Clean power is important for the future of the marine industry. We are playing our part by developing engines and propulsion systems fuelled solely by Liquid Natural Gas (LNG), one of the world’s cleanest energy sources.
The marine industry relies on fuel oils for most powering needs, but tighter emission regulations and the need to ‘go green’ are starting to convince operators to consider alternatives. Rolls-Royce gas engines have proven themselves to be the cleanest, most efficient piston engines on the market. Since the introduction of the Bergen lean-burn technology more than 650 gas engines have been delivered and over 23 million operating hours accumulated.
Mixing gas and air together for combustion at the right time is crucial to maximizing the efficiency of our engines. Bergen lean burn gas engines turn around 50% of the energy in the fuel into power at the flywheel. If a waste heat recovery system is added this figure could potentially rise by a further 20%, depending on the technology used.
The lean burn system combines spark-ignition with a prechamber, so the engine uses a lean mixture of gas and air. At the start of the compression stroke a valve feeds the right amount of gas for ignition into the prechamber, where it is ignited by the spark plug at the right moment.
This charge is directed into the cylinder, bringing enough energy to ignite the lean mixture.
Advanced control systems meter the gas, control the air pressure, valve and ignition timing. Knock sensors detect changes and adjust the control system, ensuring methane slip is reduced to very low levels. The engine combustion technology is robust and ensures that the engines can operate on a wide range of gas qualities.
“Using the Rolls-Royce Power Management system, engines can be run at their most efficient load, minimising fuel consumption and helping our customers cut their total emissions.”
Technical Manager, Island Offshore
Rolls-Royce tailors the entire system design, combining gas engines with an efficient propulsion system to meet individual customer needs and the operating profile of the vessel. We can also add an efficient hull design, and – if needed – a hybrid solution with PTI/PTO to provide system flexibility. Our delivery also includes a complete automation and control system where all equipment is interfaced with optimum efficiency and operating economy.
Cruise Ships and Ferries are perfect candidates for pure LNG fuel because they mainly operate in densely populated or pristine areas where emissions are both visible and a danger to people’s health and the environment. In fact, removing the risk of soot falling onto passenger decks was the initial challenge that got us started looking at emissions from passenger vessels.
Now, rising fuel costs and ever more demanding regulations have made fuel efficiency and emission control the main concerns for passenger ship operators. Passenger ships are highly visible to the general public and LNG is a safe and environmentally friendly fuel. Operators are discovering the benefits of operating on natural gas and most crews would prefer not to work on conventionally fuelled vessels again.
Three types of tanks are available on the market: Type A, B, and C. The vacuum insulated C-type is the most commonly used. It holds a pressure of just below 10 bar which is used to push the LNG through the vaporiser and super heater units, turning the liquid into natural gas.
The gas is then heated to the correct temperature and pressure before being fed into the engines. This is a simple and robust system with no moving parts other than the valves opening and closing to control the flow of liquid and natural gas – and no moving parts means low maintenance.
The Bergen lean-burn gas engines are the cleanest and most efficient piston engines available today, and are classed for both marine propulsion applications and power generation offshore and onshore.
Compared to diesel engines, Bergen gas engines give an emissions reduction of 92% NOx, and around 22% CO2. They also virtually eliminate SOx and particulates, and already meet the IMO NOx Tier 3 requirements that will come into force in 2016.
The Rolls-Royce ship automation system (ACON) consists of a wide range of control, monitoring and alarm products that are designed to control and monitor ship operational systems and equipment. Every gas powered vessel is equipped with an Acon LNG Control System that works as the user interface to the LNG and Engines System, giving the crew complete insight and control of the system at all times.
In addition the system is fitted with the ACON LNG Safety System, an automated safety system that closes down affected areas and moves all the relevant valves in the system to a “gas safe” position in case of emergency. The Acon LNG Control System is usually delivered as part of an integrated automation systems with multifunctional operator stations - Acon IAS. The Acon IAS user interface is tailored to the ship with access to the underlying ship systems through an ergonomic standardised interface, specially designed for safe, easy operation
The Azipull combines the advantages of a pulling propeller with the stability and manoeuvrability of a rudder. It is designed to offer efficient propulsion and manoeuvring on higher speed vessels, and can be linked to any prime mover via mechanical or electric drive (diesel, gas turbine or electric motor) depending on individual customer requirements.
The streamlined leg and skeg recover swirl energy from the slipstream, raising overall propulsive efficiency. The leg has a wide chord to optimise rudder effect and improve course stability. Azipull – which is optimal for larger vessels that require high stability and manoeuvrability – is available with a controllable or fixed pitch propeller.
Oscar Kallerdahl holds a M.Sc. in Mechanical Engineering and Product Development. After many years in Rolls-Royce he has covered the full range of Rolls-Royce products and gained in-depth knowledge of the core processes that drive businesses – from Customer Relations, Sales and Contract Management, to Production, Delivery and Warranty Handling.
Sindre Holmelid Håberg started as a diesel mechanic, subsequently obtaining an engineering degree in Mechanical Engineering, specialising in reciprocating engines. Sindre’s wide-ranging knowledge enables him to provide customers with a full and complete understanding of all available options open to them, and their vessel.
Kim Espen Tepstad has spent all his working life with marine engines, starting out with nearly 5 years on the production line, assembling and testing them. After working closely with design and engineering teams for many years, this has given him a deep understanding of all aspects of engine design.
With our network of strategically located marine workshops spread across the globe, we can support our customers’ repair and overhaul needs wherever they are operating. Services are tailored to customer requirements, providing rapid turnarounds to meet docking schedules, while working to ISO quality standards.
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