Revolutionary propulsion system for Super Eco-Ship

With increasing emphasis on environmental issues, the shipping industry is looking for propulsion solutions that will meet current and future regulations on emissions while bearing in mind that “for every good idea there is a cost”. Under the Kyoto Protocol 2002, there is a requirement to reduce greenhouse emissions 6% below 1990 levels for the first commitment period of 2008-2012. One way of achieving this target is to switch the transportation of goods from roads to coastal shipping which produces only one fifth of CO2 emissions per kilometer generated by commercial trucks.

Critical to achieving even greater reductions in emissions is improvements in ship hull design, propulsors and propulsion engines.

Concentrating on these parameters, the National Maritime Research Institute of Japan (NMRIoJ) has been conducting research and development of a revolutionary coastal ship called ?Super Eco-Ship?.

Innovative gas turbine

A new hull design, in combination with gas turbines and a highly efficient electrical propulsion system featuring a contra-rotating podded propeller, has been under development since April 2001. It is expected to increase cargo capacity by 20%, reduce CO2 emissions per ton kilometer by approximately 25% and reduce NOx emissions by 90%. Further aims are to reduce onboard maintenance and reduce dramatically noise and vibration levels for an improved working environment.

The power source for the super eco-ship will consist of an electrical propulsion system based on the Super Marine Gas Turbine (SMGT). This separate project was started back in 1998 and aims to significantly reduce emissions of NOx and SOx.

Gas turbines have a number of advantages such as lighter weight and smaller volume in comparison with conventional diesel engines which allows for extra payload. Furthermore, a small and light engine free from the constraints of the propeller shaft gives greater freedom in the location of the engine room. However, the engine and gas fuel costs are higher than for diesel engines and the NMRoJ took the decision to develop a revolutionary gas turbine engine with an efficiency comparable to that of the high-speed diesel.

This has seen a major effort by Japan in trying to reduce emissions from ships by developing a thermally efficient (38-40%), low NOx (less than 1g/kWh) turbine that is competitive with diesel engines in terms of cost. To this end, the engine is designed to burn A-type heavy fuel oil.

The SMGT has been under development by the Super Marine Gas Turbine Technological Research Association, comprising Kawasaki Heavy Industries, Ishikawajima Harima Heavy Industries, Daihatsu Diesel Manufacturing and Yanmar Diesel Engine. Extensive tests have been carried out such as the performance of coatings, including ceramics to prevent corrosion caused by burnt gas.

CRP podded propulsors

The electric power generated will drive an azimuthing podded propulsor fitted with contra-rotating propellers enabling the ship to achieve good manoeuvrability especially at low speeds and berthing operations as well as improved efficiency in terms of better fuel economy and propulsion efficiency. Also, the flexibility offered by the SMGT and podded propulsors will allow

the hull form to be optimised for maximum efficiency and give greater cargo capacity.

The contra-rotating propeller is a well proven concept and recent advances in technology have made it a practical solution and turned the concept into a sophisticated and efficient system. It is know that a mechanically driven slowly rotating propeller with a large diameter is quite effective in saving fuel. Because a 10% loss in power is inevitable for electric marine propulsion, it is necessary to overcome this handicap and the CRP podded propulsor is one answer.

A CRP driven by a tandem arrangement of small electric motors enables a compact and slim pod size to be used which brings better propulsive efficiency. A permanent magnet type motor has been developed to achieve a small diameter size with minimum heating. Double shafting for propeller drive, cooling of motor by sea water through the pod casing and water proof seals were essential elements in the design and full scale model tests were performed in 2003.

Design

The NMRIoJ used advanced design software including CFD to carry out parametic studies and optimisation of the hull form prior to tank tests. Computer simulation of ship navigation and control systems, and studies using real-time 3D graphics simulators enabled fine tuning of the detailed design including the Advanced Ship Safety Management system.

It is planned to build a prototype of the Super Eco-Ship in 2005, the final year of the project, for demonstration purposes. Once this low NOx vessel, designed to have reduced operating costs, dramatically reduced noise and vibration levels, and requiring no onboard maintenance, becomes available for commercial service, it is hoped it can revitalise coastal shipping in Japan and help a modal shift from trucking to waterborne transport, further reducing the burden on the environment.

Today?s Japanese coastal shipping has 40% share of the total domestic logistic volume and the plan is to increase this to 50%. The aim of the new generation of coastal shipping is to reduce logistic costs, improve safety and the efficiency of the service, and make the ships more environmentally friendly. n