Operating economy focus for NYK series

The NYK Blue Jay (364m loa, 50.6m beam) is the first of ten vessels that, despite their smaller capacity, are designed to compete with new 20,000 teu ultra-large container ships on operating economy. The sleek hull design is enabled by a narrow engine room, allowing for high hydrodynamic efficiency.

The Wärtsilä X-series of two-stroke diesel and dual-fuel engines employ a higher bore-to-stroke ratio than earlier engines, facilitating the larger, slower turning propellers and providing higher engine internal efficiency. The engines were designed by Winterthur Gas & Diesel (WinGD), which manages Wärtsilä’s two-stroke engine business, and built by Diesel United in Japan.

The engines can also be ‘dual-rated’, allowing ship operators to run the engines with either high or low maximum engine outputs – allowing for ships to switch between two operating profiles both with optimised fuel efficiency. The dual-rating capability is based on a system of electronically controlled fuel injection and exhaust valve actuation, combined with turbochargers with very wide compressor maps.

Rudolf Holtbecker, general manager, business & application development, WinGD, said: “Ship owners wish to be able to respond to market conditions by having closer control over the fuel costs of their ships. In recent years this has led to owners operating their ships at lower speeds with engines running below their design ratings.

“With the X engines, the dual-rating option has been introduced to allow ship owners to use their engines either with a low or a high maximum power output, further improving fuel consumption in each operating mode without major modifications.”