The large increase in oil prices of the last years has lead to a lower profitability of many fishing fleets. Depending on the operational profile of the vessel, the fuel costs can be as large as 20 percent to 30 percent of the catch. Therefore ship owners are constantly seeking different ways of reducing fuel consumption in order to remain profitable.
Upgrading the propulsion system to a Wärtsilä HR nozzle is a good start that can lead to remarkable fuel savings, proven by the fact that over the last two decades, some 350 trawler propulsion installations have been delivered by Wärtsilä so far.
In fact, Wärtsilä; LIPS HR nozzle is becoming more and more popular with fishing fleets around the world, with the majority of modern trawlers now fitted with a Wärtsilä propeller and an HR nozzle.
For example, small trawlers are in general fitted with a fixed pitch propeller, while the higher-powered vessels use a controllable pitch (CP) propeller.
A typical mission profile of fishery vessels is characterised by several dominating operating conditions; steaming, searching for fish and trawling and depends on the type of fish they are catching and also the region where the vessels are operating.
During steaming, the free sailing efficiency needs to be as high as possible. While searching for fish and during trawling, radiation of propeller noise needs to be very low in order not to scare the schools of fish. In general, a cavitation-free blade design in the searching and trawling mode is preferred. Finally, trawling requires a large pull, so that a large catch is possible.
The steaming and trawling mode are responsible for the majority of the fuel consumption. Searching for fish is normally done at a low engine power setting and sometimes in combination with reduced propeller speed.
In general when a propeller is heavy-loaded, it is known that a nozzle propeller is far more efficient than an open propeller.
Secondly, the optimisation of the propeller diameter and shaft speed can be evaluated to see if further efficiency improvements are possible.
For propellers already running in a nozzle, the application of a high efficiency nozzle (LIPS HR nozzle) will lead to a more efficient propulsion system.
And at low speeds the delivered pull of a propeller running in an HR nozzle can be 40 percent larger compared with an open propeller.
Compared with other standard nozzles, the HR nozzle shows over the whole speed range up to twelve knots, anything from six to ten percent higher fuel efficiency. Above that range, the HR nozzle outperforms even more.
Thus, taking into account the combination of operating modes, a total efficiency gain of 20 to 30 percent can be achieved when converting from an open propeller to a HR-nozzle and efficiency gain of six to ten percent can be achieved when converting from standard nozzle to HR-nozzle.
According to John Sydney, Managing Director/General Manager Service Sales , this application has many other maritime uses.
"This type of technology can be applied to just about any sea-going vessel currently in service today, including tugboat, barges and even some naval vessels," he said.
"It's all about better utilising the available power whilst cutting fuel costs at the same time," he added Mr Sydney. "And who doesn't want to save money on operating costs these days?"
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