Project Leader:	Professor Dr-Ing Horst Rulfs
Research Assistant:	Dipl-Ing L Marquardt
Duration:	01.01.2002 - 30.06.2002

 

Heavy fuel oil engines in ships or power plants are characterised by high reliability and reduced specific fuel consumption. Future international and national legislations will reduce pollutant emissions from the main or the auxilliary ship engines further, however, so that a minimisation of pollutant formation without a consumption penalty will become the key to further developments.

In the present study the potential for reducing NOx emissions through in-motor interventions was investigated theoretically for a medium-speed four-stroke engine (D = 320 mm, n = 750 min^-1, p_me = 26 bar) without adding inert material for cylinder loading. The simulation results have shown that in this manner and under gas oil operation it is possible to achieve a reduction in specific NOx emissions of ca. 6 g/kWh (test cycle E2).

Besides a consistent utilisation of the Miller process, for cooling the intake (intake stop was at 30 ° before TDC) it was necessary to reduce vale overlap and increase the compression ratio to 17.5. This demands a compression ratio of 6.3 in the charging compressor, operating with an overall charging efficiency of 70 %, and thus necessitates the utilisation of a two-stage charging with an intercooler. The study has taken into consideration the special characteristics of heavy fuel operation (limitations in the temperatures for the exhaust and the components) as well as the maximum cylinder pressures allowable.

This preliminary study has resulted in a final report to the FVV to serve as basis for designing a subsequent experimental investigation.