TWO-STROKE ENGINES
FIRST FITS2 IS FITTED INTO BULKCARRIER NEWBUILDING The engine trials for the first installation of ABB’s Flexible integrated Turbocharging System for Two-Stroke Engines (FiTS2) were carried out in May 2020
8 The first installation of ABB’s Flexible integrated Turbocharging System for Two-Stroke Engines (FiTS2) solution is due to enter service in 2021
The trials in China had to be monitored remotely as Covid-19 restrictions prevented anyone from ABB or the engine designer WinGD attending the tests, explained Alexander Mutter, Senior manager, product management low-speed for ABB Turbocharging. “Nevertheless, we achieved very good results,” he told The Motorship. The engine and its turbochargers are destined for a bulk carrier under construction at China’s Bohai shipyard for a Singapore-based shipowner Berge Bulk due to go into service in Q1 of 2021. The tests were carried out at the yard on the ship’s WinGD 6X72-B engine and Mr Mutter confirmed the performance figures reported here on 9 October, when ABB Turbocharging’s Senior Vice President Christoph Rofka spoke of fuel savings of up to 6g/kWh when the FiTS2 technology is engaged, which represents savings of 3-5%. As reported in February 2018, the system was developed jointly with WinGD, which had developed a special engine tuning to suit FiTS2. Speaking last month, Mr Mutter said that development work had started in 2016 in response to the trend for slow steaming, resulting in engines being operated at 50% or less of their rated power. Tests were conducted at Diesel United in Japan on a sixcylinder version of the X72 engine and those have provided “the backbone” for the project, Mr Mutter said, because they demonstrated not only the fuel savings but also that NOx emissions could be maintained at IMO Tier II levels. A FiTS2 installation comprises either two or three turbochargers - for the Berge Bulk installation, the engine has two of ABB’s A265-L units - one of which can be cut out for low-load operation even at relatively high engine loads.
18 | NOVEMBER 2020
It is this ability that puts the F - for flexibility - into FiTS2 and this feature, along with its compact design, were two goals behind its development, Mr Mutter recalled. On normal turbocharger installations, it is necessary to reduce the engine load to 10% or even less before the turbocharger valves can be operated to remove one turbocharger from operation, which can take half an hour or more, Mr Mutter said. This flexibility could provide valuable support to ships operating in areas where there is a risk of piracy, he suggested: because the turbochargers’ valves can operate at high loads, a ship operating at low load on one turbocharger could immediately accelerate and the second unit would come on stream as the power increased. These valves are mounted directly on the turbocharger, which is an unusual arrangement he said, to contribute to the system’s compact layout. Although both turbochargers on this first application are the same model, they have each been modified so that one delivers 60% of the air to the engine and the other 40%. When the engine is operating above 50% of its rated load, both units are in use but at lower loads the smaller turbocharger is turned off. This channels all the exhaust through the remaining unit which can then deliver a higher charge pressure than if the exhaust was shared between both units. On a triple-turbocharger installation, each could provide 33.3% of the air supply. This arrangement has an added benefit at low loads since the auxiliary blowers will only be needed below 20% engine load, rather than the normal 30%, which saves energy - and thus fuel - because of their reduced use. Mr Mutter estimated that this can add a further 1.2g/kWh of fuel savings.
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