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Sunday, March 3, 2024

PROPULSION UPDATE: The Latest On Slow-Speed Crosshead Diesel Engines

The MAN B&W range of MC crosshead two-stroke engines covers the widest range of cylinder sizes (from 260mm to 900mm) and unit outputs (2,200 to 51,840 kW/2,960 to 70,440 hp) available from a single marque. Five of the largest and potentially most powerful models, 12K90MC-C, have been built by Hyundai Heavy Industries, which began making MAN B&W engines nine years ago. The engines are installed in 25-knot, super-wide, trans-Pacific containerships owned by the Hyundai Merchant Marine, for which they have a rated duty at 67,080 hp (49,434 kW), but are normally operated at 60,370 hp at 100.4 rpm.

Most recently Spanish licensee Astilleros Espanoles built a similar engine at its Manises factory near Barcelona. This is the first of two engines Astilleros will build for a 400 MW power generation project, which encompasses a four-engine, barge-mounted plant for service in the Phillipines.

MAN B&W has three 900mm cylinder bore models, the longest stroke L90MC slow-running version for tankers and deep draft bulk carriers; the 2,550mm stroke K90MC and the 2,300mm K90MCC for draft limited vessels such as container ships. Only the Japanese, Korean and Spanish licensees have the capacity to build the 12- cylinder engines of this size.

Several models in the range have been improved recently, improvements including increases in the scantlings of the structure and moving parts to meet the higher firing pressures. A new design of shorter, thicker and bore-cooled cylinder liner has been adopted for the engines of more than 600mm bore.

New Sulzer Diesel reported a 17.3 percent increase in the value of orders received and a 33 percent increase in the value of deliveries last year. A major Sulzer engine achievement anticipated in the near future will be the introduction into service of its most powerful engine, a 12RTA84C of (41,260 kW) 56,100 hp, to be installed in the first of two 4,000 teu ulta-Panamax hatch-coverless container ships for Royal Nedlloyd Lines. The RTA84C series of shorter-stroke, large-bore engines has been widely specified for this application.

The DU-Sulzer 7RTA84T engine, presently undergoing tests in Japan, is the first of a new and exceptionally long-stroke engine specially suited to propelling large deep-draft full-bodied tankers, where a very slow propeller speed is needed. This engine has a normal full-power speed of 78 rpm and of 54 rpm at the economy rating E4. This will be the first production engine to incorporate VEC (variable exhaust valve closing) and VIT (variable injection timing), enabling flexibility and sustained fuel economy to be attained over a wide range of powers. This is very desirable for large tankers, which may spend half of their seatime on ballast voyages.

New Sulzer has upgraded its Series 2 RTA engines of520mm, 620mm and 720mm cylinder bore to develop nine percent more power, a benefit accompanied by longer life of components subject to wear and better overall reliability. This may make it possible to install an engine with fewer cylinders, but the advantage of these developments can be taken in the form of a 2 g/kWh reduction in fuel consumption at the MCR.

These advances were made possible by the application of the latest technical developments: the higher powers by changes to the crankshaft shrink-fit and the bearings; extended component life by an improved arrangement of cylinder liner cooling leading to better distribution of wall temperatures and stresses; and new thicker, pre-profiled and plasmacoated uppermost piston rings.

There are now three fuel injection valves, to ensure even firing temperature distribution.

VIT, which maintains optimum fuel efficiency over the full power range, is now electronically controlled. Research Engines The two European crosshead engine licensers now have highly sophisticated full-size experimental engines, upon which development involving higher mechanical and thermal loading can be taken further. These are the Sulzer 4RTX54 "Technology Demonstrator" and the MAN B&W 4T50MX research engine. In each case, provision has been made for widely variable electronic control of the principal events of the operating cycle: fuel injection timing quantity and duration; exhaust valve timing; cylinder liner lubrication; and starting air timing. Hydraulic actuators will eventually enable designers to dispense with the engine camshaft and its gear or chain drive.

Both the Copenhagen and Winterthur designers have very energetic partners in Japan (Mitsui with MAN B&W and Diesel United with Sulzer) who have, over the past few years, built and conducted extended tests of the first production examples of high-powered engines, notably those intended for large and fast container ships.

Mitsubishi enters the international market after many years during which its larger engines were seldom fitted in non-domestic-flag tonnage. Recently, however, a number of the largest models have been exported to Europe for installation in VLCCs. To meet a wider demand, they have extended and updated their range with three new engines, two of them to replace, eventually, less competitive middle-weight models. The third is specifically aimed at the large container ship, a sector for which their European contenders already have well-received, highpowered, faster-running versions.

A modified 600mm engine, the UEC60LSII, has an extended piston stroke and a raised running speed to achieve a 12.5 percent rise in cylinder output to 2,799 hp at 105 rpm, without impaired fuel consumption. The entirely new models are the UEC50LSII of 1,870-bhp (1,375 kW) per cylinder at 124 rpm, and a "mini," the UEC33LSII of 733 hp (539 kW) at 210 rpm, for which a number of orders are in hand.

Perhaps the most striking market success has been the order for the first examples of the container ship engine, UEC85LSC, placed by the Swiss-based Norasia Line for ship building in Germany. This is based on the 850mm by 3,150mm UEC85LSII model, fast becoming established for VLCCs, with piston stroke reduced to 2,360mm and running speed raised from 76 to 102 rpm, for a cylinder output of 5,300 hp (3,898 kW).

The VLCC Cosmo Delphinus has been at sea for months fitted with the pioneer high-powered pair of contra-rotating propellers, driven by 7UEC75LSII engine of 21,400 bhp (15,435 kW).

A report on the performance of this plant is eagerly awaited by the industry, as is the anticipated 15 percent improvement in fuel consumption. Last year Mitsubishi granted a manufacturing license to Dieselmotorenwork Rostock, now part of the major Vulkan shipbuilding, ship repairing and marine engineering group, for its range of cross- Westinghouse intends to manufacture diesel engines such as this Sulzer RTA 84 series low-speed model head engines.

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