Wärtsilä introduced a new, more efficient, Aframax tanker design offering “practical and viable” solutions to meet current and forthcoming emissions legislation. The new Aframax design emphasizes energy efficiency to provide lower operating costs and enhanced environmental performance.
The Aframax vessel type covers tankers ranging from 80,001 dwt to 120,000 dwt; the new Wärtsilä Ship Design (WSD) Aframax is spec’d at 117,500 dwt.
|Rendering of the new Aframax showing the emissions scrubber. Click to enlarge.|
The new Aframax is a single-decked, single-screw motor ship with a double bottom and double shell protection along the cargo area. It features an optimized hull form to minimize resistance, and an optimized propulsion train with energy saving devices (ESDs) for greater efficiency. Fuel savings have been the primary focus during the development of this design, and significant testing of the hull lines by both CFD and tank testing have successfully produced a highly competitive design, according to the company.
The new Aframax uses the high performance electronically-controlled 2-stroke long-stroke / low-speed Wärtsilä X62 engine. The new engine offers high propulsion efficiency in a unique combination of low engine revolutions and an engine design with a minimum physical width. This benefit results in a slimmer aft body design leading to further propulsion efficiency improvements. When comparing the new Wärtsilä X62 to currently available main engine options, a gain of approximately 7% in efficiency can be achieved, according to the company.
With the optimized engine parameters, the required propulsion power for the same vessel speed for the specific vessel can be achieved with one cylinder less (6 cyl) compared to previous generation main engine options. With a propeller diameter of 7600 mm, including a sea margin of 15% and an engine margin of 10%, Power (Pb) of 14,400 kW at 92 rpm is required.
A 7-cylinder version is a solution for even higher efficiency due to the lower rpm and higher de-rating potential that can be achieved. Power of 14,150 kW at 83 rpm is required with a propeller diameter of 7900 mm, including a sea margin of 15% and an engine margin of 10%.
Wärtsilä offers the Aframax design in three, fit-for-purpose versions; the Basic configuration using conventional HFO fuel; Environmental with the exhaust emissions cleaned using a scrubber and selective catalyst reduction (SCR); and the Green version based on dual-fuel engines using LNG. The design can also be adapted for Ice Class notation.