Deposit quantification in diesel engines using thermodynamic processes

Combustion chamber deposits have been for a long time an important problem for diesel engines. Even though they have been intensively researched, studies on their effects continue to this day.; In this work different approaches were investigated to establish a possible relationship between the thermodynamic processes and the deposit accumulation in an engine. Both the polytropic exponent and the heat release rate were analyzed in order to investigate deposit formation.; A one cylinder Ricardo Hydra diesel engine was used to investigate the deposit accumulation tendencies as a function of the operating condition chosen. Coking and decoking sequences, where deposits accumulate and decrease respectively, were used to vary the deposit level in the engine. The accumulation of deposit was monitored using a sample probe, which was inserted into the pressure port of the combustion chamber. The thermodynamic processes were monitored, using the cylinder pressure signal, as a function of the deposit presence in the combustion chamber. Only the first hours of the deposit formation process were used for the analysis in this work since the deposit formation equilibrium is reached only after a period of approximately 75 hours.; The experimental results obtained showed that the deposit presence influenced the thermodynamic processes of the engine. A linear relationship was established between the deposit accumulation and the polytropic exponent. The deposit accumulation variation was also reflected in the heat release rate diagrams as a function of time.; As the engine was being coked, the polytropic exponent value increased and the peaks of the heat release rate curves decreased. On the other hand, when the engine was being decoked, the exponent value decreased and the peaks of the curves increased.; Therefore, a correlation exists between the variation of the deposit accumulation and the thermodynamic processes and permits better monitoring of the engine.