^ Wartsila X92 Engine (Image Courtesy Wartsila at http://www.wartsila.com/media/news/15-07-2015-wartsila-joint-venture-wingd-to-deliver-wartsila-x92-engine-to-new-mega-class-container-vessel)
Super Engine for Super Container Vessels
Winterthur Gas & Diesel Ltd. (WinGD) is working on the Wartsila X92 low-speed, two-stroke engine to power a container ship of over 20,000TEU capacity. WinGD is a joint venture between the China State Shipbuilding Corporation (CSSC) and Wartsila.
Hanjin Heavy Industries and Construction (HHIC) is building the vessel for the French company CMA CSN at HHIC’s yard in Subic Bay, Philippines.
CSSC acquired Wartsila’s two-stroke engine making business in January 2015 and holds 70% stake in WinGD while Wartsila controls the remaining 30%.
Considering the fact that Wartsila engines power one in every three ships across the globe, the choice of a Wartsila engine for propelling the upcoming colossus does not surprise anyone.
Economies of Scale
Fuel expenses make up a large share in a ship’s total operating costs. This share is between 58% and 78% depending on the type of ship. Any measure that cuts down fuel expenditure is therefore more than welcome.
Leading power and automation technology maker ABB puts the cost of transporting one TEU for one day via sea at:
- about $12 for a 12,500TEU ship
- around $10 for a 18,000TEU vessel
- approximately $9.57 for a 24,000TEU vessel when such a craft is built by about 2017
Clearly, larger ships are more cost-effective. At present, the MSC Oscar is the largest container ship in terms of container carrying capacity with a 19,224TEU capacity.
As the capacities of ships expand, so do their engines. Larger ships are more fuel efficient than smaller ones because:
- Being more stable, large ships need lesser quantities of ballast water. This means, they weigh less and therefore need lesser fuel
- A large ship weighs less and wets lesser hull area than that of two smaller ships of the same total cargo capacity as that of the larger one. Again, this means lesser fuel consumption and lower emissions
Wartsila X92 Engine
Designed as a main engine for 8,000-plus TEU capacity large and ultra large container vessels of today and tomorrow, the X92 is the largest of Wartsila’s X series of workhorses. These engines boast of:
- Very Low Fuel Consumption that is 10% below that of main ship engines of the preceeding generation
The engine achieves this over the complete operating range through a judicious integration of diverse refined features discussed below
- Minimal CO2, SOX, and NOX Emissions
- Choice of Selecting Optimum RPM allows the Use of Large Propeller Diameters
- Minimum Operating Costs
- Configurations of 6 to 12 Cylinders
- Easy Installation of Power Take Off (PTO) Systems for Onboard Electricity Generation
Technical Data for Wartsila X92
|Speed||70 rpm to 80 rpm|
|Cylinder Bore||920 mm|
|Stroke / Bore Ratio||3.77|
|Piston Stroke||3,468 mm|
|Mean Effective Pressure||21.0 / 20.0 bar|
|Brake Specific Fuel Consumption||159 g/kWhto
Features that make the X92 engines exceptionally fuel efficient while slashing emissions include:
- Combination of Long Strokes with a Large Bore, Low Shaft Speeds, and the time-tested electronically-controlled Common Rail Technology
The common rail technology plays a particularly important role by enabling flexible exhaust valve operations and fuel injection. Common rail technology also eliminates smoke emissions from the engines at all loads
It controls each fuel injector separately. This is a distinctive feature of electronically-controlled, low-speed Wartsila engines that trim fuel use throughout the working range and especially at part and low loads
- Low Cylinder Lubrication Consumption of 0.6g/kWh
- Tuning Option allows very low fuel consumption during Slow Steaminge. deliberate cut down of ship speed in order to slash fuel use
- Intelligent Combustion Control (ICC) System balances the operation of each cylinder
These days, container ships are increasingly resorting to practices such as derating and slow steaming. Derating is the reduction of engine power to extend its life.
Ships do this to reduce fuel expenses and the plague of overcapacity that riddles the container vessel segment. Presently, average speed of container ships hovers in the vicinity of 21-25 knots only.
At rotational speeds between 70 and 80 rpm, the X92 engine variants provide power between 24,420 and 73,560 kW. Such low speed operations facilitate better propulsion efficiency.
When fitted with a SCR Catalyst, X92 engines become completely compliant with IMO Tier III NOX emission norms. As it is, they already adhere to IMO Tier II emission regulations.
Engine makers are working on an Exhaust Gas Recirculation (EGR) mechanism for the X92. Optional scrubber systems slash SOX discharges to below 0.1% even if you use high-sulphur fuels.
Excellent reliability, low operating costs, and maintenance-free operations trim down the total ownership cost to unbelievably negligible levels.
When combined with Condition Based Maintenance (CBM) and service agreements, owners and operators can extend the Time Between Overhaul (TBO) for critically important components to well beyond the already durable 5 years.
Common Rail Injection Systems
Unlike a conventional diesel injection system, a common rail injection system separates the process of fuel injection from the generation of injection pressure. It does not rely on the cam shaft to build injection pressure. This means, it always injects fuel at the required pressure.
High pressure fuel injection ensures better atomization of diesel i.e. split up into greater number of droplets when injected in the cylinder. More droplets present a much larger surface area for combustion.
This burns the fuel more efficiently thereby providing better fuel efficiency, greater power, lower emissions, reduced smoke, and lesser noise. If you split one drop of a liquid into 27 droplets of equal size, the surface area of the 27 droplets becomes 9 times that of the large drop.
Injection pressure is independent of engine speed or the quantity of injected fuel. A rail or accumulator creates a high-pressure fuel reservoir while a high-pressure pump boosts this pressure to 1,600 bar. Electronic Diesel Control (EDC) unit controls the pressure and duration of injection.
Apart from engines, ship builders are also investing in the development of turbochargers to power the ever expanding capacities and sizes of container ships. Economies of Scale are playing out at towering levels in the container vessel market.
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