Effects of Fuel Quality on Two Strokes Slow Speed Diesel Engines

The correct management of the fuel supply involves commercial and technical implications as well as safety issues. The present paper deals with the possible malfunctions of two strokes (2T) slow speed Diesel engines and the wearing effects on cylinder liners caused by the fuel quality. The study is based on theory, data available in literature and on a test case. In particular heavy and residual fuels having worse properties with respect to the ones required by the engine manufacturer have been examined. The combustion process of these fuels has been examined in detail, aiming to find the parameters giving malfunctioning and wearing effects. The relationship between the characteristics of the fuel and wearing, damages and malfunctions are quite complex and it is not always possible to give clear and unique explanations. However, the present work sets an interpretation key of the phenomena. A sequence of the events, linked by cause-effect relationships, is proposed, which is able to explain how the fuel viscosity and some related parameters could wear the engine cylinder liners and cause malfunctions. Such general scheme is supported by some numerical simulations and applied to the case study. Some mathematical models relevant to single steps of the process available in literature have been applied and calibrated in order to obtain results in agreement with experimental data. Shortly, it can be said that combustion parameters, influenced also by fuel properties and causing wearing and malfunctions, are: increase of the mean diameter of droplets after fuel injection, increase of the gradient of the injection pressure, increase of the ignition delay, increase of the maximum combustion pressure, increase of the non-burnt fuel particles and ashes. The main consequences are the increase of the wearing of liners, exhaust valves and in general of the whole exhaust turbo-charger piping.