercavitating flow over underwater vehicles, artificial ventilation is implemented, particularly effective at lower speeds. Previous research on supercavitation primarily focused on analyzing ventilated supercavitating flow with various cavitator types and/or ventilation rates. In this investigation, we examine the behavior of ventilated supercavitating flow over an axisymmetric model featuring both a disk cavitator and a Postdam propeller placed at the bow. Utilizing the Large Eddy Simulation turbulence model, Volume of Fluid method, and Kunz cavitation model, our simulation aims to capture the cavitating flow around the propeller and the ventilated supercavitating flow over the model. Validation of our numerical methods is achieved by comparing our results with experimental data of a ventilated model by Chung and Cho [“Ventilated supercavitation around a moving body in a still fluid: Observation and drag measurement,” J. Fluid Mech. 854, 367–419 (2018)] and the cavitating Postdam propeller by SVA Postdam [S. Potsdam, “PPTC smp'11 Workshop,” in Proceedings of the Workshop on Cavitation and Propeller Performance (2011)]. The results show that with a rotating propeller at the bow of the supercavitating model, the cavitating flow extends and stabilizes compared to configurations utilizing a traditional disk cavitator. The presence of the propeller accelerates the formation of supercavitating flow at a consistent incoming flow speed. Additionally, coupling the propeller with the disk cavitator results in significant increases in propeller thrust, torque, and efficiency. While there is an observed rise in model drag, the impact is not substantial.

Pusher Propeller Performance Investigation on Lightweight Medium Range UAV

Pusher Propeller Performance Investigation on Lightweight Medium Range UAV

Rethinking Propellant-Optimal Powered Descent Guidance

The propellant-optimal powered descent solution requires a bang-bang thrust magnitude profile that switches instantaneously between the upper and lower bounds of the engine thrust. Implementing a bang-bang thrust pattern for guidance can be challenging for the engine and may cause practical and operational difficulties. Motivated by the observation that excellent propellant performance does not appear to be predicated on necessarily having a bang-bang thrust structure, a new powered descent guidance method is proposed in this work. The foundation lies in a propellant-optimal problem in which the thrust magnitude is parameterized by a user-prescribed continuous function of time. In particular, constant and linear functions are considered. The solution determines the optimal thrust direction, time of flight, and design parameters defining the thrust function. An indirect-method-based guidance algorithm is developed to solve this problem rapidly and reliably. Substantial evidence is provided to demonstrate that the solutions proposed in this paper in general yield a propellant consumption very close to that of the optimal bang-bang solution. Given its comparable propellant performance, implementability, and robustness, this paper makes a strong case that the proposed propellant-optimal powered descent guidance approach is preferred to the long-standing bang-bang guidance approach.

Theoretical and experimental study on combustion response of aluminized solid propellant under acceleration effects

The combustion performance of solid propellants is significantly affected by the external operating parameters of rocket motors. In this paper, the combustion response characteristics of aluminized solid propellant under acceleration conditions have been studied theoretically and experimentally. A theoretical model of unsteady burning for aluminized solid propellant, considering transient heat transfer and acceleration effects, is developed based on the Zel'dovich-Novozhilov solid-phase energy conservation. The pressure-coupled responses of the solid propellant are also measured experimentally under different normal accelerations using the T-burner and centrifuge. The model is well validated by comparison with literature and experimental results. The unsteady burning of propellants is analyzed in detail, and the effects of acceleration and propellant properties on combustion response are investigated. The results show that there is a significant difference between the transient and quasi-steady burning rate under dynamic environments. As normal acceleration increases from 0 g to 1000 g, the fluctuation amplitude of the net heat flux on the burning surface continues to decrease, the magnitude of the pressure-coupled response peak decreases significantly by 69 %, and the frequency of the response peak shifts from 140 Hz to 230 Hz. Moreover, the pressure exponent and thermal conductivity plays a positive role in the pressure-coupled response. The model presented in this paper can be helpful for predicting the differences between flight and ground test performance and evaluating the combustion stability of solid rocket motors.

Performance Estimation of Fixed-Wing UAV Propulsion Systems

The evaluation of propulsion systems used in UAVs is of paramount importance to enhance the flight endurance, increase the flight control performance, and minimize the power consumption. This evaluation, however, is typically performed experimentally after the preliminary hardware design of the UAV is completed, which tends to be expensive and time-consuming. In this paper, a comprehensive theoretical UAV propulsion system assessment is proposed to assess both static and dynamic performance characteristics via an integrated simulation model. The approach encompasses the electromechanical dynamics of both the motor and its controller. The proposed analytical model estimates the propeller and motor combination performance with the overarching goal of enhancing the overall efficiency of the aircraft propulsion system before expensive costs are incurred. The model embraces an advanced blade element momentum theory underpinned by the development of a novel mechanism to predict the propeller performance under low Reynolds number conditions. The propeller model utilizes XFOIL and various factors, including post-stall effects, 3D correction, Reynolds number fluctuations, and tip loss corrections to predict the corresponding aerodynamic loads. Computational fluid dynamics are used to corroborate the dynamic formulations followed by extensive experimental tests to validate the proposed estimation methodology.