For the past forty years, steam turbine installations have dominated propulsion and electric power generation onboard LNG carriers. The ease with which these installation can utilize boil-off gas and their apparent reliability have kept them in a position that has long been lost to diesel engines in all other segments of the shipping industry. Steam turbine installations are, however, not very efficient. This has a negative impact on both the ship operating economy and its exhaust gas emissions. Exactly these issues play an increasingly important role in LNG shipping today. Initially encouraged by the latest developments in its gas engine technology, Wartsila started looking for more economical and environmentally friendly ways to power LNG carriers. We studied machinery alternative with two- and four-stroke diesel, high-pressure gas-diesel, and low-pressure dual fuel engines, in mechanical and electrical and electric propulsion arrangements, with and without boil-off reliquefaction plants. Dual-fuel-electric installations were found to be the most attractive alternative to steam turbine installations. The first dual-fuel-electric LNG carrier, Gas de France Energy will go to sea later this year and two more duel-fuel-electric LNG carriers are on order, Further orders for duel-fuel-electric LNG carrier are expected any time soon.
Propulsion systems of LNG carriers have, until now, been dominated by steam turbine plants. However, MAN B&W Diesel has recently succeeded in getting orders for two-stroke diesel engines in LNG carriers, and a general change from steam turbine propulsion to other types of propulsion seems under way as shipyards update LNG carrier designs. MAN B&W Diesel offers two different two-stroke diesel engine solutions for propulsion of LNG carrier, viz. an ordinary fuel oil diesel engine with a reliquefaction plant, and a dual fuel ME-GI diesel engine. This paper provides a general description of these solutions, focusing on items that make them different from ordinary ME two-stroke diesel engines, and of the installation thereof.
Until recently, LNG carriers have been equipped with steam propulsion systems. Boil-Off Gas (BOG) is then fired in the steam generating plant by dual fuel burners. When the amount of BOG is greater than required for propulsion, excess steam is dumped into the main condenser of the steam turbine and cooled down. The main condenser is sized accordingly. This dumping facility is not available for LNG carriers with alternative propulsion systems, however. New ship designs thus require a safe and economical BOG treatment when there is no other use for the gas. Venting to the atmosphere is not considered acceptable for environmental and safety reasons.
Unlike all cargo ships, liquefied natural gas (LNG) carriers have continued to use steam turbine propulsion plant despite more efficient diesel engine being available. This is because the gas that naturally evaporates from the cargo (called boil-off) is used as fuel for the steam turbines, and until recently there was no other use for it. The ability to reliquefy the gas given off by the cargo now makes it possible to increase the amount of LNG delivered to the discharge port, which is more profitable than using it as ship' s bunker. Reliquefying LNG and returning it to the cargo tanks means that gas never enter the engine room, adding to the general safety margin. Total separation between cargo and engine room means that the propulsion system and type of fuel used can be chosen freely.
This report describes the performance of straight-wing, vertical-axis wind turbine generation systems installed on a ship. These systems have already proven able to operate at high efficiency not only in inland areas but also in coastal areas. The experiment was carried out to determine the feasibility of using the systems on a vessel traveling at sea.
During the past years great efforts were taken to investigate particle emissions from diesel engines installed in on-road and off-road vehicles. Optimization of engines and after treatment devices led to a substantial reduction of emissions from these engines. However, there is not much knowledge about particle emissions of diesel engines operated on sea. A first particle emission study was performed in May 2000. Particle emissions of a turbocharged common rail two-stroke marine diesel engine (4RTflex-58T-B from Wartisla Switzerland Ltd.) were investigated at various operating conditions and two different fuels. Size distributions were measured with a SMPS (Scanning Mobility Particle Sizer) . In addition filter samples were taken for gravimetric and chemical analysis. The diameters of the particles range between 20-40 nm independent of the operation point. No pronounced accumulation mode was found but a high nucleation mode. The particle mass is dominated by volatile organic material.
The authors have developed a new technology that enables use of lubricating oil (LO) semi-permanently and reduces LO consumption. This technique always keeps LO clean, just as the kidneys of animals always keep their blood clean. It is, therefore, called a kidney system. The key element of the kidney system is a new type of filter, called a nephron filter. This filter completely removes oxidized LO, which is very sticky and thus increases friction in cold and motionless engines. Diesel engines for emergency electric power fail in many tests of starting which may result from high friction caused by the cold and sticky products built up in LO during the long periods of engine stop. This paper proposes a method that ensures starting of emergency diesel engines by use of a kidney system.
A friction and wear test in seawater environment was performed in seawater to select the materials for oscillatory sliding bearings employed in multi-degrees of freedom couplings that make feasible ocean floating bodies of multi connecting floating systems for marine developments and applications. We tested and analyzed tha five kinds of plastics including PTFE, phenolic and PA (poly-amid) resins, and two kinds of anticorrosive metallic alloys sliding against the SUS304 shaft. were tested and analyzed. The test environments used included seawater, atmosphere and seawater-atmosphere repeated conditions, and also the operating contact pressure was changed under a fixed sliding speed. The results obtained indicate that PA resin and anti-corrosive copper alloy with graphite have better wear resistance than other materials and can be put to practical use for the marine couplings. The PTFE resins show low friction coefficient but high wear rate, and the phenolic resins show both high friction coefficient and high wear rate. Pb-Cu sintered alloy is of no practical use because of an indication of seizure in atmosphere.