Mariko Kuroda

Development of a Calculation Method for Fuel Consumption of Ships in Actual Seas With Performance Evaluation

Greenhouse gas shall be reduced from shipping sector. For that purpose the regulation of EEDI (energy efficiency design index for new ships) and SEEMP (ship energy efficiency management plan) have been entry into force from 2013. In order to improve the energy efficiency in ship operation it is necessary to predict the fuel consumption accurately.In actual seas the wave effect is the dominant component of the external forces. In particular it is well known the bow shape above water affects the added resistance in waves. To reflect the effect of the bow shape a method which takes into account the result of simplified tank tests is proposed here. Using the results of tank tests the effect of the bow shape above water can be evaluated with accuracy as well as with robustness.Regarding to the fuel consumption it should be evaluated by combining the ship hydrodynamic performance with the engine characteristics. Especially the operating limits of the main engine, such as the torque limit and the over load protection, are affected to the ship hydrodynamic performance. In rough weather condition the revolution of the main engine will be reduced to be below the operating limits of the engine. This causes the large decrease of ship speed. To prevent the increase of fuel consumption, a control system by Fuel Index as an index of fuel injection has been applied to some ships. The calculation method for the fuel consumption by using Fuel Index is presented.In this paper following contents are reported; 1) development of a calculation method for the added resistance due to waves combined with the simplified tank tests in short waves, 2) comparison of the calculation method with onboard measurement, 3) development of a calculation method for the fuel consumption considering the engine operating mode in actual seas and 4) comparison of the method with onboard measurement of a container ship.From these investigations the availability of the present method is confirmed.Copyright

Study on the bow shapes above the waterline in view of the powering and greenhouse gas emissions in actual seas

In the shipping industry, as well as in other industries, a reduction in the greenhouse gas emissions is expected to help to reduce global warming. Shipbuilding companies are now developing ship hull forms to reduce greenhouse gas emissions with an emphasis on the vessel performance in actual seas where winds and waves are part of this environment. In this paper the bow shapes above the waterline, which may affect the added resistance in waves, are focused upon since the ship motion and wave reflection at the bow contribute to the added resistance in waves that can be reduced by an improvement in the bow shapes above the waterline. The relationship between the bow shapes above the waterline and the added wave resistance is investigated through tank tests in waves with model ships with different bow shapes. From the results of the investigation, the influences of the bow shape on the powering and greenhouse gas emissions is evaluated.

Effect of Bolsters on Ship Propulsive Performance in Actual Seas

These days ship designers make efforts to improve the ship propulsive performance in actual seas. To reduce added resistance due to waves the bow shape above water is important factor. Some ships install the bolsters at the bow, however, it is thought that waves acting on the bolsters affect the propulsive performance in actual seas. Thus tank tests in waves using a model ship with two types of the bolsters and without bolsters were carried out and the influence of bolsters on the propulsive performance was examined. As a result, it is found that the increment of added resistance in waves is not so large since the bolster interfered with the waves reflected by the hull.

Development of a Ship Performance Simulator in Actual Seas

Greenhouse gas shall be reduced from shipping sector. For that purpose the regulation of EEDI (energy efficiency design index for new ships) and SEEMP (ship energy efficiency management plan) were entry into force from 2013. In order to improve energy efficiency of ships in service it is necessary to predict the fuel consumption in actual seas.In order to reduce GHG emission from ships, a Vessel Performance Simulator in Actual Seas has been developed. It simulates ship speed and fuel consumption at steady condition by using weather data and designated engine revolution. Physical models for hull, propeller, rudder and engine are used in the simulator. Especially steady wave forces, wind forces, drift forces, steering forces and engine/governor model are important factor for the estimation.The fuel consumption should be evaluated combined the ship hydrodynamic performance with the engine/governor characteristics. Considering the external forces by winds and waves, the operation point of the main engine is important for the estimation, since the torque limit and the other limit of the engine/governor are affected to the ship hydrodynamic performance. To prevent the increase of fuel consumption in service, the engine control system by the Fuel Index has been applied to present ships. In rough weather condition the revolution of the main engine is reduced to lower revolution by the Fuel Index limit. It causes the large decrease of ship speed but reduces the fuel consumption due to reduction of engine revolution.Using the simulator the navigation performance of a container ship, a RoRo vehicle carrier and a bulk carrier is simulated along the route.In this paper following contents are discussed; 1) evaluation of the physical model; steady wave forces, wind forces, drift forces, steering forces and engine/governor model, 2) simulation and validation of the physical model by tank tests and on-board measurements and 3) effectiveness of the ship performance simulator for GHG reduction.Copyright