Overview
Many old fleets currently operate without having updated the propulsion designs to new working conditions. Propulsion efficiency decays as time elapses, inducing a rise in fuel consumption, contaminant gas pollution, engine maintenance costs and vibrations while the ship's capabilities decrease.
Fishing and tugboat fleets are the largest fleets of boats operating all over the world; from the smaller boats sailing near the coast to large trawler vessels, there is a wide range of fishing vessels crossing the seas. The average operating lifetime for these kinds of vessels can be estimated at around 25 years. Since they are used for working in two different conditions (fishing and sailing to and from port and searching for fish), the design of the propulsion is conditioned by these different working conditions.
With time, propulsion becomes less and less efficient. Using an appropriate economic knowledge of the actual situation of such fleets it is possible to estimate the feasible cost reduction in fuel consumption and maintenance, as well as gas emissions and vibration phenomena. Economic tools, together with engineering tools will be developed for the systematic updating of the propulsive (propeller and stern area) system to the new optimum working point, in order to reach the main aim of the proposal. A standard methodology for this updating procedure was the main outcome of the project.
The project focused on developing maintenances strategies, with regard to ship hydrodynamics, and to assess their costs in order to update the propulsion system of the targeted fleets (fishing vessels and tugboats) to their new working conditions after years of operation. Improvements in fuel consumption rates and reductions in maintenance costs are expected.
The other SUPERPROP objectives are:
- to increase the knowledge about the state of the art in old ships' propulsions and their ageing process;
- to use the knowledge in correlation methods to extrapolate results obtained from model testing to full-scale;
- to apply CFD codes to predict propeller behaviour, to collate computational and model testing results, and to estimate the prediction accuracy of both methods;
- to study the economic profitability of old fishing and tugboat fleets and the savings that could be reached in fuel consumption, maintenance costs and contaminant gases emission by optimising the maintenance strategy from the hydrodynamic point of view.
The main output of the project was a techno-economical model, which will permit the devising of maintenance strategies for tug and fishing vessels already in operation, taking into account a range of ageing effects. An indirect result was a reduction of fuel consumption, which is associated with fewer costs and less gas emissions. The results obtained from SUPERPROP focus on sustainable development. Most of the high-power thermal engines are working in ships, so the aim of improving the efficiency in this field is clearly an important factor to be considered in the contribution to air pollution.
The improved knowledge of the decreasing performance over time of a vessel's operating life helped in the first stages of this project. Therefore, SUPERPROP contributes to the 'advanced design and production techniques' objective. This will benefit European shipping within the shipbuilding, supplying industry, consultancy and fishing industry sectors. Concentration on advanced propulsion design, which relies on technology development, will enable the industries to stay competitive.
First, a review of fishing and tugboat technology and operation economy of the owners' fleet was performed. Information from the real situation of old ships' working conditions (economic and technical) were collected. The new ship design condition is not valid from a redesign point. Hence, flow around the selected vessels, reproducing the full-scale measurement conditions were simulated in order to have obtain an improved estimation of the propulsive coefficients for the updating activities to be performed.
The designs were done by different partners and optimum solutions were taken into account for model testing. A generalisation of the obtained results were done in order to use them for ship owners in other cases. Model testing activities were carried out in the different facilities of the consortium. The aim of these activities is to assess more accurately the performance of new designs and redesigns before full-scale manufacturing. Full-scale trials aimed at getting real-scale data from the study cases were performed. Once the modifications were put into practice, another series of trials were carried out in order to check the improvement of the performance.
Analysis activities were done by studying the decrease with time of the propulsion efficiency in the test cases and the eventual rising after the updating activities. The manufacture of new designs or the modification of old ones will follow in time. Activities related to updating criteria, generalisation of results, as well as presenting the technical results of the project in an easy-to-use form, were the last tasks to be accomplished.
Funding
Results
The main outcome of the project was the development of a techno-economic model that allows the development of an economic strategy to predict the profitability of the propulsion. This model actually offers a new optimum point of consumption, i.e the best time to change propeller. It was found out that a new propeller was the optimum solution for increasing the efficiency of old ships. Although the project's partners expected the propellers of old ships to be in worse condition, the old propellers were well optimised for the type of engine and hull they were attached to.
A positive by-product of the project was the numerical calculations, model tests and ship trial data from two real ships, a fishing vessel and a tug vessel related to propulsion and resistance. The project obtained good benchmark data and this huge amount of data (experiments, computations and sea trials) were useful for validation studies.