Performance Prediction Program for Wind-Assisted Cargo Ships

University essay from KTH/Skolan för teknikvetenskap (SCI)

Author: Martina Reche Vilanova; [2020]

Keywords: ;

Abstract: Due to the accelerating need for decarbonization in the shipping sector, wind-assisted cargo shipsare able to play a key role in achieving the IMO 2050 targets on reducing the total annual GHGemissions from international shipping by at least 50%. The aim of this Master’s Thesis project is todevelop a Performance Prediction Program for wind-assisted cargo ships to contribute knowledgeon the performance of this technology. The three key characteristics of this model are its genericstructure, the small number of input data needed and its ability to predict the performance of threepossible Wind-Assisted Propulsion Systems (WAPS): Rotor Sails, Rigid Wing Sails and DynaRigs.It is a fast and easy tool able to predict, to a good level of accuracy and really low computationaltime, the performance of any commercial ship with these three WAPS options installed with onlythe main particulars and general dimensions as input data.The hull and WAPS models predict the forces and moments, which the program balances in 6degrees of freedom to predict the theoretical sailing performance of the wind-assisted cargo shipwith the specified characteristics for various wind conditions. The model is able to play with differentoptimization objectives. This includes maximizing sailing speed if a VPP is run or maximizingtotal power savings if it is a PPP. The program is based on semi-empirical methods and a WAPSaerodynamic database created from published data on lift and drag coefficients. All WAPS datacan be interpolated with the aim to scale to different sizes and configurations such as number ofunits and different aspect ratios.A model validation is carried out to evaluate its reliability. The model results are compared withthe real sailing data of the Long Range 2 (LR2) class tanker vessel, the Maersk Pelican, whichwas recently fitted with two 30 meter high Rotor Sails; and results from another performanceprediction program. In general, the two performance prediction programs and some of the realsailing measurements show good agreement. However, for some downwind sailing conditions, theperformance predictions are more conservative than the measured values.Results showing and comparing power savings, thrust and side force coefficients for the differentWAPS are also presented and discussed. The results of this Master’s Thesis project show howWind-Assisted Propulsion Systems have high potential in playing a key role in the decarbonizationof the shipping sector. WAPS can prove substantial power, fuel, cost, and emissions savings.Tankers and bulk-carriers are specially suitable for wind propulsion thanks to their available deckspace and relatively low design speeds.The Performance Prediction Program for wind-assisted cargo ships developed in this Master’sThesis shows promising results with a good level of accuracy despite its generic and small numberof input data. It can be a useful tool in early project stages to quickly and accurately assess thepotential and performance of WAPS systems.

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