Investigation of the fuel consumption of a ship considering the dynamic coupling effect among resistance, propeller torque and engine power under the control of a governor

Abstract

Over the past century, the maritime industry has seen an uptick in demand for shipping and other related services due to increasing globalisation. Year after year, ships are getting bigger, ports are getting increasingly congested, and more and more ships continue to be built to service the thriving maritime sector. However, from an environmental standpoint, shipping continues to be a large contributor to greenhouse gas emissions as large amounts of fuel are consumed on every passage. This problem has become so pervasive that the International Maritime Organisation has imposed new regulations to reach decarbonisation by the year 2035. Methods to achieve this include improving ship design to reduce ship resistance, or simply reducing speed. Given the extensive costs involved to upgrade an existing ship in the fleet, it is likely that most ship owners will choose to reduce their ships’ speed.

Within the ship, the governor contributes to fuel consumption by controlling ship acceleration. Much research has been done on a ship in ideal conditions, that is, calm water conditions, constant ship speed and constant rate of revolutions of the diesel engine. It has been proven that by tuning the parameters of the PI-controller, the speed and the fuel consumption will change, opening up opportunities for further development of the model in real conditions to study the changes in fuel consumption. As it stands, little research has been conducted on real conditions, and it is not known if the PI-controller will respond favourably to fluctuating resistance.

In this study, the aim is to develop a mathematical model to simulate the complex relationships between hull-propeller-engine interactions. Through developing the model, it was found that the engine speed would accelerate at an unrealistic rate, and a slope limiter was fitted in order to control the rate of change of engine speed in line with the manufacturer’s specifications. Thereafter, the effects of using the model to simulate real conditions were studied, with an emphasis on evaluating model performance given real inputs such as wind and wave resistance values. The model was found to imitate the real ship in recorded weather conditions with high accuracy. In the future, further research can be centred on greater optimisation of the existing model, and evaluation of fuel consumption of the ship in given conditions.