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Encyclopedia of Marine and Energy Technology

Low NOx combustion


Wärtsilä developed combustion process which reduces the NOx emission level in the diesel engine by up to 25-35% without compromising on thermal efficiency. Low NOx combustion is based on:

- An high compression ratio that therefore gives an higher combustion air temperature at the start of injection, which drastically reduces the ignition delay.

- A late start of injection (retarded injection) and shorter injection duration to place combustion at the optimal point of the cycle with respect to efficiency.

- Improved fuel atomization and matching of combustion space with fuel sprays to facilitate air and fuel mixing.

- An early inlet valve closing (Miller timing).

Further reduction of NOx is achievable by Direct Water Injection, CASS, Wärtsilä Wetpac Humidification and Selective Catalytic Reduction.