Flettner Rotors Research Articles

Identification of Vibration for Balancing in Fehn Pollux Ship with ECO Flettner Rotor

Flettner rotors are wind propulsion systems using the Magnus effect to generate thrust, thereby reduce fuel consumption and carbon emissions in the ships. However, rotor unbalance can cause excessive vibrations and energy loss, affecting the performance and stability of the system. There is a need to have a system onboard, which can predict the vibrations. The paper proposes a deep learning approach to predict the vibrations and unbalanced forces of a Flettner rotor based on the data of ECO Flettner rotor onboard the vessel MV Fehn pollux. The paper develops two methods to estimate the direction and magnitude of the unbalanced forces using the reading values of the strain gauges. The work also compares two recurrent neural network models, namely Long-short term memory and Gated Recurrent Unit, for vibration prediction and evaluates their performance using Mean Absolute Error and Root Mean Squared Error metrics. The results show that Long-short term memory model outperforms Gated Recurrent Unit model in prediction accuracy and can be implemented on the system onboard to monitor and prevent rotor unbalance. The paper also suggests some possible solutions for automatic self-balancing of the rotor and identifies some areas for future work.

Novel optimized layout for Flettner rotors based on reuse of wake energy

The application of wind-assisted propulsion contributes to the reduction of pollutant emissions and the protection of the environment. A novel approach for the reuse of wake energy was established to optimize the layout of Flettner rotors based on the idea of migrating geese that fly in a V-shape formation to save energy. The new layout improves the aerodynamic performance of the two-rotor system compared to two separate rotors, and saves deck space. The wake structure, interaction effects, and force coefficients of rotors in the upstream rotor wake were determined in Fluent. A response surface model was developed to describe the relationship between the lift coefficient as the optimization object and layout by using the Kriging method. Subsequently, the particle swarm optimization (PSO) algorithm was used to determine the optimal position of the downstream rotor. Consequently, the downstream rotor is mounted on the high flow side of the upstream rotor. The resulting two-rotor system exhibits a significantly higher average lift coefficient, it has increased to 5.260, which corresponds to an increase of 22.98% from the reference value of 4.277. Improvements in the lift coefficient of the Flettner rotor are beneficial to the capture of wind energy by wind-assisted propulsion vessels.

Flettner Rotor Implication on Ship Ferry The Kalianget-Kagean Route Using Computational Fluid Dynamics

Ship's Ferries are a sea crossing that continues to operate around the time. The consequence related to shipping activities is an increase in ship exhaust emissions. One alternative for ship propulsion that is environmentally friendly is the Flettner rotor. The working principle of the tool follows the theory of the Magnus effect, where the force arises due to the difference in pressure between the two sides of the Flettner rotor. This study implicates the Flettner rotor on the Kalianget-Kangean ferry route with variations in wind speeds of 10, 15 and 20 knots and variations in dimensions of 3x1, 5x1 and 7x1 meters with a rotational speed of 500 rpm. Optimal results through computational fluid dynamics (CFD) simulations show a coefficient of lift (CL) of 3.647 and a lift force (Fl) of 2,980,631.2 kilonewton with dimensions of 5x1 meters and a wind speed of 15 knots. While the implicit percentage of Flettner rotors in KMP. DBS I of 18.11%, KMP. DBS III of 11.27%, and KMP. NS 92 of 5.45%.

Numerical Study on the Aerodynamic Performance of Four Flettner Rotors by Varying Distance and Spin Ratio

Numerical Study on the Aerodynamic Performance of Four Flettner Rotors by Varying Distance and Spin Ratio

The Dimple Effect on Flettner Rotors for the Wind Power Drive System of a Sailing Merchant Ship

Wind-powered ship propulsion is investigated in relation to reducing ship exhaust emissions, such as the application of Flettner rotor systems. How to increase rotor thrust's contribution to ship speed is an intriguing research question. This paper investigates the influence of dimples on the surface of a Flettner rotor on its ability to generate thrust for a ship. The CFD code, which includes the Reynolds average Navier-Stokes equation and the k-ω model for turbulent flow, is utilized to analyse three rotor designs: one with a smooth surface and two with dimple surfaces of varying diameters. Lift and drag are computed by taking into account varying spin ratios and the incoming wind angle. The CFD results are validated by comparing them to experimental data gathered in a wind tunnel and determining that their error is less than 5%. The addition of dimpled surfaces to the rotor increases lift by 69.6% and decreases drag by 14.8% due to the smooth surface. For the case study, the two rotors are mounted on the sailing ship 900 DWT and can generate the most thrust to give the ship a speed of 8.5 knots with a spin ratio of 4 and apparent wind angles of 90o or 270o relative to its speed.

Seakeeping Behaviour of a Flettner Rotors-Propelled Catamaran in Beam Waves

This paper deals with the seakeeping of a catamaran propelled by Flettner rotors. The case study is an energy ship. The prediction of the roll motion of such a ship is of particular interest since she will mostly sail in beam seas. We used a numerical model based on the boundary element method to deal with the interactions of the ship with waves. It is supplemented by a model for the aerodynamic damping effect due to the rotors, the gyroscopic effects from the rotors and by the ITTC correction for roll damping. In the present study, it has been assumed that the Flettner rotors can be modelled as a distribution of elementary airfoils whose lift and drag depend on the local apparent wind speed. Interaction effects between the rotors and between the hull and rotors have been neglected. Regular waves have been investigated. For the considered case study, it is found that the Flettner rotors can have a small destabilizing effect or a small stabilizing effect on the ship motion depending on the ship speed and the rotors’ rotational speed.

Experimental investigation of the aerodynamic performance of Flettner rotors for marine applications

Flettner rotors are becoming alternative wind-assisted propulsion systems for marine applications. This study experimentally investigated the aerodynamic performance of large-scale Flettner rotors with a diameter D = 350 mm, 0 = α ≤ 4.5, 3.5 = L/D ≤ 6.0, 1.0 ≤ De/D ≤ 2.0, and 9.33 × 104 ≤ Re ≤ 3.15 × 105, where α is the velocity ratio, L is the cylinder span, De is the diameter of the endplate, and Re is the Reynolds number based on D. The initial, increasing, decreasing, and stable areas were defined to describe the variation in the time-averaged lift-to-drag ratio K‾ with an increase in α. Both the aerodynamic performance of Flettner rotors and the range of the four areas were significantly influenced by L/D, De/D, and Re. Based on the measurement of the aerodynamic forces acting on the tested Flettner rotor under the influence of an interfering Flettner rotor with the same α, the effects of aerodynamic interaction for different wind incidence angles β and spacing ratios S/D were studied in detail. In addition, the driving and heeling force coefficients were presented for the combination of two Flettner rotors. Once the arrangement of the two Flettner rotors installed on the deck of a ship was known, both the driving and heeling forces provided by the combination of these rotors depended on α and the apparent wind angle.

Wind-Assisted Ship Propulsion: Matching Flettner Rotors with Diesel Engines and Controllable Pitch Propellers

The harvesting of wind energy and its transformation into a thrust force for ship propulsion are gaining in popularity due to the expected benefit in fuel consumption and emission reductions. To exploit these benefits, a proper matching between the conventional diesel engine-screw propeller propulsion plant and the wind-assisted plant is key. This paper aims to present a method and a code for the preliminary sizing of a ship propulsion plant based on a diesel engine, a controllable pitch propeller, and one or more Flettner rotors. A mathematical model describing the behaviour of the rotor in terms of propulsive thrust and power is proposed. The rotor model has been integrated into an existing diesel propulsion model in order to evaluate the ship’s fuel consumption. The ship’s propulsion model is written in a parametric form with respect to the following design parameters: ship dimensions and resistance-speed curve, propeller diameter, engine power, rotor geometry, and true wind conditions. The methodology helps in evaluating the engine–propeller working points and eventually the total ship propulsive power, including the power required to spin the rotor. It provides a way to compare wind-assisted propulsive solutions in terms of fuel consumption and CO2 emissions. A 3000-ton Ro-Ro/Pax ferry has been selected as a case study. Results on the parametric analysis of rotor dimensions and propeller pitch optimization are presented.

Mitigating stochastic uncertainty from weather routing for ships with wind propulsion

Reducing the shipping sector's contribution to climate change requires urgent emission reductions this decade. Both weather routing and wind propulsion offer immediate solutions, where combining sails with efficient routing amplifies the performance of each technology. However, while large emission savings are theoretically available, the impact of stochastic uncertainty from wind forecasts is unknown. Here, we present a novel approach that exploits fuel consumption calculations from over a thousand departures across three routes to characterise stochastic uncertainty. We show that routes with ideal wind conditions and long voyage times are most sensitive to uncertain forecast inputs, reducing savings from Flettner rotors and weather routing by up to 44% when a priori weather routing strategies are used. This paper further shows how an adaptive weather routing strategy can be used as an accurate prediction tool to reduce uncertainty on all routes investigated, reliably amplifying carbon savings from Flettner rotors by between 1.16 and 2.48 times typical great circle route savings. Overall, this paper provides greater assurance around the previously estimated carbon savings that serves to strengthen confidence in a wind-assisted decarbonisation strategy and its potential to provide essential emission reductions this decade.

Comparison of optimal power production and operation of unmoored floating offshore wind turbines and energy ships

Abstract. As the need to transition from global reliance on fossil fuels grows, solutions for producing green alternative fuels are necessary. These fuels will be especially important for hard-to-decarbonize sectors such as shipping. Mobile offshore wind energy systems (MOWESs) have been proposed as one such solution. These systems aim to harness the far-offshore wind resource, which is abundant and yet untapped because of installation and grid-connection limitations. Two classes of MOWES have been proposed in the literature: unmoored floating offshore wind turbines (UFOWTs) and energy ships (ESs). Both systems operate as autonomous power-to-X (PtX) plants, powered entirely by wind energy, and so can be used to produce synthetic green fuels such as hydrogen or ammonia, or for other energy-intensive applications such as direct air carbon capture. The two technologies differ in form; UFOWTs are based on a conventional FOWT but include propellers in place of mooring lines for course keeping, while ESs operate like a sailing ship and generate power via hydro-turbines mounted on the underside of the hull. Though much research and development is necessary for these systems to be feasible, the promise of harnessing strong winds far offshore, as well as the potential to avoid siting regulatory challenges, is enticing. This paper develops models of each MOWES concept to compare their power production on a consistent basis. The performance of the technologies is examined at steady-state operating points across relative wind speeds and angles. An optimization scheme is used to determine the values of the control variables which define the operating point for each set of environmental conditions. Results for each model show good agreement with published results for both UFOWTs and ESs. Model results suggest that UFOWTs can generate more power than ESs under ideal environmental conditions but are very sensitive to off-design operating conditions. In above-rated wind speeds, the UFOWT is able to produce as much power as a conventional, moored FOWT, whereas the ES cannot, since some power is always consumed to spin the Flettner rotors. The models developed here and their results may both be useful in future works that focus on the routing of UFOWTs or holistically designing a mobile UFOWT. Although differences in the performance of the systems have been identified, more work is necessary to discern which is a more viable producer of green electrofuels (e-fuels).

A Techno-Economic Analysis of a Cargo Ship Using Flettner Rotors

In the last twenty years, the global shipping transport demand has strongly increased (around 4% per year since the 1990s), together with the request for new green propulsion technologies to break down carbon emissions and face the costs deriving from the usage of conventional diesel fuels. Flettner rotors (hereafter: FRs) have been identified by several researchers as a promising solution to exploit wind energy on commercial ships, reducing fuel consumption. The present work presents a six-degree-of-freedom (6DOF) ship performance model set up to evaluate the best way of using a pair of Flettner rotors. The study analyses the performance of this propulsion system in consideration of weather and sea conditions, evaluating the related reduction in fuel consumption. A discussion about the economic and environmental advantages of the usage of FRs is provided, considering the costs linked to their installation and the new emission restrictions. Relevant results have been obtained for different routes, speed ranges and rotor dimensions while investigating the best Flettner rotor arrangement to minimise both the emissions and the installation cost payback period.

Techno environmental assessment of Flettner rotor as assistance propulsion system for LH2 tanker ship fuelled by hydrogen

This study presents a novel design and development of a 280,000 m3 liquefied hydrogen tanker ship by implementing a set of 6 Flettner rotors as an assistance propulsion system in conjunction with a combined-cycle gas turbine fuelled by hydrogen as a prime mover. The study includes assessment of the technical and environmental aspects of the developed design. Furthermore, an established method was applied to simulate the LH2 tanker in different voyages and conditions to investigate the benefits of harnessing wind energy to assist combined-cycle gas turbine in terms of performance and emission reduction based on engine behaviour for different voyages under loaded and unloaded, normal as well as 6 % degraded engine, and varying ambient conditions. The results indicate that implementing a set of 6 Flettner rotors for the LH2 tanker ship has the potential to positively impact the performance and lead to environmental benefits. A maximum contribution power of around 1.8 MW was achieved in the winter season owing to high wind speed and favourable wind direction. This power could save approximately 3.6 % of the combined-cycle gas turbine total output power (50 MW) and cause a 3.5 % reduction in NOx emissions.

WIND ASSISTED PROPULSION: INVESTIGATIONS ON THE USE OF SHIP HOLISTIC MODELS FOR PERFORMANCE ANALYSIS

Wind propulsion is one of the most promising technologies to reduce carbon intensity of ships. However, with variable thrust production and induced drift action, sail’s contribution to propulsion is to be evaluated in different ways from traditional propulsors. For sail retrofit projects, where vessels are initially designed to be optimal at single transit speeds with propulsion engine, wind assistance may also induce a degradation of operational efficiency and limit the extend of energy savings. For these reasons, performance analysis should evolve to account for complex energy transfers between propulsion domain and energy systems. A novel Modelica based model is presented in this article, where manoeuvres and energy modelling are used jointly to predict overall efficiency of wind assisted ship concepts. The model is used to evaluate the impact of retrofitting 4 Flettner rotors on the Duisburg test case (DTC) equipped with diesel engines mechanical propulsion system, with oil fired and exhaust gases steam plants and electricity generation from gensets and turbogenerator. Finally, from the analysis of DTC performance in a sweep of wind conditions, potential solutions to increase sailing efficiency are presented, offering new research directions in vessel design adaptation to natural propulsion.

Experimental proof-of-concept of an energy ship propelled by a Flettner rotor

The energy ship is a new concept for offshore wind energy capture. It consists of a wind-propelled ship that generates electricity using water turbines attached underneath its hull. Since it is not grid-connected, the generated energy is stored aboard the ship (for instance, using batteries or through conversion to hydrogen using an electrolyser). This concept has received little attention until today. In this paper, a proof-of-concept of an energy ship propelled by a Flettner rotor is presented. The experimental results are compared to numerical simulations. A very good agreement is obtained, which validates previous numerical simulations that indicate that a full-scale energy ship equipped with Flettner rotors can lead to positive net energy production.

Evaluation of aerodynamic characteristics of a ship with flettner rotors by wind tunnel tests and RANS-based CFD

One wind propulsion system is the Flettner rotor, which utilizes the aerodynamic force generated by the Magnus effect as thrust by rotating a cylinder placed in a flow. The contribution of this type of system to the improvement of fuel efficiency when installed on board a ship can be quantified by Energy Efficiency Design Index (EEDI) specified in the MARPOL Convention. However, a reasonable estimation of the thrust generated by the Flettner rotors is required to properly account for the effects of the rotors in the EEDI. Therefore, in this study, the use of RANS-Based CFD to estimate the aerodynamic forces on a ship equipped with Flettner rotors is considered, and the results of CFD calculations and wind tunnel tests are compared in order to evaluate the accuracy of the CFD analysis. The results show that CFD calculations of the aerodynamic forces on a rotor-equipped ship with model-scale Reynolds numbers agree qualitatively and quantitatively with the results of wind tunnel tests using a scaled model, indicating that CFD can be used as a substitute for wind tunnel tests. Furthermore, the discussion in previous studies using the results of CFD carried out at Reynolds numbers corresponding to the full scale indicates that CFD is capable of predicting the performance of aerodynamic forces acting on a full-scale rotor if the LPP-based Reynolds number Re is more than 1.0 × 106.

RETROFITTING OF FLETTNER ROTORS – RESULTS FROM SEA TRIALS OF THE GENERAL CARGO SHIP “FEHN POLLUX”

In 2018, a German- Dutch project consortium under the scientific direction of the Emden/Leer University of Applied Sciences retrofitted and commissioned the latest rotor development of the Eco-Flettner type on the test ship Fehn Pollux of the Leer-based shipping company Fehn Ship Management. Main design features are both upper and lower endplates with large diameter for improved aerodynamic performance and modular manufacturing. The retrofitting concept is groundbreaking in terms of easy transferability to other ships. Upscaling to a significant share of the world merchant fleet could make a substantial and realizable contribution to climate protection in the short term and potentially reduced transport costs in the long term. The most frequently asked question in connection with modern sail drives is about the performance potential and the associated fuel savings. Transparent performance data is required to enable an economic prognosis for the use of Flettner rotors on ships. The Faculty of Maritime Sciences at Emden/ Leer University of Applied Sciences has developed an automatic control and monitoring system for Flettner rotors that also records extensive operating and environmental data. The data shows that all previous assumptions and model calculations are basically correct. With regard to the performance potential, the first series of measurements show even higher rotor forces compared with model calculations. This is a further benefit for Flettner rotor efficiency and could help the technology achieve a breakthrough as a building block for low-emission shipping.

FLETTNER ROTORS PERFORMANCE AND INTERACTION EFFECTS ON THE MARIN HYBRID TRANSITION COASTER

In the context of ship design, including wind propulsion, knowing the aerodynamic performance of a ship and its wind propulsors is essential. In the literature, the performance of wind propulsors is generally derived from wind tunnel test data, full scale tests or CFD. Those experimental or numerical databases are often omitting the interactions with the ship and its superstructures and atmospheric boundary layer. In this research, a numerical approach using RANS simulations is developed to estimate the effects of the interaction between the MARIN Hybrid Transition Coaster (MHTC) and its three Flettner rotors. In order to assess the effects of these interactions, the performance of a Flettner rotor positioned on the deck of the vessel is compared to the performance of a free standing Flettner rotor. Large interaction effects are found to depend on the apparent wind angle. Accounting for these interactions is essential. A model is proposed to correct the performance of a free standing Flettner rotor to the performance of a rotor on the deck of the vessel. In addition the effects of multiple wind propulsors are studied in relation to this model.

A CFD STUDY ON WIND ASSISTED PROPULSION TECHNOLOGY FOR COMMERCIAL SHIPPING

Wind assisted propulsion has the potential to significantly reduce emissions from global shipping, with a range of technologies available including wing sails, kites, Flettner Rotors, and Suction Aerofoils such as Turbosails. Despite this, there are only a few studies publicly available on the performance of Suction Aerofoils, which operate on the same principle as a traditional sail but use boundary layer suction to develop high lift coefficients. Therefore, a CFD study was carried out in Numeca FINE/Marine software to determine values for the lift and drag coefficients over a range of angles of attack and suction levels. Supplementary studies also investigated the effects of introducing an endplate to reduce end vortices, and the effect of a ship side on the wind speed incident on the Suction Aerofoil. The plots of lift and drag coefficients developed in this paper were used to inform the BMT-led VTAS project [1], as well as contributing to wider knowledge on wind assisted propulsion for shipping. Throughout the study, Suction Aerofoils continued to show promise as an effective means of auxiliary propulsion for ships, and their use should be encouraged as part of the range of solutions to tackle the pressing issue of climate change.

PERFORMANCE PREDICTION AND DESIGN OF WIND-ASSISTED PROPULSION SYSTEMS

Wind-assisted propulsion is seen as one of the main alternatives to potentially achieve large emission reductions in shipping. However, wind-assisted propulsion introduces new challenges in the design, retrofitting and performance prediction as well as the performance analysis. This paper presents and compares methods to predict the performance of wind-assisted propulsion, using the validated performance prediction model ShipCLEAN. Focus is put on evaluating the difference between 1 degree of freedom (1 DOF) and 4 DOF methods as well as the impact of aerodynamic interaction effects in between multiple sails. Practical design considerations and performance differences are discussed based on an example ship. The study includes a comparison of the performance of different sail types (Flettner rotors, Wing sails and Suction wings) under realistic operational conditions.

Using Flettner Rotors and Parafoil as alternative propulsion systems for bulk carriers

The global shipping industry is currently experiencing a tough time due to the sluggish market situation and the oversupply of tonnage. Also, more stringent regulations on exhaust emissions have generated a significant impact on the already delicate market. Leadership in costs is one of the classic strategies to succeed in a competitive environment. Fuel is one of the most important items in the budget to consider when moving cargo across the oceans. However, up to now, there are just a few ships equipped with wind-assisted technologies to reduce fuel expenditures. Positioned in an interdisciplinary framework, this study aims to increase knowledge and understanding about the utilisation of Flettner rotors and parafoil as alternative sources of power to propel merchant vessels. To achieve this purpose, this research draws on data, information, techniques and theories from a variety of sources in both public domain and private databases. The TERA simulation of a parafoil system and Flettner rotors system assisting a 60,000 DWT bulker carrier under different wind patterns was presented. Based on the existing knowledge and scholarship, and the primary data gathered by interviews and questionnaire survey, this paper intends to critically examine the economic benefits derived from the use of two alternative propulsion systems.