Propulsion system improvement for trawlers

Many technical solutions on trawler propulsion system can be adopted in order to reduce fuel consumption. Propulsion system efficiency is mainly influenced by propeller and main engine efficiency. Unless the use of slow diesel engines where main engine is directly coupled with the propeller shaft, common high speed diesel engine must be coupled with the propeller shaft through a reduction gear in order to obtain optimum conditions for the whole fishing activity, which, for trawlers, is subdivided in two very different operating conditions: sailing and trawling. A two-speed reduction gear box can be adopted to perform each operating condition without overloading the main engine, thus saving fuel. An open fixed pitch propeller is mostly used in fishing vessels. Bollard pull tests demonstrated the usefulness of a ducted propeller. An improvement in propeller thrust up to 25%, compared to an open propeller with same pitch over diameter ratio, has been observed. Devices such as stators and grim wheel could be considered as useful improvements. Main engine efficiency can be improved using a hybrid diesel-electric propulsion system. Comparative tests on new hybrid concept demonstrated a fuel saving of up to 15%. The abovementioned improvements could be applied simultaneously in the same fishing vessel, each one improving the propulsion system efficiency. Such optimization can be adopted for new or existing vessel.