There is a need for fast ship transportation that is both efficient and non-polluting. Conventional propellers are known to have low efficiency. As an indicative example, most of ship propellers installed on cargo vessels waste about 40 percent of the energy in the form of rotational losses in the wake, vortex generation, noise production, cavitation, etc. The recovery of such losses is one of the major ways to contribute to a more rational, environmentally-friendly use of energy.
The main objective of the TRIPOD project was the development and validation of a new propulsion concept for improved energy efficiency of ships.
The ship propulsion efficiency will be optimised through the advanced combination of three existing propulsion technologies. In particular, the TRIPOD project explored the feasibility of a novel propulsion concept resulting from the integration of two promising EU grown technologies (podded propulsion and tip loaded end plate propellers) in combination with energy recovery based on counter-rotating propeller ('CRP') principle. The three existing technologies have been used separately and are known to improve the overall ship propulsion efficiency as compared to conventional propulsion. However, they have never been combined together in a single propulsion package.
The TRIPOD project contemplated two types of propulsive innovations, which were tested for the first time:
- Using Contracted Loaded Tip ('CLT') propellers in combination with pods;
- Using CLT propellers in connection with CRP propulsion and with pods.
As a result of the investigation tools were developed to assess the optimal use of propulsive energy from environmental and economic viewpoints both for new designs and for the retrofitting of existing ships with the novel propulsion concept.
The State-of-the-Art solution of TRIPOD has established the following results:
- Analysis of data obtained in model tests determined improvements reached in energy savings of up to about 5 percent for the retrofit scenario and 10 percent for the new building one.
- Study of the viability of the new propulsion solutions is made also by performing economical cost benefit analysis for the operation of the reference ships. It was concluded that if the investment level can be brought down, obviously in close cooperation with the relevant specialist suppliers, ship-owners will be interested to explore further installation opportunities especially in new-building projects of large container ships.
- In summary, the real economic criteria to evaluate business proposals have to be applied to each particular case, they vary from project to project, from business case to business case and from market situation to market situation.
- The technical developments proposed within the project will enable more versatile and efficient propulsion systems.
- Significant energy savings and consequently lower emissions are expected from the application of TRIPOD implying cleaner environment. Energy recovery concepts based on the counter-rotating propeller principle and in advanced tip loaded propellers are the key factors to produce such effects.
- Additionally, pod propulsion makes it easier to implement the CRP philosophy avoiding complicated mechanisms in the shaft, and permit more flexibility in defining hull forms with more uniform wakes at the propeller plane.
TRIPOD contemplated two types of propulsive innovations, which were tested for the first
- Using CLT propellers in combination with PODs
- Using CLT propellers in connection with CRP propulsion and with PODs
The methodology of work connected model tests on the one hand and CFD methods on the other. As a result of the investigation tools were developed to assess the optimal use of propulsive energy from environmental and economic viewpoints both for new designs and for the retrofitting of existing ships with the novel propulsion concept.
The new propulsion system set out to make it possible to set as design goal propulsion units of lower noise and vibration levels. Two main factors contributed to the reductions: smaller optimum diameter of the CRP unit as compared to the original propeller (i.e. larger gaps between propeller and hulls) and reduction of loading per unit area as a consequence of splitting the propulsive load between two propellers. Noise/vibration attenuation both improves the quality of life on board and reduces harmful impacts on the environment.
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