NIIGATA Power Systems Co., Ltd., (Niigata) has developed and started sales of the 2,000 kW class medium-speed dual fuel marine engine “AHX-DF” that meets International Maritime Organization (IMO) Tier III NOx regulations start applying from 2016. AHX-DF is a dual fuel engine that runs either on diesel fuel or natural gas, and NOx emissions are reduced by 75% from the current IMO Tier II compliant engines of Niigata. This leads to substantial reduction of environmental load complying with IMO Tier III NOx regulations.

Advantages of AHX-DF engine are as follows.
(1) Excellent acceleration response in gas operation mode
Speedy acceleration from startup to 100% load operation is a critical factor for the marine engine. It was understood that the gas engine is not as good as the diesel engine for load increase rate. The load increase rate of the AHX-DF in gas operation is substantially improved and comparable with the diesel engine.

(2) Switching between gas operation and diesel operation possible at any time from startup to 100% load operation
Conventional dual fuel engines switching between gas operation and diesel operation was only possible when the engine ran below 80% load. In the case of the AHX-DF, switching of operation mode is possible at even if 100% load, which allows continued safe ship operation by switching the operation mode in an emergency.

(3) Stable operation during rapid load increase in gas operation
It was understood that stable ship operation was difficult with a gas engine due to possible abnormal combustion during rapid load increases. Niigata applied the superior gas combustion technologies acquired through the development of gas engines for stationary power plants to the AHX-DF and successfully reduced abnormal combustion during rapid load increases.

(4) Allows selection of suitable operation mode depending on the sea area
The dual fuel feature of the AHX-DF allows flexible selection of operation mode: gas operation in IMO NOx emission control areas and diesel operation in other sea areas. This makes compliance with IMO Tier III NOx regulations without after-treatment devices.

　Niigata continues the development of marine engines that will reduce the impact on the environment and provides engines for safe and environmentally friendly ship operations.

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