Propeller Performance Prediction Research Articles

Optimization of propellers under consideration of aeroacoustic and aerodynamic goals and installation effects

Advanced Air Mobility (AAM) vehicles like air taxis and cargo unmanned aerial vehicles (UAVs) operate close to urban areas. Therefore, it is necessary to keep the noise footprint of such aerial vehicles at a minimum to gain societal acceptance for AAM vehicle operations. Cargo UAVs are typically highly integrated in terms of functions leading to a high extent of aerodynamic interactions between propellers and the airframe. As a result of these installation effects, unsteady loading noise can become the dominant part of the aerial vehicle noise emissions which leads to a situation, where classical propeller noise reduction measures like blade tip Mach number reduction do not necessarily lead to a reduction in the overall noise emissions. Overcoming these uncertainties in propeller design necessitates propeller noise optimization on an aircraft configuration level. In this work, an existing propeller optimization framework for isolated propellers was extended accordingly: Consideration of propeller inflow velocity perturbations due to installation in the blade element momentum theory-based propeller performance prediction and utilization of a blade element method code (BEM) to consider the scattering of propeller noise on the airframe accounts for configuration noise aspects. Optimization results of a pusher propeller UAV configuration conclude this work.

Application of dimension reduction methods on propeller performance prediction model

Efficient and effective prediction of propeller performance, especially for hydrodynamic performance and fluctuating pressure, have always been areas of interest for ship engineers and researchers. With the rapid blooming of machine learning based surrogate models, it is important to identify proper features that can represent crucial information from numerous features of propellers' geometry design. This paper used five different dimension reduction methods to conduct the feature selection process from propellers geometry. The reduced features are then used as inputs for a random forest based surrogate model to predict both the hydrodynamic performance and fluctuation pressure under cavitation. The experiment results on three test propellers showed that dimension reduction methods such as factor analysis, principal component analysis and random forest feature selection could yield a higher precision for the surrogate model compare to using all features or the main features selected by experience, while manifold learning methods such as isometric feature mapping and locally linear embedding were not good at extracting propellers' geometry. This paper innovatively proposes dimension reduction methods that can automatically extract main features from propellers' complex geometry. With these main features selected, Artificial Intelligence models can yield a higher precision on propellers’ performance predication. Furthermore, these dimension reduction methods have high generalization ability on different types of propellers, which enables a smarter and more cost-efficient way for the preliminary design process of ship propellers.

UNCERTAINTY QUANTIFICATION OF SELF-PROPULSION ANALYSES WITH RANS-CFD AND COMPARISON WITH FULL-SCALE SHIP TRIALS

RANS-CFD is a well-established tool with widespread use in maritime industry and research. Valuable information might be extracted from the results of such simulations in terms of ship resistance and flow field variables. With recent advancements in computational power, it became possible to investigate the performance of ships in self-propulsion conditions with RANS method. This paper presents the results of a study in which self-propulsion analyses of a small size product/oil tanker has been carried out at ship scale. The methodology proposed in this study makes use of open water propeller performance predictions, resistance analyses at model scale and self-propulsion computations at ship scale for a minimum of 2 different propeller loadings to obtain the self-propulsion point and respective performance parameters. In order to speed up the time-consuming self-propulsion computations, these cases have been solved with a single-phase approach. Resistance predictions have been compared with experimental findings. Uncertainty associated with prediction of resistance and thrust has been quantified. Additionally, sea trials have been conducted on the subject vessel and its two sisters and measured delivered power data have been used for evaluating the capability of the numerical method in self-propulsion predictions. Comparison of results indicate that the proposed self-propulsion computation methodology with RANS CFD at ship scale is capable of predicting delivered power with sufficient accuracy at an acceptable computational cost.

A Study on the Scale Effect According to the Reynolds Number in Propeller Flow Analysis and a Model Experiment

The demand for new propeller designs has increased alongside the development of new technology, such as urban aircraft and large unmanned aerial vehicles. In order to experimentally identify the performance of a propeller, a wind tunnel that provides the operating flow is essential. However, in the case of a meter class or larger propeller, a large wind tunnel is required and the related equipment becomes heavy; therefore, it is difficult to implement in reality. For this reason, propeller studies have been conducted via reduced models. In this case, it is necessary to investigate the different performance outputs between the full- and model-scale propellers due to the size difference. In the current study, a method is proposed to investigate the difference in the aerodynamic performance caused by the difference in propeller scale using VLM and RANS calculations, and the differences are analyzed. The wind tunnel test also verified the propeller performance prediction method. The boundary of aerodynamic performance independent of the Reynolds number could be predicted through the VLM based on the ideal fluid assumption. From the RANS calculations, it was possible to present the difference in the aerodynamic performance when propellers of the same geometry with different ratios were operated using different Reynolds numbers. It was confirmed that each numerical method matched well with the wind tunnel test results in the range of the advance ratio that produced the maximum efficiency, and from the results, it was possible to observe the change in aerodynamic performance that differed according to the scale change.

Aircraft Propeller Design through Constrained Aero-Structural Particle Swarm Optimization

An aero-structural algorithm to reduce the energy consumption of a propeller-driven aircraft is developed through a propeller design method coupled with a Particle Swarm Optimization (PSO). A wide range of propeller parameters is considered in the optimization, including the geometry of the airfoil at each propeller section. The propeller performance prediction tool employs a convergence improved Blade Element Momentum Theory fed by airfoil aerodynamic characteristics obtained from XFOIL and a validated OpenFOAM. A stall angle correction is estimated from experimental NACA 4-digits data and employed where convergence issues emerge. The aerodynamic data are corrected to account for compressibility, three-dimensional, viscous, and Reynolds number effects. The coefficients for the rotational corrections are proposed from experimental data fitting. A structural model based on Euler-Bernoulli beam theory is employed and validated against Finite Element Analysis, while the impact of centrifugal forces is discussed. A case of study is carried out where the chord and pitch distributions are compared to minimal losses distribution from vortex theory. Wind tunnel tests were performed with printed propellers to conclude the feasibility of the entire routine and the differences between XFOIL and CFD optimal propellers. Finally, the optimal CFD propeller is compared against a commercial propeller with the same diameter, pitch, and operational conditions, showing higher thrust and efficiency.

Dynamic Wake Identification for Model-and Full-Scale Container Ship

Propeller performance prediction is traditionally based on open water calm model basin tests. In waves, and during vessel manoeuvring, inflow to the propeller changes signifi-cantly, i.e. the shape of the wake field will change and propeller load and efficiency are impacted. This paper focus on the changes in wake fraction that can be identified in dynamic conditions. The effects on wake fraction of ship maneuvering and the effects of waves’ orbital velocity are investigated from experimental data. Model basin tests with a free sailing container ship model provide data for identification of propeller load and mean wake fraction during manoeuvring and during passage of waves. The results are verified with analysis during maneuvering in calm sea with a scale model and with the full-scale version of a 45.000 m3 container ship. Experimental results show the wake fraction variation during maneuvering, and estimates of wake fraction derivatives are found with respect to the relative sway velocity at the propeller. The contribution of the paper is to provide evidence for the magnitude of propeller shaft loads that can be expected during passage in a seaway and during manoeuvring.

Development of a Propeller-ice Cutting Air Test Platform

A propeller-ice cutting air test platform was designed and developed. The platform can measure the thrust torque under the contact conditions of propeller-ice cutting and collision, avoiding the limitation of the open water dynamometer in the range. Experiments show that the test platform has the characteristics of easy equipment installation, good measurement stability, and high range applicability in the measurement experiment, which can meet the needs of experimental teaching and scientific research, and improve the experimental teaching system of propeller performance prediction.

Propeller aerodynamic optimisation to minimise energy consumption for electric fixed-wing aircraft

AbstractAn electric propulsion model for propeller-driven aircraft is developed with the aim of minimising the power consumption for a given airspeed and thrust. Blade Element Momentum Theory (BEMT) is employed for propeller performance predictions fed with aerodynamic aerofoil data obtained from a proposed combined Computational Fluid Dynamics (CFD)–Montgomerie method, which is also validated. The Two-Dimensional (2D) aerofoil data are corrected to consider compressibility, three-dimensional, viscous and Reynolds-number effects. The BEMT model showed adequate fitting with experimental data from the University of Illinois Urbana Champaign (UIUC) database. Additionally, Goldstein optimisation via vortex theory is employed to design pitch and chord distributions minimising the induced losses of the propeller. Particle swarm optimisation is employed to find the optimal value for a wide range of geometrical and operational parameters considering some constraints. The optimisation algorithm is validated through a study case where an existing optimisation problem is approached, leading to very similar results. Some trends and insights are obtained from the study case and discussed regarding the design of an optimal propulsion system. Finally, CFD simulations of the study case are carried out, showing a slight relative error of BEMT.

The impact of biofouling on the propeller performance

Maritime transport industry is facing more and more strict rules regarding the ship emissions. Optimization of maintenance schedule represents an important operational measure, but lack of information related to the potential benefits of the application of this measure represents an important barrier in its application. Consequently, the assessment of the impact of biofouling on ship performance is very valuable. Within the analysis of the impact of biofouling on the ship performance, the effect of the propeller surface condition is frequently neglected. In this paper, the impact of biofouling on the propeller performance in open water condition is analysed using CFD approach, as well as propeller performance prediction method for fouled surfaces on the example of three propellers. The applicability of propeller performance prediction method, which enables rapid and accurate assessment of the impact of biofouling on the propeller performance is demonstrated. Thus, a practical approach that can be used in the optimization of maintenance schedule is presented. Also, this study has indicated the importance of propeller surface condition on the propeller performance in open water condition. Finally, a detail analysis of the flow around fouled propeller in open water condition is provided.

BEM applied to the cup effect on the partially submerged propeller performance prediction and ventilation pattern

This article describes the development of the boundary element method (BEM) to predict the partially submerged propeller (PSP) performance with and without the cup effect, and the 3D unsteady ventilation pattern under an open flow condition. The applied theory is a time-domain BEM, where the perturbation potential is a function of immersion ratio and time. For validation, the unsteady ventilating flow about the 841-B propeller is investigated. It is shown that the formation of the ventilation pattern is captured by the BEM, and the predicted shape of the ventilated surface corresponds well with the experimental observation. Force/moment (components) coefficients are calculated on the key blade of PSP during one cycle in comparison with and without the cup effect. The obtained numerical results are in good agreement with experiments data at high advanced coefficients and in low advanced coefficients reduced.

Recent Developments in Computational Methods for the Analysis of Ducted Propellers in Open Water

This article presents an overview of the recent developments at Instituto Superior Técnico and Maritime Research Institute Netherlands in applying computational methods for the hydrodynamic analysis of ducted propellers. The developments focus on the propeller performance prediction in open water conditions using boundary element methods and Reynolds-averaged Navier-Stokes solvers. The article starts with an estimation of the numerical errors involved in both methods. Then, the different viscous mechanisms involved in the ducted propeller flow are discussed and numerical procedures for the potential flow solution proposed. Finally, the numerical predictions are compared with experimental measurements. 1. Introduction Ducted propellers have been widely used for marine applications. Nowadays, they may be found in tugs, trawlers, tankers, bulk ships, warships, and in dynamic positioning systems of offshore platforms or vessels. The duct may be classified as an accelerating or decelerating type. Accelerating ducts are often used to increase the efficiency and thrust of heavily loaded propellers. In the case of a decelerating duct, they are used to reduce the risk of cavitation and resulting noise. The complex interaction which occurs between the propeller and duct makes the hydrodynamic design of such systems a complicated task. For the selection of the numerical simulation tool, the designer has to choose between a simplified method that predicts the main features of the flow field around the ducted propeller, and a more complex tool that provides detailed information in problematic areas such as the gap region between propeller and duct inner surface. On the other hand, model tests in a towing tank or cavitation tunnel may be seen as an alternative, but they are usually expensive. Presently, the development of an accurate and cost-effective numerical method for the design and analysis of ducted propellers is still not complete.

Grid Type and Turbulence Model Influence on Propeller Characteristics Prediction

This paper evaluates the applicability of the hexahedral block structured grids for marine propeller performance predictions. Hydrodynamic characteristics for Potsdam Propeller Test Case (PPTC), namely thrust and torque coefficients, were determined using numerical simulations in two commercial solvers: Ansys Fluent and STAR-CCM+. Results were attained for hexahedral and tetrahedral hybrid grids equivalent in terms of cell count and quality, and compared to the experimental results. Furthermore, accuracy of Realizable k- ϵ and SST k- ω turbulent models when analyzing marine propeller performance was investigated. Finally, performance characteristics were assessed in cavitating flow conditions for a single advance ratio using Zwart–Gerber–Belamri and Schnerr and Sauer models. The resulting cavitation pattern was compared to cavity extents and shape noted during measurements. The results suggest that hexa and hybrid grids, in certain range of advance ratios, do provide similar results; however, for low and high ratios, structured grids in conjunction with Realizable k- ϵ model can achieve more accurate results.

On the use of the [formula omitted] transition model for the prediction of the propeller performance at model-scale

The goal of the present work is to improve the prediction of propeller performance at model-scale using a local correlation transition model. Results are presented for two marine propellers for which paint-tests have been conducted and experimental open-water data is available. The numerical results using the k−ω SST turbulence model and the γ−R˜eθt transition model are compared with the experiments. In order to distinguish between numerical and modeling errors in the comparison with experimental results, a verification study using a range of geometrically similar grids with different grid densities is made. The influence of the turbulence inlet quantities on the numerical results is discussed and boundary-layer characteristics are presented. Finally, the numerical predictions are compared with the experimental results. An improvement in the flow pattern is achieved with the transition model. However, the model strongly depends on the turbulence inlet quantities for the prediction of the transition location. Both propellers show an increase in thrust of 2%–4% and similar torque when using the transition model.

A comparison of post-stall models extended for propeller performance prediction

Purpose The purpose of the paper is to analyse different post-stall models, originally developed for use in wind turbine codes, and extend their use to the propeller performance prediction.

Steady cavitating propeller performance by using OpenFOAM, StarCCM+and a boundary element method

Accurate and reliable numerical predictions of propeller performance are a fundamental aspect for any analysis and design of a modern propeller. Prediction of cavitation and of cavity extension is another important task, since cavitation is one of the crucial aspects that influences efficiency in addition to propagated noise and blade vibration and erosion. The validation of the numerical tools that support the design process, including open-source codes, is, consequently, essential. The public availability of measurements and observations which cover not only usual thrust and torque in open water conditions (including cavitation) but also unsteady functioning with pressure pulse measurements in the case of the Potsdam Propeller Test Case certainly represents an extremely useful source of information and an excellent chance for verification and validation purposes. In the present work, the prediction of the Potsdam Propeller Test Case propeller performance using the OpenFOAM computational fluid dynamics package is proposed. After a preliminary validation and calibration of the OpenFOAM native Schnerr–Sauer interphase mass transfer model for cavitating flow, based on the experimental results on a 2D NACA66Mod hydrofoil, open water propeller performance and cavitation predictions are carried out. The OpenFOAM results are finally compared both with the available experimental measurements and with calculations carried out with StarCCM+ and with a proprietary boundary element method code, in order to assess the accuracy and the overall capabilities of the open-source tools (from meshing to post-processing) available in the OpenFOAM package. The comparison, in addition to assessing the accuracy of the open-source approach, is aimed to verify its advantages and drawbacks with respect to widely used solvers and to further verify the reliability of traditional boundary element method approaches that are still widely adopted for design and optimization (thanks to their extremely higher computational efficiency) in a very demanding test case.

Integration of Airfoil Stall and Compressibility Models into a Propeller Blade Element Model

The blade element method is an indispensible engineering design tool. It executes rapidly on a personal computer and is capable of accurate propeller performance predictions. An extensive literature survey reveals that for conventional high-aspect ratio propeller blades lifting surface and computational fluid dynamics approaches add a large degree of complexity without providing significantly improved performance prediction capabilities as compared to the blade element/vortex theory. The accuracy of the blade element method is, however, highly dependent on the fidelity of the airfoil aerodynamic model. The primary focus of this paper is on presenting a nonlinear aerodynamic model of airfoils that can be used in combination with the blade element method for enhanced propeller performance prediction over a wide range of advance ratios. The proposed nonlinear airfoil model includes effects of angles of attack up to 90 degrees and compressibility corrections. Results of this method are validated against experimental measurements. Excellent agreement between experiment and prediction is shown for subsonic helical tip Mach numbers.

Hydrodynamic analysis of the surface-piercing propeller in unsteady open water condition using boundary element method

This article investigates numerical modeling of surface piercing propeller (SPP) in unsteady open water condition using boundary element method. The home code based on BEM has been developed for the prediction of propeller performance, unsteady ventilation pattern and cross flow effect on partially submerged propellers. To achieve accurate results and correct behavior extraction of the ventilation zone, finely mesh has generated around the propeller and especially in the situation intersection of propeller with the free surface. Hydrodynamic coefficients and ventilation pattern on key blade of SPP are calculated in the different advance coefficients. The values obtained from this numerical simulation are plotted and the results are compared with experiments data and ventilation observations. The predicted ventilated open water performances of the SPP as well as ventilation pattern are in good agreement with experimental data. Finally, the results of the BEM code/experiment comparisons are discussed.

A Wake Model for the Prediction of Propeller Performance at Low Advance Ratios

A low order panel method is used to predict the performance of propellers. A wake alignment model based on a pseudounsteady scheme is proposed and implemented. The results from this full wake alignment (FWA) model are correlated with available experimental data, and results from RANS for some propellers at design and low advance ratios. Significant improvements have been found in the predicted integrated forces and pressure distributions.

와류격자법에 의한 프로펠러 성능추정 향상을 위한 제안

Current trends in propeller design have led to the need for extremely complex blade shapes, which place great demands on the accuracy of design and analysis methods. This paper presents a new proposal for improving the prediction of propeller performance with a vortex lattice method using the lifting surface theory. The paper presents a review of the theory and a description of the numerical methods employed. For 8 different propellers, the open water characteristics are calculated and compared with experimental data. The results are in good agreement in the region of a high advanced velocity, but there are differences in the other case. We have corrected the parameters for the trailing wake modeling in this paper, and repeated the calculation. The new calculation results are more in agreement with the experimental data.

Numerical Prediction of Propeller Performance During Propeller-Ice Interaction

The aim of the present study was to predict propeller performance during propeller-ice interaction. Total loads acting on a propeller blade during propeller-ice interaction were assumed to consist of three major components: separable hydrodynamic loads, inseparable hydrodynamic loads, and ice milling loads. A panel method and an empirical formula were used for the hydrodynamic load calculations and the ice contact load calculations, respectively. This empirical model was implemented into a numerical panel code. The numerical prediction model for the ice loads including the detailed implementation is described, and the results are compared with experimental results.