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DE F N AS FUE The tougher restrictions on sulphur ox-ides and nitrogen oxides being imple-mented for ships in Emission ControlAreas result in a few options to comply for shipowners. One either has to switch to low sulphur fuels or distillates, use heavy fuel but have a scrubbers in the ex- haust gas system, or switch to usingN as fuel, which reduced NOx by 85 to 90 percent and SOx by almost 100percent. The third option is applicable for newbuildings, and requires an on- shore supply network in place for the liq- uefied natural gas fuel, thus making N suitable for short-sea vessels oper- ating between fixed ports. NANAENAE F ECAS Earlier, in March, Wrtsil secured the order for its dual-fuel gas engines for Finnish 2,600 passenger cruise ferryowner Viking ine, which opted for N as fuel for its two Baltic ferry new- buildings ordered from ST Finland. The first ship is scheduled to enter serv- ice in 201, for operation between Fin- land and Sweden. The new cruise ferries are the largest such vessels to operate on liquefied natural gas sofar. The ice class 1A vessels are 21m long, 1.8m wide and have a gross tonnage of 56,850. There are four ,600kW 850DF main engines in a diesel-electric power plant configuration, with shafts with fixed pitch propellers, driven by two 10,500kW electric propulsion motors.Wrtsil will also supply the onboard N storage, a NPac200 with 2x200cu.m tanks, including the gas sup-ply system.The new technology enables the ferries to meet coming IMO, and EU sulphurand nitrogen restrictions in the Baltic Seaemission control area. The vessel will be the first newbuildings to comply with loyds egister of Shippings provi- sional rules for N propulsion. PMAS NEAED PPEE & UDDE olls-oyce has developed an inte- grated propeller and rudder system thatoffers increased propulsive efficiency without any loss in manoeuvrability. Named Promas, the propeller and therudder are considered as one propulsionunit and are designed together for opti-mum propulsive efficiency. The rudder design is adapted to the particular pro-peller design and is optimised to regain losses from the propeller slipstream,whilst the propeller design utilises thepresence of the rudder bulb and hubcap to recover losses behind the propeller hub. A well-designed twist adapts the rudder to the rotation of the propellerslipstream and reduces the local angle ofattack on the rudders leading edge. This gives a more efficient rudder with lower drag and better recovery of rotational en- ergy from the propeller slipstream. Propeller and rudder are designed to-gether as a single unit for optimumpropulsive efficiency. Propulsive effi- ciency is typically increased by -6 per- cent. In addition it improved low speed manoeuvrability and also improves the possibility for installing low pressure pulse and low noise propeller designs, according to rundit. e says the best results are achieved on blunt single screw vessels with a block coefficient of 0.5-0.85 and a design speed in the 1 to 16 knot range. ere the efficiency gain can be as much as 6-9 percent comparedwith conventional solutions. For faster and slenderer single or twin screw ves- sels such as car carriers, efficiency im- provements of 2-5 percent can be expected. The ferry operator Scandlines is cur- rently building two ferries for their Den- mark-ermany route which will receive one five-bladed Promas arrangement at the centreline and two ,500kW olls- oyces Aipull units, also five-bladed, on the sides. Promas ite, a simplified version of Promas is intended for vessel upgrading. The vessel?s existing rudder is retained, but is fitted with a prefabricated bulb, while the propeller is equipped with aspecial hubcap and new blades. The roro-passenger ferry DFDS Pearl Sea-way received such a system in early 2011. Earlier, in 2010, such a system was installed on Carnival cruise ines Car- nival lory, followed by Vision of the Seas. Both vessels had FP propellers and were fitted with Kamewa bolted pro- pellers during the upgrade. One of the most recent cruise ships re-ceiving Promas ite is Norwegian Sun, received in January new blades for its 5.8m diameter CP propellers with spe-cially designed hub caps and customrudder bulbs on the existing flap rudders. At cruising speed of 1-21 knots, more than ten percent propulsive improvement was achieved, in measurements con- ducted by DNV. Sistership Norwegian Spirit is to re- ceive her Promas conversion later this year. On Pearl Seaway a twin .8m Pro- mas ite propulsion system was installed during the vessels regular dry-docking. DFDSs technical team found the effi- ciency improvement to be up to 12.5 per- cent, representing a payback time ofabout 1.5 years. 34Maritime Reporter & Engineering News FEATURE MARINE PROPULSIONTo meet EPA Tier 3 Caterpillar's 3500C Engine Caterpillar Marine Power Systems announced, in August, that starting in January 2012, its legendary Cat 500C marine engines will enter fullproduction meeting United StatesEPA Tier regulations. We?re pleased to offer our customers im- pacted by the United States EPA reg- ulations a timely, comprehensive power solution that doesn?t require after treatment or sacrifice perform- ance, said Bob allengren, Cater- pillar Marine Power Systems Product and Application Manager. We?re of- fering a wide range of power ratings to the market and were also able to incorporate several new standard fea- tures into the design. The Cat 500C engines will not require after treat-ment modules to meet Tier regula- tions as a result of incorporatinginnovative fuel and air system modi- fications into the design of the en- gines. The 512C Tier is a V12 cylinder engine with a 10mm bore by 215mm stroke and a 58.6 liter cylinder volume. The 516C Tier is a vee-16 cylinder with the same bore and stroke and a 8.08 liter cylinder volume. The engine series has power ratings ranging between 1,1 and ,86bhp. We installed the 516C EPA Tier engines on the Ocean Titan, a 120-ft. -drive tug boat and have been very pleased with the pow- erful performance delivered by the Tier engines, noted Bob Shrews- bury, co-owner of Western Towboats based in Seattle, Washington. It is imperative for our operations to in- corporate sustainable, efficient power solutions into our vessels and we know we can always rely on Cater- pillar. enrik egercrant Western Towboats' Ocean Titan meets EPA Tier 3 emission limits. Wärtsilä secured the order for its dual-fuel gas engines for Finnish 2,600 passenger cruise ferry owner Viking Line, which opted for LNG as fuel for its two Baltic ferry newbuildings ordered from STX Finland.
