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J. Konrad, T. Lauer, M. Moser, E. Lockner, Z. Zhu:
"Investigation of the cylinder cut-out for medium-speed dual-fuel engines";
Vortrag: 12th International MTZ Conference on Heavy-Duty Engines, Augsburg | Germany (eingeladen); 28.11.2017 - 29.11.2017; in: "ATZ live: Heavy-Duty- On- and Off-Highway-Engines", (2017), Paper-Nr. 18, 16 S.

As one of the consequences of the climate change, more severe maritime emission regulations are globally in force or will become applicable during the next years. The tough competition put pressure on the maritime transport industry. Therefore, their demand for efficient and mostly environmental neutral propulsion systems - to meet the environmental legislations and reduce the cargo costs - is high.
Medium-speed dual fuel engines are normally optimized for operation at high loads. Consequently, the highest efficiency and the most economic operation are achieved in this load range. This paper addresses the problem of improving the engine efficiency and additionally reducing the NO and methane emissions by static cylinder cut-out in low and part load operation.
A predictive 1D thermodynamical and fluid mechanical working cycle model of a MAN DF large engine was build up in GT Power. The included combustion and NO models predict crank angle depending burn rates and NO emissions. An optimization of the numerous model parameters is carried out with a search in a multi-parameter space using the commercial optimizer Optimus. A good correlation of the combustion rates and NO emissions with measured data is achieved.
The so called electronic cylinder cut-out is carried out by the constant deactivation of the natural gas admission of one to three cylinders in parallel. The load range, where the cylinder deactivation can be applied is restricted and depends on the capability of the charging system. The simulation model predicts a general increase of brake efficiency and a decrease of NO emissions as well as methane slip with cylinder cut-out.
The efficiency increase depends on the increased turbocharger efficiency, reduced pumping work, less friction loss, reduced wall heat loss, richer combustion, and the increased fraction of burned fuel. Thus, an improved combustion and engine efficiency are achieved. The methane slip can be reduced due to an increased fraction of burned fuel. The decrease in NO emissions is mainly caused by the shift from partial diesel combustion towards a largely premixed combustion with lowered peak temperatures due to the reduced fraction of diesel pilot. These effects rise with the number of cylinders that are cut-out.