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).