The effect of the speed on the blow-by of an internal combustion engine

Internal Combustion Engines are the generators of energy for many transportation applications, but they still have an overall low efficiency due to mechanical and thermal losses. The combustion chamber is the core element of the engine and it ought to be perfectly sealed, however some of the gas leaks toward the crankcase due to imperfect sealing of the rings. This leakage is known as blow-by and affects efficiency, correct lubrication and emissions. The aim of this paper was to understand in a more detailed way, how the engine speed could affect the sealing efficiency of a ring-pack. The problem, referred to a turbo diesel engine, was formulated in terms of motion equations for the rings and gas equations for the inter-ring crevices and solved in ©Ricardo RINGPAK solver. The results were discussed and compared with the reference literature and show that inertia and inter-ring gas pressures drive the sealing behavior of the rings. The blow-by trend resulted to decrease with the engine speed and increase with the load, exception made for the idle condition where the values were totally different to the other cases and didn’t follow a trend. Nevertheless, these findings can already be taken into account for further studies or experimental investigations.