Accuracy evaluation of the marine diesel engines harmonic excitation moments determination by means of the simplified indicator diagrams

Abstract

The article considers the calculated simplified indicator diagrams applicability to the forced torsional vibration calculation in power plants with diesels having systems for limiting the maximum combustion pressure. It is briefly described how and why the maximum combustion pressure is limited in modern marine diesels. The actual and simplified indicator diagrams are given, as well as the diagrams of torque from gas pressure forces for a modern low-speed two-stroke diesel engine. Harmonic analysis results for these diagrams are presented. The study results showed that simplified indicator diagrams using is unacceptable when calculating forced torsional vibration of systems with diesels having variable fuel injection angles. Also, performed work has shown the expediency of considering resonances from 12 to 24 orders when performing torsional vibration analysis for such power plants.