Assessment of the diagnostic suitability of net thermal efficiency of marine diesel engine

This article applies to searching for symptoms and diagnostic parameters pointing in a deterioration in the quality of the combustion process in marine diesel engines. It was assumed that diagnostic parameters should give clear information regardless of engine load or with respect to the mean indicated pressure. The proposed cycle and sectional net thermal (heat) efficiency characteristics and also dimensionless net heat release rate were analysed. In order to obtain the state of deterioration of the injection process simulation of discalibration (larger diameter) of injector holes was performed. The simulation was carried out by the enlarged of diameter of the injector holes form 0.375 mm to 0.385 mm. Deterioration of the formation and growth of fuel spray droplet diameter is result of such simulation. The study was conducted on a laboratory engine Sulzer Al25/30. The study was carried out according to active experiment plan, during which the selected engine failure of the injection system was simulated. Measurements of pressure of combustion were performed by means of tensometric sensors of Spice Company on the indicator valve. The analysis found that in the event of injector nozzle faults (discalibrated holes) significantly decreases the net thermal efficiency η c cycle, and there are significant oscillations of net